Conductive gel composite cathodes with high mass loading of active oxides for high-performance solid-state lithium metal batteries

Solid-state lithium (Li) metal batteries with enhanced safety and high energy density have attracted ever-increasing attention. However, it is challenging to construct an effective ionic conduction pathway in the composite cathode of the solid-state batteries, especially when the mass loading of active materials is high. Herein, we prepare a gel composite cathode by introducing an in-situ polymerized gel polymer electrolyte into the cathode. The voids in the cathode and the gaps between the cathode and the electrolyte layer are filled with the gel electrolyte, and thus a fast Li-ion conduction pathway is established. Solid-state Li metal batteries with LiCoO₂ and LiFePO₄-based gel composite cathodes show excellent cycling performance. Even at a high mass loading of 11.09 mg cm⁻², the cell with a LiCoO₂–based gel composite cathode has a long cycle life at 0.088 mA cm⁻² at room temperature. The experimental data demonstrate that the conductive gel composite cathode has promising applications in solid-state batteries with high energy density.