Clarification on the Gassing Behavior of Carbon-Coated Li₄Ti₅O₁₂ at Elevated Temperature: Importance of Coating Coverage

Lithium-ion batteries (LIBs) have become vital energy-storage devices in electric vehicles (EVs). Li₄Ti₅O₁₂ (LTO) is a promising material of LIB because of its high rate capability, cyclability, and safety compared to the graphite-based anode materials in commercial LIBs. However, one of the major concerns in LTO-based LIBs is gassing, which results from the interfacial reaction between LTO and organic electrolyte solutions, unlike the reduction decomposition of an electrolyte in graphite electrodes. Carbon coating on LTO has been proposed to mitigate the gassing by preventing such side reactions, even though reports have been conflicting. In this work, there are different kinds of carbon-coated LTO deposited using the thermal decomposition of ethanol that has been investigated at elevated temperature using In Operando pressure analysis to answer the paradox of the effect of carbon coating on the gassing behavior on LTO. Our Spatial Raman Spectroscopy Analysis (SRS) shows that the carbon coating coverage is likely responsible for the discrepancy in the gassing behavior reported by other studies. Our proposed deposition process achieves complete coverage with an ultrathin 3 nm carbon coating layer which mitigates the interfacial reactions while improving electrochemical performance.