锂离子电池硅基负极材料嵌锂行为的第一性原理研究

采用基于密度泛函理论的第一性原理平面波赝势方法,计算不同数量的锂离子引起的硅材料晶体结构的变化以及在嵌锂过程中形成Li_xSi(x=1、2、2.4、4.4)合金相的形成能与电子结构.采用LST/QST方法计算过渡态,模拟合金体相中的锂离子迁移过程.计算结果表明,随着嵌锂数量的增加,硅晶胞的体积在不断增大;Li_xSi合金相的形成能为负值,表明在嵌锂过程中锂离子和硅原子可以自发形成这些合金相,其中Li₇Si₃合金最容易形成;随着嵌锂量的增加,锂离子在费米能级处s轨道提供的电子数逐渐增加,锂硅合金在费米能级处的电子数量呈增大趋势,表明锂硅合金的导电性越来越优;常温下Li₂Si体相中很难直接形成锂离子空位,但锂离子空位的迁移过程很容易发生.     

Nanoporous carbon microspheres as anode material for enhanced capacity of lithium ion batteries

Nanoporous carbon microspheres (NCMs) are prepared by a one-step carbonizing and activating resorcinol?formaldehyde polymer spheres (RFs) in inert and CO₂ atmosphere for anode materials of lithium-ion batteries (LIBs). Compared with RFs carbon microspheres (RF-C), after activating with hot CO₂, the NCMs with porous structure and high BET surface area of 2798.8 m² g^?1, which provides abundant lithium-ion storage site as well as stable lithium-ion transport channel. When RF-C and NCM are used to anode material for LIBs, at the same current density of 210 mA g^?1, the initial specific discharge capacity are 482.4 and 2575.992 mA h g^?1, respectively; after 50 cycles, the maintain capacity are 429.379 and 926.654 mA h g^?1, respectively. The porous spherical structure of NCM possesses noticeably lithium-ion storage capability, which exhibits high discharge capacity and excellent cycling stability at different current density. The CO₂ activating carbonaceous materials used in anode materials can tremendously enhance the capacity storage, which provides a promising modification strategy to improve the storage capacity and cyclic stability of carbonaceous anode materials for LIBs.     

锂离子电池Sn-Ti合金负极材料的制备及性能研究

采用磁控溅射沉积技术制备了纳米级Sn-Ti合金负极材料,并用X射线衍射和扫描电子显微镜进行表征,用高精度电池测试系统进行充放电和循环伏安测试.结果表明先镀Sn后镀Ti（Sn/Ti复合膜）和先镀Ti后镀Sn（Ti/Sn复合膜）具有很大的性能差异,其中Sn/Ti复合膜具有优异的循环稳定性和较高的可逆容量.首次放电容量和充电容量分别为9275 mAh/g和6954 mAh/g,首次库仑效率为75％,经30次循环后,该电极的放电容量保持为4152 mAh/g,这主要归因于活性物质Sn与电解液界面之间存在非活 关键词： 锂离子电池 磁控溅射 Sn-Ti合金 电化学性能     

硅功能化石墨烯负极材料的粗粒模型

硅功能化石墨烯(硅化烯)作为锂离子电池的负极材料, 一旦发生分层或粉化等损伤现象, 会严重地降低材料的电子输运能力和储锂容量, 减少电池的使用寿命, 因此要求负极材料具有较强的力学可靠性. 考虑到传统分子动力学方法的模拟尺度很难达到硅化烯负极材料的真实尺度, 首先采用Tersoff 势函数和Lennard-Jones 势函数建立了多种硅化烯的全原子数值模型, 计算材料的各种弹性模量和吸附能; 然后采用珠子-弹簧结构, 根据力学平衡条件和能量守恒定律, 结合全原子模型的计算结果, 建立了硅化烯粗粒模型及其系统的能量方程; 最后, 通过对比石墨烯粗粒模型与其全原子模型的拉伸性能, 验证了硅化烯粗粒模型的有效性.     

Electrochemical performance of modified artificial graphite as anode material for lithium ion batteries

Artificial graphite anode material was modified by coating an amorphous carbon layer on the particle surface via a sol-gel and pyrolysis route. The electrochemical measurements demonstrate that appropriate carbon coating can increase the specific capacity and the initial coulombic efficiency of the graphite material, while excessive carbon coating leads to the decrease in specific capacity. Thick coating layer is obviously unfavorable for the lithium ion diffusion due to the increased diffusion distance, but the decreased specific surface area caused by carbon coating is beneficial to the decrease of initial irreversible capacity loss. The sample coated with 5 wt.% glucose exhibits a stable specific capacity of 340 mAhg^?1. Carbon coating can remarkably enhance the rate capability of the graphite anode material, which is mainly attributed to the increased diffusion coefficient of lithium ion.     

Influence of post-calcination treatment on the spinel lithium titanium oxide anode material for lithium ion batteries

The influence of post-calcination treatment on spinel Li₄Ti₅O₁₂ anode material is extensively studied combining with a ball-milling-assisted rheological phase reaction method. The post-calcinated Li₄Ti₅O₁₂ shows a well distribution with expanded gaps between particles, which are beneficial for lithium ion mobility. Electrochemical results exhibit that the post-calcinated Li₄Ti₅O₁₂ delivers an improved specific capacity and rate capability. A high discharge capacity of 172.9 mAh g^?1 and a reversible charge capacity of 171.1 mAh g^?1 can be achieved at 1 C rate, which are very close to its theoretical capacity (175 mAh g^?1). Even at the rate of 20 C, the post-calcinated Li₄Ti₅O₁₂ still delivers a quite high charge capacity of 124.5 mAh g^?1 after 50 cycles, which is much improved over that (43.9 mAh g^?1) of the pure Li₄Ti₅O₁₂ without post-calcination treatment. This excellent electrochemical performance should be ascribed to the post-calcination process, which can greatly improve the lithium ion diffusion coefficient and further enhance the electrochemical kinetics significantly.     

Metal oxide-embedded porous carbon nanoparticles as high-performance anode materials for lithium ion batteries

Conjugated microporous polymer (CMP) was used as a precursor to fabricate porous carbon nanoparticles (PCNs) embedded with different metal oxides (NiO_x, CoO_x, and MnO_x). Rate performance tests indicate that 10% MnO_x embedded PCNs (MnO_x10-PCN) show superior rate performance over PCN. MnO_x10-PCN and PCN were further investigated by XRD, XPS, TG, SEM, TEM, FT-IR, BET, cyclic voltammetry, and galvanostatic discharge–charge test. XRD and XPS results reveal that MnO and MnO₂ phase co-exist in the MnO_x10-PCN. SEM results indicate that both MnO_x10-PCN and PCN are spherical particles with a size ranging from 20 to 50 nm. TEM results imply that MnO_x nanoparticles are incorporated inside some porous carbon nanoparticles. FT-IR results indicate some residuary benzene rings remain in the MnO_x10-PCN and PCN. BET analysis reveals that pore properties of MnO_x10-PCN are very near to that of CMP. These unique features ensure MnO_x10-PCN possesses high reversible capacity, excellent rate performance, and long cycling life. MnO_x10-PCN delivers an initial reversible capacity of 986 mAh g^?1 at 0.2 C. In addition, the capacity cycled at 2 C for 700 cycles is even higher than its original capacity.     

Distinctive slit-shaped porous carbon encapsulating phosphorus as a promising anode material for lithium batteries

A distinctive structure of carbon materials for Li-ion batteries is proposed for the preparation of red phosphorus-carbon composites. The slit-shaped porous carbon is observed with aggregation of plate-like particles, whose isotherm belongs to the H3 of type IV. The density functional theory (DFT) method reveals the presence of micro-mesopores in the 0.5–5 nm size range. The unique size distribution plays an important role in adsorbing phosphorus and electrochemical performance. The phosphorus-slit-shaped porous carbon composite shows initial capacity of 2588 mAh g^?1, reversible capacity of 1359 mAh g^?1 at a current density of 100 mA g^?1. It shows an excellent coulombic efficiency of ～99 % after 50 cycles.     

Investigation of N-doped carbon-coated lithium zinc titanate using chitin as a carbon source for lithium-ion batteries

Nitrogen-doped carbon-coated Li₂ZnTi₃O₈ (NC-LZTO) anode material was fabricated with chitin as a carbon source by precoating process via a facile solid-state reaction method. The effects of nitrogen-doped carbon layer on the crystal structure, surface morphology, and electrochemical performances were studied. The NC-LZTO samples show the significant improvement in rate capability compared with carbon-coated Li₂ZnTi₃O₈ (C-LZTO) sample derived from glucose and naked Li₂ZnTi₃O₈ (LZTO) sample. At the current rates of 0.5, 1, 2, 5, and 10 C, the discharge-specific capacities of the NC-LZTO sample are 275.6, 262.8, 244.8, 217, and 190.6 mAh g^?1, respectively. After 200 cycles at 2 C, its capacity retention is 98.7%. The increased electrochemical performance of NC-LZTO can be ascribed to the larger specific surface, smaller particle size, and better electronic conductivity.     

Effect of carbon nanotubes on the anode performance of natural graphite for lithium ion batteries

A comparative investigation was carried out on carbon black and multiwalled carbon nanotubes as conductive additives in spherical natural graphite for lithium ion batteries. Scanning electron microscopy images showed that carbon nanotubes interlaced graphite particles in series to form a three-dimensional network. The constant current charge-discharge experiments showed that carbon nanotubes were more effective in improving reversible capacity and cycle stability. The reversible capacity was improved to 366 mAh/g and the cycle stability was improved effectively when carbon nanotubes were used. The research is of potential interest to the application of carbon nanotubes as conductive additives in anode materials for high-power lithium ion batteries.     

Performance of developed natural vein graphite as the anode material of rechargeable lithium ion batteries

Electrochemical performance of natural vein graphite as an anode material for the rechargeable Li-ion battery (LIB) was investigated in this study. Natural graphite exhibits many favorable characteristics such as, high reversible capacity, appropriate potential profile, and comparatively low cost, to be an anode material for the LIB. Among the natural graphite varieties, the vein graphite typically possesses very high crystallinity together with extensively high natural purity, which in turn reduces the cost for purification. The developed natural vein graphite variety used for this study, possessed extra high purity with modified surface characteristics. Half-cell testing was carried out using CR 2032 coin cells with natural vein graphite as the active material and 1 M LiPF₆ (EC: DMC; vol. 1:1) as the electrolyte. Galvanostatic charge–discharge, cyclic voltammetry, and impedance analysis revealed a high and stable reversible capacity of 378 mA h g^?1, which is higher than the theoretical capacity (372 mA h g^?1 for LiC₆). Further, the observed low irreversible capacity acquiesces to the high columbic efficiency of over 99.9%. Therefore, this highly crystalline developed natural vein graphite can be presented as a readily usable low-cost anode material for Li-ion rechargeable batteries.     

锂离子电池负极材料CuSn的Li嵌入性质的研究

使用基于混合基表示的第一原理赝势法，研究了锂离子电池非碳类负极材料CuSn的Li嵌入时的形成能以及相应的电子结构.还给出了Li嵌入时的体积变化，能带结构、电子态密度以及电荷密度分布等性质, 并讨论了CuSn作为负极材料的特点.计算发现，Cu-Sn化合物在闪锌矿结构时，Li嵌入主体材料时的嵌入形成能大致在3.5eV附近. 关键词： 锂离子电池 负极材料 CuSn 电子结构     

Enhancement of the electrochemical performance of silicon/carbon composite material for lithium ion batteries

The silicon/carbon (Si/C) composite material was prepared, and the electrochemical performance was investigated as a promising anode material for lithium ion batteries. The results show that the binder in the electrode acts as an important role for improving the reversible capacity of the Si/C materials during cycling. The Si/C electrode with CMC/SBR binder possesses a better cycle performance than that with PVDF binder. The Si/C composite material shows an initial reversible capacity of more than 700 mAh∙g⁻¹ and remains a reversible capacity of 597 mAh g⁻¹ after 40 cycles.     

The influence of polytetrafluorethylene reduction on the capacity loss of the carbon anode for lithium ion batteries

To date, the lithium ion battery has become the focus of secondary battery studies. A considerable capacity loss during the first lithiation of its carbon electrode is a severe drawback of this kind of battery. It has been suggested frequently that the capacity loss was caused by the decomposition of the electrolyte on the surface of the carbon electrode. However, the contribution of binder reduction to this capacity loss has never been considered until now. This paper deals with the binder polytetrafluorethylene (PTFE) reduction and finds that it plays an important part in the capacity loss. It is found that (1) the capacity loss increased with increasing PTFE binder content, (2) the X-ray diffraction peaks corresponding to the PTFE, binder became weaker, while more of the lithium was consumed by the carbon electrode, and disappeared when the consumed amount of lithium exceeded the theoretical value of 1070 mAh per gram of PTFE and (3) the height of the high voltage plateau of the electrochemical titration curves was just a function of storage time, and the length of the plateau was a function of the PTFE content.     

Electrochemical properties of metal oxides as anode materials for lithium ion batteries

Some oxides have been investigated as alternative materials for Li-ion batteries. In particular, the In₂O₃ anodic compound, synthesized in our laboratory, and some commercial powders (PbO, PbO₂ and Fe₂O₃) were studied. The morphology of the oxides was analyzed by SEM investigation. The electrochemical characteristics obtained on composite thin-film electrodes based on these materials are here reported, in term of specific capacity and cyclability. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Preparation and characterization of spherical La-doped Li4Ti5O12 anode material for lithium ion batteries

The lithium secondary batteries with high power density need the electrode materials with both high specific capacity and high tap density. An “outer gel” method by TiCl₄ as the raw material has been developed to prepare spherical precursor. High tap density spherical Li₄Ti₅O₁₂ is synthesized by sintering the mixture of precursor and Li₂CO₃. La-doped Li₄Ti₅O₁₂ is also prepared by this method. X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, tap density testing, and the determination of the electrochemical properties show that the Li₄Ti₅O₁₂ powders prepared by this method are spherical and exhibits high tap density. La³⁺ dopant improved the electrochemical performance over the pristine Li₄Ti₅O₁₂. It is tested that the tap density of the pristine and La³⁺-doped products is as high as 1.80 and 1.78 g•cm⁻³, respectively. Between 1.0 and 3.0 V versus Li, the initial discharge capacity of the La³⁺ dopant is as high as 161.5 mAh•g⁻¹ at 0.1C rate. After 50 cycles, the reversible capacity is still 135.4 mAh•g⁻¹.     

Development and characterization of a novel silicon-based glassy composite as an anode material for Li-ion batteries

A novel silicon-based glassy composite anode material with high initial coulombic efficiency and long cycling performance for lithium-ion batteries was synthesized by a wet mechanochemical reduction method. The in situ formed Si particles with size of 5-10 nm were uniformly distributed in the glassy matrices formed by B₂O₃ and P₂O₅. The as-prepared composite electrode revealed an initial charge and discharge capacity of 432.7 and 514.4 mAh g^− 1, respectively, with an initial coulombic efficiency of 84%. After 100 cycles, the reversible capacity retention rate was still up to 97%, meaning a favorable cycling stability.     

Synthesis and electrochemical properties of SnS as possible anode material for lithium batteries

Tin monosulfide, SnS particles were synthesized at 950 °C using a simple melt mixing. The as prepared materials were subjected to XRD, SEM and EDAX analyses. The CR 2032-type coin cell composed of Li/SnS was assembled and its cycling profile was examined. The cell delivered an initial discharge capacity of 956 mAh/g at its first cycle and fades subsequently in the following cycles. The formation of Li₂CO₃ in the solid electrolyte interface (SEI) was identified by FT-IR analysis. Impedance spectroscopic study on Li/SnS cells revealed an increase in the value of charge transfer resistance “R_ct” upon cycling and is attributed to the breaking of inter-particle contact caused by the volume expansion.     

Pyrolytic carbon derived from coffee shells as anode materials for lithium batteries

Disordered carbonaceous materials have been obtained by pyrolysis of coffee shells at 800 and 900 °C with pore-forming substances such as KOH and ZnCl₂. X-ray diffraction studies revealed a carbon structure with a large number of disorganized single layer carbon sheets. The structure and morphology of the materials have been greatly varied upon the addition of porogens. The prepared carbon materials have been subjected to cycling studies. The KOH-treated products offered higher capacity with improved stability than those with untreated and ZnCl₂-treated one.     

Synthesis of N-doped graphene/SnS composite and its electrochemical properties for lithium ion batteries

N-doped graphene/SnS composite as high-performance anode materials has been synthesized by a simultaneous solvothermal method using ethylene glycol as solvent. The morphology, structure, and electrochemical performance of N-doped graphene/SnS composite were investigated by transmission electron microscope (TEM), X-ray diffraction (XRD), Raman spectra, Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The SnS nanoparticles with sizes of 3–5 nm uniformly distribute on the N-doped graphene matrix. The N-doped graphene/SnS composite exhibits a relatively high reversible capacity and good cycling stability as anode materials for lithium ion batteries. The good electrochemical performance can be due to that the N-doped graphene as electron conductor improves the electronic conductivity of composite and elastic matrix accommodates the large volume changes of SnS during the cycles.