Search

Activated graphene nanosheets (AGNs) are fabricated from graphene nanosheets (GNSs) by the facile KOH activation process. It displays that the obtained AGNs have a hierarchical porous structure, leading to the superhigh specific surface area of 2662 m2 g−1. The obtained AGNs electrode exhibited high specific capacitance (238 F g−1 at 1 A g−1) and remarkable rate performance (79.41% at 10 A g−1), exhibiting higher rate performance than reported carbon materials. Furthermore, the AGNs also show exceptional cycling capacity (99% after 20,000 cycles at 5 A g−1) in 1.0 M TEA BF4/AN electrolyte with an ultra-high potential range from 0 to 3.5 V. The symmetric supercapacitor displays a high energy density of 42.78 Wh kg−1 at a power density of 2071 W kg−1 and excellent cycle stability. The superior electrochemical performance can be attributed to the high specific surface area that has a larger contact area with the electrolyte, and the porous structure which provides a richer ion transport channel. Image 1 ● The AGNs with the hierarchical porous structure were fabricated via the KOH activation of GNSs. ● The AGNs show a high specific capacitance of 238 F g−1 at 1 A g−1 at an ultra-high potential range from 0 to 3.5 V in 1.0 M TEA BF4/AN electrolyte. ● The symmetric supercapacitor displays a high energy density of 42.78 Wh kg−1 at a power density of 2071 W kg−1 and excellent cycle stability. [ABSTRACT FROM AUTHOR]

Nowadays, Lithium-ion batteries (LIBs) are prevalently applied in numerous areas, leading to increasing demand of innovative electrodes with high specific capacities. An advanced CuGeO 3 /reduced graphene oxide (rGO) structure is designed and fabricated as the anode material taking the advantage of considerable capacity offered by CuGeO 3 and stable framework constructed by rGO. The as-prepared CuGeO 3 with 30 wt% GO addition exhibits the best electrochemical performance. Specifically, a reversible charge capacity of 909 mAh·g−1 with high coulombic efficiency of 91.49% at the current density of 100 mA g−1 after 200 cycles is demonstrated, and the rate capacity retains 747.6 mAh·g−1 with 91.59% capacity retention. These results indicate that the CuGeO 3 /rGO composite holds great potential in next-generation LIBs. [ABSTRACT FROM AUTHOR]

A hollow tremella-like graphene sphere/tin dioxide (HTGS/SnO 2) composite was successfully prepared by simple emulsification and impregnation followed by calcination. In this material, tin dioxide adheres to the folds on the surface of the hollow tremella-like graphene spheres. Hollow tremella-like graphene spheres as the matrix of SnO 2 not only provide a space of volumetric expansion for the tin oxide particles, relieve the internal stress of the tin dioxide, but also effectively avoid aggregation of the tin dioxide and increase the electrical conductivity. As an anode electrode material for batteries, the initial discharge/charge capacities of HTGS/SnO 2 are 1762.4 mAh g-1 and 1169.4 mAh g-1, and the Coulomb efficiency is 96.9%. After 50 cycles, capacity remains 80.4% of reversible capacity. The excellent electrochemical stability is attributed to the extraordinary structure of HTGS/SnO 2. The hollow structure of graphene sphere allows simultaneous insertion of lithium ions from the inner and outer surfaces. Meanwhile, the tin dioxide particles are uniformly dispersed by the wrinkles on the surface of the graphene, thereby enlarging the space for the volume expansion of tin dioxide in order to avoid contact with the electrolyte. [ABSTRACT FROM AUTHOR]

With the large-scale practical application of electric vehicles and mobile devices, more and more attention has been focused on the research of high specific capacity lithium-ion batteries (LiBs) anode materials. Novel graphene caging core-shell Si@Cu nanoparticles anchored on graphene sheets (Si@Cu@rGO) anode was prepared by deposition-precipitation and one-step thermal reduction methods. During the preparation, CuC 2 O 4 and graphene oxide are simultaneously reduced and coated on silicon nanoparticles. Introduced copper can enhance charge transfer kinetics of the electrode and suppress the tight cluster of Si nanoparticles. Besides, the graphene nanocage outside Si@Cu nanoparticle restricts polarization and pulverization of silicon inside itself. Graphene provides not only buffering space for core-shell Si@Cu nanoparticles to expand but also a conductive network to enhance the electronic conductivity and flexibility of the electrode. Therefore, the synergism of copper shells and graphene sheets improved electrochemical performance. The Si@Cu@rGO composites exhibited the reversible capacity of 2095.2 mAh g−1 at 200 mA g−1 after 50 cycles, showing extraordinary electrochemical performance. This outstanding Si@Cu@rGO anode becomes an ideal candidate for superior silicon-based lithium-ion battery applications. Image 1 • Si@Cu@rGO composite is fabricated by deposition-precipitation and one-step thermal reduction methods. • The synergism of copper shell and graphene greatly improved electrochemical performance. • Si@Cu@rGO anode exhibits high reversible capacity and excellent cycle capability. [ABSTRACT FROM AUTHOR]