Synthesis and electrochemical performance of hole-rich Li4Ti5O12 anode material for lithium-ion secondary batteries

Hole-rich Li₄Ti₅O₁₂ composites are synthesized by spray drying using carbon nanotubes as additives in precursor solution, subsequently followed calcinated at high temperature in air. The structure, morphology, and texture of the as-prepared composites are characterized with XRD, Raman, BET and SEM techniques. The electrochemical properties of the as-prepared composites are investigated systematically by charge/discharge testing, cyclic voltammograms and AC impedance spectroscopy, respectively. In comparison with the pristine Li₄Ti₅O₁₂, the hole-rich Li₄Ti₅O₁₂ induced by carbon nanotubes exhibits superior electrochemical performance, especially at high rates. The obtained excellent electrochemical performances of should be attributed to the hole-rich structure of the materials, which offers more connection-area with the electrolyte, shorter diffusion-path length as well faster migration rate for both Li ions and electrons during the charge/discharge process.     

Enhanced high-rate performance of sub-micro Li4Ti4.95Zn0.05O12 as anode material for lithium-ion batteries

Zn-doped Li₄Ti₅O₁₂ was prepared by a ball milling-assisted solid-state method, and the characters were determined by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, cyclic voltammetry, and galvanostatic charge–discharge testing. The results show that Li₄Ti_5?x Zn _x O₁₂ (x?=?0, 0.05) exhibits the pure phase structure, and Zn doping does not change the electrochemical reaction process and basic spinel structure of Li₄Ti₅O₁₂. The particle size of both samples is about 300–500 nm. The prepared Li₄Ti_4.95Zn_0.05O₁₂ presents an excellent rate capability and capacity retention. At the charge–discharge rate of 1C, the initial discharge capacity of Li₄Ti_4.95Zn_0.05O₁₂ is 268 mAh g^?1. After 90 cycles at 5C, the discharge capacity of Li₄Ti_4.95Zn_0.05O₁₂ is obviously higher than that of Li₄Ti₅O₁₂. The excellent electrochemical performance of the Li₄Ti_4.95Zn_0.05O₁₂ electrode could be attributed to the improvement of reversibility by doping zinc and the sub-micro particle size.     

Nanostructured WO3 thin film as a new anode material for lithium-ion batteries

Nanostructured WO₃ thin film has been successfully fabricated by radio-frequency magnetron sputtering method and its electrochemistry with lithium was investigated for the first time. The reversible discharge capacity of WO₃/Li cells cycled between 0.01 V and 4.0 V was found above 626 mAh/g during the first 60 cycles at the current density 0.02 mA/cm². By using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and selected-area electron diffraction measurements, the reversible conversion of WO₃ into nanosized metal W and Li₂O was revealed. The high reversible capacity and good recyclability of WO₃ electrode made it become a promising cathode material for future rechargeable lithium batteries.     

Synthesis of three-dimensional cross-linked MnO@C composite as high-performance anode material for lithium-ion batteries

MnO@C composites with three-dimensional cross-linked structure were designed and fabricated through hydrothermal treatment. Cation exchange resin was used as the precursor to create a three-dimensional cross-linked porous carbon structure, which was evenly decorated by nanosized MnO particles. When compared with pristine MnO, those MnO@C composites showed much better stability during charge-discharge cycling, retaining a specific capacity of 615 mAh g^?1 (62.5 wt% MnO) after 100 cycles at a current density of 0.2 A g^?1. This could be ascribed to the special three-dimensional cross-linked porous carbon that not only accelerated the transport of Li⁺ ions but also buffered the volume change and prevented agglomeration of MnO particles during the repeated lithiation and delithiation process.     

The effects of Li2CO3 particle size on the properties of lithium titanate as anode material for lithium-ion batteries

Spinel structured Li₄Ti₅O₁₂ was synthesized by a solid-state method using TiO₂ and Li₂CO₃ as starting materials. High-energy ball milling was used to obtain the Li₂CO₃ samples with different particle size. Then, the effects of Li₂CO₃ particle size on the structure, morphology, and electrochemical performance of Li₄Ti₅O₁₂ samples were investigated in detail. The samples were characterized by TG/DTA analysis, X-ray diffraction, scanning electron microscopy and electrochemical tests, respectively. The results indicate that fine Li₂CO₃ particles will promote the interfacial reaction between Li₂CO₃ and TiO₂ in solid-state reaction. The crystallinity and particle size of Li₄Ti₅O₁₂ depend on the particle size of Li₂CO₃. Electrochemical tests show that Li₄Ti₅O₁₂ samples synthesized by fine Li₂CO₃ particles exhibit better rate capacity and cycle performance.     

Nanoporous silicon flakes as anode active material for lithium-ion batteries

Nanoporous-silicon (np-Si) flakes were prepared using a combination of an electrochemical etching process and an ultra-sonication treatment and the electrochemical properties were studied as an anode active material for rechargeable lithium-ion batteries (LIBs). This fabrication method is a simple, reproducible, and cost effective way to make high-performance Si-based anode active materials in LIBs. The anode based on np-Si flakes exhibited a higher performances (lower capacity fade rate, stability and excellent rate capability at high C-rate) than the anode based on Si nanowires. The excellent performance of the np-Si flake anode was attributed to the hollowness (nanoporous structure) of the anode active material, which allowed it to accommodate a large volume change during cycling.     

High-rate Li4Ti5O12/C composites as anode for lithium-ion batteries

The Li₄Ti₅O₁₂/C composites were synthesized by a simple solid-state reaction at 800 °C for 12 h by using Super P® conductive carbon black as carbon source. X-ray diffraction analysis shows that the Li₄Ti₅O₁₂ with 0, 5, 7.5, and 10 wt% carbon shows similar patterns with cubic spinel structure. Scanning electron microscope shows that Li₄Ti₅O₁₂ aggregated seriously, but the aggregation was inhibited by the addition of Super P® carbon. The results indicate that the addition of 5 wt% carbon during sintering and a further 5 wt% carbon during slurry preparation shows the best rate capability of 110 mAh/g when the cells were charge/discharged at 10 C rate. The comparison of the charge–discharge curves shows that the higher rate improvement should further decrease the particle size of LTO or improve the conductivity of LTO itself.     

Electrochemical properties of rutile TiO2 nanorods as anode material for lithium-ion batteries

In this paper, we synthesized rutile TiO₂ nanorods by hydrolysis of TiCl₄ ethanolic solution in water at 50?°C. Scanning electron microscopy and transmission electron microscopy images show that the as-prepared sample was consisted of nanoflowers of about 500?nm in sizes, and each petal of nanoflowers was assembled by several nanorods. We tested the electrochemical properties of the rutile TiO₂ nanorods as an anode material for lithium-ion batteries. The rutile TiO₂ nanorods exhibited a large initial discharge capacity of 223?mA?h?g^?1, and the stabilized capacity was as high as 170?mA?h?g^?1 after 100 cycles. These improved electrochemical performances may be attributed to the shorter diffusion length for both the electron and Li⁺, and the large electrode?Celectrolyte contact area offered by the nanorods with a large specific surface area, which facilitated the lithium ions insertion and extraction.     

Synthesis and electrochemical investigation of highly dispersed ZnO nanoparticles as anode material for lithium-ion batteries

Highly dispersed ZnO nanoparticles were prepared by a versatile and scalable sol-gel synthetic technique. High-resolution transmission electronic microscopy (HRTEM) showed that the as-prepared ZnO nanoparticles are spherical in shape and exhibit a uniform particle size distribution with the average size of about 7 nm. Electrochemical properties of the resulting ZnO were evaluated by galvanostatic discharge/charge cycling as anode for lithium-ion battery. A reversible capacity of 1652 mAh g^?1 was delivered at the initial cycle and a capacity of 318 mAh g^?1 was remained after 100 cycles. Furthermore, the system could deliver a reversible capacity of 229 mAh g^?1 even at a high current density of 1.5 C. This outstanding electrochemical performance could be attributed to the nano-sized features of highly dispersed ZnO particles allowing for the better accommodation of large strains caused by particle expansion/shrinkage along with providing shorter diffusion paths for Li⁺ ions upon insertion/deinsertion.     

A review of research on hematite as anode material for lithium-ion batteries

Hematite (α-Fe₂O₃) nanomaterials have been investigated intensively as a promising anode material for Li-ion batteries due to their advantages such as high theoretical capacity, low cost, environmental friendliness, high resistance to corrosion, etc. However, their practical application is hampered by poor capacity retention, low Coulombic efficiency, and poor high-rate capacity. To overcome these drawbacks, many effective works have been proposed. This review focuses first on the present status of α-Fe₂O₃ nanomaterials in the field of Li-ion batteries including their features, synthesized methods, modification, application and then on their near future development.     

Carbon-coated silicon/crumpled graphene composite as anode material for lithium-ion batteries

Silicon is a promising anode material for high-capacity Li-ion batteries (LIBs). However, its insulating property and large volume change during the lithiation/delithiation process result in poor cycling stability and in pulverization of Si. In this work, glucose-derived carbon-coated Si nanoparticles (C–Si NPs) are in conjunction with crumpled graphene (cGr) particles by a spray-drying method to prepare a novel composite (C–Si/cGr) material. The prepared C–Si NPs are uniformly embedded in the ridges of the cGr particles. The carbon layer of C–Si can make a good contact with the graphene sheet, resulting in enhanced electrical conductivity and fast charge transfer. In addition, the unique crumpled structure of the cGr can buffer the large volume change upon cycling process and facilitate the diffusion of electrolyte into the composite material. When employed as an anode electrode of LIBs, the C–Si/cGr composites deliver enhanced electrochemical performance, including stable cycling with a discharge capacity of 790 mAh·g⁻¹ after 100 cycles and a rate capability of 654 mAh·g⁻¹ at 2C. The synergistic effect of the carbon layer coating of Si NPs and the crumpled structure of the cGr particles results in a composite with improved the electrochemical performance, which is likely related to its high electrical conductivity and good mechanical stability of composite material.     

A novel LiSnVO4 anode material for lithium-ion batteries

Ionics - In this work, a new material LiSnVO4 has been prepared via sol-gel method utilizing ammonium metavanadate, acetates of tin and lithium as starting materials, and nitric acid and oxalic...     

Preparation of Si-PPy-Ag composites and their electrochemical performance as anode for lithium-ion batteries

The nanosilicon connected by polypyrrole (PPy) and silver (Ag) particles was simply synthesized by a chemical polymerization process in order to prepare Si-based anodes for Li-ion batteries. The phase structure, surface morphology, and electrochemical properties of the as-synthesized powders were analyzed by X-ray diffraction, FT-IR, scanning electron microscopy, and galvanostatic charge/discharge measurements. The cycle stability of the Si-PPy-Ag composites was greatly enhanced compared with the pure nanosilicon. A high capacity of more than 823 mA h g^?1 was maintained after 100 cycles. The improved electrochemical characteristics are attributed to the volume buffering effect as well as effective electronic conductivity of the polypyrrole and silver in the composite electrode.     

Hierarchical nanostructure CuO with peach kernel-like morphology as anode material for lithium-ion batteries

Copper oxide particles with different morphology (flower-like, peach kernel-like, and dandelion-like) are prepared with hydrothermal method by adjusting chitosan ((C₆H₁₁NO₄)_n) concentration in aqueous mixed solutions of ammonia and Cu(NO₃)₂. Various morphologies of porous cupric oxide (CuO) particles are formed by agglomerated nanosheet primary particles and lead to different electrochemical performance of electrodes. The peach kernel-shaped CuO exhibits high reversible capacity and rate capability. The reversible capacity is 722.7 mAh g^?1 at 0.1 C in the first cycle and 339 mAh g^?1 after 50 cycles at 0.2, 0.5, 1.0, and 2.0 C ratio. The higher reversible capacities and good cycling performance are attributed to the larger specific surface area, leading to better contact between CuO and electrolyte.     

Enhanced electrochemical performance of La- and Zn-co-doped LiMn2O4 spinel as the cathode material for lithium-ion batteries

We report on the nanoparticle uptake into MCF10A neoT and PC-3 cells using flow cytometry, confocal microscopy, SQUID magnetometry, and transmission electron microscopy. The aim was to evaluate the influence of the nanoparticles?? surface charge on the uptake efficiency. The surface of the superparamagnetic, silica-coated, maghemite nanoparticles was modified using amino functionalization for the positive surface charge (CNPs), and carboxyl functionalization for the negative surface charge (ANPs). The CNPs and ANPs exhibited no significant cytotoxicity in concentrations up to 500???g/cm³ in 24?h. The CNPs, bound to a plasma membrane, were intensely phagocytosed, while the ANPs entered cells through fluid-phase endocytosis in a lower internalization degree. The ANPs and CNPs were shown to be co-localized with a specific lysosomal marker, thus confirming their presence in lysosomes. We showed that tailoring the surface charge of the nanoparticles has a great impact on their internalization.     

Sn and SnO2-graphene composites as anode materials for lithium-ion batteries

Sn and SnO₂-graphene composites were synthesized using hydrothermal process, followed by annealing in Ar/H₂ atmosphere, and characterized using x-ray diffraction, scanning electron microscopy, and transition electron microscopy. The results indicated that the polycrystalline metallic Sn forms nanospheres with a diameter of 100?～?300 nm, while the SnO₂ nanoparticles are much smaller with a size below 15 nm, which adsorb tightly on the surface of graphene sheets. The Sn and SnO₂-gaphene composites showed good electrochemical performance. After 55 charging/discharging cycles, the capacity remains above 440 mAh/g at a cycling rate of 400 mA/g and the coulombic efficiency is 99.1 %. The good electrochemical properties of the composites are partially contributed to the graphene component with good mechanical flexibility and electrical conductivity, which is an excellent carbon matrix for dispersing the Sn and SnO₂ nanostructures and provides the electron transport pathways as well.     

Preparation and electrochemical performance of bramble-like ZnO array as anode materials for lithium-ion batteries

A bramble-like ZnO array with a special three-dimensional (3D) nanostructure was successfully fabricated on Zn foil through a facile two-step hydrothermal process. A possible growth mechanism of the bramble-like ZnO array was proposed. In the first step of hydrothermal process, the crystal nucleus of Zn(OH) ₄ ^2? generated by the zinc atoms and OH^? ions fold together preferentially along the positive polar (0001) to form the needle-like ZnO array. In the second step of hydrothermal process, the crystal nuclei of Zn(OH) ₄ ^2? adjust their posture to keep their c-axes vertical to the perching sites due to the sufficient environmental force and further grow preferentially along the (0001) direction so as to form bramble-like ZnO array. The electrochemical properties of the needle- and bramble-like ZnO arrays as anode materials for lithium-ion batteries were investigated and compared. The results show that the bramble-like ZnO material exhibits much better lithium storage properties than the needle-like ZnO sample. Reasons for the enhanced electrochemical performance of the bramble-like ZnO material were investigated.     

Controllable synthesis of spherical silicon and its performance as an anode for lithium-ion batteries

Spherical silicon is controllably synthesized by the hydrolysis of tetraethylorthosilicate (TEOS) with the addition of different contents of ammonia to form SiO₂, then reduced by magnesium powder in argon atmosphere at 900 °C for 3 h. The experimental results show that the electrochemical performance of the as-prepared silicon anode is much affected by the morphology of silicon, and the spherical silicon with a particle size of 250–300 nm shows a reversible capacity of 1,345.8 mAh g^?1 with the capacity retention of 83.2 % after 20 cycles. The relationship between the electrochemical performance of the spherical silicon and the diameters of silicon sphere makes it possible to control the performance of the silicon anode by adjusting the hydrolysis conditions of TEOS.     

锂离子电池负极材料CuSn的Li嵌入性质的研究

使用基于混合基表示的第一原理赝势法，研究了锂离子电池非碳类负极材料CuSn的Li嵌入时的形成能以及相应的电子结构.还给出了Li嵌入时的体积变化，能带结构、电子态密度以及电荷密度分布等性质, 并讨论了CuSn作为负极材料的特点.计算发现，Cu-Sn化合物在闪锌矿结构时，Li嵌入主体材料时的嵌入形成能大致在3.5eV附近. 关键词： 锂离子电池 负极材料 CuSn 电子结构     

Electrochemical performance of surfactant-processed LiFePO4 as a cathode material for lithium-ion rechargeable batteries

This study focuses on the effect of addition of surfactant as a dispersing agent during vibratory ball milling of LiFePO₄ (LFP) precursor materials on the electrochemical performance of solid-state reaction synthesized LFP for lithium-ion battery cathode material. LFP particles formed after calcinations of ball milled LFP precursors (Li₂CO₃, FeC₂O₄, and NH₄H₂PO₄) showed better size uniformity, morphology control, and reduced particle size when anionic surfactant (Avanel S-150) was used. The specific surface area of LFP particles increased by approximately twofold on addition of surfactant during milling. These particles showed significantly enhanced cyclic performance during charge/discharge due to a reduced polarization of electrode material. Electrodes fabricated from LFP particles by conventional milling process showed a 22 % decrease in capacity after 50 cycles, whereas the performance of electrode prepared by surfactant processed LFP showed only 3 % loss in capacity. The LFP particles were characterized using XRD, FE-SEM, particle size distribution, density measurement, and BET-specific surface area measurement. Electrochemical impedance spectra and galvanostatic charge/discharge test were performed for the electrochemical performance using coin-type cell.