Recent progress on flexible lithium metal batteries: Composite lithium metal anodes and solid-state electrolytes

Recently, flexible lithium metal batteries (LMBs) are considered as a promising power source for next-generation flexible and wearable electronic devices due to their high energy densities. However, the usage of metallic Li anodes inevitably causes safety risk due to the growth of Li dendrites. In this review, we summarized the recent research progresses on flexible LMBs, with specific emphasis on the design of composite Li metal anodes and solid-state electrolytes with high flexibility and safety. We begin with a brief introduction of flexible LMBs and the associated anodes and electrolytes. Then, the preparation of flexible composite Li metal anodes has been described in detail, with the evolution from the conventional electrodeposition method to thermal infusion and mechanical rolling methods. For solid-state electrolytes, the advanced progress on shapeable ceramic, polymer, and hybrid electrolytes have been introduced. We also presented comprehensive summaries on high-energy-density flexible LMBs, including flexible lithium-sulfur batteries and lithium-oxygen batteries. Finally, we proposed the future trends, challenges, and prospects toward the practical applications of advanced flexible LMBs.