Hierarchical nanostructures that can be directly grown on a conducting substrate are a new trend in the design of active materials for high-performance lithium-ion batteries (LIBs). This article reports our design and fabrication of a 3D hierarchical ZnCo2O4 nanostructure (3D-ZCO-NS) directly grown on Ni foams. The goose-feather-like ZnCo2O4 bundled into a loose array structure with a large electrolyte contact area and good electrical and mechanical connection to the current collector. Electrochemical measurements confirmed the good performance of the electrode for reversible Li+ storage (specific capacity of 932 mAh g–1 in the 50th cycle at 1 A g–1) relative to a pasted electrode of 3D-ZCO-NSs (599 mAh g–1 in the 50th cycle at 0.1 A g–1).Keywords: direct growth; hierarchical nanostructures; lithium-ion battery; ZnCo2O4;

SnO2 nanocrystals have been successfully synthesized by a hydrothermal method assisted by biuret. When tested as the gas-sensing material, these hydrothermally processed SnO2 nanocrystals displayed an ultrasensitive response towards NO and ultrahigh selectivity due to their physicochemical nature.

Co3O4 nanosheet arrays (NSAs) were successfully grown on flexible carbon cloth (CC) by a simple electrochemical deposition method. The deposited films were composed of homogeneous ultrathin hierarchical porous Co3O4 nanosheets. Such Co3O4 NSAs/CC electrodes showed superior electrochemical performance, indicating a promising method to fabricate flexible electrodes for Li-ion batteries.

Hierarchical structures consisting of highly conductive Au nanoparticles decorated on NiO nanostructures could significantly improve electrical conductivity. Herein, the Au–NiO composite exhibits greatly improved rate performance as pseudo-capacitors, and a high specific capacitance value of 619 F g−1 at a high rate of 20 A g−1, which is much higher than that of pure NiO electrodes (216 F g−1).

NiCo2O4 with higher specific capacitance is an excellent pseudocapacitive material. However, the bulk NiCo2O4 material prevents the achievement of high energy desity and great rate performance due to the limited electroactive surface area. In this work, NiCo2O4 nanosheet arrays were deposited on flexible carbon fabric (CF) as a high-performance electrode for supercapacitors. The NiCo2O4 arrays were constructed by interconnected ultrathin nanosheets (10 nm) with many interparticle pores. The porous feature of NiCo2O4 nanosheets increases the amount of electroactive sites and facilitates the electrolyte penetration. Hence, the NiCo2O4/CF composites exhibited a high specific capacitance of 2658 F g–1 (2 A g–1), good rate performance, and superior cycling life, suggesting the NiCo2O4/CF is a promising electrode material for flexible electrochemical capacitors.Keywords: carbon fabric; flexible; nanosheet arrays; NiCo2O4; supercapacitor;

Electrochemical supercapacitors have drawn much attention because of their high power and reasonably high energy densities. However, their performances still do not reach the demand of energy storage. In this paper β-cobalt sulfide nanoparticles were homogeneously distributed on a highly conductive graphene (CS–G) nanocomposite, which was confirmed by transmission electron microscopy analysis, and exhibit excellent electrochemical performances including extremely high values of specific capacitance (∼1535 F g−1) at a current density of 2 A g−1, high-power density (11.98 kW kg−1) at a discharge current density of 40 A g−1 and excellent cyclic stability. The excellent electrochemical performances could be attributed to the graphene nanosheets (GNSs) which could maintain the mechanical integrity. Also the CS–G nanocomposite electrodes have high electrical conductivity. These results indicate that high electronic conductivity of graphene nanocomposite materials is crucial to achieving high power and energy density for supercapacitors.

A facile, green strategy is explored to synthesize mesoporous Au/Li4Ti5O12 spheres based on in situ conversion of titanium glycolate in LiOH aqueous solution. Compared with TiO2 precursors, titanium glycolate possesses some strengths: (i) fast and easy preparation; (ii) direct reaction with LiOH without introduce of TiO2 impurity. In the synthesis, the produced chemical waste is only the mixed solvent of acetone and ethylene glycol (EG). Furthermore, acetone and EG in chemical waste can be easily separated by distillation and reused in the next synthesis process due to the great difference between their boiling points. In particular, the as-prepared mesoporous Au/Li4Ti5O12 spheres combines the advantages of large specific surface area (166 m2/g) and good electronic conduction enhanced by Au nanoparticles when used as an anode electrode material. The electrochemical tests show that the mesoporous Au/Li4Ti5O12 spheres display excellent high rate capability and cycling performance.Keywords: glycolate; high-rate; lithium ion batteries; lithium titanate; mesoporous; spheres;

Cobalt oxide nanowire array films have been prepared on large-area metallic substrates via a topochemical conversion route and have been demonstrated as advanced anode materials for high-performance lithium-ion batteries. Compared to previous reports, the cobalt oxide nanowire array electrodes will have good contact with the conducting substrates and an open space between neighboring nanowires, which provide an express pathway for charge transfer and facilitate diffusion of electrolyte into the inner region of the electrode. Besides these strengths, other ancillary materials such as binders and conductive additives are not required to enhance the system's conductivity and stability. After 50 successive cycles, the cobalt nanowire arrays are capable of retaining a specific capacity of 743 mAh g−1 with a very small capacity fading of 0.13% per cycle.

By employing microwave irradiation as a heat source, magnetite/graphene composites were synthesized by depositing Fe3+ in the interspaces of graphene sheets. The Fe3O4 nanoparticles were dispersed on graphene sheets. As anode materials for lithium ion batteries, they showed high reversible capacities, as well as significantly enhanced cycling performances (about 650 mA h g−1 after 50 cycles) and high rate capabilities (350 mA h g−1 at 5 C). The enhancement could be attributed to graphene sheets, which served as electron conductors and buffers. Our results opened a new doorway for the application of graphene sheets to prepare anode materials of lithium ion batteries with superior performances.

Porous SnO2 nanotubes were prepared via electrospinning followed by calcination in air. As anode materials for lithium ion batteries, the porous nanotubes delivered a high discharge capacity of 807 mAh g− 1 after 50 cycles. Even after cycled at high rates, the electrode still retained a high fraction of its theoretical capacity. Such excellent performances of porous SnO2 nanotubes could be attributed to the porous and hollow structure which facilitated liquid electrolyte diffusion into the bulk materials and buffered large volume changes during lithium ions insertion/extraction. Furthermore, the nanoparticles of nanotubes provided the shorter diffusion length for lithium ions insertion which benefited in retaining the structural stability and good rate performance. Our results demonstrated that this simple method could be extended for the synthesis of porous metal oxide nanotubes with high performances in the applications of lithium ion batteries and other fields.

Cobalt oxide nanowire array films have been prepared on large-area metallic substrates via a topochemical conversion route and have been demonstrated as advanced anode materials for high-performance lithium-ion batteries. Compared to previous reports, the cobalt oxide nanowire array electrodes will have good contact with the conducting substrates and an open space between neighboring nanowires, which provide an express pathway for charge transfer and facilitate diffusion of electrolyte into the inner region of the electrode. Besides these strengths, other ancillary materials such as binders and conductive additives are not required to enhance the system's conductivity and stability. After 50 successive cycles, the cobalt nanowire arrays are capable of retaining a specific capacity of 743 mAh g−1 with a very small capacity fading of 0.13% per cycle.

By employing microwave irradiation as a heat source, magnetite/graphene composites were synthesized by depositing Fe3+ in the interspaces of graphene sheets. The Fe3O4 nanoparticles were dispersed on graphene sheets. As anode materials for lithium ion batteries, they showed high reversible capacities, as well as significantly enhanced cycling performances (about 650 mA h g−1 after 50 cycles) and high rate capabilities (350 mA h g−1 at 5 C). The enhancement could be attributed to graphene sheets, which served as electron conductors and buffers. Our results opened a new doorway for the application of graphene sheets to prepare anode materials of lithium ion batteries with superior performances.

Hierarchical structures consisting of highly conductive Au nanoparticles decorated on NiO nanostructures could significantly improve electrical conductivity. Herein, the Au–NiO composite exhibits greatly improved rate performance as pseudo-capacitors, and a high specific capacitance value of 619 F g−1 at a high rate of 20 A g−1, which is much higher than that of pure NiO electrodes (216 F g−1).