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.     

Synthesis and characterization of TiO2-coated magnetite clusters (nFe3O4@TiO2) as anode materials for Li-ion batteries

TiO₂-coated magnetite clusters (nFe₃O₄@TiO₂) were facilely prepared through the sol–gel reaction between Ti alkoxides (TEOT) and magnetite clusters (nFe₃O₄) with terminated alkoxy groups. The composite particles represented a core–shell nanostructure (nFe₃O₄@TiO₂) consisting of a Fe₃O₄ cluster core and a TiO₂ capsule layer. The capsule layer of nFe₃O₄@TiO₂ was increased with increasing amounts of TEOT (150, 300, 500 μl) in sol–gel reaction. The Fe₃O₄@TiO₂ (150 μl of TEOT) with a thin TiO₂ layer (ca. 10 nm) exhibited two kinds of cathodic (0.79 V and 1.61 V) and anodic (1.78 and 2.1 V) peaks attributed to the reduction and oxidation process by Fe₃O₄ core and TiO₂ layer, respectively. The thin nFe₃O₄@TiO₂ (150 μl of TEOT) exhibited the enhanced capacity retention by ca. 40% probably due to the buffering effect of TiO₂ capsule layer. However, the thick nFe₃O₄@TiO₂ (300–500 μl of TEOT) exhibited a rapid capacity fading due to the disintegrated core–shell nanostructure, i.e., unfavorable hetero-junction between TiO₂ matrix and magnetite clusters.     

Template-free synthesis of hierarchical NiO microtubes as high performance anode materials for Li-ion batteries

Hierarchical nanostructured NiO (h-NiO) microtubes were prepared by a simple wet-chemical synthesis without the use of template or surfactant, followed by the calcination of α-Ni(OH)₂ precursor. The structural characterization of the h-NiO microtubes were performed by scanning microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), the results of which indicated that the obtained h-NiO microtubes are covered by the nanosheet grown perpendicularly on the tube surface. The unique hierarchical nanostructure of h-NiO microtubes with high surface area and many voids facilitates the electrochemical reaction as well as the short ion and electron transport pathway. Therefore, as anode electrode of Li-ion batteries, the h-NiO microtubes deliver largely enhanced cycle capacity of 770 mAh·g⁻¹ at a current density of 0.5 C after 200 cycles with high columbic efficiency, compared to the NiO rods. These results suggest that the h-NiO microtubes can be a promising anode material for Li-ion batteries.     

Hydrothermal synthesis of spinel Li1+x Mn2O4 as cathode material for rechargeable lithium battery

Abstract

The hydrothermal synthesis of Li-Mn spinel oxide (Li_1+xMn₂O₄) was undertaken in order to develop high quality, low cost cathode material for a rechargeable lithium battery. In our experiments, γ-MnOOH, LiOH · H₂O and H₂O₂ were used as starting materials to synthesize Li-Mn spinel oxide under hydrothermal conditions of 180-230°C and about 1.0-2.8 MPa. The chemical composition and particle size of the Li_1+xMn₂O₄ is easily controlled in the hydrothermal reaction. The Li_1+xMn₂O₄ produced was characterized by X-ray diffraction, with the spinel phase having a Li/Mn ratio of 0.50-0.60. There is convincing evidence, as a result of this work, that our synthesis process is most suitable for producing high quality cathode material that can be used in a rechargeable lithium battery.     

Preparation and characteristics of Li4Ti5O12 with various dopants as anode electrode for hybrid supercapacitor

Spinel-Li₄Ti₅O₁₂ is successfully synthesized by a solid phase synthesis. The Li₄Ti₅O₁₂ powders with various dopants (Al³⁺, Cr³⁺, Mg²⁺) synthesized at 800 °C are in accordance with the Li₄Ti₅O₁₂ cubic spinel phase structure. The dopants are inserted into the lattice structure of Li₄Ti₅O₁₂ without causing any changes in structural characteristics. In order to study the effect on various dopants, the hybrid supercapacitor is prepared by using un-doped Li₄Ti₅O₁₂ and doped Li₄Ti₅O₁₂ in this work. The electrochemical performance of the hybrid supercapacitor is characterized by impedance spectroscopy and cycle performance. The results show Cr³⁺ and Mg²⁺ dopants enhance the conductivity of Li₄Ti₅O₁₂. Also, Al³⁺ substitution improves the reversible capacity and cycling stability of Li₄Ti₅O₁₂. It is found that effect of dopant on the electrochemical performance of Li₄Ti₅O₁₂ as electrode material for hybrid supercapacitor where the EDLC and the Li ion secondary battery coexist in one cell system.     

Li4Ti5O12/Ag composite as electrode materials for lithium-ion battery

The Li₄Ti₅O₁₂/Ag composites were prepared by thermal decomposition of AgNO₃ added to Li₄Ti₅O₁₂ powders. The influence of the Ag contents and the mixing media on the particle size, morphology and electrochemical performance of Li₄Ti₅O₁₂/Ag composites were investigated. The highest discharge capacity of the Li₄Ti₅O₁₂/Ag composite reached at the 5 wt.% of Ag content. Compared with alcohol medium, distilled water as mixing medium presented the Li₄Ti₅O₁₂/Ag composite with higher specific capacity and better cycling performance, leading to a reversible capacity after 50 cycles of 184.2 mAh/g with a capacity degradation of 3.31% compared to the second cycle at 2 C rate.     

Preparation of binder-free thin film Li4Ti5O12 anode with an adjustable thickness through anodic TiO2 nanotubes

Binder-free thickness-controllable Li₄Ti₅O₁₂ for application in lithium ion batteries was fabricated by the reaction of Li₂CO₃ and anodic nanotubular TiO₂ at 800 °C. As the concentration of Li₂CO₃ increased, the thickness of Li₄Ti₅O₁₂ film increased, leading to increase in discharge capacity. The Li₄Ti₅O₁₂ film prepared at the optimized concentration of Li₂CO₃ of 3.8 × 10^?6 mol displayed the maximum capacity of 104 μA h cm^?2 at the first cycle, which corresponds to 103 mA h g^?1. We found that excess Li₂CO₃ led to creation of LiTiO₂ phases in the Li₄Ti₅O₁₂ film, which reduced the discharge capacity. For comparison, a Li₄Ti₅O₁₂ film was prepared by the reaction of Li₂CO₃ on a non-anodized Ti foil. In this case, discharge capacity was dramatically reduced due to the formation of Li₂TiO₃ phases in Li₄Ti₅O₁₂, which was confirmed by TEM and XRD analysis.     

Development and characterization of a novel silicon-based glassy composite as an anode material for Li-ion batteries

A novel silicon-based glassy composite anode material with high initial coulombic efficiency and long cycling performance for lithium-ion batteries was synthesized by a wet mechanochemical reduction method. The in situ formed Si particles with size of 5-10 nm were uniformly distributed in the glassy matrices formed by B₂O₃ and P₂O₅. The as-prepared composite electrode revealed an initial charge and discharge capacity of 432.7 and 514.4 mAh g^− 1, respectively, with an initial coulombic efficiency of 84%. After 100 cycles, the reversible capacity retention rate was still up to 97%, meaning a favorable cycling stability.     

Comparative study of NiSb2 and FeSb2 as negative electrodes for Li-ion batteries

Crystalline FeSb₂ powder prepared by ceramic route is examined as negative electrodes for lithium-ion batteries. The complete reaction mechanism of FeSb₂ is investigated by ¹²¹Sb and ⁵⁷Fe Mössbauer spectroscopy as well as magnetic measurements and the results are correlated with a previous in situ XRD characterization. On the first discharge the reaction with Li proceeds through a biphasic process transforming FeSb₂ into a new Li_xFe_ySb₂ phase, and this ternary phase is then converted into fcc Li₃Sb and metallic Fe nanoparticles. The combination of Mössbauer spectroscopy and magnetic analyses leads i) to a better understanding of the FeSb₂ → ternary phase reaction and concomitantly allowed ii) to specify the stoichiometry of the new ternary phase. On charge, the extrusion of lithium includes the back conversion of the Li₃Sb/Fe mixture into both Li₄Fe_0.5Sb₂ and metallic Sb, which are the main active species for the following cycles, responsible for the poor cycling life of the FeSb₂ electrode. The nature of these resulting products is quite different from that previously observed for the isotype NiSb₂ electrode which is characterized by a highly reversible mechanism.     

Structure and insertion properties of disordered and ordered LiNi0.5Mn1.5O4 spinels prepared by wet chemistry

We present the synthesis, characterization, and electrode behavior of LiNi_0.5Mn_1.5O₄ spinels prepared by the wet-chemical method via citrate precursors. The phase evolution was studied as a function of nickel substitution and upon intercalation and deintercalation of Li ions. Characterization methods include X-ray diffraction, SEM, Raman, Fourier transform infrared, superconducting quantum interference device, and electron spin resonance. The crystal chemistry of LiNi_0.5Mn_1.5O₄ appears to be strongly dependent on the growth conditions. Both normal-like cubic spinel [Fd3m space group (SG)] and ordered spinel (P4 ₁ 32 SG) structures have been formed using different synthesis routes. Raman scattering and infrared features indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Ni, Mn)-O bonds. Scanning electron microscopy (SEM) micrographs show that the particle size of the LiNi_0.5Mn_1.5O₄ powders ranges in the submicronic domain with a narrow grain-size distribution. The substitution of the 3d⁸ metal for Mn in LiNi_0.5Mn_1.5O₄ oxides is beneficial for its charge–discharge cycling performance. For a cut-off voltage of 3.5–4.9 V, the electrochemical capacity of the Li//LiNi_0.5Mn_1.5O₄ cell is ca. 133 mAh/g during the first discharge. Differences and similarities between LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ oxides are discussed.     

Li4Ti2.5Cr2.5O12 as anode material for lithium battery

Chromium-substituted Li₄Ti₅O₁₂ has been investigated as a negative electrode for future lithium batteries. It has been synthesized by a solid-state method followed by quenching leading to a micron-sized material. The minimum formation temperature of Li₄Ti_2.5Cr_2.5O₁₂ was found to be around 600 °C using thermogravimetric and differential thermal analysis. X-ray diffraction, scanning electron microscopy, cyclic voltammetry (CV), impedance spectroscopy, and charge–discharge cycling were used to evaluate the synthesized Li₄Ti_2.5Cr_2.5O₁₂. The particle size of the powder was around 2–4 μm. CV studies reveal a shift in the deintercalation potential by about 40 mV, i.e., from 1.54 V for Li₄Ti₅O₁₂ to 1.5 V for Li₄Ti_2.5Cr_2.5O₁₂. High-rate cyclability was exhibited by Li₄Ti_2.5Cr_2.5O₁₂ (up to 5  C) compared to the parent compound. The conduction mechanism of the compound was examined in terms of the dielectric constant and dissipation factor. The relaxation time has been evaluated and was found to be 0.07 ms. The mobility was found to be 5.133 × 10⁻⁶ cm² V⁻¹ s⁻¹.     

Neutron diffraction and Mössbauer studies of iron substituted Li2Ti3O7 of ramsdellite-type as negative electrode for Li-ion accumulator

In this work we have reported the electrochemical lithiation properties of ramsdellite Li_2.28Ti_3.43O₈, and two new iron-doped ramsdellite phases of compositions Li_2.624Ti_3.088Fe_0.343O₈ and Li_2.28Ti_3.153Fe_0.31O_7.9. In the two iron-doped samples, charge balance is maintained by excess lithium and by oxygen vacancies respectively. The use of neutron diffraction and ⁵⁷Fe Mössbauer spectroscopy is of high interest for studying effect of lithium or vacancies located in the channels of the ramsdellite-type structure. In the case of iron-doped ramsdellite-type phases, all the iron ions are located on octahedral sites and the quadrupole spittings are related to the number of lithium in the neighbourhood of probed atoms. The presence of iron limits the reversible capacity due to the decrease of lithium mobilily through the channels of the ramsdellite-type structure.     

Ultrasound-assisted synthesis of Li-rich mesoporous LiMn2O4 nanospheres for enhancing the electrochemical performance in Li-ion secondary batteries

The hierarchically structured mesoporous LiMn₂O₄ (LMO) nanospheres were synthesized using a template-free self-assembly process that was coupled with ultrasound (U). The ultrasound technique suggested here is very powerful for controlling an ordered nanostructure and improving crystallinity with large single-crystalline domains. Owing to the hierarchical mesoporous structure and high crystallinity, U-LMO provides an excellent rate capability and cycle stability with a capacity retention of more than 98% up to 50 cycles at a 0.2 C rate. Here, we demonstrate that mesoporous U-LMO nanospheres were fabricated to enhance the electrochemical performance and protect it from structurally significant collapsing because of high crystallinity.     

New scheme for dual readout of dose in polycrystalline Li2B4O7 irradiated with synchrotron X-rays from Indus-2

A new thermoluminescent (TL) dosimeter readout scheme was developed which allows for the measurement of both the single incident dose and the accumulated dose from multiple irradiations, through a novel dual readout procedure. Undoped, Mn doped and Cu doped polycrystalline Li₂B₄O₇ pallets were irradiated by synchrotron X-rays from Indus-2 with different dose. Thermoluminescence glow curves were taken at various heating rates. Two glow peaks were observed in each sample. TL intensities of different samples were compared and it was found that TL counts are more in Cu doped Li₂B₄O₇ sample. TL counts under each peak were calculated and a fixed ratio for two peaks was obtained. A new method of reading out the two peaks separately was formalized, allowing for greater flexibility in the use of TL based personnel dose monitoring devices.     

Sonochemical synthesis of LiNi0.5Mn1.5O4 and its electrochemical performance as a cathode material for 5 V Li-ion batteries

LiNi_0.5Mn_1.5O₄ was synthesized as a cathode material for Li-ion batteries by a sonochemical reaction followed by annealing, and was characterized by XRD, SEM, HRTEM and Raman spectroscopy in conjunction with electrochemical measurements. Two samples were prepared by a sonochemical process, one without using glucose (sample-S1) and another with glucose (sample-S2). An initial discharge specific capacity of 130 mA h g⁻¹ is obtained for LiNi_0.5Mn_1.5O₄ at a relatively slow rate of C/10 in galvanostatic charge–discharge cycling. The capacity retention upon 50 cycles at this rate was around 95.4% and 98.9% for sample-S1 and sample-S2, respectively, at 30 °C.     

Facile preparation of SnC2O4 nanowires for anode materials of a Li ion battery

A simple method of creating densely-packed nanostructures of functional metal oxides is attractive, but it has always been a challenge. Here, we synthesize well-distributed nanostructures of Sn complexes (SnC₂O₄ and SnO₂) via a simple chemical anodization technique followed by annealing. Chemical anodization of Sn surface in oxalic acid, using various organic solvents, provides one-dimensional nanostructures of SnC₂O₄. Length and packing density were precisely controlled by several parameters: solubility of oxalic acid, dielectric constant of organic solvents, and the ion transfer of proton and oxalate anion. Further thermal decomposition converts the SnC₂O₄ nanowires into SnO₂ nanowires, maintaining the nanostructure form in the process. In addition, we expect that the mixture of SnC₂O₄ and SnO₂ nanowires synthesized by this approach might be potential alternative anode materials for prompt charging and discharging Li ion batteries.     

Influence of structural defects on the insertion behavior of γ-MnO2: comparison of H and Li

In an attempt to correlate the crystallographic disorder of γ-MnO₂ compounds to their cationic uptake, the influence of their structural defects on their lithium and proton insertion behavior has been studied and compared. The rate of structural defects in the starting γ-MnO₂ compounds strongly modifies both the voltage vs. cation composition profiles (in terms of shape, average voltage of each electrochemical process, polarization and cycled capacity) and the cycling behavior during the first cycles. This work illustrates that the relationships between structure and cation insertion behavior are different for Li and for proton. The study allows to select for better performing samples in terms of maximum cycled capacity: Li insertion is favored by a very small amount of initial disorder (i.e. a low rate of structural defects in starting compound), while proton insertion requires maximum initial disorder (i.e. an intermediate rate of structural defects). Extrapolation of the results demonstrates the interest of Ramsdellite γ-MnO₂ compounds for cathode applications of rechargeable Li batteries.     

Preparation and characterization of (PVP + NaClO4) electrolytes for battery applications

A sodium ion-conducting polymer electrolyte based on polyvinyl pyrrolidone (PVP) complexed with NaClO₄ was prepared using the solution-cast technique. The cathode film of V₂O₅ xerogel modified with polyvinyl pyrrolidone was prepared using the sol-gel method. Investigations were conducted using X-ray diffractometry (XRD), Fourier transformation infrared (FT-IR) spectroscopy. The ionic conductivity and transference number measurements were performed to characterize the polymer electrolyte for battery applications. The transference number data indicated that the conducting species in these electrolytes are the anions. Using the electrolyte, electrochemical cells with a configuration Na/(PVP + NaClO₄)/V₂O₅ modified by (PVP) were fabricated and their discharge profiles studied.     

The effect of S-functionalized and vacancies on V2C MXenes as anode materials for Na-ion and Li-ion batteries

The electrochemical properties of V₂C and V₂CT₂ (T = O, S) MXenes with and without vacancy as anode materials for Na-ion and Li-ion batteries, have been studied using first-principles calculation. The present results indicate that the adsorption strength of Li-ion and Na-ion on V₂CS₂ are less than that of O-functionalized, together with a lower diffusion barrier. Simultaneously, V₂CS₂ monolayer exhibits lower open-circuit voltage (OCV) values of 0.72 and 0.49 V for Li- and Na-ion, respectively. Interestingly, the presence of atomic vanadium vacancy on V₂CS₂ monolayer exerts more prominent effects on enhancing adsorption strength than that of carbon vacancy for Li-ion and Na-ion, but with an exception for the diffusion of Li-ion and Na-ion on V₂CS₂ monolayer. The finding suggests that the V₂CS₂ monolayer is expected to be a potential candidate as anode material for Li-ion and Na-ion battery due to its lower open-circuit voltages and diffusion barriers.     

Synergistic effect of Cr2O3 and Co3O4 nanocomposite electrode for high performance supercapacitor applications

The fabrication of high performance supercapacitor electrodes has been greatly investigated for future high power storage applications. In this present work, chromium oxide-cobalt oxide based nanocomposite (Cr₂O₃–Co₃O₄ NC) was synthesized using the hydrothermal approach. Moreover, the cyclic voltammetry (CV) study reveals the Cr₂O₃–Co₃O₄ NC delivers a high specific capacitance of 619.4 F/g at 10 mV/s. The electrochemical impedance spectra (EIS) of Cr₂O₃–Co₃O₄ NC possess the solution resistance (R_s) and charge transfer resistance (R_ct) of 0.68 Ω and 0.03 Ω respectively. The Galvanostatic charge-discharge (GCD) analysis demonstrated the prolonged charge-discharge time and good rate capability of the Cr₂O₃–Co₃O₄ NC. The cyclic stability of Cr₂O₃–Co₃O₄ NC delivers superior capacitive retention of 83% even after 2000 cycles. The asymmetric supercapacitor (ASC) device based on Cr₂O₃–Co₃O₄//AC yielded an energy density of 4.3 Wh/kg at the corresponding power density of 200 W/kg. Furthermore, the ASC delivers superior cyclic stability of 74.8% even after 1000 consecutive charge-discharge cycles.