Construction of a Stable LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) Cathode Interface by a Multifunctional Organosilicon Electrolyte Additive

It is still a big challenge to stabilize a Ni-rich cathode interface at high current rate and a long-term cycle in the present Li-ion battery for electric vehicles. In this work, N,O-bis(trimethylsilyl)acetamide (BSA) is utilized as a multifunctional electrolyte additive to stabilize the LiNi0.8Co0.1Mn0.1O2 cathode interface and enhance its electrochemical performance. After 200 cycles, the LiNi0.8Co0.1Mn0.1O2/Li cell at 1C rate with 0.5% BSA shows improved capacity retention of 86%, while it shows only 69.4% with the baseline electrolyte. When the discharge rate is increased to 2C, the LiNi0.8Co0.1Mn0.1O2/Li cell with BSA additive shows improved capacity retention of 72.6% after 400 cycles, while the counterpart is only 49.5%. The experimental results show that HF and H2O can be scavenged by BSA, and the hydrolysis of LiPF6 is reduced. Moreover, the BSA additive can be preferentially oxidized during the charging process and form a robust, uniform electrode/electrolyte interface film on the NCM811 cathode surface. Consequently, a better CEI film can suppress the electrolyte decomposition, improve cathode interface stability, and alleviate transition metal ions dissolution.