Spherical Lithium Deposition Enables High Li‐Utilization Rate, Low Negative/Positive Ratio, and High Energy Density in Lithium Metal Batteries

Abstract

Abstract Lithium metal battery promises an attractively high energy density. A high Li‐utilization rate of Li metal anode is the prerequisite for the high energy density and avoiding a huge waste of the Li resource. However, the dendritic Li deposition gives rise to “dead Li” and parasitic interfacial reactions, resulting in a low Li utilization rate. Herein, Li deposition is regulated to spherical Li by designing an MXene host with an egg‐box structure, suitable curvature, and continuous gradient lithiophilic structure. Because the spherical Li greatly reduces the interfacial side reactions and avoids the formation of dead Li, the Li anode affords a high plating/stripping efficiency. Furthermore, the gradient lithiophilic design results in a bottom‐up growth of the spherical Li within the host, safely away from the separator. Thus, the spherical Li anode realizes a long life of >3000 h with a high Li‐utilization rate of >90%, stable cycling in full cells at an areal capacity up to 5 mAh cm −2 with a low negative/positive ratio of 0.8, which is critical for high energy density. Such spherical deposition highlights the critical role of the morphological control of alkali metals and provides a viable method to build practical high‐energy metal batteries.