Considering the lower room temperature ionic conductivity, Li-ion transference number, and narrow electrochemical stability window in all-solid-state polymer electrolytes (ASSPEs)-based lithium metal batteries (LMBs), it is of particular necessity to find plausible strategies to accomplish these issues. In this paper, poly­(ε-caprolactone-co-1,5-dioxepan-2-one) (PDCL)-based poly­(ether-ester) ASSPEs have been successfully fabricated by the random ring-opening polymerization of cyclic CL and DXO. The PDCL-SPE exhibits a high ion conductivity of 3.54 × 10–5 S cm–1 at 30 °C with a high Li-ion transference number (0.62) and a superior electrochemical stability (5.1 V). FT-IR spectra confirm the synergistic effect of ether and carbonyl of ester from the main chain of PDCL, which is superior to the dissociation of lithium salts and facilitation the motivation of lithium ions. Furthermore, the assembled LiFePO4/PDCL-SPE/Li batteries displayed low interfacial resistance, Li dendrite suppression, high specific capacity, and excellent cyclic performance (capacity retention of 85% after 200 cycles at 0.1 C). The high-voltage LiNi0.5Co0.2Mn0.3O2/PDCL-SPE/Li batteries also exhibits good cycling performance and durability.