Electrochemical Characteristics of Amorphous Ni-P Electroplated Thin Film

In this study, an amorphous nickel-phosphide (Ni-P) thin film was produced by electroplating, and its possible use as the anode material of a secondary lithium battery was explored. First, by changing the electroplating conditions, we created uniform and flat Ni-P thin films that contained 16–28 at% phosphorus. An evaluation of the manufactured thin film as anode material showed that a thin film with more phosphorus content had a higher specific discharge capacity. In particular, the initial gravimetric capacity of the electrode with the highest phosphorus content (28 at%) was comparable to that of graphite, but it had three times the initial volumetric capacity. The cycling stability improved with a higher phosphorus content. It was suggested that the adhesive strength between the substrate and thin film had a greater impact on the cycling stability than the physical damage caused by the volume changes during charging and discharging. To improve the specific capacity, we formed globular electrodeposits on the surface of the thin film. As a result, a discharge capacity comparable to the theoretical capacity of Ni-P was obtained, and the rate performance was additionally improved, without reduction in the life cycle.