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.     

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.     

Sn-Co-artificial graphite composite as anode material for rechargeable lithium batteries

Nanosized Sn-Co prepared by ultrasonic-assisted chemical reduction is milled with artificial graphite (AG) to form Sn-Co-AG composite. The as-prepared materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrometry and Brunauer-Emmett-Telle (BET) surface area measurement. XRD patterns show that Sn-Co particles are poorly crystallized and artificial graphite has a typical hexagonal graphite structure phase. The diffraction peaks of Sn-Co particles remain the same but some of AG obviously change after milling Sn-Co with AG. BET areas of AG, Sn-Co and Sn-Co-AG are 1.569, 13.187 and 6.754 m² g⁻¹, respectively. SEM images display the as-prepared Sn-Co particles have a size distribution ranging from 20 to 70 nm in diameter. After milling Sn-Co with AG, Sn-Co particles keep similar morphology but there is a perceptible change in AG. Electrochemical tests show that Sn-Co-AG composite possesses much improved electrochemical performance than the state-of-the-art graphite. This composite has great potential as an alternative material for improving the energy density of a lithium ion secondary battery.     

SnO2-C复合负极材料的维度设计用于锂、钠离子电池

新能源汽车的高速发展,对电池材料的能量密度提出了更高的要求。SnO₂-C复合材料因比容量高、倍率性能好、资源丰富、价格低廉等优点而被视为下一代锂、钠离子电池最有潜力的负极材料之一。基于SnO₂-C复合材料的尺寸变化和尺寸复合方式,本文对SnO₂-C复合材料进行了分类,并且详细综述了SnO₂-C复合材料的最新代表性进展,重点涉及尺寸设计公式以及由此产生的协同效应和提高性能的潜力。最后,讨论了该领域未来的发展方向和前景,鉴于协同效应的优良体现,以后该研究将偏于多重复合方向,同时会探索出简单、环保、廉价的合成工艺,不断向商品化的方向靠近。其概念和策略对实际锂离子、钠离子电池金属氧化物-C复合材料的合理设计和可扩展构造提供了一些依据。     

锂二次电池正极材料用四氧化三锰的制备研究

在75℃,pH值为6.5下,以一水硫酸锰为原料,采用空气直接氧化法,当控制Mn2+浓度为60～70 g/L,调节适当的空气流量和搅拌速度,反应12 h,即可制备得到符合锂二次电池正极材料用的四氧化三锰,产物为类球形貌,晶形完整,该Mn3O4振实密度大于1.85 g/m3,Mn含量高于70.5%,S含量低于0.15%,主要金属杂质含量均在30×10-6以下,中位粒径在6～14μm范围内。     

Electrochemical properties of heat-treated polymer-derived SiCN anode for lithium ion batteries

Silicon-carbon-nitrogen material (SiCN) is pyrolyzed from polysilylethylenediamine (PSEDA) derivation, followed by a heat-treating process at 1000 °C in Ar atmosphere. This heat-treated SiCN material has an excellent electrochemical performance as an anode for lithium ion batteries. Charge-discharge cycle measurements show that the heat-treated SiCN material exhibits a high first cycle discharge capacity of 829.0 mAh g⁻¹ and stays between 400 and 370 mAh g⁻¹ after 30 cycles. The discharge capacity remains above 300 mAh g⁻¹ at the high current density of 80 and 160 mA g⁻¹. These values are higher than untreated SiCN and commercial graphite anodes, which indicates that the heat-treating process improves the charge-discharge capacity, cycle stability and high-rate ability of SiCN anode. It is seemed that changes of SiCN structure, the formation of loose nano-holes on material surface and the formation of graphitic carbon phase in heat-treating process contribute to the improvement of electrochemical properties for SiCN anode.     

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.     

Efficient construction of a CoCO3/graphene composite anode material for lithium-ion batteries by stirring solvothermal reaction

Transition-metal carbonates have recently been investigated as anode materials for lithium-ion batteries because of their relatively high capacity compared with that of the corresponding transition-metal oxides. In this work, a facile stirring solvothermal reaction is used to prepare a CoCO₃/graphene composite without the use of an additional organic chelating agent. The as-prepared CoCO₃/graphene composite exhibits a smaller cubic particle size of 1–2 µm and a larger specific surface area than the composite obtained by a traditional solvothermal reaction. The composite prepared with stirring delivers a highly reversible capacity of 602 mAh g^?1 after 100 cycles. Even at a high current density of 2.0 A g^?1, the composite maintains charge–discharge capacities of 605/598 mAh g^?1. The composites contained the same amount of graphene, indicating that the improved electrochemical properties are attained independently of the amount of the graphene. In addition, the results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS)experiments also reveal that the CoCO₃/graphene composite electrode materials synthesised via a stirring solvothermal reaction exhibit substantially enhanced kinetics. The stirring solvo/hydrothermal reaction develops in this work is considered a promising candidate for efficiently preparing carbonate/graphene composites with better electrochemical properties for practical applications, without the use of an extra chelating agent.     

石墨烯/硅负极材料的制备及其电化学性能的研究

通过将亚微米硅与石墨烯进行原位还原复合(SG1)和机械混合(SG2)这2种方式制备了不同的石墨烯/硅复合锂离子电池负极材料。SEM结果显示,2种复合物中硅颗粒都被石墨烯片层所包夹,且分散均匀;充放电测试表明,这2种复合方式均使复合电极的首次容量损失大大减小,循环稳定性得到很大提高,其首次放电比容量分别为2 070.5mAh/g和1 534.2mAh/g,循环12次后均保持在1 000mAh/g以上;通过EIS阻抗谱对硅复合电极的导电性以及电极结构的初步研究,发现复合电极本身导电性以及材料的电接触性远优于纯硅,电极结构也相对稳定。     

中间相炭微球在锂离子电池负极材料的应用进展

中间相炭微球(MCMB)具有良好锂离子扩散性、导电性和机械稳定性等优势,是目前应用广泛、综合性能优异的锂离子电池负极材料,但较低理论比容量是制约其发展的关键因素。为了获得性能优良的MCMB基锂离子电池负极材料,改性修饰和复合材料已然成为目前研发重点。笔者论述了碳结构、表界面和复合材料等微观结构设计对MCMB负极材料电化学性能的影响。从碳堆积结构类型、有序性、层间距以及球体粒径大小等方面,论述了碳结构微观设计对MCMB电化学性能的影响。发现具有乱层结构的MCMB在充放电过程中内部产生应力较小,且碳结构较稳定,具有优异循环稳定性;内部具有大量微孔或碳层间距较大的MCMB,在充放电过程中可提高锂离子在电极中的迁移速率,并提供更多的储锂空间,一般具有优良的充放电比容量和倍率性能;小粒径MCMB具有较短的锂离子迁移路径和随之增加的比表面积,通常具有较好倍率性能,伴随着可逆比容量和充放电效率的衰减。从表界面碳层改性、包覆和掺杂改性等方面,论述了表界面改性对MCMB电化学性能的影响。表面碳层修饰可增加MCMB与电解液的相容性及其比表面积,提高了与电解液的接触面积及贮锂容量,改善了锂离子电池负极材料的电化学性能;另外,MCMB表面包覆一层无定型碳,可避免其表面与电解液直接接触,减少电化学副反应的产生,提升其可逆比容量。从碳活性物质复合材料、非碳活性物质复合材料等方面,论述了复合材料微观结构设计对MCMB电化学性能的影响。碳活性物质可降低MCMB内部碳层结构的有序性,减少锂离子嵌入过程中的内部应力,提升MCMB循环稳定性。非碳活性物质诱导MCMB生成更加有序的碳层结构,提高MCMB的比表面积,从而改善MCMB表面与电解液分子的接触能力及其嵌锂性能,有利于提升MCMB负极材料可逆比容量、循环性能和倍率性能。MCMB具有高碳层间距和多缺陷位点等结构特征,有利于钠离子自由脱嵌,应用于钠离子电池时具有良好的可逆比容量、循环稳定性和倍率性能。MCMB的不规则定向层状结构经活化等处理具有较高比表面积,可应用于超级电容器电极材料。最后提出在高性能锂离子电池电极材料快速发展的需求下,从微观结构角度设计MCMB纳米复合材料将是MCMB负极材料的研究重点。     

One-step synthesis of recoverable CuCo2S4 anode material for high-performance Li-ion batteries

A facile one-step hydrothermal method has been adopted to directly synthesize the CuCo₂S₄ material on the surface of Ni foam. Due to the relatively large specific surface area and wide pore size distribution, the CuCo₂S₄ material not only effectively increases the reactive area, but also accommodates more side reaction products to avoid the difficulty of mass transfer. When evaluated as anode for Li-ion batteries, the CuCo₂S₄ material exhibits excellent electrochemical performance including high discharge capacity, outstanding cyclic stability and good rate performance. At the current density of 200 mA·g⁻¹, the CuCo₂S₄ material shows an extremely high initial discharge capacity of 2510 mAh·g⁻¹, and the cycle numbers of the material even reach 83 times when the discharge capacity is reduced to 500 mAh·g⁻¹. Furthermore, the discharge capacity can reach 269 mAh·g⁻¹ at a current of 2000 mA·g⁻¹. More importantly, when the current density comes back to 200 mA·g⁻¹, the discharge capacity could be recovered to 1436 mAh·g⁻¹, suggesting an excellent capacity recovery characteristics.     

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。     

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.     

Electrochemical properties of Si/Ni alloy–graphite composite as an anode material for Li-ion batteries

Si/Ni alloy and graphite composites were synthesized using arc-melting followed by high energy mechanical milling (HEMM). Alloy particles comprising of NiSi₂, NiSi and Si phases were distributed finely and uniformly on the surface of graphite in the composites obtained after HEMM. The composite containing 60 wt.% of Si/Ni alloy exhibited a stable capacity of 780 mAh/g. Fourier transform infrared spectroscopy (FTIR) analysis confirmed that some bonds were formed between alloy and graphite after HEMM, which appeared to retain the electrical connection between alloy and graphite during cycling. X-ray diffraction (XRD) analysis indicated that NiSi₂ and NiSi phases, which acted as an inactive alloy matrix remained invariant during charge and discharge. In addition to NiSi₂ and NiSi phases, disordered graphite layers also played the role of media for the accommodation of large volume change of Si during cycling. The large reversible capacity and good cycleability showed that Si/Ni alloy and graphite composite could be an alternative to conventional graphite-based anode materials for lithium-ion secondary batteries.     

Cobalt ferrite thin films as anode material for lithium ion batteries

Spinel cobalt ferrite (CoFe₂O₄) thin films have been fabricated by 355 nm reactive pulsed laser deposition on stainless steel substrates. XRD and SEM analyses showed that the CoFe₂O₄ films exhibited a polycrystalline structure and were composed of nanoparticles with an average size of 80 nm. At 1C rate, the initial irreversible capacity of polycrystalline CoFe₂O₄ film electrode cycled between 0.01 and 3.0 V reached 1280 mAh/g. After 20 cycles, the reversible discharge capacities decreased and sustained about 610 mAh/g. The diffusion coefficient of Li ion for CoFe₂O₄ films was determined by ac impedance method, and the average value was estimated to be 1.1 × 10⁻¹³ cm²/S. Based on ex situ XRD, SEM and XPS data, the electrochemical mechanism of CoFe₂O₄ film with lithium upon cycling was proposed. During the first discharge, the amorphization process of CoFe₂O₄ film electrode is accompanied with the reduction of Co²⁺ and Fe³⁺ into metal Co and Fe, respectively, and then the reversible oxidation/reduction processes of Co, Fe and Li₂O take place in the subsequent charge/discharge cycles.     

Synthesis and electrochemical behaviour of tin oxide for use as anode in lithium rechargeable batteries

SnO₂ was synthesized by precipitation from an aqueous solution of SnCl₄ and NH₄OH, followed by a heat treatment. The product was characterized by XRD, SEM, FTIR spectroscopy, DSC and TG. The XRD patterns suggest the formation of phase-pure cassiterite form of SnO₂. SEM imaging indicates that the particles obtained are of sub-micron size with good morphology and size control (around ∼300 nm). Electrodes were fabricated by a slurry-coating procedure and the electrochemical performances of these electrodes were evaluated using galvanostatic cycling tests. The results suggest that the heat treated SnO₂ samples deliver higher capacities when cycled between 1.0 and 0.1 V vs. Li⁺/Li and showed coulombic efficiencies of more than 98% in the tenth cycle.     

Polymer microsphere embedded Si/graphite composite anode material for lithium rechargeable battery

Si/graphite composite materials embedded with polymer microsphere as an elastic inactive phase were prepared by high-energy mechanical milling and investigated as a high capacity anode material for lithium rechargeable battery. Improved capacity retention was achieved with the composite. In situ measurement of the electrode thickness revealed that the swelling of the electrode became smaller with the increase of polymer microsphere content. It is believed that polymer microsphere played a buffering role of accommodating the mechanical strains induced by silicon expansion during lithiation, resulting in the suppression of the volume expansion of the electrode, which improved the cycle performance of the electrode.     

锂离子电池锡基负极材料的研究进展

锡基负极材料与碳负极材料相比,具有容量密度高,安全性好等优点,成为动力锂离子电池用新型负极材料研究的热点之一。本文综述了近年来国内外针对锡基材料首次不可逆容量高、循环性能差等问题所进行的改性研究,分别从材料的制备方法、组成结构及电化学性能等方面进行比较分析,并对锡基负极材料的进一步研究、发展应用予以展望。     

A novel nanosized silicon-based composite as anode material for high performance lithium ion batteries

A new kind of silicon-based composite anode with high initial coulombic efficiency and good cycling performance is synthesized by a wet high energy mechanical milling technique and characterized by X-ray diffraction, transmission electron microscope and high resolution transmission electron microscope. It is demonstrated that the in situ formed Si particles with size of 5–10 nm are uniformly distributed in the elastic matrices consisting of the in situ formed Li-containing compounds, amorphous P₂O₅, SiP₂O₇, Ni, Si–Ni alloys and conductive graphite. The elastic matrices can effectively alleviate the volume variations of the active Si particles during long-term cycling. The as-prepared silicon-based composite electrode reveals an initial discharge and charge capacity of 549 and 565.3 mAh g⁻¹, respectively, with an initial coulombic efficiency of 103%. After 80 cycles, the reversible capacity of the composite electrode is up to 560.7 mAh g⁻¹ with a capacity retention rate of 99%.