Regulated Lithium Plating and Stripping by a Nano-Scale Gradient Inorganic-Organic Coating for Stable Lithium Metal Anodes

An intrinsic challenge of Li metal anode (LMA) that hinders its application is the formation of unstable solid electrolyte interphase (SEI), which causes uncontrollable Li plating/stripping and deteriorates the cycling stability. While it is desirable to fabricate a robust artificial SEI to stabilize Li, it remains highly challenging to manipulate the composition of the protective film with a high precision. Herein, we report a functional ‘gradient coating’ of mechanically enhanced hybrid inorganic-organic polyurea achieved by molecular layer deposition (MLD) for highly stable LMAs. The electrically insulating polymer on the coating surface can confine the electro-deposition of Li and tolerate the volume change due to its good flexibility, while the inner inorganic lithiophilic sites can effectively facilitate and regulate uniform Li nucleation and deposition. Owing to this elaborate interphase design, the protected Li can extend the cycling life significantly at a high current of 6 mA cm-2. Furthermore, as a proof of concept for application in Li metal batteries (LMBs), stable cycling for over 1500 hours in Li-O2 batteries was achieved. This work demonstrates an innovative nano-scale protective film design for LMAs and creates new opportunities for the realization of high performance next-generation batteries.