Quantification of the Impact of Crosslinking on Ionic Conductivity and Electro-Chemo-Mechanical Properties of Poly(ethylene oxide)-Based Solid Polymer Electrolytes

Non-crosslinked poly(ethylene oxide) (PEO) is widely studied for its lithium-ion conductivity and applications as solid polymer electrolytes (SPEs) for lithium-metal-anode batteries (LMBs), but its mechanical softness remains a barrier to roll-to-roll manufacturing. Crosslinking in polymer synthesis can reinforce PEO-based SPEs by linking polymer chains into a three-dimensional network, making them compatible with roll-to-roll processing. Although crosslinking may reduce lithium-ion conductivity by limiting segmental motion, the resulting mechanical enhancement can suppress dendrite growth, improving the reversibility of lithium-metal anodes. Understanding the relationship between the degree of crosslinking, mechanical properties, glass transition temperature, ionic conductivity, and electrochemical reversibility in LMBs is therefore of fundamental importance. Here, we systematically quantify the impact of crosslinking on the ionic, electrochemical, and mechanical properties of PEO. The results indicate that higher crosslinking enhances SPEs’ mechanical strength but reduces ionic conductivity, consistent with the rise in glass transition temperature, supporting the theory that segmental motion governs lithium-ion conduction in PEO. Meanwhile, although crosslinking reduces the limiting current density, whereas the critical current density benefits from mechanical reinforcement of SPEs brought by crosslinking, thereby enhancing the reversibility of lithium-metal anodes. This work provides the opportunity to improve the electro-chemo-mechanical properties of PEO-based SPEs for LMBs.