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.