Influence of separator and bimetallic doping on Zn2+ ion storage properties of Prussian blue analogues for aqueous zinc-ion batteries

Prussian blue analogues (PBA) have been gaining attention as cathode materials for Aqueous zinc-ion batteries (AZIBs) owing to their 3D open framework structure; however, they suffer from low specific capacity, fast degradation, and poor cycling stability. In this study, we report Co–Ni co-doped PBA, with different Co and Ni ratios with high purity and crystallinity as cathode materials for AZIBs. Moreover, different low-cost porous water-based separators are proposed in conjunction with Co–Ni co-doped PBA cathodes. The studies on Zn||Zn symmetric cell show that nitrocellulose membrane (NC) separator can operate over 2000 h with lower hysteresis voltage of 90 mV and considerably decreases the dendrite grown on the Zn-metal surface due to the uniform pore size distribution. Benefiting from the synergetic effect of bimetallic doping and Zn dendrite inhibition ability from NC separator, the aqueous K1.9Co0.67Ni0.33[Fe(CN)6].1.7H2O||Zn cell is able to display excellent cycling performance of 5000 cycles at 1 A g−1 with a maximum capacity retention of 84 %. This research not only demonstrates the considerable effect of bimetallic doping on the Zn storage performance of PBA cathodes, but it also discloses the influence of separator on the zinc striping/plating process, which will provide insights into the development of high-performance AZIBs.