| 1. |
- Lundgren, Anders, 1978, et al.
(författare)
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Formation of Gold Nanoparticle Size and Density Gradients via Bipolar Electrochemistry
- 2016
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Ingår i: Chemelectrochem. - : Wiley. - 2196-0216. ; 3:3, s. 378-382
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Tidskriftsartikel (refereegranskat)abstract
- Bipolar electrochemistry is employed to demonstrate the formation of gold nanoparticle size gradients on planar surfaces. By controlling the electric field in a HAuCl4-containing electrolyte, gold was reduced onto 10 nm diameter particles immobilized on pre-modified thiolated bipolar electrode (BPE) templates, resulting in larger particles towards the more cathodic direction. As the gold deposition was the dominating cathodic reaction, the increased size of the nanoparticles also reflected the current distribution on the bipolar electrode. The size gradients were also combined with a second gradient-forming technique to establish nanoparticle surfaces with orthogonal size and density gradients, resulting in a wide range of combinations of small/large and few/many particles on a single bipolar electrode. Such surfaces are valuable in, for example, cell-material interaction and combinatorial studies, where a large number of conditions are probed simultaneously.
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| 2. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Rapid determination of solid-state diffusion coefficients in Li-based batteries via intermittent current interruption method
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The galvanostatic intermittent titration technique (GITT) is considered the go-to method for determining the Li+ diffusion coefficients in insertion electrode materials. However, GITT-based methods are either time-consuming, prone to analysis pitfalls or require sophisticated interpretation models. Here, we propose the intermittent current interruption (ICI) method as a reliable, accurate and faster alternative to GITT-based methods. Using Fick’s laws, we prove that the ICI method renders the same information as the GITT within a certain duration of time since the current interruption. Via experimental measurements, we also demonstrate that the results from ICI and GITT methods match where the assumption of semi-infinite diffusion applies. Moreover, the benefit of the non-disruptive ICI method to operando materials characterization is exhibited by correlating the continuously monitored diffusion coefficient of Li+ in a LiNi0.8Mn0.1Co0.1O2-based electrode to its structural changes captured by operando X-ray diffraction measurements.
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| 3. |
- Kitz, Paul G., et al.
(författare)
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Operando EQCM-D with Simultaneous in Situ EIS : New Insights into Interphase Formation in Li Ion Batteries
- 2019
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Ingår i: Analytical Chemistry. - : AMER CHEMICAL SOC. - 0003-2700 .- 1520-6882. ; 91:3, s. 2296-2303
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Tidskriftsartikel (refereegranskat)abstract
- An operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) with simultaneous in situ electrochemical impedance spectroscopy (EIS) has been developed and applied to study the solid electrolyte interphase (SEI) formation on copper current collectors in Li-ion batteries. The findings are backed by EIS simulations and complementary analytical techniques, such as online electrochemical mass spectrometry (OEMS) and X-ray photoelectron spectroscopy (XPS). The evolution of mass and the mechanical properties of the SEI are directly correlated to the electrode impedance. Electrolyte reduction at the anode carbon active material initiates dissolution, diffusion, and deposition of reaction side products throughout the cell and increases electrolyte viscosity and the ohmic cell resistance as a result. On Cu the reduction of CuOx and HF occurs at >1.5 V and forms an initial LiF-rich interphase while electrolyte solvent reduction at <0.8 V vs Li+/Li adds a second, less rigid layer on top. Both the shear storage modulus and viscosity of the SEI generally increase upon cycling but-along with the SEI Li+ diffusion coefficient-also respond reversibly to electrode potential, likely as a result of Li+/EC interfacial concentration changes. Combined EIS-EQCM-D provides unique prospects for further studies of the highly dynamic structure-function relationships of electrode interphases in Li ion batteries.
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| 4. |
- Mikheenkova, Anastasiia, et al.
(författare)
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Ageing of High Energy Density Automotive Li-Ion Batteries : The Effect of Temperature and State-of-Charge
- 2023
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:8
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Tidskriftsartikel (refereegranskat)abstract
- Lithium ion batteries (LIB) have become a cornerstone of the shift to electric transportation. In an attempt to decrease the production load and prolong battery life, understanding different degradation mechanisms in state-of-the-art LIBs is essential. Here, we analyze how operational temperature and state-of-charge (SoC) range in cycling influence the ageing of automotive grade 21700 batteries, extracted from a Tesla 3 long Range 2018 battery pack with positive electrode containing LiNixCoyAlzO2 (NCA) and negative electrode containing SiOx-C. In the given study we use a combination of electrochemical and material analysis to understand degradation sources in the cell. Herein we show that loss of lithium inventory is the main degradation mode in the cells, with loss of material on the negative electrode as there is a significant contributor when cycled in the low SoC range. Degradation of NCA dominates at elevated temperatures with combination of cycling to high SoC (beyond 50%).
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| 5. |
- Nilsson, Viktor, 1985, et al.
(författare)
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Highly Concentrated LiTFSI-EC Electrolytes for Lithium Metal Batteries
- 2020
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 3:1, s. 200-207
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Tidskriftsartikel (refereegranskat)abstract
- Concentrated electrolytes have the potential to increase the stability for batteries with lithium metal anodes. In this study, liquid electrolytes were created by mixing ethylene carbonate (EC), a solid at room temperature, with a high concentration of LiTFSI salt. The binary LiTFSI-EC highly concentrated electrolytes have the benefit of extremely low volatility as compared to conventional organic electrolytes and also allow for cycling vs Li metal anodes. Using a LiTFSI-EC electrolyte with molar ratio 1:6, the Coulombic efficiency for Li plating/stripping on Cu is 97% at a current density of 1 mA cm-2 with a 2 mAh cm-2 capacity, pointing to a practically useful performance. In a full cell setup using a commercial LiFePO4 (LFP) cathode, the efficiency is maintained, proving compatibility. In comparison to other carbonate-based electrolytes, there is less accumulation of decomposition products on the surface of a cycled Li film, which in part explains the improved cycle life. In all, this electrolyte system shows promise in terms of electrochemical stability and may allow for safe Li metal batteries due to the inherent physical stability.
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| 6. |
- Aktekin, Burak, et al.
(författare)
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Understanding the Capacity Loss in LiNi0.5Mn1.5O4-Li4Ti5O12 Lithium-Ion Cells at Ambient and Elevated Temperatures
- 2018
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:21, s. 11234-11248
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Tidskriftsartikel (refereegranskat)abstract
- The high-voltage spinel LiNi0.5Mn1.5O4, (LNMO) is an attractive positive electrode because of its operating voltage around 4.7 V (vs Li/Li+) and high power capability. However, problems including electrolyte decomposition at high voltage and transition metal dissolution, especially at elevated temperatures, have limited its potential use in practical full cells. In this paper, a fundamental study for LNMO parallel to Li4Ti5O12 (LTO) full cells has been performed to understand the effect of different capacity fading mechanisms contributing to overall cell failure. Electrochemical characterization of cells in different configurations (regular full cells, back-to-back pseudo-full cells, and 3-electrode full cells) combined with an intermittent current interruption technique have been performed. Capacity fade in the full cell configuration was mainly due to progressively limited lithiation of electrodes caused by a more severe degree of parasitic reactions at the LTO electrode, while the contributions from active mass loss from LNMO or increases in internal cell resistance were minor. A comparison of cell formats constructed with and without the possibility of cross-talk indicates that the parasitic reactions on LTO occur because of the transfer of reaction products from the LNMO side. The efficiency of LTO is more sensitive to temperature, causing a dramatic increase in the fading rate at 55 degrees C. These observations show how important the electrode interactions (cross-talk) can be for the overall cell behavior. Additionally, internal resistance measurements showed that the positive electrode was mainly responsible for the increase of resistance over cycling, especially at 55 degrees C. Surface characterization showed that LNMO surface layers were relatively thin when compared with the solid electrolyte interphase (SEI) on LTO. The SEI on LTO does not contribute significantly to overall internal resistance even though these films are relatively thick. X-ray absorption near-edge spectroscopy measurements showed that the Mn and Ni observed on the anode were not in the metallic state; the presence of elemental metals in the SEI is therefore not implicated in the observed fading mechanism through a simple reduction process of migrated metal cations.
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| 7. |
- Aktekin, Burak, et al.
(författare)
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Understanding the Capacity Loss in LiNi0.5Mn1.5O4 - Li4Ti5O12 Lithium-Ion Cells at Ambient and Elevated Temperatures
- 2017
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Konferensbidrag (refereegranskat)abstract
- The high voltage spinel LiNi0.5Mn1.5O4 (LNMO) is an attractive positive electrode due to its operating voltage around 4.7 V (vs. Li/Li+) arising from the Ni2+/Ni4+ redox couple. In addition to high voltage operation, a second advantage of this material is its capability for fast lithium diffusion kinetics through 3-D transport paths in the spinel structure. However, the electrode material is prone to side reactions with conventional electrolytes, including electrolyte decomposition and transition metal dissolution, especially at elevated temperatures1. It is important to understand how undesired reactions originating from the high voltage spinel affect the aging of different cell components and overall cycle life. Half-cells are usually considered as an ideal cell configuration in order to get information only from the electrode of interest. However, this cell configuration may not be ideal to understand capacity fading for long-term cycling and the assumption of ‘stable’ lithium negative electrode may not be valid, especially at high current rates2. Also, among the variety of capacity fading mechanisms, the loss of “cyclable” lithium from the positive electrode (or gain of lithium from electrolyte into the negative electrode) due to side reactions in a full-cell can cause significant capacity loss. This capacity loss is not observable in a typical half-cell as a result of an excessive reserve of lithium in the negative electrode.In a full-cell, it is desired that the negative electrode does not contribute to side reactions in a significant way if the interest is more on the positive side. Among candidates on the negative side, Li4Ti5O12 (LTO) is known for its stability since its voltage plateau (around 1.5 V vs. Li/Li+) is in the electrochemical stability window of standard electrolytes and it shows a very small volume change during lithiation. These characteristics make the LNMO-LTO system attractive for a variety of applications (e.g. electric vehicles) but also make it a good model system for studying aging in high voltage spinel-based full cells.In this study, we aim to understand the fundamental mechanisms resulting in capacity fading for LNMO-LTO full cells both at room temperature and elevated temperature (55°C). It is known that electrode interactions occur in this system due to migration of reaction products from LNMO to the LTO side3, 4. For this purpose, three electrode cells have been cycled galvanostatically with short-duration intermittent current interruptions5 in order to observe internal resistance for both LNMO and LTO electrodes in a full cell, separately. Change of voltage curves over cycling has also been observed to get an insight into capacity loss. For comparison purposes, back-to-back cells (a combination of LNMO and LTO cells connected electrically by lithium sides) were also tested similarly. Post-cycling of harvested electrodes in half cells was conducted to determine the degree of capacity loss due to charge slippage compared to other aging factors. Surface characterization of LNMO as well as LTO electrodes after cycling at room temperature and elevated temperature has been done via SEM, XPS, HAXPES and XANES.ReferencesA. Kraytsberg, Y. Ein-Eli, Adv. Energy Mater., vol. 2, pp. 922–939, 2012.Aurbach, D., Zinigrad, E., Cohen, Y., & Teller, H. Solid State Ionics, 148(3), 405-416, 2002.Li et al., Journal of The Electrochemical Society, 160 (9) A1524-A1528, 2013.Aktekin et al., Journal of The Electrochemical Society 164.4: A942-A948. 2017.Lacey, M. J., ChemElectroChem. Accepted Author Manuscript. doi:10.1002/celc.201700129, 2017.
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| 8. |
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| 9. |
- Aktekin, Burak, et al.
(författare)
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Understanding the Rapid Capacity Fading of LNMO-LTO Lithium-ion Cells at Elevated Temperature
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The high voltage spinel LiNi0.5Mn1.5O4 (LNMO) has an average operating potential around 4.7 V vs. Li/Li+ and a gravimetric charge capacity of 146 mAh/g making it a promising high energy density positive electrode for Li-ion batteries. Additionally, the 3-D lithium transport paths available in the spinel structure enables fast diffusion kinetics, making it suitable for power applications [1]. However, the material displays large instability during cycling, especially at elevated temperatures. Therefore, significant research efforts have been undertaken to better understand and improve this electrode material.Electrolyte (LiPF6 in organic solvents) oxidation and transition metal dissolution are often considered as the main problems [2] for the systems based on this cathode material. These can cause a variety of problems (in different parts of the cell) eventually increasing internal cell resistance, causing active mass loss and decreasing the amount of cyclable lithium.Among these issues, cyclable lithium loss cannot be observed in half cells since lithium metal will provide almost unlimited capacity. Being a promising full cell chemistry for high power applications, there has also been a considerable interest on LNMO full cells with Li4Ti5O12 (LTO) used as the negative electrode. For this chemistry, for an optimized cell, quite stable cycling for >1000 cycles has been reported at room temperature while fast fading is still present at 55 °C [3]. This difference in performance (RT vs. 55 °C) is beyond most expectations and likely does not follow any Arrhenius-type of trend.In this study, a comprehensive analysis of LNMO-LTO cells has been performed at different temperatures (RT, 40 °C and 55 °C) to understand the underlying reasons behind stable cycling at room temperature and rapid fading at 55 °C. For this purpose, testing was made on regular cells (Figure 1a), 3-electrode cells (Figure 1b) and back-to-back cells [4] (Figure 1c). Electrode interactions (cross-talk) have been shown to exist in the LTO-LNMO system [5] and back-to-back cells have therefore been used to observe fading under conditions where cross-talk is impossible [4]. Galvanostatic cycling combined with short-duration intermittent current interruptions [6] was performed in order to separately observe changes in internal resistance for LNMO and LTO electrodes in a full cell. Ex-situ characterization of electrodes have also been performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES).Our findings show how important the electrode interactions can be in full cells, as a decrease in lithium inventory was shown to be the major factor for the observed capacity fading at elevated temperature. In this presentation, the effect of other factors – active mass loss and internal cell resistance – will be discussed together with the consequences of cross-talk.References[1] A. Kraytsberg et al. Adv. Energy Mater., vol. 2, pp. 922–939,2012.[2] J. H. Kim et al., ChemPhysChem, vol. 15, pp. 1940–1954, 2014.[3] H. M. Wu et al. J. E. Soc., vol. 156, pp. A1047–A1050, 2009.[4] S. R. Li et al., J. E. Soc., vol. 160, no. 9, pp. A1524–A1528, 2013.[5] Dedryvère et al. J. Phys. C., vol. 114 (24), pp. 10999–11008, 2010.[6] M. J. Lacey, ChemElectroChem, pp. 1–9, 2017.
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| 10. |
- Bergfelt, Andreas, et al.
(författare)
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Mechanically Robust and Highly Conductive Di-Block Copolymers as Solid Polymer Electrolytes for Room Temperature Li-ion Batteries
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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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