Potential-Gated Polymer Integrates Reversible Ion Transport and Storage for solid-state Batteries.

The development of practical solid-state batteries is hindered by their high interfacial resistance and sluggish diffusion properties, primarily due to the heterogeneous interfaces between the solid electrolyte and the electrode. Here, an all-in-one polymer electrode-electrolyte material (P(EO2-S3)) is presented, which covalently integrates ethylene oxide groups for Li+ transport and trisulfide linkages for redox-active sites. This material exhibits favorable ionic conductivity as a solid electrolyte, while its reversible redox activity activates below 2.5 V versus Li⁺/Li, delivering a high reversible capacity of 491.7 mAh g-1. Leveraging P(EO2-S3) as both cathode and electrolyte, integrated cells (P(EO2-S3)@CP|P(EO2-S3)|Li) exhibit accelerated electrochemical kinetics while maintaining cycling stability in flexible devices over 20 000 bending cycles. As a redox-active catholyte of LiFePO4, P(EO2-S3) increases the capacity of the composite cathode to 358.3 mAh g-1 based on LiFePO4 mass, achieving an electrode energy density of 585.9 Wh kg-1. This work establishes a new paradigm for multifunctional polymers that integrates ion transport and storage, offering a versatile platform for flexible, high-energy solid-state batteries.