Substrate Designs for Stable Potassium Metal Anodes

Potassium metal batteries (PMBs) are gaining attention as low-cost, sustainable, and high-energy storage. Their practical implementation, however, is impeded by instability of the potassium (K) metal anode, manifested as dendritic growth, large volume fluctuations, and fragile solid electrolyte interphases (SEIs), all of which accelerate capacity fading and safety risks. This review highlights recent advances in substrate design for stabilizing K metal anodes, categorized into five strategies: (i) three-dimensional host architectures, (ii) heteroatom doping and molecular grafting, (iii) inorganic nanoparticle incorporation, (iv) alloying seed engineering, and (v) substrate-regulated SEI formation via work function modulation. Mechanistic insights from experimental and theoretical studies are integrated with performance comparisons to evaluate trade-offs between deposition control, SEI stability, scalability, and cost. Key challenges for commercialization are outlined, including long-term cycling under practical conditions, integration with high-energy-density cathodes, and scalable fabrication. By advancing structural, chemical, and electronic design principles, PMBs can progress toward reliable, high-performance energy storage.