| 1. |
- Abbafati, Cristiana, et al.
(författare)
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- 2020
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Tidskriftsartikel (refereegranskat)
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| 2. |
- 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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| 3. |
- Mikheenkova, Anastasiia, et al.
(författare)
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Visualizing ageing-induced heterogeneity within large prismatic lithium-ion batteries for electric cars using diffraction radiography
- 2024
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 599
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Tidskriftsartikel (refereegranskat)abstract
- In this study, Synchrotron X-ray diffraction (XRD) radiography was utilized to investigate the ageing heterogeneity in 48 Ah prismatic lithium-ion cells with Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) as the positive electrode active material and graphite as the negative electrode active material after ∼2800 cycles. The study revealed that the area closest to the positive electrode tab is most vulnerable to degradation, particularly impacting the NMC material. Application of principal component analysis allowed to differentiate and visualize part of positive electrode material that has a different degradation due to the lithium plating. A comparison of non-destructive X-ray diffraction-based methods and electrochemical characterization method which was performed on the opened cell has shown an importance of a complementary approach. Our results highlight the feasibility of employing non-destructive techniques to study large prismatic cells, thereby presenting extensive opportunities for advancements in battery research and industry.
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| 4. |
- Smith, Alexander J., et al.
(författare)
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Localized lithium plating under mild cycling conditions in high-energy lithium-ion batteries
- 2023
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Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 573
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Tidskriftsartikel (refereegranskat)abstract
- Conditions such as the temperature and pressure experienced by lithium-ion battery components are dependent on cell geometry and can vary widely within a large cell. The resulting uneven degradation is challenging to study at the full cell level but can be revealed upon disassembly and post mortem analysis. In this work, we report localized lithium plating in automotive-grade, prismatic lithium-ion cells, also under cycling conditions generally considered to be mild (e.g., 5–65 %SOC, 23 °C, 0.5C cycle rate). Dead lithium content is quantified using 7Li nuclear magnetic resonance spectroscopy in both electrode and separator samples, corresponding to substantial capacity fade (26–46%) of the full cells. Severe lithium plating is typically initiated in regions near the positive tab, in which both the separators and negative electrodes are ultimately deactivated. High pressure arises during cycling, and we propose a deactivation mechanism based on high local stress due to electrode expansion and external constraint. Further, we develop a model to demonstrate that component deactivation can result in lithium plating even under mild cycling conditions. Notably, components harvested from regions with no detected lithium plating maintained adequate electrochemical performance.
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| 5. |
- Svens, Pontus, 1970-, et al.
(författare)
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Evaluating Performance and Cycle Life Improvements in the Latest Generations of Prismatic Lithium-Ion Batteries
- 2022
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Ingår i: IEEE TRANSACTIONS ON TRANSPORTATION ELECTRIFICATION. - : Institute of Electrical and Electronics Engineers (IEEE). - 2332-7782. ; 8:3, s. 3696-3706
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, the market interest for electrified vehicles has increased considerably alongside global climate initiatives. This has coincided with vast improvements in automotive-grade, lithium-ion battery performance. This has increased the range of battery electric vehicles and plug-in hybrids, but lifetime remains a challenge. Aging during fast charging is especially difficult to understand due to its nonlinear dependence on charge rate, state-of-charge, and temperature. We present results from fast charging of several energy-optimized, prismatic lithium-ion battery cell generations with a nickel manganese cobalt (NMC)/graphite chemistry through comparison of capacity retention, resistance, and dQ/dV analysis. Changes in cell design have increased energy density by almost 50% over six years of cell development and acceptable cycle life can be expected, even under fast charging, when restricting the usage of the available capacity. Even though this approach reduces the useable energy density of a battery system, this tradeoff could still be acceptable for vehicle applications where conventional overnight charging is not possible. The tested cell format has been used for a decade in electrified vehicles. The ongoing development and improvement of this cell format by several cell manufacturers suggests that it will continue to be a good choice for future vehicles.
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| 6. |
- Bergfelt, Andreas, et al.
(författare)
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A Mechanical Robust yet highly Conductive Diblock Copolymer-based Solid Polymer Electrolyte for Room Temperature Structural Battery Applications
- 2020
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Ingår i: ACS Applied Polymer Materials. - : American Chemical Society (ACS). - 2637-6105. ; 2:2, s. 939-948
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Impact of Compression on the Electrochemical Performance of the Sulfur/Carbon Composite Electrode in Lithium-Sulfur Batteries
- 2022
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Ingår i: Batteries & Supercaps. - : Wiley-VCH Verlagsgesellschaft. - 2566-6223. ; 5:7
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Tidskriftsartikel (refereegranskat)abstract
- While lithium-sulfur batteries theoretically have both high gravimetric specific energy and volumetric energy density, only its specific energy has been experimentally demonstrated to surpass that of the state-of-the-art lithium-ion systems at cell level. One major reason for the unrealized energy density is the low capacity density of the highly porous sulfur/carbon composite as the positive electrode. In this work, mechanical compression at elevated temperature is demonstrated to be an effective method to increase the capacity density of the electrode by at least 90 % and moreover extends its cycle life. Distinct impacts of compression on the resistance profiles of electrodes with different thickness are investigated by tortuosity factors derived from both electrochemical impedance spectroscopy, X-ray computed tomography and kinetic analysis based on operando X-ray diffraction. The results highlights the importance of a homogeneous electrode structure highlight lithium-sulfur system.
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| 8. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Poly(Ethylene Glycol-block-2-Ethyl-2-Oxazoline) as Cathode Binder in Lithium-Sulfur Batteries
- 2021
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Ingår i: ChemistryOpen. - : John Wiley & Sons. - 2191-1363. ; 10:10, s. 960-965
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Tidskriftsartikel (refereegranskat)abstract
- Functional binders constitute a strategy to overcome several challenges that lithium-sulfur (Li-S) batteries are facing due to soluble reaction intermediates in the positive electrode. Poly (ethylene oxide) (PEO) and poly (vinylpyrrolidone) (PVP) are in this context a previously well-explored binder mixture. Their ether and amide groups possess affinity to the dissolved sulfur species, which enhances the sulfur utilization and mitigates the parasitic redox shuttle. However, the immiscibility of PEO and PVP is a concern for electrode stability. Copolymers comprising ether and amide groups are thus promising candidates to improve the stability the system. Here, a series of poly (ethylene glycol-block-2-ethyl-2-oxazoline) with various block lengths is synthesized and explored as binders in S/C composite electrodes in Li-S cells. While the electrochemical analyses show that although the sulfur utilization and capacity retention of the tested electrodes are similar, the integrity of the as-cast electrodes can play a key role for power capability.
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| 9. |
- 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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| 10. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Towards reliable three-electrode cells for lithium–sulfur batteries
- 2022
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 58:5, s. 705-708
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Tidskriftsartikel (refereegranskat)abstract
- Three-electrode measurements are valuable to the understanding of the electrochemical processes in a battery system. However, their application in lithium–sulfur chemistry is difficult due to the complexity of the system and thus rarely reported. Here, we present a simple three-electrode cell format with relatively good life time and minimum interference with the cell operation.
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| 11. |
- Mathew, Alma, et al.
(författare)
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Investigating oxidative stability of lithium-ion battery electrolytes using synthetic charge-discharge profile voltammetry
- 2021
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Ingår i: Journal of Power Sources Advances. - : Elsevier. - 2666-2485. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Electrolytes are an integral part of any electrochemical energy storage systems, including batteries. Among the many properties which determine the applicability of a Li-ion battery electrolyte, electrochemical stability - and for high voltage electrodes, in particular anodic stability - is a key parameter to consider. Despite being simple and straightforward to employ, the conventional linear sweep voltammetry (LSV) technique often leads to an over-estimation of the oxidative stability. In this study, an alternative approach termed Synthetic Charge-discharge Profile Voltammetry (SCPV) is explored to investigate the oxidative electrolyte stability. We have found this to be a convenient method of quantifying the anodic stability of the electrolyte in a more practically representative manner, in which passivation kinetics and electrode potential changes at the electrode-electrolyte interface are more appropriately reproduced. The viability of this technique is explored with liquid electrolytes based on ether, carbonate, sulfone and carbonate-sulfone mixtures, all with lithium hexafluorophosphate (LiPF6) salt, tested for a potential profile equivalent to LiNi0.5Mn1.5O4 electrodes. The credibility of this technique is validated by correlations to the coulombic efficiencies of corresponding half-cells.
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| 12. |
- Mathew, Alma, et al.
(författare)
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Understanding the Capacity Fade in Polyacrylonitrile Binder-based LiNi0.5Mn1.5O4 Cells
- 2022
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Ingår i: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; 5:12
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Binders are electrochemically inactive components that have a crucial impact in battery ageing although being present in only small amounts, typically 1?3?% w/w in commercial products. The electrochemical performance of a battery can be tailored via these inactive materials by optimizing the electrode integrity and surface chemistry. Polyacrylonitrile (PAN) for LiNi0.5Mn1.5O4 (LNMO) half-cells is here investigated as a binder material to enable a stable electrode-electrolyte interface. Despite being previously described in literature as an oxidatively stable polymer, it is shown that PAN degrades and develops resistive layers within the LNMO cathode. We demonstrate continuous internal resistance increase in LNMO-based cells during battery operation using intermittent current interruption (ICI) technique. Through a combination of on-line electrochemical mass spectrometry (OEMS) and X-ray photoelectron spectroscopy (XPS) characterization techniques, the degradation products can be identified as solid on the LNMO electrode surface, and no excessive gas formation seen. The increased resistance and parasitic processes are correlated to side-reactions of the PAN, possibly intramolecular cyclization, which can be identified as the main cause of the comparatively fast capacity fade.
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| 13. |
- Mikheenkova, Anastasiia, et al.
(författare)
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Resolving high potential structural deterioration in Ni-rich layered cathode materials for lithium-ion batteries operando
- 2023
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Ingår i: Journal of Energy Storage. - : Elsevier. - 2352-152X .- 2352-1538. ; 57
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Tidskriftsartikel (refereegranskat)abstract
- LixNi0.90Co0.05Al0.05O2 (NCA) extracted from an automotive battery cell is studied using a combination of in-house operando techniques to understand the correlation between gas evolution and structural collapse when NCA is cycled to high potentials in a lithium-ion battery configuration. The operando techniques comprise X-ray diffraction (XRD) and online electrochemical mass spectrometry (OEMS), and cycled using intermittent current interruption (ICI). The ICI cycling protocol is used to assess the dynamic change in resistance as well as to provide a validation of the operando setups. Both gas evolution and structural collapse have previously been observed as degradation mechanisms of Ni-rich electrodes including NCA, however, their causal link is still under debate. Here our presented results show a correlation between the decrease of the interlayer distance in NCA with both an increase in CO2 evolution and diffusion resistance above 4.1 V. Additionally, particle cracking, which is a mechanism often correlated with gas evolution, was found to be reversible and visible before gas evolution and Li diffusion resistance increase. The ICI technique is shown to be useful for the correlation of operando experiments on parallel setups and evaluation of mass transport dependent processes.
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| 14. |
- Misiewicz, Casimir, et al.
(författare)
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Online electrochemical mass spectrometry on large-format Li-ion cells
- 2023
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Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 554
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Tidskriftsartikel (refereegranskat)abstract
- Advances in methodologies for real-time analysis of batteries have come a long way, especially with the development of Operando Electrochemical Mass Spectrometry (OEMS). These approaches allow for the deter-mination of side reactions during battery cycling with unprecedented selectivity and sensitivity, providing vital information necessary for determination of lifetime-limiting processes. However, the work thus far has primarily been carried out on model battery systems, where cell atmospheres are largely altered (through open flow, closed cell, and intermittent sampling approaches) and operation conditions are therefore not comparable with real-life situations. Herein, the development and validation of an intermittently closed OEMS system adapted for readily available commercial batteries is showcased. We provide a detailed description of a unique analysis design for large-format PHEV2 cells, with subsequent pressure and gassing data. A qualitative analysis of the results shows that side reactions brought on by structural transitions within both electrodes can be clearly observed. Transi-tions causing large volume changes in graphite induce H2 and C2H4 as SEI reformation products while the c lattice collapse in NMC induces CO2 evolution (through O2 release). OEMS can therefore be used for the quick and effective study of commercially available rechargeable batteries without influencing the internal battery chemistry.
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| 15. |
- Ostli, Elise R., et al.
(författare)
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Limitations of Ultrathin Al2O3 Coatings on LNMO Cathodes
- 2021
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:45, s. 30644-30655
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Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates the application of Al2O3 coatings for the high-voltage cathode material LiNi0.5–xMn1.5+xO4−δ (LNMO) by atomic layer deposition. The ultrathin and uniform coatings (0.6–1.7 nm) were deposited on LNMO particles and characterized by scanning transmission electron microscopy, inductively coupled plasma mass spectrometry, and X-ray photoelectron spectroscopy. Galvanostatic charge discharge cycling in half cells revealed, in contrast to many published studies, that even coatings of a thickness of 1 nm were detrimental to the cycling performance of LNMO. The complete coverage of the LNMO particles by the Al2O3 coating can form a Li-ion diffusion barrier, which leads to high overpotentials and reduced reversible capacity. Several reports on Al2O3-coated LNMO using alternative coating methods, which would lead to a less homogeneous coating, revealed the superior electrochemical properties of the Al2O3-coated LNMO, suggesting that complete coverage of the particles might in fact be a disadvantage. We show that transition metal ion dissolution during prolonged cycling at 50 °C is not hindered by the coating, resulting in Ni and Mn deposits on the Li counter electrode. The Al2O3-coated LNMO particles showed severe signs of pitting dissolution, which may be attributed to HF attack caused by side reactions between the electrolyte and the Al2O3 coating, which can lead to additional HF formation. The pitting dissolution was most severe for the thickest coating (1.7 nm). The uniform coating coverage may lead to non-uniform conduction paths for Li, where the active sites are more susceptible to HF attack. Few benefits of applications of very thin, uniform, and amorphous Al2O3 coatings could thus be verified, and the coating is not offering long-term protection from HF attack.
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| 16. |
- Salian, Girish D., et al.
(författare)
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Investigation of Water-Soluble Binders for LiNi0.5Mn1.5O4-Based Full Cells
- 2022
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Ingår i: ChemistryOpen. - : John Wiley & Sons. - 2191-1363. ; 11:6
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Tidskriftsartikel (refereegranskat)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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| 17. |
- Salian, Girish D., et al.
(författare)
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Understanding the electrochemical and interfacial behaviour of sulfolane-based electrolytes in LiNi0.5Mn1.5O4-graphite full-cells
- 2023
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Ingår i: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; n/a:n/a
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Tidskriftsartikel (refereegranskat)abstract
- An ethylene carbonate-free electrolyte composed of 1 M lithium bis(fluorosulfonyl) imide (LiFSI) in sulfolane (SL) is studied here for LiNi0.5Mn1.5O4-graphite full-cells. An important focus on the evaluation of the anodic stability of the SL electrolyte and the passivation layers formed on LNMO and graphite is being analysed along with intermittent current interruption (ICI) technique to observe the resistance while cycling. The results show that the sulfolane electrolyte shows more degradation at higher potentials unlike previous reports which suggested higher oxidative stability. However, the passivation layers formed due to this electrolyte degradation prevents further degradation. The resistance measurements show that major resistance arises from the cathode. The pressure evolution during the formation cycles suggests that there is lower gas evolution with sulfolane electrolyte than in the conventional electrolyte. The study opens a new outlook on the sulfolane based electrolyte especially regarding its oxidative/anodic stability.
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| 18. |
- Østli, Elise R., et al.
(författare)
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On the Durability of Protective Titania Coatings on High‐Voltage Spinel Cathodes
- 2022
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Ingår i: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; 15:12
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Tidskriftsartikel (refereegranskat)abstract
- TiO2-coating of LiNi0.5-xMn1.5+xO4 (LNMO) by atomic layer deposition (ALD) has been studied as a strategy to stabilize the cathode/electrolyte interface and mitigate transition metal (TM) ion dissolution. The TiO2 coatings were found to be uniform, with thicknesses estimated to 0.2, 0.3, and 0.6 nm for the LNMO powders exposed to 5, 10, and 20 ALD cycles, respectively. While electrochemical characterization in half-cells revealed little to no improvement in the capacity retention neither at 20 nor at 50 °C, improved capacity retention and coulombic efficiencies were demonstrated for the TiO2-coated LNMO in LNMO||graphite full-cells at 20 °C. This improvement in cycling stability could partly be attributed to thinner cathode electrolyte interphase on the TiO2-coated samples. Additionally, energy-dispersive X-ray spectroscopy revealed a thinner solid electrolyte interphase on the graphite electrode cycled against TiO2-coated LNMO, indicating retardation of TM dissolution by the TiO2-coating.
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