An oxygen vacancy-rich ZnO layer on garnet electrolyte enables dendrite-free solid state lithium metal batteries

The huge interfacial resistance caused by Li2CO3 on garnet (LLZO) electrolyte and the lithium-dendrite growth through garnet greatly hinder the development of solid-state batteries (SSBs). Here, both the problems are simultaneously addressed through a general strategy of engineering garnet pellet with a layer of ZnO with oxygen vacancies (OV-ZnO). The OV-ZnO not only protects LLZO from being exposed to wet air, but also reacts spontaneously with lithium-metal to in-situ form an ionic conducting LixZnO interphase. The as-formed interphase improves the Li/LLZO contact, reduces the huge interface resistance caused by Li2CO3, suppresses the lithium-dendrite growth, and promotes the lithium transport between LLZO and Li-metal. As a result, an Li/Li symmetric cell with OV-ZnO coated LLZO pellet shows a low area specific resistance of 55 Ω cm2, a stable plating/stripping process for 200 h at a current density of 0.1 mA cm−2, and a record-high critical current density of 1.4 mA cm−2 ever reported at room temperature. Moreover, this approach of coating metal oxide with oxygen vacancies on garnet electrolytes has been extended to other metal oxides, such as copper oxide (OV-CuO), titanium dioxide (OV-TiO2) and indium oxide (OV-In2O3).