In Situ Formed Gradient Composite Solid Electrolyte Interphase Layer for Stable Lithium Metal Anodes.

Lithium (Li) metal anode (LMA) is highly considered as a desirable anode material for next-generation rechargeable batteries because of its high specific capacity and the lowest reduction potential. However, uncontrollable growth of Li dendrites, large volume change, and unstable interfaces between LMA and electrolyte hinder its practical application. Herein, a novel in situ formed artificial gradient composite solid electrolyte interphase (GCSEI) layer for highly stable LMAs is proposed. The inner rigid inorganics (Li S and LiF) with high Li ion affinity and high electron tunneling barrier are beneficial to achieve homogeneous Li plating, while the flexible polymers (poly(ethylene oxide) and poly(vinylidene fluoride)) on the surface of GCSEI layer can accommodate the volume change. Furthermore, the GCSEI layer demonstrates fast Li ion transport capability and increased Li ion diffusion kinetics. Accordingly, the modified LMA enables excellent cycling stability (over 1000 h at 3 mA cm ) in the symmetric cell using carbonate electrolyte, and the corresponding Li-GCSEI||LiNi Co Mn O full cell demonstrates 83.4% capacity retention after 500 cycles. This work offers a new strategy for the design of dendrite-free LMAs for practical applications.