Designing sodium alloys for dendrite‐free sodium‐metal batteries

Abstract Sodium metal, with a high theoretical specific capacity (∼1165 mA h g−1) and a low redox potential (−2.71 V vs. SHE) as well as low cost, becomes an attractive option for high‐energy‐density sodium secondary batteries. However, the practical application of sodium metal anodes is hindered by dendrite growth, which results in low energy efficiency, poor lifetime and serious safety issues. To address this challenge, researchers propose various strategies, including the formation of sodium alloys (Na‐M alloys, M = Sn, Sb, Bi, In, etc.) through alloying reaction. The alloying effect has a positive impact in terms of reducing the local current density, mitigating the volume expansion, and inhibiting the dendrite growth. It is thus an effective solution for constructing high‐performance sodium secondary batteries. This review systematically describes the mechanism of dendrite growth and the alloying process of Na‐M alloys, summarizes recent research progress and strategies for applying Na‐M alloys to create dendrite‐free sodium secondary batteries, as well as presents prospects for the development of Na‐M alloys and offers clear suggestions for future research. This review aims to inspire further efforts to build dendrite‐free, high‐performance sodium secondary batteries and broaden a new aspect for the next‐generation battery systems.