Enhancing compatibility between LiNi0.8Co0.1Mn0.1O2 and LiPF6-based electrolyte via bis(trimethylsilyl)oxalate additive

Abstract

LiNi0.8Co0.1Mn0.1O2 (NCM811)-layered oxide has a high discharge capacity and is considered as an alternative cathode for next-generation high-energy density lithium-ion batteries (LIBs). However, the corrosion of LiPF6-based electrolyte and the poor stability of the cathode solid electrolyte interface (CEI) film pose a threat to the cyclic stability of the battery. Herein, bis(trimethylsilyl)oxalate (DTMSO) is introduced as a novel multifunctional electrolyte additive to construct a stable CEI film and improve the high temperature tolerance of NCM811/Li cells. Results show that DTMSO can effectively scavenge HF resulted from trace water and high temperature, preventing the detrimental effects of HF on CEI film and NCM811 electrode material. More than that, DTMSO can react with LiPF6 to form conducive lithium tetrafluoro(oxalate)phosphate (LiTFOP) when undergoes the ordeal of high temperature (55 °C) for 24 h. The as-generated LiTFOP aids in the construction of a stable and conductive CEI film that is rich in LiF and LixPOyFz. Benefit from these characteristics, DTMSO additive enables effective protection of the electrode material and mitigates capacity decay in the battery, ultimately facilitating good cycling performance and improving ability to resist high temperature within a certain time. As a result, the capacity retention rate of the NCM811/Li cell after 100 cycles is increased from 67.8% to 85.6%, when the test condition is shelved at 55 °C for 24 h and then changed back to cycling at 25 °C. This work provides a viable strategy for the development of electrolytes compatible with nickel-rich cathode and is of great significance for the development of advanced LIBs.