Y-shaped PCL-PLA copolymer-based all-solid electrolyte with enhanced Li ion conduction and stable cycling performance

Abstract

In recent years, solid polymer electrolytes (SPEs) have attracted much attention because of their good safety, good thermal stability and environmental stability. In this study, PLA-DMPA was synthesized by amidation after terminal group modification of PLA. A Y-shaped poly(ε-caprolactone)-poly(l-lactide) (Y-PCL-PLA) copolymer was delicately tailored by ring-opening copolymerization of PLA-DMPA and the ε-CL monomer, and the utilization rate of the terminal group (-DMPA) reached 83.7%. The Y-shaped structure can effectively decrease the crystallinity of PCL by 18.3%, improve the molecular chain movement ability and enhance the mechanical properties at high temperature. LFP/Y-PCL-PLA/Li batteries exhibit high ionic conductivity (1.64 × 10−4 S cm−1 at 60 °C), a wide electrochemical stability window (∼5.65 V), and a high lithium ion transfer number (tLi+ = 0.72). At 0.5C, the LFP/Y-PCL-PLA/Li battery can maintain a long-term stable cycle of 500 cycles, and the Coulombic efficiency is maintained above 99.7%. The discharge capacity is high (132 mAh g−1), the capacity retention rate can reach 75.8%, and the polarization voltage is very small (0.08 V). These data illustrate the excellent performance of Y-PCL-PLA as an all-solid electrolyte.