A novel composite containing nanosized silicon and tin as anode material for lithium ion batteries

A novel composite consisting of nanosized Sn and Si as well as some lithium containing phases was synthesized by a mechanochemical reaction between SiO/SnO and Li using high energy mechanical milling (HEMM) with graphite as a dispersant, followed by a thermal treatment. The electrochemically active nanoclusters of Si and Sn derived by the mechanochemical reduction were uniformly distributed in the elastic matrix of lithium-containing phases and graphite. The difference in the reactive potential of Sn and Si with lithium was favorable for reducing the mechanical stress of the active hosts. Furthermore, the dispersion of Sn among the elastic matrix may contribute to an improved electrical connection among the Si based hosts and the current collectors. As a result, the composite presented a rechargeable capacity of 574.1 mAh g⁻¹ after 200 cycles. The capacity fading rate was thus calculated to be less than 0.2% per cycle. The cyclability of the composite was much superior to those of the SnO and SiO electrodes.     

Facile fabrication of porous NiMoO4@C nanowire as high performance anode material for lithium ion batteries

Herein, porous NiMoO₄@C nanowire is purposefully synthesized using oleic acid as carbon source, and further evaluated as high performance anode material for Li-ion batteries (LIBs). Compared with the pure NiMoO₄, porous NiMoO₄@C nanowire exhibits high reversible charge/discharge specific capacity, excellent cycle stability and preeminent rate capability. A stable reversible lithium storage capacity of 975 mAh g⁻¹ can still be maintained after 100 cycles at 200 mA g⁻¹. When the current density decreases back from 3000 mA g⁻¹ to 100 mA g⁻¹, a high discharge specific capacity of 884 mAh g⁻¹ is recovered. The porous structure and carbon layers can enhance the electronic transmission and structural stability, shorten the path lengths for ion and electron transport, and provide a mechanical buffer space to accommodate the volume expansion/contraction during the repeated Li⁺ insertion/extraction processes. All the results highlight that the porous NiMoO₄@C nanowire composite would be a promising candidate for high performance anode material of LIBs owing to its excellent electrochemical properties.     

Spherical NiO-C composite for anode material of lithium ion batteries

Spherical NiO-C composite was prepared by dispersing spherical NiO in glucose solution and subsequent carbonization under hydrothermal conditions at 180 °C. The microstructure and morphology of the NiO-C and NiO powders were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the electrodes were measured by galvanostatic charge-discharge tests, cyclic voltammetric analysis (CV), and electrochemical impedance spectroscopy (EIS). SEM images showed that the amorphous carbon not only coated on the surface but also filled the inner pores of the NiO spheres. Electrochemical tests showed that the NiO-C composite exhibited higher initial coulombic efficiency (66.6%) than NiO (56.4%), and better cycling performances. The improvement of these properties is attributed to the carbon, as it can reduce the specific surface area of porous sphere, and enhance the conductivity of porous NiO.     

Modified natural flake graphite with high cycle performance as anode material in lithium ion batteries

Natural flake graphite was mild-expanded and then carbon coated to enhance its cycle performance. The sample was investigated by scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The interlayer distance of graphite was slightly increased and many defects were introduced into graphite to form a porous structure. The mild-expanded graphite with pyrolysis carbon coating could accommodate up to 378 mAh g⁻¹ capacity and keep 100% capacity after 100 cycles. A mechanism is proposed that the increased interlayer distance and porous structure act as buffer for the change of graphite's volume in cycles, which greatly enhances the cycle stability. Porous structure also increases the capacity remarkably according to the micro-porous storage mechanism.     

Eutectoid WxC embedded WS2 nanosheets as a hybrid composite anode for lithium-ion batteries

A novel eutectoid structure, W_xC-embedded WS₂ nanosheets hybrids composite, was developed by hydrothermal reaction followed by a carbonization process. The fabricated WS₂–W_xC hybrid nanosheets electrode was used for lithium-ion batteries as an anode material, and demonstrated the specific capacity of 272 mA h·g^?1 at 0.01 A g^?1 with enhanced rate competence and cycling behavior when compared with individual WS₂ and W₂C electrode. While the large interlayer spacing in WS₂ facilitates rapid Li⁺ transport, the extremely high electronic conductivity of W_xC provides a highly conductive electron transfer pathway, which facilitates fast and reversible (de)lithiation reactions during charging and discharging. Further, these outcomes point the way for developing future eutectoid hybrid systems for advanced energy-storage applications.     

高容量硅基负极材料及其厚膜成型技术和性能

为了缓解硅基负极材料的体积膨胀并改善其电化学性能,以Mg、SiO和石墨为原料,成功制备出一种多相Si-MgO-G复合材料。探讨了不同高能球磨工艺对Mg和SiO反应程度的影响及厚膜成型技术的应用。结果表明,当高能球磨（1+5）h后,Mg和SiO原位反应生成Si-MgO产物,将反应产物与石墨混磨制备成多相Si-MgO-G复合材料。用XRD、SEM 和TEM等手段对制得材料的结构、形貌和成分进行分析,证实了复合材料是由Si、MgO和石墨组成,其中Si(220)//MgO(200)之间存在晶面共格关系。用CV和EIS等对捏合开炼厚膜技术制得负极极片进行电化学性能分析,结果表明,捏合开炼工艺制备的厚膜极片的厚度、载量和面积比容量分别约为薄膜极片的7.4倍、6.0倍和6.2倍。采用简单、绿色和可规模化生产的厚电极制备技术,可提高锂离子电池的面积比容量。     

A hierarchical porous carbon material for high power, lithium ion batteries

We synthesize a carbon anode material with unique nanostructure for high power lithium ion batteries. The carbon material is composed of numerous clusters of carbon nanobeads, and shows a macro-meso-micro hierarchical porous structure. This unique nanostructure appears to facilitate the rapid transfer of lithium ions and a very large ion adsorption. It exhibits a reversible capacity of 407.4 mAh g⁻¹ and its rate performance is drastically improved in comparison with that of the commercial graphite. The unique structure enables the anode to combine the advantages of both lithium ion batteries and electrochemical double layer capacitors, resulting in the good electrochemical performance.     

SiCN/C-ceramic composite as anode material for lithium ion batteries

The choice of electrode and electrolyte materials to design lithium batteries is limited due to the chemical reactivity of the used materials during the intercalation/deintercalation process. Amorphous silicon carbonitride (SiCN) ceramics are known to be chemically stable in corrosive environments and exhibit disordered carbonaceous regions making it potentially suitable to protect graphite from exfoliation. The material studied in this work was synthesized by mixing commercial graphite powder with the crosslinked polysilazane VL20^®. Pyrolysis of the polymer/graphite compound at appropriate temperatures in inert argon atmosphere resulted in the formation of an amorphous SiCN/graphite composite material. First electrochemical investigations of pure SiCN and of the SiCN/C composite are presented here. A reversible capacity of 474 mA hg⁻¹ was achieved with a sample containing 25 wt% VL20^® and 75 wt% graphite. The measured capacity exceeds that of the used graphite powder by a factor of 1.3 without any fading over 50 cycles.     

Electrochemical properties of Si–Ge–Mo anode composite materials prepared by magnetron sputtering for lithium ion batteries

Si–Ge–Mo composites are prepared using an RF/DC magnetron sputtering method, and their potential use as anode materials for rechargeable lithium-ion batteries is investigated. The Si–Ge–Mo composite films present an amorphous structure. The reaction mechanism of the Si–Ge–Mo with Li is investigated by various analytical techniques. The fabricated Si_0.41Ge_0.34Mo_0.25 composite film shows excellent electrochemical properties, including a high energy density (1st charge: 1193 mAh g⁻¹), long cycleability (ca. 870 mAh g⁻¹ over 100 cycles), and good initial Coulombic efficiency (ca. 96%). Additionally, when coupled with a LiCoO₂ cathode, the Si_0.55Ge_0.22Mo_0.23 composite electrode used as an anode shows excellent cycleability with a high energy density. The excellent electrochemical properties demonstrated by the Si–Ge–Mo composite film electrode confirm its potential as an alternative anode material for lithium-ion batteries.     

Carbon nanobeads as an anode material on high rate capability lithium ion batteries

Carbon nanobeads (CNBs) were prepared by reacting cyclohexachlorobenzene with dispersed sodium metal at 200 °C for 4 h. The CNBs prepared in this manner formed uniform nanobeads, with sizes ranging from 100 to 300 nm. Heating resulted in a reduction in the size of the CNBs, and improvements in their degree of crystallinity. The nanosized carbon materials considerably increased the surface area of the powder, reducing the distance of the intercalation/deintercalation pathway, substantially improving the charge capacity of the lithium ion battery at a high charging rate. The charge capacity of CNBs was found to be 238 mAh g⁻¹, while that of commercial MCMB reached only 36 mAh g⁻¹, when the charging rate was 1C (372 mAh g⁻¹). As the charging rate was further increased to 2C (744 mAh g⁻¹) and 3C (1116 mAh g⁻¹), the charge capacities of CNBs dropped to 173 and 111 mAh g⁻¹, respectively. The cyclic performance of the CNBs was measured and found to be significantly improved in comparison to other carbonaceous materials, for up to 100 cycles. Although cyclic performance did result in a gradual reduction in capacity, the CNBs still greatly exceeded the capacity of MCMB. These results clearly demonstrate the potential role of CNBs as anodes for high capacity Li ion batteries for use in the automobile industry.     

Pyrolytic polyurea encapsulated natural graphite as anode material for lithium ion batteries

Carbon encapsulated graphite was prepared by coating polyurea on the surface of natural graphite particles via interfacial polymerization followed by a pre-oxidation at 250 °C in air and a heat treatment at 850 °C in nitrogen. FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate the structure of the graphite before and after the surface modification. Galvanostatic cycling, dc impedance spectroscopy, and cyclic voltammetry were used to investigate the electrochemical properties of the modified graphite as the anode material of lithium cells. The modified graphite shows a large improvement in electrochemical performance such as higher reversible capacity and better cycleability compared with the natural graphite. It can work stably in a PC-based electrolyte with the PC content up to 25 vol.% because the encapsulated carbon can depress the co-intercalation of solvated lithium ion. The initial coulombic efficiency of C-NG and NG in non-PC electrolyte is 74.9 and 88.5%, respectively.     

An urchin-like graphite-based anode material for lithium ion batteries

In situ preparation of carbon nanotubes on the surface of spherical graphite particles is made by chemical vapor deposition, resulting in an “urchin-like” hybrid material. TEM and SEM images show that carbon nanotubes are herringbone with turbulent layered structure, less than 100 nm in diameter and several micrometers in length in the average. The hybrid's use as an anode material in lithium ion batteries is examined using constant current charge-discharge tests, which prove that carbon nanotubes oriented on the surface effectively improve the reversible capacity. Cyclic voltammogram shows that there is no cathodic peak for the reaction of the Fe catalyst with Li⁺ in the charge-charge process in 0.0-1.6 V vs. Li/Li⁺ potential range.     

Hard carbon/lithium composite anode materials for Li-ion batteries

Hard carbon/lithium composite anode electrode is prepared to reduce the initial irreversible capacity of hard carbon, which hinders practical application of hard carbon in lithium ion batteries, by introducing lithium into hard carbon. Lithium foil effectively compensates the irreversible capacity of hard carbon in the first cycle. A full cell using LiCoO₂ cathode and the composite anode shows much higher initial coulombic efficiency than that of a cell using LiCoO₂ cathode and hard carbon anode. This paves the way to reduce the large initial irreversible capacity of hard carbon. Besides that, this composite anode enables conductive polymer/sulfur composite cathode to be used in Li-ion batteries with non-lithiated anode materials.     

Carbon-coated silicon as anode material for lithium ion batteries: advantages and limitations

Carbon coating of silicon powder was studied as a means of preparation of silicon-based anode material for lithium ion batteries. Carbon-coated silicon has been investigated at various cycling modes vs. lithium metal. Ex situ X-ray data suggest that there is irreversible reduction of crystallinity of the silicon content. Since carbon layer preserving the integrity of the particle, the reversibility of the structural changes in the amorphous state Li-Si alloy provides the reversible capacity. The progressively decreased Coulomb efficiency with cycling indicates that more and more lithium ions are trapped in some form of Li-Si alloy and become unavailable for extraction. This is the main factor for the capacity fading during cycling. Qualitative studies of the impedance spectra of the electrode material at the first cycle for the fresh anode and at the last cycle after the anode capacity faded considerably and provide further support for this model of fading mechanism.     

Vanadium nitride as a novel thin film anode material for rechargeable lithium batteries

Vanadium mononitride (VN) thin films have been successfully fabricated by magnetron sputtering. Its electrochemical behaviour with lithium was examined by galvanostatic cell cycling and cyclic voltammetry. The capacity of VN was found to be stable above 800 mAh g⁻¹ after 50 cycles. By using ex situ X-ray diffraction, high-resolution transmission electron microscopy and selected area electron diffraction as well as in situ spectroelectrochemical measurements, the electrochemical reaction mechanism of VN with lithium was investigated. The reversible conversion reaction of VN into metal V and Li₃N was revealed. The high reversible capacity and good stable cycle of VN thin film electrode made it a new promising lithium-ion storage material for future rechargeable lithium batteries.     

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.     

An Sn-Fe/carbon nanocomposite as an alternative anode material for rechargeable lithium batteries

Sn-Fe/carbon nanocomposites were synthesized by the mechanochemical treatment of Sn with various amounts of an Fe/C composite through the pyrolysis of Fe(III) acetylacetonate. The composites were then evaluated as alternative anode materials for rechargeable lithium batteries. Based on the obtained ex situ X-ray diffraction (XRD) data, X-ray absorption spectroscopy (XAS) results, and differential capacity plots (DCPs), a reaction mechanism was suggested. It was found that increasing the amounts of the SnFe phase and pyrolyzed carbon in the composite improved its electrochemical characteristics in terms of its capacity retention.     

One-step synthesis of Li-doped NiO as high-performance anode material for lithium ion batteries

The poor electronic conductivity and huge volume expansion of NiO are the vital barriers when used as anode for lithium ion batteries. In order to solve above issues, Li-doped NiO are prepared by a facile one-step ultrasonic spray pyrolysis method. The effects of Li doping on the morphology, structure and chemical composition of the Li-doped NiO powders are extensively studied. When used as lithium ion batteries anode, it is demonstrated that the doping of Li has significant positive effect on improving the electrochemical performance. After 100 cycles at 400 mA g⁻¹, The Li-doped NiO samples deliver a discharge capacity of 907 mAh g⁻¹, much more than that of un-doped sample (736 mAh g⁻¹). The improved electrochemical performances can be ascribed to the improved p-type conductivity and lower impedance, which are confirmed by Rietveld refinement, X-ray photoelectron spectroscopy and electron impedance spectroscopy.     

Electrochemical performance of nano-Pt-supported carbon anode for lithium ion batteries

A nano-Pt-supported carbon anode was prepared by supporting Pt nanoparticles onto carbon powder. Ultrafine Pt nanoparticles could be well distributed on the surface of carbon particles. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), FTIR, and impedance spectroscopy were used to study on the electrode structure and electrochemical performance. Nano-Pt-supported carbon anode enhanced the Li discharge reaction and suppressed the solvent decomposition reaction, which are favorable for lithium batteries.     

Nanoscale SnS with and without carbon-coatings as an anode material for lithium ion batteries

SnS nanoparticles were mechnochemical synthesized and then co-heated with polyvinyl alcohol (PVA) at various temperatures to obtain carbon coating. All amorphous carbon-coated SnS particles had average particle size of about 20-30 nm, revealed by transmission electron microscopy (TEM). During discharge-charge, ex situ XRD results indicated that SnS firstly decomposed to Sn, then lithium ions intercalated into Sn. The reaction of Li⁺ and Sn was responsible for the reversible capacity in cycling process. The lithium ion insertion and extraction mechanism of SnS anode was similar to that of Sn-based oxide. Electrochemical capacity retention of carbon-coated SnS obtained at 700 °C was superior to that of other prepared SnS anodes and especially the rate capability was obviously enhanced due to good electric conductivity and buffering matrix effects of carbon coating.