Cocktail Effects in Boosting the Interfacial Ionic Conduction of the Garnet Solid-State Battery

The garnet-type Li₇La₃Zr₂O₁₂ electrolyte has gained a lot of attention due to its nonflammability, high ionic conductivity, and thermodynamic stability against lithium anodes. However, the large-scale application of solid garnet electrolytes is restricted by high interfacial resistance due to the poor wettability of metallic lithium and interfacial voids caused by sluggish lithium-ion transport during plating/stripping. Herein, we propose a three-dimensional (3D) composite lithium anode with high ionic and electronic conductivity by introducing a small amount of carbonized ZIF-8 powder into molten lithium, achieving compact contact with remarkably low interfacial resistance of 15.2 Ω cm² due to the decreased surface tension of molten lithium. Aided by DFT calculations, we are able to confirm that the reaction products of Li₃N, Li₂O, Li-Zn alloy, and LiC₆ have much lower interfacial formation energies with garnet electrolytes compared to that of the pure lithium anode. The lithiophobic Li₃N and Li₂O could impede lithium dendrite growth, provide rapid ionic transport, and thus prevent garnet reduction. In addition, the lithiophilic Li-Zn alloy and LiC₆ accelerate lithium-ion migration, preventing the formation of voids at the interface. Thus, the so-called cocktail effects would occur to boost the electrochemical performance through synergistic interactions. The symmetric battery enabled with the composite lithium anode achieves an impressive CCD of 2.5 mA cm^-2 and stable galvanostatic cycling for 350 h without short-circuiting at 0.5 mA cm^-2. Moreover, the full cell paired with the LiFePO₄ cathode delivers excellent cycling performance (LiFePO₄, 86.2%@160th cycle@0.5 C). This article describes an integrated approach to develop safe and long-lasting solid-state batteries.