Heteroengineering‐Induced Electronic Reconstruction for Ammonium‐Ion Energy Storage

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.