Hierarchical Nitrogen-Doped Porous Carbon Microspheres as Anode for High Performance Sodium Ion Batteries

Sodium ion batteries (SIBs) have been considered as a promising alternative to lithium ion batteries (LIBs) for large scale energy storage in the future. However, the commercial graphite anode is not suitable for SIBs because of its low Na⁺ ions storage capability and poor cycling stability. Recently, another alternative as anode for SIBs, amorphous carbon materials, have attracted tremendous attention because of their abundant resource, nontoxicity, and most importantly, stability. Here, N-doped hierarchical porous carbon microspheres (NHPCS) derived from Ni-MOF have been prepared and used as anode for SIBs. Benefiting from the open porous structure and expanded interlayer distance, the diffusion of Na⁺ is greatly facilitated and the Na⁺ storage capacity is significantly enhanced concurrently. The NHPCS exhibit high reversible capacity (291 mA h g^-1 at current of 200 mA g^-1), excellent rate performance (256 mA h g^-1 at high current of 1,000 mA g^-1), and outstanding cycling stability (204 mA h g^-1 after 200 cycles).