Extensively Reducing Interfacial Resistance by the Ultrathin Pt Layer between the Garnet-Type Solid-State Electrolyte and Li–Metal Anode

All-solid-state Li-ion batteries (ASSLIBs), also known as next-generation batteries, have attracted much attention due to their high energy density and safety. The best advantage of ASSLIBs is the Li–metal anodes that could be used without safety issues. In this study, a highly conductive garnet solid electrolyte (Li6.75La3Zr1.75Ta0.25O12, LLZTO) was used in the ASSLIB, and a Pt film was used to modify the surface of LLZTO to prove the solution of the Li–metal anode for LLZTO. Li–Pt alloy was synthesized to improve the wettability and contact of the interface. The interfacial resistance was reduced by 21 times, at only 9 Ω cm2. The symmetric cell could stably cycle over 3500 h at a current density of 0.1 mA cm–2. The full cell of Li|Li–Pt|LLZTO|LiFePO4 and Li|Li–Pt|LLZTO|LiMn0.8Fe0.2PO4 achieved high stability in terms of battery performance. Point-to-point contact transformed into homogeneous surface contact made the Li-ion flux faster and more stable. This surface modification method could provide researchers with a new choice for fixing interface issues and promoting the application of high-performance ASSLIBs in the future.