Atomic‐Level Interactions Enable “Near‐Zero Strain” Cathodes for Ultra‐Stable Aqueous Magnesium‐Ion Batteries

Aqueous magnesium-ion batteries (AMIBs) are promising next-generation energy storage devices owing to their high safety, theoretical capacity, and resource abundance. However, the strong electrostatic interactions between Mg-ions and conventional cathodes usually lead to poor cycling stability and limited rate capability. Herein, we, for the first time, introduced "Near-Zero Strain" engineering in AMIBs to developed the proof-of-the-concept high entropy Prussian blue analog (HEPBA) cathodes materials with ultra-stable cycling performance. The atomic-level interactions and long-range disordered lattice strain field enable HEPBA to spontaneously respond to ion intercalation-induced stress with reversible changes in lattice structure, achieving one of the best long-term stability among AMIBs (above 96.7% capacity retention after 20 000 cycles at a high current density of 5.0 A g^- ¹). Meanwhile, diverse metal atoms with overlapped d-band toward optimized HEPBA features efficient charge compensation with drastically enhanced rate capability (over 80.1 mAh g^-1 at 5.0 A g^- ¹). Overall, the novel near-zero strain engineering strategy toward cathode materials in this work revealed the enormous potentiality to improve multivalent-ion batteries performance.