| 1. |
- Ekdahl, Ylva, et al.
(författare)
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A-to-I editing of microRNAs in the mammalian brain increases during development
- 2012
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 22:8, s. 1477-1487
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Tidskriftsartikel (refereegranskat)abstract
- Adenosine-to-inosine (A-to-I) RNA editing targets double-stranded RNA stem-loop structures in the mammalian brain. It has previously been shown that miRNAs are substrates for A-to-I editing. For the first time, we show that for several definitions of edited miRNA, the level of editing increases with development, thereby indicating a regulatory role for editing during brain maturation. We use high-throughput RNA sequencing to determine editing levels in mature miRNA, from the mouse transcriptome, and compare these with the levels of editing in pri-miRNA. We show that increased editing during development gradually changes the proportions of the two miR-376a isoforms, which previously have been shown to have different targets. Several other miRNAs that also are edited in the seed sequence show an increased level of editing through development. By comparing editing of pri-miRNA with editing and expression of the corresponding mature miRNA, we also show an editing-induced developmental regulation of miRNA expression. Taken together, our results imply that RNA editing influences the miRNA repertoire during brain maturation.
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| 2. |
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| 3. |
- Behm, Mårten, et al.
(författare)
-
Electrochemical production of polysulfides and sodium hydroxide from while liquor .2. Electrolysis in a laboratory scale flow cell
- 1997
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Ingår i: Journal of Applied Electrochemistry. - 0021-891X .- 1572-8838. ; 27:5, s. 519-528
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical production of polysulfide-containing white liquor and pure sodium hydroxide solution was investigated at 90 degrees C in a laboratory scale flow cell. A mixed iridium-tantalum oxide coated titanium electrode was used as the anode and the two electrolyte compartments were separated by a cation-exchange membrane. The process was demonstrated at current densities up to 5 kA m(-2), resulting in high current efficiencies for both products. The previously reported autocatalytic effect of polysulfide ions was confirmed, and its technical implications on the use of three-dimensional electrodes were demonstrated and discussed. The current efficiency was found to depend strongly on the degree of conversion of sulfur(-II) to sulfur(0). The anode material showed favourable properties, with respect to activity and selectivity, but suffered from limited durability.
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| 4. |
- Behm, Mårten, et al.
(författare)
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Electrochemical production of polysulfides and sodium hydroxide from white liquor .1. Experiments with rotating disc and ring-disc electrodes
- 1997
-
Ingår i: Journal of Applied Electrochemistry. - 0021-891X .- 1572-8838. ; 27:5, s. 507-518
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochemical oxidation of white liquor in a membrane cell is a process of great potential for the pulp and paper industry. The process produces polysulfide-containing white liquor in the anode chamber, and pure sodium hydroxide solution in the cathode chamber. The anode reaction has been investigated using cyclic voltammetry at temperatures between 25 and 90 degrees C on rotating disc and ring-disc electrodes. It was further investigated using chronoamperometry on rotating disc electrodes at 90 degrees C. The experiments, which were mainly run in dilute alkaline sulfide solutions, using platinum electrodes, show that the electrochemical production of polysulfide ions, at lower anode potentials (-0.1 to +0.1 V vs SCE), proceeds via formation of elemental sulfur on the electrode surface. The sulfur is dissolved by hydrosulfide and polysulfide ions producing (longer-chain) polysulfide ions. The rate of dissolution, and thus the overall reaction rate, increases strongly with temperature. Polysulfide ions have an autocatalytic effect on the anode reaction due to their ability to dissolve adsorbed sulfur. At higher anode potentials (greater than or equal to 0.2 V vs SCE), a change of reaction mechanism is observed. In this region the reaction rate depends on electrode potential and is not catalysed by polysulfide ions.
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| 5. |
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| 6. |
- Behm, Mårten, et al.
(författare)
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Influence of structure and composition upon performance of tin phosphate based negative electrodes for lithium batteries
- 2002
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 47:11, s. 1727-1738
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Tidskriftsartikel (refereegranskat)abstract
- Tin oxide and amorphous tin borophosphates have recently received significant attention as possible new negative electrode materials for lithium batteries. In this study. we have carefully investigated a number of different well-characterised tin phosphates as electrodes in Li-ion cells, in order to better understand the mode of operation of these materials and how their performance is related to structure and composition. The materials that were investigated were crystalline cubic and layered SnP2O7, LiSn2(PO4)(3). Sn2P2O7, and Sn-3(PO4)(2). and amorphous Sn2BPO6. Cubic SnP2O7 showed the best performance with a reversible specific charge capacity of > 360 mA h g(-1) and a capacity retention of 96% over 50 cycles when cycled between 0.02 and 1.2 V versus Li-m. The three Sn(IV) materials showed lower initial reversible capacity but better capacity retention than the three Sn(II) materials in the study. Their higher proportion of inert matrix material can partly explain this. However. cubic SnP2O7 cycled significantly better than its layered polymorph. which shows that the structure of the starting material is also of great importance. Another important conclusion drawn front the results is that it is not necessary for the starting material to be amorphous, or if crystalline, to have small grain size, to cycle well. The three pyrophosphates all show an initial reduction capacity that corresponds to around 2 Li per P2O74- unit more than is predicted by theory. This might be explained by reductive break-up of the P 0 P bond.
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| 7. |
- Behm, Mårten, et al.
(författare)
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Nickel as anode material for the electrochemical production of polysulfides in white liquor
- 1999
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Ingår i: Journal of New Materials for Electrochemical Systems. - 1480-2422. ; 2:1, s. 11-18
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Tidskriftsartikel (refereegranskat)abstract
- This paper is concerned with new anode materials for the electrochemical oxidation of white liquor. This electrosynthesis process is run in a membrane cell where polysulfide ions are produced in the white liquor of the anode chamber, while a pure sodium hydroxide solution is generated in the cathode chamber: If the noble metal oxide coated anodes that were used in a previous investigation could be successfully replaced by nickel, important reductions in investment costs would be possible. The stability and catalytic activity of nickel as anode material were investigated using cyclic voltammetry and chronoamperometry on rotating disc electrodes, combined with surface analysis. Furthermore, porous nickel was tested in a flow cell, with galvanostatic electrolysis. The results show that nickel has good activity for sulfide oxidation, but a nickel oxide/sulfide surface layer is formed which deactivates the electrode at E greater than or equal to -0.2 V, probably due to the increasing proportion of poorly conducting Ni(II) oxide. Carbon precipitation, and peeling of a thin film of the metal were observed with SEM. High current efficiency and an overpotential of less than 0.2 V were obtained with a porous nickel electrode at a geometric current density of 3 kA m(-2). Corrosion did not appear to be a problem, and nickel should also be suitable as substrate material for more active anode coatings.
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| 8. |
- Bessman, Alexander, et al.
(författare)
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Investigating the aging effect of current ripple on lithium-ion cells
- 2015
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Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-6737. - 9781607685395 ; , s. 101-106
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Konferensbidrag (refereegranskat)abstract
- We have built an experimental setup which exposes twelve cells to a well-defined ripple current. It consists of a system for cycling high capacity cells in parallel with a triangular current waveform superimposed on top of the direct current. The frequency of the waveform is variable up to 50 Hz, and the sum of the DC and AC components can have a magnitude of -40 A to 40 A. Current is measured over a 500 μω shunt resistor. The voltage and current of each cell is read simultaneously at a sample rate up to 4 MS/s, allowing for precise impedance measurements even for high frequency harmonics. The cells are cycled at 40 °C. The experiment has been designed to eliminate indirect effects of the AC harmonics as far as possible. This system is being used to test whether or not AC harmonics affect Li-ion aging.
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| 9. |
- Brown, Shelley, et al.
(författare)
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Characterisation and modelling of a high-power density lithium-ion positive electrode for HEV application
- 2004
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Konferensbidrag (refereegranskat)abstract
- In this study, the impedance response of a porous electrode based on LiNi0.8Co0.15Al0.05O2 was investigated using an impedance model including the following features: Butler-Volmer kinetics; double layer capacitance; solid phase concentration and potential gradients; electrolyte phase concentration and potential according to the concentrated electrolyte theory; particle size distribution; and an empirical relation between equilibrium potential and state of charge. The model was evaluated by fitting it to experimental results using different electrolytes and states of charge. In addition, the characteristic parameters for the electrode were obtained from the fitting results.
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| 10. |
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| 11. |
- Chai, Xin-Sheng, et al.
(författare)
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Spectrophotometric in-line monitoring of the electrochemical production of polysulfides using an ATR-probe
- 1998
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Ingår i: Process control and quality. - : Brill. - 0924-3089 .- 1568-5667. ; 11:2, s. 153-159
-
Tidskriftsartikel (refereegranskat)abstract
- With an ATR-probe For the UV-vis range it is possible to apply spectrophotometry to very concentrated process liquors without dilution. In this paper the application of a new ATR-probe to the monitoring of sulfur species during an electrochemical process for production of polysulfides is presented. In this system, the temperature and the total salt concentration are relatively constant. A linear relation exists between the ATR-probe response and the concentration of adsorbing species. Therefore, the process can be followed by simple monitoring of a few wavelengths. The ATR-probe was easily implemented and showed no signs of deterioration in the hot strongly alkaline medium. Temperature has a significant effect on measurement with ATR-probes. Other factors that might also affect the measurements using an ATR-probe an briefly discussed.
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| 12. |
- Ciosek Högström, Katarzyna, 1984-, et al.
(författare)
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Impact of the flame retardant additive triphenyl phosphate (TPP) on the performance of graphite/LiFePO4 cells in high power applications
- 2014
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 256, s. 430-439
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents an extensive characterization of a standard Li-ion battery (LiB) electrolyte containing different concentrations of the flame retardant triphenyl phosphate (TPP) in the context of high power applications. Electrolyte characterization shows only a minor decrease in the electrolyte flammability for low TPP concentrations. The addition of TPP to the electrolyte leads to increased viscosity and decreased conductivity. The solvation of the lithium ion charge carriers seem to be directly affected by the TPP addition as evidenced by Raman spectroscopy and increased mass-transport resistivity. Graphite/LiFePO4 full cell tests show the energy efficiency to decrease with the addition of TPP. Specifically, diffusion resistivity is observed to be the main source of increased losses. Furthermore, TPP influences the interface chemistry on both the positive and the negative electrode. Higher concentrations of TPP lead to thicker interface layers on LiFePO4. Even though TPP is not electrochemically reduced on graphite, it does participate in SEI formation. TPP cannot be considered a suitable flame retardant for high power applications as there is only a minor impact of TPP on the flammability of the electrolyte for low concentrations of TPP, and a significant increase in polarization is observed for higher concentrations of TPP. (C) 2014 Elsevier B.V. All rights reserved.
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| 13. |
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| 14. |
- Ciosek, Katarzyna, et al.
(författare)
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Energy storage activities in the Swedish hybrid vehicle centre
- 2009
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Ingår i: World Electric Vehicle Journal. - : MDPI AG. - 2032-6653. ; 3:4, s. 858-862, s. 2850-2854
-
Tidskriftsartikel (refereegranskat)abstract
- Significant efforts are put worldwide on developing new concepts for vehicle propulsion with the hybrid electric vehicle (HEV) being a prominent example. Hybrid technology is clearly a strategic future activity for automotive industries and in response to the rapid development in the area; the Swedish Hybrid Vehicle Centre (SHC) was formed in 2007 to join forces between Swedish industry and academia in the field. The centre emphasizes a holistic view to meet the environmental and societal needs with new technological solutions. The research within SHC is currently divided into three different themes whereof we here describe the Energy Storage theme with emphasis on the activities carried out at the involved universities in the current main project areas: Cell Properties, Electrode Materials and Electrolyte Additives. Examples are given on how these projects attacks the problems at hand separately, but also how we create synergy effects between the projects. As an example cell modelling is performed given a specific chemistry and cycling scheme, the same parameters are used for electrochemical experiments which provide macroscopic data that are connected with molecular level actions in the electrodes, the electrolyte, and the interfaces. All this is done using our base-line chemistry and a subsequent route is to investigate the role of different additives to overcome the limitations that are observed.
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| 15. |
- Danielsson, Carl-Ola, et al.
(författare)
-
A Model for the Enhanced Water Dissociation On Monopolar Membranes
- 2009
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 54:11, s. 2983-2991
-
Tidskriftsartikel (refereegranskat)abstract
- A model for the enhanced water dissociation that takes place at the solution/membrane interface in electromembrane processes is presented. The mechanisms behind the enhanced water dissociation are poorly understood and therefore a semi-empirical approach is suggested. The enhanced water dissociation is introduced as a heterogeneous surface reaction similar to the well established Butler–Volmer law for electrode reactions. In the model there are two parameters that need to be determined through experiments. A 1D diffusion boundary layer problem is presented and solved in order to show that a sufficient rate of water dissociation can be obtained with the model. The advantage of the presented model is that it can easily be incorporated into simulations of electromembrane processes such as electrodialysis, electrodeionization and electropermutation. The influence of the enhanced water dissociation on these processes can then be studied.
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| 16. |
- Danielsson, Carl-Ola
(författare)
-
Electropermutation assisted by ion-exchange textile : removal of nitrate from drinking water
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increased levels of nitrate in ground water have made many wells unsuitable as sources for drinking water. In this thesis an ion-exchang eassisted electromembrane process, suitable for nitrate removal, is investigated both theoretically and experimentally. An ion-exchange textile material is introduced as a conducting spacer in the feed compartment of an electropermutation cell. The sheet shaped structure of the textile makes it easy to incorporate into the cell. High permeability and fast ion-exchange kinetics, compared to ion-exchange resins, are other attractive features of the ion-exchange textile. A steady-state model based on the conservation of the ionic species is developed. The governing equations on the microscopic level are volume averaged to give macro-homogeneous equations. The model equations are analyzed and relevant simplifications are motivated and introduced. Dimensionless parameters governing the continuous electropermutation process are identified and their influence on the process are discussed. The mathematical model can be used as a tool when optimising the process parameters and designing equipment. An experimental study that aimed to show the positive influence of using the ion-exchange textile in the feed compartment of an continuous electropermutation process is presented. The incorporation of the ion-exchange textile significantly improves the nitrate removal rate at the same time as the power consumption is decreased. A superficial solution of sodium nitrate with a initial nitrate concentration of 105 ppm was treated. A product stream with less than 20 ppm nitrate could be obtained, in a single pass mode of operation. Its concluded from these experiments that continuous electropermutation using ion-exchange textile provides an interesting alternative for nitrate removal, in drinking water production. The predictions of the mathematical model are compared with experimental results and a good agreement is obtained. Enhanced water dissociation is known to take place at the surface of ion-exchange membranes in electromembrane processes operated above the limiting current density. A model for this enhanced water dissociation in presented in the thesis. The model makes it possible to incorporate the effect of water dissociation as a heterogeneous surface reaction. Results from simulations of electropermutation with and without ion-exchange textile incorporated are presented. The influence of the water dissociation is investigated with the developed model.
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| 17. |
- Danielsson, Carl-Ola, et al.
(författare)
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Modeling Continuous Electropermutation with Effects of Water Dissociation Included
- 2010
-
Ingår i: AIChE Journal. - : Wiley. - 0001-1541 .- 1547-5905. ; 56:9, s. 2455-2467
-
Tidskriftsartikel (refereegranskat)abstract
- The repeating unit consisting of a cell pair of one concentrate and one feed compartment of an electropermutation stack is modeled. Both the feed and the concentrate compartments are filled with an ion-exchange textile material. Enhanced water dissociation taking place at the surface of the membrane is included in the model as a hetrogeneous surface reaction. Results from simulations of nitrate removal for drinking water production are presented and comparisons with previous experimental results are made. The influence of both conductive and inert textile spacers on the process is investigated via simulations
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| 18. |
- Danielsson, Carl-Ola, et al.
(författare)
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Nitrate Removal by Continuous Electropermutation Using Ion-Exchange Textile : II. Experimental Investigation
- 2006
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 153:4, s. D62-D67
-
Tidskriftsartikel (refereegranskat)abstract
- Water with nitrate concentrations above 100 ppm has been treated with continuous electropermutation which partially substitutes the nitrate with chloride. The performance of a textile anion exchanger as conducting spacer in the feed compartment of an electropermutation cell was investigated. Experiments with and without textile are compared and the influence of the textile is discussed. The process could, using the textile, successfully treat feed water with 105 ppm nitrate to produce a water with less than 25 ppm nitrate. The importance of establishing a good contact between the membranes and the textile spacer was pointed out. The experimental results were compared to model predictions and a good agreement was found.
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| 19. |
- Danielsson, Carl-Ola, et al.
(författare)
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Nitrate Removal by Continuous Electropermutation Using Ion-Exchange Textile : I. Modeling
- 2006
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 153:4, s. D51-D61
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a steady-state model of the feed compartment of an electropermutation cell, used for nitrate removal, with ion exchange textiles incorporated as a conducting spacer. In the model the ion-exchange textile is treated as a porous medium and volume averaging is applied to obtain a macrohomogeneous two-phase model. The ion-exchange between the two phases is modeled assuming that the rate-determining step is the mass-transfer resistance on the liquid side of the phase interface. Analysis of the model equations reveals appropriate simplifications. The influence of the governing dimensionless numbers is investigated through simulations based on the model.
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| 20. |
- Danielsson, Lars-Göran, et al.
(författare)
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UV characterization of sulphide-polysulphide solutions and its application for process monitoring in the electrochemical production of polysulphides
- 1996
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 22:6, s. J187-J191
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Tidskriftsartikel (refereegranskat)abstract
- The UV spectral characteristics of some sulphur species of relevance for the electrochemical production of polysulphides have been studies. It was found that an isosbestic point exists in the hydrogen sulphide ion-polysulphide solution. The absorption at this point (249 nm) is proportional to the total sulphur concentration in the solution. The investigation also shows that the spectrum of a polysulphide solution can be regarded simply as the sum of contributions from charges hydrogen sulphide ion and zero-valent sulphur in polysulphides although a complicated equilibrium distribution of different species exists in the polysulphide solution. The spectrum provides enough information for the measurement of these forms of sulphur. Based on spectrophotometric measurements, a simple monitoring for changed hydrogen sulphide ion and polysulphide excess sulphur in the process liquor can be realized.
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| 21. |
- Das, B, et al.
(författare)
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High performance metal nitrides, MN (M = Cr, Co) nanoparticles for non-aqueous hybrid supercapacitors
- 2015
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 26:3, s. 783-788
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Tidskriftsartikel (refereegranskat)abstract
- In this study, metal nitrides MN (M = Cr, Co) nanoparticles of particle size similar to 20-30 nm have been prepared under NH3 + N-2 atmosphere at relatively low temperature. The Cr-urea complex was directly converted to CrN with an intermediate formation of Cr2O3, whereas CoN was prepared from Co3O4. These compounds were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) techniques. The electrochemical properties were evaluated by galvanostatic cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical performance of the resultant MN nanoparticles showed that they can be used as potential electrode materials for non-aqueous hybrid electrochemical supercapacitors (HESCs). The MN/AC showed high specific capacitance of 75 and 37 F g (1) for M = Cr, Co, respectively when cycled at 30 mA g (1) in non-aqueous electrolyte.
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| 22. |
- Dermenci, K.B., et al.
(författare)
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Effect of cathode slurry composition on the electrochemical properties of Li-ion batteries
- 2015
-
Ingår i: ECS Transactions. - 1938-5862 .- 1938-6737. ; 66:9, s. 285-293
-
Tidskriftsartikel (refereegranskat)abstract
- The performance difference between commercial and laboratory scale cells remains a problem to be solved. Different way of battery electrode preparation is considered to be the main reason underlying various battery performance. In this work, the effect of slurry composition on electrochemical properties of Li-ion batteries is reported. Slurry preparation with various compositions of LiFePO4 active material (76-88%), PVdF binder (6-12%) and Super P Carbon conductive additive (6-12%) has been studied. Charge-discharge curves and capacity fade of electrodes are also investigated. Selected electrodes were pressed in order to see the effect of pressing on the final performance. Results showed that varying PVdF and carbon content mainly effects charge-discharge characteristics. For unpressed samples, higher amount of PVdF and carbon could result higher maximum specific capacity and lower internal resistance during lithiation and delithiation of positive electrode. Pressing reduces the distance between slurry particles, which enhances the conductivity of the prepared cell.
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| 23. |
- Dolidze, T. D., et al.
(författare)
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Two-equivalent electrochemical reduction of a cyano-complex Tl-III(CN)(2) (+) and the novel di-nuclear compound (CN)(5)Pt-II-Tl-III (0)
- 2005
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 50:22, s. 4444-4450
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Tidskriftsartikel (refereegranskat)abstract
- Extending our recent insights in two-electron transfer microscopic mechanisms for a Tl-III/Tl-I redox system, the electrochemical response of glassy carbon electrode in acidified solutions of Tl-III (ClO4)(3) containing different concentrations of sodium cyanide has been extensively studied for the first time by use of cyclic voltammetry and the CVSIM curve simulation PC program. The complex [Tl-III(CN)(2)](+) has been thoroughly identified electrochemically and shown to display a single welldefined reduction wave (which has no anodic counterpart), ascribed to the two-equivalent process yielding [Tl-I(aq)](+). This behavior is similar to that of [Tl-III (aq)](3+) ion in the absence of sodium cyanide, disclosed in the previous work, and is compatible with the quasi-simultaneous yet sequential two-electron transfer pattern (with two reduction waves merged in one), implying the rate-determining first electron transfer step (resulting in the formation of a covalently interacting di-thallium complex as a metastable intermediate), and the fast second electron transfer step. Some preliminary studies of the two-equivalent reduction of directly metal-metal bonded stable compound [(CN)(5)Pt-II-Tl-III](0) has been also performed displaying two reduction waves compatible with a true sequential pattern.
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| 24. |
- Eric, Jacques, et al.
(författare)
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Impact of the mechanical loading on the electrochemical capacity of carbon fibres for use in energy storage composite materials
- 2011
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Reducing system mass for improvements in system performance has become a priority for future applications such as mobile phones or electric vehicles which require load bearing components and electrical energy storage devices. Structure and energy storage are usually subsystems with the highest mass contributions but energy storage components are structurally parasitic. A novel solution is a multifunctional lightweight design combining these two functions in a single material entity able to simultaneously bear mechanical loads as a carbon fiber composite component and store electrochemical energy as a lithium-ion battery.
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| 25. |
- Giordano, Giuseppe, 1985, et al.
(författare)
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Model-Based Lithium-Ion Battery Resistance Estimation From Electric Vehicle Operating Data
- 2018
-
Ingår i: IEEE Transactions on Vehicular Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9545 .- 1939-9359. ; 67:5, s. 3720-3728
-
Tidskriftsartikel (refereegranskat)abstract
- State-of-health estimates of batteries are essential for onboard electric vehicles in order to provide safe, reliable, and cost-effective battery operation. This paper suggests a method to estimate the 10-s discharge resistance, which is an established battery figure of merit from laboratory testing, without performing the laboratory test. Instead, a state-of-health estimate of batteries is obtained using data directly from their operational use, e.g., onboard electric vehicles. It is shown that simple dynamical battery models, based on a current input and a voltage output, with model parameters dependent on temperature and state of charge, can be derived using AutoRegressive with eXogenous input models, whose order can be adjusted to describe the complex battery behavior. Then, the 10-s discharge resistance can be conveniently computed from the identified model parameters. Moreover, the uncertainty of the estimated resistance values is provided by the method. The suggested method is validated with usage data from emulated electric vehicle operation of an automotive lithium-ion battery cell. The resistance values are estimated accurately for a state-of-charge and temperature range spanning typical electric vehicle operating conditions. The identification of the model parameters and the resistance computation are very fast, rendering the method suitable for onboard application.
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| 26. |
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| 27. |
- Hellqvist Kjell, Maria, et al.
(författare)
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Comparing aging of graphite/LiFePO4 cells at 22 degrees C and 55 degrees C - Electrochemical and photoelectron spectroscopy studies
- 2013
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 243, s. 290-298
-
Tidskriftsartikel (refereegranskat)abstract
- Accelerated aging at elevated temperature is commonly used to test lithium-ion battery lifetime, but the effect of an elevated temperature is still not well understood. If aging at elevated temperature would only be faster, but in all other respects equivalent to aging at ambient temperature, cells aged to end-of-life (EOL) at different temperatures would be very similar. The present study compares graphite/LiFePO4-based cells either cycle- or calendar-aged to EOL at 22 degrees C and 55 degrees C. Cells cycled at the two temperatures show differences in electrochemical impedance spectra as well as in X-ray photoelectron spectroscopy (XPS) spectra. These results show that lithium-ion cell aging is a complex set of processes. At elevated temperature, the aging is accelerated in process-specific ways. Furthermore, the XPS results of cycle-aged samples indicate increased deposition of oxygenated LiPF6 decomposition products in both the negative and positive electrode/electrolyte interfaces. The decomposition seems more pronounced at elevated temperature, and largely accelerated by cycling, which could contribute to the observed cell impedance increase.
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| 28. |
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| 29. |
- Hellqvist Kjell, Maria, et al.
(författare)
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Electrochemical characterization of lithium intercalation processes of PAN-based carbon fibers in a microelectrode system
- 2013
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 160:9, s. A1473-A1481
-
Tidskriftsartikel (refereegranskat)abstract
- A full electrochemical investigation of the lithium intercalation processes in a commercially available PAN-based carbon fiber, Toho Tenax IMS65 (unsized and sized) primarily intended to be used in structural lithium-ion batteries, has been performed. In order to extract the electrochemical properties, a specially designed microelectrode system consisting of a single fiber working electrode, lithium-foil counter electrode and well-characterized battery materials were utilized. The properties, for 5 to 100% state-of-charge (SOC), were mainly determined from electrochemical impedance spectroscopy (EIS) measurements by fitting of a physics-based model, and electronic conductivity examination. The study shows excellent mass transport and kinetic properties, especially at high SOCs for this specific carbon fiber compared to other negative electrode materials. Some electrochemical parameters vary depending on sizing, but are too small to affect the actual electrochemical performance. A strong SOC dependence is shown for most electrochemical properties, including the electronic conductivity.
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| 30. |
- Hellqvist Kjell, Maria, et al.
(författare)
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PAN-based carbon fiber negative electrodes for structural lithium-ion batteries
- 2011
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society Inc.. - 0013-4651 .- 1945-7111. ; 158:12, s. A1455-A1460
-
Tidskriftsartikel (refereegranskat)abstract
- Several grades of commercially-available polyacrylonitrile (PAN)-based carbon fibers have been studied for structural lithium-ion batteries to understand how the sizing, different lithiation rates and number of fibers per tow affect the available reversible capacity, when used as both current collector and electrode, for use in structural batteries. The study shows that at moderate lithiation rates, 100 mA g-1, most of the carbon fibers display a reversible capacity close to or above 100 mAh g-1 after ten full cycles. For most of the fibers, removing the sizing increased the capacity to some extent. However, the main factor affecting the measured capacity was the lithiation rate. Decreasing the current by a tenth yielded an increase of capacity of around 100 for all the tested grades. From the measurements performed in this study it is evident that carbon fibers can be used as the active negative material and current collector in structural batteries.
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| 31. |
- Hellqvist Kjell, Maria, et al.
(författare)
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PAN-based carbon fibers for structural lithium-ion batteries
- 2012
-
Ingår i: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials. - : European Conference on Composite Materials, ECCM. - 9788888785332
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Konferensbidrag (refereegranskat)abstract
- Structural batteries have the potential to become an integrated part of the device, functioning as both a structural element and as energy storage by combining electrochemical properties and mechanical properties in the same material. In addition, an increase of power and energy density on a system level could be achieved. The electrochemical properties of seven different commercially available PAN-based carbon fibers have been investigated as negative electrodes for structural lithium-ion batteries. All of the tested fibers showed some ability to intercalate lithium ions. The performance varied significantly between the different grades of fiber. Fibers with intermediate modulus showed the most promising results.
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| 32. |
- Hellqvist Kjell, Maria
(författare)
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Performance of Conventional and Structural Lithium-Ion Batteries
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-ion batteries have, in recent years, experienced a rapid development from small everyday devices towards hybrid electric vehicle (HEV) applications. Due to this shift in application area, the battery performance andits degradation with time are becoming increasingly important issues to besolved.In this thesis, lithium-ion batteries are investigated with focus on lifetime performance of an existing battery chemistry, and development of electrodes for so-called structural batteries. The systems are evaluated by electrochemical methods, such as cycling and electrochemical impedance spectroscopy (EIS),combined with material characterization and modeling.Lifetime performance of mesocarbon microbeads (MCMB)/LiFePO4 cells was investigated to develop an understanding of how this technology tolerates and is influenced by different conditions, such as cycling, storage and temperature.The lifetime of the LiFePO4-based cells was found to be significantly reduced by cycling at elevated temperature, almost five times shorter compared to cycle-aged cells at ambient temperature. The calendar-aged cells also showed major signs of degradation at elevated temperatures. The overall cause of aging was electrolyte decomposition which resulted in loss of cyclable lithium, i.e. capacity fade, and impedance increase.Commercially available polyacrylonitrile (PAN)-based carbon fibers were investigated, both electrochemically and mechanically, to determine their suitability as negative electrodes in structural batteries. The electrochemical performance of carbon fibers was found to be excellent compared to other negative electrode materials, especially for single or well-separated fibers. The mechanical properties, measured as changes in the tensile properties, showed that the tensile stiffness was unaffected by lithium-ion intercalation and cycling. The ultimate tensile strength, however, showed a distinct variation with state-of-charge (SOC). Overall, carbon fibers are suitable for structural battery applications.
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| 33. |
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| 34. |
- Jacques, Eric, et al.
(författare)
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Effect of lithium-ion intercalation on the tensile properties of carbon fibres for energy storage composites
- 2012
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Ingår i: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials. - : European Conference on Composite Materials, ECCM. - 9788888785332
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Konferensbidrag (refereegranskat)abstract
- Carbon fibres can be used as structural electrodes because they have a high tensile properties-to-weight ratio and a graphitic structure which enables lithium-ion intercalation. Carbon fibre specimens were used as electrodes in laboratory cells. It was found that the fibre undergoes an ultimate tensile strength drop and an axial expansion which depend on the measured capacity. The results suggest that a tensile strain develops in the carbon fibre which is pre-stressed in tension and that this pre-stress correlates with the amount of lithiumions intercalated.
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| 35. |
- Jacques, Eric, et al.
(författare)
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Expansion of carbon fibres induced by lithium intercalation for structural electrode applications
- 2013
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 59, s. 246-254
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Tidskriftsartikel (refereegranskat)abstract
- Carbon fibres (CFs) can work as lightweight structural electrodes in CF-reinforced composites able to store energy as lithium (Li)-ion batteries. The CF has high stiffness and strength-to-weight ratios and a carbonaceous microstructure which enables Li intercalation. An innovative in situ technique for studying the longitudinal expansion of the CF and the relationship with the amount of intercalated Li is described in the present paper. The polyacrylonitrile-based CFs, T800H and unsized IMS65, were chosen for their electrochemical storage capacities. It was found that the CF expands during lithiation and contracts during delithiation. At the first electrochemical cycle, the expansion is partly irreversible which supports that the first-cycle capacity loss partly relates to Li trapped in the CF structure. For the following cycles, the capacity and the expansion are reversible. The expansion, which might relate to tensile stress, increases up to 1% as the measured capacity approaches the theoretical limit of 372 mAh/g for Li storage in graphite. Minor additional expansions due to the uneven distribution of intercalated Li in the CF structure were measured before and after lithiations. Using scanning electron microscope images the transverse expansion of fully lithiated CFs was estimated to about 10% of the cross-section area.
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| 36. |
- Jacques, Eric, et al.
(författare)
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Impact of electrochemical cycling on the tensile properties of carbon fibres for structural lithium-ion composite batteries
- 2012
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Ingår i: Composites Science And Technology. - : Elsevier. - 0266-3538 .- 1879-1050. ; 72:7, s. 792-798
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Tidskriftsartikel (refereegranskat)abstract
- Carbon fibres are particularly well suited for use in a multifunctional lightweight design of a structural composite material able to store energy as a lithium-ion battery. The fibres will in this case act as both a high performance structural reinforcement and one of the battery electrodes. However, the electrochemical cycling consists of insertions and extractions of lithium ions in the microstructure of carbon fibres and its impact on the mechanical performance is unknown. This study investigates the changes in the tensile properties of carbon fibres after they have been subjected to a number of electrochemical cycles. Consistent carbon fibre specimens were manufactured with polyacrylonitrile-based carbon fibres. Sized T800H and desized IMS65 were selected for their mechanical properties and electrochemical capacities. At the first lithiation the ultimate tensile strength of the fibres was reduced of about 20% but after the first delithiation some strength was recovered. The losses and recoveries of strength remained unchanged with the number of cycles as long as the cell capacity remained reversible. Losses in the cell capacity after 1000 cycles were measured together with smaller losses in the tensile strength of the lithiated fibres. These results show that electrochemical cycling does not degrade the tensile properties which seem to depend on the amount of lithium ions inserted and extracted. Both fibre grades exhibited the same trends of results. The tensile stiffness was not affected by the cycling. Field emission scanning electron microscope images taken after electrochemical cycling did not show any obvious damage of the outer surface of the fibres.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
- Kjell, Maria, et al.
(författare)
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Comparing aging of MCMB graphite/LiFePO4 cells at 22 °C and 55 °C – Electrochemical and photoelectron spectroscopy studies.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Accelerated aging at elevated temperature is commonly used to test lithium-ion battery lifetime, but the effect of an elevated temperature is still not well understood. If aging at elevated temperature would only be faster, but in all other respects equivalent to aging at ambient temperature, cells aged to end-of-life (EOL) at different temperatures would be very similar. The present study compares graphite/LiFePO4-based cells either cycle- or calendar-aged to EOL at 22 °C and 55 °C. Cells cycled at the two temperatures show differences in electrochemical impedance spectra as well as in X-ray photoelectron spectroscopy (XPS) spectra. These results show that lithium-ion cell aging is a complex set of processes. At elevated temperature, the aging is accelerated in process specific ways. Furthermore, the XPS results of cycle-aged samples indicate increased deposition of oxygenated LiPF6 decomposition products in both the negative and positive electrode/electrolyte interfaces. The decomposition seems more pronounced at elevated temperature, and largely accelerated by cycling, which could contribute to the observed cell impedance increase.
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| 41. |
- Klass, Verena, et al.
(författare)
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A support vector machine-based state-of-health estimation method for lithium-ion batteries under electric vehicle operation
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 270, s. 262-272
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Tidskriftsartikel (refereegranskat)abstract
- Capacity and resistance are state-of-health (SOH) indicators that are essential to monitor during the application of batteries on board electric vehicles. For state-of-health determination in laboratory environment, standard battery performance tests are established and well-functioning. Since standard performance tests are not available on-board a vehicle, we are developing a method where those standard tests are applied virtually to a support vector machine-based battery model. This data-driven model is solely based on variables available during ordinary electric vehicle (EV) operation such as battery current, voltage and temperature. This article contributes with a thorough experimental validation of this method, as well as the introduction of new features capacity estimation and temperature dependence. Typical EV battery usage data is generated and exposed to the suggested method in order to estimate capacity and resistance. These estimations are compared to direct measurements of the SOH indicators with standard tests. The obtained estimations of capacities and instantaneous resistances demonstrate good accuracy over a temperature and state-of-charge range typical for EV operating conditions and allow thus for online detection of battery degradation. The proposed method is also found to be suitable for on-board application in respect of processing power and memory restrictions.
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| 42. |
- Klass, Verena, 1985-
(författare)
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Battery Health Estimation in Electric Vehicles
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For the broad commercial success of electric vehicles (EVs), it is essential to deeply understand how batteries behave in this challenging application. This thesis has therefore been focused on studying automotive lithium-ion batteries in respect of their performance under EV operation. Particularly, the need for simple methods estimating the state-of-health (SOH) of batteries during EV operation has been addressed in order to ensure safe, reliable, and cost-effective EV operation. Within the scope of this thesis, a method has been developed that can estimate the SOH indicators capacity and internal resistance. The method is solely based on signals that are available on-board during ordinary EV operation such as the measured current, voltage, temperature, and the battery management system’s state-of-charge estimate. The approach is based on data-driven battery models (support vector machines (SVM) or system identification) and virtual tests in correspondence to standard performance tests as established in laboratory testing for capacity and resistance determination. The proposed method has been demonstrated for battery data collected in field tests and has also been verified in laboratory. After a first proof-of-concept of the method idea with battery pack data from a plug-in hybrid electric vehicle (PHEV) field test, the method was improved with the help of a laboratory study where battery electric vehicle (BEV) operation of a battery cell was emulated under controlled conditions providing a thorough validation possibility. Precise partial capacity and instantaneous resistance estimations could be derived and an accurate diffusion resistance estimation was achieved by including a current history variable in the SVM-based model. The dynamic system identification battery model gave precise total resistance estimates as well. The SOH estimation method was also applied to a data set from emulated hybrid electric vehicle (HEV) operation of a battery cell on board a heavy-duty vehicle, where on-board standard test validation revealed accurate dynamic voltage estimation performance of the applied model even during high-current situations. In order to exhibit the method’s intended implementation, up-to-date SOH indicators have been estimated from driving data during a one-year time period.
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| 43. |
- Klass, Verena, et al.
(författare)
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Capturing lithium-ion battery dynamics with support vector machine-based battery model
- 2015
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 298, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- During long and high current pulses, diffusion resistance becomes important in lithium-ion batteries. In such diffusion-intense situations, a static support vector machine-based battery model relying on instantaneous current, state-of-charge (SOC), and temperature is not sufficient to capture the time-dependent voltage characteristics. In order to account for the diffusion-related voltage dynamics, we suggest therefore the inclusion of current history in the data-driven battery model by moving averages of the recent current. The voltage estimation performance of six different dynamic battery models with additional current history input is studied during relevant test scenarios. All current history models improve the time-dependent voltage drop estimation compared to the static model, manifesting the beneficial effect of the additional current history input during diffusion-intense situations. The best diffusion resistance estimation results are obtained for the two-step voltage estimation models that incorporate a reciprocal square root of time weighing function for the current of the previous 100 s or an exponential time function with a 20 s time constant (1–8% relative error). Those current history models even improve the overall voltage estimation performance during the studied test scenarios (under 0.25% root-mean-square percentage error).
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| 44. |
- Klass, Verena, et al.
(författare)
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Dynamical Lithium-Ion Battery Model Identificationusing Electric Vehicle Operating Data for Resistance Estimation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- State-of-health (SOH) estimates of batteries are essential on-board electric vehicles (EVs) in order to provide safe, reliable, and cost-effective battery operation. Here, we present an approach for the estimation of the battery SOH indicator internal resistance. Battery models are constructed on the basis of ordinary EV operating data. The 10 s discharge resistance, which is an established battery figure-of-merit from laboratory testing, can be conveniently computed from the identified model parameters. Dynamical battery models based on a current input and a voltage output with model parameters dependent on temperature and state-of-charge (SOC) are derived using AutoRegressive with eXogenous input (ARX) models. The suggested method is validated with usage data from emulated EV operation of an automotive lithium-ion battery cell. The resistance values are estimated accurately by the proposed model for a SOC and temperature range spanning typical EV operating conditions (average relative estimation error of 1.5%). The method even provides an uncertainty interval for the resistance estimations, which is found to be very narrow. The linear identification of the model parameters and the resistance computation are very fast rendering the method suitable for on-board application.
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| 45. |
- Klass, Verena, et al.
(författare)
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Evaluating real-life performance of lithium-ion battery packs in electric vehicles
- 2012
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Ingår i: ECS Transactions 2012. - : Electrochemical Society. - 9781607683315 ; , s. 1-11
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Konferensbidrag (refereegranskat)abstract
- In regard to the increasing market launch of plug-in hybrid electric vehicles (PHEVs), understanding battery pack performance under electric vehicle (EV) operating conditions is essential. As lifetime still remains an issue for battery packs, it is a necessity to monitor the battery pack's state-of-health (SOH) on-board. Standard performance tests for health evaluation do not apply since operation interruptions and additional testing equipment are beyond question during ordinary EV usage. We suggest a novel methodology of performance estimation from real-life battery data. On the basis of battery pack data collected during PHEV operation, a support vector machine model is constructed that serves as source for performance evaluation figures. The SOH indicator "10 s discharge resistance" as known from hybrid pulse power characterization (HPPC) tests is chosen to exemplify how performance degradation can be followed over a year.
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| 46. |
- Klass, Verena, et al.
(författare)
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Evaluating Real-Life Performance of Lithium-Ion Battery Packs in Electric Vehicles
- 2012
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 159:11, s. A1856-A1860
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Tidskriftsartikel (refereegranskat)abstract
- In regard to the increasing market launch of plug-in hybrid electric vehicles (PHEVs), understanding battery pack performance under electric vehicle (EV) operating conditions is essential. As lifetime still remains an issue for battery packs, it is a necessity to monitor the battery pack's state-of-health (SOH) on-board. Standard laboratory performance tests for health evaluation do not apply since operation interruptions and additional testing equipment are out of the question during ordinary EV usage. We suggest a novel methodology of performance estimation from real-life battery data. On the basis of battery pack data collected during PHEV operation, a support vector machine model capturing battery behavior characteristics is constructed. By virtually testing this battery model, access to standard performance evaluation figures can be gained. The SOH indicator "10 s discharge resistance" as known from hybrid pulse power characterization (HPPC) tests is chosen to exemplify how performance can be followed over a year.
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| 47. |
- Klass, Verena, et al.
(författare)
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Li-ion battery performance in electric vehicles
- 2010
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Ingår i: AABC 2010 Conference and Symposia Proceedings.
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Konferensbidrag (refereegranskat)abstract
- When Li-ion batteries are applied in challenging applications like the propulsion of electric vehicles, it is essential to understand their performance and degradation as a function of their use in order to predict and improve their life time. Therefore, data on the behavior of batteries during electric vehicle operation is documented and methods and strategies for the processing of the real-life data are developed. From battery data analysis, insight into the characteristics of Li-ion batteries in electric vehicles can be gained and battery stress factors can be identified. Ultimately, the impact of operation conditions and battery specifications on battery performance and especially on battery performance degradation are intended to be described quantitatively. Recommendations on the optimum operation of the battery in regard of prolonging battery life time are meant to be given.
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| 48. |
- Klass, Verena, et al.
(författare)
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State-of-health estimation of lithium-ion battery under emulated HEV operation on board heavy-duty truck
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper addresses the need for simple and cost-effective methods that detect the state-of-health (SOH) of batteries in vehicle applications solely based on data readily available from the battery management system without any knowledge of battery properties, prior laboratory measurements or additional equipment.A power-optimized lithium-ion battery cell is operated in an emulated hybrid electric vehicle (HEV) environment on board a conventional heavy-duty truck. The HEV operation of the battery cell depends on the driving pattern of the truck within set limits. Beyond the HEV operation, the performance of the battery cell is periodically measured with on-board standard pulse and capacity tests. On basis of the battery operating data collected in the field test, support vector machine-based battery models are built. From a model input of current, temperature, state-of-charge, and current history, the model accurately estimates the battery voltage despite the tough HEV operating conditions with high current pulses. This data-driven battery model is used to estimate the battery cell’s charge and discharge resistance as well as capacity, i.e. the performance measures verified with the standard tests. These SOH indicators can be predicted by the model with adequate accuracy for on-board SOH detection and are followed throughout the one-year field test period.
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| 49. |
- Klett, Matilda, et al.
(författare)
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Altered electrode degradation with temperature in LiFePO4/mesocarbon microbead graphite cells diagnosed with impedance spectroscopy
- 2014
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 141, s. 173-181
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Electrode degradation in LiFePO4 / mesocarbon microbead graphite (MCMB) pouch cells aged at 55 °C by a synthetic hybrid drive cycle or storage is diagnosed and put into context with previous results of aging at 22 °C. The electrode degradation is evaluated by means of electrochemical impedance spectroscopy (EIS), measured separately on electrodes harvested from the cells, and by using a physics-based impedance model for aging evaluation. Additional capacity measurements, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) are used in the evaluation. At 55 °C the LiFePO4 electrode shows increased particle/electronic conductor resistance, for both stored and cycled electrodes. This differs from results obtained at 22 °C, where the electrode suffered lowered porosity, particle fracture, and loss of active material. For graphite, only cycling gave a sustained effect on electrode performance at 55 °C due to lowered porosity and changes of surface properties, and to greater extent than at low temperature. Furthermore, increased current collector resistance also contributes to a large part of the pouch cell impedance when aged at increased temperatures. The result shows that increased temperature promotes different degradation on the electrode level, and is an important implication for high temperature accelerated aging. In light of the electrode observations, the correlation between full-cell and electrode impedances is discussed.
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| 50. |
- Lindberg, Jonas, et al.
(författare)
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Benchmarking of electrolyte mass transport in next generation lithium batteries
- 2017
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Ingår i: Journal of Electrochemical Science and Engineering. - : International Association of Physical Chemists (IAPC). - 1847-9286. ; 7:4, s. 213-221
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Tidskriftsartikel (refereegranskat)abstract
- Beyond conductivity and viscosity, little is often known about the mass transport properties of next generation lithium battery electrolytes, thus, making performance estimation uncertain when concentration gradients are present, as conductivity only describes performance in the absence of these gradients. This study experimentally measured the diffusion resistivity, originating from voltage loss due to a concentration gradient, together with the ohmic resistivity, obtained from ionic conductivity measurements, hence, evaluating electrolytes both with and without the presence of concentration gradients. Under galvanostatic conditions, the concentration gradients, of all electrolytes examined, developed quickly and the diffusion resistivity rapidly dominated the ohmic resistivity. The electrolytes investigated consisted of lithium salt in: room temperature ionic liquids (RTIL), RTIL mixed organic carbonates, dimethyl sulfoxide (DMSO), and a conventional Li-ion battery electrolyte. At steady state the RTIL electrolytes displayed a diffusion resistivity similar to 20 times greater than the ohmic resistivity. The DMSO-based electrolyte showed mass transport properties similar to the conventional Li-ion battery electrolyte. In conclusion, the results presented in this study show that the diffusion polarization must be considered in applications where high energy and power density are desired.
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