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

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.