Enabling a High‐Entropy Effect Paradigm for Efficient Zn ²⁺ /NH ₄ ⁺ Energy Storage

Abstract Aqueous energy storage devices (AESD) have the advantages of intrinsic safety, environmental friendliness, and low cost. Among them, the high energy density characteristic of zinc ion batteries (ZIBs) and the fast charge capability of ammonium ion capacitors (AICs) are particularly prominent. The common demand lies in that Zn 2+ needs a stable framework to resist distortion and NH 4 + needs surface active sites to promote rapid transport. Here, a high‐entropy oxide (FeCoNiCrMn) 3 O 4 (HEO) is developed. HEO has an irregular polyhedral spinel structure with a unique high‐entropy effect, which is thermodynamically stabilized to build a rigid framework, regulate the d‐band centers, optimize the electron distribution, induce surface defect‐rich structures, synergically accelerates the reaction kinetics for effective storage of Zn 2+ /NH 4 + . Therefore, excellent electrochemical performance of both Zn 2+ (320.2 mAh g −1 at 0.10 A g −1 and 100.6 mAh g −1 at 10.00 A g −1 with 82.2% capacity retention at 5.00 A g −1 after 3600 cycles) and NH 4 + (391.1 F g −1 at 0.50 A g −1 with 96.1% capacity retention at 5.00 A g −1 after 15 000 cycles) is obtained in HEO. Furthermore, the Zn 2+ storage mechanism involves high‐entropy multi‐ion synergistic charge transfer and interfacial chemical adaptation. This work provides an innovative paradigm for the universal design of AESD.