Enhanced Silicon Diphosphide-Carbon Composite Anode for Long-Cycle, High-Efficient Sodium Ion Batteries

Advanced anode materials possessing high performance, excellent stability, and low cost are quite insufficient for sodium ion batteries (NIBs), and there is a call for huge progress to meet the prerequisites toward practical applications. Herein, a silicon diphosphide (SiP2)/carbon composite anode was synthesized by a facile ball milling method to improve the NIBs performance. The well-constructed composite comprised of uniformly distributed SiP2 nanocrystallites within a conductive carbon framework greatly enhanced the electrode conductivity and structural compatibility to repeated sodiation/desodiation conversions and thus generated an excellent cyclability of >80% capacity retention for 500 cycles, a high Coulombic efficiency of 99%, and a promising fast-rate capability. In-situ/ex-situ X-ray diffraction and in-situ transmission electron microscopy investigations on the reversible electrochemical conversion of SiP2 showed the formation of Na3P and NaSi6 as the main sodiation products. This study sheds light on the realization of large-scale, high-performance NIBs through superior phosphorus-based anode materials.