Highly Ion-Conducting Protective Layers with Nanomicro Engineering for High-Performance Lithium Metal Anodes

The utilization of the lithium (Li) metal as an anode material has generated significant interest in the development of next-generation Li rechargeable batteries. However, the occurrence of heterogeneous Li plating/stripping during cycling often leads to the formation of Li dendrites, which severely limits their further application. In this study, we report the successful fabrication of a nanomicro structure protective layer composed of core–shell-like Li2Sn5@LiCl particles, achieved through a simple replacement reaction of Li and SnCl4, followed by spontaneous alloying reactions. The protective layer has a core–shell structure, consisting of electron-conducting Li2Sn5 covered by ion-conducting LiCl layers, serving as a Li+ transport network and enabling fast Li+ diffusion to achieve a uniform deposition of Li. As a result, a dendrite-free Li metal anode is obtained, leading to greatly improved cycling stability. Remarkably, symmetrical cells employing treated Li electrodes with an optimized thickness of the protective layer (designated as Li@SL-30) exhibit stable cycling for more than 100 h at a current density of 3 mA cm–2 in a carbonate-based electrolyte. In contrast, symmetric cells employing bare Li electrodes display oscillated voltage after only 15 h of cycling. Furthermore, full cells utilizing Li@SL-30 anodes paired with lithium cobalt oxide (LCO) cathodes (≈15 mg cm–2) demonstrate superior cycling performance over 140 cycles with a high capacity retention of 96.4% at 0.2 C, indicating only 0.0257% capacity loss per cycle. Conversely, full cells employing bare Li anodes exhibit capacity retention of only 88.9% after 100 cycles, dropping to 132.5 mA h g–2. These results demonstrate the feasibility of this approach for the development of high-performance Li metal batteries.