Approaching High-Performance Lithium Storage Materials by Constructing Hierarchical CoNiO_(2)@CeO_(2)Nanosheets

In this work,the hierarchical CoNiO_(2)@CeO_(2)nanosheet composites were successfully prepared by a one-step hydrothermal process with a subsequent annealing process for the first time.The CeO_(2)nanoparticles successfully deposit on the surface of CoNiO_(2)nanosheet,and benefit the improvement of electrical contact between CoNiO_(2)and CeO_(2).CeO_(2)modification improve the reversibility of insertion/extraction of Li-ions and electrochemical reaction activity,and promotes the transport of Li-ions.Benefited of the unique architecture and component,the CoNiO_(2)@CeO_(2)nanosheet composites show high-reversible capacities,excellent cycling stability and good rate capability.The CoNiO_(2)@CeO_(2)(5.0 wt%)shows a charge/discharge capacity of 867.1/843.2 m Ah g^(-1)after 600 cycles at 1 A g^(-1),but the pristine CoNiO_(2)@CeO_(2)nanosheet only delivers a charge/discharge capacity of 516.9/517.6 m Ah g^(-1)after 500 cycles.The first-principles calculation reveals that valid interfaces between CeO_(2)and NiCoO_(2)can be formed,and the formation process of the interfaces is exothermic.The strong interfacial interaction resulting in an excellent structure stability and thus a cycling stability of the CoNiO_(2)@CeO_(2)material.This work provides an effective strategy to develop highperformance anode materials for advanced a lithium-ion battery,and the CoNiO_(2)@CeO_(2)nanosheet shows a sizeable potential as an anode material for next generation of high-energy Li-ion batteries.

Oxygen vacancies enriched nickel cobalt based nanoflower cathodes: Mechanism and application of the enhanced energy storage

The rational design of oxygen vacancies and electronic microstructures of electrode materials for energy storage devices still remains a challenge. Herein, we synthesize nickel cobalt-based oxides nanoflower arrays assembled with nanowires grown on Ni foam via the hydrothermal process followed annealing process in air and argon atmospheres respectively. It is found that the annealing atmosphere has a vital influence on the oxygen vacancies and electronic microstructures of resulting NiCo_(2)O_(4) (NCO-Air) and CoNiO_(2) (NCO-Ar) products, which NCO-Ar has more oxygen vacancies and larger specific surface area of 163.48 m^(2)/g. The density functional theory calculation reveals that more oxygen vacancies can provide more electrons to adsorb –OH free anions resulting in superior electrochemical energy storage performance. Therefore, the assembled asymmetric supercapacitor of NCO-Ar//active carbon delivers an excellent energy density of 112.52 Wh/kg at a power density of 558.73 W/kg and the fabricated NCO-Ar//Zn battery presents the specific capacity of 180.20 mAh/g and energy density of 308.14 Wh/kg. The experimental measurement and theoretical calculation not only provide a facile strategy to construct flower-like mesoporous architectures with massive oxygen vacancies, but also demonstrate that NCO-Ar is an ideal electrode material for the next generation of energy storage devices.

Three-dimensional porous CoNiO_(2)@reduced graphene oxide nanosheet arrays/nickel foam as a highly efficient bifunctional electrocatalyst for overall water splitting

It is crucial to develop high-performance and cost-effective bifunctional electrocatalysts for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)toward overall water splitting.Herein,a unique heterostructure of reduced graphene oxide(rGO)and CoNiO_(2) nanosheets directly grown on nickel foam(NF)were successfully fabricated and applied as a kind of highly efficient bifunctional electrocatalyst.The optimum CoNiO_(2)@rGO/NF electrode exhibits excellent elec-trocatalytic OER performance with an overpotential of only 272 mV to drive a current density of 100 mA·cm^(−2),and HER performance with an overpotential of 126 mV to achieve a current density of 10 mA·cm^(−2).Meanwhile,the electrodes also display outstanding long-term stability for OER and HER with negligible activity and morphology degradation after at least 40 h testing.Furthermore,when employed as both cathode and anode for overall water splitting,CoNiO_(2)@rGO/NF elec-trode only requires 1.56 V at 10 mA·cm^(−2) and operates stably for over 40 h,which is among the best performing Co-based and Ni-based non-precious metal electrocatalysts.Detailed characterizations reveal that the extraordinary electrocatalytic performance should be attributed to the synergistic effect of the unique heterostructure of CoNiO_(2) nanosheets and rGO for increasing the electrode conductivity and integrity,ultrasmall primary particle size for providing larger electrode/electrolyte contact area and abundant active sites,and three-dimensional(3D)conductive networks for facilitating the electrochemical reaction.