Synthesis of confinement structure of Sn/C-C (MWCNTs) composite anode materials for lithium ion battery by carbothermal reduction

A composite anode material was prepared with confined tin into multiwall carbon nanotube by carbothermal reduction. The morphology and structure of Sn/C (nature graphite) and Sn/C-C (nature graphite + multiwall carbon nanotube) were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was revealed that the additive of MWCNT was a crucial factor to improve Sn /C composite anodes for cyclability and reversible capacity. Volume changes and morphological changes in Sn can be reduced by encasing MWCNT in a carbonaceous material that has sufficient flexibility to act as a buffer. Electrochemical performance test shows that the charge capacity of the Sn/C-C (NG + MWCNT) electrode in the fiftieth cycle was 400 mAh/g, which was higher than that of the Sn/C (NG) electrode. After 50 cycles, the retention of the Sn/C-C electrode and the Sn/C electrode was 80% and 63%, respectively.     

Tin-carbon composites as anodic material in Li-ion batteries obtained by copyrolysis of petroleum vacuum residue and SnO2

Composite materials with tin nanoparticles surrounded by a “muffling” carbon matrix are formed simultaneously by adding 20% SnO₂ to a vacuum residue and following carbonisation between 700 °C and 1000 °C. The primary purpose of the carbonaceous material is the reduction of SnO₂, giving rise to SnS and Sn as nanoparticles. The homogenous distribution of both components induces therefore a synergetic effect on the properties of the electrode material, not only from the electrochemical point of view but also from that mechanical. Thus, the carbon matrix hinders the agglomeration of Li-Sn alloys during long term cycling and, simultaneously, tin particles improve the conductivity of the material and increase the overall capacity as compared with the reference carbon. In addition, a CVD treatment increases the performance of the material. ¹¹⁹Sn Mössbauer and ⁷Li MAS NMR spectroscopies allow a detailed study of partially charged/discharged samples and, therefore, the phases, steps and mechanisms occurring during the electrochemical process.     

Electrochemical properties of SnO2/carbon composite materials as anode material for lithium-ion batteries

SnO₂/carbon composite anode materials were synthesized from SnCl₄·5H₂O and sucrose via a hydrothermal route and a post heat-treatment. The synthesized spherical SnO₂/carbon powders show a cauliflower-like micro-sized structure. High annealing temperature results in partial reduction of SnO₂. Metallic Sn starts to emerge at 500 °C. High Sn content in SnO₂/carbon composite is favorable for the increase of initial coulombic efficiency but not for the cycling stability. The SnO₂/carbon annealed at 500 °C exhibits high specific capacity (∼400 mAh g⁻¹), stable cycling performance and good rate capability. The generation of Li₂O in the first lithiation process can prevent the aggregation of active Sn, while the carbon component can buffer the big volume change caused by lithiation/delithiation of active Sn. Both of them make contribution to the better cycle stability.     

以淀粉为碳源制备锂离子电池负极用Sn/C复合材料的研究

以玉米淀粉为碳源,锡酸钠为锡源,通过碳热还原的方法制备了Sn/C复合材料。采用XRD,SEM,TEM等手段对材料的结构和形貌进行表征。结果表明,以玉米淀粉为碳源,锡酸钠为锡源制备的Sn/C复合材料碳基体能对金属锡形成很好的分散和包覆,在结构上具有良好的稳定性;600℃处理得到的样品具有最佳的比容量和循环性能,其首次脱锂比容量为583 mA.h/g,循环10次后其充放电效率达95%。     

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.     

Electrochemical performance of Sn film reinforced by Cu nanowire

Sn/Cu nanowire composite film was electrodeposited on copper foil substrates and used as an anode material for lithium-ion batteries. The structure of the obtained composite film anode was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy. It was found that the Sn/Cu nanowire composite film anode showed a better cycle stability than Sn film anode, whereas the Sn/CNT composite film anode indicated poor capacity retention. It could be deduced that copper nanowire reinforced the Sn film anode due to the better wetting property of Sn on the surface of copper and reduced the loss of electric contact among tin particles in the Sn/Cu nanowire composite film anode.     

Study of carbonization behavior of polyacrylonitrile/tin salt as anode material for lithium‐ion batteries

Using polyacrylonitrile (PAN) as a template, a composite of tin salt/PAN nanofiber is facilely produced by an electrospinning technique. Under high‐temperature heat treatment, the carbonization of PAN and the crystal growth of tin oxide proceed simultaneously to form a composite structure of tin nanoparticles wrapped in carbon nanofibers (tin@CNF). The composite structure of tin@CNF is controllable by the precursor ratio of PAN with tin salt and the carbonization temperature. The sample Sn1Pan1_700, synthesized from the precursor with weight ratio of SnCl₂:PAN = 1:1 and carbonized at 700 °C, delivers the initial capacity of 1329.8 mAh g^?1 and remains at 741.1 mAh g^?1 at the 40th cycle. The proper morphology of tin nanoparticles wrapped in carbon nanofibers plays an important role in specific capacity and cyclic performance, because the proper structure of carbon fiber hinders the aggregation of tin nanoparticles during the lithiation and delithiation processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016     

Electrochemical lithiation of new graphite-nanosized tin particle materials obtained by SnCl2 reduction in organic medium

SnCl₂ was reduced in the presence of graphite by t-BuONa-activated NaH. The resulting (tin/graphite)-based system was composed of nanosized tin particles deposited on the graphite surface and of free tin aggregates. Lithium electrochemical insertion occurs in graphite and in tin. A reversible specific charge of 500 mAh/g is found stable upon cycling.This value is lower than the maximum theoretical one (650 mAh/g) assuming a Sn/12C molar composition and the formation of the highest lithium content alloy Li₂₂Sn₅. It is suggested that the part of tin responsible for the stable reversible capacity is the one bound to graphite. To the contrary, free tin aggregates could contribute to a capacity which decreases upon cycling in connection with the volume changes accompanying lithium insertion/extraction in/out of these aggregates.     

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.     

SnO2 prepared by ion-exchange method of sodium alginate hydrogel as robust anode material for lithium-ion batteries

Tin-based anode materials are important components of lithium-ion batteries (LIBs) owing to their larger theoretical capacitance and lower working potential. However, the synthesis of tin-based anode materials is very complex, impeding their industrialization. In this work, tin dioxide nanoparticles were synthesized using sodium alginate hydrogel as a chelating agent for the ion-exchange reaction with tin tetrachloride. The resulting nano-tin dioxide was uniformly distributed with a porous structure morphology. The addition of sodium alginate at 0.1 g yielded a sample (SA-0.1) with a high reversible specific capacity, excellent multiplicative properties, and good cycling stability. After 702 cycles, the capacity of reversible discharge of the SA-0.1 maintained 621.1 mAh g^?1 at the current density of 0.5A g^?1, which cooperates with the facile synthesis method making the composite promising for commercialization.     

Effect of particle shape on the electrochemical properties of CaSnO3 as an anode material for lithium-ion batteries

Cubic and star-shaped CaSnO₃ particles with a perovskite structure were synthesized successfully using a simple hydrothermal method at a low temperature of 140 °C. The structure and morphology of the CaSnO₃ powders were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The electrochemical properties of the CaSnO₃ as anode materials for lithium-ion batteries were tested by constant current discharge/charge and cyclic voltammetry. The large irreversible capacity in the initial cycle was similar to that of tin oxide, due to the decomposition of tin oxide into metallic tin and Li₂O, followed by a reversible Li–Sn formation. The reversible capacity of the cubic CaSnO₃ was 382 mAh g^?1 in the first cycle and was maintained at 365 mAh g^?1 in the following cycles. The cubic CaSnO₃ particles had a higher reversible capacity than the star-shaped CaSnO₃ particles and retained a capacity of about 365 mAh g^?1 after 60 cycles as well as good cycle stability, showing potential as attractive anode materials for lithium-ion batteries. It is found that the particle shape had a marked effect on electrochemical performance.     

High-performance Sn–Ni alloy nanorod electrodes prepared by electrodeposition for lithium ion rechargeable batteries

To reduce irreversible capacity and improve cycle performance of tin used in lithium ion batteries, Sn–Ni alloy nanorod electrodes with different Sn/Ni ratios were prepared by an anodic aluminum oxide template-assisted electrodeposition method. The structural and electrochemical performance of the electrode were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and galvanostatic charge–discharge cycling measurement. The results showed that the copper substrate is covered with uniformly distributed Sn–Ni alloy nanorods with an average diameter of 250 nm. Different phases (Sn, Ni₃Sn₄ and metastable phases) of alloy nanorod formed in the electrodeposition baths with different compositions of Sn²⁺ and Ni²⁺ ions. Sn–Ni alloy nanorod electrode delivered excellent capacity retention and rate performance.     

Electrochemical reduction of trinitrotoluene on core-shell tin-carbon electrodes

In this work, we studied the electrochemical process of 2,4,6-trinitrotoluene (TNT) reduction on a new type of electrodes based on a core-shell tin-carbon Sn(C) structure. The Sn(C) composite was prepared from the precursor tetramethyl-tin Sn(CH₃)₄, and the product contained a core of submicron-sized tin particles uniformly enveloped with carbon shells. Cyclic voltammograms of Sn(C) electrodes in aqueous sodium chloride solutions containing TNT show three well-pronounced reduction waves in the potential range of −0.50 to −0.80 V (vs. an Ag/AgCl/Cl⁻ reference electrode) that correspond to the multistep process of TNT reduction. Electrodes containing Sn(C) particles annealed at 800 °C under argon develop higher voltammetric currents of TNT reduction (comparing to the as-prepared tin-carbon material) due to stabilization of the carbon shell. It is suggested that the reduction of TNT on core-shell tin-carbon electrodes is an electrochemically irreversible process. A partial oxidation of the TNT reduction products occurred at around −0.20 V. The electrochemical response of TNT reduction shows that it is not controlled by the diffusion of the active species to/from the electrodes but rather by interfacial charge transfer and possible adsorption phenomena. The tin-carbon electrodes demonstrate significantly stable behavior for TNT reduction in NaCl solutions and provide sufficient reproducibility with no surface fouling through prolonged voltammetric cycling. It is presumed that tin nanoparticles, which constitute the core, are electrochemically inactive towards TNT reduction, but Sn or SnO₂ formed on the electrodes during TNT reduction may participate in this reaction as catalysts or carbon-modifying agents. The nitro-groups of TNT can be reduced irreversibly (via two possible paths) by three six-electron transfers, to 2,4,6-triaminotoluene, as follows from mass-spectrometric studies. The tin-carbon electrodes described herein may serve as amperometric sensors for the detection of trace TNT.     

Charge-discharge characteristics of a layered-structure electroplated Cu/Sn anode for Li-ion batteries

An electroplated copper/tin (Cu/Sn) anode with a layered structure is described that minimizes the high-voltage irreversible capacity observed in an electroplated Sn anode at a potential over 1 V. The high-voltage irreversible capacity is caused by the electrolyte decomposition at the catalytic site of the Sn anode. In the electroplated Cu/Sn anode, the upper Cu layer effectively suppresses the exposure of the newly formed Sn surfaces, resulting in the absence of the high-voltage irreversible capacity. Therefore, the electroplated Cu/Sn anode exhibits a higher cycle performance than the electroplated Sn anode.     

纳米Sn／SnO2／石墨复合材料作为锂离子电池负极材料的研究

以氯化锡、氨水和无水乙醇为原料,采用溶胶一凝胶法制备纳米SnO2粉末,并与石墨、葡萄糖共热制备Sn／SnO2／石墨复合材料。用X射线衍射分析、透射电镜和电化学测试对材料进行了表征。采用该方法制备出的Sn／SnO2／石墨复合材料可逆容量可达680mA·h·g^-1,经过20次循环后容量基本稳定在380mA·h·g^-1。     

CZTSe solar cells prepared by electrodeposition of Cu/Sn/Zn stack layer followed by selenization at low Se pressure

Cu₂ZnSnSe₄ (CZTSe) thin films are prepared by the electrodeposition of stack copper/tin/zinc (Cu/Sn/Zn) precursors, followed by selenization with a tin source at a substrate temperature of 530°C. Three selenization processes were performed herein to study the effects of the source of tin on the quality of CZTSe thin films that are formed at low Se pressure. Much elemental Sn is lost from CZTSe thin films during selenization without a source of tin. The loss of Sn from CZTSe thin films in selenization was suppressed herein using a tin source at 400°C (A2) or 530°C (A3). A copper-poor and zinc-rich CZTSe absorber layer with Cu/Sn, Zn/Sn, Cu/(Zn + Sn), and Zn/(Cu + Zn + Sn) with metallic element ratios of 1.86, 1.24, 0.83, and 0.3, respectively, was obtained in a selenization with a tin source at 530°C. The crystallized CZTSe thin film exhibited an increasingly (112)-preferred orientation at higher tin selenide (SnSe _x ) partial pressure. The lack of any obvious Mo-Se phase-related diffraction peaks in the X-ray diffraction (XRD) diffraction patterns may have arisen from the low Se pressure in the selenization processes. The scanning electron microscope (SEM) images reveal a compact surface morphology and a moderate grain size. CZTSe solar cells with an efficiency of 4.81% were produced by the low-cost fabrication process that is elucidated herein.     

Enhanced Thermal Stability and Electrochemical Performance of Polyacrylonitrile/Cellulose Acetate-Electrospun Fiber Membrane by Boehmite Nanoparticles: Application to High-Performance Lithium-Ion Batteries

In this study, polyacrylonitrile/cellulose acetate (PAN/CA) composite nanofiber membranes with different boehmite contents are prepared by electrospinning. The physical and electrochemical properties of the composite nanofiber membrane as a separator in lithium batteries are investigated. In contrast to commercial polypropylene membrane (PP), the nanocomposite fiber membrane has a 3D network structure, higher porosity, higher thermal stability, higher electrolyte absorptivity, higher ionic conductivity, and better cycling performance. The PAN/CA composite membrane with 12 wt% boehmite has the highest ionic conductivity (1.694 mS cm⁻¹); the specific discharge capacity is 160 mAh g⁻¹ at 0.2 C discharge density and the highest capacity retention rate is 99.3% after 100 cycles. The cycle rate at 2 C has a higher capacity retention rate (88.75%). These results indicate that the PAN/CA/AlOOH composite nanofiber membrane can be expected to replace the commercial polyolefin membrane and behave as a high-performance separator for lithium-ion batteries.     

Polyterthiophene/CNT composite as a cathode material for lithium batteries employing an ionic liquid electrolyte

A polyterthiophene (PTTh)/multi-walled carbon nanotube (CNT) composite was synthesised by in situ chemical polymerisation and used as an active cathode material in lithium cells assembled with an ionic liquid (IL) or conventional liquid electrolyte, LiBF₄/EC-DMC-DEC. The IL electrolyte consisted of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄) containing LiBF₄ and a small amount of vinylene carbonate (VC). The lithium cells were characterised by cyclic voltammetry (CV) and galvanostatic charge/discharge cycling. The specific capacity of the cells with IL and conventional liquid electrolytes after the 1st cycle was 50 and 47 mAh g⁻¹ (based on PTTh weight), respectively at the C/5 rate. The capacity retention after the 100th cycle was 78% and 53%, respectively. The lithium cell assembled with a PTTh/CNT composite cathode and a non-flammable IL electrolyte exhibited a mean discharge voltage of 3.8 V vs Li⁺/Li and is a promising candidate for high-voltage power sources with enhanced safety.     

Nanostructural CoSnC anode prepared by CoSnO3 with improved cyclability for high-performance Li-ion batteries

Stannate, CoSnO₃, which mixes the elements Co and Sn evenly at the atomic level, was used as precursor to prepare CoSnC by a modified carbothermal reduction method. The synthesis process was characterized by differential thermal analysis (DTA) and X-ray diffraction (XRD). The particle feature was evaluated by transmission electron microscopy (TEM). The results indicated the as-prepared composite has a well-coated carbon layer that effectively prevents the encapsulated, low melting point alloy from out-flowing in a high-temperature treatment process. In addition, this structure, CoSn_x grains surrounded by carbon, prevents aggregation and pulverization of nanosized, tin-based alloy particles during charge/discharge cycling and improves the cycling stability of the alloy. The synthesized CoSnC integrates the merits of intermetallic compounds and nanosized anode materials and delivers a reversible capacity of 450 mA h g⁻¹ with a capacity retention of 72% after 50 cycles.     

Preparation of porous-structured LiFePO4/C composite by vacuum sintering for lithium-ion battery

The LiFePO₄/C (LFP/C) composite as a cathode material for lithium-ion battery was synthesized by solid-state reaction under vacuum sintering condition (20–5 Pa). The effects of vacuum sintering temperature and time on the phase composition, morphological structure, and electrochemical performance of LFP/C composite were investigated by X-ray diffraction, scanning electron microscopy, galvanostatic charge–discharge cycling test, and electrochemical impedance spectroscopy. The synthetic LFP/C composite possessed uniform particle-size distribution with porous architecture upon sintering at 650 °C for 12 h and thus exhibited the highest discharge capacity and best cycle performance. The complete decomposition of citric acid at a suitable temperature under vacuum condition resulted in the formation of porous structure. Compared with atmospheric argon sintering, vacuum sintering method led to the formation of porous architecture, the porous sample showed excellent cycle performance with less than 2% capacity loss after 80 cycles at 0.2 C, and reached the discharge specific capacity of 87.6 mAh g⁻¹ at 10 C rate, these are better than that of atmospheric argon sintering. The LFP/C composite prepared under vacuum sintering also reduced the optimum sintering temperature by nearly 100 °C compared with that prepared under atmospheric argon sintering.