| 1. |
- Hudson, Lawrence N, et al.
(author)
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The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
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In: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
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Journal article (peer-reviewed)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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| 2. |
- Ahlberg Tidblad, Annika, et al.
(author)
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Future Material Developments for Electric Vehicle Battery Cells Answering Growing Demands from an End-User Perspective
- 2021
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In: Energies. - : MDPI. - 1996-1073. ; 14:14
-
Research review (peer-reviewed)abstract
- Nowadays, batteries for electric vehicles are expected to have a high energy density, allow fast charging and maintain long cycle life, while providing affordable traction, and complying with stringent safety and environmental standards. Extensive research on novel materials at cell level is hence needed for the continuous improvement of the batteries coupled towards achieving these requirements. This article firstly delves into future developments in electric vehicles from a technology perspective, and the perspective of changing end-user demands. After these end-user needs are defined, their translation into future battery requirements is described. A detailed review of expected material developments follows, to address these dynamic and changing needs. Developments on anodes, cathodes, electrolyte and cell level will be discussed. Finally, a special section will discuss the safety aspects with these increasing end-user demands and how to overcome these issues.
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| 3. |
- Aktekin, Burak, et al.
(author)
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Concentrated LiFSI-€“Ethylene Carbonate Electrolytes and Their Compatibility with High-Capacity and High-Voltage Electrodes
- 2022
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In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 5:1, s. 585-595
-
Journal article (peer-reviewed)abstract
- The unusual physical and chemical properties of electrolytes with excessive salt contents have resulted in rising interest in highly concentrated electrolytes, especially for their application in batteries. Here, we report strikingly good electrochemical performance in terms of conductivity and stability for a binary electrolyte system, consisting of lithium bis(fluorosulfonyl)imide (LiFSI) salt and ethylene carbonate (EC) solvent. The electrolyte is explored for different cell configurations spanning both high-capacity and high-voltage electrodes, which are well known for incompatibilities with conventional electrolyte systems: Li metal, Si/graphite composites, LiNi0.33Mn0.33Co0.33O2 (NMC111), and LiNi0.5Mn1.5O4 (LNMO). As compared to a LiTFSI counterpart as well as a common LP40 electrolyte, it is seen that the LiFSI:EC electrolyte system is superior in Li-metal–Si/graphite cells. Moreover, in the absence of Li metal, it is possible to use highly concentrated electrolytes (e.g., 1:2 salt:solvent molar ratio), and a considerable improvement on the electrochemical performance of NMC111-Si/graphite cells was achieved with the LiFSI:EC 1:2 electrolyte both at the room temperature and elevated temperature (55 °C). Surface characterization with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) showed the presence of thicker surface film formation with the LiFSI-based electrolyte as compared to the reference electrolyte (LP40) for both positive and negative electrodes, indicating better passivation ability of such surface films during extended cycling. Despite displaying good stability with the NMC111 positive electrode, the LiFSI-based electrolyte showed less compatibility with the high-voltage spinel LNMO electrode (4.7 V vs Li+/Li).
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| 4. |
- Andersson, Rassmus, et al.
(author)
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Designing Polyurethane Solid Polymer Electrolytes for High-Temperature Lithium Metal Batteries
- 2022
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In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 5:1, s. 407-418
-
Journal article (peer-reviewed)abstract
- Potentially high-performance lithium metal cells in extreme high-temperature electrochemical environments is a challenging but attractive battery concept that requires stable and robust electrolytes to avoid severely limiting lifetimes of the cells. Here, the properties of tailored polyester and polycarbonate diols as the soft segments in polyurethanes are investigated and electrochemically evaluated for use as solid polymer electrolytes in lithium metal batteries. The polyurethanes demonstrate high mechanical stability against deformation at low flow rates and moreover at temperatures up above 100 degrees C, enabled by the hard urethane segments. The results further indicate transferrable ion transport properties of the pure polymers when incorporated as the soft segments in the polyurethanes, offering designing opportunities of the polyurethane by tuning the soft segment ratio and composition. Long-term electrochemical cycling of polyurethane-containing cells in lithium metal batteries at 80 degrees C proves the stability at elevated temperatures as well as the compatibility with lithium metal with stable cycling maintained after 2000 cycles.
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| 5. |
- Andersson, Rassmus
(author)
-
Discovering new ground in ion transport: Exploring coordination effects in polymer electrolytes : – From method development to battery implementation
- 2024
-
Doctoral thesis (other academic/artistic)abstract
- The exponentially increasing demand for portable and stationary energy storage devices is pushing the development of lithium-ion batteries (LIBs). This requires safer and more sustainable electrolytes where solid polymer electrolytes (SPEs) are a viable alternative to the flammable liquid electrolytes used nowadays. However, SPEs are characterized by poor ionic conductivity compared to their liquid equivalents, preventing large-scale implementation. Furthermore, to meet the increasing production rate of batteries, alternative battery chemistries based on more abundant resources than Li are explored. To address these matters, a fundamental understanding of ion transport in SPEs for a range of relevant cations is vital in the development process.In the thesis, the ion transport is explored on a fundamental level for Li+ in addition to cations “beyond Li” such as Na+, K+ and Mg2+ in polyether-, polyester- and polycarbonate-based SPEs, where the core encompasses the connection between the ion coordination strength and the transference number (T+). New methods to investigate these properties have been developed especially targeting these more challenging cations. To study the ion coordination strength, two qualitative and one quantitative methods based on NMR and FTIR, are presented. In addition, eNMR and EIS have been combined to determine T+.Regardless of the cation investigated, the strongest coordination was observed for polyethylene oxide, stemming from its chelating effect on the cations. In contrast, poly(trimethylene carbonate) exhibited the weakest coordination, while poly(ε-caprolactone) fell in between. A direct correlation between the coordination strength and the T+ was also recognized, where strong interactions are accompanied by low T+ and vice versa. Moreover, the divalent Mg2+ displayed particularly interesting transport characteristics, where the [MgTFSI]+ speciation appears to be a large contributor to the net Mg mobility. Lastly, the outcome of incorporating an ion-conducting polymer as the soft segment in polyurethanes is that the transport mechanism of the pure SPE remains. In combination with sustained long-term cycling in lithium metal batteries, the polyurethanes illustrate opportunities for new designs by adjusting the soft segments. Similarly, the properties of poly(1-oxoheptamethylene) can be controlled by tuning its saturation degree, which is crucial for the ion conduction and mechanical properties in lithium metal batteries, since it highly affects the crystallinity and the crosslinking of the systems.In summary, this thesis contributes toward the understanding of ion transport in systems belonging to “next-generation” batteries, where SPEs for lithium-metal batteries as well as for cations “beyond Li” are considered to play an important part.
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| 6. |
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| 7. |
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| 8. |
- Andersson, Rassmus, et al.
(author)
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Micro versus Nano : Impact of Particle Size on the Flow Characteristics of Silicon Anode Slurries
- 2020
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In: ENERGY TECHNOLOGY. - : WILEY-V C H VERLAG GMBH. - 2194-4288 .- 2194-4296. ; 8:7
-
Journal article (peer-reviewed)abstract
- Silicon is interesting for use as a negative electrode material in Li-ion batteries due to its extremely high gravimetric capacity compared with today's state-of-the-art material, graphite. However, during cycling the Si particles suffer from large volume changes, leading to particle cracking, electrolyte decompositions, and electrode disintegration. Although utilizing nm-sized particles can mitigate some of these issues, it would instead be more cost-effective to incorporate mu m-sized silicon particles in the anode. Herein, it is shown that the size of the Si particles not only influences the electrode cycling properties but also has a decisive impact on the processing characteristics during electrode preparation. In water-based slurries and suspensions containing mu m-Si and nm-Si particles, the smaller particles consistently give higher viscosities and more pronounced viscoelastic properties, particularly at low shear rates. This difference is observed even when the Si particles are present as a minor component in blends with graphite. It is found that the viscosity follows the particle volume fraction divided by the particle radius, suggesting that it is dependent on the surface area concentration of the Si particles.
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| 9. |
- Andersson, Rassmus, et al.
(author)
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Quantifying the ion coordination strength in polymer electrolytes
- 2022
-
In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 24:26, s. 16343-16352
-
Journal article (peer-reviewed)abstract
- In the progress of implementing solid polymer electrolytes (SPEs) into batteries, fundamental understanding of the processes occurring within and in the vicinity of the SPE are required. An important but so far relatively unexplored parameter influencing the ion transport properties is the ion coordination strength. Our understanding of the coordination chemistry and its role for the ion transport is partly hampered by the scarcity of suitable methods to measure this phenomenon. Herein, two qualitative methods and one quantitative method to assess the ion coordination strength are presented, contrasted and discussed for TFSI-based salts of Li+, Na+ and Mg2+ in polyethylene oxide (PEO), poly(epsilon-caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC). For the qualitative methods, the coordination strength is probed by studying the equilibrium between cation coordination to polymer ligands or solvent molecules, whereas the quantitative method studies the ion dissociation equilibrium of salts in solvent-free polymers. All methods are in agreement that regardless of cation, the strongest coordination strength is observed for PEO, while PTMC exhibits the weakest coordination strength. Considering the cations, the weakest coordination is observed for Mg2+ in all polymers, indicative of the strong ion-ion interactions in Mg(TFSI)(2), whilst the coordination strength for Li+ and Na+ seems to be more influenced by the interplay between the cation charge/radius and the polymer structure. The trends observed are in excellent agreement with previously observed transference numbers, confirming the importance and its connection to the ion transport in SPEs.
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| 10. |
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| 11. |
- Bergfelt, Andreas, et al.
(author)
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A Mechanical Robust yet highly Conductive Diblock Copolymer-based Solid Polymer Electrolyte for Room Temperature Structural Battery Applications
- 2020
-
In: ACS Applied Polymer Materials. - : American Chemical Society (ACS). - 2637-6105. ; 2:2, s. 939-948
-
Journal article (peer-reviewed)abstract
- In this paper we present a solid polymer electrolyte (SPE) that uniquely combines ionic conductivity and mechanical robustness. This is achieved with a diblock copolymer poly(benzyl methacrylate)-poly(ε-caprolactone-r-trimethylene carbonate). The SPE with 16.7 wt% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) showed the highest ionic conductivity (9.1×10−6 S cm−1 at 30 °C) and apparent transference number (T+) of 0.64 ± 0.04. Due to the employment of the benzyl methacrylate hard-block, this SPE is mechanically robust with a storage modulus (E') of 0.2 GPa below 40 °C, similar to polystyrene, thus making it a suitable material also for load-bearing constructions. The cell Li|SPE|LiFePO4 is able to cycle reliably at 30 °C for over 300 cycles. The promising mechanical properties, desired for compatibility with Li-metal, together with the fact that BCT is a highly reliable electrolyte material makes this SPE an excellent candidate for next-generation all-solid-state batteries.
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| 12. |
- Bergfelt, Andreas, et al.
(author)
-
Mechanically Robust and Highly Conductive Di-Block Copolymers as Solid Polymer Electrolytes for Room Temperature Li-ion Batteries
- 2018
-
Conference paper (other academic/artistic)abstract
- Alternative solid polymer electrolytes (SPEs) hosts to the archetype poly(ethylene oxide) are gaining attention thanks to their appealing properties, such as higher cation transport number, thermal stability and electrochemical stability [1]. In addition, high mechanical stability is required in order to integrate easy-to-use materials into flexible or ‘structural’ batteries [2, 3]. In this work, a solid polymer electrolyte (SPE) featuring high ionic conductivity and mechanical robustness at room temperature is presented. The SPE consists of a di-block copolymer, poly(benzyl methacrylate)-poly(ε-caprolactone-r-trimethylene carbonate) (BCT), mixed with different loadings of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The highest ionic conductivity achieved for these SPEs was found with 16.7 wt% LiTFSI loading (BCT17), reaching 9.1 x 10-6 S cm-1 at 30 °C. The limited current fraction (F+) for the BCT17 electrolyte was calculated to be 0.64 with the Bruce-Vincent method. Furthermore, dynamic mechanical analysis showed a storage modulus (E’) of 0.2 GPa below 40 °C and 1 MPa above 50 °C. These results indicate that BCT with LiTFSI is a competitive electrolyte, combining high ionic conductivity and modulus at ambient temperatures. LiFePO4|BCT17|Li half-cells showed good cycling performance at 60 °C. At 30 °C, where the SPE possessed significantly higher modulus, decent cell performance could still be achieved after several optimization steps. These included incorporating a SPE as binder, and infiltration cast the SPE on the electrode to maximize the contact between both components, thereby improving the interfacial contact and decreasing the cell resistance and overpotential when cycling the battery device. References[1] J. Mindemark, M.J. Lacey, T. Bowden, D. Brandell. Prog Polym Sci, (2018). DOI: 10.1016/j.progpolymsci.2017.12.004.[2] J.F. Snyder, R.H. Carter, E.D. Wetzel. Chem Mater, 19 (2007) 3793-801.[3] W.S. Young, W.F. Kuan, Thomas H. Epps. J Polym Sci, Part B: Polym Phys, 52 (2014) 1-16.
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| 13. |
- Dhillon, Shweta, et al.
(author)
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Modelling capacity fade in silicon-graphite composite electrodes for lithium-ion batteries
- 2021
-
In: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 377
-
Journal article (peer-reviewed)abstract
- Silicon-based composite electrodes in lithium ion batteries attract increasing attention because of their high theoretical capacity. Here, numerical simulations are used to better understand the interplay between electrochemical and morphological behavior of the silicon-graphite (1:2.7) composite electrode during galvanostatic cycling. Finite element methodology is used to solve a one-dimensional model based on the porous electrode and concentrated solution theory. Porosity changes in the silicon electrode and solid electrolyte interphase layer growth are also included in the model. The simulation results show that at lower rates, the electrode with high initial porosity is being fully utilized before the lower cut-off potential is reached. When comparing the computational results with experimental observations, it can be seen that the main reason for capacity fade is the increase in tortuosity in the diffusion pathway of lithium ions due to cracking of the silicon composite electrode upon electrochemical cycling.
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| 14. |
- Gogoi, Neeha, et al.
(author)
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Base-driven Ring-Opening Reactions of Vinylene Carbonate
- 2024
-
In: Journal of the Electrochemical Society. - : Institute of Physics (IOP). - 0013-4651 .- 1945-7111.
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Journal article (peer-reviewed)abstract
- Vinylene carbonate (VC) is the most commonly applied performance-enhancing electrolyte additives in Li-ion batteries to date. Despite numerous studies, there is a lack of consensus regarding the various reaction pathways of VC and their implications. VC has primarily been observed to either polymerize forming poly(vinylene carbonate) (poly(VC)) or decompose releasing major amounts of CO2, two seemingly contradictory processes. Herein, we present evidence of additional reaction pathways of VC highlighting its role as a H2O scavenging agent. In contrast to the typical electrolyte solvent ethylene carbonate, VC reacts much more rapidly with water impurities, especially when in contact with hydroxides, forming products less likely to influence cell performance. Efficient removal of water and hydroxides is essential to preserve the stability of Li-ion electrolyte solvent and salt, hence guaranteeing a long lifetime of the battery. Model studies pinpointing reaction pathways of electrolytes and additives, as presented herein, are critical not only to improve modern Li-ion cells but also to establish design principles for future battery chemistries.
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| 15. |
- Gogoi, Neeha, et al.
(author)
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Reactivity of Organosilicon Additives with Water in Li-ion Batteries
- 2024
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 128:4, s. 1654-1662
-
Journal article (peer-reviewed)abstract
- Introducing small volumes of organosilicon-containing additives as part of lithium-ion battery (LIB) electrolyte engineering has been getting a lot of attention owing to these additives’ multifunctional properties. Tris(trimethylsilyl)phosphate (TMSPa) is a prominent member of this class of additives and scavenges Lewis bases such as water, although the rate at which the reaction occurs and the fate of the resultant product in the battery system still remain unknown. Herein, we have employed complementary nuclear magnetic resonance and gas chromatography–mass spectrometry to systematically study the reactivity of TMSPa with water in conventional organic carbonate solvents mimicking the Li-ion cell environment. The reaction products are identified, and a working reaction pathway is proposed by following the chemical evolution of the products over varying time and temperatures. We found that the main reaction products are trimethylsilanol (TMSOH) and phosphoric acid (H3PO4); however, various P–O–Si-containing intermediates were also found. Similar to water, the Lewis base TMSOH can undergo reaction with TMSPa at room temperature to form hexamethyldisiloxane and can also activate ethylene carbonate (EC) ring-opening reactions at elevated temperatures (≥80 °C), yielding a TMS derivative with ethylene glycol (TMS-EG). While the formation of TMS-EG at the expense of EC is in principle an unwanted parasitic reaction, it should be noted that this reaction is only activated at elevated temperatures in comparison to EC ring-opening by H2O, which takes place at ≥40 °C. Thus, the study underlines the advantages of organo-silicon compounds as electrolyte additives. Elucidating the reaction mechanism in model systems like this is important for future studies of similar additives in order to improve the accuracy of additive exploration in LIBs.
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| 16. |
- Gogoi, Neeha, et al.
(author)
-
Silyl-Functionalized Electrolyte Additives and Their Reactivitytoward Lewis Bases in Li-Ion Cells br
- 2022
-
In: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 34:8, s. 3831-3838
-
Journal article (peer-reviewed)abstract
- Silyl groups are included in a wide range of electrolyteadditives to enhance the performance of state-of-the-art Li-ion batteries. Arecognized representative thereof is tris-(trimethylsilyl)phosphate(TMSPa) which, along with the similarly structured phosphite, has beenat the center of numerous electrolyte studies. Even though the silyl grouphas already been widely reported to be specifically reactive towardsfluorides, herein, a reactivity towards several Lewis bases typically found inLi-ion cells is postulated and investigated with the aim to establish a moresimplified and generally applicable reaction mechanism thereof. Bothgaseous and electrolyte soluble reactants and products are monitored bycombining nuclear magnetic resonance and injection cell-coupled massspectrometry. Experimental observations are supported by computationalmodels. The results clearly demonstrate that the silyl groups react withwater, hydroxide, and methoxide and thereby detach in a stepwise fashion from the central phosphate in TMSPa. Intermolecularinteraction between TMSPa and the reactants likely facilitates dissolution and lowers the free energy of reaction. Lewis bases are wellknown to trigger side reactions involving both the Li-ion electrode and electrolyte. By effectively scavenging these, the silyl group canbe explained to lower cell impedance and prolong the lifetime of modern Li-ion batteries.
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| 17. |
- Heintz, Mads C., et al.
(author)
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Photovoltaic Wafering Silicon Kerf Loss as Raw Material : Example of Negative Electrode for Lithium‐Ion Battery
- 2023
-
In: ChemElectroChem. - : Wiley-VCH Verlagsgesellschaft. - 2196-0216. ; 10:19
-
Journal article (peer-reviewed)abstract
- Silicon powder kerf loss from diamond wire sawing in the photovoltaic wafering industry is a highly appealing source material for use in lithium-ion battery negative electrodes. Here, it is demonstrated for the first time that the kerf particles from three independent sources contain ~50 % amorphous silicon. The crystalline phase is in the shape of nano-scale crystalline inclusions in an amorphous matrix. From literature on wafering technology looking at wafer quality, the origin and mechanisms responsible for the amorphous content in the kerf loss powder are explained. In order to better understand for which applications the material could be a valuable raw material, the amorphicity and other relevant features are thoroughly investigated by a large amount of experimental methods. Furthermore, the kerf powder was crystallized and compared to the partly amorphous sample by operando X-ray powder diffraction experiments during battery cycling, demonstrating that the powders are relevant for further investigation and development for battery applications.
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| 18. |
- Hernández, Guiomar, et al.
(author)
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Do non-coordinating polymers function as host materials for solid polymer electrolytes? : The case of PVdF-HFP
- 2023
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 11:28, s. 15329-15335
-
Journal article (peer-reviewed)abstract
- In the search for novel solid polymer electrolytes (SPEs), primarily targeting battery applications, a range of different polymers is currently being explored. In this context, the non-coordinating poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer is a frequently utilized system. Considering that PVdF-HFP should be a poor solvent for cation salts, it is counterintuitive that this is a functional host material for SPEs. Here, we do an in-depth study of the salt dissolution properties and ionic conductivity of PVdF-HFP-based electrolytes, using two different fabrication methods and also employing a low-molecular-weight solvent analogue. It is seen that PVdF-HFP is remarkably poor as an SPE host, despite its comparatively high dielectric constant, and that the salt dissolution properties instead are controlled by fluorophilic interactions of the anion with the polymer.
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| 19. |
- Hernández, Guiomar, et al.
(author)
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Elimination of Fluorination : The Influence of Fluorine-Free Electrolytes on the Performance of LiNi1/3Mn1/3Co1/3O2/Silicon-Graphite Li-Ion Battery Cells
- 2020
-
In: ACS Sustainable Chemistry and Engineering. - : AMER CHEMICAL SOC. - 2168-0485. ; 8:27, s. 10041-10052
-
Journal article (peer-reviewed)abstract
- In the quest for environmentally friendly and safe batteries, moving from fluorinated electrolytes that are toxic and release corrosive compounds, such as HF, is a necessary step. Here, the effects of electrolyte fluorination are investigated for full cells combining silicon- graphite composite electrodes with Li-Ni1/3Mn1/3Co1/3O2 (NMC111) cathodes, a viable cell chemistry for a range of potential battery applications, by means of electrochemical testing and postmortem surface analysis. A fluorine-free electrolyte based on lithium bis(oxalato) borate (LiBOB) and vinylene carbonate (VC) is able to provide higher discharge capacity (147 mAh g(NMC)(-1)) and longer cycle life at C/10 (84.4% capacity retention after 200 cycles) than a cell with a highly fluorinated electrolyte containing LiPF6, fluoroethylene carbonate (FEC) and VC. The cell with the fluorine-free electrolyte is able to form a stable solid electrolyte interphase (SEI) layer, has low overpotential, and shows a slow increase in cell resistance that leads to improved electrochemical performance. Although the power capability is limiting the performance of the fluorine-free electrolyte due to higher interfacial resistance, it is still able to provide long cycle life at C/2 and outperforms the highly fluorinated electrolyte at 40 degrees C. X-ray photoelectron spectroscopy (XPS) results showed a F-rich SEI with the highly fluorinated electrolyte, while the fluorine-free electrolyte formed an O-rich SEI. Although their composition is different, the electrochemical results show that both the highly fluorinated and fluorine-free electrolytes are able to stabilize the silicon-based anode and support stable cycling in full cells. While these results demonstrate the possibility to use a nonfluorinated electrolyte in high-energy-density full cells, they also address new challenges toward environmentally friendly and nontoxic electrolytes.
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| 20. |
- Hernández, Guiomar, et al.
(author)
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Fluorine-Free Electrolytes for Lithium and Sodium Batteries
- 2022
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In: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; 5:6
-
Research review (peer-reviewed)abstract
- Fluorinated components in the form of salts, solvents and/or additives are a staple of electrolytes for high-performance Li- and Na-ion batteries, but this comes at a cost. Issues like potential toxicity, corrosivity and environmental concerns have sparked interest in fluorine-free alternatives. Of course, these electrolytes should be able to deliver performance that is on par with the electrolytes being in use today in commercial batteries. This begs the question: Are we there yet? This review outlines why fluorine is regarded as an essential component in battery electrolytes, along with the numerous problems it causes and possible strategies to eliminate it from Li- and Na-ion battery electrolytes. The examples provided demonstrate the possibilities of creating fully fluorine-free electrolytes with similar performance as their fluorinated counterparts, but also that there is still a lot of room for improvement, not least in terms of optimizing the fluorine-free systems independently of their fluorinated predecessors.
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| 21. |
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| 22. |
- Hernández, Guiomar, et al.
(author)
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Going beyond sweep voltammetry : Alternative approaches in search of the elusive electrochemical stability of polymer electrolytes
- 2021
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 168:10
-
Journal article (peer-reviewed)abstract
- Solid polymer electrolytes (SPEs) are promising candidates for solid-state lithium-ion batteries. Potentially, they can be used with lithium metal anodes and high-voltage cathodes, provided that their electrochemical stability is sufficient. Thus far, the oxidative stability has largely been asserted based on results obtained with sweep voltammetry, which are often determined and reliant on arbitrary assessments that are highly dependent on the experimental conditions and do not take the interaction between the electrolyte and the electrode material into account. In this study, alternative techniques are introduced to address the pitfalls of sweep voltammetry for determining the oxidative stability of SPEs. Staircase voltammetry involves static conditions and eliminates the kinetic aspects of sweep voltammetry, and coupled with impedance spectroscopy provides information of changes in resistance and interphase layer formation. Synthetic charge–discharge profile voltammetry applies the real voltage profile of the active material of interest. The added effect of the electrode active material is investigated with a cut-off increase cell cycling method where the upper cut-off voltage during galvanostatic cycling is gradually increased. The feasibility of these techniques has been tested with both poly(ethylene oxide) and poly(trimethylene carbonate) combined with LiTFSI, thereby showing the applicability for several categories of SPEs.
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| 23. |
- Hernández, Guiomar, et al.
(author)
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New Insights in the Synthesis of High-Molecular-Weight Aromatic Polyamides-Improved Synthesis of Rod-like PPTA
- 2023
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In: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 24:3
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Journal article (peer-reviewed)abstract
- By employing a variation of the polyamidation method using in situ silylated diamines and acid chlorides, it was possible to obtain a rod-type polyamide: poly(p-phenylene terephthalamide) (PPTA, a polymer used in the high-value-added material Kevlar), with a molecular weight much higher than that obtained with the classical and industrial polyamidation method. The optimization of the method has consisted of using, together with the silylating agent, a mixture of pyridine and a high-pKa tertiary amine. The research was complemented by a combination of nuclear magnetic resonance and molecular simulation studies, which determined that the improvements in molecular weight derive mainly from the formation of silylamide groups in the growing polymer.
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| 24. |
- Hernández, Guiomar, et al.
(author)
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Non-Fluorinated Electrolytes for Si-based Li-ion Battery Anodes
- 2018
-
Conference paper (other academic/artistic)abstract
- Although the performance of lithium-ion batteries has been improved to some extent since the initial commercialization,1 cycling stability, safety and sustainability still present some challenges and concerns. In this regard, the battery electrolyte plays an important role. State-of-the-art electrolytes contain the electrolyte salt LiPF6, susceptible to undergo defluorination reactions and form toxic and corrosive compounds, such as HF. Yet, fluorine-containing electrolytes are often considered necessary for enhanced battery performance. On the other hand, replacing LiPF6 with fluorine-free salts would reduce cost, increase safety and decrease toxicity, both in the manufacturing and recycling processes. Among the available fluorine-free salts, lithium bis(oxalato)borate (LiBOB) is a viable candidate due to its enhanced thermal stability.2 Furthermore, additives in the electrolyte are another common source of fluorine, not least fluoroethylene carbonate (FEC) which can form a stable solid electrolyte interface (SEI).3Herein, we compare the cell performance of fluorinated and non-fluorinated electrolytes in NMC/Si-Graphite full cells. Three electrolytes are tested: (1) LP57 (1 M LiPF6 in ethylene carbonate (EC):ethyl methyl carbonate (EMC) 3:7 vol/vol); (2) LP57 with 10 wt% FEC and 2 wt% vinylene carbonate (VC); and (3) 0.7 M LiBOB in EC:EMC 3:7 vol/vol and 2 wt% VC.The cells containing the conventional electrolyte, LP57, feature a rapid capacity fade and continuous decrease in coulombic efficiency. The cell performance is improved when adding SEI-forming additives to the electrolyte (LP57 with FEC and VC). In addition, stable cycling for over 200 cycles are obtained for both the fluorinated (LP57 with FEC and VC) and non-fluorinated (LiBOB with VC) electrolytes.Characterisation by X-ray photoelectron spectroscopy (XPS) of the anode surface showed higher amounts of carbonate species and a thicker SEI layer with the non-fluorinated electrolyte compared to the fluorinated one.1 J. Electrochem. Soc. 2017, 164, A5019-A5025.2 ChemSusChem 2017, 10, 2431-2448.3 J. Electrochem. Soc. 2014, 161, A1933-A1938.
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| 25. |
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| 26. |
- Hernández, Guiomar, et al.
(author)
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Perspective—A League of Our Own: A Perspective on How to Start and Keep the Flow of Women in Energy Storage
- 2022
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In: Journal of The Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 169:2
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Journal article (peer-reviewed)abstract
- Women are under-represented in science, technology, engineering and mathematics (STEM) majors and careers in most industrialized countries around the world. The aim of this perspective is to offer a view of the current status in energy storage, mainly in Europe, while focusing on proposed solutions towards gender balance and providing examples of activities that could be carried out within industry and academia. It should be noted that we are not social scientists, the proposed solutions and activities are just based on our own experiences, and our main objective is to continue the discussion of gender equality in the energy storage field.
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| 27. |
- Hernández, Guiomar, et al.
(author)
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Polyimide-polyether bindersediminishing the carbon content in lithium-sulfur batteries
- 2017
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In: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 6, s. 264-270
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Journal article (peer-reviewed)abstract
- Lithium-sulfur batteries are on the run to become the next generation energy storage technology. First of all due to its high theoretical energy density but also for its sustainability and low cost. However, there are still several challenges to take into account such as reducing the shuttle effect, decreasing the amount of conductive carbon to increase the energy density or enhancing the sulfur utilization. Herein, redox-active binders based on polyimide-polyether copolymers have been proposed as a solution to those drawbacks. These multiblock copolymers combine the ability of poly (ethylene oxide) to act as polysulfide trap and the properties of the imide groups to redox mediate the charge-discharge of sulfur. Thus, poly (ethylene oxide) block helps with the shuttle effect and mass transport in the electrode whereas the polyimide part enhances the charge transfer promoting the sulfur utilization. Sulfur cathodes containing pyromellitic, naphthalene or perylene polyimide-polyether binders featured improved cell performance in comparison with pure PEO binder. Among them, the electrode with naphthalene polyimide-PEO binder showed the best results with an initial capacity of 1300 mA h g(-1) at C/5, low polarization and 70% capacity retention after 30 cycles. Reducing the amount of carbon black in the cathode to 5 wt%, the cell with the redox-active binder was able to deliver 500 mA h g(-1) at C/5 with 78% capacity retention after 20 cycles. Our results demonstrate the possibility to reduce the amount of carbon by introducing polyimide-polyether copolymers as redox-active binders, increasing the sulfur utilization, redox kinetics and stability of the cell. (C) 2017 Elsevier Ltd. All rights reserved.
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| 28. |
- Hudson, Lawrence N., et al.
(author)
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The PREDICTS database : a global database of how local terrestrial biodiversity responds to human impacts
- 2014
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:24, s. 4701-4735
-
Journal article (peer-reviewed)abstract
- Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups - including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems - ). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.
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| 29. |
- Jeschull, Fabian, et al.
(author)
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Multivalent Cation Transport in Polymer Electrolytes : Reflections on an Old Problem
- 2024
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In: Advanced Energy Materials. - : Wiley-VCH Verlagsgesellschaft. - 1614-6832 .- 1614-6840. ; 14:4
-
Journal article (peer-reviewed)abstract
- Today an unprecedented diversification is witnessed in battery technologies towards so-called post-Li batteries, which include both other monovalent (Na+ or K+) and multivalent ions (e.g., Mg2+ or Ca2+). This development is driven, among other factors, by goals to establish more sustainable and cheaper raw material platforms, using more abundant raw material, while maintaining high energy densities. For these new technologies a decisive role falls to the electrolyte, that ultimately needs to form stable electrode-electrolyte interfaces and provide sufficient ionic conductivity, while guaranteeing high safety. The transport of metal-ions in a polymer matrix is studied extensively as solid electrolytes for battery applications, particularly for Li-ion batteries and are now also considered for multivalent systems. This poses a great challenge as ion transport in the solid becomes increasingly difficult for multivalent ions. Interestingly, this topic is a subject of interest for many years in the 80s and 90s and many of the problems then are still causing issues today. Owing to recent progress in this field new possibilities arise for multivalent ion transport in solid polymer electrolytes. For this reason, in this perspective a stroll down memory lane is taken, discuss current advancements and dare a peek into the future.
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| 30. |
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| 31. |
- Lee, Tian Khoon, et al.
(author)
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Polyester-ZrO2 Nanocomposite Electrolytes with High Li Transference Numbers for Ambient Temperature All-Solid-State Lithium Batteries
- 2021
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In: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; 4:4, s. 653-662
-
Journal article (peer-reviewed)abstract
- Polyester- and polycarbonate-based polymer electrolytes have attracted great interest after displaying promising functionality for solid-state Li batteries. In this present work, poly(epsilon-caprolactone-co-trimethylene carbonate) electrolytes are further developed by the inclusion of ZrO2 particles, prepared by an in situ sol-gel method. SEM micrographs show that the ZrO2 particles are uniform and 30-50 nm in size. Contrary to many studies on filler-polymer electrolytes, the changes in ionic conductivity are less significant upon addition of zirconia filler to the polymer electrolyte, but remain at similar to 10(-5) S cm(-1) at room temperature. This can be explained by the amorphous nature of the polymer. Instead, high lithium transference numbers (0.83-0.87) were obtained. Plating/stripping tests with Li metal electrodes show long-term cycling performance for >1000 cycles at 0.2 mA cm(-2). Promising solid-state lithium battery cycling results at ambient temperature using the material are also shown.
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| 32. |
- Mandal, Prithwiraj, et al.
(author)
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Influence of Binder Crystallinity on the Performance of Si Electrodes with Poly(vinyl alcohol) Binders
- 2021
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In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:4, s. 3008-3016
-
Journal article (peer-reviewed)abstract
- Silicon is a highly promising electrode material for Li-ion batteries because of its high theoretical capacity, but severe volume changes during cycling leads to pulverization and rapid capacity fading. The use of alternative and water-soluble polymer binders such as poly(vinyl alcohol) (PVA) or poly(acrylic acid) (PAA) can improve the cycling performance of Si-based Li-ion batteries. Here, we investigate the effect of the substitution of the hydroxyl groups of PVA chains by carboxylic acid and acetate groups on the electrochemical performance of Si anodes in Li-ion batteries. Using modified PVAs, a model system is created spanning the chemical space between PVA and PAA, and the role of different Si-adhering functionalities is investigated. When comparing the electrochemical performance of Li-ion battery cells using Si anodes and the investigated binder systems, PVA with the highest degree of hydrolysis exhibits a superior performance (100 cycles with 1019 mAh g(-1)) compared to modified PVAs and PAA as a binder for Si anodes. An increased degree of hydrolysis of PVA is also seen to be beneficial for high capacity retention. These effects can be largely explained by the crystallinity of the binder system, which renders an improved electrode integrity during cycling and less swelling of the Si particles.
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| 33. |
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| 34. |
- Nkosi, Funeka P., et al.
(author)
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Garnet-Poly(epsilon-caprolactone-co-trimethylene carbonate) Polymer-in-Ceramic Composite Electrolyte for All-Solid-State Lithium-Ion Batteries
- 2021
-
In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:3, s. 2531-2542
-
Journal article (peer-reviewed)abstract
- A composite electrolyte based on a garnet electrolyte (LLZO) and polyester-based co-polymer (80:20 epsilon-caprolactone (CL)-trimethylene carbonate, PCL-PTMC with LiTFSI salt) is prepared. Integrating the merits of both ceramic and co-polymer electrolytes is expected to address the poor ionic conductivity and high interfacial resistance in solid-state lithium-ion batteries. The composite electrolyte with 80 wt % LLZO and 20 wt % polymer (PCL-PTMC and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at 72:28 wt %) exhibited a Li-ion conductivity of 1.31 X 10(-4) S/cm and a transference number (t(Li+)) of 0.84 at 60 degrees C, notably higher than those of the pristine PCL-PTMC electrolyte. The prepared composite electrolyte also exhibited an electrochemical stability of up to 5.4 V vs Li+/Li. The interface between the composite electrolyte and a LiFePO4 (LFP) cathode was also improved by direct incorporation of the polymer electrolyte as a binder in the cathode coating. A Li/composite electrolyte/LFP solid-state cell provided a discharge capacity of ca. 140 mAh/g and suitable cycling stability at 55 degrees C after 40 cycles. This study clearly suggests that this type of amorphous polyester-based polymers can be applied in polymer-in-ceramic composite electrolytes for the realization of advanced all-solid-state lithium-ion batteries.
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| 35. |
- Park, Bumjun, et al.
(author)
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Ion Coordination and Transport in Magnesium Polymer Electrolytes Based on Polyester-co-Polycarbonate
- 2021
-
In: Energy Material Advances. - : American Association for the Advancement of Science (AAAS). - 2692-7640. ; 2021, s. 1-14
-
Journal article (peer-reviewed)abstract
- Magnesium-ion-conducting solid polymer electrolytes have been studied for rechargeable Mg metal batteries, one of the beyond-Li-ion systems. In this paper, magnesium polymer electrolytes with magnesium bis(trifluoromethane)sulfonimide (Mg(TFSI)2) salt in poly(ε-caprolactone-co-trimethylene carbonate) (PCL-PTMC) were investigated and compared with the poly(ethylene oxide) (PEO) analogs. Both thermal properties and vibrational spectroscopy indicated that the total ion conduction in the PEO electrolytes was dominated by the anion conduction due to strong polymer coordination with fully dissociated Mg2+. On the other hand, in PCL-PTMC electrolytes, there is relatively weaker polymer–cation coordination and increased anion–cation coordination. Sporadic Mg- and F-rich particles were observed on the Cu electrodes after polarization tests in Cu|Mg cells with PCL-PTMC electrolyte, suggesting that Mg was conducted in the ion complex form (MgxTFSIy) to the copper working electrode to be reduced which resulted in anion decomposition. However, the Mg metal deposition/stripping was not favorable with either Mg(TFSI)2 in PCL-PTMC or Mg(TFSI)2 in PEO, which inhibited quantitative analysis of magnesium conduction. A remaining challenge is thus to accurately assess transport numbers in these systems.
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| 36. |
- Phadatare, Manisha R., et al.
(author)
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Silicon-Nanographite Aerogel-Based Anodes for High Performance Lithium Ion Batteries
- 2019
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Journal article (peer-reviewed)abstract
- To increase the energy storage density of lithium-ion batteries, silicon anodes have been explored due to their high capacity. One of the main challenges for silicon anodes are large volume variations during the lithiation processes. Recently, several high-performance schemes have been demonstrated with increased life cycles utilizing nanomaterials such as nanoparticles, nanowires, and thin films. However, a method that allows the large-scale production of silicon anodes remains to be demonstrated. Herein, we address this question by suggesting new scalable nanomaterial-based anodes. Si nanoparticles were grown on nanographite flakes by aerogel fabrication route from Si powder and nanographite mixture using polyvinyl alcohol (PVA). This silicon-nanographite aerogel electrode has stable specific capacity even at high current rates and exhibit good cyclic stability. The specific capacity is 455 mAh g−1 for 200th cycles with a coulombic efficiency of 97% at a current density 100 mA g−1.
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| 37. |
- Salian, Girish D., et al.
(author)
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Investigation of Water-Soluble Binders for LiNi0.5Mn1.5O4-Based Full Cells
- 2022
-
In: ChemistryOpen. - : John Wiley & Sons. - 2191-1363. ; 11:6
-
Journal article (peer-reviewed)abstract
- Two water-soluble binders of carboxymethyl cellulose (CMC) and sodium alginate (SA) have been studied in comparison with N-methylpyrrolidone-soluble poly(vinylidene difluoride-co-hexafluoropropylene) (PVdF-HFP) to understand their effect on the electrochemical performance of a high-voltage lithium nickel manganese oxide (LNMO) cathode. The electrochemical performance has been investigated in full cells using a Li4Ti5O12 (LTO) anode. At room temperature, LNMO cathodes prepared with aqueous binders provided a similar electrochemical performance as those prepared with PVdF-HFP. However, at 55 degrees C, the full cells containing LNMO with the aqueous binders showed higher cycling stability. The results are supported by intermittent current interruption resistance measurements, wherein the electrodes with SA showed lower resistance. The surface layer formed on the electrodes after cycling has been characterized by X-ray photoelectron spectroscopy. The amount of transition metal dissolutions was comparable for all three cells. However, the amount of hydrogen fluoride (HF) content in the electrolyte cycled at 55 degrees C is lower in the cell with the SA binder. These results suggest that use of water-soluble binders could provide a practical and more sustainable alternative to PVdF-based binders for the fabrication of LNMO electrodes.
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| 38. |
- Sångeland, Christofer, et al.
(author)
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Dissecting the solid polymer electrolyte–electrode interface in the vicinity of electrochemical stability limits
- 2022
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:25, s. 28716-28728
-
Journal article (peer-reviewed)abstract
- Proper understanding of solid polymer electrolyte–electrode interfacial layer formation and its implications on cell performance is a vital step toward realizing practical solid-state lithium-ion batteries. At the same time, probing these solid–solid interfaces is extremely challenging as they are buried within the electrochemical system, thereby efficiently evading exposure to surface-sensitive spectroscopic methods. Still, the probing of interfacial degradation layers is essential to render an accurate picture of the behavior of these materials in the vicinity of their electrochemical stability limits and to complement the incomplete picture gained from electrochemical assessments. In this work, we address this issue in conjunction with presenting a thorough evaluation of the electrochemical stability window of the solid polymer electrolyte poly(ε-caprolactone):lithium bis(trifluoromethanesulfonyl)imide (PCL:LiTFSI). According to staircase voltammetry, the electrochemical stability window of the polyester-based electrolyte was found to span from 1.5 to 4 V vs Li+/Li. Subsequent decomposition of PCL:LiTFSI outside of the stability window led to a buildup of carbonaceous, lithium oxide and salt-derived species at the electrode–electrolyte interface, identified using postmortem spectroscopic analysis. These species formed highly resistive interphase layers, acting as major bottlenecks in the SPE system. Resistance and thickness values of these layers at different potentials were then estimated based on the impedance response between a lithium iron phosphate reference electrode and carbon-coated working electrodes. Importantly, it is only through the combination of electrochemistry and photoelectron spectroscopy that the full extent of the electrochemical performance at the limits of electrochemical stability can be reliably and accurately determined.
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| 39. |
- Weng, Yi-Chen, et al.
(author)
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Spatially and Chemically Resolved Degradation of Fluorine-Free Electrolyte on Silicon/Graphite Surfaces
- 2024
-
In: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 171:6
-
Journal article (peer-reviewed)abstract
- Implementation of fluorine-free electrolytes that are safer and more sustainable than the state-of-the-art highly fluorinated electrolytes requires a thorough understanding of the interphase formation process. This work investigates the effects of LiPF6- and lithium bis(oxalato)borate (LiBOB)-based electrolytes on the electrochemical performance and surface chemistry of graphite, silicon, and silicon-graphite composite electrodes. The LiBOB-based electrolyte degrades more with the presence of silicon in the electrode, and tends to form a thicker solid electrolyte interphase (SEI) layer compared to the LiPF6-based electrolyte. Different degradation distributions were also found in the graphite-silicon composite electrode: The LiPF6 degradation products tend to form on silicon, while the LiBOB degradation products preferentially form on carbon species. These results provide insights into the relationship between electrolytes and electrodes in terms of electrochemical performance, as well as SEI composition and morphology.
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| 40. |
- Xu, Chao, 1988-, et al.
(author)
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Unraveling and Mitigating the Storage Instability of Fluoroethylene Carbonate-Containing LiPF6 Electrolytes To Stabilize Lithium Metal Anodes for High-Temperature Rechargeable Batteries
- 2019
-
In: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 2:7, s. 4925-4935
-
Journal article (peer-reviewed)abstract
- Implementing Li metal anodes provides the potential of substantially boosting the energy density of current Li-ion battery technology. However, it suffers greatly from fast performance fading largely due to substantial volume change during cycling and the poor stability of the solid electrolyte interphase (SEI). Fluoroethylene carbonate (FEC) is widely acknowledged as an effective electrolyte additive for improving the cycling performance of batteries consisting of electrode materials that undergo large volume changes during cycling such as Li metal. In this study, we report that while FEC can form a robust SEI on the electrode, it also deteriorates the shelf life of electrolytes containing LiPF6. The degradation mechanism of LiPF6 in FEC solutions is unraveled by liquid-and solid-state NMR. Specifically, traces of water residues induce the hydrolysis of LiPF6, releasing HF and PF5 which further trigger ring-opening of FEC and its subsequent polymerization. These reactions are significantly accelerated at elevated temperatures leading to the formation of a three-dimensional fluorinated solid polymer network. Moisture scavenger additives, such as lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI), can delay the degradation reaction as well as improve the cycling stability of LiNi1/3Mn1/3Co1/3O2/Li metal batteries at 55 degrees C. This work highlights the poor shelf life of electrolytes containing FEC in combination with LiPF6 and thereby the great importance of developing proper storage methods as well as optimizing the content of FEC in practical cells.
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| 41. |
- Åkerlund, Lisa, 1986-, et al.
(author)
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A crosslinked conducting polymer with well-defined proton trap function for reversible proton cycling in aprotic environments
- 2020
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 8:24, s. 12114-12123
-
Journal article (peer-reviewed)abstract
- In this paper, a well-defined proton trap material containing a hydroquinone unit flanked by two pyridine proton acceptors is presented. In combination with a terthiophene trimer, based on 3,4-ethylenedioxythiophene and 3,4-propylenedioxythiophene units, a conducting material with reversible redox properties is obtained. We apply post-deposition polymerization of the functionalized terthiophene trimer to provide a conducting polymer, which allows investigation of the electrochemical properties of the proton trap material. In situ studies concerning conductance measurements, mass uptake, electronic transitions and bonding vibrations indicate stable internal proton cycling between the hydroquinone and the pyridine functionality without affecting the conductivity or the doping process. The theoretical capacity of 42 mA h g−1, based on the pendant group redox conversion, can be achieved in a three electrode setup by potential step charging (25 s) at 0.5 V vs. Fc0/+ with subsequent discharging at 2C (0.5–0 V vs. Fc0/+). The total theoretical capacity available, including the contribution from the backbone, is 84 mA h g−1 and coin cell batteries with the conducting redox polymer as cathode material (without any additive) vs. lithium foil as anode showed a discharge capacity of 81 mA h g−1 (97% of the theoretical capacity) already from the first cycle (2.5–3.8 V vs. Li0/+ at 2C). The capacity was maintained during prolonged cycling and showed a capacity retention of 99% after 100 cycles and 98% after 200 cycles indicating high stability of this organic cathode material when applied in a battery configuration.
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| 42. |
- Åkerlund, Lisa, 1986-, et al.
(author)
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In situ Investigations of a Proton Trap Material: A PEDOT-Based Copolymer with Hydroquinone and Pyridine Side Groups Having Robust Cyclability in Organic Electrolytes and Ionic Liquids
- 2019
-
In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 2:6, s. 4486-4495
-
Journal article (peer-reviewed)abstract
- A conducting redox polymer based on PEDOT with hydroquinone and pyridine pendant groups is reported and characterized as a proton trap material. The proton trap functionality, where protons are transferred from the hydroquinone to the pyridine sites, allows for utilization of the inherently high redox potential of the hydroquinone pendant group (3.3 V versus Li0/+) and sustains this reaction by trapping the protons within the polymer, resulting in proton cycling in an aprotic electrolyte. By disconnecting the cycling ion of the anode from the cathode, the choice of anode and electrolyte can be extensively varied and the proton trap copolymer can be used as cathode material for all-organic or metal-organic batteries. In this study, a stable and nonvolatile ionic liquid was introduced as electrolyte media, leading to enhanced cycling stability of the proton trap compared to cycling in acetonitrile, which is attributed to the decreased basicity of the solvent. Various in situ methods allowed for in-depth characterization of the polymer’s properties based on its electronic transitions (UV–vis), temperature-dependent conductivity (bipotentiostatic CV-measurements), and mass change (EQCM) during the redox cycle. Furthermore, FTIR combined with quantum chemical calculations indicate that hydrogen bonding interactions are present for all the hydroquinone and quinone states, explaining the reversible behavior of the copolymer in aprotic electrolytes, both in three-electrode setup and in battery devices. These results demonstrate the proton trap concept as an interesting strategy for high potential organic energy storage materials.
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| 43. |
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