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

Abstract

An oxygen vacancy-rich ZnO (Ov-ZnO) layer is deposited on garnet electrolyte, which not only remove the surfafical Li 2 CO 3 , but also in-situ forms an Li + -conductive Li x ZnO interphase. Li symmetric cells with this Ov-ZnO-coated garnet exhibit an ultralow cell resistance and a record-high critical current density of 1.4 mA cm −2 ever reported without lithium dendrite at room temperature. • A layer of ZnO with oxygen vacancies is coated on the surface of garnet electrolyte. • A low interfacial resistance of 55 Ω cm 2 is achieved without melting lithium. • The reaction mechanism of the interphase on garnet is investigated in detail. • The strategy can be extended to other metal oxides with oxygen vacancies. The huge interfacial resistance caused by Li 2 CO 3 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 (O V -ZnO). The O V -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 Li x ZnO interphase. The as-formed interphase improves the Li/LLZO contact, reduces the huge interface resistance caused by Li 2 CO 3 , suppresses the lithium-dendrite growth, and promotes the lithium transport between LLZO and Li-metal. As a result, an Li/Li symmetric cell with O V -ZnO coated LLZO pellet shows a low area specific resistance of 55 Ω cm 2 , 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 (O V -CuO), titanium dioxide (O V -TiO 2 ) and indium oxide (O V -In 2 O 3 ).