Yolk-shelled FeP/Ni2P/C@C nanospheres with void: Controllable synthesis and excellent performance as the anode for lithium-ion batteries

Designing and preparing electrode materials with controllable morphology, structure and component to enhance electrochemical performance of lithium ion battery is still a challenging and valuable work. Herein, polyvinyl pyrrolidone (PVP) was selected as inducer, controller and carbon source for the successful synthesis of yolkshelled FeP/Ni2P/C@C nanospheres with voids. It revealed that the obtained FeP/Ni2P/C@C nanoparticles (NPs) possessed outer carbon layer with the thickness of average 10 nm and void between shell and internal nanoparticles with the width of about 8 nm. A model of recognition-nucleation-aggregation-limited growth-heterogeneous contraction was proposed for explaining the formation mechanism of yolk-shelled FeP/Ni2P/ C@C nanospheres. As anode material, the reversible capacity of FeP/Ni2P/C@C nanospheres reached 426 mA h g(-1) at a current density of 0.5 A g(-1) after 100 cycles. Even at the high current density of 1 A g(-1), it still retained a capacity of 364 mA h g(-1). Compared with FeP/Ni2P/C obtained without PVP, the FeP/Ni2P/C@C electrode with excellent electrochemical performance maybe owe to the distinctive yolk-shelled structure and synergistic effect of carbon, which could ease volume expansion, increase electrical conductivity and accelerate diffusion of Li+ ions and electrons in the process of charge/discharge. This work can be extended to develop other electrode materials with controlled structure and enhanced electrochemical performance for LIBs.