Block Copolymer Solid Battery Electrolyte with High Li-Ion Transference Number

Abstract

The electrochemical properties of a solid polymer electrolyte consisting of a diblock copolymer and lithium bis(oxalato)borate, LiBC4O8LiBC4O8 (LiBOB) salt, is reported. The spherical microphase-separated diblock copolymer is composed of a majority poly(ethylene oxide) (PEO) block and a minority random copolymer block of methyl methacrylate (MMA) and lithium salt of methacrylic acid (MAALi), PEO-b-(PMMA-ran-PMAALi)PEO-b-(PMMA-ran-PMAALi) . Salt-optimized electrolyte membranes of the diblock copolymer and LiBOB salt exhibited an average lithium-ion transference number (TLi+)(TLi+) value of 0.9 at room temperature (21–23°C)(21–23°C) . The solid-state flexible, translucent polymer electrolyte shows a wide electrochemical stability window and excellent interface properties with the lithium metal electrode. The combination of these properties makes these block copolymer membranes viable electrolyte candidates for flexible lithium-ion batteries.