SnO2@carbon nanostructure composites are prepared by a simple hydrothermal method. The composite exhibits unique structure, which consists of a mesoporous SnO2 core assembled of very small nanoparticles and a carbon shell with 10 nm thickness. The mesoporous SnO2@carbon core-shell nanostructures manifest superior electrochemical performance as an anode material for lithium ion batteries. The reversible specific capacity of the composite is about 908 mAh g(-1) for the first cycle and it can retain about 680 mAh g(-1) after 40 charge/discharge cycles at a current density of 0.3 C. Moreover, it shows excellent rate capability even at the high rate of 4.5 C. The enhanced performance was attributed to the mesoporous structure and a suitable carbon coating.

No abstract

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.

No abstract

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[Formula: see text]mAh/g at 0.1[Formula: see text]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.