Conductive Li2S-NbSe2 Cathode Material Capable of Bidirectional Self-Activation for High-Performance All-Solid-State Lithium Metal Batteries

All-solid-state lithium metal batteries (ASSLBs) offer an alternative route to safe and high energy density power sources. Sulfur-based cathodes with high theoretical specific capacity and low cost are crucial for advancing ASSLBs. However, the electronic insulation and sluggish kinetics of sulfide materials like Li 2 S severely limit battery performance. Herein, the strategy is proposed that a highly electronic conductive Li 2 S-NbSe 2 material enhances the electrochemical performance through bidirectional self-activation. The chemical interaction between Li 2 S and NbSe 2 induces NbSe 2-x S x and Li 2 Se derivatization, serving as the basis for activation. The carrier transport properties, chemical evolution and self-activation mechanism of Li 2 S-NbSe 2 during the oxidation–reduction process are revealed. The chemical activation of NbSe 2-x S x is explored to accelerate the electrochemical processes by modifying the conductivity of sulfur species and the conversion pathways without insulating Li 2 S and S aggregation. Therefore, ASSLBs using Li 2 S-NbSe 2 as cathode active material achieve an electrode-level energy density of 394 Wh kg −1 and a power density of 524 W kg −1 at 1 C (4.35 mA cm −2 ) and 25 °C. The capacity retention after 100 cycles at 0.5 C is ≈99.3% with almost no degradation. This work provides new options and insights for the rational design and development of chalcogenide cathode active materials for high-performance ASSLBs.