CoNi hexacyanoferrate nanoparticles anchored on carbon nanotubes as superior cathode materials for rechargeable aqueous zinc-ion batteries

Prussian blue analogues (PBAs) have attracted growing interest as competitive cathode materials for aqueous zinc-ion batteries (AZIBs). However, their low conductivity and easy structural collapse often lead to poor reversible capacity and cyclability. Herein, cobalt‑nickel hexacyanoferrate (CoNiHCF), a CoNi-Prussian blue analogue, are designed as AZIBs cathode materials for the first time, in which highly uniform CoNiHCF nanocubes are in-situ decorated on carbon nanotubes (CNTs) via a simple co-precipitation method. The resulted CoNiHCF/CNTs composite displays superior zinc ion storage performance, with a great reversible capacity of 124.9 mAh g−1 at the current density of 50 mA g−1, and a high capacity retention of 81.8 % at 3000 mA g−1 for 1000 cycles, which are remarkably superior to those of CoHCF, NiHCF and CoNiHCF. The excellent Zn2+ storage properties of CoNiHCF/CNTs can be ascribed to the bimetallic synergistic effect of Co and Ni as well as the introduction of conductive CNTs skeleton. This study offers a straightforward and efficient method for promoting the application of PBAs-based cathodes in AZIBs.