CoFe2O4 flower-like microspheres are prepared via a surfactant- and template-free method, involving the controlled hytrothermal synthesis firstly and a subsequent thermal decomposition treatment. The ...microspheres with diameters of 3–4 μm are characterized by the assembly of numerous porous and inter-connected lamella structures. Lithium-ion batteries electrodes based on the as-prepared CoFe2O4 microspheres show a high specific capacity of 733.5 mAh g−1 after 50 cycles at a current density of 200 mA g−1 and a good cyclic stability, as well as excellent rate capability. The enhanced electrochemical performance can be attributed to the hierarchical microsphere structure with high sufficient interfacial contact area between the microspheres and electrolyte, the short diffusion distance of Li+, better accommodation of structural stress and volume change with the lithiation/delithiation process. It is suggested that the CoFe2O4 microsphere is one of the most promising candidates for high-performance lithium-ion batteries.
CoFe2O4 flower-like microspheres were synthesized by a controlled AA-assisted hydrothermal process and subsequent annealing. The discharge capacity and cycle stability were greatly enhanced. Display omitted
•We prepared CoFe2O4 flower-like microspheres via a AA-assisted method.•The microspheres are assembled by numerous porous and inter-connected lamella structures.•The electrode shows high capacity, good cycle stability and enhanced rate performance.
A hierarchically Fe2O3@Co3O4 nanowire array is prepared by the aid of hydrothermal synthesis and sacrificial hydrolysis method. The obtained nanowire array shows hierarchical porosity and large ...surface area. The resulted Fe2O3@Co3O4 nanowire array is evaluated as an anode material for Li ion batteries, which exhibits high capacity and good cycle stability (1005.1 mAh g−1 after 50 cycles at a current density of 200 mA g−1) and an excellent rate performance, mainly owing to the unique hierarchical nanowire architecture and an elegant synergistic effect of two electrochemically active materials. The developed strategy can be readily generalized to construct other multifunctional hybrid nanostructures, which will be promising materials for high-performance electrochemical devices.
•We prepared Fe2O3@Co3O4 array by the hydrothermal and sacrificial hydrolysis method.•The porous Co3O4 nanowire act as the core and Fe2O3 nanoparticle as the shell layer.•The electrode shows high capacity, good cycle stability and enhanced rate performance.•This strategy can be generalized to construct other hybrid nanostructures.
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Exploring high performance cathode materials is of great means for the development of bi-functional electrochromic energy storage devices. Herein, Nb-doped WO3 mesoporous films as ...integrated high-quality cathode are successfully constructed via a facile sol-gel method. Chemical state and crystallinity of the WO3 based films are significantly influenced by doping concentration. Compared with the pure WO3, the optimal Nb-doped film shows improved optical-electrochemical properties with high specific capacity (74.4 mAh g−1 at 2 A g−1), excellent high-rate capability, large optical contrast (61.7% at 633 nm), and ultra-fast switching speed (3.6 s and 2.1 s for coloring and bleaching process, respectively). These positive features suggest the potential application of Nb-doped WO3 mesoporous cathode. Our research paves the way for the development of multifunctional photoelectrochemical energy devices.
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Improving the insulating nature of sulfur and retaining the soluble polysulfides in sulfur cathodes are crucial for realizing the practical application of lithium–sulfur batteries ...(LSBs). Biomass-based carbon is becoming increasingly popular for fabricating economical and efficient cathodes for LSBs owing to its unique structure. Herein, we report a facile strategy to transform bovine bone with an organic–inorganic structure into cellular hierarchical porous carbon via carbonization and KOH activation, followed by CoS2 modification through hydrothermal treatment. The synthesized composite can load abundant sulfur and produce a dual effect of “physical confinement and chemical entrapment” on polysulfides. The conductive carbon frame with the developed porous structure provides adequate space to accommodate sulfur and physically suppress the shuttle effect of polysulfides. The embedded half-metallic CoS2 sites can chemically anchor the polysulfides and enhance the electrochemical reaction activity as well. Owing to the multifunctional structure and dual restraint effect, the designed electrode exhibits enhanced electrochemical properties including high initial capacity (1230.9 mAh g−1 at 0.2 C), improved cycling stability and enhanced rate capability.
Lithium metal has always been considered as a “Holy Grail” of anode materials for high-energy-density batteries owing to its extremely high theoretical gravimetric capacity of 3860 mAh g−1 and the ...lowest electrochemical potential of −3.04 V. Unfortunately, huge challenges including unlimited dendrite growth and complex interfacial reaction accompanied with relatively low Coulombic efficiency have extremely restricted its practical applications for decades. In this review, we discuss recently exciting achievements in modifying Li metal anodes, particularly regarding porous structure design, surface modification, heterogeneous seed strategy, potential substitutes including Li powder, and pre-lithiated composite. Although each improvement method has its own advantage, we believe appropriate combination of them will yield more promising results. Finally, we discuss core issues and potential opportunities of Li metal anode, expecting to shed new light on future research in this field.
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•Main superiorities and challenges of Li metal anode are reviewed.•Recent developments of Li metal anodes are summarized.•Insight of various modification strategies is brightly given.•Future directions toward safe Li metal anode are suggested.
Pure Ni and three Ni–Co alloys films, i.e. Ni–4wt.%Co, Ni–18wt.%Co, and Ni–40wt.%Co, are electrodeposited at room temperature from the choline chloride/ethylene glycol deep eutectic solvent dissolved ...by nickel or/and cobalt chlorides. Electrodeposition mechanism, microstructure, and corrosion properties of the films are investigated. Surface morphology and chemical composite of the films are significantly dependent on the Ni2+ and Co2+ concentrations in the electrolytes. Interestingly, it is found that the amount of cobalt in the Ni–Co alloy films is significantly lower than that present in the electrolytes, which indicates an absence of anomalous codeposition process for the non-aqueous electrolytes. However, anomalous codeposition of Ni–Co deposits is frequently observed for the aqueous electrolytes. The Ni–Co alloy films possess face-centered cubic structures and refined grains revealed by X-ray diffractometer and scanning electron microscope. Potentiodynamic polarization measurements show that the Ni film exhibits the noblest corrosion potential and the lowest corrosion current compared with the Ni–Co alloys films. Moreover, the more Co content the Ni–Co films have, the more negative corrosion potential and the higher corrosion current the films exhibit.
► Electrodeposition of Ni–Co films from a deep eutectics system. ► Co2+ concentrations influence surface morphology and chemical composite of films. ► Ni–Co deposition with a non-anomalous codeposition process.
•Sm2O3 is well coated on LiLi0.2Mn0.56Ni0.16Co0.08O2 by simple wet chemical method.•The coated sample exhibits high capacity of 234.5mAhg−1 at 1C.•Capacity retention of 91.5% is obtained at 1C ...(200mAg−1) after 80 cycles 25°C.•EIS shows the thin Sm2O3 layer mainly reduces the charge transfer resistance.
Sm2O3-modified LiLi0.2Mn0.56Ni0.16Co0.08O2 was synthesized via a simple wet chemical process followed by a solid state reaction. A thin Sm2O3 layer with a thickness of about 2.5nm was uniformly coated on the surface of the Li-rich layered oxide particles. After Sm2O3 surface modification, high discharge capacity of 214.6mAhg−1 with a retention of 91.5% is obtained at a current density of 200mAg−1 between 2.0V and 4.8V after 80 cycles. Electrochemical impedance spectroscopy (EIS) shows that the thin Sm2O3 layer mainly reduces the charge transfer resistance and stabilizes the surface structure of the active material during cycling. Sm2O3 modification will be a promising approach to improve the cyclic stability of Li-rich layered oxides.
As promising battery-type electrode materials, layered single metal hydroxides (LSHs) including α-Ni(OH) 2 and α-Co(OH) 2 based hybrid supercapacitors exhibit larger operating voltages compared with ...those that are based on activated carbons and double-layer capacitance mechanisms. This study proposes a novel and facile room-temperature method to fabricate α-Ni(OH) 2 and α-Co(OH) 2 superstructures by using the double hydrolysis of Ni 2+ or Co 2+ and NCO − without the presence of any structure directing agent. Two dimensional sheet-like building blocks of the alpha-type metal hydroxide are assembled into various elegant morphologies including a 3D interconnected hierarchical assembly (3D-ICHA), sheet-on-sheet, sheet-on-rod and other nanostructures, which depends on the cation–anion mixing mode. Significantly, the 3D-ICHA α-Ni(OH) 2 possesses an ultrahigh specific surface area (320.2 m 2 g −1 ) and robust porous structure. An outstanding initial specific capacity (653.1 C g −1 at 1 A g −1 and 406 C g −1 at 20 A g −1 ) and an excellent cycling retention (86.2% in 20 000 cycles) were obtained for the 3D-ICHA α-Ni(OH) 2 , which stands out from most of the state-of-the-art α-Ni(OH) 2 powder-based materials. A high-loading asymmetric capacitor with excessive activated carbon (∼10 mg 3D-ICHA α-Ni(OH) 2 vs. ∼60 mg activated carbon) is demonstrated and it works very steadily even after 20 000 charge/discharge cycles.
Porous tin-based films are electrodeposited on copper foils from a choline chloride/ethylene glycol based electrolyte containing SnCl2·2H2O without any complexing agent or additive. Increasing the ...deposition time and voltage produces thicker films. The initially deposited Sn grains are relatively uniform with an average size of 200–300 nm and a kind of self-assembly distribution constructing an open and bicontinuous porous network. The architecture of these films possesses a double-layer structure, i.e. SnO2 (superficial layer)/Sn–Cu alloy (bottom layer), which is revealed by X-ray diffractometer and X-ray photoelectron spectroscopy. The electrochemical performance of the porous tin-based films as anode for lithium-ion batteries is measured. Although the capacity fades gradually with repeated cycling, a reversible capacity of 300-350 mAh g−1 is maintained for more than 50 cycles, which suggests that the in situ formed Sn--Cu alloy could provide an interlocking interface between active materials and current collector. Therefore, the tin's shedding from the current collector can be restrained. Moreover, the inactive materials, such as the oxide in the superficial layer and the Cu in the bottom layer, could also act as buffers to relieve the induced volume expansion of Sn during the repeated lithiathion/delithiation process, thus giving the good cycle performances.
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► Porous tin-based film with double-layer structure, i.e. SnO2/Sn–Cu. ► Tin-based film electrodeposited from Ethaline based electrolyte. ► Self-assembly distribution constructing an open and bicontinuous porous Sn network. ► Double-layer tin-based film delivering a satisfactory Li ion storage capacity.
Fe sub(2)O sub(3) nanospindles assembled with nanoparticles as primary building blocks are directly synthesized by a versatile ionothermal strategy in the choline chloride/urea mixture-based deep ...eutectic solvent system. The proposed ionothermal protocol is attractive and environmental friendly because choline chloride and urea are both naturally biocompatible compounds. As an anode material for lithium-ion batteries, the resultant Fe sub(2)O sub(3) nanospindles show high capacity and good cycle stability (921.7 mAh g super(-1) at a current density of 200 mA g super(-1) up to 50 cycles), as well as the excellent rate capability. The good electrochemical performance can be attributed to the nanospindle structure with high sufficient interfacial contact area between the active material and electrolyte, the short diffusion distance of Li ions. The environmentally benign strategy proposed in this study is expected to offer an attractive technique for the ionothermal synthesis of electrochemical energy storage materials.
