Nitrogen-rich carbon with interconnected mesoporous structure has been simply prepared via a nano-CaCO3 template method, using polyaniline as carbon and nitrogen precursors. The preparation process includes in situ polymerization of aniline in a nano-CaCO3 aqueous solution, carbonization of the composites and removal of the template with diluted hydrochloric acid. Nitrogen sorption shows the carbon-enriched mesopores with a specific surface area of 113 m(2) g(-1). The X-ray photoelectron spectroscopy (XPS) analysis indicates that the carbon has a high nitrogen content of 7.78 at. %, in the forms of pyridinic and pyrrolic, as well as graphitic nitrogen. The nitrogen-rich mesoporous carbon shows a high reversible capacity of 338 mAh g(-1) at a current density of 30 mA g(-1), and good rate performance as well as ultralong cycling durability (110.7 mAh g(-1) at a current density of 500 mA g(-1) over 800 cycles). The excellent sodium storage performance of the nitrogen-rich mesoporous carbon is attributed to its disordered structure with large interlayer distance, interconnected porosity, and the enriched nitrogen heteroatoms.
Transition metal oxides can be considered as appealing candidates for sodium ion battery anode materials because these low-cost materials possess high capacity and enhanced safety. However, the practical application of these materials is usually limited by their low electronic conductivity and serious volume change during the charging-discharging process. Herein, we report the fabrication of 3D-0D graphene-FeO quantum dot hybrids by a facile one-pot hydrothermal approach as anode materials for sodium-ion batteries. FeO quantum dots with an average size of 4.9 nm are anchored on the surface of 3D structured graphene nanosheets homogeneously. Such unique hierarchical structure are advantageous for enlarging the electrode/electrolyte interface area and enhancing the electrochemical activity of the hybrid materials, inhibiting particle aggregation of FeO and accommodating their volume change during the charging-discharging process as well as enabling fast diffusion of electrons and rapid transfer of electrolyte ions. Consequently, the 3D-0D graphene-FeO quantum dot hybrids exhibit ultrahigh sodium storage capacity (525 mAh g at 30 mA g), outstanding cycling stability (312 mAh g after 200 cycles at 50 mA g) and superior rate performance (56 mAh g at 10 A g).
Nitrogen-doped carbon/graphene (NCG) hybrid materials were prepared by an in-situ polymerization and followed pyrolysis for sodium-ion batteries. The NCG has a large interlayer distance (0.360 nm) and a high nitrogen content of 7.54 at%, resulting in a high reversible sodium storage capacity of 336 mAh g -1 at 30 mA g -1 .The NCG shows a sandwich-like structure, i.e. nitrogen-doped carbon nanosheets closely coated on both sides of graphene. The carbon nanosheets shorten the ion
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