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.     

Enhanced high-rate performance of sub-micro Li4Ti4.95Zn0.05O12 as anode material for lithium-ion batteries

Zn-doped Li₄Ti₅O₁₂ was prepared by a ball milling-assisted solid-state method, and the characters were determined by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, cyclic voltammetry, and galvanostatic charge–discharge testing. The results show that Li₄Ti_5?x Zn _x O₁₂ (x?=?0, 0.05) exhibits the pure phase structure, and Zn doping does not change the electrochemical reaction process and basic spinel structure of Li₄Ti₅O₁₂. The particle size of both samples is about 300–500 nm. The prepared Li₄Ti_4.95Zn_0.05O₁₂ presents an excellent rate capability and capacity retention. At the charge–discharge rate of 1C, the initial discharge capacity of Li₄Ti_4.95Zn_0.05O₁₂ is 268 mAh g^?1. After 90 cycles at 5C, the discharge capacity of Li₄Ti_4.95Zn_0.05O₁₂ is obviously higher than that of Li₄Ti₅O₁₂. The excellent electrochemical performance of the Li₄Ti_4.95Zn_0.05O₁₂ electrode could be attributed to the improvement of reversibility by doping zinc and the sub-micro particle size.     

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.     

Solid-state synthesis of graphite carbon-coated Li4Ti5O12 anode for lithium ion batteries

Graphites are widely used for their high electrical conductivity and good thermal and chemical stability. In this work, graphitic carbon-coated lithium titanium (Li₄Ti₅O₁₂/GC) was successfully synthesized by a simple one-step solid-state reaction process with the assistance of sucrose without elevating sintering temperature. The lattice fringe of 0.208 nm clearly seen from the high-resolution transmission electron microscopy (HRTEM) images was assigned to graphite (010). The average grain size of the as-prepared Li₄Ti₅O₁₂/GC was about 100–200 nm, 1 order smaller than that of pure Li₄Ti₅O₁₂ prepared similarly. The rate performance and cycle ability were significantly improved by the hybrid conducting network formed by graphitic carbon on the grains and amorphous carbon between them. The specific capacity retention rate was 66.7 % when discharged at a rate of 12C compared with the capacity obtained at 0.5C. After 300 cycles, the capacity retention was more than 90 % at a high rate of 15C.     

Preparation and characterization of spherical La-doped Li4Ti5O12 anode material for lithium ion batteries

The lithium secondary batteries with high power density need the electrode materials with both high specific capacity and high tap density. An “outer gel” method by TiCl₄ as the raw material has been developed to prepare spherical precursor. High tap density spherical Li₄Ti₅O₁₂ is synthesized by sintering the mixture of precursor and Li₂CO₃. La-doped Li₄Ti₅O₁₂ is also prepared by this method. X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, tap density testing, and the determination of the electrochemical properties show that the Li₄Ti₅O₁₂ powders prepared by this method are spherical and exhibits high tap density. La³⁺ dopant improved the electrochemical performance over the pristine Li₄Ti₅O₁₂. It is tested that the tap density of the pristine and La³⁺-doped products is as high as 1.80 and 1.78 g•cm⁻³, respectively. Between 1.0 and 3.0 V versus Li, the initial discharge capacity of the La³⁺ dopant is as high as 161.5 mAh•g⁻¹ at 0.1C rate. After 50 cycles, the reversible capacity is still 135.4 mAh•g⁻¹.     

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.     

Electrochemical properties of TiO2 nanotube-Li4Ti5O12 composite anodes for lithium-ion batteries

For application as an anode material in lithium batteries, composite anodes consisting of TiO₂ nanotubes (TNT) and Li₄Ti₅O₁₂ (LTO) nanocrystalline particles are prepared by hydrothermal reaction of rutile TiO₂ particles, physical blending with LTO, and subsequent heat treatment at 300 °C. The TNT-LTO composites with varying the composition are characterized by electron microscopy, X-ray diffraction, potentiostatic cyclic voltammetry, and galvanostatic charge-discharge tests at various current rates. With higher LTO content, short TNTs with the average tube diameter of 10 nm are distributed among the potato-shaped LTO particles with the average diameter of 200 nm. At higher content of TNT, however, the LTO particles are sparsely distributed in the fibrillar aggregates of TNT with more lengthened image. As a result, the samples of TNT:LTO = 2:8 and 4:6 show superior cycle performance and high-rate capability, mainly due to their higher electrode densities to yield nanotubular TNT distributed on and supported by potato-shaped LTO nanoparticles.     

Performance of solid-state hybrid supercapacitor with LiFePO4/AC composite cathode and Li4Ti5O12 as anode

We report the studies on quasi-solid battery-supercapacitor (BatCap) systems fabricated using sol–gel-prepared LiFePO₄ and its composites (LACs) with activated charcoal (AC) as hybrid cathode and Li₄Ti₅O₁₂ powder as anode separator by flexible gel polymer electrolyte (GPE) film. The GPE film comprises 1.0 M lithium trifluoromethane sulfonate (LiTf) solution in ethylene carbonate (EC)–propylene carbonate (PC) mixture, immobilized poly(vinylidene fluoride-co-hexafluoro-propylene) (PVdF-HFP), which is of high ionic conductivity (∼3.8 × 10⁻³ S cm⁻¹ at 25 °C) and electrochemical stability window (∼3 V). The effect of the addition of AC in composite electrode LACs has been analyzed using various techniques such as X-ray diffraction, porosity analysis, and electrochemical methods. The interfaces of composite LACs and GPE film not only offer high rate performance but also show high specific energy (>27.8 Wh kg⁻¹) as compared to the symmetric supercapacitors and pristine lithium iron phosphate (LiFePO₄)-based lithium ion batteries. The full BatCap systems have been characterized by cyclic voltammetry and galvanostatic charge–discharge tests. The BatCap systems with composite electrodes (LACs) offer better cyclic performance as compared to that of pristine LiFePO₄-based BatCap or LIB LiFePO₄/Li₄Ti₅O₁₂.

     

Structural and electrochemical study on Li(Li1/3Ti5/3)O4 anode material for lithium ion batteries

Chemical and electrochemical studies have shown that various titanium oxides can incorporate lithium in different ratios. Other compounds with a spinel-type structure and corresponding to the spinel oxides LiTi₂O₄ and Li₄Ti₅O₁₂ have been evaluated in rechargeable lithium cells with promising features. The spinel Li[Li_1/3Ti_5/3]O₄ [1–5] compound is a very appealing electrode material for lithium ion batteries. The lithium insertion-deinsertion process occurs with a minimal variation of the cubic unit cell and this assures high stability which may reflect into long cyclability. In addition, the diffusion coefficient of lithium is of the order of 10⁻⁸ cm²s⁻¹ [5] and this suggests fast kinetics which may reflect in high power capabilities. In this work we report a study on the kinetics and the structural properties of the Li[Li_1/3Ti_5/3]O₄ intercalation electrode carried out by: cyclic voltammetry, galvanostatic cycling and in-situ X-ray diffraction. The electrochemical characterization shows that the Li[Li_1/3Ti_5/3]O₄ electrode cycles around 1.56 V vs. Li with a capacity of the order of 130 mAhg⁻¹ which approaches the maximum value of 175 mAhg⁻¹ corresponding to the insertion of 1 equivalent per formula unit. The delivered capacity remains constant for hundred cycles confirming the stability of the host structure upon the repeated Li insertion-deinsertion process. This high structural stability has been confirmed by in situ Energy Dispersion X-ray analysis. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

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.     

Synthesis and characterization of Li4Ti5O12/graphene composite as anode material with enhanced electrochemical performance

The use of graphene as a conductive additive to enhance the rate capability and cycle stability of Li₄Ti₅O₁₂ electrode material has been demonstrated. Li₄Ti₅O₁₂ and its composite with graphene (1.86 wt%) are prepared by ball milling and simple chemical method, respectively. Among the as-synthesized composites, Li₄Ti₅O₁₂ particles uniformly clung to the graphene sheets. When used as an electrode material for lithium ion battery, the composite presents excellent rate performance and high cyclic stability. It is found that the composite displayed high-rate capacity of 118.7 mAh?g^?1 at 20 C. Furthermore, the composite exhibits good cycle stability, retaining over 96 % of its initial capacity after 50 cycles at 10 C. The excellent electrochemical performance is attributed to a decrease in the charge-transfer resistance.     

Sn and SnO2-graphene composites as anode materials for lithium-ion batteries

Sn and SnO₂-graphene composites were synthesized using hydrothermal process, followed by annealing in Ar/H₂ atmosphere, and characterized using x-ray diffraction, scanning electron microscopy, and transition electron microscopy. The results indicated that the polycrystalline metallic Sn forms nanospheres with a diameter of 100?～?300 nm, while the SnO₂ nanoparticles are much smaller with a size below 15 nm, which adsorb tightly on the surface of graphene sheets. The Sn and SnO₂-gaphene composites showed good electrochemical performance. After 55 charging/discharging cycles, the capacity remains above 440 mAh/g at a cycling rate of 400 mA/g and the coulombic efficiency is 99.1 %. The good electrochemical properties of the composites are partially contributed to the graphene component with good mechanical flexibility and electrical conductivity, which is an excellent carbon matrix for dispersing the Sn and SnO₂ nanostructures and provides the electron transport pathways as well.     

Kinetic performance of Li4Ti5O12 anode material synthesized by the solid-state method

Li₄Ti₅O₁₂ anode was successfully synthesized by solid-state method. X-ray diffraction and scanning electron micrographs show that Li₄Ti₅O₁₂ prepared by solid-state method has a purity phase with a uniform particle size in the range of 0.5?C1???m. Cyclic voltammogram reveals that there is a big irreversible capacity for the first cycle. Li₄Ti₅O₁₂ shows a stable cycling stability at 1?C rate. After 152 cycles, the discharge capacity is 213?mAh?g^?1, which keeps 93% of it at the second cycle. Electrochemical impedance spectroscopy shows that the resistance of charge-transfer of Li₄Ti₅O₁₂ electrode decreased with increasing the storage temperatures, and the lithium diffusion coefficient is increased with increasing the storage temperatures, revealing that the kinetics of Li⁺ and electron transfer into the electrodes were much faster at high temperature than that at low temperature. The apparent activation energy of the charge transfer and lithium diffusion can be calculated to be 33.1 and 27.3?kJ?mol^?1, respectively.     

Tin oxide nano-flower-anchored graphene composites as high-performance anode materials for lithium-ion batteries

The SnO₂ nano-flower/graphene (SnO₂-NF/GN) composites were synthesized by using graphene (GN) and SnO₂ nano-flower (SnO₂-NF). Among them, the SnO₂-NFs were prefabricated by using sodium hydroxide and stannic chloride pentahydrate (SnCl₄·5H₂O) as raw materials. The results of SEM show that the SnO₂-NFs are uniformly dispersed on the surface of GN. Furthermore, compared with the pure SnO₂, the as-prepared SnO₂-NF/GN composites displayed superior cycle performace and high rate capability. The SnO₂-NF/GN composite delivers a specific capacity of 650 mAh g^?1 after 60 cycles and an excellent rate capability of 480 mAh g^?1 at 2000 mA g^?1.     

Preparation and characterization of spinel Li4Ti5O12 nanoparticles anode materials for lithium ion battery

Spinel Li₄Ti₅O₁₂ nanoparticles were prepared via a high-temperature solid-state reaction by adding the prepared cellulose to an aqueous dispersion of lithium salts and titanium dioxide. The precursors of Li₄Ti₅O₁₂ were characterized by thermogravimetry and differential scanning calorimetry. The obtained Li₄Ti₅O₁₂ nanoparticles were characterized using X-ray diffraction, transmission electron microscopy (TEM) and electrochemical measurements. The TEM revealed that the Li₄Ti₅O₁₂ prepared with cellulose is composed of nanoparticles with an average particle diameter of 20–30 nm. Galvanostatic battery testing showed that nano-sized Li₄Ti₅O₁₂ exhibit better electrochemical properties than submicro-sized Li₄Ti₅O₁₂ do especially at high current rates, which can deliver a reversible discharge capacity of 131 mAh g⁻¹ at the rate of 10 C, whereas that of the submicro-sized sample decreases to 25 mAh g⁻¹ at the same rate (10 C). Its reversible capacity is maintained at ~172.2 mAh g⁻¹ with the voltage range 1.0–3.0 V (vs. Li) at the current rate of 0.5 C for over 80 cycles.     

Synthesis and electrochemical characterization of InSn4 and InSn4/C as new anode materials for lithium-ion batteries

The InSn₄ intermetallic powders are synthesized via carbothermal reduction route from In₂O₃ and SnO₂. The reaction possibility is estimated by thermodynamic calculation. Pure InSn₄ intermetallic powders with spherical morphology can be obtained at 900 °C in flowing nitrogen. The micro-sized InSn₄ particle is actually composed of a large number of nano-sized grains with polycrystalline and loose structure. The synthesized InSn₄ shows high reversible specific capacity (ca. 500 mAhg^?1) and a good cycling performance as an anode material for lithium-ion batteries. Coating InSn₄ with carbon can increase the reversible specific capacity and improve significantly the rate capability. The InSn₄/C composite displays a stable specific capacity of ca. 600 mAhg^?1. In consideration of the simple and moderate synthesis route and the mass productive feature, the InSn₄/C composite is a promising anode material for lithium-ion batteries.     

Preparation of Si-PPy-Ag composites and their electrochemical performance as anode for lithium-ion batteries

The nanosilicon connected by polypyrrole (PPy) and silver (Ag) particles was simply synthesized by a chemical polymerization process in order to prepare Si-based anodes for Li-ion batteries. The phase structure, surface morphology, and electrochemical properties of the as-synthesized powders were analyzed by X-ray diffraction, FT-IR, scanning electron microscopy, and galvanostatic charge/discharge measurements. The cycle stability of the Si-PPy-Ag composites was greatly enhanced compared with the pure nanosilicon. A high capacity of more than 823 mA h g^?1 was maintained after 100 cycles. The improved electrochemical characteristics are attributed to the volume buffering effect as well as effective electronic conductivity of the polypyrrole and silver in the composite electrode.     

Synthesis and performance of Li2NiTi3O8 as a new anode material for lithium-ion batteries

The titanate spinel Li₂NiTi₃O₈ is proposed for the first time as a new anode for lithium-ion batteries and successfully synthesized via a facile ball-milling assisted solid-state reaction method. The sample is characterized by X-ray diffraction patterns (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge tests, cyclic voltammetry (CV) tests, and electrochemical impedance spectroscopy (EIS). The results reveal that the Li₂NiTi₃O₈ nanoparticles have well-distributed morphology, and the particle size ranges between 100 and 300 nm. Although the initial coulombic efficiency is only 56.3 %, the Li₂NiTi₃O₈ electrode still exhibits a high rate capability and excellent cycling stability. The Li₂NiTi₃O₈ anode provides a large capacity of 212.3 mAh g^?1 at 0.1 A g^?1 after 10 cycle, which is close to its theoretical capacity (223.6 mAh g^?1). Even after 100 cycles, it still delivers a quite high capacity of 203.98 mAh g^?1, with no significant capacity fading. This indicates that the as-synthesized Li₂NiTi₃O₈ material is a promising anode material for lithium-ion batteries.     

Silicon/carbon nanocomposites used as anode materials for lithium-ion batteries

Silicon/carbon nanocomposites are prepared by dispersing nano-sized silicon in mesophase pitch and a subsequent pyrolysis process. In the nanocomposites, silicon nanoparticles are homogeneously distributed in the carbon networks derived from the mesophase pitch. The silicon/carbon nanocomposite delivers a high reversible capacity of 841 mAh g^?1 at the current density of 100 mA g^?1 at the first cycle, high capacity retention of 98 % over 30 cycles, and good rate performance. The superior electrochemical performance of nanocomposite is attributed to the carbon networks with turbostratic structure, which enhance the conductivity and alleviate the volume change of silicon.     

A novel LiSnVO4 anode material for lithium-ion batteries

Ionics - In this work, a new material LiSnVO4 has been prepared via sol-gel method utilizing ammonium metavanadate, acetates of tin and lithium as starting materials, and nitric acid and oxalic...