Hierarchical porous nitrogen-rich carbon nanospheres with high and durable capabilities for lithium and sodium storage

To improve the energy storage performance of carbon-based materials, considerable attention has been paid to the design and fabrication of novel carbon architectures with structural and chemical modifications. Herein, we report that hierarchical porous nitrogen-rich carbon (HPNC) nanospheres originating from acidic etching of metal carbide/carbon hybrid nanoarchitectures can be employed as high-performance anode materials for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The structural advantages of HPNC nanospheres are that the exceptionally-high content of nitrogen (17.4 wt%) can provide abundant electroactive sites and enlarge the interlayer distance (∼3.5 Å) to improve the capacity, and the large amount of micropores and mesopores can serve as reservoirs for storing lithium/sodium ions. In LIBs, HPNC based anodes deliver a high reversible capacity of 1187 mA h g^-1 after 100 cycles at 100 mA g^-1, a great rate performance of 470 mA h g^-1 at 5000 mA g^-1, and outstanding cycling stabilities with a capacity of 788 mA h g^-1 after 500 cycles at 1000 mA g^-1. In SIBs, HPNC based anodes exhibit a remarkable reversible capacity of 357 mA h g^-1 at 100 mA g^-1 and high long-term stability with a capacity of 136 mA h g^-1 after 500 cycles at 1000 mA g^-1.