Molecular-Level Insights into the Effect of Block Copolymer Architecture on PEO–PVDF Solid Polymer Electrolyte Properties

Solid polymer electrolytes (SPEs) have attracted significant attention in the development of lithium–ion batteries (LIBs), as they offer enhanced safety and stability compared with traditional liquid electrolytes. In this work, we employed molecular dynamics simulations to investigate the synergistic effect of the highly Li+ conductive poly(ethylene oxide) (PEO) and the mechanically strong poly(vinylidene fluoride) (PVDF) blocks on the properties of polymer electrolytes. The study focuses on the effect of block copolymer architecture on the phase morphology of polymer electrolytes, the coordination structure and mobility of Li+, and the mechanical properties in terms of tensile strength. The results show that Li+ mobility and tensile modulus of the block copolymer systems lie between those of PEO and PVDF homopolymers. Distinct phase separation between amorphous PEO and crystalline PVDF domains was observed in the block copolymer systems, particularly in triblock architectures. This separation enables the formation of a continuous PEO phase that supports enhanced Li+ transport, while the PVDF domains contribute to improved mechanical strength. Meanwhile, the graft copolymer systems show better mixing between PEO and PVDF units, disrupting the PEO phase continuity and resulting in reduced Li+ mobility. These findings highlight the influence of the block copolymer architecture on key properties of polymer electrolytes for LIBs and may guide the future design of improved SPE materials.