(257q) Crumpled P-Rich Metal Phosphide/Rgo Composite Powders for Advanced Li-Ion Batteries

Transition metal phosphides have been lately investigated as high capacity anode materials for lithium-ion batteries (LIBs) to replace commercial graphite electrodes that have low specific capacity. Depending on the amount of phosphorus, metal phosphides with various compositions can be synthesized. For example, nickel phosphides can exist in different stoichiometric ratios such as Ni₁₂P₅, Ni₄P₃, NiP, and NiP₂. Generally, it is known that transition metal phosphides are first transformed to metal nanograins (M) and amorphous-like Li₃P matrix, followed by an alloying reaction of the phosphorus nanograins with Li⁺ during cycling. Therefore, NiP₂ material with high P content is attractive for anode materials because it can offer high theoretical capacity and low potential versus Li/Li⁺. However, P-rich metal phosphide materials have been limited to a specific morphology so far, usually in the form of aggregated nanoparticles obtained from high energy mechanical milling. In order for P-rich metal phosphide materials to be applied as LIB anode materials, the development of a simple and cost-effective method to control the morphology of P-rich metal phosphides is crucial. In this study, we report a simple two-step method of systematically synthesizing reduced graphene oxide(rGO)/metal phosphide composite powders. The Ni/rGO composite powders prepared by scalable spray pyrolysis were then transformed into NiP₂/rGO composite powders by a simple phosphorization process in a vacuum-sealed ampoule. The synthesized NiP₂/rGO composite powders showed superior Li⁺ storage properties.