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 (∼1000 Ω cm 2 ) and uneven current distribution. In this work, the issue is effectively addressed by coating the garnet pellet with a SnO 2 nanolayer. Attributed to the lithiation reaction between the lithium metal and SnO 2 , an ion-conducting interlayer is generated automatically between the garnet and lithium metal, which reduces their interfacial resistance from 1019 to 153 Ω cm 2 . A Li | SnO 2 -garnet | 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 | SnO 2 -garnet | LiFePO 4 full battery test, the SnO 2 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. • SnO 2 nanofilm is coated on the garnet surface to address the Li/garnet interface issue • The Li/garnet interfacial resistance is reduced from 1019 to 153 Ω cm 2 • Stable lithium plating/stripping is achieved for more than 900 h at 0.2 mA cm −2 • A Li .| SnO 2 -garnet | LiFePO 4 full battery stably operates for over 100 cycles at 0.3 C