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Abstract: A new type of CoO nanoparticles encapsulated by graphitable hollow carbon sphere (GHCS) composite material was synthesized. The core–shell structure CoO/GHCS composite shows the improved cyclability as an anodic material in Li-ion battery. The core–shell composite containing 50wt% CoO exhibits a reversible capacity of 584mAhg−1 at a constant current density of 100mAg−1 between 0 and 3.0V (vs. Li+/Li), and remains a capacity retention of 95% after 50th cycle. The improvement could be attributed to that the GHCS with a good electronic conductivity and high surface severs as dispersing medium to prevent CoO nanoparticles from aggregating, and provide the enough space to buffer the volume change during the Li-ion insertion and extraction reactions in CoO nanoparticles. [Copyright &y& Elsevier]

Abstract: We report a simple strategy to prepare a hybrid of lithium titanate (Li4Ti5O12, LTO) nanoparticles well-dispersed on electrical conductive graphene nanosheets as an anode material for high rate lithium ion batteries. Lithium ion transport is facilitated by making pure phase Li4Ti5O12 particles in a nanosize to shorten the ion transport path. Electron transport is improved by forming a conductive graphene network throughout the insulating Li4Ti5O12 nanoparticles. The charge transfer resistance at the particle/electrolyte interface is reduced from 53.9Ω to 36.2Ω and the peak currents measured by a cyclic voltammogram are increased at each scan rate. The difference between charge and discharge plateau potentials becomes much smaller at all discharge rates because of lowered polarization. With 5wt.% graphene, the hybrid materials deliver a specific capacity of 122mAhg−1 even at a very high charge/discharge rate of 30C and exhibit an excellent cycling performance, with the first discharge capacity of 132.2mAhg−1 and less than 6% discharge capacity loss over 300 cycles at 20C. The outstanding electrochemical performance and acceptable initial columbic efficiency of the nano-Li4Ti5O12/graphene hybrid with 5wt.% graphene make it a promising anode material for high rate lithium ion batteries. [Copyright &y& Elsevier]

Abstract: Nanocomposites of Mn3O4 nanoparticles and graphene (GR) nanosheets – Mn3O4@GR can be made by growing Mn3O4 nanoparticles directly on the surfaces of GR in solvothermal reactions. The asymmetric supercapacitors constructed with Mn3O4@GR as positive and activated carbon (AC) as negative electrodes, respectively, show highly enhanced performances in energy storage. It was found that the electrolytes employed in constructing electrodes of the devices can influence the performances of Mn3O4@GR supercapacitors dramatically. Compared to their energy density in KOH electrolyte, the devices exhibit improved charge storage performances in Na2SO4 electrolyte. Furthermore, the charge storage abilities of the devices are closely related to the amount of Mn3O4 nanoparticles loaded onto the surface of GR nanosheets. The performances of Mn3O4@GR//AC asymmetric supercapacitors can be optimized by carefully tailoring the composition of electrode materials and adjusting the electrolytes for making the devices. [Copyright &y& Elsevier]