Electrochemical behavior of LiNi0.6Mn0.2Co0.2O2 cathode in different aqueous electrolytes

Abstract

In the past decade, there has been a growing interest in aqueous lithium-ion batteries (LiBs) since they are a lower cost and safer alternative to their traditional organic versions. Such interest is fueled by the need for large-scale stationary energy storage systems. The introduction of “water-in-salt” LiTFSI electrolyte has paved the way for higher voltage aqueous batteries, thereby helping their energy densities. LiNi0.6Mn0.2Co0.2O2 (NMC 622) is a promising cathode material for aqueous LiBs owing to its high operating voltage and lithium capacity. However, there is no report of its use in aqueous electrolytes. NMC 622 was tested in Li2SO4, LiNO3, and “water-in-salt” LiTFSI aqueous electrolytes for the first time in this study. Our results showed that NMC 622 exhibits excellent electrochemical performance in LiTFSI electrolyte reaching a maximum discharge capacity of 152 mAh g−1. On the other hand, fast capacity decay and rise in overpotential are observed in cases of nitrate and sulfate electrolytes. This study highlights the significance of electrolyte composition and states that high-nickel cathodes in “water-in-salt” LiTFSI electrolyte present promise for future aqueous LiBs.