Nano-porous SiO/carbon composite anode for lithium-ion batteries

Carbon-coating of sub-μm SiO particles (d_max = 0.36 μm, d₅₀ = 0.69 μm) by a fluidized-bed chemical-vapor-deposition process has produced unique nano-porous SiO/C secondary particles within which the SiO primary particles are “glued” together by carbon to form a network that possesses randomly distributed pores with sizes in the nano-meter range and a bulk porosity of >30%. Upon lithiation/delithiation cycling in an organic Li-ion electrolyte, the electrode made of the SiO/C particles exhibited reduced polarization, smaller irreversible electrode expansion, and remarkably enhanced cycling performance, as compared with that of pristine SiO particles. The reduced electrode expansion exhibited by the SiO/C electrode can be attributed to the combination of diluted SiO content and presence of pre-set voids, which could partially accommodate volume expansion arising from lithiation of the SiO primary particles. These effects render the SiO/C electrode structurally more robust than the SiO electrode against volumetric variations upon cycling.     

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%。     

Single wall carbon nanotube paper as anode for lithium-ion battery

“Free-standing” single wall carbon nanotube (SWNT) papers have been synthesised by simple filtration method via positive pressure. A conventional SWNT slurry coated electrode was fabricated to compare with the SWNT papers. The results show that the capacity of the “Free-standing” electrode was slightly lower than that of the conventional electrode, but the “Free-standing” electrode was produced without any binder, and metal substrate, so that the weight of electrode was reduced significantly. On the other hand, the procedures for SWNT electrode preparation were simplified, so the cost of the manufacturing could be reduced.     

Preparation and characterization of carbon cryogel (CC) and CC-SiO composite as anode material for lithium-ion battery

Carbon cryogel (CC) has been prepared through sol-gel polycondensation of resorcinol (R) with formaldehyde (F) followed by freeze-drying and carbonization in this work. The characteristics and lithium-ion insertion-extraction property have been investigated for the first time. Based on the results that CC has very excellent cycling stability but very limited lithium-ion charge-discharge capacity, SiO is employed to synthesize CC-SiO composite by high energy mechanical ball-milling to improve the applicability. The results showed that, CC-SiO is composed of active carbon, graphite, SiO and dispersed Si crystal, while CC is composed of active carbon and graphite. CC-SiO has smaller and much more uniform particles than CC. SiO can greatly improve discharge capacity of CC with an acceptable sacrifice of cycling stability, and the charge-discharge capacity of CC-SiO comes mainly from lithium insertion-extraction in Si-SiO in the sample. CC-SiO has excellent high-rate discharge ability and is promising anode material of lithium-ion battery for use of high power density purpose.     

A novel nickel-based mixed rare-earth oxide/activated carbon supercapacitor using room temperature ionic liquid electrolyte

Mesopore nickel-based mixed rare-earth oxide (NMRO) and activated carbon (AC) with rich oxygen-contained groups were prepared as electrode materials in a supercapacitor using room temperature ionic liquid (RTIL) electrolyte. These electrode materials were characterized by XPS, XRD, N₂ adsorption, SEM as well as various electrochemical techniques, and showed good properties and operated well with RTIL electrolyte. A 3 V asymmetrical supercapacitor was fabricated, which delivered a real power density of 458 W kg⁻¹ as well as a real energy density of 50 Wh kg⁻¹, and during a 500-cycle galvanostatic charge/discharge measurement, no capacity decay was visible. Such promising energy-storage performance was to a large extent ascribed to nonvolatile RTIL electrolyte with wide electrochemical windows and high stable abilities worked with both electrode materials.     

SnO2-coated multiwall carbon nanotube composite anode materials for rechargeable lithium-ion batteries

SnO₂-coated multiwall carbon nanotube (MWCNT) nanocomposites were synthesized by a facile hydrothermal method. The as-prepared nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The SnO₂/MWCNT composites, when combined with carboxymethyl cellulose (CMC) as a binder, show excellent cyclic retention, with the high specific capacity of 473 mAh g⁻¹ beyond 100 cycles, much greater than that of the bare SnO₂ which was also prepared by the hydrothermal method in the absence of MWCNTs. The enhanced capacity retention could be mainly attributed to good dispersion of the tin dioxide particles in the matrix of MWCNTs, which protected the particles from agglomeration during the cycling process. Furthermore, the usage of CMC as a binder is responsible for the low cost and environmental friendliness of the whole electrode fabrication process.     

锂离子电池用有机电解液的制备技术

分析了有机电解液在锂离子电池中的作用以及锂离子电池对有机电解液的要求,介绍了有机电解液的制备方法以及制备过程中的控制技术,根据锂离子电池的发展方向,提出了提高有机电解液质量及应用性能的途径。     

Novel synthesis of SiOx/C composite as high-capacity lithium-ion battery anode from silica-carbon binary xerogel

Micro/nanostructured SiO_x/C composite was firstly synthesized by carbothermal reduction of silica-carbon binary xerogel. The homogeneous dispersion feature of the two components in binary xerogel contributes to effectively carbothermally reduce the O/Si atomic ratio, enhancing the electrochemical activity of the SiO_x component.The micron-sized SiO_x/C spheres are composed of many near-spherical nanoparticles. The synthesized SiO_x/C exhibits a stable and high reversible capacity of 830 m A·h·g~(-1) for 100 cycles, and excellent rate-capability. The homogeneous dispersion structure of phases, the micro/nanostructure and the high electrochemical activity of SiO_x component combinedly contribute the excellent electrochemical performance.     

Effect of the pitch-based carbon anode on the capacity loss of lithium-ion secondary battery

The total capacity loss of lithium-ion secondary cell is reduced by engineering the pitch-based carbon anode through one or more of the following methods: attaining a high degree of graphitization, minimizing the surface oxygen concentration, attaining a large crystal size L_c, degassing, and use of PVDF in place of teflon as the binder.     

A Si-SnSb/pyrolytic PAN composite anode for lithium-ion batteries

Polyvinyl chloride (PVC) powders are introduced as carbon sources to prepare Si-SnSb alloy based on carbothermal method. Then the as-prepared alloy was mixed with pyrolytic polyacrylonitrile (PAN) to synthesize a composite anode of Si-SnSb/ pyrolytic polyacrylonitrile (PAN) with the pyrolysis of PAN at 400 °C and 600 °C. The material exhibits a high-specific capacity and a good-cycling stability due to its multiphase characteristics. The Si-SnSb blended with PAN pyrolyzed at 600 °C shows better electrochemical performance, its initial Coulombic efficiency is 62.6%, and the specific capacity is 658.4 mAh g⁻¹ after the 10th cycle. The pyrolytic PAN improves the performance of the Si-SnSb alloy by means of dispersing the alloy efficiently, and the pyrolytic PAN enhances the performance of the pure alloy simultaneously.     

CuO/graphene composite as anode materials for lithium-ion batteries

CuO/graphene composite is synthesized from CuO and graphene oxide sheets following reduced by hydrazine vapor. As the electrode material for lithium-ion batteries, CuO nanoparticles with sizes of about 30 nm homogeneously locate on graphene sheets, and act as spacers to effectively prevent the agglomeration of graphene sheets, keeping their high active surface. In turn, the graphene sheets with good electrical conductivity server as a conducting network for fast electron transfer between the active materials and charge collector, as well as buffered spaces to accommodate the volume expansion/contraction during discharge/charge process. The synergetic effect is beneficial for the electrochemical performances of CuO/graphene composite, such as improved initial coulombic efficiency (68.7%) and reversible capacity of 583.5 mAh g⁻¹ with 75.5% retention of the reversible capacity after 50 cycles.     

Three-dimensional MnO/reduced graphite oxide composite films as anode materials for high performance lithium-ion batteries

MnO/reduced graphite oxide (MnO/RGO) composite films with three dimensionally porous structures have been synthesized by an improved electrostatic spray deposition setup and their microstructure and electrochemical properties have been characterized by X-ray diffraction, scanning electron microscopy, thermal gravimetric, Raman spectrometry and galvanostatic cell cycling. The results show that the structure and electrochemical performance of the electrode film are influenced significantly by the RGO content. The three dimensionally porous structure collapse does not occur in the MnO/RGO thin films for a RGO content lower than 16.58 wt%, the 16.58 wt% reduced graphite oxide content being optimal. Such an improvement in the cycling performance (772 mAh g⁻¹ after 100 cycles at 1 C) and rate capability (425 mAh g⁻¹ at 6 C) might be attributed to the excellent microstructure and electrical conductivity of MnO/reduced graphite oxide composite film electrodes.     

锂离子电池硅负极材料粉化问题研究进展

硅作为锂离子电池的负极材料由于其很高的理论比容量（4212 mA·h·g^-1）而备受关注。硅材料的研究集中在解决充放电中体积胀缩所引起的粉化问题。通过调研近年来硅负极材料粉化问题研究进展,对比了各种方法的优劣和思路,在此基础上进行了简单的评述。     

锂离子电池铁氧化物负极材料的研究进展

铁氧化物负极材料具有较高的储锂容量和较低的电压平台,是最具潜力的下一代锂离子电池负极材料之一,而且铁氧化物负极材料具有合成方法简单、对环境友好等特点,受到研究者的关注。本文介绍了铁氧化物负极材料在锂离子电池中的应用以及最新进展情况,总结了铁氧化物材料的不同制备方法,重点分析了不同铁氧化物负极材料在电化学性能方面表现出的差异,展望了铁氧化物负极材料电化学性能的研究趋势。     

Effects of electrolytes on the electrochemical performance of Si/graphite/disordered carbon composite anode for lithium-ion batteries

The influences of LiBF₄, LiClO₄, lithium bis(oxalato) borate (LiBOB), LiPF₆ with VC and without VC, and the mixed electrolytes composed of different ratios of LiBOB and LiPF₆ or LiClO₄ on the electrochemical properties of Si/graphite/disordered carbon (Si/G/DC) composite electrode were systematically investigated by constant current charge-discharge and electrochemical impedance spectra (EIS) techniques. Scanning electron microscopy (SEM) was used to observe the change of electrodes in morphology after given cycle numbers. X-ray photoelectron spectroscopy (XPS) was employed to understand the influences of different mixed electrolytes on the composition of SEI layers. The results showed that Si/G/DC composite electrode in the mixed electrolytes presented better electrochemical performance than in single electrolyte. The compactness and compositions of SEI layers intensively influenced the cycle performance of Si/G/DC composite materials. LiBOB and additive VC had a good synergistic effect on the formation of the dense SEI layers. In particular, Si/G/DC in 0.5 M LiBOB + 0.38 M LiPF₆ electrolytes containing VC exhibited a high reversible capacity and excellent cycle performance.     

Long-term cyclability of LiFePO4/carbon composite cathode material for lithium-ion battery applications

A simple high-energy ball milling combined with spray-drying method has been developed to synthesize LiFePO₄/carbon composite. This material delivers an improved tap density of 1.3 g/cm³ and a high electronic conductivity of 10⁻² to 10⁻³ S/cm. The electrochemical performance, which is especially notable for its high-rate performance, is excellent. The discharge capacities are as high as 109 mAh/g at the current density of 1100 mA/g (about 6.5C rate) and 94 mAh/g at the current density of 1900 mA/g (about 11C rate). At the high current density of 1700 mA/g (10C rate), it exhibits a long-term cyclability, retaining over 92% of its original discharge capacity beyond 2400 cycles. Therefore, the as-prepared LiFePO₄/carbon composite cathode material is capable of such large-scale applications as hybrid and plug-in hybrid electric vehicles.     

高分散SiO2/石油沥青基多孔碳用于锂离子电池负极

二氧化硅(SiO₂)作为锂离子电池负极材料具有理论容量高、放电电位低、成本较低等特点,但存在导电性差、充放电过程体积膨胀严重以及容量衰减过快等问题。以石油沥青为碳源,利用硅烷偶联剂KH-540对纳米α-Fe₂O₃模板剂进行表面化学包覆,然后将硅源修饰模板剂与碳源混合,经碳化、酸洗等步骤得到高分散SiO₂/石油沥青基多孔碳(SiO₂/PC)。所得SiO₂/PC作为锂离子电池负极材料,在1 A·g^-1电流密度下,循环900圈后仍具有640 mA·h·g^-1的高可逆比容量。研究结果表明,高度纳米化的SiO₂在高温碳化过程原位生成,紧密牢固地负载于多孔碳表面,提高了其导电性,同时能够有效缓解SiO₂在充放电过程中的体积膨胀,抑制SiO₂的团聚或粉化,从而表现出优异的电化学性能。     

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.