Carbon nanosheet@MoO2/Mo2C nanocrystalline-assembled hierarchical mesoporous nanospheres as high-performance anode for sodium-ion batteries

Highlights: • Hierarchical mesoporous nanospheres. • Ultrasmall MoO₂/Mo₂C nanocrystalline-embedded ultrathin carbon nanosheets. • High specific capacity, excellent cycling performance and rate capability. -- Abstract: It is crucial for sodium ion batteries to improve reversible capacity and lifespan of anode materials. Herein, a simple chelation and carbonization strategy is proposed to synthesize hierarchical mesoporous nanospheres of C@MoO₂/Mo₂C that are assembled by many ultrathin amorphous carbon nanosheets. These carbon nanosheets are further embedded by numerous ultrasmall MoO₂/Mo₂C nanocrystalline. The thickness of the carbon nanosheets is about 10 nm and the diameter of the nanocrystalline is 3–5 nm. C@MoO₂/Mo₂C exhibits plentiful mesopores and large surface area (179 m² g⁻¹), enhanced electrical/ionic conductivity and excellent structural stability. Benefiting from these positive structural advantages, C@MoO₂/Mo₂C exhibits high discharge capacity, good rate capability and outstanding cycling performance when used as anode for sodium-ion batteries. The discharge capacity is as high as 701 mAh g⁻¹ at current density of 0.5 A g⁻¹. Even at 5 A g⁻¹, average discharge capacity may stabilize at 253 mAh g⁻¹. After 300 cycles at 1 A g⁻¹, the discharge capacity of 441 mAh g⁻¹ is still achieved. This work offers a new synthesis and structure design strategy for developing high-performance anode materials of sodium ion batteries.