► In this paper, we attempt to address the poor kinetics of conversion reactions, the major drawback for it, by synchronously considering optimization design of electrode configuration and ...improvement of the lattice electronic conductivity of active materials. Results suggest Co-doped NiO nanoflake arrays electrode show high capacity, good cycling performance and rate capability. These can be attributed to the synthesis effect, coming from high electrode–electrolyte contact area, direct contact between each naonflake and current collector, fast Li+ diffusion and improvement of p-type conductivity of active materials.
Co-doped NiO nanoflake arrays with a cellular-like morphology are fabricated by low temperature chemical bath deposition. As anode material for lithium ion batteries (LIBs), the array film shows a capacity of 600mAhg−1 after 50 discharge/charge cycles at low current density of 100mAg−1, and it retains 471mAhg−1 when the current density is increased to 2Ag−1. Appropriate electrode configuration possesses some unique features, including high electrode–electrolyte contact area, direct contact between each naonflake and current collector, fast Li+ diffusion. The Co2+ partially substitutes Ni3+, resulting in an increase of holes concentration, and therefore improved p-type conductivity, which is useful to reduce charge transfer resistance during the charge/discharge process. The synergetic effect of these two parts can account for the improved electrochemical performance.
► We synthesize a hierarchically porous NiO film. ► The hierarchically porous NiO film possesses large surface area (196.8
m
2
g
−1). ► A specific capacitance of 200
F
g
−1 can be obtained at a ...discharging current of 20
A. ► 87% of capacitance is retained when the current density changes from 2 to 20
A
g
−1.
A hierarchically porous NiO film on nickel foam substrate is prepared by a facile ammonia-evaporation method. The self-assembled film possesses a structure consisting of NiO triangular prisms and randomly porous NiO nanoflakes. The pseudocapacitive behaviors of the porous NiO film are investigated by cyclic voltammograms and galvanostatic charge–discharge tests in 1
M KOH. The hierarchically porous NiO film exhibits a high discharge capacitance and excellent rate capability with 232
F
g
−1, 229
F
g
−1, 213
F
g
−1 and 200
F
g
−1 at 2, 4, 10, and 20
A
g
−1, respectively. The specific capacitance of 87% is maintained from 2
A
g
−1 to 20
A
g
−1. The porous NiO film also shows rather good cycling stability and exhibits a specific capacitance of 348
F
g
−1 after 4000 cycles.
Porous NiCo2O4 hetero-structure arrays on nickel foam are prepared by a facile hydrothermal method. The morphology of the arrays changes with the growth time. After hydrothermal synthesis for 8 h in ...combination with annealing treatment, the NiCo2O4 array presents a nanoflake–nanowire hetero-structure. The porous NiCo2O4 hetero-structure array exhibits the excellent pseudocapacitive properties in 2 M KOH, with a high capacitance of 891 F g−1 at 1 A g−1 and 619 F g−1 at 40 A g−1 before activation as well as excellent cycling stability. The specific capacitance can achieve a maximum of 1089 F g−1 at a current density of 2 A g−1, which can still retain 1058 F g−1 (97.2% retention) after 8000 cycles. The enhanced pseudocapacitive performances are mainly attributed to its unique hetero-structure which provides fast ion and electron transfer, large reaction surface area and good strain accommodation.
•Porous NiCo2O4 hetero-structure arrays on nickel foam were prepared by facile hydrothermal method.•The porous NiCo2O4 hetero-structure array exhibits excellent pseudocapacitive properties.•The specific capacitance achieves a maximum of 1089 F g−1 at a current density of 2 A g−1.•The specific capacitance can still retain 1058 F g−1 (97.2% retention) after 8000 cycles.
TiCN nanocomposite films are prepared by direct current magnetron sputtering from Ti
C combined target under different nitrogen flow rates. The composition, morphology and microstructure of the ...nanocomposite films are characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Hardness and tribological properties are tested by nanoindentation measurement and ball-on-disk tribometer, respectively. With the increase of nitrogen flow ranging from 0 to 30
sccm at a work pressure of 0.3
Pa, both crystallinity and sp
2 carbon content in the TiCN films increase. In addition, the ratio of TiN to Ti(C, N) increases as the nitrogen flow rate increases. The friction coefficient and wear rate could be greatly reduced due to the increase of sp
2 carbon and better toughness in the composite films. TiCN nanocomposite film with high hardness and good wear resistance is obtained under a nitrogen flow rate of 30
sccm.
► We prepared TiCN composite films by sputtering a Ti
C combined target. ► We studied the composition, mechanical and tribological properties in detail. ► XPS and TEM confirmed Ti(C,N) existed in the Ti
C
N composite films. ► sp
2-C content, ratio of TiN to Ti(C,N) did a great impact on the properties.
All the Li metal anode-based batteries suffer from a high propensity to form Li dendrites. To prevent the formation of dendritic lithium on the electrodes, amorphous carbon coatings are deposited ...onto the surface of metallic lithium foil by magnetron sputtering technique. The electrochemical performances of the amorphous carbon-coated lithium (Li/C) electrodes are investigated by galvanostatic charge/discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The compact carbon coatings on the surface of lithium foil can suppress the growth of dendritic lithium during charge–discharge process. The thickness of amorphous carbon coating affects the electrode from two aspects; the thick coating can prevent the formation of dendritic lithium much efficiently, but lead to a large impedance of Li+ transfer.
•Amorphous carbon coatings were deposited onto the surface of metallic lithium.•The formation of dendritic can be prevented according to the SEM photograph.•The electrochemical performance is promoted due to the existence of a-C coating.•The thickness of a-C coating affects the electrode performance from two aspects.
Macroporous Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials with high crystallinity and hexagonal ordering are synthesized by aerogel template followed by solid state reaction. High discharge capacities ...of 244.0 mA h g−1 and 153.9 mA h g−1 are obtained for the Li-rich layered oxide synthesized at 800 °C at current densities of 200 mA g−1 and 2000 mA g−1 between 2.0 V and 4.8 V. Increasing the synthesis temperature to 900 °C, the macroporous Li1.2Mn0.54Ni0.13Co0.13O2 delivers a high discharge capacity of 220.2 mA h g−1 at a current density of 200 mA g−1 with a capacity retention of 89.1% after 50 cycles, 129.8 mA h g−1 at a current density of 2000 mA g−1 and almost no capacity fading after 120 cycles. The diffusion coefficients of Li+ in the Li-rich layered oxide determined by galvanostatic intermittent titration technique are in the range of 5.0 × 10−18−8.0 × 10−14 cm2 s−1. Electrochemical impedance spectroscopy indicates that the macroporous structure with good particle contact of the layered oxide can improve its rate capability and cyclic stability.
•Macroporous LiLi0.2Mn0.54Ni0.13Co0.13O2 is synthesized via aerogel template.•High discharge capacity of 244.0 mA h g−1 is obtained at 1 C for LMNCO-800.•For LMNCO-900, 220.2 mA h g−1 is obtained at 1 C with enhanced cycle stability.•Capacity of 129.8 mA h g−1 is obtained at 10 C without any fading after 120 cycles.
Vertically aligned hierarchical WO3 nano-architectures on transparent conducting substrate (3×2.5cm2 in size and sheet resistance Rs=10Ω) are produced via a template-free solvothermal method. The ...nanostructured array films with thicknesses of about 1.1μm show remarkable enhancement of the electrochromic properties in visible spectrum and infrared region. In particular, a significant optical modulation (66.5% and 66.0% at 633nm, 73.8% and 53.9% at 2000nm, 57.7% and 51.7% at 8μm), fast switching speed (4.6s/3.6s and 2.0s/3.4s), high coloration efficiency (126 and 120cm2C−1 at 633nm) and excellent cycling stability (maintained 77.5% and 81.7% of the initial optical modulation after 4500-cycles) are achieved for the nanotree and nanowire arrays, respectively. The improved electrochromic properties are mainly attributed to the vertically aligned structure and the porous space among the nanotrees or nanowires, which make the diffusion of H+ in these arrays easier and also supply larger surface area for charge-transfer reactions.
Display omitted
•Vertically aligned WO3 nano-architectures are produced via a solvothermal method.•WO3 nano-architectures exhibit significant optical modulation and fast switching speed.•High coloration efficiency and excellent cycling performance are achieved for the nano-architectures.
► The surface of graphene is modified by nickel nanoparticles (Ni–NPs). ► The anchored Ni–NPs are in-suit reduced by graphene from NiO nanoparticles. ► Graphene–Ni hybrid electrode exhibits enhanced ...lithium storage performance. ► Ni–NPs enhance electronic transport and Li+ migration through SEI film.
The surface of graphene is modified by nickel nanoparticles which are in-situ reduced from NiO nanoparticles by graphene. The nickel nanoparticles obtained are up to 10nm in size and are strongly anchored on the surface of graphene sheets. As an anode material for lithium ion batteries, the graphene–Ni hybrid material delivers a reversible capacity of 675mAhg−1 after 35 discharge/charge cycles at a current density of 100mAg−1, corresponding to 85% retention of the initial charge capacity. In addition, the graphene–Ni hybrid electrode exhibits much better rate capability compared to its pure counterpart operated at various rates between 200 and 800mAg−1. Such enhanced lithium storage performance of the graphene–Ni hybrid electrode can be ascribed to the enhanced electronic transport and Li+ migration through the solid electrolyte interphase (SEI) film as a consequence of that the anchored nickel nanoparticles increase the electronic conductivity and modify the structure of SEI film covering the surface of graphene.
A compositive synthesis of gel polymer electrolytes by blending poly(propylene carbonate) (PPC) into poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) as a polymer host is proposed. The ...blending polymer is produced by a facile solution casting method and ester groups of PPC are successful introduced into PVDF-HFP. The gel polymer electrolyte displays an excellent ion conductivity of 1.18 × 10−3 S cm−1, broad electrochemical window up to 4.8 V (vs. Li/Li+) and outstanding electrochemical stability within rechargeable lithium batteries at room temperature. The improvement of ion conductivity is attributed to the decrease of polymer crystallizability and the increase of micro pores. The strategy of blending is promising for the modification of PVDF-HFP electrolyte and foreground application in next-generation solid energy conversion devices.
Li-rich layered oxide LiLi0.2Mn0.54Ni0.13Co0.13O2 is synthesized by combustion reaction using alcohol as both solvent and fuel. X-ray diffraction (XRD), scanning electron microscopy (SEM) and ...transmission electron microscopy (TEM) show that the oxide synthesized at 800 °C exhibits perfect crystallinity and lattice ordering, and has particle sizes of 50–150 nm. The layered oxide delivers an initial discharge capacity of 290.1 mAh g−1 at a current density of 20 mA g−1 after activation, and exhibits improved rate capability with high discharge capacities of 238.6 and 165.0 mAh g−1 at current densities of 200 and 2000 mA g−1 in the voltage range of 2.0–4.8 V, respectively. Low Li-ion diffusion coefficient of 1.07 × 10−14−1.01 × 10−16 cm2 s−1 is calculated by galvanostatic intermittent titration technique (GITT) during the initial discharge process, indicating that the improved rate capability is mainly attributed to the small particle sizes of the Li-rich oxide.
► Cathode material LiLi0.2Mn0.54Ni0.13Co0.13O2 is synthesized by combustion method. ► Alcohol is adopted as both solvent and fuel. ► Initial discharge capacity of 290.1 mAh g−1 is obtained at 20 mA g−1. ► High discharge capacity of 165.0 mAh g−1 is obtained at 2000 mA g−1. ► Diffusion coefficients of Li+ of 1.07 × 10−14–1.01 × 10−16 cm2 s−1 is obtained by GITT.
