Nickel–iron batteries: Overcoming traditional barriers and ushering in a new era of energy storage

Amidst the global shift toward clean energy systems, nickel–iron (Ni–Fe) batteries have re-emerged as compelling candidates for long-duration and grid-scale energy storage, owing to their superb cycling stability and inherent safety. However, critical challenges related to Fe anodes and Ni(OH) 2 cathodes hinder the widespread practical deployment of Ni–Fe batteries. While prior studies have clarified fundamental mechanisms, a comprehensive framework addressing the key performance bottlenecks remains lacking. This review provides an overview of the historical development of Ni–Fe batteries, establishes comprehensive design principles to guide the development of practical Ni–Fe batteries, and systematically analyzes the key challenges and corresponding solutions, with a particular emphasis on electrode engineering of Fe anodes and Ni(OH) 2 cathodes. Through well-defined guidelines and industrial perspectives, this work supports the rational development of Ni–Fe batteries and facilitates their practical application in long-duration and large-scale energy storage systems.