Exploring High Li+ Transference Number Solid-State Electrolytes Based on a Poly(ε-caprolactone) Polymer Matrix with Efficient Lithium Salt Dissociation for Applications in Lithium-Metal Batteries

Composite polymer electrolytes (CPEs) with high security and mechanical flexibility are needed for all-solid-state lithium-metal batteries (LMBs). However, their practical application is hindered by the increasing demand for high-power and high-areal-energy-density storage solutions. Herein, a high-powered CPE relying on poly­(ε-caprolactone) (PCL) as the polymer matrix is developed. The binding energy of Li+-PCL is predicted to be −130.163 kcal·mol–1 via density functional theory calculations, which implies a high dissociation of Li salts in the PCL matrix. The weak interactions between the Li+ and the polymer chains enable the CPEs with a high Li+ transfer number (t Li+) of 0.71. Besides, LiFePO4//Li batteries deliver a high capacity retention of 85% for over 600 cycles at 2.0C. This work demonstrates the tremendous potential of PCL-based CPEs in promoting the application of high-power-performance LMBs.