Disiloxanes Containing Tertiary Amine and Dioxaborolane Groups as Bifunctional Electrolyte Additive for Improved Cycling Life of LiNi0.8Co0.1Mn0.1O2/Graphite Batteries

Abstract A new disiloxane compound with tertiary amine and dioxaborolane group, N , N ‐dimethyl‐2‐(3‐(1,1,3,3‐tetramethyl‐3‐(3‐(2‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)ethoxy)propyl)disiloxanyl)propoxy)ethan‐1‐amine (TMBDSA), is designed and synthesized as functional electrolyte additive for improving the cycling stability of high‐capacity nickel‐rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811). The NCM811/graphite full cell test shows that the cycling stability is considerably improved by adding TMBDSA (0.2 wt.%) in the baseline electrolyte, retaining 88 % of initial capacity as compared with 71 % for the cell with the baseline electrolyte at 1 C after 200 cycles. Even at a high rate of 10 C, the cell with TMBDSA delivers a high capacity of 140.2 mAh/g and outstanding cycling stability at high temperatures of 55 °C. The surface analysis and density functional theory calculation reveal that TMBDSA is oxidized prior to the carbonate components in the electrolyte to form a protective interphase layer on the cathode surface. In addition, TMBDSA can significantly suppress the hydrolysis of LiPF 6 and the dissolution of transition metal ions (Ni, Co, and Mn) owing to the acid scavenging function of tertiary amine moiety. All the results demonstrate that TMBDSA can be potentially used as an efficient electrolyte additive for improving the cycling life of high energy density lithium‐ion batteries using nickel‐rich NCM811 cathode.