Co2P: A facile solid state synthesis and its applications in alkaline rechargeable batteries

The Co2P crystals are successfully synthesized by a facile solid state reaction. Energy dispersive X-ray spectrum (EDS) results indicate a mol ratio of 0.6686–0.3314 for Co to P, confirming the stoichiometric ratio of Co2P. Galvanostatic charge/discharge tests show that Co2P exhibits a high maximum discharge capacity (Cmax) of 223.5 mAh g−1 and excellent cyclic properties with capacity retention of 97.9% (C300/Cmax) in the 300th cycle as an anode material in alkaline rechargeable batteries. Cyclic voltammetry (CV) and XRD tests during full charge/discharge processes confirm a quasi-reversible redox mechanism between Co(OH)2 and Co resulting from the conversion of Co2P. The simultaneously produced P plays an important role in the whole process – with the reaction and dissolution in the electrolyte, it brings many new interspaces in Co2P body to enlarge the contact area between the active material and the electrolyte, and make the electrochemical process easier and faster.

► Co2P as anode material is used in alkaline secondary battery for the first time.
► Co2P exhibits a high capacity of 223.5 mAh g−1 and excellent cycle stability.
► The capacity retention is 97.9% (C300/Cmax) in the 300th cycle.
► The dissolving of P benefits the electrochemical performances.