Facile synthesis of Co₂P via the reduction of phosphate with KBH₄ for nickel-based rechargeable batteries

Highlights: • We report a new way to prepare Co₂P for nickel-based rechargeable batteries. • The reversible discharge capacity of Co₂P is about 244 mAh g⁻¹. • Co₂P exhibits attractive cycle stability and rate capability. - Abstract: Crystalline Co₂P is synthesized via a green and effective method based on the reduction of phosphate with KBH₄. Various analytical techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy-dispersive spectroscopy instrument are employed to characterize the obtained Co₂P. Moreover, it is electrochemically used as an anode material for nickel-based rechargeable batteries and compared with amorphous Co–P prepared by chemical reduction. Co₂P electrode presents superior electrochemical properties such as discharge capacities, cycle stability, and rate capability to Co–P electrode. The reversible discharge capacity of Co₂P electrode is about 244.1 mAh g⁻¹ at 100 mA g⁻¹ which can be retained after 200 cycles. Co₂P electrode also shows promising high rate performance. Furthermore, cyclic voltammogram illustrates that the reversible electrochemical capacity of Co₂P electrode is attributed to the redox of Co/Co(OH)₂. Electrochemical impedance spectroscopy displays that the charge transfer resistance of Co₂P electrode is smaller than that of Co–P electrode