Synthesis and Ring-Opening Polymerization of Functional Silacyclobutane Derivatives and Their Application to Lithium Ion Batteries

摘要

Polycarbosilanes, which have a carbon-silicone backbone, are highly flexible polymers with excellent thermal, chemical, and electrical stability. They can be readily prepared by ring-opening polymerization of silacyclobutane derivatives. Although polysilacycobutanes are non-polar in general, they can be compatible to carbonate-based electrolyte solutions by introducing a 5-membered cyclic carbonate structure as a pendant group, and if properly designed they can be promising candidates as gelators to prepare gel polymer electrolytes (GPE). We designed a new carbosilane-based GPE system, which could be prepared by ringopening polymerization of a silacyclobutane having a 5-membered cyclic carbonate structure, 4-{2-(1-methylsilacyclobutyl)}ethyl-1,3-dioxolane-2-one (SBMC). The GPEs were directly synthesized by copolymerization of the monomer with a crosslinker, 1,6-bis(1-methylsilacyclobutyl)hexane (HMBS), in situ of a battery electrolyte solution consisting of 1M LiPF6 in an ethylene carbonate (EC) / diethyl carbonate (DEC) mixed solvent. The obtained GPE showed relatively high ionic conductivity compared to usual liquid electrolytes, and the lithium ion batteries composed of this GPE showed charge/discharge performance as high as those composed of the usual liquid electrolyte.