Addressing electrode degradation issue in high negative to positive electrode capacity ratio lithium-ion batteries using water-in-salt electrolyte

Authors
Zhanadilov, OrynbayAkhmetova, AktilekSon, JunehyukYu, Jun HoKim, MingonyChung, Kyung YoonKim, Hee JaeBakenov, ZhumabayYashiro, HitoshiMyung, Seung-Taek
Issue Date
2025-06
Publisher
SPRINGER NATURE
Citation
Advanced Composites and Hybrid Materials, v.8, no.3
Abstract
In this study, we investigate the underlying causes of degradation in Li4Ti5O12//LiMn2O4 cells with an N/P ratio of 0.9 utilizing 19.44 m LiN(SO2CF3)(2) and 8.33 m LiN(SO2CF2CF3)(2) (Li(TFSI)(0.7)(BETI)(0.3)center dot 2H(2)O), a hydrate-melt electrolyte. We identify the formation of hydrofluoric acid (HF) during electrochemical reactions as a key factor leading to both Mn dissolution from the LiMn2O4 cathode and rapid self-discharge at room temperature. To address these challenges, we apply a calcium fluoride (CaF2) coating to the electrodes, designed to scavenge HF by reacting to form calcium bifluoride (Ca(HF2)(2)). This reaction underscores the unique quasi-non-aqueous nature of Li(TFSI)(0.7)(BETI)(0.3)center dot 2H(2)O, which facilitates chemical processes not possible in traditional aqueous electrolytes. Electrochemical evaluations demonstrate that the CaF2-coated electrode exhibits improved capacity retention and higher coulombic efficiency than their uncoated counterparts. Despite these enhancements, the rapid self-discharge issue remains, indicating that additional factors contribute to this phenomenon and require further investigation. Our findings highlight the potential of water-in-salt systems, particularly the Li(TFSI)(0.7)(BETI)(0.3)center dot 2H(2)O electrolyte, in advancing lithium-ion battery technology by leveraging their distinct chemical environment. This study provides insights into the mechanisms affecting the stability and performance of hydrate-melt electrolyte for exploiting quasi-non-aqueous systems in energy-storage applications.
Keywords
LIMN2O4 CATHODE; CHEMISTRY; STATE; SAFE; SELF-DISCHARGE; Hydrate-melt electrolyte; Lithium-ion batteries; HF formation; Mn dissolution; CaF2 coating; Water-in-salt electrolyte
ISSN
2522-0128
URI
https://pubs.kist.re.kr/handle/201004/152681
DOI
10.1007/s42114-025-01347-5
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KIST Article > Others
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