Developing next-generation hard carbon anodes for fast-charging sodium-ion batteries

Hard carbon (HC) anodes are one of the most promising electrodes for sodium-ion batteries (SIBs) because of their low cost, high reversible specific capacity, and suitable operating voltage. However, the poor fast-charging properties of HC limits the broad applicability of SIBs in practical scenarios. This review initially meticulously dissects the underlying sodium storage mechanisms and kinetic behaviors of the HC anode, elucidating the direct correlation with the rate capabilities. Afterward, recent advancements in the field are systematically surveyed, encompassing strategies such as structural modification, interface engineering, morphology regulation, and electrolyte optimization. These methodologies are pivotal in addressing the challenges and unlocking the full potential of HC anodes for high-rate SIB applications. Eventually, by synthesizing the current state-of-the-art and delineating prospective research directions. This review aims to promote the development of HC, thereby advancing next-generation SIBs with superior energy density, cycle life, high-rate capability, and safety, ultimately facilitating the broader adoption of sodium-based energy storage systems.