In Situ Formed Protective Layer: Toward a More Stable Interface between the Lithium Metal Anode and Li₆PS₅Cl Solid Electrolyte

Due to the advantages of high safety and high energy density, solid-state lithium batteries (SSLBs) are promising competitors for next-generation batteries. Unfortunately, the growth of Li dendrites and irreversible capacity loss caused by the Li metal anode/solid electrolyte interfacial incompatibility remain challenges. Herein, an in situ formed artificial protective layer between the lithium metal anode and solid electrolyte Li6PS5Cl (LPSC) is introduced. A stable solid electrolyte interface (SEI) is in situ formed in the Li/Li6PS5Cl interface via the electrochemical reduction of the liquid electrolyte LiTFSI/tetraethylene glycol dimethyl ether (Li(G4)TFSI), which is beneficial for the improvement of the stability of interfacial chemistry and homogeneous lithium deposition behavior. The assembled Li/Li(G4)TFSI-assisted Li6PS5Cl/Li symmetric cells enable stable cycles for 850 and 400 h at a current density of 0.1 and 0.2 mA/cm2, respectively. Moreover, the LiNi0.6Co0.1Mn0.3O2(NCM613)/Li(G4)TFSI-assisted Li6PS5Cl/Li SSLBs can achieve prominent cycling stability at room temperature. This work provides a new insight into the interfacial modification to design SSLBs with high energy density.