Electrode/Electrolyte Interface Enhanced by Carbonate-Based Copolymer as a Cathode Binder and in Situ Cross-Linking for Electrolyte

Abstract

Achieving good compatibility and physical contact between the electrode and solid-electrolyte interface in solid-state lithium–metal batteries (SSLMBs) remains a significant challenge. The polymer binder in a composite electrode is essential for establishing the ionic pathway between the electrode and the solid-electrolyte interface in SSLMBs. Consequently, conductive polymer binders are expected to enhance ionic migration more effectively than nonconductive polymer binders. Here, we report a CO₂-derived cross-linked copolymer (CP) as an ion-conductive cathode binder to reduce the resistance of the electrode/electrolyte interface. We further increase the compatibility of the electrode/electrolyte interface by an in situ cross-linking of solid polymer electrolyte (SPE). The in situ CP-SPE cell with the cathode using a CP-based polymer binder (Li/in situ CP-SPE/LFP@CP8) exhibited excellent initial discharge capacity as high as 143 mA h g^–1 at a C/5 rate. Moreover, the SEM images suggest that the cathode after cycles of the Li/in situ CP-SPE/LFP@CP8 cell has a smooth surface without any cracks, while the Li/CP-SPE/LFP@CP8 cell shows some cracks on the surface and active material detached from the aluminum (Al) current collector. The proper combination of CP-based cathode binder and the in situ cross-linking strategy enhances the electrode/electrolyte interfaces and increases the adhesion of the composite cathode materials.