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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]

We have studied the effect of final annealing temperature on the formation of lithium zinc titanate, its electrical conductivity, and its electrochemical performance. LiZnTiO has been shown to form in a wide range of annealing temperatures, from 673 to 1073 K. Its particle size increases systematically with increasing annealing temperature, whereas its conductivity decreases. The highest electrochemical capacity at low currents is offered by the materials annealed at 773 and 873 K, and the highest cycling stability is offered by the material prepared at 873 K. [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]

Used LiCoO material was renovated by means of ultrasound radiation under hydrothermal conditions. The optimal reaction condition for renovation process was obtained: temperature 120 °C, ultrasonic power 999 W, and ultrasonic method 'work 5 s-stop 2 s' and ultrasonic radiation time 10 h. The XRD, SEM, ICP-AES analysis, and charge-discharge test showed that the renovated LiCoO had a high degree of crystallinity, a fine-layered structure, good dispersion of particles, and improved electrochemical cycle performance. The first-time charge capacity and discharge capacity of renovated LiCoO were 132.6 and 131.5 mAh/g, respectively. The first-time charge and discharge efficiency was 99.2 %. After 20 cycles, the discharge capacity retention rate was 98.1 % which reaches or approaches the electrochemical properties of commercial batteries. [ABSTRACT FROM AUTHOR]

Carbon-coated LiMnSiO powders were synthesized by a citric acid-assisted sol-gel process, and their physical and electrochemical properties were characterized to assess their suitability as a cathode material in lithium-rechargeable batteries. Carbon was coated onto the LiMnSiO particles through the carbonization of polymeric materials that were caused by the addition of citric acid during the sol-gel process. The particle size and electrical conductivity of the LiMnSiO powders were found to be changed by varying the amount of citric acid added during the sol-gel process. XRD analysis showed that the quantity of impurities in LiMnSiO was decreased during the sol-gel process. The carbon coating led to an increase in conductivity and mean particle size by creating an electrical and physical connection between the particles. The discharge capacity of LiMnSiO with over 5 % carbon coating was significantly increased to ~125 mAh g compared to just ~3 mAh g for noncoated material. [ABSTRACT FROM AUTHOR]

Spinel LiMnO and multidoped spinel LiMnCoCrNiFeO were synthesized by the glycine-nitrate method and coated with lithium borosilicate (LBS) in order to enhance the electrochemical performance at room temperature. The structure and electrochemical performance of all samples were characterized by inductively coupled plasma-mass spectrometer (ICP-MS), X-ray diffraction (XRD), differential thermal analysis/thermogravimetry (DTA/TG), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and galvanostatic charge-discharge measurements. The XRD analysis shows that the samples exhibit a pure spinel phase. The SEM results indicated that LBS particles had encapsulated the surface of the undoped and multidoped LiMnO without causing any structural change. The charge-discharge tests showed that LiMnCoCrNiFeO displays better cycling performance than the pristine LiMnO at room temperature. However, in the same conditions, LBS-coated LiMnCoCrNiFeO and LiMn O have better cycling performance than uncoated samples. The results suggest that multidoped and LBS-coated LiMnO could develop into a promising cathode material for lithium ion batteries. [ABSTRACT FROM AUTHOR]

α-MoO nanobelts were synthesized by simple hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cyclic voltammogram (CV) and galvanostatic charge/discharge testing techniques were employed to evaluate electrochemical behaviors of α-MoO materials. Results showed that α-MoO nanobelts with about 80 nm in diameter and 5-12 μm in length were grown in the orthorhombic system. Electrochemical characterisation confirmed that in lithium ion insertion/extraction process, the first intercalation of lithium ion in α-MoO at about 2.8 V was irreversible, corresponding to LiMoO (0 < x ≤ 0.25) and the parent MoO materials coexisting, the second lithium ion inter-calation was reversible at the potential range of 2.2-2.4 V followed by LiMoO (0.25 < x ≤ 0.5), and below 1.0 V the mechanism of lithium ion storage changed from lithium ion intercalation reaction into lithium alloying reaction. The α-MoO nanobelts showed better electrochemical performance, 319 mA h g initial discharge capacity, around 52% capacity retention after 20 cycles than that of α-MoO bulk. [ABSTRACT FROM AUTHOR]

To understand the influence of structure and atom sites on the electrochemical properties of Sn-based anode materials, the lithium intercalation-deintercalation mechanisms into SnNiCu and SnNiCu phases were studied using the first-principle plane wave pseudo-potential method. Calculation results showed that both SnNiCu and SnNiCu were unsuitable anode materials for lithium ion batteries. The Sn-based anode structure related to the number of interstitial sites, theoretical specific capacity, and volume expansion ratio. Different atom sites led to different forces at interstitial sites, resulting in variations in formation energy, density of states, and hybrid orbital types. In order to validate the calculated model, the SnNiCu alloy anode material was synthesized through a chemical reduction-codeposition approach. Experimental results proved that the theoretical design was reasonable. Consequently, when selecting Sn-based alloy anodes, attention should be paid to maximizing the number of interstitial sites and distributing atoms reasonably to minimize forces at these sites and facilitate the intercalation and deintercalation of lithium ion. [ABSTRACT FROM AUTHOR]

Nanoporous Si was obtained by means of metal-assisted chemical etching. Li ion insertion-extraction was tested by voltammetric and galvanostatic electrochemical cycling in conventional 1 M LiPF ethylene carbonate/dimethyl carbonate EC/DMC and in 1 M LiTFSI 1-butyl-1-methyl-pyrrolidinium bis (trifluoromethyl) sulfonylimide [BMP] [TFSI] electrolytes. The nanoporous Si demonstrated high reversibility when cycled in 1 M LiPF EC/DMC electrolyte and showed superior activity compared to the non-structured sample. In contrast to the organic carbonate electrolyte, the material cycling in ionic liquid media showed reduced capacity and reversibility of the Li ion exchange. The latter results were discussed in terms of the high viscosity of the ionic liquid and ineffective cathodic passivation of the Si substrate in the ionic liquid-based electrolyte. Scanning electron microscopy imaging showed minor morphological changes due to the large volume change during Li insertion. No signs of crack formation and propagation were detected during the time span of the measurement. [ABSTRACT FROM AUTHOR]

First-principles prediction of enhancement in the electrochemical potential of LiCoO with aluminum substitution has been realized through earlier experiments. For safer and less expensive Li-ion batteries, it is desirable to have a similar enhancement for alternative cathode materials, LiFePO and LiCoPO. Here, we present first-principles density functional theory based analysis of the effects of aluminum substitution on electrochemical potential of LiCoO, LiFePO and LiCoPO. While Al substitution for transition metal results in increase in electrochemical potential of LiCoO, it leads to reduction in LiFePO and LiCoPO. Through comparative topological analysis of charge density of these materials, we identify a ratio of Bader charges that correlates with electrochemical potential and determine the chemical origin of these contrasting effects: while electronic charge from lithium is transferred largely to oxygen in LiCoO, it gets shared by the oxygen and Co/Fe in olivine phosphates due to strong covalency between O and Co/Fe. Our work shows that covalency of transition metal-oxygen bond plays a key role in determining battery potential. [ABSTRACT FROM AUTHOR]

In the present work, the electrochemical behaviour of LiFePO4/C electrode has been reported. Specially, the electrochemical impedance spectroscopies (EIS) have been studied in detail. The discharge capacity is more than 120 mAh/g. There are two semicircles being found in the Nyquist plot for the cycled electrode and one semicircle for the as-prepared electrode. It is found that the interface capacitance is in an order of magnitude of 10 μF/cm for the high-frequency semicircle, while for the second semicircle the interface capacitance is 5.3~45.4 × 10 μF/cm. It could be concluded that the high-frequency semicircle is to correspond to the charge transfer process. The function of the carbon layer is also briefly discussed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

LiFePO (LFP) nanobars, microplates and nanorods have been selectively synthesized via a solvothermal method in a water-ethylene glycol (EG) binary solvent with HPO, LiOH·HO, and FeSO·7HO as starting materials. The morphology and size of the as-obtained LFP products can be deliberately controlled by varying the volume ratio of EG to water. The formation mechanism and electrochemical properties of different LFP morphologies have been investigated. With carbon coating, the Li-ion diffusion coefficients of LFP nanorods, nanobars and micro-plates are 2.58×10, 2.91×10, and 7.22×10 cm s, respectively. For the carbon-coated nanorods, excellent rate capability and cyclability were attained. At 5 C, the capacity was 141 mAh g for the first cycle and maintained 120 mAh g after 100 cycles; at 10 C, the capacity was still as high as 132 mAh g. [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]

This paper reported on a new gel polymer electrolyte (GPE) based on polyethylene (PE) non-woven fabric supported poly(acrylonitrile-vinyl acetate) (P(AN-VAc)/PE) membrane for lithium ion battery use. The preparation and performances of the P(AN-VAc)/PE membrane and its GPE based on 1 M LiPF in dimethyl carbonate/diethylene carbonate/ethylene carbonate (1:1:1 in volume) were investigated with a comparison of the unsupported P(AN-VAc) membrane. It is found that the P(AN-VAc)/PE membrane shows better mechanical strength and pore structure for electrolyte uptake than the P(AN-VAc) membrane, and subsequently the GPE based on P(AN-VAc)/PE exhibits higher ionic conductivity and electrochemical stability on cathode than the GPE based on P(AN-VAc). With the support of the non-woven fabric, the ionic conductivity of the GPE at room temperature increases from 1.4 to 3.8 mS cm, the oxidation decomposition potential of the GPE on a stainless steel is improved from 5.0 to 5.6 V (vs. Li/Li). The mesocarbon microbeads (MCMB)/LiMnO battery using P(AN-VAc)/PE as separator retains 94% of its initial discharge capacity after 100 cycles at C/2 rate, showing that the P(AN-VAc)/PE membrane is a possible alternative to the expensive separator for current liquid lithium ion battery. [ABSTRACT FROM AUTHOR]

The electronic structure and electrochemical parameters of ternary NiSn0.5Ti0.5 phase are investigated by plane-wave pseudopotential method of the first-principle. The interstitial sites are firstly filled with lithium atoms, and then the substitution for Ni sites occurs. The results show that the Fermi level of lithium-intercalated phase goes up with the increasing lithium concentration. These interactions of M-M covalent bonds (M=Ni, Sn, Ti) become weak, while Li-M bonds are found to increase. NiSn0.5Ti0.5 phase is characterized with high theoretical capacity and low voltage of lithium-intercalation. The obvious volume effect from 77.15% to 189.94% would lead to the failure of the electrode material, and therefore the NiSn0.5Ti0.5 compound should be limited as low as possible in multi-element Sn-based alloy. [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]

Co-substituted α-Ni(OH)2 was synthesized by a novel microwave homogeneous precipitation method in the presence of urea. LiNi0.8Co0.2O2 cathode material was synthesized by calcining Co-substituted α-Ni(OH)2 precursor and LiOH·H2O at 900°C for 10 h in flowing oxygen. XRD, FTIR, FESEM and electrochemical tests were used to study the physical and the electrochemical performances of the materials. The results show that the prepared LiNi0.8Co0.2O2 compound has a good layered hexagonal structure. Moreover, the LiNi0.8Co0.2O2 cathode material demonstrates stable cyclability with a high initial specific discharge capacity of 183.9 mAh/g. The good electrochemical performance could be attributed to the uniform distribution of Ni2+ and Co2+ ions in the crystal structure and a minimal cation mixing in LiNi0.8Co0.2O2 host structure. [ABSTRACT FROM AUTHOR]

Aluminum (Al) foil is widely used as a current collector in lithium ion batteries, EDLCs and other electrochemical devices, and its electrochemical behavior in electrolytes has great effect on the cycle performances and safety of the electrochemical devices. In this work, corrosion behavior of Al foil in 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids and its electrolytes containing LiTFSI as salt were studied using cyclic voltammogram method. It was found that a passive film was firmly formed on the surface of Al foil after the anodic polarization in BMI-BF4 compared to those in EMI-BF4 and PMI-BF4. In addition, anodic polarization research showed that the passive film on Al surface in BMI-TFSI did not well exist. A good passive film formed on the surface of Al foil in BMI-BF4 was not broken down until the potential was up to 94.58 V. Moreover, EDX and XPS analysis showed that F and O exist on the Al surface after the anodic polarization in BMI-BF4, which indicated that a passive film like AlF3 and Al2O3 may be formed on its surface. [ABSTRACT FROM AUTHOR]

The article evaluates the primary electrochemical performance of surface modified spherical graphite in relation to the distribution of conductive additive particles on the coated electrode material. It has been observed that the cycling behavior was influenced by the dispersion of conductive additive. The initial reversible capacity was greater than that of commercial synthetic graphite. Also, poor dispersion produced numerous white deposits.