Batteries consisting of Li₄Ti₅O₁₂ (LTO) anodes do not require the formation of a solid electrolyte interface to deliver robust high-rate performance at room temperature, however performance suffers at elevated temperatures due to gassing. Research has linked this gassing to the instability of the electrolyte on the surface of charged LTO at elevated temperatures. If this is the case a passivation layer that prevents the electrolyte from coming into contact with the charged surface of LTO should hinder gassing. Several classes of electrolyte additives have been investigated in Li₄Ti₅O₁₂/LiMn₂O₄ coin cells and pouch cells. ATR-FTIR and X-ray photoelectron spectroscopy has been used to gain an understanding of the surface films formed with different additives while in-situ gas measurements based on Archimedes’ principle and gas chromatography have given insight into how the implementation of these additives affects gassing. The results from this study enable the selective design of surface films for LTO anodes, which impedes gassing at elevated temperatures without sacrificing performance.