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Biomass‐derived carbon materials are an amazing electrode material for supercapacitor, owing to their abundant, porous structure and composition. Herein, a controllable N content carbon material with hierarchical porous structure was fabricated via an integrated carbonization, activation and nitrogen‐doping process. N‐rich camellia pollen is used as carbon precursor, while NH4Cl is employed as both activation agent and dopant. The optimal N‐doped carbon with higher N content (3.82 at%), suitable pore size distribution and larger specific surface area (810 m2 g−1), provides abundant ion transport channels and exposes more accessible active sites. Thus, a high specific capacitance of 280 F g−1 (1 A g−1) in 6 M KOH (three‐electrode system) can be obtained with making full use of N−HPC‐1. Moreover, the assembled symmetrical supercapacitor delivers high energy densities both in 6 M KOH (13.3 Wh kg−1) and 1 M Na2SO4 (20 Wh kg−1) that can be used for LED lighting. More than that, it is also demonstrates excellent cycle stability in 6 M KOH (85.4% after 20000 cycles at 20 A g−1). In view of the above‐mentioned merits, this N‐doped hierarchical porous carbon is anticipated to be a promising material for application in supercapacitors and other fields. [ABSTRACT FROM AUTHOR]

In this work, we developed a simple one-step hydrothermal method to successfully prepare Fe3O4/FeS-reduced graphene oxide (Fe3O4/FeS/rGO) composite directly, which is a novel Lithium-ion batteries (LIBs) anode material. The characterization of Fe3O4/FeS/rGO composite demonstrates that octahedral Fe3O4/FeS particles are uniformly deposited on the rGO, leading to a strong synergy between them. The excellent structural design can make Fe3O4/FeS/rGO composite to have higher reversible capacity (744.7 mAh/g at 0.1 C after 50 cycles), excellent cycling performance and superior rate capability. This outstanding electrochemical behavior can be attributed to the conductivity network of rGO, which improves the composite electrode conductivity, facilitates the diffusion and transfer of ions and prevents the aggregation and pulverization of Fe3O4/FeS particles during the charging and discharging processes. Moreover, the Fe3O4/FeS/rGO electrode surface is covered with a thin solid-electrolyte interface (SEI) film and the octahedral structure of Fe3O4/FeS particles is still clearly visible, which indicates that composite electrode has excellent interface stability. We believe that the design of this composite structure will provide a new perspective for the further study of other transition metal oxides for LIBs. The Fe3O4/FeS-reduced graphene oxide (Fe3O4/FeS/rGO) composite was obtained using one-step hydrothermal method. Thereinto, octahedral Fe3O4/FeS particles are uniformly deposited on the rGO, leading to a strong synergy between them. With the advantages of excellent structure, the Fe3O4/FeS/rGO composite holds the prospective applications as an advanced anode material in LIBs. [ABSTRACT FROM AUTHOR]

Multi-element doped porous carbon materials are considered as one of the most promising electrode materials for supercapacitors due to their large specific surface area, abundant mesoporous structure, heteroatom doping and good conductivity. Herein, we propose a very simple and effective strategy to prepare nitrogen, sulfur co-doped hierarchical porous carbons (N-S-HPC) by one-step pyrolysis strategy. The effect of sole dopants as a precursor was a major factor in the transformation process. The optimized N-S-HPC-2 possesses a typical hierarchically porous framework (micropores, mesopores and macropores) with a large specific surface area (1284.87 m2 g − 1) and N (4.63 atomic %), S (0.53 atomic %) doping. As a result, the N-S-HPC-2 exhibits excellent charge storage capacity with a high gravimetric capacitance of 360 F g − 1 (1  A g − 1) in three-electrode systems and 178 F g − 1 in two-electrode system and long-term cycling life with 87% retention after 10,000 cycles in KOH electrolyte. Nitrogen, sulfur co-doped hierarchical porous carbons (N-S-HPC) materials are prepared by a very simple and effective pyrolysis strategy. The effect of sole dopants as a precursor was a major factor in the transformation process. This work demonstrates that K2CO3 and thiourea synergistic effect can greatly enhance electrochemical properties of the heteroatoms co-doped biomass based hierarchically porous carbon. [ABSTRACT FROM AUTHOR]

Fe 7 S 8 has a high theoretical capacity (663 mAh g -1 ) and can be prepared at a low cost, making it advantageous for production. However, Fe 7 S 8 has two disadvantages as a lithium-ion battery anode material. The first is that the conductivity of Fe 7 S 8 is not good. The second is that when the lithium ion is embedded, the volume expansion of the Fe 7 S 8 electrode is serious. That is why Fe 7 S 8 has not been used in real life yet. In this paper, Co-Fe 7 S 8 /C composites were prepared by doping Co into Fe 7 S 8 through a one-pot simple hydrothermal method. In situ Co is doped into Fe 7 S 8 to produce a more disordered microstructure to improve ion and electron transport performance, thereby reducing the activation barrier of the main material. The Co-Fe 7 S 8 /C electrode presents a high specific discharge capacity of 1586 mAh g -1 and a Coulombic efficiency (CE) of 71.34% at an initial cycle at 0.1 A g -1 . After 1500 cycles, the specific discharge capacity remains at 436 mAh g -1 (5 A g -1 ). When the current density returns to 0.1 A g -1 , the capacity almost returns to the initial level, showing excellent rate performance.