Compositional Engineering of Lithium Metal Anode for High-Performance Garnet-Type Solid-State Lithium Battery

Garnet-type solid-state lithium batteries (SSLBs) possess excellent potential owing to their safety and high energy density. However, fundamental barriers are deficient cycling stability and poor rate capability. The main concern lies in generating voids at the Li|garnet interface during Li stripping, stemming from the sluggish diffusion of Li atoms inside the bulk Li metal. Herein, a composite anode (AN@Li) containing Li-Al alloy, Li₃N, and LiNO₂ is designed by introducing aluminum nitrate into molten Li. The lower interfacial formation energies exhibited by Li-Al alloy, Li₃N, and LiNO₂ with garnet solid-state electrolyte (SSE) enhance the wettability of AN@Li toward SSE. Meanwhile, it affords efficient conductive pathways that facilitate Li⁺ diffusion in the bulk anode (not just on the surface). Impressively, the resulting symmetric cell with AN@Li electrodes achieves high critical current density (1.95 mA cm^-2) and long cycle life (6000 h at 0.3 mA cm^-2). The SSLB coupled with LiFePO₄ cathode and AN@Li anode enables stable cycling for 200 cycles at a high rate of 1 C with a retention of 96% and exhibiting outstanding rate capability (145.9 mAh g^-1 at 2 C). This work provides practical insights for producing high-performance lithium metal anode for advanced garnet-type SSLBs.