Li₃N-Modified Garnet Electrolyte for All-Solid-State Lithium Metal Batteries Operated at 40 °C

Lithium carbonate on the surface of garnet blocks Li⁺ conduction and causes a huge interfacial resistance between the garnet and electrode. To solve this problem, this study presents an effective strategy to reduce significantly the interfacial resistance by replacing Li₂CO₃ with Li ion conducting Li₃N. Compared to the surface Li₂CO₃ on garnet, Li₃N is not only a good Li⁺ conductor but also offers a good wettability with both the garnet surface and a lithium metal anode. In addition, the introduction of a Li₃N layer not only enables a stable contact between the Li anode and garnet electrolyte but also prevents the direct reduction of garnet by Li metal over a long cycle life. As a result, a symmetric lithium cell with this Li₃N-modified garnet exhibits an ultralow overpotential and stable plating/stripping cyclability without lithium dendrite growth at room temperature. Moreover, an all-solid-state Li/LiFePO₄ battery with a Li₃N-modified garnet also displays high cycling efficiency and stability over 300 cycles even at a temperature of 40 °C.