Toward efficient Li-ion cells at high temperatures: Example of TiSnSb material
Résumé
Developing efficient Li-ion cells with long lifetime for high temperature applications remains a challenging problem due to severe electrolyte degradation. Here, it is showed that superior lifetime, CE and polarization could be obtained at 60 °C compared to 25 °C when TiSnSb/Li coin cells filled with 1 M LiPF6 EC:PC:3DMC +5% FEC +1% VC electrolyte were used. To understand such unexpected phenomenon, a thorough correlation of the electrochemical performance with complementary gas chromatography coupled with electron impact mass spectrometry (GC/MS) and X-ray photoelectron spectroscopy (XPS) analysis was performed. XPS results showed the formation of a more stable and passivating SEI film at the TiSnSb electrode surface at 60 °C due to a specific reactivity of the electrolyte. In good agreement, the GC/MS analysis showed only a partial consumption/reactivity of the FEC/VC additives at 60 °C while a full consumption of the additives and a further degradation of the EC solvent were observed at 25 °C. As a whole, the XPS and GC/MS results allowed to identify the origin of the superior electrochemical performance of the TiSnSb/coin cells at 60 °C.