Microwave assisted hydrothermal synthesis of tin niobates nanosheets with high cycle stability as lithium-ion battery anodes

SnNb₂O₆ and Sn₂Nb₂O₇ nanosheets were synthetized via microwave assisted hydrothermal method, and innovatively employed as anode materials for lithium-ion battery. Compared with Sn₂Nb₂O₇ and the previously reported pure Sn-based anode materials, the SnNb₂O₆ electrode exhibited outstanding cycling performance.     

Direct electrodeposition of Cu2Sb for lithium-ion battery anodes

We describe the direct single potential electrodeposition of crystalline Cu2Sb, a promising anode material for lithium-ion batteries, from aqueous solutions at room temperature. The use of citric acid as a complexing agent increases the solubility of antimony salts and shifts the reduction potentials of copper and antimony toward each other, enabling the direct deposition of the intermetallic compound at pH 6. Electrodeposition of Cu2Sb directly onto conducting substrates represents a facile synthetic method for the synthesis of high quality samples with excellent electrical contact to a substrate, which is critical for further battery testing.     

Hydrothermal synthesis of peony-like CuO micro/nanostructures for high-performance lithium-ion battery anodes

The peony-like CuO micro/nanostructures were fabricated by a facile hydrothermal approach. The peonylike CuO micro/nanostructures about 3-5 μm in diameter were assembled by CuO nanoplates. These CuO nanoplates, as the building block, were self-assembled into multilayer structures under the action of ethidene diamine, and then grew into uniform peony-like CuO architecture. The novel peony-like CuO micro/nanostructures exhibit a high cycling stability and improved rate capability. The peony-like CuO micro/nanostructures electrodes show a high reversible capacity of 456 mAh/g after 200 cycles, much higher than that of the commercial CuO nanocrystals at a current 0.1 C. The excellent electrochemical performance of peony-like CuO micro/nanostructures might be ascribed to the unique assembly structure, which not only provide large electrode/electrolyte contact area to accelerate the lithiation reaction, but also the interval between the multilayer structures of CuO nanoplates electrode could provide enough interior space to accommodate the volume change during Li~+ insertion and de-insertion process.     

Exfoliated graphite nanosheets/carbon nanotubes hybrid materials for superior performance supercapacitors

Nanostructured hybrid material of exfoliated graphite nanosheets and carbon nanotubes (GNSNT) served as supercapacitor electrode materials was presented. The nanostructured hybrid was prepared by a facile chemical reduction method. The hybrid material was characterized by X-ray diffraction technique, transmission electron microscopy, scanning electron microscopy, cyclic voltammetry, galvanostatic charge/discharge cycling, and four-point probe conductivity measurement to represent a well-defined nanostructure possessing a vast number of active sites and delivering the ingredients for a fast effective charge separation network. Our results clearly demonstrated that the hybrid possess a superior performance. A specific capacitance value 266 F/g was obtained for GNSNT hybrid electrode at a current density of 0.1 A/g, while it was only 185 F/g for exfoliated graphite nanosheets (GNS). At a higher current density of 2 A/g, the GNSNT electrode still keeps a specific capacitance of 220 F/g, which is more than double that of GNS. This synergistic effect of the nanostructured hybrid material offers an effective network for charge separation and therefore renders a significantly enhanced specific capacitance and rate capability.     

Inexpensive methodology for obtaining flexible SnO2-single-walled carbon nanotube composites for lithium-ion battery anodes

Journal of Solid State Electrochemistry - A versatile and low-cost methodology for fabricating free-standing carbon graphite (CG)/SnO2/single-walled carbon nanotube (SWCNT) composites as anode...     

One-step solvothermal synthesis of single-crystalline TiOF2 nanotubes with high lithium-ion battery performance

Single-crystalline TiOF(2) nanotubes were prepared by a one-step solvothermal method. The nanotubes are rectangular in shape with a length of 2-3?μm, width of 200-300?nm, and wall thickness of 40-60?nm. The formation of TiOF(2) nanotubes is directly driven by the interaction between TiF(4) and oleic acid in octadecane to form the 1D nanorods, and this is followed by a mass diffusion process to form the hollow structures. The synthesis approach can be extended to grow TiOF(2) nanoparticles and nanorods. Compared with TiO(2), which is the more commonly considered anode material in lithium-ion batteries, TiOF(2) has the advantages of a lower Li-intercalation voltage (e.g., to help increase the total voltage of the battery cell) and higher specific capacities. The TiOF(2) nanotubes showed good Li-storage properties with high specific capacities, stable cyclabilities, and good rate capabilities.     

Kirkendall-effect-based growth of dendrite-shaped CuO hollow micro/nanostructures for lithium-ion battery anodes

Three-dimensional (3D) dendrite-shaped CuO hollow micro/nanostructures have been prepared via a Kirkendall-effect-based approach for the first time and have been demonstrated as a high-performance anode material for lithium-ion batteries. The as-prepared hollow structures were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electrochemical properties. A CuO hollow structure composed of nanocubes outside and a dense film inside was selected as a typical example of the optimized design; it exhibited significantly improved cyclability at a current rate of 0.5 C, with the average Coulombic efficiency of ∼97.0% and 57.9% retention of the discharge capacity of the second cycle after 50 cycles. The correlation between the structure features of the hollow CuO and their electrochemical behavior was discussed in detail. Smaller size of primary structure and larger internal space of electrode materials are crucial to better electrochemical performance. This work represents that Kirkendall effect is a promising method to fabricate excellent hollow electrode materials for Li-ion batteries.     

Yolk-shell Si/C composites with multiple Si nanoparticles encapsulated into double carbon shells as lithium-ion battery anodes

The conceptual design of yolk-shell structured Si/C composites is considered to be an effective way to improve the recyclability and conductivity of Si-based anode materials. Herein, a new type of yolk-shell structured Si/C composite(denoted as TSC-PDA-B) has been intelligently designed by rational engineering and precise control. In the novel structure, the multiple Si nanoparticles with small size are successfully encapsulated into the porous carbon shells with double layers benefiting from the strong etching effect of HF. The TSC-PDA-B product prepared is evaluated as anode materials for lithium-ion batteries(LIBs).The TSC-PDA-B product exhibits an excellent lithium storage performance with a high initial capacity of 2108 mAh g~(-1) at a current density of 100 mA g~(-1) and superior cycling performance of 1113 mAh g~(-1) over 200 cycles. The enhancement of lithium storage performance may be attributed to the construction of hybrid structure including small Si nanoparticles, high surface area, and double carbon shells, which can not only increase electrical conductivity and intimate electrical contact with Si nanoparticles, but also provide built-in buffer voids for Si nanoparticles to expand freely without damaging the carbon layer.The present findings can provide some scientific insights into the design and the application of advanced Si-based anode materials in energy storage fields.     

Mesoporous carbon material as cathode for high performance lithium-ion capacitor

The mesoporous carbon material with large pore volume and high surface area by a simple situ MgO template method is synthesized, which is utilized as cathode to assemble a high performance lithium ion capacitor.     

Silicon-containing anodes with high capacity loading for lithium-ion batteries

Comparative analysis of cycling performance of hybrid electrodes based on the MAG synthetic graphite mechanic mixtures with silicon nanopowder and “nano-Si/SiO₂/hard carbon” ceramic frame-ordered composite in 1 M LiPF₆ solution in a monofluoroethylene carbonate-ethyl methyl carbonate mixture (30: 70, v/v), added with 3 wt % vinylene carbonate and 2 wt % ethylene sulfite, is performed. The high capacity loading (up to 6.8 mA h cm^?2 at the electrode layer thickness of 37 μm) and acceptable accumulated irreversible capacity of the composite-containing electrodes are achieved, due to the electrodes’ high density and stable silicon-containing electrode/electrolyte interface formation.     

Silicon core-hollow carbon shell nanocomposites with tunable buffer voids for high capacity anodes of lithium-ion batteries

Silicon core-hollow carbon shell nanocomposites with controllable voids between silicon nanoparticles and hollow carbon shell were easily synthesized by a two-step coating method and exhibited different charge-discharge cyclability as anodes for lithium-ion batteries. The best capacity retention can be achieved with a void/Si volume ratio of approx. 3 due to its appropriate volume change tolerance and maintenance of good electrical contacts.     

Fabrication of polyacrylonitrile/lignin-based carbon nanofibers for high-power lithium ion battery anodes

Low-cost carbon nanofibers are fabricated from lignin, the second most abundant raw material in wood after cellulose and polyacrylonitrile mixture as a carbon precursor by electrospinning, followed by suitable heat treatments. As the lignin content in the precursor increases, the carbon nanofibers become thinner, as seen from scanning electron microscopy images. However, their carbon structure and electrochemical performance are found to be very similar, even though surface functional groups on carbon nanofibers are slightly different from each other. For example, in the initial charge (lithium insertion) and discharge (lithium deinsertion) process, the reversible specific capacities of the various carbon nanofibers come from different precursor ratios of lignin and polyacrylonitrile are similar. Even at a fast (7 min) charge and discharge condition, the carbon nanofibers prepared from the lignin-containing precursors show a discharge capacity of 150 mAh g^?1. The lignin-based carbon nanofibers thus show promise for use in high-power lithium ion battery anodes with low price.     

Interconnected sandwich structure carbon/Si-SiO_2/carbon nanospheres composite as high performance anode material for lithium-ion batteries

In the present work,an interconnected sandwich carbon/Si-SiO_2/carbon nanospheres composite was prepared by template method and carbon thermal vapor deposition(TVD).The carbon conductive layer can not only efficiently improve the electronic conductivity of Si-based anode,but also play a key role in alleviating the negative effect from huge volume expansion over discharge/charge of Si-based anode.The resulting material delivered a reversible capacity of 1094 mAh/g,and exhibited excellent cycling stability.It kept a reversible capacity of 1050 mAh/g over 200 cycles with a capacity retention of 96%.     

Polythiophene-coated nano-silicon composite anodes with enhanced performance for lithium-ion batteries

Herein, a new polythiophene-coated silicon composite anode material was prepared by in situ chemical oxidation polymerization method. The structure of this material was characterized by infrared spectroscopy, which proved that the oxidative polymerization of thiophene occurred mainly in α position. The polythiophene can provide the better electric contact between silicon particles. Therefore, the as-prepared Si/polythiophene composite electrodes achieve better cycling performance than the bare Si anode. The specific capacity of the composite electrode retains 478 mA h g^?1 after 50 cycles.     

Interconnected sandwich structure carbon/Si-SiO2/carbon nanospheres composite as high performance anode material for lithium-ion batteries

In the present work,an interconnected sandwich carbon/Si-SiO2/carbon nanospheres composite was prepared by template method and carbon thermal vapor deposition（TVD）.The carbon conductive layer can not only efficiently improve the electronic conductivity of Si-based anode,but also play a key role in alleviating the negative effect from huge volume expansion over discharge/charge of Si-based anode.The resulting material delivered a reversible capacity of 1094 mAh/g,and exhibited excellent cycling stability.It kept a reversible capacity of 1050 mAh/g over 200 cycles with a capacity retention of 96%.     

Structural and electrochemical properties of SnO2/nanocarbon families as lithium-ion battery anodes

Hybrid SnO₂/nanocarbon families (graphene nanosheets (GNSs), single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs) and carbon nanospheres (CNSs)) have been synthesized by a similar wet chemical method. SnO₂ nanoparticles are uniformly loaded on the surface of the nanocarbon families. As lithium battery anodes, their electrochemical properties of the reaction of lithium are investigated under the same conditions. To compare between them, SnO₂/GNSs have the largest capacity; SnO₂/GNSs and SnO₂/SWCNTs have high cyclability; and SnO₂/MWCNTs can maintain the capacity at high current density. Such behaviors are ascribed to their surface-to-volume ratio, structure flexibility, ion mobility and electron conductivity. The present results are the bases for their practical applications in lithium-ion battery anodes.     

Controlled synthesis of mesoporous carbon nanosheets and their enhanced supercapacitive performance

Mesoporous carbon nanosheets (MCNs) were synthesized using porous magnesium oxide (MgO) layer as the template precursor and resol as the carbon source. The morphology of the mesoporous carbon particles can be easily controlled by altering the mass ratio of MgO to resol. The structural characterization demonstrates that the interlaced MCNs can be formed when MgO/resol is 1:1 and they possess the carbon nanolayer with a thickness of about 5 nm and a width of about 200 nm. The quantities of mesopores and micropores endow the MCNs with a large surface area of 1,180 m²?g^?1 and a high pore volume of 1.56 cm³?g^?1. The supercapacitive performance of carbon products synthesized with various MgO/resol ratios was evaluated using cyclic voltammetry and galvanostatic charge–discharge techniques. The results show that the interlaced MCNs exhibit the highest specific capacitance of 241 F?g^?1, the best rate capability and cycling stability, which are attributed to the fast electrolyte ion transport or diffusion throughout the electrode matrix and effective utilization of the electrical double-layer capacitance of carbon layer.     

Electrochemical performance of graphene nanosheets as anode material for lithium-ion batteries

Graphene nanosheets (GNSs) were prepared from artificial graphite by oxidation, rapid expansion and ultrasonic treatment. The morphology, structure and electrochemical performance of GNSs as anode material for lithium-ion batteries were systematically investigated by high-resolution transmission electron microscope, scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy and a variety of electrochemical testing techniques. It was found that GNSs exhibited a relatively high reversible capacity of 672 mA h/g and fine cycle performance. The exchange current density of GNSs increased with the growth of cycle numbers exhibiting the peculiar electrochemical performance.