Understanding the mechanism of cycling degradation and novel strategy to stabilize the cycling performance of graphite/LiCoO2 battery at high voltage

Interest in wide-operating-voltage lithium-ion batteries is thriving because higher energy density can be enabled by employing higher-voltage cathodes and robust, stable electrolyte system. However, the severe solubilization of cobalt occurred at high cut-off voltage leads to rapid capacity degradation and limited lifespan. Here, we show that 1,3,2-dioxathiolane-2,2-dioxide as electrolyte additive has strong complexation ability to cobalt ions, which can inhibit the direct attack on solid electrolyte interphase films. Through calculation, the additive was proven to possess more negative lowest unoccupied molecular orbital energy than well-studied ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, which facilitates the reduction to form a protective film easily. As results, the LiCoO2/graphite pouch cells with 2 wt% additive cycled at 1C between 3.0 and 4.45 V exhibit significantly enhanced performance: the capacity outputs increases from 160.5 mAh g(-1) to 172.2 mAh g(-1 )and capacity retention after 200 cycles from 58.1% to 89.4%. Further development of the 1,3,2-dioxathiolane-2,2-dioxide as an electrolyte additive is a promising step towards high voltage stable electrolyte and high energy density lithium ion battery. (C) 2019 Elsevier B.V. All rights reserved.