2D VOPO₄ Pseudocapacitive Ultrafast‐Charging Cathode with Multi‐Electron Chemistry for High‐Energy and High‐Power Solid‐State Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) are acknowledged to be one major direction for next‐generation energy storage devices. However, the practical applications of LMBs are certainly limited by the low power density and safety issues owing to the lack of high‐capacity pseudocapacitive cathode materials and solid electrolytes. Herein, the rational synthesis of 2D VOPO₄ nanosheets with enriched V⁴⁺ defects (VOPO₄@G‐Air) enabling ultrafast multi‐electron reactions as a high‐capacity pseudocapacitive cathode is reported. Through V⁴⁺ defect engineering, the larger polarizationand inhomogeneous multi‐electron reactions are vastly improved, resulting in remarkably fast kinetics. Benefiting from the ultrathin 2D structure and controllably regulated V⁴⁺ defect concentration, a high discharge capacity of 313 mA h g⁻¹at 0.1C is achieved, anda large capacity of 116 mA h g⁻¹ is offered at 50C. Finally, utilizing the as‐synthesized VOPO₄@G‐Air and a solid‐state electrolyte based on ethoxylated trimethylolpropane triacrylate (ETPTA‐LiClO₄‐SSE) , the assembled solid‐state LMBs (Li||ETPTA‐LiClO₄‐SSE||VOPO₄) show high energy density of 85.4 Wh kg⁻¹ at 114.5 W kg⁻¹ and high power density of 2.3 kW kg⁻¹ at 45.86 Wh kg⁻¹. Further, the pouch cell unveils extraordinary safety and excellent flexibility. This work provides new insights in the construction of ultrafast and high‐capacity pseudocapacitive cathodes with multi‐electron reactions for solid‐state LMBs.