Alkaline-based aqueous sodium-ion batteries for large-scale energy storage

Aqueous sodium-ion batteries (ASIBs) are practically promising for large-scale energy storage, but their energy density and lifespan are hindered by water decomposition. Current strategies to enhance the water stability include using expensive fluorine-containing salts to create a solid electrolyte interface or adding potentially-flammable organic co-solvents in the electrolyte to reduce water activity. However, these methods have significantly increased cost and safety risk. Shifting electrolytes from near neutrality to alkalinity can fundamentally suppress hydrogen evolution, but trigger oxygen evolution and cathode dissolution. Here, we present an alkaline-type ASIB with Mn-based Prussian blue analogue cathode, which exhibits a record lifespan of 13,000 cycles at 10 C together with high energy density of 90 Wh kg−1 at 0.5 C. This is achieved by building a nickel/carbon layer to induce a H3O+-rich local environment near the cathode surface, thereby suppressing oxygen evolution and cathode dissolution. Simultaneously, Ni atoms can be in-situ embedded into the cathode to enable its durability. At an industry-level mass loading > 30 mg cm−1, the pouch cell exhibits excellent stability with a capacity retention of ~ 100% following 200 cycles at 300 mA g−1, outperforming previously reported aqueous batteries.