Ethylene Carbonate Grafted Polysilane with Different Substitutions: A New Series of Electrolyte Additives to Improve High-Temperature Performance of Lithium-Ion Batteries

Abstract

A series of ethylene carbonate grafted polysilane with different substitutions are synthesized and used as novel electrolyte additives to improve high temperature performance of lithium-ion batteries. The relationship between Si-H substitution of polysilane and electrochemical performances are studied by cyclic voltammetry and charge-discharge cycling tests. Surface analysis on the cycled positive electrode is carried out by X-ray photoelectron spectroscopy, and then two possible protection mechanism of ethylene carbonate grafted polysilane is presented. Results show that cycling performance at elevated temperature (60 oC) could be significantly improved by adding a tiny amount (0.5 wt%) of grafting polysilane additives which could be exhausted and removed from electrolyte at the end of the film-forming process on positive electrode. When ethyl ethylene carbonate grafting polysilane with low substitution below 10 %, oxidation crosslinking of silicon hydrogen bond becomes main film-formation mechanism, whi...