3D cubic framework of fluoride perovskite SEI inducing uniform lithium deposition for air-stable and dendrite-free lithium metal anodes

High-capacity lithium metal batteries have attracted wide attention as the next-generation energy storage systems. However, lithium dendrite caused by uneven deposition is a primary obstacle that hinders practical application of lithium metal batteries. In this work, fluoride perovskite with 3D octahedron framework, is first utilized as artificial solid electrolyte interface (SEI) to induce uniform lithium deposition for air-stable and dendrite-free lithium metal anode. The stable perovskite KNiF3 protective layer separates lithium metal from air and electrolyte, not only increases the stability of Li metal electrode, but also improves the interface contact and Li ion conduction. As evidenced theoretically and experimentally, lithium ions can migrate through the space in 3D cubic framework of perovskite with a low energy barrier, achieving fast ions migration and homogeneous deposition. The symmetric cells protected by KNiF3 SEI deliver stable cycling over 3000 h at a high capacity of 4 mAh cm−2. Coupled with commercial LiFePO4 cathodes (LFP, 13.3 mg cm−2), LFP||Li-KNiF3 batteries show promoted cycling stability and rate capability, much better than the bare Li. This work uncovers the transport mechanism of Li+ within KNiF3 SEI, and provides an avenue to air-stable and dendrite-free lithium metal anodes.