Robust Nanoscale Anode Protective Layers toward Fast-Charge High-Energy-Density Lithium Metal Batteries

Mechanically stable and structurally homogeneous lithium-electrolyte interfacial layers are crucial in stabilizing lithium (Li) anodes for practical Li metal batteries. Herein, an ultrathin (≈84 nm) and robust artificial protective layer is constructed with reactive two-dimensional (2D) molecular brushes as building blocks. The artificial protective layer can in situ react with underlying Li metal to produce a nanoscale poly(lithium styrenesulfonate)-grafted graphene oxide (GO-g-PSSLi) layer on the outermost surface and an infinite Li-Ag solid solution in the anode. The nanoscale GO-g-PSSLi layer well integrates a large number of single Li-ion conducting PSSLi chains and 2D robust GO backbones, thereby enabling molecular-level homogeneous and fast Li-ion diffusion as well as remarkable mechanical strength. Meanwhile, the simultaneously formed Li-Ag solid solution is beneficial for rapid Li transport in the anode to reduce the Li nucleation barrier and facilitate homogeneous deposition of Li. With such artificial protective layers, a prototype pouch cell with a thin Li metal anode (50 µm) and a high-loading cathode (21.6 mg cm^-2) delivers an impressive cycle life of over 350 cycles with 69% capacity retention under harsh conditions. Remarkably, ultrahigh charging power density of 456 W kg^-1 and energy density of 325 Wh kg^-1 can be simultaneously achieved in an Ah-level pouch cell.