Facile synthesis of a novel P-doped carbon coated nickel phosphides nanorods as sodium storage anode materials

Nickel-based phosphides as anode materials of sodium ion batteries have high capacity,but poor cycle stability and low electrical conductivity.Rational structural design for nickel-based phosphides with carbon provides a new way to address the above shortcomings.This paper presents a simple method to synthesize a novel carbon coated Ni_(x)P(x=2.4-3.0,denoted as Ni_(x)P@PC)nanorods using phosphoric acid resin as phosphorus and carbon sources.The Ni_(x)P nanocrystals are in-situ generated in the P-doped carbon without further phosphatization.The carbon layer can confine the volume changes during charging/discharging process.Additionally,the enriched P doping in the carbon layer greatly increases the electrical conductivity of the Ni_(x)P-based composite and provides more active sites for sodium storage.The as-obtained Ni_(x)P@PC nanorods reveal excellent reversible sodium storage performance(271.6 mA·h/g based on the mass of Ni_(x)P@PC at 0.1 A/g after 300 cycles)and outstanding cycling stability(0.005%capacity decay per cycle after 5000 cycles at 2 A/g).Meanwhile,the formation mechanism of Ni_(x)P@PC is evidenced by monitoring the evolution of morphology and structure during the preparing process.This paper may provide a feasible way for constructing high-performance transitional metal compounds for sodium-ion batteries.