Multi-shelled porous LiNi0.5Mn1.5O4 microspheres as a 5 V cathode material for lithium-ion batteries

Multi-shelled porous LiNi_0.5Mn_1.5O₄ microspheres have been successfully synthesized by a co-precipitation approach combined with high-temperature calcinations. The compositions and structures of multi-shelled LiNi_0.5Mn_1.5O₄ microspheres have been investigated by a variety of characterization methods. The LiNi_0.5Mn_1.5O₄ microspheres are composed of a lot of concentric circular porous shells with constant O, Mn, and Ni concentration, which is ascribed to the fast outward diffusion of Mn and Ni atoms and the slow inward diffusion of O and Li atoms during the calcination process. Electrochemical measurements show that LiNi_0.5Mn_1.5O₄ microspheres deliver good cycling stability and rate capability with discharge capacities of 137.1 (0.1 C), 133.9 (0.2 C), 124.2 (0.5 C), 114.9 (1 C), and 96.0 mAh g⁻¹ (2 C). The LiNi_0.5Mn_1.5O₄ microspheres synthesized by the facile method may be a promising cathode candidate for high energy density lithium-ion batteries.     

Structure and electrochemical performance of Fe3O4/graphene nanocomposite as anode material for lithium-ion batteries

Using hydrothermal method, Fe₃O₄/graphene nanocomposite is prepared by synthesizing Fe₃O₄ particles in graphene. The synthesized Fe₃O₄ is nano-sized sphere particles (100–200 nm) and uniformly distributed on the planes of graphene. Fe₃O₄/graphene nanocomposite as anode material for lithium ion batteries shows high reversible specific capacity of 771 mAh g⁻¹ at 50th cycle and good rate capability. The excellent electrochemical performance of the nanocomposite can be attributed to the high surface area and good electronic conductivity of graphene. Due to the high surface area, graphene can prevent Fe₃O₄ nanoparticles from aggregating and provide enough space to buffer the volume change during the Li insertion/extraction processes in Fe₃O₄ nanoparticles.     

Microwave homogeneous synthesis of porous nanowire Co3O4 arrays with high capacity and rate capability for lithium ion batteries

In this paper, an efficient microwave-assisted homogeneous synthesis approach by urea hydrolysis is used to synthesize cobalt-basic-carbonate compounds. The dimensions and morphology of the synthesized precursor compounds are tailored by changes in the incorporated anions (CO₃²⁻ and OH⁻) under different conditions of temperature and time under microwave irradiation. The wire-like cobalt-basic-carbonate compound self-assembles into one-dimensional porous arrays of Co₃O₄ nanowires constructed of interconnected Co₃O₄ nanocrystals along the [1 1 0] axis after thermal decomposition at 350 °C. The textural characteristics of the Co₃O₄ products have strong positive effects on their electrochemical properties as electrode materials in lithium-ion batteries. The obtained porous nanowire Co₃O₄ arrays exhibit excellent capacity retention and rate capability at higher current rates, and their reversible capacity of 600 mAh g⁻¹ can be maintained after 100 cycles at the high current rate of 400 mA g⁻¹.     

CTAB-assisted sol-gel synthesis of Li4Ti5O12 and its performance as anode material for Li-ion batteries

A simple CTAB-assisted sol-gel technique for synthesizing nano-sized Li₄Ti₅O₁₂ with promising electrochemical performance as anode material for lithium ion battery is reported. The structural and morphological properties are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrochemical performance of both samples (with and without CTAB) calcined at 800 °C is evaluated using Swagelok™ cells by galvanostatic charge/discharge cycling at room temperature. The XRD pattern for sample prepared in presence of CTAB and calcined at 800 °C shows high-purity cubic-spinel Li₄Ti₅O₁₂ phase (JCPDS # 26-1198). Nanosized-Li₄Ti₅O₁₂ calcined at 800 °C in presence of CTAB exhibits promising cycling performance with initial discharge capacity of 174 mAh g⁻¹ (∼100% of theoretical capacity) and sustains a capacity value of 164 mAh g⁻¹ beyond 30 cycles. By contrast, the sample prepared in absence of CTAB under identical reaction conditions exhibits initial discharge capacity of 140 mAh g⁻¹ (80% of theoretical capacity) that fades to 110 mAh g⁻¹ after 30 cycles.     

Effect of heat treatment on the morphology and electrochemical performance of TiO2 nanotubes as anode materials for lithium-ion batteries

Lepidocrocite TiO₂ nanotubes prepared by hydrothermal process were annealed at 300 °C and 500 °C for 1 h in air. The morphologies, structures and electrochemical performances of these TiO₂ nanomaterials were investigated by transmission electron microscope, X-ray diffraction and a variety of electrochemical testing techniques. The results showed that the TiO₂ nanotubes gradually collapsed during heating period, and were finally transformed into anatase TiO₂ nanorods. The electrochemical measurements revealed that all the TiO₂ electrodes exhibit a good cycling performance when were used as the anode materials for lithium-ion batteries. Compared with the original TiO₂ nanotubes, the 500 °C annealed TiO₂ nanomaterial electrode provided a higher first coulombic efficiency and higher lithium-ion transfer rate, implying a promising anode candidate for lithium-ion batteries.     

Electrochemical properties of facile emulsified LiV3O8 materials

LiV₃O₈ cathode materials are post-treated by a special emulsion method (termed “EM”) and then calcinated at different temperatures. The experimental results show that the structure of these oxides is different from LiV₃O₈ prepared by the solid-state reaction (acronym “STATE”) route, although their starting materials are identical. The EM product prepared at 500 °C exhibits a better electrochemical behavior than its counterpart prepared by traditional methods (STATE) or by EM at other temperatures. Its initial discharge capacity is 305 mAh g⁻¹, and it still maintains 250.2 mAh g⁻¹ after 100 cycles at 0.2 C at the voltage range of 1.8–4.0 V vs. Li/Li⁺.     

Synthesis and electrochemical properties of nanorod-shaped LiMn1.5Ni0.5O4 cathode materials for lithium-ion batteries

Nanorod-shaped LiMn_1.5Ni_0.5O₄ cathode powders were synthesized by a co-precipitation method with oxalic acid. Their structures and electrochemical properties were characterized by SEM, XRD and galvanostatic charge-discharge tests. The resulting nanorod-shaped LiMn_1.5Ni_0.5O₄ cathode active materials delivered a specific discharge capacity of 126 mAh g⁻¹ at 0.1 C rate. These active materials exhibited better capacity retention and higher rate performance than those of LiMn_1.5Ni_0.5O₄ cathode powders with irregular morphology.     

Low temperature synthesis of Fe3O4 nanoparticles and its application in lithium ion batteries

Well dispersed Fe₃O₄ nanoparticles with mean size about 160 nm are synthesized by a simple chemical method at atmosphere pressure. The products are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Raman spectrum. Electrochemical properties of the as-synthesized Fe₃O₄ nanoparticles as anode electrodes of lithium ion batteries are studied by conventional charge/discharge tests, showing initial discharge and charge capacities of 1140 mAh g⁻¹ and 1038 mAh g⁻¹ at a current density of 0.1 mA cm⁻². The charge and discharge capacities of Fe₃O₄ electrode decrease along with the increase of cycle number, arriving at minimum values near the 70th cycle. After that, the discharge and charge capacities of Fe₃O₄ electrode begin to increase along with the increase of cycle number, arriving at 791 and 799 mAh g⁻¹ after 393 cycles. The morphology and size of the electrode after charge and discharge tests are characterized by SEM, which exhibits a large number of dispersive particles with mean size about 150 nm.     

Conductive polyaniline capped Fe2O3 composite anode for high rate lithium ion batteries

A composite of Fe₂O₃ capped by conductive polyaniline (PANI) was synthesized by a facile two-step method through combining homogeneous Fe₂O₃ suspension prepared by a hydrothermal method and in-situ polymerization of aniline. As anode material for lithium ion batteries, the Fe₂O₃/PANI composite manifests very large discharge capacities of 1635 mAh g⁻¹, 1480 mAh g⁻¹ at large currents of 1.0 and 2.0 A g⁻¹ (1C and 2C), respectively, as well as good cycling performance and rate capacity. The enhancement of electrochemical performance is attributed to the improved electrical conductivity and effective ion transportation of the composite electrode, in that, PANI keeps the Fe₂O₃ nanorods uniformly connected and offers conductive contact between the electrolyte and the active electrode materials.     

Silicon nanowire array films as advanced anode materials for lithium-ion batteries

Silicon nanowire array films were prepared by metal catalytic etching method and applied as anode materials for rechargeable lithium-ion batteries. The films completely consisted of silicon nanowires that were single crystals. Aluminum films were plated on the backs of the silicon nanowire films and then annealed in an argon atmosphere to improve electronic contact and conduction. In addition to easy preparation and low cost, the silicon nanowire film electrodes exhibited large lithium storage capacity and good cycling performance. The first discharge and charge capacities were 3653 mAh g⁻¹ and 2409 mAh g⁻¹, respectively, at a rate of 150 mA g⁻¹ between 2 and 0.02 V. A stable reversible capacity of about 1000 mAh g⁻¹ was maintained after 30 cycles. The good properties were ascribed to the silicon nanowires which better accommodated the large volume change during lithium-ion intercalation and de-intercalation.     

Synthesis and electrochemical properties of LiV3O8 phase

Lithium vanadium oxide was synthesized by a new method in which LiOH, V₂O₅ and NH₄OH were used as the starting materials to synthesize a precursor containing Li and V, and then obtain the resulting product by calcining the precursor. The LiV₃O₈ compound prepared by this synthesis method gave a good charge-discharge and cycle performance. A specific capacity of 258 mAh/g is obtained in the range of 1.8−4.0 V in the first cycle and 247 mAh/g in the eighth cycle.     

Electrochemical properties of carbon-coated TiO2 nanotubes as a lithium battery anode material

To use as an anode material of lithium batteries, carbon-coated TiO₂ nanotubes are prepared by hydrothermal reaction of rutile particles, subsequent sol–gel mixing with poly(vinyl pyrrolidone), and heat treatment at 300–500 °C. The carbon-coated TiO₂ nanotubes are also characterized by morphology observation, crystalline property analysis, potentiostatic redox behaviors, and galvanostatic discharge–charge evaluations at low and high rates. When annealed at 300 °C, the amorphous phase of carbon layers which are covered on the TiO₂ nanotubes dominates the anatase TiO₂ nanocrystalline phase. When annealed at 500 °C, the carbon-coated TiO₂ nanotubes exhibit superior cyclic performance and high-rate capability, due to the crystalline phase in the carbon-coated layer formed by annealing at high temperature.     

Synthesis and electrochemical performance of LiV3O8/carbon nanosheet composite as cathode material for lithium-ion batteries

To improve the rate capability and cyclability of LiV₃O₈ cathode for Li-ion batteries, LiV₃O₈ was modified by forming LiV₃O₈/carbon nanosheet composite. The LiV₃O₈/carbon nanosheet composite was successfully achieved via a hydrothermal route followed by a carbon coating process. The morphology and structural properties of the samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). TEM observations demonstrated that LiV₃O₈/carbon composite has a very flat sheet-like morphology, with each nanosheet having a smooth surface and a typical length of 400-700 nm, width of 200-350 nm, and thickness of 10-50 nm. Each sheet was surrounded by a thick layer of amorphous carbon. Electrochemical tests showed that the LiV₃O₈/carbon composite cathode features long-term cycling stability (194 mAh g⁻¹ at 0.2 C after 100 cycles) and excellent rate capability (110 mAh g⁻¹ at 5 C, 104 mAh g⁻¹ at 10 C, and 82 mAh g⁻¹ at 20 C after 250 cycles). Electrochemical impedance spectra (EIS) indicated that the LiV₃O₈/carbon composite electrode has very low charge-transfer resistance compared with pristine LiV₃O₈, indicating the enhanced ionic conductivity of the LiV₃O₈/carbon composite. The enhanced cycling stability is attributed to the fact that the LiV₃O₈/carbon composite can prevent the aggregation of active materials, accommodate the large volume variation, and maintain good electronic contact.     

Li3SbO4: A new high rate anode material for lithium-ion batteries

Electrochemical properties of Li₃SbO₄ have been investigated as an anode in lithium-ion coin cells. X-ray powder diffraction of the material, synthesized by the conventional solid state technique with thermal treatment at 800 °C in air, confirmed a monoclinic structure with lattice parameters of a = 5.159 Å, b = 6.048 Å, c = 5.144 Å and β = 109°. Electrochemical measurements in 2032 type coin cells show that Li insertion and extraction in this material take place at 0.72 and 1.05 V vs Li/Li⁺ respectively. Although the material shows a low average reversible capacity of 81 mAhg⁻¹ at a current density of 0.05 mAcm⁻² (C/5), an excellent rate performance with nearly 100% Coulombic efficiency has been observed. Continuous cycling up to 200 cycles at current densities of 0.05, 4.0 and 8.0 mAcm⁻² shows that by increasing the current rate from C/5 to 43 C i.e. 215 times, the average reversible capacity decreases only 10%. Thus, the material might be very useful for applications requiring high rate of charge and discharge.     

Layer-by-layer assembly synthesis of ZnO/SnO2 composite nanowire arrays as high-performance anode for lithium-ion batteries

A layer-by-layer approach has been developed to synthesize ZnO/SnO₂ composite nanowire arrays on copper substrate. ZnO nanowire arrays have been first prepared on copper substrate through seed-assisted method, and then, the surface of ZnO nanowires have been modified by the polyelectrolyte. After oxidation-reduction reaction, SnO₂ layer has been deposited onto the surface of ZnO nanowires. The as-synthesized ZnO/SnO₂ composite nanowire arrays have been applied as anode for lithium-ion batteries, which show high reversible capacity and good cycling stability compared to pure ZnO nanowire arrays and SnO₂ nanoparticles. It is believed that the improved performance may be attributed to the high capacity of SnO₂ and the good cycling stability of the array structure on current collector.     

Controllable synthesis of monodisperse Mn3O4 and Mn2O3 nanostructures via a solvothermal route

A facile one-step solvothermal route was developed to synthesize monodisperse Mn₃O₄ and Mn₂O₃ nanostructures with the introduction of poly(vinyl-pyrrolidone)/stearic acid (PVP/SA) mixture. H₂O₂ played a key role in the determination of the products Mn₃O₄ and Mn₂O₃. The synthesis parameters for nanostructured MnO_x such as surfactant and reaction time were investigated, along with their influences on morphology and composition. The morphology evolution of the Mn₃O₄ and Mn₂O₃ reveals that the nanostructures formed via two distinct mechanisms of nucleation and growth of nanocrystals.     

Hydrothermal synthesis of Co3O4 with different morphologies and the improvement of lithium storage properties

A simple hydrothermal treatment was developed to synthesize Co₃O₄ powders with different morphologies in mass production by using hexamethylenetetramine (HMT, C₆H₁₂N₄) as a precipitator. By changing the initial HMT concentrations, the prepared Co₃O₄ powders were readily regulated in its morphologies, which varied from microsphere to urchin-like hollow microsphere, and finally to collapsed porous structure. Moreover, the four Co₃O₄ powders with different HMT concentrations had been applied in the negative electrode materials for lithium ion batteries, which exhibited different electrochemical properties. The present research demonstrated that morphology was one of the crucial factors that affected the electrochemical properties of electrodes. The capacity retention of sample with an original Co(NO₃)₂:HMT mole ratio of 1:1 is almost above 94% from the 5th cycle at different current densities of 40 and 60 mA g⁻¹, exhibiting the better long-life stability and favorable electrochemical behaviors due to its higher specific surface area (97.1 m² g⁻¹) and the uniform urchin-like hollow structure.     

Preparation and electrochemical properties of Cr doped LiV3O8 cathode for lithium ion batteries

Chromium was incorporated into lithium trivanadate by an aqueous reaction followed by heating at 100 °C. This Cr doped LiV₃O₈ as a cathode for lithium ion batteries exhibits 269.9 mAh g^− 1 at first discharge cycle and remains 254.8 mAh g^− 1 at cycle 100, with a charge-discharge current density of 150 mA g^− 1 in the voltage range of 1.8-4.0 V. The Cr-LiV₃O₈ cathode show excellent discharge capacity, with the retention of 94.4% after 100 cycles. These result values are higher than previous reports indicating that Cr-LiV₃O₈ prepared by our low temperature synthesis method is a promising cathode material for rechargeable lithium ion batteries. The enhanced discharge capacity and cycle stability of Cr-LiV₃O₈ cathode indicate that chromium atoms promote lithium transfer or intercalation/deintercalation during the electrochemical cycles and improve the electrochemical performances of LiV₃O₈ cathode.     

Preparation of copper-doped LiV3O8 composite by a simple addition of the doping metal as cathode materials for lithium-ion batteries

The copper-doped LiV₃O₈ was first prepared by mixing copper powder with solid-state synthesized LiV₃O₈ in distilled water. The electrochemical performance of the copper-doped LiV₃O₈ was compared with that of the undoped one. It was found that the electrochemical performance of the copper-doped sample is significantly improved, with an initial capacity of 265.0 mAh/g and a stabilized capacity of 227.7 mAh/g after 100 cycles. It indicates that the copper-doped LiV₃O₈ could be easily prepared by a simple addition of the doping metal.     

Synthesis of LiV3O8 by an improved citric acid assisted sol–gel method at low temperature

LiV₃O₈ was synthesized by the normal citric acid assisted sol–gel method and an improved citric acid assisted sol–gel method. The improved method compares with the normal method in detail by thermogravimetry (TG), FTIR, X-ray diffraction (XRD), scanning electron microscopy (SEM), charge–discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Results show that the improved method can synthesize LiV₃O₈ successfully at much lower temperature than normal method.