X-ray study of metal oxide based anodes for Li-ion batteries

Cells were made from Co₃O₄ and Co₂SnO₄ and lithium metal and tested to determine reversible lithium capacity. Li is reversibly inserted into Co₃O₄, as was observed by electrochemistry, coupled with changes of cobalt oxidation state as observed by Co K-edge EXAFS. On lithium insertion the Co₃O₄ is reduced to yield only metallic cobalt species, and then on lithium removal an oxide of Co is formed. The EXAFS data further showed that the initial reduction was to Co(II) and then to metallic Co, and that both the metallic and oxide phases were disordered, having low co-ordination numbers and large shell spacings. The electrochemical behaviour of the Co₂SnO₄ cells was closer to that of SnO₂ than Co₃O₄, but did exhibit changes obviously caused by the cobalt. EXAFS on Co₂SnO₄ cells revealed that the Co is reduced to metallic cobalt on the initial discharge, but does not convert back to an oxide on cycling. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Silica doped tin oxide composite anodes for lithium-ion batteries

Silica doped tin oxide composites prepared by a sol gel method have been studied as negative electrode materials for lithium-ion batteries. The composite powders fired at 500 °C were analysed by means of XRD and SEM and showed that the composite consists of a blend of crystalline and amorphous structure with different particle size distribution. The electrochemical properties of this anode material were examined by charge-discharge measurements and cyclic voltammetry. The silica doped tin oxide composite anode, which was cycled between 0.1 to 2.0 V, showed a reversible capacity of 270 mAh/g. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Li-ion batteries: Phase transition

Progress in the research on phase transitions during Li+extraction/insertion processes in typical battery materials is summarized as examples to illustrate the significance of understanding phase transition phenomena in Li-ion batteries.Physical phenomena such as phase transitions(and resultant phase diagrams) are often observed in Li-ion battery research and already play an important role in promoting Li-ion battery technology. For example, the phase transitions during Li+insertion/extraction are highly relevant to the thermodynamics and kinetics of Li-ion batteries, and even physical characteristics such as specific energy, power density, volume variation, and safety-related properties.     

Operando plasmon-enhanced Raman spectroscopy in silicon anodes for Li-ion battery

Silicon, an attractive candidate for high-energy lithium-ion batteries (LIBs), displays an alloying mechanism with lithium and presents several unique characteristics which make it an interesting scientific topic and also a technological challenge. In situ local probe measurements have been recently developed to understand the lithiation process and propose an effective remedy to the failure mechanisms. One of the most specific techniques, which is able to follow the phase changes in poorly crystallized electrode materials, makes use of Raman spectroscopy within the battery, i.e., in operando mode. Such an approach has been successful but is still limited by the rather signal-to-noise ratio of the spectroscopy. Herein, the operando Raman signal from the silicon anodes is enhanced by plasmonic nanoparticles following the known surface-enhanced Raman spectroscopy (SERS). Coinage metals (Ag and Au) display a surface plasmon resonance in the visible and allow the SERS effect to take place. We have found that the as-prepared materials reach high specific capacities over 1000 mAh/g with stability over more than 1000 cycles at 1C rate and can be suitable to perform as anodes in LIB. Moreover, the incorporation of coinage metals enables SERS to take place specifically on the surface of silicon. Consequently, by using a specially designed Raman cell, it is possible to follow the processes in a silicon-coinage metal-based battery trough operando SERS measurements.     

电动汽车与锂离子电池

文章简要介绍了混合动力汽车、插电式混合动力汽车、纯电动汽车和锂离子动力电池及其关键材料。发展电动汽车可以大幅度降低人们对石油的依赖和改善城市空气质量。锂离子电池性能优越,为电动汽车的发展提供了支撑。近期,新一代锂离子动力电池正极材料即将走向应用,可使电动汽车里程增加一倍,材料选择和电池设计及制造工艺与电池储存能量、寿命、安全等密切相关, 尊道而重德,可做出“好”电池。     

Nanopowders of spinel-type electrode materials for Li-ion batteries

Nanomaterials are becoming important for use in Li-ion battery electrodes as these can deliver increased capacity and improved power performance. Our work is focused on Mg-doped high-voltage spinel materials, such as LiNi_0.5Mn_1.5O₄, in order to improve its stability. LiMg_δNi_0.5−δMn_1.5O₄ with δ = 0.05, having the cubic spinel structure (P4₃32) were made via four different synthesis routes – a solid-state route, a sol–gel method, a xerogel route and an auto ignition method.The powders were investigated with SEM and TEM analysis. XRD was used to determine the crystallographic structure. Electrochemical tests were performed in CR2320 coin cells built with 1 M LiPF₆ in EC/EMC/DMC 1:2:2 as electrolyte and metallic Li as negative electrode – cells were measured with a MACCOR cycler.LiMg_0.05Ni_0.45Mn_1.5O₄ made via the sol–gel and xerogel routes revealed agglomerated nanoparticles with sizes ranging from 10 to 200 nm, whereas the auto ignition method gives particle sizes between 10 and 50 nm. Although agglomerated, often residual LiMn₂O₄ is observed, with increasing concentration going from solid-state, sol–gel, xerogel to auto ignition.Hence, thanks to these different synthesis routes, we are able to obtain particle sizes reaching from 10 to 200 nm, with a narrow particle size distribution. The electrochemical tests of the xerogel particles showed promising results. The auto ignition method show also promising results, however, the impurity phase needs to be suppressed significantly. The sol–gel method, the xerogel route and the auto ignition method show increased capacity retention at high power rates compared to the solid state method.     

Preparation of V-LiFePO4 cathode material for Li-ion batteries

The preparation of vanadium-modified olivine LiFePO₄ was attempted using vanadium-modified FePO₄ precursor which was synthesized by controlled crystallization. The structure and electrochemical behavior of V-LiFePO₄ with different vanadium contents were investigated. The electrochemical behavior of V-LiFePO₄ materials at high rate and low temperature was compared with that of the LiFePO₄ material. Incorporation of vanadium improved the electrochemical performance of LiFePO₄. The investigation showed that the 3%V-modified LiFePO₄ presented the best electrochemical performance.     

Two-dimensional MnN utilized as high-capacity anode for Li-ion batteries

When developing high performance lithium-ion batteries,high capacity is one of the key indicators.In the last decade,the progress of two-dimensional(2 D) materials has provided new opportunities for boosting the storage capacity.Here,based on first-principles calculation method,we predict that MnN monolayer,a recently proposed 2 D nodal-loop halfmetal containing the metallic element Mn,can be used as a super high-capacity lithium-ion batteries anode.Its theoretical capacity is above 1554 mA-h/g,more than four times that of graphite.Meanwhile,it also satisfies other requirements for a good anode material.Specifically,we demonstrate that MnN is mechanically,dynamically,and thermodynamically stable.The configurations before and after lithium adsorption exhibit good electrical conductivity.The study of Li diffusion on its surface reveals a very low diffusion barrier(～ 0.12 eV),indicating excellent rate performance.The calculated average open-circuit voltage of the corresponding half-cell at full charge is also very low(～0.22 V),which facilitates higher operating voltage.In addition,the lattice changes of the material during lithium intercalation are very small(～ 1.2%-～4.8%),which implies good cycling performance.These results suggest that 2 D MnN can be a very promising anode material for lithium-ion batteries.     

Optimized LiVOPO4 for cathodes in Li-ion rechargeable batteries

Improvement of the rate properties of orthorhombic LiVOPO₄ by using a milling approach and acetylene black additives as electronic binder is investigated. The average particle size of orthorhombic LiVOPO₄ was reduced from 12.0 μm to 6.1 μm by milling process by which the Li intercalation capacity into LiVOPO₄ increased to 40 mAhg⁻¹ at 0.4 mAcm⁻² (C/5). At an optimized acetylene black amount of 15 wt.%, a better uniformity in particle size distribution and dispersion of the current distribution was obtained. Thus, enhancing the kinetic performance a fairly large reversible intercalation capacity of Li was achieved with values of 100 and 60 mAhg⁻¹ at high rate conditions of C/5 (0.4 mAcm⁻²) and 1C (2 mAcm⁻²), respectively. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Surface structure evolution of cathode materials for Li-ion batteries

Lithium ion batteries are important electrochemical energy storage devices for consumer electronics and the most promising candidates for electrical/hybrid vehicles. The surface chemistry influences the performance of the batteries significantly. In this short review, the evolution of the surface structure of the cathode materials at different states of the pristine, storage and electrochemical reactions are summarized. The main methods for the surface modification are also introduced.     

SiMn–Graphite composites as anodes for lithium ion batteries

Two Si–Mn–C composites were obtained by sequentially ball milling the mixture of the silicon and manganese powders (atomic ratio of 3:5), followed by addition of 20 wt.% and 10 wt.% graphite, respectively. The phase structure and morphology of the composite were analyzed by X-ray diffraction (XRD) and scanning electromicroscopy (SEM). The results of XRD show that there is no new alloy phase in the composite obtained by mechanical ball milling. SEM micrographs confirm that the particle size of the Si–Mn–C composite is about 0.5–2.0 μm and the addition of graphite restrains the morphological change of active center (Si) during cycling. The Si–Mn particles are dispersed among the carbon matrix homogeneously, which ensures a good electrical contact between the active particles. Electrochemical tests show that the Si–Mn–C composite achieves better reversible capacity and cycleability. The Si–Mn–20 wt.% C composite electrode annealed at 200 °C for 2 h reveals an initial reversible capacity of 463 mAh·g^− 1 and retains 387 mAh·g^− 1 after 40 cycles.     

Nanoflake CoN as a high capacity anode for Li-ion batteries

CoN films with nanoflake morphology are prepared by RF magnetron sputtering on Cu and oxidized Si substrates and characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) techniques. The thickness and composition of the films are determined by the Rutherford back scattering (RBS) technique confirming the stoichiometric composition of CoN with a thickness, 200 (± 10) nm. Li-storage and cycling behavior of nanoflake CoN have been evaluated by galvanostatic discharge–charge cycling and cyclic voltammetry (CV) in cells with Li–metal as counter electrode in the range of 0.005–3.0 V at ambient temperature. Results show that a first-cycle reversible capacity of 760 (± 10) mAhg^? 1 at a current rate 250 mAg^? 1(0.33 C) increases consistently to yield a capacity of 990 (± 10) mAhg^? 1 after 80 cycles. The latter value corresponds to 2.7 mol of cyclable Li/mol of CoN vs. the theoretical, 3.0 mol of Li. Very good rate capability is shown when cycled at 0.59 C (up to 80 cycles) and at 6.6 C (up to 50 cycles). The coloumbic efficiency is found to be 96–98% in the range of 10–80 cycles. The average charge and discharge potentials are 0.7 and 0.2 V, respectively for the decomposition/formation of Li₃N as determined by CV. However, cycling to an upper cut-off voltage of 3.0 V is essential for the completion of the “conversion reaction”. Based on the ex-situ-XRD, -HR-TEM and -SAED data, the plausible Li-cycling mechanism is discussed. The results show that nanoflake CoN film is a prospective anode material for Li-ion batteries.     

Synthesis of nanosized Si composite anode material for Li-ion batteries

A simple method was proposed to prepare nanosized Si composite anode materials for lithium-ion (Li-ion) batteries. The preparation started with the shock-type ball milling of silicon in liquid media of polyacrylonitrile (PAN)/dimethylformamide (DMF) solution, forming slurry where the nano-Si particles were uniformly dispersed, followed by the drying of the slurry to remove DMF. The nanosized Si composite anode material was obtained after the pyrolysis of the mixture at 300 °C where the pyrolyzed PAN provided a conductive matrix to relieve the morphological change of Si during cycling. As-prepared composite presented good cyclability for lithium storage. The proposed process paves an effective way to prepare high performance Si, Sn, Sb and their alloys based composite anode materials for Li-ion batteries.     

Combined operando studies of new electrode materials for Li-ion batteries

The performances of Li-ion batteries depend on many factors amongst which the important ones are the electrode materials and their structural and electronic evolution upon cycling. For a better understanding of lithium reactivity mechanism of many materials the combination of X-Ray Powder Diffraction (XRPD) and Transmission Mössbauer Spectroscopy (TMS) providing both structural and electronic information during the electrochemical cycling has been carried out. Thanks to the design of a specific electrochemical cell, derived from a conventional Swagelock cell, such measurements have been realised in operando mode. Two examples illustrate the greatness of combining XRPD and TMS for the study of LiFe_0.75Mn_0.25PO₄ as positive electrode and TiSnSb as negative electrode. Different kinds of insertion or conversion reactions have been identified leading to a better optimization and design of performing electrodes.     

Neutron radiation on tin anodes of lithium-ion batteries

Abstract

The operating durability of lithium-ion batteries is a principal problem in universe exploration or rescuing work in the nuclear radiation area. In the study, the neutron irradiation experiments were conducted on film-tin electrodes using the radiation dose of 10¹¹, 10¹², 10¹³ and 10¹⁴?n?cm^?2, respectively. The results show that the particle size grows with the increasing radiation does by atomic force microscopy (AFM) and scanning electron microscope (SEM). In addition, the degressive trend of specific capacity of tin anodes after neutron radiations increases with the increasing radiation dose. The fade of electrochemical performances may be attributed to the increasing particle size and defects induced by neutron radiation.     

Li2MnSiO4/carbon nanofiber cathodes for Li-ion batteries

Pure single-phase Li₂MnSiO₄ nanoparticle-embedded carbon nanofibers have been prepared for the first time via a simple sol-gel and electrospinning technique. They exhibit an improved electrochemical performance over conventional carbon-coated Li₂MnSiO₄ nanoparticle electrodes, including a high discharge capacity of ～200 mAh g^?1, at a C/20 rate, with the retention of 77 % over 20 cycles and a 1.6-fold higher discharge capacity at a 1 C rate.     

Structural transitions in positive electrodes for Li-ion batteries the vibronic approach

We present the vibrational properties of manganese dioxides and lithiated oxides with either spinel-type and layered-type structure used as positive electrodes in Li-ion batteries. The local structure in γ-MnO₂ is investigated as a function of the intergrowth rate, Pr, of pyrolusite in the ramsdellite matrix and the phase evolution as a function of the degree of intercalation or deintercalation in 4-volt electrode materials Li_1−xCoO₂ and Li_1−xMn₂O₄. Lattice dynamics are studied using either a classical group theoretical analysis or a local environment model. Raman and FTIR bands are identified on the basis of vibrational modes of polyhedral units which are building the structure. Structural modifications induced by intercalation-deintercalation process are examined. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Preparation of P(AN-MMA) gel electrolyte for Li-ion batteries

Phase inversion technique was used to prepare poly(acrylonitrile-methyl methacrylate) [P(AN-MMA)]-based microporous gel electrolyte with addition of SiO₂ via in-situ composition for Li-ion batteries. The P(AN-MMA) was synthesized by emulsion polymerization and was dissolved into N,N-dimethylformamide (DMF) to form a uniform solution, while tetraethyl orthosilicate (TEOS) was added into the solution and was hydrolyzed by catalysis of alkali ammonia solution to form SiO₂. Then the solution was cast onto a glass plate using a doctor blade and exposed to humidified atmosphere produced by ultrasonic humidifier, followed by washing, rinsing, and drying, successively. The gel electrolyte was obtained by putting the P(AN-MMA) microporous membrane in a liquid electrolyte. The gelled microporous membrane sucked with 755 wt% of liquid electrolyte vs the dried membrane. It had a porosity of 70%, about 1∼5 μm of pores, and presented an ionic conductivity of 0.94 × 10⁻³ S/cm at room temperature. Electrochemical stability window of the porous gel polymer electrolyte was determined by running a linear sweep voltammetry. The decomposition voltage of the polymer electrolyte exceeds 4.5 V vs Li. The coin test cell with the microporous gel electrolyte showed a good cycling performance. The discharge capacity retention was above 87% at 0.1 C for 45 cycles.     

Physics of electron and lithium-ion transport in electrode materials for Li-ion batteries

The physics of ionic and electrical conduction at electrode materials of lithium-ion batteries(LIBs) are briefly summarized here, besides, we review the current research on ionic and electrical conduction in electrode material incorporating experimental and simulation studies. Commercial LIBs have been widely used in portable electronic devices and are now developed for large-scale applications in hybrid electric vehicles(HEV) and stationary distributed power stations. However,due to the physical limits of the materials, the overall performance of today's LIBs does not meet all the requirements for future applications, and the transport problem has been one of the main barriers to further improvement. The electron and Li-ion transport behaviors are important in determining the rate capacity of LIBs.     

Review of 5-V electrodes for Li-ion batteries: status and trends

Lithium-ion batteries have dominated the battery industry for the past several years in portable electronic devices due to their high volumetric and gravimetric energy densities. The success of these batteries in small-scale applications translates to large-scale applications, with an important impact in the future of the environment by improving energy efficiency and reduction of pollution. We present the progress that allows several lithium-intercalation compounds to become the active cathode element of a new generation of Li-ion batteries, namely the 5-V cathodes, which are promising to improve the technology of energy storage and electric transportation, and address the replacement of gasoline engine by meeting the increasing demand for green energy power sources. The compounds considered here include spinel LiNi_0.5Mn_1.5O₄ and its related doped-structures, olivine LiCoPO₄, inverse spinel LiNiVO₄ and fluorophosphate Li₂CoPO₄F. LiNi_0.5Mn_1.5O₄ thin films, nanoscale prepared materials and surface-modified cathode particles are also considered. Emphasis is placed on the quality control that is needed to guarantee the reliability and the optimum electrochemical performance of these materials as the active cathode element of Li-ion batteries. The route to increase the performance of Li-ion batteries with the other members of the family is also discussed.