Bi: A rising star for low-temperature fast-charging sodium-ion batteries

The rising demand for energy storage, such as electric vehicles in extreme conditions, polar and deep-sea exploration, necessitates batteries with exceptional low-temperature performance. Sodium-ion batteries (SIBs) exhibit wide temperature range adaptability and superior rate capability owing to smaller Stokes radius compared with Li+. Bi-based materials are characterized by low cost, moderate reaction potential and high volumetric capacity. In addition, the integration with ether-based electrolyte endows the Bi electrode with a continuous three-dimensional (3D) porous nanostructure, rendering it a promising candidate for fast-charging anode. Nevertheless, the low-temperature capabilities are constrained by a multitude of factors, including sluggish solid-state diffusion, diminished ionic conductivity, and slow Na+ desolvation kinetics. In this review, the challenges of huge volume expansion and opportunities of high diffusion coefficient intermediate phases for Bi-based materials are highlighted. A series of low-temperature high-performance Bi-based materials are also summarized, along with chemical design strategies tailored to enhance their performance. This review culminates in an overview of the prevailing challenges and prospects for the advancement of Bi-based materials as fastcharging anodes in low-temperature environments.