Improving Thermal Stability of Si-Based Anodes for Lithium-Ion Batteries by Controlling Bulk and Surface Layer Compositions

Si-based anodes are promising candidates for next-generation lithium-ion batteries (LIBs). Apart from electrochemical performances, their thermal stability needs immediate attention as it relates to battery safety and commercialization. In this work, we use differential scanning calorimetry (DSC) to systematically compare the thermal behaviors of silicon (Si) and silicon monoxide (SiO) electrodes with different state of charge and electrolytes. It is possible to reduce heat generation not only by reducing the amount of lithiation but also with the incorporation of oxygen matrix in the material. Moreover, the existence of robust F-containing species on the electrode surface with the addition of fluoroethylene carbonate (FEC) into the electrolyte reduces reaction between electrolyte and active material, leading to lower heat generation. Though, larger amount of FEC results in more heat as FEC is more exothermic than ethylene carbonate. Better thermal stability of Si and SiO is achievable by optimizing the FEC content in the electrolyte.