Thermally welded fluorine-rich hybrid interface enables high-performance sulfide-based all-solid-state lithium batteries

The demand for high energy density and safety has significantly promoted the development of all-solid-state lithium metal batteries. However, their practical use has been limited by the solid-solid interface and thermodynamic stability between lithium metal and solid electrolytes (SEs). Here, we constructed a hybrid interface via a thermal welding strategy to achieve stable cycling. Specifically, a dense and robust AlF 3 interface layer was constructed on the surface of the lithium metal via pressing and heat treatment. The lithiation products Li-Al alloy and LiF can effectively improve the interface contact and inhibit the growth of lithium dendrites. As a result, the critical current density (CCD) of the Li/Li symmetric cell significantly improved from 0.8 to 3.3 mA cm −2 , and the cycling life was dramatically increased to 6000 h at a high current density of 0.4 mA cm −2 . Moreover, the hybrid interface enabled stable cycling of both Li/Li symmetric and LiNi 0.6 Mn 0.2 Co 0.2 O 2 /Li cells even at high current densities. The modified layer material had been diversified to SnF 2 , ZnF 2 , and MgF 2 , thus supporting the general concept of thermal activation strategy. Such a design can be extended to other solid-state devices for better functioning and extended cycle life.