碳纳米管和石墨烯在锂离子电池硅负极中的应用

碳纳米管、石墨烯与具有高理论比容量的硅材料形成的复合负极材料,可以提高硅负极的导电性和稳定性,是目前极具发展前景的锂离子电池负极材料。本文综述了碳纳米管和石墨烯在锂离子电池硅负极材料中应用的研究进展,并对未来的应用前景作了展望。     

锂离子电池用高容量复合负极材料的研究进展

硅基复合材料因具有较高储锂特性而成为锂离子电池用高容量负极材料的首选。本文介绍目前常见的3类硅基复合负极材料:包覆型硅基负极材料、硅/炭复合负极材料、氧化亚硅复合负极材料。简述这几类材料各自的优势和区别,最后对硅基材料所面临的现状进行分析,提出其未来的发展方向。     

锂离子电池硅/碳复合负极材料的研究进展

负极材料是制约锂离子电池发展的重要因素之一.硅/碳复合材料储锂容量高、循环稳定性好,是目前制备新型锂离子电池负极材料的研究热点.介绍了硅/碳复合材料的不同制备方法和复合结构以及优良的电化学性能,综述了硅/碳复合材料的研究进展,并对未来的发展方向进行了展望.     

Si基锂离子电池负极材料研究进展

硅具有高的理论比容量、较低的嵌锂电位、来源广泛且环境友好等优点,被认为是下一代锂离子电池负极材料的有力竞争者。然而,在锂离子脱嵌过程中巨大的体积膨胀引起了活性材料的粉化和破裂,这带来了电极循环性能差、容量衰减快甚至电极失效等一系列问题。迄今为止,有大量关于改性硅基材料的报道。本文将重点介绍硅基材料的纳米结构化设计和硅/碳材料的结合。首先,分析了硅的储锂及失效机制,从机理上理解硅的失效对其电化学性能的影响。其次,从理论上阐述了纳米级硅材料对缓解体积效应的机理,从结构设计、材料合成、形态特征和电化学性能等方面论证了纳米硅材料的优势。随后,从缓解体积膨胀、提高电导率和形成稳定的固体电解质（SEI）膜等方面总结了硅碳复合材料的研究进展。此外,还讨论了将导电聚合物和金属引入硅基材料的电化学性能增强机理。最后,从提高首次库仑效率、SEI膜稳定性和质量负载量等方面对硅基材料的产业化应用提出几点建议。     

二维硅烯纳米片作为锂离子电池负极材料研究进展

硅材料被公认为最具有商业化前景的高容量锂离子电池负极之一,但其锂化膨胀率过高的问题成为阻碍应用的瓶颈.基于层状结构和特殊价键形式的新型二维材料—硅烯成为负极材料理想的硅源,为从根本上破解锂离子电池能量密度偏低的难题提供新途径.本文综述了硅烯纳米片作为锂离子电池负极的研究进展,分别就硅烯纳米片的特性、硅烯纳米片的制备工艺...     

优质石油焦用于锂离子电池负极的研究进展

总结了优质石油焦(以针状石油焦为主)在锂离子电池负极材料方面的研究进展,包括:优质石油焦的处理温度对其结构和电化学性能的影响;优质石油焦的微结构及其储锂机理;优质石油焦作为软碳应用于负极材料情况。最后,对适用于锂离子电池负极材料的优质石油焦结构特点进行小结,并探讨石油焦类锂离子电池负极材料的发展趋势。     

碳纳米管在锂离子电池中的应用

如今随着新型电极材料研究的不断加深,该材料在高性能的锂离子电池应用中发挥着巨大作用。因此硅材料由于其独特的性能成为了电极材料的首选,其具备了较高的储锂容量以及较低的储锂地位。但是由于硅在充放电时体积会发生变化,给锂电池的稳定性会造成一定的影响。基于此本文研究分析了具有可控性结构的碳纳米管硅分子复合型材料,因其具有比较优异的综合性能,在新型的锂离子电池中获得较好的应用,解决了锂离子电池的稳定性,为我国锂离子电池的发展起到了很好地促进作用。     

锂离子电池负极用碳/硅复合材料的研究进展

硅(Si)因具有资源丰富、理论容量高、绿色环保等优点成为世界上最具有前景的锂离子电池负极材料之一。但硅的导电性能差,且在合金化/去合金化过程中会发生剧烈的体积膨胀导致电池循环稳定性严重下降。碳材料(C)导电性能优异且结构稳定。将C和Si进行复合,可得到容量高且循环性能好的锂离子电池负极材料。本综述从材料的制备方法着手,总结了锂离子电池C/Si复合负极材料的最新研究进展,探讨了制备方法、材料结构对C/Si复合负极材料储锂性能的影响。     

锂离子二次电池炭负极材料的插锂机理

综述了有关锂离子二次电池炭负极材料插锂行为的报道,由于各种炭负极材料的结构性能不同,表现在插锂行为上存在很大差异。这些插锂机理主要有:经典的石墨层间插入式化合物的插锂机理、多层锂机理、层—边端—表面储锂机理、碳—锂—氢机理、微孔储锂机理、锂分子Li_2的形成机理及其他插锂机理。     

简讯

日本一家公司最近开发出锂离子电池制造新技术,利用硅氧化物、纳米硅、碳等生成的新型材料制作电池负极,使电池容量比目前使用石墨作负极的锂离子电池增加2至5成。硅具有价格低廉且对锂离子的吸收率高等特点,适合制造大容量电池。但是,硅吸收锂离子时的膨胀率也很高,用作电池负极易产生裂缝,进而缩短电池寿命。因此,硅材料制成的锂离子电池负极一直没能实用化。据《日经产业新闻》日前报道,日立万胜公司采用新技术,让纳米硅散布于硅氧化物材料内部形成“含纳米硅化合物,再混合这种“含纳米硅化合物和碳材料,形成“纳米硅多孔质复合材料。这…     

Lithium containing silazanes as precursors for SiCN:Li ceramics—A potential material for electrochemical applications

Lithium containing silicon carbonitride ceramics (SiCN:Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of the model compound 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane and of a commercial poly(organosilazane) VL20^® with n-butyllithium in different molar ratios. According to Raman spectroscopic measurements, lithiation takes place at the NH groups of the molecular organosilazane structure. If the amount of n-BuLi exceeds the stoichiometric amount of NH groups, addition of n-BuLi at the vinyl groups (attached as substituents at the Si atoms of the silazane) occurs. Thermal analysis coupled with in situ mass spectrometry evidenced the loss of methane and hydrogen as the main gaseous by-products formed during the precursor-to-ceramic-transformation. The ceramization process is completed at 1100 °C in argon and yielded Li-containing silicon carbonitride, SiCN:Li. X-ray powder diffraction revealed that the resulting SiCN:Li ceramics were basically amorphous and contained LiSi₂N₃ as a crystalline phase with increasing amount of Li. Possible applications of the new SiCN:Li ceramics are seen in the field of Li-ion batteries as alternative anode or solid electrolyte material.     

Molecular orbital calculations on electronic and Li-adsorption properties of sulfur-, phosphorus- and silicon-substituted disordered carbons

To clarify the effect of atom substitution on electronic and lithium (Li) adsorption properties of disordered carbons, we employed circum-coronene (C₅₄H₁₈) as a model cluster for disordered carbons and investigated the stable structures, electronic and Li-adsorption properties of its sulfur-, phosphorus- and silicon-substituted sheets, by using a semiempirical molecular orbital method. Among the three substituted sheets, the silicon-substituted Si₂C₅₂H₁₈ sheet was found to have desirable properties as an anode material of rechargeable Li-ion batteries: planar structure and large amount of Li adsorption. Although the Li-adsorption energy of Si₂C₅₂H₁₈ is smaller than that of B₂C₅₂H₁₈, the dependence of adsorption energy on the number of Li atoms indicates that Si₂C₅₂H₁₈ can adsorb more Li atoms than B₂C₅₂H₁₈. Therefore, silicon- as well as boron-substituted disordered carbons are expected to be promising materials for the anode in Li-ion batteries.     

Identification of nano-sized holes by TEM in the graphene layer of graphite and the high rate discharge capability of Li-ion battery anodes

SEM images of round-shaped natural graphite, currently widely used as the anode active material of Li-ion batteries, show that the surface mainly consists of the basal plane, which suggests that the Li insertion/extraction reaction rate is quite limited. In contrast to this suggestion, however, the anode of commercial Li-ion batteries is capable of high rate charging/discharging. In order to explain this inconsistency, we propose that there are nano-holes in the graphene layers of the graphite allowing Li to be very easily inserted and extracted via the holes.Prior to the measurements a quantum chemical investigation was performed on the energy required for Li to pass through the hole in a graphene layer (E_act). The results showed that the E_act value is too high when the size is smaller than pyrene, but is fairly low for holes of the size of coronene, implying that Li can pass through the basal plane layer if there is a hole larger than coronene.Characterization of the rounded graphite sample and flaky natural graphite was conducted by constant-current charge/discharge cycle tests, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). XRD revealed no appreciable difference between the rounded graphite and flaky natural graphite, in agreement with Raman data.A detailed analysis of the HRTEM results revealed the presence of a number of variously sized circular images. We believe that these are holes in the graphene layer through which Li can pass. The mechanism of formation of the holes is discussed.     

In situ X-ray absorption spectroscopy of germanium evaporated thin film electrodes

The understanding of germanium Li-ion insertion/extraction reaction mechanism is drawing more and more attention in the field of Li-ion batteries. When a germanium thin film electrode is inserted with Li ions, the material remains amorphous until it crystallizes into Li₁₅Ge₄ as evidenced by X-ray diffraction. The local coordination environment of the Ge atoms of the intermediate amorphous phases was investigated by in situ X-ray absorption spectroscopy. Li-ion insertion and extraction were electrochemically controlled by continuous and intermittent galvanostatic methods. The evolution of the coordination number and interatomic distance of Ge–Ge and Ge–Li shells was determined as a function of Li composition. From a short range ordering perspective, it was observed that the first Ge–Ge interatomic distance increases and the Ge–Ge coordination number decreases with increasing Li content. The opposite is observed for the first Li–Ge interaction. Moreover, it was found that electrochemical lithiation is reversible at the atomic scale.     

Graphene as a conductive additive to enhance the high-rate capabilities of electrospun Li4Ti5O12 for lithium-ion batteries

Spinel Li₄Ti₅O₁₂ (LTO) is a promising candidate anode material for Li-ion batteries due to its well-known zero-strain merits. To improve the electronic properties of spinel LTO, which are intrinsically poor, we processed the material into a nanosized architecture to shorten the distance for Li-ion and electron transport using the versatile electrospinning method. Graphene was chosen as an effective carbon coating to improve the surface conductivity of the nanocomposites. The as-prepared graphene-embedded LTO anode material showed improved discharging/charging and cycling properties, particularly at high rates, such as 22 C, which makes the nanocomposite an attractive anode material for applications in electric vehicles.     

Fe2O3/N-doped carbon-modified SiOx particles via ionic liquid as anode materials for Li-ion batteries

Journal of Applied Electrochemistry - SiOx is considered a promising alternative anode material for Li-ion batteries because of its higher theoretical capacity and safety compared with those of...     

Vertically ordered Ni(3)Si(2)/Si nanorod arrays as anode materials for high-performance Li-ion batteries

In this paper, we have reported a novel hierarchical nanostructure made of vertically ordered Ni(3)Si(2)/Si nanorod arrays to moderate the notorious pulverization and capacity decay usually occurring in the silicon used as the anode materials in Li-ion batteries. During the lithiation and delithiation process, the amorphous Si (a-Si) layer acts as an active material and participates in the processes, whereas the Ni(3)Si(2) nanorod arrays work as a mechanically stable supporter and fast charge transport pathway. In addition, they can afford sufficient interspace for expansion/contraction upon lithium insertion/extraction. These Ni(3)Si(2)/Si nanorod arrays anodes exhibit excellent cycling performance at high current rates of 1 C (4.2 A g(-1)), 2 C (8.4 A g(-1)), and 4 C (16.8 A g(-1)), respectively. A high and steady discharge capacity of over 2184 mA h g(-1) can be achieved after 50 cycles with a high initial coulombic efficiency of 86.7%. The synthesis approach is simple, efficient and rich-yielding, probably providing a new strategy for the application of silicon-based anode materials with enhanced performance.     

Li ion battery materials with core-shell nanostructures

Nanomaterials have some disadvantages in application as Li ion battery materials, such as low density, poor electronic conductivity and high risk of surface side reactions. In recent years, materials with core-shell nanostructures, which was initially a common concept in semiconductors, have been introduced to the field of Li ion batteries in order to overcome the disadvantages of nanomaterials, and increase their general performances in Li ion batteries. Many efforts have been made to exploit core-shell Li ion battery materials, including cathode materials, such as lithium transition metal oxides with varied core and shell compositions, and lithium transition metal phosphates with carbon shells; and anode materials, such as metals, alloys, Si and transition metal oxides with carbon shells. More recently, graphene has also been proposed as a shell material. All these core-shell nanostructured materials presented enhanced electrochemical capacity and cyclic stability. In this review, we summarize the preparation, electrochemical performances, and structural stability of core-shell nanostructured materials for lithium ion batteries, and we also discuss the problems and prospects of this kind of materials.     

Embedded Si/Graphene Composite Fabricated by Magnesium-Thermal Reduction as Anode Material for Lithium-Ion Batteries

Embedded Si/graphene composite was fabricated by a novel method, which was in situ generated SiO₂ particles on graphene sheets followed by magnesium-thermal reduction. The tetraethyl orthosilicate (TEOS) and flake graphite was used as original materials. On the one hand, the unique structure of as-obtained composite accommodated the large volume change to some extent. Simultaneously, it enhanced electronic conductivity during Li-ion insertion/extraction. The MR-Si/G composite is used as the anode material for lithium ion batteries, which shows high reversible capacity and ascendant cycling stability reach to 950 mAh·g^?1 at a current density of 50 mA·g^?1 after 60 cycles. These may be conducive to the further advancement of Si-based composite anode design.     

Hollow Nanostructured Anode Materials for Li-Ion Batteries

Hollow nanostructured anode materials lie at the heart of research relating to Li-ion batteries, which require high capacity, high rate capability, and high safety. The higher capacity and higher rate capability for hollow nanostructured anode materials than that for the bulk counterparts can be attributed to their higher surface area, shorter path length for Li⁺ transport, and more freedom for volume change, which can reduce the overpotential and allow better reaction kinetics at the electrode surface. In this article, we review recent research activities on hollow nanostructured anode materials for Li-ion batteries, including carbon materials, metals, metal oxides, and their hybrid materials. The major goal of this review is to highlight some recent progresses in using these hollow nanomaterials as anode materials to develop Li-ion batteries with high capacity, high rate capability, and excellent cycling stability.