A 3D Network Based on Poly(ε-caprolactone) Macromonomers as Polymer Electrolyte for Solid State Lithium Metal Batteries

Abstract

A commercial low molecular weight poly( ε -caprolactone) was chain-extended with acrylate moieties to create a macromonomer, which was then polymerized by radical reaction in the presence of different amounts of lithium bis(trifluoromethanesulfonyl)imide, LiTFSI, to obtain a 3D network Solid Polymer Electrolyte (SPE). The SPE with the largest ionic conductivity (24 μ S cm −1 at 50 °C) had a high transference number of 0.78 and could form a self-standing film. Lithium Iron Phosphate (LFP)/SPE/Li cells made with this SPE attained a specific capacity of 120 mA.h.g −1 . At 50 °C, the initial capacity declined by less than 15% after 150 cycles at 0.2 C. No evidence of degradation and dendrite growth was observed, indicating that the 3D network was stable. Thus, caprolactone-based 3D networks are promising materials for the fabrication of all solid-state batteries with high stability and cyclability, at near room temperature.