Garnet-type solid-state electrolytes (SSEs) are very promising due to their high ionic conductivities at room temperature and high stability against Li metal. However, the poor garnet/Li interfacial contact caused by Li2CO3 surface contaminant can lead to lithium dendrite growth and the performance decay of solid-state batteries (SSBs), which still hinders their practical application. Herein, a universal and simple method of rapid acid treatment is proposed to perfectly remove the surface Li2CO3 and retrieve a lithiophilic SSE surface. The SSE/Li interfacial resistance dramatically decreases from 940 Ω cm2 to 26 Ω cm2 at 30 °C. The acid treated garnet-SSE pellets exhibit an interfacial resistance comparable to the pellets with various surface coatings. In addition, the intrinsic garnet/Li interface remains stable during cycling, which enables the Li symmetric cells continuously cycle over 700 h under 0.2 mA cm−2 at 30 °C. And the LiFePO4/Li and LiCoO2/Li cells with acid treated garnet-SSE show excellent cycle and rate performances after eliminating the surface contaminant. These results indicate that rapid acid treatment not only guides a new understanding for an intrinsic garnet/Li interface but also is a simple and high-efficiency strategy to well address the interfacial issue for SSBs.

In-situ formed Li2CO3-free garnet/Li interface by rapid acid treatment for dendrite-free solid-state batteries