Aqueous alkali-ion batteries are gaining traction as a low-cost, sustainable alternative to conventional organic lithium-ion batteries. However, the rapid degradation of commonly used electrode materials, such as Prussian Blue Analogs and carbonyl-based organic compounds, continues to challenge the economic viability of these devices. While stability issues can be addressed by employing highly concentrated water-in-salt electrolytes, this approach often requires expensive and, in many cases, fluorinated salts. Here, we show that replacing monovalent K