Facile hydrothermal and sol-gel synthesis of novel Sn-Co/C composite as superior anodes for Li-ion batteries

As an anode material in lithium ion battery, the Sn-Co/C composite electrode materials have been successfully synthesized by hydrothermal and solgel methods, respectively. The resultant composites were mainly composed of Snbased oxides, nanometer Sn-Co alloy and carbon. Carbon and Co, acting as buffer materials, can accommodate to the large volume change of active Sn during the discharge-charge process, thus improving the cycling stability. Although charge/discharge curves revealed the excellent cycle performance for samples synthesized by both methods, composites obtained by the sol-gel showed a better dispersion effect of nanoparticles on the carbon matrix and possessed much more improved stable capacity with 624.9 mAh g-1 over 100 cycles and that by hydrothermal method only exhibited ～299.3 mAh g-1. Therefore, the Sn-Co/C composites obtained by solgel synthesis method could be a perfect candidate for anode material of Liion storage battery.     

Polymeric artificial solid/electrolyte interphases for Li-ion batteries

During the operation of Li-ion batteries(LIBs),solvent and electrolyte decomposition takes place at the electrode surface to form a so-called solid-electrode interphase(SEI) passivating-layer.The physical structure and chemical composition of the SEI exert profound effects on various aspects of the electrode performance of the batteries.A new concept of forming polymeric artificial SEIs(A-SEIs) based on rational design of multifunctional polymer-blend coating to achieve favorable electrode/A-SEI/electrolyte interfacial properties is described.Three examples using binary and ternary polymer blends to form mechanically robust and highly Li-ion permeable surface coatings with selected functionalities in the cases of graphite and silicon–graphite composite electrodes have demonstrated greatly enhanced capacity,rate and cycle performance.Given the rich chemistry available from polymer blends,this surface preconditioning approach holds great promise for improving the performance of various negative electrodes to meet the requirements for advanced LIBs.     

Pseudo-capacitance of ruthenium oxide/carbon black composites for electrochemical capacitors

Hydrous ruthenium oxide was formed by a new process. The precursor was obtained by mixing the aqueous solutions of RuCl₃·xH₂O and NaHCO₃. The addition of NaHCO₃ led to the formation of an oxide with extremely fine RuO₂ particles forming a porous network structure in the oxide electrode. Polyethylene glycol was added as a controller to partly inhibit the sol-gel reaction. The rate capacitance of 530 F·g-1 was measured for the powder formed at an optimal annealing temperature of 210℃. Several details concerning this new material, including crystal structure, particle size as a function of temperature, and electrochemical properties, were also reported. In addition, the rate capacitance of the composite electrode reached 800 F·g-1 after carbon black was added. By using the modified electrode of a RuO₂/carbon black composite electrode, the electrochemical capacitor exhibits high energy density and stable power characteristics. The values of specific energy and maximum specific power of 24 Wh·kg-1 and 4 kW·kg-1, respectively, are demonstrated for a cell voltage between 0 and 1 V.     

用于高性能超级电容器的基于蚕沙的二氧化锰/碳纳米复合材料

MnO₂/biomass carbon nanocomposite was synthesized by a facile hydrothermal reaction. Silkworm excrement acted as a carbon precursor, which was activated by ZnCl₂ and FeCl₃ combining chemical agents under Ar atmosphere. Thin and flower-like MnO₂ nanowires were in-situ anchored on the surface of the biomass carbon. The biomass carbon not only offered high conductivity and good structural stability but also relieved the large volume expansion during the charge/discharge process. The obtained MnO₂/biomass carbon nanocomposite electrode exhibited a high specific capacitance (238 F·g?1 at 0.5 A·g?1) and a superior cycling stability with only 7% degradation after 2000 cycles. The observed good electrochemical performance is accredited to the materials’ high specific surface area, multilevel hierarchical structure, and good conductivity. This study proposes a promising method that utilizes biological waste and broadens MnO₂-based electrode material application for next-generation energy storage and conversion devices.     

Preparation and Characterization of Carbon Coated Silicon Nanoparticle as Anode Material for Li-ion Batteries

Silicon has been regarded as one of the most promising anode materials for Li-ion batteries. Its theoretical capacity （4 000 mAh/g） is much higher than that of the commercialized graphite （372 mAh/g）. However, the cycle performance of silicon is poor due to the severe volume expansion and shrinkage during Li^＋ insertion/extraction which results in pulverization of Si particles, eventually losing its Li^＋ storage ability. To solve this problem, nanosized Si particles were utilized and achieved a partial improvement by reducing the absolute volume change. Nevertheless, a new problem was encountered with nanosized material that small Si particles were aggregated to be larger one during Li^＋ insertion/extraction, and then pulverized again. In this work, we have succeeded to improve the cycle performance of nanosized Si particles by synthesis of carbon coated silicon nanopartiele.     

Promotive effect of multi-walled carbon nanotubes on Co3O4 nanosheets and their application in lithium-ion battery

Co3O4/MWCNTs composites have been synthesized by a simple hydrothermal method using a surfactant(CTAB) and a precipitation agent(urea). The samples were characterized by XRD, SEM and BET methods. The electrochemical properties of the samples as anode materials for lithium batteries were studied by EIS and Galvanostatic measurements. The Co3O4/MWCNTs composites displayed higher capacity and better cycle performance in comparison with the Co3O4 nanosheets. The remarkable improvement of electrochemical performance within the hybrid composites is probably related to the addition of MWCNTs that possesses improved properties such as excellent electric conductivity and large surface area, which helps to alleviate the effect of volume change, shorten the distance of lithium ion diffusion, facilitate the transmission of electron and keep the structure stable.     

Performance of a combined capacitor based on ultrafine nickel oxide/carbon nanotubes composite electrodes

A new sol-gel process for the preparation of ultrafine nickel hydroxide electrode materials was developed. The composite electrodes consisting of carbon nanotubes and Ni(OH)₂ were developed by mixing the hydroxide and carbon nanotubes together in different mass ratios. In order to enhance energy density, a combined type pseudocapacitor/electric double layer capacitor was considered and its electrochemical properties were characterized by cyclic voltammetry and dc charge/discharge test. The combined capacitor shows excellent capacitor behavior with an operating voltage up to 1.6 V in KOH aqueous electrolyte. Stable charge/discharge behaviors were observed with much higher specific capacitance values of 24 F/g compared with that of EDLC (12F/g) by introducing 60% Ni(OH)₂ in the anode material. By using the modified anode of a Ni(OH)₂/carbon nanotubes composite electrode, the specific capacitance of the cell was less sensitive to discharge current density compared with that of the capacitor employing pure nickel hydroxide as anode. The combined capacitor in this study exhibits high energy density and stable power characteristics.     

Electrochemical characterization of MnO2 as the cathode material for a high voltage hybrid capacitor

Manganese dioxide (MnO₂) was prepared using the ultrasonic method. Its electrochemical performance was evaluated as the cathode material for a high voltage hybrid capacitor. And the specific capacitance of the MnO₂ electrode reached 240 F·g-1. The new hybrid capacitor was constructed, combining A1/Al₂O₃ as the anode and MnO₂ as the cathode with electrolyte for the aluminum electrolytic capacitor to solve the problem of low working voltage of a supercapacitor unit. The results showed that the hybrid capacitor had a high energy density and the ability of quick charging and discharging according to the electrochemical performance test. The capacitance was 84.4 μF, and the volume and mass energy densities were greatly improved compared to those of the traditional aluminum electrolytic capacitor of 47 μF. The analysis of electrochemical impedance spectroscopy (EIS) showed that the hybrid capacitor had good impedance characteristics.     

Electrochemical performance of MCMB/(AC+LiFePO4) lithium-ion capacitors

Lithium-ion capacitors(LICs) were fabricated using mesocarbon microbeads(MCMB) as a negative electrode and a mixture of activated carbon(AC) and LiFePO4 as a positive electrode(abbreviated as LAC).The phase structure and morphology of LAC samples were characterized by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM).The electrochemical performance of the LICs was studied using cyclic voltammetry,charge-discharge rate measurements,and cycle performance testing.A LIC with 30 wt% LiFePO4 was found to have the best electrochemical performance with a specific energy density of 69.02 W h kg-1 remaining at 4 C rate after 100 cycles.Compared with an AC-only positive electrode system,the ratio of practical capacity to theoretical calculated capacity of the LICs was enhanced from 42.22% to 56.59%.It was proved that adding LiFePO4 to AC electrodes not only increased the capacity of the positive electrode,but also improved the electrochemical performances of the whole LICs via Li+ pre-doping.     

碳点修饰硅在锂离子电池中的应用研究

Silicon (Si) particles were functionalized using carbon dots (CDs) to enhance the interaction between the Si particles and the binders. First, CDs rich in polar groups were synthesized using a simple hydrothermal method. Then, CDs were loaded on the Si surface by impregnation to obtain the functionalized Si particles (Si/CDs). The phases and microstructures of the Si/CDs were observed using Fourier-transform infrared reflection, X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. Si/CDs were used as the active material of the anode for electrochemical performance experiments. The electrochemical performance of the Si/CD electrode was assessed using cyclic voltammetry, electrochemical impedance spectroscopy, and constant current charge and discharge experiment. The electrodes prepared with Si/CDs showed good mechanical structure stability and electrochemical performance. After 150 cycles at 0.2 C, the capacity retention rate of the Si/CD electrode was 64.0%, which is twice as much as that of pure Si electrode under the same test conditions.     

高容量型锂离子电池硅基负极材料的研究进展

硅基负极材料由于其具有高容量而被广泛研究,该材料在充/放电过程中巨大的体积变化、低的循环寿命和初始库仑效率阻碍了其商业化应用. 本文分析了硅基负极材料的工作原理,回顾了其在脱/嵌锂过程中的晶体结构、表面/界面的变化以及提高其电化学性能的方法,讨论了锂离子电池硅基负极材料的前景.     

不同载硅量对Li2FeSiO4/C材料电性能的影响

以多壁纳米碳管和Si(OC2H5)4为原料,采用液相法合成包覆了SiO2的多壁碳纳米管(MWCNTs@SiO2),通过调节Si(OC2H5)4的加入量,制备出不同载硅量的前驱体MWCNTs@SiO2,并以此种前驱物合成硅酸铁锂Li2FeSiO4/C材料.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、恒流充放电对Li2FeSiO4/C材料进行了表征及电化学性能测试,实验结果表明载硅量为35.72%的MWCNTs@SiO2前驱体合成的Li2FeSiO4/C材料颗粒大小一致,在0.1C电流密度下循环50圈后获得180 mAh·g－1的稳定放电比容量,具有优良的电化学性能.     

Nanostructure designing and hybridizing of high-capacity silicon-based anode for lithium-ion batteries

Lithium-ion batteries have long been used in electronic products and electric vehicles, but their energy density is slowly failing to keep up with demand. Because of its extraordinarily high theoretical specific capacity, silicon is regarded as the most potential next-generation anode material for practical lithium-ion batteries. However, its unavoidable volume expansion issue can cause electrode deformation and loss of electrical contact during cycling,resulting in significant performance reduc...     

Review of silicon-based alloys for lithium-ion battery anodes

Silicon (Si) is widely considered to be the most attractive candidate anode material for use in next-generation high-energy-density lithium (Li)-ion batteries (LIBs) because it has a high theoretical gravimetric Li storage capacity, relatively low lithiation voltage, and abund-ant resources. Consequently, massive efforts have been exerted to improve its electrochemical performance. While some progress in this field has been achieved, a number of severe challenges, such as the element’s large volume change during cycling, low intrinsic electronic conduct-ivity, and poor rate capacity, have yet to be solved. Methods to solve these problems have been attempted via the development of nanosized Si materials. Unfortunately, reviews summarizing the work on Si-based alloys are scarce. Herein, the recent progress related to Si-based alloy an-ode materials is reviewed. The problems associated with Si anodes and the corresponding strategies used to address these problems are first de-scribed. Then, the available Si-based alloys are divided into Si/Li-active and inactive systems, and the characteristics of these systems are dis-cussed. Other special systems are also introduced. Finally, perspectives and future outlooks are provided to enable the wider application of Si-alloy anodes to commercial LIBs.     

MnO@CoMn$_{\textbf{2}}$O$_{\textbf{4}}$/N-C纳米线复合材料的制备及其作为锂离子电池阳极材料的电化学性能

过渡金属氧化物作为锂离子电池(lithium-ion batteries, LIBs)阳极材料时具有较高的理论容量, 但因其电导率低, 以及充放电过程中的体积膨胀效应常会导致容量的快速衰减. 碳包覆是提升金属氧化物导电性的有效方法, 二者之间的协同效应也可以有效提升材料的电化学性能. 以MnO$_{2}$纳米线为模板制备出MnO$_{2}$@ZIF-67有机-无机杂化纳米结构, 再通过退火处理合成了氮掺杂碳包覆的MnO@CoMn$_{2}$O$_{4}$纳米线复合材料(MnO@CoMn$_{2}$O$_{4}$@N-C). ZIF-67的有机配体在高温煅烧过程中发生碳化反应, 产生了氮掺杂碳, 提升了导电性. 当作为锂离子电池阳极材料时, MnO@CoMn$_{2}$O$_{4}$/N-C纳米线复合材料在0.1 A/g电流密度下的首次放电比容量为1 594.6 mA$\cdot$h/g, 并且在100次充放电循环后的放电比容量仍保持在 925.8 mA$\cdot$h/g, 在0.5 A/g电流密度下经200次充放电循环后的放电比容量仍维持在837.6 mA$\cdot$h/g, 同时具有优异的倍率循环性能. 这种优异的电化学储能特性主要来源于复合材料的特殊结构, 以及氮掺杂碳的包覆.     

锂离子电池多孔硅／碳复合负极材料研究

以硅粉、镁粉和葡萄糖为原料,采用高温固相烧结工艺及水热法制备了循环性能优异的锂离子电池多孔硅／碳复合负极材料．利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）对样品物相和微观形貌进行表征,研究了无定形碳包覆量对产物电化学性能的影响．无定形碳的存在,不仅对多孔硅粉的三维孔隙结构起到了支撑作用,也可有效改善复合材料的导电性能并有效缓冲电化学嵌／脱锂过程中多孔硅颗粒所产生的体积效应．电化学性能测试表明,10次循环后,多孔硅／碳复合负极材料平均每周次容量衰减为0．41%,100次循环后其可逆容量仍可维持在608．7mA·h／g．     

CuO微米梭的制备及其电化学性能研究

尽管各种各样的CuO纳米结构已被广泛应用于锂离子电池负极材料的研究,但将CuO微米梭作为锂离子电池负极材料却鲜有报道. 运用简单的溶剂热法制备大量的CuO微米梭,并用作锂离子电池负极材料. 实验表明,CuO微米梭在电流密度为100 mA g-1下充放电循环100次后,放电容量依然保持在484 mAh g-1. CuO微米梭优异的电化学性能归功于其独特的梭形结构. 这种结构在锂离子电池充放电过程中可以缩短锂离子和电子的传输距离,缓解体积膨胀效应.     

硅/碳复合材料的高温热解法制备及其电化学性能

采用高温热解方法成功地合成了高容量硅/碳复合负极材料.通过X射线衍射分析、热重分析、扫描电子显微镜观察、透射电子显微镜观察、恒电流充放电测试、循环伏安法等手段研究了复合材料的性能.结果表明：硅/碳复合材料由Si、C以及少量SiO2组成;硅/碳复合材料中碳的质量分数约在39%左右;经电化学性能测试,在电流0.2 mA下,该硅/碳复合材料首次充电容量768 mAh·g-1,首次库仑效率75.6%,70次循环后可逆比容量仍为529 mAh·g-1,平均容量衰减率为0.44%.这些性能改善归因于硅/碳复合材料中碳的引进,硅表面存在的碳涂层提供了一个快速锂运输通道,降低了电池的阻抗并且充放电过程中稳定了电极的组成.     

锂离子电池炭负极的结构与特性及其电化学性能

通过计算边缘碳原子及表面碳原子含量计算,研究边缘碳及表面碳原子含量对炭材料的电化学性能的作用机理。导出炭材料的结构与物理特性对炭材料的嵌锂性能的影响。通过对不同形貌、粒径、比表面积及有序程度的人造石墨、中间相炭微球及热解炭的电化学性能的研究,验证该机理的正确性。应用这一机理分析对人造石墨进行热处理改性,以及在人造石墨表面包覆无定形炭的改性作用。研究结果表明:边缘碳及表面碳原子的含量对固体-电解质中间相(SEI)膜的形成以及SEI膜的均匀、稳定性具有重要的作用,从而影响炭材料的首次不可逆容量及循环性能。     

锂离子电池碳负极中边缘碳及表面碳原子含量的理论计算

通过理论分析与计算得到边缘碳及表面碳原子含量的表达式。分析了石墨微晶结构与成键特征,研究了石墨微晶中边缘碳原子与基平面碳原子的电化学特性。结果表明:边缘碳原子比基平面碳原子更易于与其他原子或基团形成较为稳固的联接,电化学反应活性较高;在首次充电过程中,边缘碳原子附近电解质的分解与SEI膜成膜反应速度较快,有利于形成联接较为紧密的SEI膜;建立了紧密堆砌的正六棱柱颗粒模型,推导出理想石墨中边缘碳原子及表面碳原子含量与微晶参数、颗粒尺寸之间的关系式。通过引入适当因子,修正了实际石墨颗粒与理想石墨在结构、形貌、孔隙率等方面的差别,得到的表达式可适用于石墨、无定形碳及改性碳等多种碳材料碳原子含量的计算。