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Graphitization Mechanisms and Electrochemical Performance of Needle Coke Anode for Li―ion Battery
WANG Deng-Jun, WANG Yan-Li, ZHAN Liang, ZHANG Xiu-Yun, Liu Chun-Fa, QIAO Wen-Ming, LING Li-Cheng
无机材料学报 , 2011, DOI: 10.3724/sp.j.1077.2011.00619
Abstract: Effects of heat―treatment temperature on the microstructure and electrochemical properties of coal based needle coke were investigated by TG―DTG, XRD, SEM, XPS analysis and the charge/discharge, cyclic voltammetry curves. The graphitization mechanism of needle coke is suggested as well as the Li+ extraction―insertion behaviors. With the heat―treatment temperature increasing, the graphite―like crystal grows continuously attended with a complicated process, including the arrangement of crystal along radial/axial direction, dislocation dispersion among graphite layers, hexagonal carbon formation, crystal edge dispersion and folded graphite layer turning to plane. Meanwhile, the driving―forces are far different for different process. When needle coke is graphitized at 2800 , it exhibits a lower charge/discharge potential and stable charge/discharge platform, and the insertion capacitance of Li+ can maintain at 305mAh/g even after charge/discharged for 40 cycles.
Effect of Crystallinity on Electrochemical Insertion/Extraction of Li in Transition Metal Oxides Part I: LiMn2O4 and LiCo0.5Ni0.5O2
Effect of Crystallinity on Electrochemical Insertion/Extraction of Li in Transition Metal Oxides Part I: LiMn_2O_4 and LiCo_(0.5)Ni_(0.5)O_2


材料科学技术学报 , 1999,
Abstract: Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materials on electrochemical Li insertion/extraction performance was discussed. These two transition metal oxides belong to one group that the crystallinity of these oxides affects to the performance.
Effect of crystallinity on electrochemical insertion/extraction of Li in transition metal oxides - Part II: TiO2, V2O5 and MoO3


材料科学技术学报 , 2000,
Abstract: Electrochemical insertion/extraction sf Li on cathode materials of anatase type TiO2, quasi-layered structure V2O5 and layered structure MoO3 was measured on samples of which structures were well characterized and showed a wide range of crystallinity. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materials on electrochemical Li insertion/extraction performance was discussed. These three transition metal oxides were classified as one group on the basis of whether the crystallinity of these oxides affects to the performance or not, LiMn2O4 and LiCo0.5Ni0.5O2 belongs to the former group and TiO2, V2O5 and MoO3 to the latter.
Influence of the C/Sn Ratio on the Synthesis and Lithium Electrochemical Insertion of Tin-Supported Graphite Materials Used as Anodes for Li-Ion Batteries  [PDF]
Cédric Mercier,Rapha?l Schneider,Patrick Willmann,Denis Billaud
International Journal of Electrochemistry , 2011, DOI: 10.4061/2011/381960
Abstract: Novel composites consisting of tin particles associated to graphite were prepared by chemical reduction of tin(+2) chloride by -BuONa-activated sodium hydride in the presence of graphite. The samples obtained using various C/Sn ratios were investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and elemental analyses. The largest tin particles associated to graphite layers were observed for the material with a C/Sn ratio of 16. For the materials with C/Sn ratios of 42 and 24, SEM and TEM experiments demonstrated that Sn aggregates of ca. 250?nm length and composed of Sn particles with an average diameter of ca. 50?nm were homogeneously distributed at the surface of graphite. Electrodes prepared from the material exhibit a high reversible capacity of over 470?mAh up to twenty cycles with stable cyclic performances. 1. Introduction With the development of portable electronic devices and the enormous interest in the hybrid electric vehicle market, the demand for power sources with higher storage capacity, longer operating times, as well as safety, environmental compatibility, and low production costs has markedly increased [1]. Graphite is mainly used as negative electrode materials for lithium ion secondary batteries and yields a theoretical capacity of 372?mAhg?1. Lithium alloys, which can be reversibly formed and decomposed electrochemically in nonaqueous electrolyte solutions, are natural alternative candidates to both lithium and lithiated graphite in rechargeable Li-based batteries. Of special importance in this respect are the lithium-tin compounds. Indeed, both metallic tin and tin oxide (SnO2) were shown as interesting anode materials for Li-ion batteries because of their conducting properties combined with high specific capacities (Sn, 994?mAhg?1 and SnO2, 781?mAhg?1) [2, 3] compared to that of graphite [4, 5]. Lithium can be inserted into tin to form alloys of high Li content up to Li22Sn5, corresponding to a theoretical capacity of 994?mAhg?1 [2]. Although these attractive features have initiated a number of studies on Sn-based hosts [4, 6–19], Li+ ion insertion/extraction into/from Sn causes volume changes [9, 20, 21]. These changes result in cracking and crumbling of the electrode with the concomitant loss of electrical contact both between interparticles, and between particles and the current collector, resulting in poor cycling performance. A promising way of improving the cyclability of Sn-based electrodes is to synthesize small-sized Sn particles. We have recently
Synthesis and Electrochemical Characterization of Li2MnSiO4 with Different Crystal Structure as Cathode Material in Lithium Rechargeable Batteries  [PDF]
Joongpyo Shim, Sora Won, Gyungse Park, Ho-Jung Sun
Advances in Materials Physics and Chemistry (AMPC) , 2012, DOI: 10.4236/ampc.2012.24B048

Li2MnSiO4 with different crystal structure was synthesized by solid state reaction method. Their crystal structure and electrochemical properties have been characterized by X-ray diffraction and charge-discharge test. The material prepared at 900oC in N2 atmosphere had γ-phase and its crystal structure changed to β-phase by post-heating at 400oC in air after 900oC sintering. In electrochemical measurement, two materials (γ- and β-phase) showed ~3 and ~45mAh/g, respectively. The different capacities of these two materials might be due to the change of crystal structure.

电化学嵌锂γ—Li_xFe_2O_3的晶体结构  [PDF]
金属学报 , 1992,
Abstract: 本文以Mossbauer谱学为主,辅以X射线衍射、XPS及电化学方法研究了电化学嵌锂γ-Li_xFe_2O_3的晶体结构。结果表明,以较小电流密度嵌锂时,晶体结构保持原来的尖晶石型;当以较大电流密度嵌锂或热激活时,由于Li~+的运动加剧,部分晶体结构转变为类似于氧化亚铁的面心立方结构。文中揭示了Li~+嵌入过程中的跃迁通道。讨论了Li~+的极限嵌入量。
Preparation, Characterization and Electrochemical Lithium Insertion Into the New Organic–Inorganic Poly(3,4-Ethylene Dioxythiophene)/ Hybrid  [PDF]
Chai-Won Kwon,A. Vadivel Murugan,Guy Campet
Active and Passive Electronic Components , 2003, DOI: 10.1080/1042015031000073904
Abstract: Poly(3,4-ethylene dioxythiophene) (PEDOT) has been inserted between the layers of crystalline V2O5 via the in situ polymerization of EDOT within the framework of the oxyde. The insertion increases the bidimensionality of the V2O5 host by the layer separation but results in a random layer stacking structure, leading to broadening of the energy state distribution. According to electrochemical measurements, the hybrids showed reversible specific capacities up to ∼330 mAh/g at 15mA/g between 2 and 4.4V vs. Li
A model for electrochemical insertion limited by a phase transition process - eilpt  [PDF]
Adhoum N.,Bouteillon J.,Dumas D.,Poignet J.C.
Journal of Mining and Metallurgy, Section B : Metallurgy , 2003, DOI: 10.2298/jmmb0302353a
Abstract: This paper deals with electrochemical insertion into a cathodic material. New results on modeling of the influence of a solid phase transformation on the shape of voltamograms are presented. The original experiments concern the insertion of sodium into carbon during the cathodic reduction of molten NaF at 1020 °C, but in the present manuscript emphasis on the theoretical aspects of the work is put. Phase transformations during electrochemical insertion are taken into account, with various values for parameters such as the thermodynamic biphase equilibrium potential, the compared diffusion and phase transformation kinetics, and the electrode thickness. The voltamograms calculated present very specific features; some of them have already been observed experimentally in literature.
Li+ distribution into V2O5 films resulting from electrochemical intercalation reactions
Decker, Franco;Donsanti, Frederique;Salvi, Anna Maria;Ibris, Neluta;Castle, James E.;Martin, Franz;Alamarguy, David;Vuk, Angela Surca;Orel, Boris;Lourenco, Airton;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000400009
Abstract: we studied interface effects of thin film v2o5 electrodes on top of indium tin oxide (ito) glass for li intercalation by means of a combination of methods: depth-profiling by secondary ion mass spectroscopy (sims), electrochemical insertion-extraction of lithium ions by slow-scan cyclic voltammetry (sscv) and by potentiostatic intermittent titration technique (pitt). we show that the li+ distribution inside the oxide film is always far from homogeneous, and that different diffusion paths (parallel to interfaces as well as perpendicular to them) have to be considered in experiments with electrodes having areas of few cm2. the exposed edge formed when cutting out coupons from the coated glass plate supporting the v2o5 electrode plays a significant role in the process, because it exposes the v2o5-ito interface to the electrolyte.
Boletín de la Sociedad Chilena de Química , 2001, DOI: 10.4067/S0366-16442001000300016
Abstract: we have studied the lithium insertion into lim2o4 (m = mn, fe, co) using n-buli and electrochemical techniques. the oxides crystallized in the pure spinel phase s.g. oh7(fd3m). probable cationic distributions were proposed based on xrd, m?ssbauer and pzc measurements. the results demonstrate that an important factor in the extent of the lithium insertion reaction in mixed oxides is the presence of the highest oxidation state in the transition metal cations that are located in b-sites of the spinel framework
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