Aqueous Na-ion and K-ion Batteries

The urgent need for sustainable and safe energy storage solutions has spotlighted rechargeable aqueous Na- and K-ion batteries as promising alternatives to conventional nonaqueous Li-ion systems. Na and K are abundant, globally distributed, and cost-effective, while aqueous electrolytes offer inherent safety and environmental advantages. However, key challenges persist, particularly in expanding the narrow operating potential window of aqueous electrolytes and in developing active materials that can accommodate the large ionic sizes of Na+ and K+. This chapter reviews recent advances in overcoming these limitations and outlines innovations that are further required to realize safe, scalable, and sustainable aqueous Na- and K-ion batteries.