Oligo(ethylene oxide)-functionalized trialkoxysilanes as novel electrolytes for high-voltage lithium-ion batteries

Abstract

Oligo(ethylene oxide)-functionalized trialkoxysilanes were synthesized through hydrosilylation reaction by reacting trialkoxysilane with oligo(ethylene oxide) allyl methyl ether using PtO2 as a catalyst. The physical properties of these compounds, such as viscosity, dielectric constant, and ionic conductivity, were characterized. Among them, [3-(2-(2-methoxyethoxy)ethoxy)-propyl]triethoxysilane (TESM2) exhibited a commercial viable ionic conductivity of 1.14 mS cm−1 and a wide electrochemical window of 5.2 V. A preliminary investigation was conducted by using TESM2 as an electrolyte solvent for high-voltage applications in lithium-ion batteries. Using 1 M LiPF6 in TESM2 with 1 vol% vinyl carbonate as an electrolyte, LiCoO2/Li half-cell delivered a specific capacity of 153.9 mAh g−1 and 90 % capacity retention after 80 cycles (3.0–4.35 V, 28 mA g−1); Li1.2Ni0.2Mn0.6O2/Li4Ti5O12 full cell exhibited the initial capacity of 161.3 mAh g−1 and 86 % capacity retention after 30 cycles (0.5–3.1 V, 18 mA g−1).