A review study on titanium niobium oxide-based composite anodes for Li-ion batteries: Synthesis,structure, and performance

The growing demands for Li-ion batteries (LIBs) in the electrification revolution, require the development of advanced electrode materials. Recently, intercalating titanium niobium oxide (TNO) anode materials with the general formula of TiNb_xO_2+2.5x have received lots of attention as an alternative to graphite and Li₄Ti₅O₁₂ commercial anodes. The desirability of this family of compounds stems from their high theoretical capacities (377–402 mAh/g), high safety, high working voltage, excellent cycling stability, and significant pseudocapacitive behavior. However, the rate performance of TNO-based anodes is poor owing to their low electronic and ionic conductivities. TNO-based composites generally are prepared with two aims of enhancing the conductivity of TNO and achieving a synergic effect between the TNO and the other component of the composite. Compositing with carbon matrices, such as graphene and carbon nanotubes (CNTs) are the most studied strategy for improving the conductivity of TNO and optimizing its high-rate performance. Also, for obtaining anode materials with high capacity and high long-term stability, the composites of TNO with transition metal dichalcogenides (TMDs) materials were proposed in previous literature. In this work, a comprehensive review of the TNO-based composites as the anodes for LIBs is presented which summarizes in detail the main recent literature from their synthesis procedure, optimum synthesis parameters, and the obtained morphology/structure to their electrochemical performance as the LIBs anode. Finally, the research gaps and the future perspective are proposed.     

Unique CNTs-chained Li4Ti5O12 nanoparticles as excellent high rate anode materials for Li-ion capacitors

Composite anode materials with a unique architecture of carbon nanotubes (CNTs)-chained spinel lithium titanate (Li₄Ti₅O₁₂, LTO) nanoparticles are prepared for lithium ion capacitors (LICs). The CNTs networks derived from commercial conductive slurry not only bring out a steric hindrance effect to restrict the growth of Li₄Ti₅O₁₂ particles but greatly enhance the electronic conductivity of the CNTs/LTO composites, both have contributed to the excellent rate capability and cycle stability. The capacity retention at 30 C (1 C = 175 mA g^?1) is as high as 89.7% of that at 0.2 C with a CNTs content of 11 wt%. Meanwhile, there is not any capacity degradation after 500 cycles at 5 C. The LIC assembled with activated carbon (AC) cathode and such a CNTs/LTO composite anode displays excellent energy storage properties, including a high energy density of 35 Wh kg^?1 at 7434 W kg^?1, and a high capacity retention of 87.8% after 2200 cycles at 1 A g^?1. These electrochemical performances outperform the reported data achieved on other LTO anode-based LICs. Considering the facile and scalable preparation process proposed herein, the CNTs/LTO composites can be very potential anode materials for hybrid capacitors towards high power-energy outputs.     

Structural,magnetic and magnetostrictive properties of Co1-xLixFe2O4 synthesized by cathode materials of spent Li-ion batteries

In this study, we investigated the effects of substituting Li⁺ for Co²⁺ at the B sites of the spinel lattice on the structural, magnetic and magnetostrictive properties of cobalt ferrites. The Li⁺ substituted cobalt ferrites, Co_1-xLi_xFe₂O₄, with x varying from 0 to 0.7 in 0.1 increments, were synthesized with a sol-gel auto-combustion method using the cathode materials of spent Li-ion batteries. X-ray diffraction analysis revealed that all the Co_1-xLi_xFe₂O₄ nanopowders had a single-phase spinel structure and the lattice parameters decreased with increasing Li⁺ content, which can be proved by slight shifts towards higher diffraction angle values of the (311) peak. Field emission scanning electron microscopy was used to observe the fractured inner surface of the sintered cylindrical rods and the increased porosity resulted in a decreased magnetostriction. The oxidation states of Co and Fe in the cobalt ferrite samples were examined by X-ray photoelectron spectroscopy. High resolution transmission electron microscopy micrographs showed that most particles were roughly spherical and with sizes of 25–35?nm. Li⁺ substitution had a strong effect on the saturation magnetization and coercivity, which were characterized with a vibrating sample magnetometer. The Curie temperature was reduced due to the decrease in magnetic cations and the weakening of the exchange interactions. The magnetostrictive properties were influenced by the incorporation of Li⁺ at the B sites of the spinel structure and correlated with the changes in porosity, magnetocrystalline anisotropy and the cation distribution.     

电解铜箔产业发展趋势

随着技术的进步,电解铜箔在厚度上迅速向薄、超薄方向发展,THE、RCC、CAC等特殊性能铜箔需求比例快速 增加,以锂离子电池为代表的新应用领域正在形成。     

Synthesis of nano Sb-encapsulated pyrolytic polyacrylonitrile composite for anode material in lithium secondary batteries

A novel process was proposed to synthesize nano Sb-encapsulated pyrolytic polyacrylonitrile composite for anode material in lithium secondary batteries. The preparation started with the dissolution of SbCl₃ and polyacrylonitrile (PAN) in dimethylformamide (DMF) solution, followed by the addition of KBH₄ to reduce Sb³⁺ in the solution. The Sb composite was obtained by pyrolysis of the Sb/PAN mixture that precipitated out when the DMF solution was added by plentiful water. The TEM analysis showed that about 100-200 nm Sb particles were embedded by the pyrolyzed PAN, which provided a conductive matrix to relieve the morphological change of Sb during electrochemical cycling. As-prepared composite presented good cycleability for lithium storage. The proposed process paves an effective way to prepare high performance alloy based composite anode materials for high performance lithium-ion batteries.     

In situ synchrotron X-ray studies on copper-nickel 5 V Mn oxide spinel cathodes for Li-ion batteries

Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the cycle life characteristics of the cathode. Substitution with either metal or a combination of both metals in the spinel lattice structure reduces the 3.9-4.2 V potential plateaus associated with the conversion of Mn³⁺ to Mn⁴⁺. Higher potential plateau associated with oxidation of the substituted transition elements is also observed. These substituents also significantly alter the onset of Jahn-Teller distortions in the 3 V potential plateau. Synchrotron based in situ X-ray absorption (XAS) was used to determine the exact nature of the oxidation state changes in order to explain the overall observed capacities at different potential plateaus. The studies on LiCu_0.5Mn_1.5O₄ show single phase behavior in the 4-5 V potential region with a good cycle life. Lower cycle life characteristic observed in cycling LiNi_0.5Mn_1.5O₄ and LiNi_0.25Cu_0.25Mn_1.5O₄ versus Li metal are ascribed to coexistence of several phases in this potential region. However, LiCu_0.5Mn_1.5O₄ shows onset of Jahn-Teller distortions in the 3 V potential plateau, in contrast to LiNi_0.5Mn_1.5O₄ and LiNi_0.25Cu_0.25Mn_1.5O₄ cathode materials.     

Electrochemical properties of carbon-coated CaWO4 versus Li

Carbon-coated CaWO₄ nano-crystalline phases have been synthesized by ambient temperature solution precipitation method, characterized by X-ray diffraction, SEM and thermogravimetry and their electrochemical properties were studied versus Li metal. Galvanostatic cycling at a current of 60 mA/g in the voltage range 0.005-3.0 V on the 5 wt.% C-coated CaWO₄ gave a reversible capacity of 230 ± 5 mAh/g corresponding to 2.5 mol of Li, which is almost stable from 20 to 50 cycles. Under the same conditions, the 10 wt.% C-coated CaWO₄ showed a capacity of 355 ± 5 mAh/g (3.8 mol of Li) during the initial cycles, but the capacity degraded at a rate of 1.6 mAh/g per cycle in the range 5-100 cycles. A good operating voltage range was found to be 0.005-3.0 V with average discharge and charge potentials being 0.6 and 1.3 V, respectively. Coulombic efficiency in all cases was 96-98%. Cyclic voltammograms compliment the galvanostatic results. Impedance spectral data on the 10 wt.% C-coated CaWO₄ at different voltages during the first and 20th discharge-charge cycle have been interpreted in terms of the variations in the bulk and charge-transfer resistances of the composite electrode. A reaction mechanism involving the formation/decomposition of the oxide bronze, ‘Li_xWO_y’ has been proposed to explain the electrochemical cycling.     

Possible use of methylbenzenes as electrolyte additives for improving the overcharge tolerances of Li-ion batteries

Based on the voltammetric behaviour of a series of methyl-substituted benzenes in 1M LiPF₆/EC-DMC electrolyte, xylene was selected and tested as an electrolyte additive for overcharge protection of Li-ion batteries. From the overcharge curves, CV behaviour and SEM observations of the cells in the presence of xylene, it was found that the additive can polymerize at the overcharged voltage to form a dense layer of isolating polymer film at the cathode surface, which blocks off further oxidation of the electroactive material and electrolyte and, therefore, improves the overcharge tolerance of the Li-ion battery. In addition, the xylene additive has shown only a slight influence on the cycling behaviour.     

Synthesis and electrochemical performance of LiNi0.5Mn1.5O4 spinel compound

Spinel compound LiNi_0.5Mn_1.5O₄ was synthesized by a chemical wet method. Mn(NO₃)₂, Ni(NO₃)₂·6H₂O, NH₄HCO₃ and LiOH·H₂O were used as the starting materials. At first, Mn(NO₃)₂ and Ni(NO₃)₂·6H₂O reacted with NH₄HCO₃ to produce a precursor, then the precursor reacted with LiOH·H₂O to synthesize product LiNi_0.5Mn_1.5O₄. The product showed a single spinel phase under appropriate calcination conditions, and exhibited a high voltage plateau at about 4.6-4.8 V in the charge/discharge process. The LiNi_0.5Mn_1.5O₄ had a discharge specific capacity of 118 mAh/g at about 4.6 V and 126 mAh/g in total in the first cycle at a discharge current density of 2 mA/cm². After 50 cycles, the total discharge capacity was above 118 mAh/g.