Functional Trimethylsilyl-based Additives to Improve Fast Charging and Low-Temperature Performance of LiNi0.8Co0.1Mn0.1O2 based Lithium-ion Batteries
Description
Layered cathode material LiNi0.8Co0.1Mn0.1O2 (NCM811) is distinguished by its high nickel content, low cost, high working voltage, and high specific capacity. Lithium-ion batteries (LIBs) utilizing NCM811 demonstrate higher specific energy density and specific power density, rendering it a promising choice for fast-charging automotive batteries in the industry. However, at the high rate (>3C) cycling process, the stability of NCM811 material faces many challenges, such as safety, long cycle stability, rate stability caused by intergranular cracking of particles, phase transformation of their bulk and surface, strong instability of cathode electrolyte interfaces (CEIs), etc. In this study, two organic compounds (tri(trimethylsilyl) phosphate and N-trimethylsilyl diethylamine) were utilized as electrolyte additives to improve overall low-temperature stability and cycle stability of NCM811-based batteries simultaneously. Incorporating two silyl-based organics into the electrolyte significantly enhances rate capability, high-rate (5C) cycling performance, and impedance characteristics of the NCM811. Furthermore, these additives demonstrate excellent compatibility with Li4Ti5O12 anodes. With addition of 0.5%vol tri(trimethylsilyl) phosphate, LTO//NCM811 battery shows a capacity retention of 77% after 120 cycles at a low temperature of -20℃ and high rate of 5C. Combining machine learning with density functional theory simulation, the additive has bifunctional ability of removing H2O and HF in the electrolyte and enhancing passivation film formation. This work provides alternative pathway for enhancing low-temperature performance and fast charging capabilities of the batteries.