Robust All-Solid-State Lithium Metal Batteries Enabled by a Composite Lithium Anode with Improved Bulk Li Diffusion Kinetics Properties

All-solid-state batteries (ASSBs) with a Li metal anode are expected to be one of the most promising energy storage systems to achieve high energy density. However, the interfacial instability between the Li metal anode and solid-state electrolyte (SSE) limits the rate capability and cycling stability of ASSBs. The main issue is the formation of voids at the Li/SSE interface during Li stripping due to the slow diffusion of Li within the bulk Li metal, then increasing internal cell resistance and inducing the formation of lithium dendrites. To address these issues, a composite Li anode (LAO) composed by Li-Ag alloy and Li₂O is constructed by mixing the stoichiometric metal Li and Ag₂O directly. LAO anode is capable of improving bulk Li diffusion kinetics and inhibiting the formation of interfacial voids effectively, achieving a high critical current density over 1.5 mA cm^-2 and long stable cycling over 1000 h at 1 mA cm^-2. The ASSBs, employing LAO as the anode, Li₆PS₅Cl as the SSE, and LiCoO₂ as the cathode, exhibit superior rate capability and stable cycling over 4000 cycles at 5 C. Moreover, ASSBs can operate stably with a high LiCoO₂ loading of 17.8 mg cm^-2 for more than 100 cycles at 0.2 C.