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Capacity of layered lithium nickel-cobalt-manganese oxide () cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. , but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.

Lithium diffusivity of the silicon (Si)-based materials of Si-Cu and SiO x (x = 0.4, 0.85) withimproved interfacial stability to electrolyte have been determined, using variable rate cyclic vol-tammetry with film model electrodes. Lithium diffusivity is found to depend on the intrinsic prop-erties of anode material and electrolyte; the fraction of oxygen for SiO x (x = 0.4, 0.85), which isdirectly related to electrical conductivity, and the electrolyte type with different ionic conductivityand viscosity, carbonate-based liquid electrolyte or ionic liquid-based electrolyte, affect the lithiumdiffusivity. Keywords : Rechargeable lithium batteries, Si-based anode, Lithium diffusivity, Film model electrode ( Received September 23, 2013 : Accepted October 7, 2013) 1. Introduction There is an increasing need of high-energyrechargeable lithium batteries for their applications toelectric vehicles and stationary energy storage gridsystems. This represents the development need ofhigher capacity anode materials, and higher capacityand higher voltage cathode materials with a stablecycling ability and safer characteristics than the con-ventional ones.

Structural volume change occurring on the Si-based anode battery materials during alloying/dealloying with lithium is noticed to be a major drawback responsible for a limited cycle life. Silicon monoxide has been reported to show relatively improved cycling performance compared to Si-containing materials for rechargeable lithium batteries, due to the structural buff- ering role of in-situ formed Li2O and lithium silicate during the reaction of silicon monoxide and lithium. Here we report improved cycling ability of interfacially stabilized Si-SiO2-graphite composite anode using silane-based electrolyte additive for rechargeable lithium batteries, which includes low cost silicon dioxide for structural stabilization and graphite for enhanced conduc- tivity.