Electrochemical Performance of a Potassium‐Ion Complex Gel Electrolyte with Succinonitrile Embedded in an In Situ Constructed 3D Polymer Framework

Abstract Potassium‐ion batteries (PIBs) represent an emerging energy storage technology, yet their widespread adoption is hindered by the inherent safety risks associated with conventional organic liquid electrolytes. To mitigate these challenges, a composite gel polymer electrolyte (SN@PPE‐X) is synthesized by incorporating the plastic‐crystal material succinonitrile (SN) into a rigid 3D confined polymer network. This is achieved through the in situ photopolymerization of pentaerythritol tetraacrylate (PETEA) after mixing SN with the monomer, forming a rigid framework that restricts SN mobility. The integration of SN enhances K⁺ dissociation from potassium salts, thereby elevating ionic concentration and improving ionic conductivity (1.30 × 10⁻ ³ S cm⁻¹) and transference number (0.72). Furthermore, the 3D polymer matrix confines SN, stabilizing the interface between SN@PPE‐2 and potassium metal. When applied in PIBs, SN@PPE‐2 demonstrates a capacity retention of 62% over 350 cycles at 50 mA g⁻¹, attributed to the rigid framework's ability to suppress cathode structural deformation, minimize parasitic reactions, and enhance rate performance. This gel electrolyte combines facile synthesis, cost‐effectiveness, and scalability, underscoring its potential for industrial implementation.