Bi/C nanosheet microspheres with an open pore structure as anodes for sodium ion batteries with high capacity, excellent rate performance and long cycle life

To develop high-performance and low-cost anode materials for sodium ion batteries, novel Bi/C nanosheet microspheres with an open pore structure (labeled as ops-Bi/C nanosheet microspheres), in which nanosheets are assembled from Bi nanospheres and disordered C, are synthesized through facile methods using Bi(NO3)(3), glucose and ethylene glycol as raw materials. Benefiting from the synergy of the material's unique microstructure, carbon coating and NaPF6-diglyme electrolyte, the ops-Bi/C nanosheet microspheres exhibit a higher stable reversible capacity (similar to 400 mA h g(-1) at 0.1 A g(-1)) than the theoretical capacity of Bi metal, excellent rate performance (396, 393, 395, 392 and 381 mA h g(-1) at 0.2, 1, 5, 10 and 20 A g(-1), respectively) and long cycle life (361 mA h g(-1) after 10 000 cycles at 5 A g(-1)). Moreover, even if the mass loading of the ops-Bi/C nanosheet microspheres exceeds 10 mg cm(-2), the electrode still shows a high reversible capacity of 321 mA h g(-1) at 0.8 A g(-1) with good cycle performance. The sodium ion full cells composed of the ops-Bi/C nanosheet microsphere anode and commercial Na3V2(PO4)(3) (NVP) cathode exhibit high energy density (174 W h kg((total))(-1) at 0.1 A g((NVP))(-1)) and long cycle performance (600 cycles at 1 A g((NVP))(-1)).

Automated summary

Novel Bi/C nanosheet microspheres with an open pore structure were synthesized and exhibited excellent performance in sodium ion batteries due to the synergy of their unique microstructure, carbon coating, and NaPF6-diglyme electrolyte. These microspheres showed high reversible capacity, outstanding rate capability, and long cycle life, making them promising materials for advanced energy storage applications.