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Polypyrrole (PPy) used as popular coatings can improve the electrochemical performance of electrodes greatly; however, uniform coatings of PPy on nanostructures is a challenging task in a solution system. Substitution for liquid phase polymerization reaction, herein a developed evaporation method is reported to make pyrrole vapor in situ polymerization on CuO arrays for the uniform PPy coatings. With the help of this uniform PPy coatings, the unique structure of arrayed CuO film can well maintain the stability of mechanical structures and has rapid transmission of lithium ions and electrons during charge/discharge processes, hence harvesting a high lithium storage. Electrochemical tests indicate that PPy can not only enhance the specific capacities of CuO anodes greatly but also improve the cyclic stability at a high-current density. The specific capacity of the CuO@PPy integrated anode can be up to 561 mAh g−1 at 1 C after 100 cycles, which is increased by almost 33% than that of the pure CuO anode. [ABSTRACT FROM AUTHOR]

The structural and electrochemical effects of electrospun V2O5 with selected redox-inactive dopants (namely Na+, Ba2+ and Al3+) have been studied. The electrospun materials have been characterised via a range of analytical methods including X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area measurements and scanning and transmission electron microscopy. The incorporation of dopants in V2O5 was further studied with computational modelling. Structural analysis suggested that the dopants had been incorporated into the V2O5 structure with changes in crystal orientation and particle size, and variations in the V4+ concentration. Electrochemical investigations using potentiodynamic, galvanostatic and impedance spectroscopy analysis showed that electrochemical performance might be dependent on V4+ concentration, which influenced electronic conductivity. Na+- or Ba2+-doped V2O5 offered improved conductivities and lithium ion diffusion properties, whilst Al3+ doping was shown to be detrimental to these properties. The energetics of dopant incorporation, calculated using atomistic simulations, indicated that Na+ and Ba2+ occupy interstitial positions in the interlayer space, whilst Al3+ is incorporated in V sites and replaces a vanadyl-like (VO)3+ group. Overall, the mode of incorporation of the dopants affects the concentration of oxygen vacancies and V4+ ions in the compounds, and in turn their electrochemical performance.ᅟ [ABSTRACT FROM AUTHOR]

The electrochemical performances of LiMnNiCoO cathode material are enhanced through hydrothermal approach using NaS solution as a medium. Furthermore, the influence of contents of NaS solution on the morphology, structure, and electrochemical performances is fully investigated. The results indicate that a high content of NaS solution results in the formation of spinel particles which are detected by SEM, XRD, and HR-TEM measurements. The formation of spinel particles leads to a deterioration of electrochemical performances. However, a low content of NaS solution results in a slight structure change from layered phase to spinel one near the edge of LiMnNiCoO particles. This slight structure change facilitates the decrease of charge transfer resistance, which contributes to the enhanced rate capability of NaS-treated LiMnNiCoO. [ABSTRACT FROM AUTHOR]

LiZnTiO/C nanocomposite has been synthesized using phenolic resin as carbon source in this work. The structure, morphology, and electrochemical properties of the as-prepared LiZnTiO samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), Raman spectroscopy (RS), galvanostatic charge-discharge, and AC impedance spectroscopy. SEM images show that LiZnTiO/C was agglomerated with a primary particle size of ca. 40 nm. TEM images reveal that a homogeneous carbon layer (ca. 5 nm) formed on the surface of LiZnTiO particles which is favorable to improve the electronic conductivity and inhibit the growth of LiZnTiO during annealing process. The as-prepared LiZnTiO/C composite with 6.0 wt.% carbon exhibited a high initial discharge capacity of 425 and 159 mAh g at 0.05 and 5 A g, respectively. At a high current density of 1 A g, 95.5 % of its initial value is obtained after 100 cycles. [ABSTRACT FROM AUTHOR]

Natural graphite treated by mechanical activation can be directly applied to the preparation of LiV(PO). The carbon-coated LiV(PO) with monoclinic structure was successfully synthesized by using natural graphite as carbon source and reducing agent. The amount of activated graphite is optimized by X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectrum, galvanostatic charge/discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy tests. Our results show that LiV(PO) (LVP)-10G exhibits the highest initial discharge capacity of 189 mAh g at 0.1 C and 162.9 mAh g at 1 C in the voltage range of 3.0-4.8 V. Therefore, natural graphite is a promising carbon source for LVP cathode material in lithium ion batteries. [ABSTRACT FROM AUTHOR]

Olivine LiFePO/C cathode materials for lithium ion batteries were synthesized using monodisperse polystyrene (PS) nano-spheres and other carbon sources. The structure, morphology, and electrochemical performance of LiFePO/C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge tests, electrochemical impedance spectroscopy (EIS) measurements, and Raman spectroscopy measurements. The results demonstrated that LiFePO/C materials have an ordered olivine-type structure with small particle sizes. Electrochemical analyses showed that the LiFePO/C cathode material synthesized from 7 wt.% PS nano-spheres delivers an initial discharge capacity of 167 mAh g (very close to the theoretical capacity of 170 mAh g) at 0.1 C rate cycled between 2.5 and 4.1 V with excellent capacity retention after 50 cycles. According to Raman spectroscopy and EIS analysis, this composite had a lower I/ I, sp/ sp peak ratio, charge transfer resistance, and a higher exchange current density, indicating an improved electrochemical performance, due to the increased proportion of graphite-like carbon formed during pyrolysis of PS nano-spheres, containing functionalized aromatic groups. [ABSTRACT FROM AUTHOR]

A series of Cr-doped LiVCr(PO) ( x = 0, 0.1, 0.25, and 0.5) samples are prepared by a sol-gel method. The effects of Cr doping on the physical and chemical characteristics of LiV(PO) are investigated. Compared with the XRD pattern of the undoped sample, the XRD patterns of the Cr-doped samples have no extra reflections, which indicates that Cr enters the structure of LiV(PO). As indicated by the charge-discharge measurements, the Cr-doped LiVCr(PO) ( x = 0.1, 0.25, and 0.5) samples exhibit lower initial capacities than the undoped sample at the 0.2 C rate. However, both the discharge capacity and cycling performance at high rates (e.g., 1 and 2 C) are enhanced with proper amount of Cr doping ( x = 0.1). The highest discharge capacity and capacity retention at the rates of 1 and 2 C are obtained for LiVCr(PO). The improvement of the electrochemical performance can be attributed to the higher crystal stability and smaller particle size induced by Cr doping. [ABSTRACT FROM AUTHOR]

series of LiNiMnCoO $$ \left( {0 < {2}x \leqslant 0.{33}} \right) $$ compounds were prepared by solid-state reaction from nickel manganese cobalt oxides, and their characteristics were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and charge-discharge test. LiNiMnCoO samples have single phase of layered structure with a space group of $$ {\hbox{R}}\overline 3 {\hbox{m}} $$ for 2 x = 0.02, 0.05, 0.10, 0.20, and 0.33. Both the lattice constants of a- and c-axis and Li/Ni mixing degree decreased with the increase in Co contents in samples. The valence states of Ni, Mn, and Co in the samples are predominantly +2, +4, and 3, respectively, with a small amount of Ni, Mn, and Co. LiNiMnCoO gives excellent cycling performance in the voltage range of 2.5-4.4 V at the current rate of 20 and 100 mA g over 50 cycles. High-rate capacity test of LiNiMnCoO shows that even at a current rate of 1,000 mA g, stable capacity about 63 mAh g is retained. [ABSTRACT FROM AUTHOR]

Monodisperse Li4Ti5O12 hollow spheres were prepared by using carbon spheres as templates. Scanning electron microscopy images show hollow spheres that have an average outer diameter of 1.0 μm and an average wall thickness of 60 nm. Compared with Li4Ti5O12 solids, the hollow spherical Li4Ti5O12 exhibit an excellent rate capability and capacity retention and can be charged/discharged at 10 C (1.7 A g−1) with a specific capacity of 100 mA h g−1, and after 200 charge and discharge cycles at 2 C, their specific capacity remain very stable at 150 mA h g−1. It is believed that the hollow structure has a relatively large contact surface between Li4Ti5O12 and liquid electrolyte, resulting in a better electrochemical performance at high charge/discharge rate. [ABSTRACT FROM AUTHOR]

The olivine-typed cathode materials of LiFePO4were prepared via solid-state reaction under argon atmosphere and co-doped by manganese and fluorine to improve their electrochemical performances. The crystal structure, morphology, and electrochemical properties of the prepared samples were investigated using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, cyclic voltammetry, and charge–discharge cycle measurements. The result showed that the electrochemical performance of LiFePO4 had been improved dramatically by Mn–F co-doping. The initial discharge capacity of LiFe0.99Mn0.01 (PO4)2.99/3F0.01/C samples reached 140.2 mAh/g at 1C rate and only had a small amount of fading in 50 cycles. [ABSTRACT FROM AUTHOR]