Ultra-fine surface solid-state electrolytes for long cycle life all-solid-state lithium–air batteries

Solid-state electrolytes (SSEs) are potential candidates for developing high-energy-density and safe all-solid-state lithium (Li)-metal batteries due to the elimination of most of the safety issues encountered with liquid electrolytes. However, unfortunately, dangerous Li dendrites still form in SSEs. Herein, we report a simple nano-polishing method to prepare a high-performance all-solid-sate Li–air battery that consists of an air cathode, Li metal anode and ultra-fine surface Li1.5Al0.5Ge1.5P3O12 (LAGP) electrolyte. Such a design effectively reduces the interface impedance of the battery and meanwhile creates an ultra-smooth/flat interface between the Li metal and LAGP electrolyte that can produce a uniform electric field across the interface, thus enabling a homogeneous metal Li-forming/deforming environment during discharge/charge processes. As a result, a long cycle life all-solid-state Li–air battery has been obtained at room temperature at 400 mA g−1 with a capacity limitation of 1000 mA h g−1. The experimental results reveal that Li dendrites are suppressed through eliminating protrusion-induced locally concentrated free electron density on the surface of Li metal. The present ultra-fine interface engineering may be robust enough to suppress Li-dendrites, providing new insights into the interface between the Li-metal and SSE to develop future all solid-state Li-metal batteries.