Interface Manipulation of Composite Solid Polymer Electrolyte with Polydopamine to Construct Durable and Fast Li⁺ Conduction Pathways

Taking advantage of light weight, flexibility, and flame retardancy, solid polymer electrolytes (SPEs) provide a feasible solution to these safety concerns and to the enhancement of energy density for lithium-ion batteries (LIBs). However, the development of SPEs is still restricted by low ionic conductivity. Herein, we develop a type of SPE filler built by flower-like Co₃O₄ microspheres as a lithiophilic backbone and polydopamine (PDA) as a multifunctional coating for the engineering of the interphase properties of the polyether-based SPEs. The hierarchical structure of Co₃O₄ affords large interfacial contact area with SPEs and effectively suppresses the regular crystallinity of poly(ethylene oxide) (PEO) segments. Moreover, the PDA coating layers with diverse surface functionalities serve as a versatile mediator to finely tune ionic distribution and transport behavior via multiple Lewis acid-base interactions. We uncover the interphase characterizations and their synergistic effects to enhance Li⁺ conductivity and mechanical/electrochemical stability. This study provides intriguing alternatives for developing composite solid polymer electrolytes (CPEs), for which we further demonstrate the potential application of Co₃O₄@PDA-based CPEs in all-solid-state LIBs.