Heteroengineering‐Induced Electronic Reconstruction for Ammonium‐Ion Energy Storage

ABSTRACT

Ammonium‐ion supercapacitor (AISC) emerges as a promising energy storage system owing to its safety, low cost, and sustainability. However, the large tetrahedral geometry of NH ₄ ⁺ , compared with the spherical structure of metallic charge carriers, leads to an inefficient intercalation chemistry, resulting in unsatisfied capacity. Here, we introduce local heteroengineering on the VO ₂ (B) surface to modulate its electronic structure, which enables an integrated electronic reconstruction behavior: (i) electrons spontaneously transfer to the higher‐energy V t _2g orbital, enhancing the intrinsic conductivity; (ii) adaptive electron redistribution at the heterointerface generates a reversible built‐in electric field (BIEF), offering extra coulombic driving force for NH ₄ ⁺ (de)intercalation. This electronic adjustment accordingly reduces the NH ₄ ⁺ diffusion energy barriers in host materials and promotes NH ₄ ⁺ intercalation efficiency. As a result, the VO ₂ @VS heterogenous electrode delivers 214.7 mAh g ⁻¹ (556.3 F g ⁻¹ ) at 1 A g ⁻¹ , reaching 2/3 theoretical capacity of vanadium dioxides (323 mAh g ⁻¹ ), and retains 107.2 mAh g ⁻¹ (275 F g ⁻¹ ) at a high current density of 10 A g ⁻¹ . This study explores the electronic structural evolution induced by rational heteroengineering, providing new pathways for advancing efficient ammonium‐ion energy storage systems.