Electrochemical properties of NiO/Co-P nanocomposite as anode materials for lithium ion batteries

NiO/Co-P nanocomposite is prepared by an electroless cobalt plating technique. The as-prepared composite is characterized by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. SEM and TEM images reveal that the NiO particles are about 200 nm in size, which are modified by Co-P nanoparticles of about 30 nm. The electrochemical properties as anode materials for lithium ion batteries are examined by cyclic voltammetry (CV) and discharge-charge tests. The results show that, compared with the bare NiO without electroless cobalt plating, NiO/Co-P nanocomposite exhibits a smaller polarization and a better rate capability, which is attributed to the Co-P nanoparticles.     

CoSb3-graphite composite anode material for lithium ion batteries

The CoSb3-graphite composite was prepared by ball-milling. The electrochemical performance of the composite material was evaluated using the lithium ion model cell Li/ LiPF6 (EC DMC) / CoSb3C4. It was found that the CoSb3C4 composite shows higher reversible capacity than the pure CoSb3 alloy, and its firSt reversible (Li-ions removal) capacity reaches 721 mA.h.g^-1, which exceeds the theoretical capacity (550 mA.h.g^-1) of CoSb3C4.     

Electrochemical properties of the carbon-coated lithium vanadium oxide anode for lithium ion batteries

Carbon-coated Li_1.1V_0.9O₂ powder was prepared by dissolving pure crystalline Li_1.1V_0.9O₂ powder in an ethanol solution containing 10 wt% sucrose and sintering it under an argon atmosphere. The structures of the bare and carbon-coated Li_1.1V_0.9O₂ powders were analyzed using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. These powders were used as anode active materials for lithium ion batteries in order to determine the electrochemical properties via cyclic voltammetry (CV) and constant current methods. CV revealed the carbon-coated Li_1.1V_0.9O₂ anode to have better reversibility during cycling than the bare Li_1.1V_0.9O₂ anode. Carbon-coated Li_1.1V_0.9O₂ also showed a higher specific discharge and charge capacities, as well as lower electrolyte and interfacial resistance properties. The observed specific discharge and charge capacities of the carbon-coated Li_1.1V_0.9O₂ anode were 330 mAh/g and 250 mAh/g, respectively, in the first cycle. In addition, the cyclic efficiency of this cell was 75.8% in the first cycle. After 20 cycles, the specific capacity of the Li_1.1V_0.9O₂ anode was reduced to approximately 50% of its initial capacity, irrespective of the presence of a carbon coating.     

Si-doped composite carbon as anode of lithium ion batteries

1　INTRODUCTIONAdvancedrechargeablelithiumionbatteriesareattractiveforuseinconsumableelectronicandelectricvehicles(EV )becauseoffavorablecombinationofvoltage,energydensity ,cycling performance ,etc .Worldwideeffortshavebeendevotedtothestudyofcarbonmaterialsasanodesinthesebatteries .Amongavarietyofcarbonmaterials ,graphiteappearstobethemostsuitablecandidatebecauseofitshighcapaci ty ,lowandflatpotential[1,2 ] .Nevertheless ,therearestillsomeproblemswithrespecttothedestructionofthecarbonstr…     

Preparation of Fe2O3/graphene composite and its electrochemical performance as an anode material for lithium ion batteries

The micro-sized sphere Fe₂O₃ particles doped with graphene nanosheets were prepared by a facile hydrothermal method. The obtained Fe₂O₃/graphene composite as the anode material for lithium ion batteries showed a high discharge capacity of 660 mAh g⁻¹ during up to 100 cycles at the current density of 160 mA g⁻¹ and good rate capability. The excellent electrochemical performance of the composite can be attributed to that graphene served as dispersing medium to prevent Fe₂O₃ microparticles from agglomeration and provide an excellent electronic conduction pathway.     

Large-scale synthesis of macroporous SnO2 with/without carbon and their application as anode materials for lithium-ion batteries

The macroporous SnO₂ is prepared using close packed carbonaceous sphere template which synthesized from glucose by hydrothermal method. The structure and morphology of the macroporous SnO₂ are evaluated by XRD and FE-SEM. The average pore size of the macroporous SnO₂ is about 190 nm and its wall thickness is less than 10 nm. When the macroporous SnO₂ filled with carbon is used as an anode material for lithium-ion battery, the capacity is about 380 mAh g⁻¹ after 70 cycles. The improved cyclability is attributed to the carbon matrix which is used as an effective physical buffer to prevent the collapse of the well dispersed macroporous SnO₂.     

Stress generation during lithiation of high-capacity electrode particles in lithium ion batteries

A model is developed to study the stress generation in a spherical particle subjected to lithium insertion. The model accounts for both the plastic deformation and the coexistence of lithium-poor and lithium-rich phases with a sharp and curved phase boundary. Such two-phase and inelastic deformation characteristics often arise during lithiation of crystalline particles with high capacity. A flexible sigmoid function is used to create the lithium profile with a step-like change in lithium concentration, mimicking a sharp phase boundary that separates a pristine core and a lithiated shell in the particle. The mechanics results, obtained by an analytic formulation and finite difference calculations, show the development of tensile hoop stress in the surface layer of the lithiated shell. This hoop tension provides the driving force of surface cracking, as observed by in situ transmission electron microscopy. The two-phase lithiation model is further compared with the single-phase one, which assumes a gradual and smooth variation in radial lithium distributions, and thus predicts only hoop compression in the surface layer of the particle. Furthermore, the effect of dilatational vs. unidirectional lithiation strains in the two-phase model is studied, thereby underscoring the critical role of anisotropy of lithiation strain in controlling stress generation in high-capacity electrodes for lithium ion batteries.     

生物模板法制备MnO/C复合材料及其储锂性能研究

以天然的柚子皮为生物模板,高锰酸钾为锰源,通过化学浴(CBD)方法和后续煅烧处理制备MnO/碳(MnO/C)复合材料。采用X射线衍射(XRD),热重-差热分析法(TG-DTA),拉曼(Raman),扫描电子显微镜(SEM)和透射电子显微镜(TEM)对材料的物相组成、形貌和微结构进行表征。结果表明,柚子皮模板原位转变为碳基体,同时MnO颗粒均匀负载于碳基体形成MnO/C复合材料,其中碳含量约为30%。电化学测试表明该复合材料具有优异的储锂性能,在0.2 A/g电流密度下循环100次后可逆容量依旧保持在664 mAh/g,在3 A/g大电流密度下,可逆容量仍有441 mAh/g。     

Mechanism of lithium insertion into NiSi2 anode material for lithium ion batteries

As a promising high capacity anode material for lithium ion batteries, the lithium insertion performance and possible insertion mechanism of binary alloy of NiSi2 were discussed. The initial lithium insertion of crystal NiSi2 can reach up to 600 mAh·g-1 , but large irreversible capacity occurrs simultaneously for serious structure transformation and the irreversible phase forms. XRD and XPS were employed to detect the crystal structure and composition changes produced by lithium insertion. The lithium insertion-extraction behavior of NiSi2 electrode is similar to that of silicon after the first discharge. The structure stability seems related to the non-stoichimometric Ni-Si compound formed by lithium insertion into NiSi2.     

A novel method to synthesize anatase TiO2 nanowires as an anode material for lithium-ion batteries

We demonstrate a simple and novel approach for the synthesis of a kind of anatase TiO₂ nanowires. The method is based on a hydrothermal method under normal atmosphere without using the complex Teflon-lined autoclave, high concentrations NaOH solution and long react time. The as-prepared materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The obtained anatase TiO₂ nanowires show excellent performance. There is a potential plateau at 1.77 and 1.88 V in the process of Li insertion and extraction, and the initial Li insertion/extraction capacities are 283 and 236 mAh g⁻¹ at the density of 20 mA g⁻¹, respectively. In the 20th cycle, the reversible capacities still remain about 216 and 159 mAh g⁻¹ at the current densities of 20 and 200 mA g⁻¹, respectively, and the coulombic efficiency is more than 98%, exhibiting excellent electrochemical performance.     

Electrochemical properties of novel calcium stannate anode for lithium ion batteries

1 INTRODUCTIONThe reversible alloying and dealloying proper-ties of Sn with Li have gained wide spread interestdue to its potentiality to use as anode material inLi-ion batteries[1 8]. The searchfor Sn-based mate-rials gained momentum after the report of nearly600 mA·h·g-1reversible capacity observed inamorphous Sn-based composite oxides (ATCO)[1].By in situ X-ray diffraction, Courtney et al[2 ,3]showed that the reversible Li-Sn alloy formationisresponsible for the observed reversi…     

Mechanism for capacity fading of 18650 cylindrical lithium ion batteries

The mechanism for capacity fading of 18650 lithium ion full cells under room-temperature (RT) is discussed systematically. The capacity loss of 18650 cells is about 12.91% after 500 cycles. The cells after cycles are analyzed by XRD, SEM, EIS and CV. Impedance measurement shows an overall increase in the cell resistance upon cycling. Moreover, it also presents an increased charge-transfer resistance (R_ct) for the cell cycled at RT. CV test shows that the reversibility of lithium ion insertion/extraction reaction is reduced. The capacity fading for the cells cycled can be explained by taking into account the repeated film formation over the surface of anode and the side reactions. The products of side reactions deposited on separator are able to reduce the porosity of separator. As a result, the migration resistance of lithium ion between the cathode and anode would be increased, leading the fading of capacity and potential.     

TiO2-coated SnO2 hollow spheres as anode materials for lithium ion batteries

TiO2-coated SnO2(TCS) hollow spheres,which are new anode materials for lithium ion(Li-ion) batteries,were prepared and characterized with X-ray diffraction(XRD) ,scanning electron microscopy(SEM) ,transmission electron microscopy(TEM) ,cyclic voltammetry(CV) ,and galvanostatic charge/discharge tests.The results obtained from XRD,SEM,and TEM show that TiO2 can be uniformly coated on the surface of SnO2 hollow spheres with the assistance of anionic surfactant.The cyclic voltammograms indicate that both TiO2 a...     

Preparation of tin-oxide nanotubes as anode for Li-ion batteries

The influence of nanostructure on the electrochemical properties of Li-ion battery was investigated. Tin-oxide nanotubes were prepared by combining sol-gel method with polycarbonate template. Scanning electron microscopy and X-ray diffractometry were applied to characterize the obtained material. The electrochemical measurements were conducted on the nanostructured tin-oxides as electrode of Li-ion batteries. The XRD data indicate that the wall of tube is composed of cassiterite crystals of several nanometers. The electrochemical measurements show that the reaction under potential 0.1-0.2 V is possibly related to the tubular structure of the material. It is suggested that the trapping of Li by dangling bonds and defects sites also contributes to the larger irreversible capacity loss in the first discharge.     

Controlled synthesis of uniform ultrafine CuO nanowires as anode material for lithium-ion batteries

A simple solution route is used to synthesize ultrafine Cu(OH)₂ nanowires by restraining the morphology transformation of early formed 1D nanostructure. The obtained ultrafine nanowires can be well preserved at a low temperature structure transformation in solid state. As anode material for lithium-ion batteries, the ultrafine CuO nanowires exhibit high reversible capacity, superior cycling performance and improved rate capability. The improved electrochemical properties of CuO nanowires are ascribed to their ultrafine size which lead to the reduced over-potential, extra reversible reactions at low potentials and improved interface performance between the electrode and electrolyte.     

Effect of lithium or aluminum substitution on the characteristics of graphite for anode of lithium ion batteries

Modification of graphite for anode of lithium ion batteries is investigated. Results of X-ray diffraction shows lithium and aluminum exists as Li compound (CH3COOLi-2H2O) and Al compound (AID3) in the graphite, respectiovely. The Brunauer-Emmer-Teller (BET) surface area of the modified graphite increases. According to the electrochemical measurements of Li/C cell and prototype Li-ion batteries, the Li-doped graphite has large reversible capacity of 312.2 mA·h/g, low irreversible capacity of 52.9 mA·h/g, and high initial coulombic efficiency of 85.51 %. The 063448 size proto-type battery with Li-doped graphite anode has large discharge capacity of 845 mA·h and good cycling performance. The initial charge/discharge characteristic of Al-doped graphite is close to those of undoped graphite, but the prototype battery with Al-doped anode shows the best cycling performance with capacity retention ratio of 94.06% at the 200th cycle.     

Silicon/flake graphite/carbon anode materials prepared with different dispersants by spray-drying method for lithium ion batteries

Silicon/flake graphite/carbon (Si/FG/C) composites were synthesized with different dispersants via spray drying and subsequent pyrolysis, and effects of dispersants on the characteristics of the composites were investigated. The structure and properties of the composites were determined by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results show that samples have silicon/flake graphite/amorphous carbon composite structure, good spherical appearances, and better electrochemical performance than pure nano-Si and FG/C composites. Compared with the Si/FG/C composite using washing powder as dispersant, the Si/FG/C composite using sodium dodecyl benzene sulfonate (SDBS) as dispersant has better electrochemical performance with a reversible capacity of 602.68 mA·h/g, and a capacity retention ratio of 91.58 % after 20 cycles.     

Effects of modification on performance of natural graphite coated by SiO2 for anode of lithium ion batteries

A stable silicon dioxide film was coated on the surface of natural graphite anode by sol-gel method with Si（OCH2CH3）4, and effects of modification on performance of natural graphite were investigated. The structure and properties of graphite samples were determined by X-ray diffi＇actometry（XRD）, scanning electron microscopy（SEM）, energy-dispersive X-ray spectroscopy（EDS） and electrochemical measurements. The modified graphite shows mainly the layer structure, and silicon dioxide film is amorphous. Compared with the pure natural graphite, the modified graphite exhibits the higher specific capacity of 366 mA-h/g. After 40 charge-discharge cycles, the capacity retention ratio of the modified graphite reaches 99.55%, while that of natural graphite is only 83.04%. The results indicate that the surface modification of natural graphite by SiO2 is effective for improving the electrochemical performance of the natural graphite anode for lithium ion batteries.