Revealing the Micro-Size Effect in Alloy Anodes for High-Capacity and Long-Cycling Sulfide-Based Solid-State Batteries.

Solid-state batteries (SSBs) are competitive contenders for energy storage due to their inherent safety and high energy. However, the lack of an appropriate anode has hindered their development. Graphite and lithium metal are widely used anode materials, but graphite suffers from a low capacity, whereas lithium metal presents severe dendrite and reactivity challenges. Herein, the promising performance of micro-sized alloys is demonstrated as high-capacity and long-cycling anodes for SSBs. Using antimony as a model anode, its full theoretical capacity (660 mAh g), high-rate capability (3 A g), and long cycling life (1000-2000 cycles) is achieved at room temperature. Comparative studies further reveal an overlooked "micro-size effect", where micro-sized alloys establish more efficient electron/ion conduction pathways, significantly exceeding their nano-sized counterparts. This micro-size effect challenges the conventional belief that nano-sized alloys always outperform micro-sized ones. Based on this discovery, similarly high performance of other micro-alloys (lead and bismuth) in SSBs is further demonstrated. Given the additional benefits of easy synthesis, low cost, high tap density, and high stability, micro-sized alloys hold great promise as excellent anode candidates for SSBs.