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Rational design of novel structures plays a key role in achieving high specific capacities and fast charge rates with a long cycling life for battery-type electrodes of supercapacitors. To tackle capacity fading issues of battery-type electrode materials for supercapacitors, a new approach is proposed to form a bioinspired sea-sponge nanostructure of Ni/Ni(HCO3)2-on-C, synthesized through modifying triangle nanoflakes of Ni(HCO3)2 with partially in situ reduced Ni generated on sea-sponge-like porous carbon spheres (S-PCSs). The conductive skeleton of S-PCSs facilitates fast electron transfer and ion diffusion, and maintains the morphology of Ni(HCO3)2 triangle nanoflakes to ensure a high specific capacity of Ni/Ni(HCO3)2 nanoflakes. Simultaneously, the in situ reduced Ni acts as a capacity reservoir to prevent the fading of the specific capacity. When, applied as a positive electrode material, such sea-sponge nanostructures of Ni/Ni(HCO3)2-on-C exhibit a high specific capacity (472 mA h g−1) with a good rate capability (66% capacity retention at 32 A g−1vs. 8 A g−1), superior reversibility and cyclability (92% capacity retention after 10 000 cycles). An asymmetric supercapacitor based on Ni/Ni(HCO3)2-on-C//S-PCSs shows a high energy density of 51.3 W h kg−1 at a power density of 4 kW kg−1 with a capacitance retention of 89.6% over 6000 cycles. [ABSTRACT FROM AUTHOR]

CeO2 has been explored as an electro-catalyst for the cathode of lithium–oxygen batteries due to its good performance, especially in the initial discharging stage. In order to fully understand its initial oxygen reduction reaction (ORR), in this work, oxygen and lithium adsorptions and the initial ORR on stoichiometric and reduced CeO2 surfaces were systematically investigated using density functional theory (DFT) calculations. Changes of free energy values and structural parameters of the intermediates and precursors of the initial ORR were also studied to identify the possible reaction paths. It was found that the oxygen atoms are preferably adsorbed on the reduced CeO2 surface, whereas the lithium atoms are preferably adsorbed on both the stoichiometric and reduced CeO2 surfaces; therefore, there exists a strong adsorption at the site with high oxygen coordination. The reduced CeO2 with the surface oxygen vacancies was identified as the most critical surface for the initial oxygen reduction reaction. The path with the lithium adsorption as the first step was identified as the most probable one. A Li3O2 precursor was identified as the most possible initial structure of the catalyst to start the discharging process. [ABSTRACT FROM AUTHOR]

In this study, we report hierarchical TiO2 sphere–sulfur frameworks assisted with graphene as a cathode material for high performance lithium–sulfur batteries. With this strategy, the volume expansion and aggregation of sulfur nanoparticles can be effectively mitigated, thus enabling high sulfur utilization and improving the specific capacity and cycling stability of the electrode. Modification of the TiO2–S nanocomposites with graphene can trap the polysulfides via chemisorption and increase the electronic connection among various components. The graphene-assisted TiO2–S composite electrodes exhibit high specific capacity of 660 mA h g−1 at 5C with a capacity loss of only 0.04% per cycle in the prolonged charge–discharge processes at 1C. [ABSTRACT FROM AUTHOR]