In Situ Gas Analysis of Li₄Ti₅O₁₂Based Electrodes at Elevated Temperatures

Abstract

In Li-ion batteries, Li₄Ti₅O₁₂ (LTO) has merits of an excellent cycling stability combined with a safe working potential of 1.55 V vs. Li⁺/Li at which no adverse side-reactions with the electrolyte are expected. Concerns regarding gassing of LTO, especially at elevated temperatures, have however recently been reported. In this work, LTO gassing behavior at 50°C is investigated by in situ pressure and online electrochemical mass spectrometry (OEMS), allowing for both qualitative and quantitative analysis of evolving gases. H₂, C₂H₄, and CO₂ are the dominantly evolving gases for ethylene carbonate (EC) based electrolytes. H2 is mainly produced during the first charge step, while C₂H₄ is observed at lower potentials resulting from the reduction of EC. CO₂ evolution mechanism is complex and is promoted at more anodic potentials. Passivating the LTO surface, e.g. by a proper coating, and/or exchanging the LiPF₆ salt, may effectively reduce gas evolution, thus clearing the way for future use of LTO in energy storage applications at elevated temperatures.