Enhanced Regional Electric Potential Difference of Graphdiyne Through Asymmetric Substitution Strategy Boosts Li+ Migration in Composite Polymer Solid-State Electrolyte

Abstract

Low ionic conductivity is a major obstacle for polymer solid-state electrolytes. In response to this issue, a design concept of enhanced regional electric potential difference (EREPD) is proposed to modulate the interaction of nanofillers with other components in the composite polymer solid-state electrolytes (CPSEs). While ensuring the periodic structure of the graphdiyne (GDY) backbone, methoxy-substituted GDY (OGDY) is prepared by an asymmetric substitution strategy, which increases the electric potential differences within each repeating unit of GDY. The staggered distributed electron-rich regions and electron-deficient regions on the two-dimensional plane of OGDY increase the free Li⁺ concentration through Lewis acid–base pair interaction. The adjacent ERRs and EDRs form uniformly distributed EREPDs, creating a continuous potential gradient that synergistically facilitates the efficient migration of Li⁺. Impressively, the OGDY/poly(ethylene oxide) (PEO) exhibits a high ionic conductivity (1.1 × 10^–3 S cm⁻¹) and ion mobility number (0.71). In addition, the accelerated Li⁺ migration promotes the formation of uniform and dense SEI layers and inhibits the growth of lithium dendrites. As a proof of concept, Li||Li symmetric cell and Li||LiFePO₄ full cell and pouch cell assembled with OGDY/PEO exhibit good performance, highlighting the effectiveness of our EREPD design strategy for improving CPSEs performance.