Constructing a stable interface between the sulfide electrolyte and the Li metal anode: Via a Li⁺-conductive gel polymer interlayer

Due to high ionic conductivity, favorable mechanical plasticity, and non-flammable properties, inorganic sulfide solid electrolytes bring opportunities to the practical realization of rechargeable lithium-metal batteries with high energy, yet their use was impeded by an electrochemically unstable Li-electrolyte interface. Herein, we propose to address the issue via a Li+-conductive gel polymer interlayer, which is derived in situ from a conventional liquid ether electrolyte during the cell fabrication process. The gel polymer interlayer not only enables intimate solid-solid contact and uniform Li-ion flux at the heterointerface but also effectively inhibits interfacial reactions and Li dendrite growth. With improved interfacial stability, a Li-Li symmetric cell with the gel polymer interlayer demonstrates an ultra-stable Li plating/stripping performance of over 1300 hours at 0.1 mA cm-2 and 350 hours at 0.5 mA cm-2 at room temperature, and a high critical current density of >5 mA cm-2. This work offers general insights into a reasonable design of an anode/electrolyte interface for high-energy rechargeable Li-metal batteries.