Ultra-stable lithium plating/stripping in garnet-based lithium-metal batteries enabled by a SnO2 nanolayer

Owing to its high ionic conductivity (10(-4) - 10(-3) S cm(-1)), excellent stability toward lithium and a wide electrochemical window, the garnet-type solid-state electrolyte has been regarded as one of the most promising solutions to the viability of lithium metal-based batteries. However, the poor interfacial contact between the garnet and the lithium metal leads to an ultrahigh interfacial resistance (similar to 1000 Omega cm(2)) and uneven current distribution. In this work, the issue is effectively addressed by coating the garnet pellet with a SnO2 nanolayer. Attributed to the lithiation reaction between the lithium metal and SnO2, an ion-conducting interlayer is generated automatically between the garnet and lithium metal, which reduces their interfacial resistance from 1019 to 153 Omega cm(2). A Li vertical bar SnO2-garnet vertical bar Li symmetric cell is then built and achieves a stable lithium plating/stripping for more than 900 h at 0.2 mA cm(-2) without short circuit. Moreover, in a Li vertical bar SnO2-garnet vertical bar LiFePO4 full battery test, the SnO2 nanolayer enables the full battery to be stably operated for over 100 cycles at 0.3 C with a capacity retention of 98.6%, whereas the control group using bare garnet is unable to work at this high rate.