Electrochemical performance of CoSb3/MWNTs nanocomposite prepared by in situ solvothermal synthesis

In situ solvothermally synthesized composite (SSC) and mechanically blended composite (MBC) of nanosized CoSb₃ and multiwalled carbon nanotubes (MWNTs) were prepared and investigated as potential anode materials for Li-ion batteries. It was found that SSC exhibits an entanglement structure of nanosized CoSb₃ and MWNTs and shows significantly better cycling stability than MBC. The reversible capacity of SSC electrode reaches 312 mA h g⁻¹ at the first cycle and remains above 265 mA h g⁻¹ after 30 cycles.     

Synthesis of uniform polycrystalline tin dioxide nanofibers and electrochemical application in lithium-ion batteries

Under optimized synthesis conditions, very large area uniform SnO₂ nanofibers consisting of orderly bonded nanoparticles have been obtained for the first time by thermal pyrolysis and oxidization of electrospun tin(II)2-ethylhexanoate/polyacrylonitrile (PAN) polymer nanofibers in air. The structure and morphology were elaborated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The SnO₂ nanofibers delivered a reversible capacity of 446 mAh g⁻¹ after 50 cycles at the 100 mA g⁻¹ rate and excellent rate capability of 477.7 mAh g⁻¹ at 10.0 C. Owing to the improved electrochemical performance, this electrospun SnO₂ nanofiber could be one of the most promising candidate anode materials for the lithium-ion battery.     

Mesoporous polyaniline or polypyrrole/anatase TiO2 nanocomposite as anode materials for lithium-ion batteries

A functional composite as anode materials for lithium-ion batteries, which contains highly dispersed TiO₂ nanocrystals in polyaniline matrix and well-defined mesopores, is fabricated by employing a novel one-step approach. The as-prepared mesoporous polyaniline/anatase TiO₂ nanocomposite has a high specific surface area of 224 m² g⁻¹ and a predominant pore size of 3.6 nm. The electrochemical performance of the as-prepared composite as anode material is investigated by cyclic voltammograms and galvanostatic method. The results demonstrate that the polyaniline/anatase nanocomposite provides larger initial discharge capacity of 233 mAh g⁻¹ and good cycle stability at the high current density of 2000 mA g⁻¹. After 70th cycles, the discharge capacity is maintained at 140 mAh g⁻¹. The excellent electrochemical performance of the polyaniline/TiO₂ nanocomposite is mainly attributed to its special structure. Furthermore, it is accessible to extend the novel strategy to other polymer/TiO₂ composites, and the mesoporous polypyrrole/anatase TiO₂ is also successfully fabricated.     

The preparation of nano-sulfur/MWCNTs and its electrochemical performance

In this work, a novel nano-sulfur/MWCNTs composite with modified multi-wall carbon nano-tubes (MWCNTs) as sulfur-fixed matrix for Li/S battery is reported. Based on different solubility of sulfur in different solvents, nano-sulfur/MWCNTs composite was prepared by solvents exchange method. The composite was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The modified MWCNTs are considered that not only acts as a conducting material, but also a matrix for sulfur. The electrochemical performance of the nano-sulfur/MWCNTs composite was tested. The results indicated that nano-sulfur/MWCNTs composite had the specific capacity of 1380 mAh g⁻¹, 1326 mAh g⁻¹ and 1210 mAh g⁻¹ in the initial cycle at 100 mA g⁻¹, 200 mA g⁻¹ and 300 mAh g⁻¹ discharge rates respectively, and remained a reversible capacity of 1020 mAh g⁻¹, 870 mAh g⁻¹ and 810 mAh g⁻¹ after 30 cycles. The electrochemical performances confirm that the modified MWCNTs as sulfur-fixed matrix show better ability than any other carbon in cathode of Li/S batteries that had been reported.     

A novel germanium/carbon nanotubes nanocomposite for lithium storage material

A new nanocomposite of Ge/carbon nanotubes (n-Ge/CNTs) was reported by a facile precursor method through a pyrolysis technique. Among it, germanium nanoparticles are encapsulated with a thin layer of amorphous carbon, which benefits to keep a good electronic contact with carbon nanotubes. Germanium nanoparticles are mainly supported inside the carbon nanotubes, which can effectively buffer the volume changes of Germanium. The composite was an effectively mixed (Li⁺ and e⁻) conducting network, which is vital to a quick Li insertion. The composite was shown to exhibit a reversible capacity of about 750 mAh g⁻¹ (74.4 mA g⁻¹) and an improved rate performance, compared with that of CNTs processed as the same condition. Our results demonstrated the composite to be a good active Li-storage material for Li batteries.     

Porous polythiophene as a cathode material for lithium batteries with high capacity and good cycling stability

Polythiophene (PTh) has been synthesized by chemical oxidative polymerization and used as an active cathode material in lithium batteries. The lithium batteries are characterized by cyclic voltammetry (CV), galvanostatic charge/discharge cycling and electrochemical impedance spectroscopic studies (EIS). The lithium battery with the PTh cathode exhibits a discharge voltage of 3.7 V compared to Li⁺/Li and excellent electrochemical performance. PTh can provide large discharge capacities above 50 mA h g⁻¹ and good cycle stability at a high current density 900 mA g⁻¹. After 500 cycles, the discharge capacity is maintained at 50.6 mA h g⁻¹. PTh is a promising candidate for high-voltage power sources with excellent electrochemical performance.     

A novel micro-spherical CoSn2/Sn alloy composite as high capacity anode materials for Li-ion rechargeable batteries

Micro-scaled spherical CoSn₂/Sn alloy powders synthesized from oxides of Sn and Co via carbothermal reduction at 800 °C were examined for use as anode materials in Li-ion battery. The phase composition and particle morphology of the CoSn₂/Sn alloy composite powders were investigated by XRD, SEM and TEM. The prepared CoSn₂/Sn alloy composite electrode exhibits a low initial irreversible capacity of ca. 140 mAh g⁻¹, a high specific capacity of ca. 600 mAh g⁻¹ at constant current density of 50 mA g⁻¹, and a good rate capability. The stable discharge capacities of 500-515 mAh g⁻¹ and the columbic efficiencies of 95.8-98.1% were obtained at current density of 500 mA g⁻¹. The relatively large particle size of CoSn₂/Sn alloy composite powder is apparently favorable for the lowering of initial capacity loss of electrode, while the loose particle structural characteristic and the Co addition in Sn matrix should be responsible for the improvement of cycling stability of CoSn₂/Sn electrode.     

Synthesis and electrochemical performance of novel loose structured submicro/micro-sized NiSnx alloy composites for lithium batteries

An effective method of carbothermal reduction was employed to prepare spherical microcrystal NiSn_x alloy powders from oxides of Sn and Ni used as anode materials for Li-ion battery. According to XRD, SEM and TEM analysis, the synthesized spherical NiSn_x powders show a loose submicro/micro-sized structure and a multi-phase composition. The prepared NiSn_x alloy composite electrode exhibits a stable discharge capacity of electrode is ca. 380 mAh g⁻¹ at constant current density of 50 mA g⁻¹, and can be retained at 350 mAh g⁻¹ after 25 cycles. Moreover, NiSn_x alloys exhibit excellent high rate performance, i.e. stable discharge capacities of 300-310 mAh g⁻¹ and the coulombic efficiencies of 97.5-99.5% have been obtained at the current density of 500 mA g⁻¹. The loose submicro-sized particle structural characteristic and the Ni addition in Sn matrix should be responsible for the improvement of cycling stability of NiSn_x electrode. The carbothermal reduction method is simple, low-cost and mass-productive, which should be viable to other alloy composite materials system of rechargeable lithium ion batteries.     

Nanodispersed iron, tin and antimony in vapour grown carbon fibres for lithium batteries: an EPR and electrochemical study

The use of iron-, tin- and antimony-containing carbon fibres as potential candidates for the negatives electrode of advanced lithium-ion batteries is described. Two different types of fibres are used: non-graphitic and partially graphitized carbon. EPR results show that both carbon and dispersed iron participate in redox processes during the electrochemical reaction with Li. Lithium test cells evidence higher capacities for partially graphitized fibres. The addition of dispersed tin or antimony is used to improve the capacity of the non-graphitic fibres by formation of lithium-tin and lithium-antimony compounds. Reversible capacity values close to 300 mA h g⁻¹ are achieved in both partially graphitized and composite electrodes containing Li-alloying elements. The use of nanodispersed transition metals, i.e. iron, in a carbon matrix is proposed here as an alternative to carbon composites containing Li-alloying elements.     

Rice husk-derived SiOx@carbon nanocomposites as a high-performance bifunctional electrode for rechargeable batteries

This paper we use ZnCl₂ to activates and reduces rice husks to produce SiO_x@N-doped carbon core-shell nanocomposites with inner voids is a facile and effective strategy to improve the electrochemical performance. As an anode material for the lithium-ion batteries, the composites exhibit a high reversible capacity (1315 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹) and long-term stability (584 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). Such outstanding cycling stability is attributed to the small size of the SiO_x particles with inner voids and the carbon layer coating can guarantee good structural integrity for long cycle stability. As a cathode material for Li–S batteries, the composite displays a high capacity and good stability (675 mAh g⁻¹ after 100 cycles at 0.1C). Its good performance and facile preparation will improve the utilization of rice husk waste.     

One step solid state synthesis of FeF3·0.33H2O/C nano-composite as cathode material for lithium-ion batteries

Nanometer-sized FeF₃·0.33H₂O/acetylene black composite has been synthesized by one step chemico-mechanical ball-milling process using Fe (NO₃)₃?9H₂O and NH₄F as precursors and investigated as cathode materials for secondary lithium batteries. The obtained FeF₃·0.33H₂O/C composite was described in terms of structure, morphology, and electro-chemical performance. The composite exhibited a noticeable capacity of 233.9 mAh g⁻¹ at a current density of 20 mA g⁻¹ within potential range 1.8–4.5 V and good rate capability. These results showed that FeF₃·0.33H₂O/C nano-composite prepared from an easily scalable chemico-mechanical ball-milling process was of great industrial interest.     

Electrochemical performances of Al-based composites as anode materials for Li-ion batteries

Al-C, Al-Fe and Al-Fe-C composite materials have been prepared by high-energy ball milling technique. The electrochemical measurements demonstrated that the Al-Fe-C composites have greatly improved electrochemical performances in comparison with Al, Al-C and Al-Fe anode. For example, Al₇₁Fe₉C₂₀ can deliver the reversible capacity of 436 mAh g⁻¹ at first cycle and 255 mAh g⁻¹ at 15th cycle. This improved electrochemical performance could be attributed to the alloying formation of Al with Fe and the buffering effect by the graphite matrix. This suggests that the Al-Fe-C composite has a potential possibility to be developed as an anode material for lithium-ion batteries.     

Hydrothermal synthesis of flower-like Zn2SnO4 composites and their performance as anode materials for lithium-ion batteries

Flower-like Zn₂SnO₄ composites had been prepared through a green hydrothermal synthesis. The structural, morphological and electrochemical properties were investigated by means of XRD, BET, SEM, TEM, and electrochemical measurement. The results show that the as-prepared sample is in high purity phase and of good crystallinity; meanwhile it has a particular 3-D structure and large surface area. Electrochemical measurement suggests that flower-like Zn₂SnO₄ composites exhibit better cycling properties and lower initial irreversible capacities than the solid Zn₂SnO₄ cubes. The first discharge and charge capacities of the material are 1750 mA h g⁻¹ and 880 mA h g⁻¹ respectively. A higher reversible capacity of 501 mA h g⁻¹ was obtained after 50 cycles at a current density of 300 mA g⁻¹. The higher reversible capacity and good stability can be related to the special nanostructural features of the material. Such Zn₂SnO₄ structures synthesized by the simple and cheap method are expected to have potential application in energy storage.     

Novel tin-graphite composites as negative electrodes of Li-ion batteries

For the purpose of obtaining an improved performance of the graphite negative electrode of Li-ion batteries, a novel graphite-tin composite has been synthesized by reduction of tin chloride (SnCl₂) with KC₈ in THF medium. This composite contains nano-sized tin particles dispersed on the graphite surface and free tin aggregates. Lithium electrochemical insertion occurs both in graphite and in tin. An experimental reversible specific charge of 489 mA h g⁻¹ is found stable upon cycling. Such a value is lower than the maximum theoretical one of 609 mA h g⁻¹ suggesting that only a part of tin is involved in the lithium insertion/extraction process. This part of active tin responsible for the stable capacity could be that bound to graphite. To the contrary, free tin aggregates could contribute to an extra capacity that decreases upon cycling in relation with the volume changes that occurs during alloying/dealloying.     

Study of the electrochemical hydrogen storage properties of the proton-conductive perovskite-type oxide LaCrO3 as negative electrode for Ni/MH batteries

LaCrO₃ was prepared by glycine combustion method and investigated as negative electrode for Ni/MH batteries. The structures of the as-calcined powder and the 20th charge-discharge cycle sample were characterized by XRD. The electrochemical experimental results demonstrated that the LaCrO₃ electrode showed excellent electrochemical reversibility and considerably high charge-discharge capacity at various temperatures. Except for the charge-discharge cycle at 298 K, the discharge capacities of LaCrO₃ electrode keep steady at 107.1 mA h g⁻¹and 285 mA h g⁻¹ at 313 K and 333 K after 5 cycles, respectively.     

Optimization of electrochemical properties of LiFePO4/C prepared by an aqueous solution method using sucrose

LiFePO₄ can be used as a positive electrode material for lithium-ion batteries by making composite with electrical conductive carbonaceous materials. In this study, LiFePO₄/C (carbon) composite was prepared by a soft chemistry route, in which sucrose was used as a carbon source of a low price. We tried to optimize a Li/(LiFePO₄/C) cell performance through changing synthetic conditions and discussed the factors affecting the electrochemical performances of the cell, such as the amount of the carbon source, synthetic temperature, gas flow rate of pyrolysis and the formation of secondary phases. It was found that the connection of the residual carbon and Fe₂P to LiFePO₄ particles and the amount of these two phases were important factors. In our experimental conditions, LiFePO₄/C including 9.72 wt.% of residual carbon, prepared at 800 °C for 12 h showed the highest reversible capacity and the best C rate performance among the synthesized materials; 130 mAh g⁻¹ at 10C rate and 50 °C.     

Preparation and performance of a core-shell carbon/sulfur material for lithium/sulfur battery

The core-shell carbon/sulfur material with high performance is prepared by a facile and fast deposit method in an aqueous solution. As sulfur ratio is 85% (w/w) in the composite, scanning electron microscope (SEM) and transmission electron microscope (TEM) observation show that the moniliform particles with 10 nm sulfur shells preserve the morphology of carbon cores. Tested as the cathode material in a lithium cell with binary organic electrolyte at room temperature, the composite shows excellent electrochemical performance. It exhibits a specific capacity up to 1232.5 mAh g⁻¹ at the initial discharge and its specific capacity remained above 800 mAh g⁻¹ after 50 cycles. Meanwhile, the composite also exhibits the high-rate behavior at 800 mA g⁻¹ of current density. Assuming a complete reaction to the final product, Li₂S, the utilization of the electrochemically active sulfur is about 85% at the initial cycle. Electrochemical impedance spectroscopy (EIS) is introduced to understand the impact of the microstructure of composite on electrochemistry. According to our study, a novel core-shell structural carbon/sulfur material is proposed and the key factors of the preparation are discussed.     

Synthesis and characterization of high-density LiFePO4/C composites as cathode materials for lithium-ion batteries

To achieve a high-energy-density lithium electrode, high-density LiFePO₄/C composite cathode material for a lithium-ion battery was synthesized using self-produced high-density FePO₄ as a precursor, glucose as a C source, and Li₂CO₃ as a Li source, in a pipe furnace under an atmosphere of 5% H₂-95% N₂. The structure of the synthesized material was analyzed and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical properties of the synthesized LiFePO₄/carbon composite were investigated by cyclic voltammetry (CV) and the charge/discharge process. The tap-density of the synthesized LiFePO₄/carbon composite powder with a carbon content of 7% reached 1.80 g m⁻³. The charge/discharge tests show that the cathode material has initial charge/discharge capacities of 190.5 and 167.0 mAh g⁻¹, respectively, with a volume capacity of 300.6 mAh cm⁻³, at a 0.1C rate. At a rate of 5C, the LiFePO₄/carbon composite shows a high discharge capacity of 98.3 mAh g⁻¹ and a volume capacity of 176.94 mAh cm⁻³.     

Synthesis and characterization of LiFePO4/(Ag + C) composite cathodes with nano-carbon webs

LiFePO₄/(Ag + C) composite cathodes with a new type of nano-sized carbon webs were synthesized by two methods of an aqueous co-precipitation and a sol-gel process, respectively. Simultaneous thermogravimetric-differential thermal analysis indicates that the crystallization temperature of LiFePO₄ is about 455-466 °C, which is close to the pyrolysis temperature of polypropylene, 460 °C. The silver and carbon co-modifying does not affect the olivine structure of LiFePO₄ but improves its kinetics in terms of discharge capacity and rate capability. Discharge capacities were improved from 153.4 mA h g^− 1 of LiFePO₄/C to 160.5 mA h g^− 1and 162.1 mA h g^− 1 for LiFePO₄/(Ag + C) cathodes synthesized by the co-precipitation and sol-gel methods, respectively. The possible reasons for the small difference in discharge capacity of two LiFePO₄/(Ag + C) cathodes were discussed. AC impedance measurements show that the Ag + C co-modification decreases the charge transfer resistance of LiFePO₄/(Ag + C) cathodes.     

Electrochemical properties and hydrogen storage mechanism of perovskite-type oxide LaFeO3 as a negative electrode for Ni/MH batteries

Perovskite-type oxide LaFeO₃ powder was prepared using a stearic acid combustion method. Its phase structure, electrochemical properties and hydrogen storage mechanism as negative electrodes for nickel/metal hydride (Ni/MH) batteries have been investigated systematically. The results of X-ray diffraction (XRD) analysis show that both the calcined powder and the charged/discharged samples after 10 cycles have orthorhombic structures. The discharge capacity, whose maximum value appeared at the first cycle, is 530.3 mA h g⁻¹ at 333 K and increases with an increase in temperature. The discharge capacity decreases distinctly during the first three cycles and then stays steady at about 80 mA h g⁻¹, 160 mA h g⁻¹ and 350 mA h g⁻¹ at 298 K, 313 K and 333 K, respectively. The hydrogen storage mechanism is studied by XRD, X-ray photoelectron spectroscopy (XPS) and mass spectrometry (MS), coupled with pressure-composition-temperature (PCT) methods. Hydrogen atoms may be intercalating into the oxide lattice and forming a homogeneous solid solution during the charging process.