MOF-derived Multi-Shelled NiP2 Microspheres as High-Performance Anode Materials for Sodium-/Potassium-Ion Batteries

Development of high capacity, high-rate performance, long cycling life, and low-cost electrode materials is highly desirable for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) to pave the way for their rapid commercialization. Herein, NiP2 nanoparticles loaded in multi-shelled hollow N-doped carbon microspheres (NiP2@MHNC) are successfully prepared. The built-in heterogeneous interfaces between NiP2 and N-doped carbon promote Na+/K+ diffusion; the robust C-N, N-Ni bonds stabilize the structure of electrodes and accelerate the electrons transfer; and the multi-shelled hollow structure with large specific surface area effectively buffers the volume expansion to ensure cycling stability. Endowed with the aforementioned synergistic effect, the NiP2@MHNC exhibits remarkable enhancement in electrochemical performance with 346.6 mA h g(-1) after 300 cycles for SIB and 142 mA h g(-1) after 200 cycles for PIBs at 0.1 A g(-1). Moreover, the synergistic effect on electrochemical reaction kinetics is systematically analyzed. Further, the mechanism of sodium storage for NiP2@MHNC is also investigated. The research experience and conclusions in this study based on synergistic effect of heterogeneous interfaces, N-doped carbon, and multi-shelled hollow structure open up a meaningful route to design other similar advanced composite electrode materials in energy storage and conversion field.