Epitaxial Core–Shell MnFe Prussian Blue Cathode for Highly Stable Aqueous Zinc Batteries

The high-safety aqueous zinc battery is regarded as a desirable alternative to lithium-ion batteries; however, it still lacks sufficient cycling capability. The primary impediment is structural distortion of cathode materials in aqueous electrolytes. Here we propose an epitaxial Fe- on Mn-hexacyanoferrate to construct a core–shell double-atom-redox Prussian blue analogue (PBA). The shell Fe-PBA shows a small volumetric change, inclined toward surface amorphization upon ion-insertion, leading to the low-strain core–double shell structure. The in situ surface reorganization effectively suppresses Jahn–Teller distortion and prevents Mn dissolution into electrolyte in the core Mn-PBA. Consequently, the cathode design that facilitates high-voltage full cells (over 1.8 V vs Zn2+/Zn) enables a high discharge capacity of 166 and 117 mAh g–1 and a capacity retention of 72.4% and 83.9% over 400 and 4800 cycles at 0.1 and 2 A g–1, respectively. A pouch cell operates successfully under harsh conditions from −30 to 60 °C.