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Nonmetallic ammonium (NH₄⁺) ions are applied as charge carriers for aqueous batteries, where hexagonal MoO₃ is initially investigated as an anode candidate for NH₄⁺ storage. From experimental and first‐principle calculated results, the battery chemistry proceeds with reversible building–breaking behaviors of hydrogen bonds between NH₄⁺ and tunneled MoO₃ electrode frameworks, where the ammoniation/deammoniation mechanism is dominated by nondiffusion‐controlled pseudocapacitive behavior. Outstanding electrochemical performance of MoO₃ for NH₄⁺ storage is delivered with 115 mAh g⁻¹ at 1 C and can retain 32 mAh g⁻¹ at 150 C. Furthermore, it remarkably exhibits ultralong and stable cyclic performance up to 100 000 cycle with 94% capacity retention and high power density of 4170 W kg⁻¹ at 150 C. When coupled with CuFe prussian blue analogous (PBA) cathode, the full ammonium …