One-step hydrothermal synthesis of CoNi bimetallic phosphide nanoflowers for high-performance quasi-solid-state zinc-ion batteries

Nickel-cobalt bimetallic phosphide (CNP) samples with a flower-like nanosheet morphology are prepared on nickel foam by a simple one-step hydrothermal method to form the cathodes in zinc-nickel batteries. The electrode materials possess not only synergistic properties rendered by nickel and cobalt, but also high theoretical specific capacity and electronic conductivity of transition metal phosphide. The quasi-solid-state batteries assembled with the phosphide electrode, zinc sheet, and hydrogel electrolyte are assessed in alkaline media. The flexible Zn-CNP battery shows an areal capacity of 3.75 mA h cm⁻² at a high current density of 50 mA cm⁻² and retains 93% of its capacity after 2000 cycles (at 80 mA cm⁻²). Furthermore, the quasi-solid-state battery continues to function despite being bent at different angles or after puncturing. The results reveal a novel strategy to design bimetallic phosphide electrodes in zinc-ion batteries for flexible and wearable applications.