Investigation on the Copolymer Electrolyte of Poly(1,3‐dioxolane‐co‐formaldehyde)

A series of copolymers are prepared via cationic ring‐opening polymerization with 1,3‐dioxolane (DOL) and trioxymethylene (TOM) as monomers. The crystallization behaviors of the copolymers can be suppressed by adjusting the ratio of DOL/TOM. With LiBF 4 as a source for a BF 3 initiator, copolymer electrolytes (CPEs) can be prepared in situ inside cells without needing nonelectrolyte catalysts or initiators. The ionic conductivities and Li + diffusion coefficients () of the CPEs increase with a decreasing DOL/TOM ratio in a certain range. The CPE with a DOL/TOM ratio of 8/2 has the highest ionic conductivity as well as and shows excellent interfacial compatibility with lithium (Li) metal anodes. Li–Li symmetric cells can be uniformly plated/stripped for more than 1200 h. Furthermore, LiFePO 4 –Li cells with 8/2‐CPE display stable cycling performance for over 400 cycles. This strategy is a promising approach for the preparation of high‐performance polymer electrolytes and is sure to promote their application in Li metal batteries.