Stable lithium metal anode enabled by an artificial multi-phase composite protective film

High theoretical specific capacity and low electrochemical potential offered by lithium metal make it the definitive anode material for lithium batteries. Yet, unrelenting growth of dendrites forestalls the use of Li metal anode in commercial applications. To overcome this issue, we demonstrate the formation of a multi-phase composite protective layer consists of LixSi alloy, Si-linked organic oligomers and LiCl on the lithium anode surface. Due to its inherent ionic conductivity and chemical stability, the composite film can not only inhibit the formation of lithium dendrites by facilitating uniform Li-ion distribution, but also prevent unfavorable side reactions. The improved electrochemical performance is demonstrated by symmetric cells with the composite layer cycling at 1  mA cm−2 stably for 2200 h. Protected lithium anode coupled with LiFePO4 achieves high rate performance and better capacity retention after 400 cycles at 1C. Furthermore, cells with protected lithium anode and Li4Ti5O12 cathode (high areal loading of 14.9 mg cm−2) shows 91% capacity retention after 400 cycles at 0.5 C. The effective and scalable way to stabilize lithium anode with the multi-phase composite protective layer may serve as good references for development of advanced lithium metal batteries.