Synergetic modulation on multiple transition metals enables NiCoxZnyP(1+x+y)/2 microspheres for efficient lithium-ion storage†

For transition metal phosphides, poor cycling stability and conductivity are the main issues limiting their practical applications. There have been many solutions to these problems, but there are still relatively few methods based on the synergistic effect of multiple transition metals for transition metal phosphides. Herein, this study presents a rational design of three-dimensional (3D) NiCo_xZn_yP_(1+x+y)/2 (x = 1 or 1/2, 0 < y ≤ 1/2) microspheres via a facile two-step route. Experimental characterization and theoretical calculation indicate that the synergistic effect of transition metal elements enables the optimization of the micro-structures, induces electron transfer between metal ions, increases active sites, improves lithium ion diffusion kinetics, and provides fast mass/charge transfer channels of NiCo_xZn_yP_(1+x+y)/2. Significantly, NiCo_1/2Zn_1/6P_5/6 displays the best electrochemical performance as an anode material in lithium-ion batteries. It exhibits a high reversible specific capacity (624 mA h g⁻¹, 400 cycles at 0.2 A g⁻¹), great rate performance and excellent cycling stability even with a capacity retention of 116.57% after 10 000 cycles at 5.0 A g⁻¹. This study indicates that rational design of transition metal phosphide anode materials based on the synergistic effect of multiple transition metals is a feasible strategy for achieving high-performance energy storage applications.