Light-Induced NH ₄ ⁺ Deprotonation Drives NH ₄ ⁺ /H ⁺ Hybrid Storage Toward Near-Theoretical Capacity in NH ₄ V ₄ O ₁₀ Electrodes

Ammonium-ion batteries (AIBs) utilize the earth abundance, low molar mass, and small hydrated radius of NH 4 + to achieve high gravimetric specific capacity, offering a sustainable alternative to metal-ion systems for large-scale energy storage. However, achieving high capacity in AIB electrodes remains challenging due to inefficient NH 4 + intercalation. Here, we demonstrate that photodriven NH 4 + deprotonation on the NH 4 V 4 O 10 electrodes enables near-theoretical capacity through hybrid NH 4 + /H + storage. Light irradiation modulates the ions intercalation kinetics, enhancing the ion diffusion contribution while maintaining pseudocapacitive behavior, boosting capacity by 76.6%. The capacity of the NH 4 V 4 O 10 electrode reaches 539 mAh g –1 at 1 A g –1, approaching its theoretical capacity (589 mAh g –1 ). TOF-SIMS and in situ Raman spectroscopy revealed that light triggers NH 4 + deprotonation at the electrode/electrolyte interface, enabling proton intercalation as the primary capacity enhancement mechanism. DFT calculations rationalize this effect by showing that photoexcitation of NH 4 V 4 O 10 reduces the NH 4 + deprotonation barrier on surface, and facilitates proton intercalation. Such interfacial photocontrol of NH 4 + dynamics explores new pathways toward efficient ammonium-ion batteries with photo assistance.