Potassium-ion batteries for stationary energy storage solutions

Potassium-ion batteries (KIBs) are emerging as a potentially sustainable and cost-competitive technology for stationary energy storage. Built on earth-abundant elements, exhibiting favourable redox potentials, and broadly compatible with existing lithium-ion manufacturing infrastructure, KIBs present a credible route to large-scale, low-cost deployment. In this review, we provide a critical and integrative assessment of KIB science and technology, connecting fundamental materials chemistry and interfacial behaviour to the engineering and techno-economic demands of grid-scale and residential storage. We begin with the fundamental electrochemistry of the KIB system, examining K⁺ solvation and transport in liquid electrolytes, ion diffusion through crystalline and amorphous electrode hosts, and the charge-transfer kinetics and passivation processes that govern electrode-electrolyte interfaces. Building on these foundations, we evaluate the most promising classes of cathode, anode, and electrolyte materials, identify the principal challenges associated with full cell integration, and define the application-relevant performance descriptors, energy and power density, cycle and calendar life, temperature window, and cost that underpin stationary deployment. The contemporary industrial landscape is then surveyed, encompassing the first commercial prototypes, pilot-scale manufacturing lines, and nascent supply chains. Safety, abuse tolerance, and long-term reliability are assessed under operating conditions representative of real-world grid duty cycles, and KIBs are quantitatively benchmarked against incumbent lithium-ion and emerging sodium-ion technologies. Finally, we articulate a forward-looking research and development roadmap that encompasses materials discovery, interfacial engineering, scalable cell design, sustainability, safety, and recycling to guide the translation of KIBs from laboratory innovation to commercially viable stationary storage systems.