Realization of Ultra-Low Interfacial Impedance for Garnet-Based Solid State Battery via In-Situ Construction of Li–Ag Alloy Anode

Garnet-based solid–state lithium metal batteries (SSLMBs) are promising candidates for next-generation rechargeable batteries owing to their high energy density and safety. Nonetheless, SSLMBs face the challenges of high interfacial impedance and Li dendrite growth. To overcome these challenges, we propose a simple effective in situ construction of Li alloy anode strategy, in which Ag is introduced into molten Li to compose the Li–Ag alloy anode. This strategy creates a tight and continuous interface between Li–Ag alloy and LLZTO, achieving an ultralow interfacial impedance of 2.8 Ω·cm2. Moreover, the Li–Ag alloy framework established during Li plating and stripping provides migration pathways for Li atoms, effectively preventing dendrite growth and anode interface degradation. Consequently, the Li–Ag/LLZTO/Li–Ag symmetric cell attained a critical current density of 1.5 mA/cm2, and completed 1000 cycles at 0.5 mA/cm2 without significant polarization. Additionally, the Li–Ag/LLZTO/LiFePO4 full cell also delivers excellent electrochemical performance. This work presents an innovative strategy to design high-performance garnet-based SSLMBs.