Stabilizing lithium metal anode by molecular beam epitaxy grown uniform and ultrathin bismuth film

Abstract Lithium metal anode is regarded as an attractive option for next-generation high-energy-density rechargeable batteries. However, the unstable solid-electrolyte interphases between lithium anode and electrolyte lead to uncontrolled growth of lithium dendrites. Herein, we describe the surface reconstruction of Li anode by molecular beam epitaxy deposition of an ultrathin and compact bismuth film. During Li plating process, the electrochemical active bismuth film is prone to form a close-knit lithiophilic lithium-bismuthide (LixBi) alloy layer through electrochemical alloying with lithium metal. Benefiting from its high ionic conductivity, lithiophilic characteristics, high chemical stability, good mechanical properties and air/moisture tolerance, the LixBi-rich layer efficiently inhibit the parasitic reactions between Li anode and electrolyte, and thus favor a dendrite-free Li plating/stripping process, as verified by electrochemical tests and in-depth analyses. Symmetric cells with Bi-coated Li electrodes show a stable and dendrite-free cycling behavior at 1.0 mAh cm−2 for 300 h and superior rate performance up to 5.0 mA cm−2. When Bi-coated lithium anodes are paired with a LiNi0.5Co0.2Mn0.3O2 cathode, a stable cycling life for over 300 cycles at 0.5C with a high capacity retention rate of 97% is obtained. This work provides new insights and strategies for the construction of Li-rich alloy layers on lithium metal surface via molecular beam epitaxy that enables dendrite-free and high-performance lithium metal batteries.