| 1. |
- Asfaw, Habtom D., et al.
(författare)
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Boosting the thermal stability of emulsion–templated polymers via sulfonation : an efficient synthetic route to hierarchically porous carbon foams
- 2016
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Ingår i: ChemistrySelect. - : Wiley. - 2365-6549. ; 1:4, s. 784-792
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchically porous carbon foams with specific surface areas exceeding 600 m2 g−1 can be derived from polystyrene foams that are synthesized via water-in-oil emulsion templating. However, most styrene-based polymers lack strong crosslinks and are degraded to volatile products when heated above 400 oC. A common strategy employed to avert depolymerization is to introduce potential crosslinking sites such as sulfonic acids by sulfonating the polymers. This article unravels the thermal and chemical processes leading up to the conversion of sulfonated high internal phase emulsion polystyrenes (polyHIPEs) to sulfur containing carbon foams. During pyrolysis, the sulfonic acid groups (-SO3H) are transformed to sulfone (-C-SO2-C-) and then to thioether (-C−S-C-) crosslinks. These chemical transformations have been monitored using spectroscopic techniques: in situ IR, Raman, X-ray photoelectron and X-ray absorption near edge structure spectroscopy. Based on thermal analyses, the formation of thioether links is associated with increased thermal stability and thus a substantial decrease in volatilization of the polymers.
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| 2. |
- Asfaw, Habtom Desta
(författare)
-
Multifunctional Carbon Foams by Emulsion Templating : Synthesis, Microstructure, and 3D Li-ion Microbatteries
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbon foams are among the existing electrode designs proposed for use in 3D Li-ion microbatteries. For such electrodes to find applications in practical microbatteries, however, their void sizes, specific surface areas and pore volumes need be optimized. This thesis concerns the synthesis of highly porous carbon foams and their multifunctional applications in 3D microbatteries. The carbon foams are derived from polymers that are obtained by polymerizing high internal phase water-in-oil emulsions (HIPEs).In general, the carbonization of the sulfonated polymers yielded hierarchically porous structures with void sizes ranging from 2 to 35 µm and a BET specific surface area as high as 630 m2 g-1. Thermogravimetric and spectroscopic evidence indicated that the sulfonic acid groups, introduced during sulfonation, transformed above 250 oC to thioether (-C-S-) crosslinks which were responsible for the thermal stability and charring tendency of the polymer precursors. Depending on the preparation of the HIPEs, the specific surface areas and void-size distributions were observed to vary considerably. In addition, the pyrolysis temperature could also affect the microstructures, the degree of graphitization, and the surface chemistry of the carbon foams.Various potential applications were explored for the bespoke carbon foams. First, their use as freestanding active materials in 3D microbatteries was studied. The carbon foams obtained at 700 to 1500 oC suffered from significant irreversible capacity loss during the initial discharge. In an effort to alleviate this drawback, the pyrolysis temperature was raised to 2200 oC. The resulting carbon foams were observed to deliver high, stable areal capacities over several cycles. Secondly, the possibility of using these structures as 3D current collectors for various active materials was investigated in-depth. As a proof-of-concept demonstration, positive active materials like polyaniline and LiFePO4 were deposited on the 3D architectures by means of electrodeposition and sol-gel approach, respectively. In both cases, the composite electrodes exhibited reasonably high cyclability and rate performance at different current densities. The syntheses of niobium and molybdenum oxides and their potential application as electrodes in microbatteries were also studied. In such applications, the carbon foams served dual purposes as 3D scaffolds and as reducing reactants in the carbothermal reduction process. Finally, a facile method of coating carbon substrates with oxide nanosheets was developed. The approach involved the exfoliation of crystalline VO2 to prepare dispersions of hydrated V2O5, which were subsequently cast onto CNT paper to form oxide films of different thicknesses.
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| 3. |
- Asfaw, Habtom Desta, 1986-, et al.
(författare)
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Over-Stoichiometric NbO2 Nanoparticles for a High Energy and Power Density Lithium Microbattery
- 2017
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Ingår i: ChemNanoMat. - : Wiley. - 2199-692X. ; 3:9, s. 646-655
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Tidskriftsartikel (refereegranskat)abstract
- Effective utilization of active materials in microbatteries can be enhanced by rational design of the electrodes. There is an increasing trend of using 3D electrodes that are coated in nanosized active materials to boost both energy and power densities. This article focuses on the fabrication of 3D electrodes based on monolithic carbon foams coated in over-stoichiometric NbO2 nanoparticles. The electrodes exhibit remarkable energy and power densities at various current densities when tested in lithium microbatteries. An areal capacity of around 0.7mAhcm(-2) and energy density up to 45mWhcm(-3) have been achieved. More than half of the areal capacity can be accessed at a current density of about 11mAcm(-2), with the corresponding energy and power densities being 21mWhcm(-3) and 1349mWcm(-3). These values are comparable to those of microsupercapacitors containing carbon and MnO2 nanomaterials. Furthermore, the electrochemical reversibility improves progressively upon cycling along with substantial increase in the charge transfer kinetics of the electrode. Based on impedance analyses almost a fourfold decrease in the charge transfer resistance has been observed over 25 cycles. Such enhancement of the electronic properties of NbO2 can account for the high electrochemical rate performance of the 3D electrodes.
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| 4. |
- Asfaw, Habtom Desta, Dr. 1986-, et al.
(författare)
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Tailoring the Microstructure and Electrochemical Performance of 3D Microbattery Electrodes Based on Carbon Foams
- 2019
-
Ingår i: Energy Technology. - : Wiley. - 2194-4288 .- 2194-4296.
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional (3D) carbon electrodes with suitable microstructural features and stable electrochemical performance are required for practical applications in 3D lithium (Li)-ion batteries. Herein, the optimization of the microstructures and electrochemical performances of carbon electrodes derived from emulsion-templated polymer foams are dealt with. Exploiting the rheological properties of the emulsion precursors, carbon foams with variable void sizes and specific surface areas are obtained. Carbon foams with an average void size of around 3.8 mu m are produced, and improvements are observed both in the coulombic efficiency and the cyclability of the carbon foam electrodes synthesized at 2200 degrees C. A stable areal capacity of up to 1.22 mAh cm(-2) (108 mAh g(-1)) is achieved at a current density of 50 mu A cm(-2). In addition, the areal capacity remains almost unaltered, i.e., 1.03 mAh cm(-2) (91 mAh g(-1)), although the cycling current density increases to 500 mu A cm(-2) indicating that the materials are promising for power demanding applications.
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| 5. |
- Bengtsson, Katarina
(författare)
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Additive manufacturing methods and materials for electrokinetic systems
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fabrication of miniaturized devices is usually time-consuming, costly, and the materials commonly used limit the structures that are possible to create. The techniques most often used to make microsystems involve multiple steps, where each step takes considerable time, and if only a few systems are to be made, the price per device becomes excessive. This thesis describes how a simple syringebased 3D-printer, in combination with an appropriate choice of materials, can reduce the delay between design and prototype and simplify fabrication of microsystems. This thesis suggest two types of materials that we propose be used in combination with 3D-printing to further develop microsystems for biology and biochemistry.Analytical applications in biology and biochemistry often contain electrodes, such as in gel electrophoresis. Faradaic (electrochemical) reactions have to occur at the metal electrodes to allow electron-to-ion transduction through an electrolyte-based system to drive a current when a potential is applied to the electrodes in an electrolyte-based system. These electrochemical reactions at the electrodes, such as water electrolysis, are usually problematic when miniaturizing devices and analytical systems. An alternative to metal electrodes can be electrochemicallyactive conducting polymers, e.g. poly(3,4-ethylenedioxythiophene) (PEDOT), which can be used to reduce electrolysis when driving a current through water-based systems. Paper 1 describes gel electrophoresis where the platinum electrodes were replaced with the conductive polymer PEDOT, without affecting the separation.Manufacturing and prototyping of microsystems can be simplified by using 3Dprinting in combination with a sacrificial material. A sacrificial template material can further simplify bottom-up manufacturing of more complicated forms such as protruding and overhanging structures. We showed in paper 2 that polyethylene glycol (PEG), in combination with a carbonate-based plasticizer, functions well as a 3D-printable sacrificial template material. PEG2000 with between 20 wt% and 30 wt% ethylene carbonate or propylene carbonate has properties advantageous for 3D-printing, such as shear-thinning rheology, mechanical and chemical stability, and easy dissolution in water.
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| 6. |
- Böhme, Solveig, et al.
(författare)
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Electrochemical behavior of tin(IV) oxide electrodes in lithium-ion batteries at high potentials
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In commercial lithium-ion batteries (LIB) graphite is used as the anode material. However, graphite has a rather limited volumetric and gravimetric capacity which is a drawback when higher energy densities are required as for instance in cars. Here, other materials with higher capacities and energy densities like the alloying materials tin and silicon are hence needed. Even bigger capacities could be obtained using tin oxide based compounds due to a combination of the tin oxide conversion reaction with lithium to tin and lithium oxide and the alloying reaction between tin and lithium. However, tin oxides usually suffer a great capacity loss after the first cycle due to the irreversibility of tin oxide reduction with lithium. [1,2] Nevertheless, there have been some reports in the past about a limited reversibility of the tin(IV) oxide conversion. [3-5]In our work we, therefore, investigated voltammetric cycling of tin(IV) oxide electrodes in different potential windows in order to learn about the influence of the alloying reaction on the conversion reaction (excluding the alloying reaction when cutting at 0.9 V vs. Li+/Li). In addition, rather high voltages (up to 3.7 V vs. Li+/Li) were applied to check the tin(IV) oxide conversion reversibility and electrode stability. Further cycling experiments were carried out at 60 oC and the results compared to cycling at room temperature. Cycling products at different potentials and temperatures were investigated using XPS. The results confirmed a certain reversibility of the tin(IV) oxide conversion which seemed to be enhanced at 60 oC. Cycling at a higher temperature generally lead to bigger capacities of the tin(IV) oxide electrodes. Courtney, I.A. and Dahn, J.R., J. Electrochem. Soc., 1997, 144, 2045-2052.Courtney, I.A.; McKinnon, W.R. and Dahn, J.R., J. Electrochem. Soc., 1999, 146, 59-68.Chouvin, J.; Branci, C.; Sarradin, J.; Olivier-Fourcade, J.; Jumas, J.C.; Simon, B. and Biensan, P., J. Power Sources, 1999, 81-82, 277-281.Chouvin, J.; Olivier-Fourcade, J.; Jumas, J.C.; Simon, B.; Biensan, P.; Fernández Madrigal, F.J.; Tirado, J.L. and Pérez Vicente, C., J. Electroanal. Chem., 2000, 494, 136-146.Sun, X.; Liu, J. and Li, Y., Chem. Mater., 2006, 18, 3486-3494.
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| 7. |
- Böhme, Solveig, et al.
(författare)
-
Electrochemical behaviour of tin(IV) oxide electrodes in lithium-ion batteries at high potentials
- 2015
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In commercial lithium-ion batteries graphite is currently the most common anode material. However, graphite has a rather limited volumetric and gravimetric capacity which is a drawback when higher energy densities are required, for instance, in cars. Here, other materials with higher capacities and energy densities like the alloying materials tin and silicon are, hence, required. Even bigger capacities could be obtained using tin oxide based compounds due to a combination of the tin oxide conversion reaction converting lithium to tin and lithium oxide and the alloying reaction between tin and lithium. However, tin oxides usually suffer a great capacity loss after the first cycle due to the irreversibility of the tin oxide reduction. [1,2] Nevertheless, there have been some reports suggesting a limited reversibility of the tin(IV) oxide conversion. [3-6]In this work we have investigated the voltammetric behaviour of tin(IV) oxide electrodes within different potential windows in order to study the influence of the alloying reaction on the conversion reaction (excluding the alloying reaction by cycling to 0.9 V vs. Li+/Li). In addition, rather high voltages (up to 3.7 V vs. Li+/Li) were applied to check the tin(IV) oxide conversion reversibility as well as electrode and electrolyte stability under these conditions. The results were also compared with those presented in an earlier model study carried with our group. [6] Cycling experiments were likewise carried out at 60oC and these results will be compared to those obtained for cycling at room temperature. The products formed at different potentials and temperatures were investigated using XPS and SEM. The results confirmed the presence of a partial reversibility of the tin(IV) oxide conversion reaction which was enhanced at 60oC. It will be demonstrated that cycling at a higher temperature lead to larger capacities of tin(IV) oxide electrodes. In addition, the influence of different cycling rates on the capacity will be discussed. Courtney, I.A. and Dahn, J.R., J. Electrochem. Soc., 1997, 144, 2045-2052.Courtney, I.A.; McKinnon, W.R. and Dahn, J.R., J. Electrochem. Soc., 1999, 146, 59-68.Chouvin, J.; Branci, C.; Sarradin, J.; Olivier-Fourcade, J.; Jumas, J.C.; Simon, B. and Biensan, P., J. Power Sources, 1999, 81-82, 277-281.Chouvin, J.; Olivier-Fourcade, J.; Jumas, J.C.; Simon, B.; Biensan, P.; Fernández Madrigal, F.J.; Tirado, J.L. and Pérez Vicente, C., J. Electroanal. Chem., 2000, 494, 136-146.Sun, X.; Liu, J. and Li, Y., Chem. Mater., 2006, 18, 3486-3494Böhme, S.; Edström, K. and Nyholm, L., On the electrochemistry of tin oxide coated tin electrodes in lithium-ion batteries, Electrochim. Acta, 2015 (in press).
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| 8. |
- Böhme, Solveig, et al.
(författare)
-
Electrochemical behaviour of tin(IV) oxide electrodes in lithium-ion batteries at high temperature and potentials
- 2016
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In commercial lithium-ion batteries graphite is currently the most common anode material. However, graphite has a rather limited volumetric and gravimetric capacity which is a drawback when higher energy densities are required, for instance, in cars. Here, other materials with higher capacities and energy densities like the alloying materials tin and silicon are, hence, required. Even bigger capacities could be obtained using tin oxide based compounds due to a combination of the tin oxide conversion reaction converting lithium to tin and lithium oxide and the alloying reaction between tin and lithium. However, tin oxides usually suffer a great capacity loss after the first cycle due to the irreversibility of the tin oxide reduction.[1,2] Nevertheless, there have been some reports suggesting a limited reversibility of the tin oxide conversion. [3-6] In our work we have investigated the kinetic behaviour of different tin(IV) oxide based electrodes during electrochemical cycling in lithium-ion batteries for both the conversion and the alloying reaction. To be able to study the influence of the alloying reaction on the conversion reaction cycling was carried out within different potential windows (excluding the alloying reaction by cycling only to 0.9 V vs. Li+/Li). In addition, rather high voltages (up to 3.7 V vs. Li+/Li) were applied to check the tin(IV) oxide conversion reversibility as well as electrode and electrolyte stability under these conditions. The results were also compared with those presented in an earlier model study carried with our group. [6] Cycling experiments were likewise carried out at 60 oC as well as different scan rates and with different particle sizes and additives (i.e. aluminium oxide and diamond). The products formed at different potentials and temperatures for tin(IV) oxide electrodes were also investigated using XPS and SEM. The results confirmed the presence of a partial reversibility of the tin(IV) oxide conversion reaction which was enhanced at 60 oC. The study, thus, indicated that there is a kinetic limitation regarding the reoxidation of tin to tin oxide upon charge which can be overcome more easily when using higher temperatures or smaller particles. It will be demonstrated that cycling at a higher temperature, lower scan rate or with a smaller particle size leads to larger capacities of tin(IV) oxide electrodes. In addition, the influence of different additives on the capacity will be discussed. REFERENCESCourtney, I.A. and Dahn, J.R., J. Electrochem. Soc., 1997, 144, 2045-2052.Courtney, I.A.; McKinnon, W.R. and Dahn, J.R., J. Electrochem. Soc., 1999, 146, 59-68.Chouvin, J.; Branci, C.; Sarradin, J.; Olivier-Fourcade, J.; Jumas, J.C.; Simon, B. and Biensan, P., J. Power Sources, 1999, 81-82, 277-281.Chouvin, J.; Olivier-Fourcade, J.; Jumas, J.C.; Simon, B.; Biensan, P.; Fernández Madrigal, F.J.; Tirado, J.L. and Pérez Vicente, C., J. Electroanal. Chem., 2000, 494, 136-146.Sun, X.; Liu, J. and Li, Y., Chem. Mater., 2006, 18, 3486-3494Böhme, S.; Edström, K. and Nyholm, L., On the electrochemistry of tin oxide coated tin electrodes in lithium-ion batteries, Electrochim. Acta, 2015, 179, 482-494.
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| 9. |
- Böhme, Solveig, 1987-, et al.
(författare)
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Elevated Temperature Lithium-Ion Batteries Containing SnO2 Electrodes and LiTFSI-Pip14TFSI Ionic Liquid Electrolyte
- 2017
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:4, s. A701-A708
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Tidskriftsartikel (refereegranskat)abstract
- The performance of lithium-ion batteries (LIBs) comprising SnO2 electrodes and an ionic liquid (IL) based electrolyte, i.e., 0.5 MLiTFSI in Pip14TFSI, has been studied at room temperature (i.e., 22◦C) and 80◦C. While the high viscosity and low conductivity ofthe electrolyte resulted in high overpotentials and low capacities at room temperature, the SnO2 performance at 80◦C was found to beanalogous to that seen at room temperature using a standard LP40 electrolyte (i.e., 1MLiPF6 dissolved in 1:1 ethylene carbonate anddiethyl carbonate). Significant reduction of the IL was, however, found at 80◦C, which resulted in low coulombic efficiencies duringthe first 20 cycles, most likely due to a growing SEI layer and the formation of soluble IL reduction products. X-ray photoelectronspectroscopy studies of the cycled SnO2 electrodes indicated the presence of an at least 10 nm thick solid electrolyte interphase (SEI)layer composed of inorganic components such as lithium fluoride, sulfates, and nitrides as well as organic species containing C-H,C-F and C-N bonds.
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| 10. |
- Böhme, Solveig, 1987-
(författare)
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Fundamental Insights into the Electrochemistry of Tin Oxide in Lithium-Ion Batteries
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims to provide insight into the fundamental electrochemical processes taking place when cycling SnO2 in lithium-ion batteries (LIBs). Special attention was paid to the partial reversibility of the tin oxide conversion reaction and how to enhance its reversibility. Another main effort was to pinpoint which limitations play a role in tin based electrodes besides the well-known volume change effect in order to develop new strategies for their improvement. In this aspect, Li+ mass transport within the electrode particles and the large first cycle charge transfer resistance were studied. Li+ diffusion was proven to be an important issue regarding the electrochemical cycling of SnO2. It was also shown that it is the Li+ transport inside the SnO2 particles which represents the largest limitation. In addition, the overlap between the potential regions of the tin oxide conversion and the alloying reaction was investigated with photoelectron spectroscopy (PES) to better understand if and how the reactions influence each other`s reversibility.The fundamental insights described above were subsequently used to develop strategies for the improvement of the performance and the cycle life for SnO2 electrodes in LIBs. For instance, elevated temperature cycling at 60 oC was employed to alleviate the Li+ diffusion limitation effects and, thus, significantly improved capacities could be obtained. Furthermore, an ionic liquid electrolyte was tested as an alternative electrolyte to cycle at higher temperatures than 60 oC which is the thermal stability limit for the conventional LP40 electrolyte. In addition, cycled SnO2 nanoparticles were characterized with transmission electron microscopy (TEM) to determine the effects of long term high temperature cycling. Also, the effect of vinylene carbonate (VC) as an electrolyte additive on the cycling behavior of SnO2 nanoparticles was studied in an effort to improve the capacity retention. In this context, a recently introduced intermittent current interruption (ICI) technique was employed to measure and compare the development of internal cell resistances with and without VC additive.
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| 11. |
- Böhme, Solveig, et al.
(författare)
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Lithium-ion batteries based on SnO2 electrodes and a LiTFSI-Pip14TFSI ionic liquid electrolyte
- 2017
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 164:4, s. A701-A708
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of lithium-ion batteries (LIBs) comprising SnO2 electrodes and an ionic liquid (IL) based electrolyte, i.e., 0.5 M LiTFSI in Pip14TFSI, has been studied at room temperature (i.e., 22°C) and 80°C. While the high viscosity and low conductivity of the electrolyte resulted in high overpotentials and low capacities at room temperature, the SnO2 performance at 80°C was found to be analogous to that seen at room temperature using a standard LP40 electrolyte (i.e., 1 M LiPF6 dissolved in 1:1 ethylene carbonate and diethyl carbonate). Significant reduction of the IL was, however, found at 80°C, which resulted in low coulombic efficiencies during the first 20 cycles, most likely due to a growing SEI layer and the formation of soluble IL reduction products. X-ray photoelectron spectroscopy studies of the cycled SnO2 electrodes indicated the presence of an at least 10 nm thick solid electrolyte interphase (SEI) layer composed of inorganic components such as lithium fluoride, sulfates, and nitrides as well as organic species containing C-H, C-F and C-N bonds.
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| 12. |
- Böhme, Solveig, 1987-, et al.
(författare)
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On the electrochemistry of tin oxide coated tin electrodes in lithium-ion batteries
- 2015
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 179, s. 482-494
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Tidskriftsartikel (refereegranskat)abstract
- As tin based electrodes are of significant interest in the development of improved lithium-ion batteries it is important to understand the associated electrochemical reactions. In this work it is shown that the electrochemical behavior of SnO2 coated tin electrodes can be described based on the SnO2 and SnO conversion reactions, the lithium tin alloy formation and the oxidation of tin generating SnF2. The CV, XPS and SEM data, obtained for electrodeposited tin crystals on gold substrates, demonstrates that the capacity loss often observed for SnO2 is caused by the reformed SnO2 layer serving as a passivating layer protecting the remaining tin. Capacities corresponding up to about 80 % of the initial SnO2 capacity could, however, be obtained by cycling to 3.5 V vs. Li+/Li. It is also shown that the oxidation of the lithium tin alloy is hindered by the rate of the diffusion of lithium through a layer of tin with increasing thickness and that the irreversible oxidation of tin to SnF2 at potentials larger than 2.8 V vs. Li+/Li is due to the fact that SnF2 is formed below the SnO2 layer. This improved electrochemical understanding of the SnO2/Sn system should be valuable in the development of tin based electrodes for lithium-ion batteries.
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| 13. |
- Böhme, Solveig, 1987-, et al.
(författare)
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Overlapping and rate controlling electrochemical reactions for tin(IV) oxide electrodes in lithiu-ion batteries
- 2017
-
Ingår i: Journal of Electroanalytical Chemistry. - 0022-0728 .- 1873-2569. ; 797, s. 47-60
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Tidskriftsartikel (refereegranskat)abstract
- The results of this extensive electrochemical study of the electrochemical reactions of SnO2 electrodes in lithium-ion batteries demonstrate that the different reduction and oxidation reactions overlap significantly during the cycling and that the rates of the redox reactions are limited by the mass transport through the layers of oxidation or reduction products formed on the electrodes. The experiments, which were carried out in the absence and presence of the lithium alloy reactions, show that the capacity losses seen on the first cycles mainly can be explained by an incomplete oxidation of the lithium tin alloy and an incomplete reformation of SnO2. The latter can be explained by the formation of thin tin oxide layers (i.e., SnO and SnO2), protecting the remaining tin, as the oxidation current then becomes limited by the Li+ diffusion rate though these layers. The results, also show that the first cycle SnO2 reduction was incomplete for the about 20 μm thick electrodes containing 1 to 6 μm large SnO2 particles. This can be ascribed to the formation of a layer of tin and Li2O (protecting the remaining SnO2) during the reduction process. Although the regeneration of the SnO2 always was slower than the reduction of the SnO2, the results clearly show that the SnO2 conversion reaction is far from irreversible, particularly at low scan rates and increased temperatures. Electrochemical cycling at 60 °C hence gave rise to increased capacities, but also a faster capacity loss, compared to at room temperature. These new findings indicate that a full utilization of SnO2 based electrodes at a given cycling rate only can be reached with sufficiently small particles since the allowed particle size is given by the time available for the mass transport through the formed surface layers. The present results consequently provide important insights into the phenomena limiting the use of SnO2 electrodes in lithium-ion batteries.
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| 14. |
- Böhme, Solveig, 1987-, et al.
(författare)
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Photoelectron Spectroscopic Evidence for Overlapping Redox Reactions for SnO2 Electrodes in Lithium-Ion Batteries
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:9, s. 4924-4936
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Tidskriftsartikel (refereegranskat)abstract
- In-house and synchrotron-based photoelectron spectroscopy (XPSand HAXPES) evidence is presented for an overlap between the conversion andalloying reaction during the cycling of SnO2 electrodes in lithium-ion batteries(LIBs). This overlap resulted in an incomplete initial reduction of the SnO2 as wellas the inability to regenerate the reduced SnO2 on the subsequent oxidative scan.The XPS and HAXPES results clearly show that the SnO2 conversion reactionoverlaps with the formation of the lithium tin alloy and that the conversion reactiongives rise to the formation of a passivating Sn layer on the SnO2 particles. The latterlayer renders the conversion reaction incomplete and enables lithium tin alloy toform on the surface of the particles still containing a core of SnO2. The results alsoshow that the reoxidation of the lithium tin alloy is incomplete when the formationof tin oxide starts. It is proposed that the rates of the electrochemical reactions andhence the capacity of SnO2-based electrodes are limited by the lithium masstransport rate through the formed layers of the reduction and oxidations products.In addition, it is shown that a solid electrolyte interphase (SEI) layer is continuously formed at potentials lower than about 1.2 VLi+/Li during the first scan and that a part of the SEI dissolves on the subsequent oxidative scan. While the SEI was found tocontain both organic and inorganic species, the former were mainly located at the SEI surface while the inorganic species werefound deeper within the SEI. The results also indicate that the SEI dissolution process predominantly involves the organic SEIcomponents.
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| 15. |
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| 16. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Cellulose Separators With Integrated Carbon Nanotube Interlayers for Lithium-Sulfur Batteries : An Investigation into the Complex Interplay between Cell Components
- 2019
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 166:14, s. A3235-A3241
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Tidskriftsartikel (refereegranskat)abstract
- This work aims to address two major roadblocks in the development of lithium-sulfur (Li-S) batteries: the inefficient deposition of Li on the metallic Li electrode and the parasitic "polysulfide redox shuttle". These roadblocks are here approached, respectively, by the combination of a cellulose separator with a cathode-facing conductive porous carbon interlayer, based on their previously reported individual benefits. Both approaches result in significant improvements in cycle life in test cells with positive electrodes with practically relevant specifications. Despite the substantially prolonged cycle life, the combination of the interlayer and cellulose separator generates an increase in polysulfide shuttle current, leading to greatly reduced Coulombic efficiency. Based on XPS analyses, the latter is ascribed to a change in the composition of the solid electrolyte interphase (SEI) on the Li electrode. At the same time, the rate of electrolyte decomposition is found to be lower in cells with cellulose-based separators, which corroborates the observation of longer cycle life. These seemingly contradictory and counterintuitive observations demonstrate the complicated interactions between the cell components in the Li-S system and how strategies aiming to mitigate one unwanted process may exacerbate another. This study demonstrates the value of a holistic approach to the development of Li-S chemistry.
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| 17. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Electrochemical Analysis of Modified Separators for Li-S Batteries
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The lithium-sulfur system is one of the potential energy storage technologies of the next generation due to the high theoretical specific capacity (1672 mAh/g), abundance and nontoxicity of sulfur [1]. However, there are still challenges yet to be overcome, one of which is the ‘polysulfide shuttle’ [1]. In order to address this issue, several modifications of the separators have been proposed. For example, longer cycle life, higher Coulombic efficiency and higher specific capacities have been reported with metal oxide coatings [2] and conductive interlayers [3,4] on the separators. Performance improvements in one or more of these properties have been ascribed to a suppression of polysulfide transport across the separator, even though this has not always been correlated with the difference in electrochemistry. In this work, the Intermittent Current Interruption (ICI) method [5] is applied to monitor the evolution of internal resistance of Li-S cells with different separators during repeated charge and discharge. Cells with different separators exhibit significant differences in resistance as a function of state-of-charge in the initial cycles, as shown in the figure. Complemented by self-discharge tests and impedance spectroscopy at selected states of charge, the roles of the interlayers in the system can be further interpreted electrochemically. This work aims to associate the electrochemical properties of the interlayers to their corresponding microstructural counterparts, which can in turn facilitate further development of the interlayer materials. Figure: Internal resistance of cells vs specific charge for Li-S cells with different separators (Zero charge indicates the fully charged state.) for the 2nd, 5th and 10th cycles at C/10 rate. References:[1] S. Urbonaite, T. Poux, P. Novák, Adv. Energy Mater. 5 (2015) 1–20.[2] Z. Zhang, Y. Lai, Z. Zhang, K. Zhang, J. Li, Electrochim. Acta 129 (2014) 55–61.[3] H. Yao, K. Yan, W. Li, G. Zheng, D. Kong, Z.W. Seh, V.K. Narasimhan, Z. Liang, Y. Cui, Energy Environ. Sci. 7 (2014) 3381–3390.[4] J. Balach, T. Jaumann, M. Klose, S. Oswald, J. Eckert, L. Giebeler, Adv. Funct. Mater. 25 (2015) 5285–5291.[5] M.J. Lacey, K. Edström, D. Brandell, Chem. Commun. 51 (2015) 16502–16505.
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| 18. |
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| 19. |
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| 20. |
- Edberg, Jesper, 1988-
(författare)
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Flexible and Cellulose-based Organic Electronics
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic electronics is the study of organic materials with electronic functionality and the applications of such materials. In the 1970s, the discovery that polymers can be made electrically conductive led to an explosion within this field which has continued to grow year by year. One of the attractive features of organic electronic materials is their inherent mechanical flexibility, which has led to the development of numerous flexible electronics technologies such as organic light emitting diodes and solar cells on flexible substrates. The possibility to produce electronics on flexible substrates like plastic or paper has also had a large impact on the field of printed, electronics where inks with electronic functionality are used for large area fabrication of electronic devices using classical printing methods, such as screen printing, inkjet printing and flexography.Recently, there has been a growing interest in the use of cellulose in organic and printed electronics, not only as a paper substrate but also as a component in composite materials where the cellulose provides mechanical strength and favorable 3D-microstructures. Nanofibrillated cellulose is composed of cellulose fibers with high aspect-ratio and diameters in the nanometer range. Due to its remarkable mechanical strength, large area-to-volume ratio, optical transparency and solution processability it has been widely used as a scaffold or binder for electronically active materials in applications such as batteries, supercapacitors and optoelectronics.The focus of this thesis is on flexible devices based on conductive polymers and can be divided into two parts: (1) Composite materials of nanofibrillated cellulose and the conductive polymer PEDOT:PSS and (2) patterning of vapor phase polymerized conductive polymers. In the first part, it is demonstrated how the combination of cellulose and conductive polymers can be used to make electronic materials of various form factors and functionality. Thick, freestanding and flexible “papers” are used to realize electrochemical devices such as transistors and supercapacitors while lightweight, porous and elastic aerogels are used for sensor applications. The second focus of the thesis is on a novel method of patterning conductive polymers produced by vapor phase polymerization using UV-light. This method is used to realize flexible electrochromic smart windows with high-resolution images and tunable optical contrast.
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| 21. |
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| 22. |
- Eriksson, Kristofer, et al.
(författare)
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Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam : A Catalyst for Cycloisomerization of Alkynoic Acids to gamma-Alkylidene Lactones
- 2015
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :10, s. 2250-2255
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Tidskriftsartikel (refereegranskat)abstract
- A versatile approach for the production of dispersed thiol-stabilized gold nanoparticles in the pores of siliceous mesocellular foam (MCF) is described. The reported method is based on an electrochemical oxidation of a gold surface generating oxidative Au-III species, which give rise to a surface-confined redox reaction yielding MCF-supported Au-I thiolates. By reducing the corresponding Au-I-S-MCF species with sodium borohydride, thiol-stabilized gold nanoparticles in the size range of 1-8 nm were obtained as determined by transmission electron microscopy. Elemental analysis indicated an Au loading of 3% (w/w) on the MCF. The surface-confined Au nanoparticles were used to catalyze the cycloisomerization of alkynoic acids to the corresponding -alkylidene lactones in high efficiency and complete 5-exo-dig selectivity under mild reaction conditions.
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| 23. |
- Eriksson, Rickard
(författare)
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Structural Changes in Lithium Battery Materials Induced by Aging or Usage
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Li-ion batteries have a huge potential for use in electrification of the transportation sector. The major challenge to be met is the limited energy storage capacity of the battery pack: both the amount of energy which can be stored within the space available in the vehicle (defining its range), and the aging of the individual battery cells (determining how long a whole pack can deliver sufficient energy and power to drive the vehicle). This thesis aims to increase our knowledge and understanding of structural changes induced by aging and usage of the Li-ion battery materials involved.Aging processes have been studied in commercial-size Li-ion cells with two different chemistries. LiFePO4/graphite cells were aged under different conditions, and thereafter examined at different points along the electrodes by post mortem characterisation using SEM, XPS, XRD and electrochemical characterization in half-cells. The results revealed large differences in degradation behaviour under different aging conditions and in different regions of the same cell. The aging of LiMn2O4-LiCoO2/Li4Ti5O12 cells was studied under two different aging conditions. Post mortem analysis revealed a high degree of Mn/Co mixing within individual particles of the LiMn2O4-LiCoO2 composite electrode.Structural changes induced by lithium insertion were studied in two negative electrode materials: in Li0.5Ni0.25TiOPO4 using in situ XRD, and in Ni0.5TiOPO4 using EXAFS, XANES and HAXPES. It was shown that Li0.5Ni0.25TiOPO4 lost most of its long-range-order during lithiation, and that both Ni and Ti were involved in the charge compensation mechanism during lithiation/delithiation of Ni0.5TiOPO4, with small clusters of metal-like Ni forming during lithiation.Finally, in situ XRD studies were also made of the reaction pathways to form LiFeSO4F from two sets of reactants: either FeSO4·H2O and LiF, or Li2SO4 and FeF2. During the heat treatment, Li2SO4 and FeF2 react to form FeSO4·H2O and LiF in a first step. In a second step LiFeSO4F is formed. This underlines the importance of the structural similarities between LiFeSO4F and FeSO4·H2O in the formation process of LiFeSO4F.
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| 24. |
- Etman, Ahmed, et al.
(författare)
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One-pot Synthesis of MoO3-x Nanosheets for Supercapacitor Applications
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Molybdenum oxide nanosheets are interesting materials for energy storage, catalysis, and gas sensor applications.1 However, they are traditionally prepared via a variety of approaches which require the use of high temperature or organic solvents.2,3 Herein, we report the synthesis of MoO3-x nanosheets (where x denotes oxygen vacancy) via a one-step water based exfoliation strategy using bulk molybdenum oxides precursors.4 Scanning and transmission electron microscopy show that the MoO3-x has a typical nanosheet morphology with a few nanometer thickness. The MoO3-x nanosheets display localized surface plasmon resonance (LSPR), which can be enhanced by modifying the morphology and the amount of oxygen vacancies (x) using chemical and/or photochemical treatments.The aqueous suspension of the MoO3-x nanosheets was drop-cast onto carbon paper and this material was then used as binder free electrodes for supercapacitor applications. The electrodes showed promising performance regarding capacitance and rate capability in acidified sodium sulphate solutions. The facile green synthesis of MoO3-x nanosheets coupled with their significant photochemical and electrochemical properties pave the way for the use of the nanosheets in a variety of applications.References:(1) de Castro, I. A.; Datta, R. S.; Ou, J. Z.; Castellanos-Gomez, A.; Sriram, S.; Daeneke, T.; Kalantar-zadeh, K. Molybdenum Oxides - From Fundamentals to Functionality. Adv. Mater. 2017, 29 (40), 1701619.(2) Xiao, X.; Song, H.; Lin, S.; Zhou, Y.; Zhan, X.; Hu, Z.; Zhang, Q.; Sun, J.; Yang, B.; Li, T.; Jiao, L.; Zhou, J.; Tang, J.; Gogotsi, Y. Scalable Salt-Templated Synthesis of Two-Dimensional Transition Metal Oxides. Nat. Commun. 2016, 7, 11296.(3) Alsaif, M. M. Y. A.; Field, M. R.; Daeneke, T.; Chrimes, A. F.; Zhang, W.; Carey, B. J.; Berean, K. J.; Walia, S.; van Embden, J.; Zhang, B.; Latham, K.; Kalantar-zadeh, K.; Ou, J. Z. Exfoliation Solvent Dependent Plasmon Resonances in Two-Dimensional Sub-Stoichiometric Molybdenum Oxide Nanoflakes. ACS Appl. Mater. Interfaces 2016, 8 (5), 3482–3493.(4) Etman A. S.; Abdelhamid H. N.; Yuan Y.; Wang L.; Zou X.; Sun J. Facile Water Based Strategy for Synthesizing MoO3-x Nanosheets: Efficient Visible Light Photocatalyst for Dye Degradation. ACS Omega. in Press.
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| 25. |
- Etman, Ahmed S., et al.
(författare)
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Flexible Freestanding MoO3-x-Carbon Nanotubes-Nanocellulose Paper Electrodes for Charge-Storage Applications
- 2019
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Ingår i: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; 12:23, s. 5157-5163
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Tidskriftsartikel (refereegranskat)abstract
- Herein, a one‐step synthesis protocol was developed for synthesizing freestanding/flexible paper electrodes composed of nanostructured molybdenum oxide (MoO3−x) embedded in a carbon nanotube (CNT) and Cladophora cellulose (CC) matrix. The preparation method involved sonication of the precursors, nanostructured MoO3−x, CNTs, and CC with weight ratios of 7:2:1, in a water/ethanol mixture, followed by vacuum filtration. The electrodes were straightforward to handle and possessed a thickness of approximately 12 μm and a mass loading of MoO3−x–CNTs of approximately 0.9 mg cm−2. The elemental mapping showed that the nanostructured MoO3−x was uniformly embedded inside the CNTs–CC matrix. The MoO3−x–CNTs–CC paper electrodes featured a capacity of 30 C g−1, normalized to the mass of MoO3−x–CNTs, at a current density of 78 A g−1 (corresponding to a rate of approximately 210 C based on the MoO3 content, assuming a theoretical capacity of 1339 C g−1), and exhibited a capacity retention of 91 % over 30 000 cycles. This study paves the way for the manufacturing of flexible/freestanding nanostructured MoO3−x‐based electrodes for use in charge‐storage devices at high charge/discharge rates.
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| 26. |
- Etman, Ahmed S., et al.
(författare)
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Molybdenum Oxide Nanosheets with Tunable Plasmonic Resonance : Aqueous Exfoliation Synthesis and Charge Storage Applications
- 2019
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 29:4
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Tidskriftsartikel (refereegranskat)abstract
- Herein, a simple aqueous‐exfoliation strategy is introduced for the fabrication of a series of MoO3−x nanosheets (where x stands for oxygen vacancies) using two commercial molybdenum oxide precursors, MoO2 and MoO3. The nanosheets offer a localized surface plasmon resonance (LSPR) effect which is dependent on the structure and local environment of the nanosheets. The LSPR can be efficiently tuned by changing the weight ratio between the molybdenum oxide precursor(s) and/or by solar light irradiation using a low‐energy UV lamp (36 W). For the pristine MoO3−x nanosheets, the highest LSPR signal is obtained for nanosheets prepared using 80% MoO2. On the contrary, after solar light irradiation, the nanosheets prepared using pure MoO3 offer the highest LSPR response. The nanosheets also show an outstanding rate capability when used as binder‐free supercapacitor electrodes in an acidified Na2SO4 electrolyte. The electrodes exhibit discharge capacities of 110 and 75 C g−1 at a scan rate of 20 and 1000 mV s−1, respectively. The MoO3−x nanosheets can likewise be used as a negative electrode material for lithium‐ion batteries. The efficient eco‐friendly synthesis and the ability to tune the photochemical and electrochemical properties of the nanosheets make this approach interesting to many energy‐related research fields.
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| 27. |
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| 28. |
- Ihrfors, Charlotte, et al.
(författare)
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Manufacturing and electrochemical characterization of freestanding TiO2 nanotube electrodes for lithium-ion batteries
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Microelectronic systems are continuously developed towards smaller and smaller devices which increase the demands on the energy and power densities of the batteries that are used to power the devices. As the size of the electronic components decreases the foot print area available for the surface mounted batteries becomes a limiting factor. These high demands on the energy and power densities make three-dimensional (3D) lithium-ion microbatteries a promising alternative while traditional thin film lithium-ion batteries are less suitable [1, 2] as it is difficult to obtain both high energy and power densities for this type of batteries. The 3D microbatteries can, on the other hand, provide high energy densities per footprint area as well as high power densities thanks to the short diffusion paths and increased mass loading when compared to thin film batteries [1, 3, 4].It is well-known that self-assembled freestanding TiO2 nanotubes with a hexagonal structure can be synthesized through an anodization of titanium foil in a fluoride containing electrolyte [5]. This 3D structure can then be annealed to convert the as-formed amorphous TiO2 to anatase. Such annealed nanotubes can readily be used as binder-free anode material for lithium-ion batteries. The high capacity per footprint area and good cycling stability of the TiO2 nanotubes make them suitable for applications in 3D microbatteries [3].In this work TiO2 nanotubes of different lengths from 4.5 to 40 µm have been synthesized through a two-step anodization process. The material properties of the nanotubes have been analysed with scanning electron microscopy and X-ray diffraction and the electrochemical performances of nanotubes of different lengths have been evaluated, using galvanostatic cycling and cyclic voltammetry in cells containing lithium-foil counter electrodes. The rate limiting factors during the lithiation and delithiation at high cycling rates have been studied for different tube lengths in addition to the cycling stability of nanotubes with different lengths. ReferencesRoberts M., Johns P., Owen J., Brandell D., Edström K., Enany G. E., Guery C., Golodonitsky D., Lacey M., Lecoeur C., Mazor H., Peled E., Perre E., Shaijumon M. M., Simon P., Taberna P. -L., 3D lithium ion batteries—from fundamentals to fabrication. J. Mater. Chem. 2011, 21, 9876–9890.Edström K., Brandell D., Gustafsson T., Nyholm L., Electrodeposition as a tool for 3D microbattery fabrication. Electrochem. Soc. Interface. 2011, 20, 41–46.Wei W., Oltean G., Tai C. –W., Edström K., Björefors F., Nyholm L., High energy and power density TiO2 nanotube electrodes for 3D Li-ion microbatteries. J. Mater. Chem. A. 2013, 1, 8160-8169.Yiping T., Xiaoxu T., Guangya H., Guoqu Z., Nanocrystalline Li4Ti5O12-coated TiO2 nanotube arrays as three-dimensional anodes for lithium-ion batteries. Electrochimica Acta. 2014, 117, 172–178.Roy P., Berger S., Schmuki P., TiO2 Nanotubes: Synthesis and Applications. Angew. Chem. Int. Ed. 2011, 50, 2904–2939.
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| 29. |
- Ihrfors, Charlotte, et al.
(författare)
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Manufacturing of TiO2 nanotubes for lithium-ion batteries
- 2015
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Microelectronic equipment is continuously getting smaller and smaller and thus sets higher and higher demands on the energy and power densities of the batteries that are used to drive them. For surface mounted batteries the surface area of the battery becomes more and more important as the size of the electronic components decreases. The high demands on the energy and power densities per footprint area render the traditional thin film lithium-ion batteries unsuitable and 3D microbatteries are instead proposed to meet these new demands [1, 2]. The high surface area, short diffusion paths and increased mass loadings compared to for thin film batteries makes it possible for the 3D microbatteries to provide a higher energy density per footprint area as well as a high power density [1, 3, 4].Electrochemical anodization of titanium foil in fluoride containing electrolytes makes it possible to grow self-assembled TiO2 nanotubes with an almost perfect hexagonal structure. This 3D structure has been shown to perform well as a binder free anode material for lithium-ion batteries and the nanotubes are usually annealed to convert the as-formed TiO2 to anatase. The TiO2 nanotubes have shown a high capacity per footprint area and a good cycling stability which makes them suitable for applications in 3D microbatteries [3].In the work presented here TiO2 nanotubes of different lengths, i.e. from 4.5 to 40 µm, have been synthesized employing an anodization approach. The obtained nanotubes, which were characterized with scanning electron microscopy and X-ray diffraction experiments, were also evaluated as electrodes in lithium-ion batteries containing lithium foil counter electrodes. The results of these investigations will be discussed. References Roberts M, Johns P, Owen J, Brandell D, Edstrom K, Enany GE, Guery C, Golodonitsky D, Lacey M, Lecoeur C, Mazor H, Peled E, Perre E, Shaijumon MM, Simon P, Taberna P-L. 3D lithium ion batteries—from fundamentals to fabrication. J. Mater. Chem. 2011;21:9876–90.Edström K, Brandell D, Gustafsson T, Nyholm L. Electrodeposition as a tool for 3D microbattery fabrication. Electrochem. Soc. Interface. 2011;20:41–6.Wei W, Oltean G, Tai C-W, Edström K, Björefors F, Nyholm L. High energy and power density TiO2 nanotube electrodes for 3D Li-ion microbatteries. J. Mater. Chem. A. 2013;1:8160-9.Yiping T, Xiaoxu T, Guangya H, Guoqu Z. Nanocrystalline Li4Ti5O12-coated TiO2 nanotube arrays as three-dimensional anode for lithium-ion batteries. Electrochimica Acta. 2014;117:172–8.Roy P, Berger S, Schmuki P. TiO2 Nanotubes: Synthesis and Applications. Angew. Chem. Int. Ed. 2011;50:2904–39.
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| 30. |
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| 31. |
- Keskinen, Jari, et al.
(författare)
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Asymmetric and symmetric supercapacitors based on polypyrrole and activated carbon electrodes
- 2015
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 203, s. 192-199
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Supercapacitors were prepared using either two polypyrrole (PPy) composite electrodes or one PPy composite and one activated carbon electrode. The PPy composite electrodes were either freestanding paper-like sheets or PPy films printed on graphite ink coated aluminium/PET laminate substrates, using Cladophora algae derived cellulose as the substrate or binder, respectively. The specific capacitance of the PPy electrodes was found to be about 200 F g−1 depending on the manufacturing method, yielding supercapacitors with capacitances between 0.45 and 3.8 F and energy efficiencies of over 90%. For an asymmetric device with activated carbon positive electrode and PPy negative electrode a capacitance loss of 5% was seen after 14300 cycles.
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| 32. |
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| 33. |
- Kizling, Michal, et al.
(författare)
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Bioelectrodes based on pseudocapacitive cellulose/polypyrrole composite improve performance of biofuel cell
- 2016
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 112, s. 184-190
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Tidskriftsartikel (refereegranskat)abstract
- Enzymatic electrodes with high internal capacitance, based on cellulose/polypyrrole composite were optimized and utilized to design improved enzymatic fuel cell. Fructose dehydrogenase Gluconobacter sp. specifically adsorbed on the cellulose/polypyrrole matrix and electrophoretically immobilized and electrochemically entrapped Laccase Trametes versicolor, were used as the anode and cathode bioelectrocatalysts, respectively. The cellulose/polypyrrole composite film exhibited pseudocapacitive properties under mild pH conditions. Following modification with carboxylic groups the composite material enabled highly efficient adsorption of enzyme and provided good electrical contact between the enzymatic active sites and the electrode surface. The modified cellulose/polypyrrole composite based electrode was used for the anode leading to mediatorless fructose oxidation giving large catalytic current density, 12.8 mA cm(-2). Laccase and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) as the mediator entrapped in the cellulose/polypyrrole composite film generated dioxygen reduction current density of 2 mA cm(-2). Application of pseudocapacitive matrix and decreasing the distance between electrodes to 1 mm lead to improvement of the biofuel cell power output and its regeneration ability. The power of the cell was found to increase by introduction of a preconditioning step during which the cell was kept at open circuit voltage under fuel flow. After 24 h of preconditioning the matrix was recharged and the device output reached the power, 2.1 mW cm(-2) and OCV, 0.59 V.
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| 34. |
- Kizling, Michal, et al.
(författare)
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Biosupercapacitors for powering oxygen sensing devices
- 2015
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 106, s. 34-40
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Tidskriftsartikel (refereegranskat)abstract
- A biofuel cell comprising electrodes based on supercapacitive materials - carbon nanotubes and nanocellulose/polypyrrole composite was utilized to power an oxygen biosensor. Laccase Trametes versicolor, immobilized on naphthylated multi walled carbon nanotubes, and fructose dehydrogenase, adsorbed on a porous polypyrrole matrix, were used as the cathode and anode bioelectrocatalysts, respectively. The nanomaterials employed as the supports for the enzymes increased the surface area of the electrodes and provide direct contact with the active sites of the enzymes. The anode modified with the conducting polymer layer exhibited significant pseudocapacitive properties providing superior performance also in the high energy mode, e.g., when switching on/off the powered device. Three air-fructose biofuel cells connected in a series converted chemical energy into electrical giving 2 mW power and open circuit potential of 2 V. The biofuel cell system was tested under various externally applied resistances and used as a powering unit for a laboratory designed two-electrode minipotentiostat and a laccase based sensor for oxygen sensing. Best results in terms of long time measurement of oxygen levels were obtained in the pulse mode -45 s for measurement and 15 min for self-recharging of the powering unit.
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| 35. |
- Kizling, Michal, et al.
(författare)
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Pseudocapacitive polypyrrole-nanocellulose composite for sugar-air enzymatic fuel cells
- 2015
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Ingår i: Electrochemistry communications. - : Elsevier BV. - 1388-2481 .- 1873-1902. ; 50, s. 55-59
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Tidskriftsartikel (refereegranskat)abstract
- Efficient, new combination of a bioelectrocatalytic and a pseudocapacitive cellulose-based composite material is reported. The anode comprising Gluconobacter sp. fructose dehydrogenase physically adsorbed on Cladophora sp. Algae nanocellulose/polypyrrole composite provides large catalytic oxidation currents due to large effective surface area of the composite material, and enables storing of the charge. Supercapacitor properties are useful for larger current demands e.g. during switching on-off the devices. Mediatorless catalytic oxidation current densities as high as 14 mA cm(-2) at potentials as negative as -0.17 V vs. Ag/AgCl constitute the best anode performance without using mediators reported to date. The fuel cell with GCE cathode covered with laccase adsorbed on naphthylated multiwalled carbon nanotubes, exhibits improved parameters: open circuit voltage of 0.76 V, and maximum power density 1.6 mW cm(-2).
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| 36. |
- Lindgren, Fredrik, et al.
(författare)
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Breaking Down a Complex System : Interpreting PES Peak Positions for Cycled Li-ion Battery Electrodes
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121, s. 27303-27312
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Tidskriftsartikel (refereegranskat)abstract
- Photoelectron spectroscopy (PES) is an important technique for tracing and understanding the side reactions responsible for decreasing performance of Li-ion batteries. Interpretation of different spectral components is dependent on correct binding energy referencing and for battery electrodes this is highly complex. In this work, we investigate the effect on binding energy reference points in PES in correlation to solid electrolyte interphase (SEI) formation, changing electrode potentials and state of charge variations in Li-ion battery electrodes. The results show that components in the SEI have a significantly different binding energy reference point relative to the bulk electrode material (i.e. up to 2 eV). It is also shown that electrode components with electronically insulating/semi-conducting nature are shifted as a function of electrode potential relative to highly conducting materials. Further, spectral changes due to lithiation are highly depending on the nature of the active material and its lithiation mechanism. Finally, a strategy for planning and evaluating PES experiments on battery electrodes is proposed where some materials require careful choice of one or more internal reference points while others may be treated essentially without internal calibration.
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| 37. |
- Lindgren, Fredrik, et al.
(författare)
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On the Capacity Losses Seen for Optimized Nano-Si Composite Electrodes in Li-Metal Half-Cells
- 2019
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 9:33
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Tidskriftsartikel (refereegranskat)abstract
- While the use of silicon‐based electrodes can increase the capacity of Li‐ion batteries considerably, their application is associated with significant capacity losses. In this work, the influences of solid electrolyte interphase (SEI) formation, volume expansion, and lithium trapping are evaluated for two different electrochemical cycling schemes using lithium‐metal half‐cells containing silicon nanoparticle–based composite electrodes. Lithium trapping, caused by incomplete delithiation, is demonstrated to be the main reason for the capacity loss while SEI formation and dissolution affect the accumulated capacity loss due to a decreased coulombic efficiency. The capacity losses can be explained by the increasing lithium concentration in the electrode causing a decreasing lithiation potential and the lithiation cut‐off limit being reached faster. A lithium‐to‐silicon atomic ratio of 3.28 is found for a silicon electrode after 650 cycles using 1200 mAhg−1 capacity limited cycling. The results further show that the lithiation step is the capacity‐limiting step and that the capacity losses can be minimized by increasing the efficiency of the delithiation step via the inclusion of constant voltage delithiation steps. Lithium trapping due to incomplete delithiation consequently constitutes a very important capacity loss phenomenon for silicon composite electrodes.
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| 38. |
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| 39. |
- Makaraviciute, Asta, et al.
(författare)
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Systematic approach to the development of microfabricated biosensors : relationship between the gold surface pretreatment and thiolated molecule binding
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:31, s. 26610-26621
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Tidskriftsartikel (refereegranskat)abstract
- Despite the increasing popularity of microfabricated biosensors due to advances in technologic and surface functionalization strategies, their successful implementation is partially inhibited by the lack of consistency in their analytical characteristics. One of the main causes for the discrepancies is the absence of a systematic and comprehensive approach to surface functionalization. In this article microfabricated gold electrodes aimed at biosensor development have been systematically characterized in terms of surface pretreatment, thiolated molecule binding, and reproducibility by means of X-ray photoelectron scattering (XPS) and cyclic voltammetry (CV). It has been shown that after SU-8 photolithography gold surfaces were markedly contaminated, which decreased the effective surface area and surface coverage of a model molecule mercaptohexanol (MCH). Three surface pretreatment methods compatible with microfabricated devices were compared. The investigated methods were (i) cyclic voltammetry in dilute H2SO4, (ii) gentle basic piranha followed by linear sweep voltammetry in dilute KOH, and (iii) oxygen plasma treatment followed by incubation in ethanol. It was shown that all three methods significantly decreased the contamination and increased MCH surface coverage. Most importantly, it was also revealed that surface pretreatments may induce structural changes to the gold surfaces. Accordingly, these alterations influence the characteristics of MCH functionalization.
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| 40. |
- Malinovskis, Paulius, et al.
(författare)
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Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance
- 2018
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 149, s. 51-62
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Tidskriftsartikel (refereegranskat)abstract
- Multicomponent carbide thin films of (CrNbTaTiW)C (30–40 at.% C) with different metal contents were depos-ited at different temperatures using non-reactive DC magnetron sputtering. The lattice distortion for the metallattice was estimated to vary from about 3 to 5%. Most films crystallized in the cubic B1 structure but Ta/W-rich films deposited at 600 °C exhibited a tetra gonal distortion. X-ray diffraction results sh ow that near-equimolar films exhibited a strong (111) texture. In contrast, Ta/W-rich films exhibited a shift from (111) to(100) texture at 450 °C. The in-plane relationship was determined to MC(111)[-12-1]//Al2O3(001)[110] with alattice mismatch of about 11% along the Al2O3[110] direction. A segregation of Cr to the grain boundaries was ob-served in all films. The microstructure was found to be the most important factor for high hardness. Less denseNb-rich and near-equimolar films deposited at low tem peratures exhib ited the low est hardnes s (12 GPa),while very dense Ta/W-rich high temperature films were found to be the hardest (36 GPa). No correlation wasfound between the lattice distortion and the hardness. Corrosion studies revealed that the multicomponentfilms exhibited excellent corrosion resistance, superior to that of a reference hyper-duplex stainless steel, in1.0 M HCl.
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| 41. |
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| 42. |
- Munktell, Sara, et al.
(författare)
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Towards high throughput corrosion screening using arrays of bipolar electrodes
- 2015
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Ingår i: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : Elsevier BV. - 1572-6657. ; 747, s. 77-82
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Tidskriftsartikel (refereegranskat)abstract
- In this work we demonstrate the possibility of combining bipolar electrochemistry with arrays of samples as a fast and versatile method for comparing their corrosion resistances at a wide range of potentials. Several steel samples of different grades were arranged in a bipolar electrochemical cell and exposed to an electric field by applying a constant current. The gradient in electrochemical potential difference across each sample resulted in a pitting corrosion gradient on the anodic parts which was used as a simple, straightforward and qualitative method of screening the corrosion properties of several samples in one single experiment. In the cell, all samples acted as individual bipolar electrodes but interestingly, the current density for each sample was also found to be influenced by the corrosion resistances of its neighbours. Results from the bipolar array were also compared with standard polarisation curves and the pitting resistance equivalent number (PREN) for each steel type.
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| 43. |
- Munktell, Sara, et al.
(författare)
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Towards high-throughput Corrosion Screening using Bipolar Electrochemistry
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work the concept of using arrays of bipolar electrodes for a fast and simple way to screen corrosion properties is presented.When an isolated conducting object is exposed to an external electric field the resulting potential difference across its surface can cause part of the total current to pass through said object. The result of this is that the object will act as an anode and a cathode simultaneously and that there will be a gradient in electrochemical potential ranging between the two end poles. The effect has proved useful in various industries and research fields with applications ranging from large scale chemical reactors to the modification of nano-objects1.We have previously demonstrated that bipolar electrochemistry can be used to generate gradients in corrosion damage on steel samples to evaluate their corrosion properties2.When a number of steel samples are placed together in an array configuration and subjected to an external field they all act as individual bipolar electrodes, and in this way many samples can be compared in the same experiment at the same time. The shape of the gradient that forms on the anodic end of the samples will depend on the steels corrosion resistance.When all steel samples placed together are of the same type the BPE-induced gradients are all alike. If steels of different corrosion properties are placed together the least resistant steel will pass more of the current and therefore corrode further3. This effect can be used to enhance differences between samples. Figure 1: Schematic of the BPE-array setup.Figure 2: Gradients on the same type of steel from different setups, arrows roughly indicates the length of the gradient. References[1] G. Loget, D. Zigah, L. Bouffier, N. Sojic, A. Kuhn, Accounts of Chemical Research 2013, 46, 2513-2523.[2] S. Munktell, M. Tydén, J. Högström, L. Nyholm, F. Björefors, Electrochemistry Communications 2013, 35, 274-277.[3] S. Munktell, L. Nyholm, F. Björefors, Journal of Electroanalytical Chemistry 2015, 747, 77-82.
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| 44. |
- Nygren, Kristian, et al.
(författare)
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The influence of nanoeffects on the oxidation of magnetron sputtered Cr-C/Ag thin films containing silver nanoparticles
- 2017
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Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 4:2, s. 418-429
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Tidskriftsartikel (refereegranskat)abstract
- Well-controlled functionalization of carbide-based nanocomposite films with noble-metal surface nanoparticles of different sizes may lead to new materials with novel multifunctional properties. In this work, magnetron sputtering was used to deposit nanocomposite films comprising amorphous chromium carbide (a-CrCx), amorphous carbon (a-C), and a minority of silver in the form of embedded nanoclusters. Up to 510(10) surface nanoparticles per cm(2) with different size distributions were also found to be formed, owing to the diffusion of silver from the bulk of the film. The influences of these conductive nanoparticles on the electrochemical behavior of the films were investigated in dilute sulfuric acid. Although silver is a noble metal, the oxidation potential of the nanoparticles was about 0.4V more negative than the Ag+/Ag standard potential, meaning that the nanoparticles were oxidized in the Cr passive potential region. While this effect can mainly be explained by a low concentration of Ag+ in the electrolyte, the sizes of the nanoparticles and interactions with the matrix were also found to be important. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to analyze the surface chemistries. As Ag can be replaced by other noble metals, the concept is of general interest for further studies.
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| 45. |
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| 46. |
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| 47. |
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| 48. |
- Olsson, Caroline, 1970, et al.
(författare)
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Initial experience with introducing national guidelines for CT- and MRI-based delineation of organs at risk in radiotherapy
- 2019
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Ingår i: Physics and Imaging in Radiation Oncology. - : Elsevier. - 2405-6316. ; 11, s. 88-91
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental problem in radiotherapy is the variation of organ at risk (OAR) volumes. Here we present our initial experience in engaging a large Radiation Oncology (RO) community to agree on national guidelines for OAR delineations. Our project builds on associated standardization initiatives and invites professionals from all radiotherapy departments nationwide. Presently, one guideline (rectum) has successfully been agreed on by a majority vote. Reaching out to all relevant parties in a timely manner and motivating funding agencies to support the work represented early challenges. Population-based data and a scalable methodological approach are major strengths of the proposed strategy.
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| 49. |
- Oltean, Alina, 1987-
(författare)
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Building Sustainable Batteries : Organic electrodes based on Li- and Na-benzenediacrylate
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As possible alternatives to the conventional inorganic Li- or Na-ion battery electrode materials, organic compounds have recently drawn considerable attention. However, major challenges such as poor electronic conductivity, solubility in battery electrolyte or fast capacity decay of the resulting electrochemical cells are some of the reasons that hold these compounds back from becoming commercial solutions in the energy system.The goal of this thesis work was to investigate the background to these phenomena and find strategies for improvements. Two different compounds were studied: dilithium and disodium benzenediacrylate, in their respective cells. First, improving the performance of the dilithium compound was performed by applying different electrode fabrication strategies. A freeze-drying technique was combined with carbon coating in the liquid state, which rendered an improved electrode morphology. Moreover, when using the compound in pouch cell format instead of Swagelok® cells, a different technique was applied: calendaring. Successful results were obtained both in half-cells and in full-cells when the compound was cycled versus LiFePO4-based cathodes. Second, the sodium analogue was investigated, and while the synthesis of this compound is straightforward, the electrochemical performance in Na-ion battery cells displays an unexpected degree of complexity. The compound displays a considerably faster capacity decrease in comparison to the Li compound, and generally a poor chemical stability in the applied system. When cycled at higher currents (C-rates of C/4 or C/10, in comparison to C/40), the compound presents an capacity increase while the Li decreases, likely due to a chemical process more dependent on time than on the number of cycles for the Na compound.The fast capacity decay in the first cycles of these types of compounds is often considered to be related to the Solid Electrolyte Interphase (SEI) layer formation. Its study was also performed and it was concluded that the Na compound has a thicker SEI layer in comparison to the Li counterpart, and mostly consisted of inorganic species such as the electrolyte salt and its decomposition products. Finally, a concept for a sustainable manufacturing and recycling process of a hybrid full cell is also performed with positive results.Although the organic compounds cannot yet outperform the inorganic compounds used commercially in Li-ion batteries, important steps towards their employment in the energy system have been taken in this thesis work.
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| 50. |
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