Spinel Li4Ti5O12 Research Articles

Spontaneous Li-Ion Transfer from Spinel Li4Ti5O12 Surfaces: Deterioration at Li4Ti5O12/Electrolyte Interfaces Stored at Room Temperature

Spinel lithium titanium oxide (LTO; Li4Ti5O12) is one of attractive negative electrode materials for high-performance lithium-ion batteries. We studied the changes of LTO-electrode surfaces in contact with liquid electrolytes without electrochemical operation, as the basic state of a stored cell. The electrochemical properties of the LTO-crystal electrode were greatly deteriorated after soaking in a liquid electrolyte (1 M LiPF6 in PC) for 2 weeks at room temperature. Spinel LTO structure was changed into rock-salt like structure at the surface region. The chemical compositions of Li and O were decreased at the surface region, suggesting spontaneous Li+ and O2− transfer from the LTO surface. The present structural and chemical changes of the surface region was explained as disordered-spinel phase generation with less Li-ion conductivity.

Suppression of interfacial reactions between Li4Ti5O12 electrode and electrolyte solution via zinc oxide coating

Li4Ti5O12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process. The interfacial reactions between LTO and electrolyte solution may be the main reason. In this work, the LTO spinel particles are modified with ZnO coating using a chemical process to reduce the surface reactivity of LTO particles. Results show that the ZnO coating can effectively stabilize the electrode/electrolyte interface and suppress the formation of a solid electrolyte interface (SEI) film. Simultaneously, this ZnO modification can improve the electronic conductivity and lithium ion diffusion coefficient, which contributes to a great improvement in cyclic and high rate capabilities of LTO electrode. The ZnO coating on LTO may be an effective method to restrict the gassing behavior of LTO based battery.

Dual Functions of Carbon in Li4Ti5O12/C Microspheres

Spinel Li4Ti5O12 has become an alternative material to replace graphite anodes in terms of solving safety issues and improving battery life-time. Unfortunately, as Li4Ti5O12 is an insulator, the low electrical conductivity becomes a major drawback, as it is unfavorable to higher rate capability. In addition to the low electronic conductivity, severe gassing during charge/discharge cycles is a critical but often-overlooked problem of Li4Ti5O12 batteries. Li4Ti5O12/C microspheres were prepared by assembling the nano-Li4Ti5O12 (50–300 nm) with pitch derived pyrolytic carbon. It was found that the coated carbon in Li4Ti5O12/C microspheres can effectively inhibit gassing and Mn deposition in LiMn2O4//Li4Ti5O12 battery. Carbon can also significantly improve rate capability and cycling performance compared with that of Li4Ti5O12 microspheres without carbon due to stable interface and superior electronic conductivity.

Three-dimensional hierarchical Li4Ti5O12 nanoarchitecture by a simple hydrothermal method.

The spinel Li4Ti5O12 (LTO) is a promising candidate as a superior electrode material for energy storage devices due to the extremely small volume expansion/contraction during the charge/discharge processes of a battery. There are various synthetic approaches for the nanostructured LTO electrode: sol-gel, sonochemical, solution-combustion, hydrothermal methods, and others. Herein, three-dimensional (3D) high-density heterogeneous LTO architectures are fabricated by employing the TiO2 nanorods (NRs) branched SnO2 nanowire (NW) arrays as the template. The TiO2 NRs were effectively converted by the hydrothermal method into the LTO NRs that have a width of 40-nm and length of 100-nm, which induce branch/backbone structured LTO-SnO2 composites. Interestingly, the 3D LTO architectures exhibit unique geometrical shapes because the NRs are surrounded by small nanoparticles. We also discuss how the temperature and solvent affect the LTO nanostructure formation in detail. These results suggest that using a template can provide a new method for designing and synthesizing various classes of 3D architecturing synthesis.

Advanced charge performance of pristine Li4Ti5O12 spinel for power lithium-ion battery

Intense research works had been devoted worldwide to the improvement of electrons conductivity of Li4Ti5O12 spinel to get better power performances. In this study, our experimental results revealed that pristine Li4Ti5O12 spinel possessed excellent power charge performance. Three charge–discharge modes were employed to take advantage of its outstanding power charge capacity. The power capacity of Li4Ti5O12 spinel was increased about 13 times at high current density by using an appropriate working mode. Even at 30C, Li4Ti5O12 could keep 90% of the reversible capacity at 0.5C in the improved mode, whereas it was only 7% in the ordinary mode. The corresponding improvement mechanism of different working modes was demonstrated. Our results suggested that designing appropriate working modes for electrode materials according to their inherent characteristics would be a promising way to achieve advanced performance in the field of lithium-ion battery.

Facile solution-based synthesis of spinel Li4Ti5O12 nanosheets and the application in lithium ion Batteries

A simple low-temperature solution-synthesis method is developed for preparing nanostructured Li4Ti5O12. Compared with normal hydrothermal synthesis (temperature>120°C), this low-temperature (60°C) approach is more suitable for fabricating pure Li4Ti5O12 nanomaterials on a large scale due to its low requirements of reaction conditions and equipments. The as-prepared Li4Ti5O12 nanosheets are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and cyclic voltammetry. Galvanostatic testing results show that the discharging capacity of the sample still remains 148.9mAhg−1 at 10C rates after 100cycles, presenting excellent rate performance and cycle stability.

Study on the Improvement of Rate Capability of Spinel Li4Ti5O12 with Graphene/Carbon Nanotubes Binary Conductive Additive

Study on the Improvement of Rate Capability of Spinel Li4Ti5O12 with Graphene/Carbon Nanotubes Binary Conductive Additive

Study on the energy band structure and photoelectrochemical performances of spinel Li4Ti5O12

Energy band structure, photoelectrochemical performances and photocatalysis activity of spinel Li4Ti5O12 are investigated for the first time in this paper. Li4Ti5O12 possesses more positive valence band potential and wider band gap than TiO2 due to its valence band consisting of Li1s and Ti3d orbitals mixed with O2p. Li4Ti5O12 shows typical photocatalysis material characteristics and excellent photocatlytic activity under UV irradiation.

Li4Ti5O12 thin-film electrodes by in-situ synthesis of lithium alkoxide for Li-ion microbatteries

Rechargeable thin-film batteries have recently become the topic of widespread research for use as efficient energy storage devices. Spinel Li4Ti5O12 has been considered as one of the most prospective anode materials for Li-ion batteries because of its excellent reversibility and long cycle life. We report here the sol–gel synthesis and coating preparation of spinel thin-film Li4Ti5O12 electrodes for Li-ion microbatteries using lithium ethoxide produced in situ that reacts with titanium alkoxide to produce the precursor solution without particle precipitation. This synthesis procedure reduces the thermal treatment to obtain a pure phase at only 700°C and 15minutes. The physical and structural characterization of the 300nm Li4Ti5O12 coatings shows a very homogeneous distribution of elements and a pure spinel phase. Galvanostatic discharge-charge tests indicate maximum discharge capacities of 152mA h g−1 when the material is treated at 700°C for 15minutes.

Bamboo carbon assisted sol–gel synthesis of Li4Ti5O12 anode material with enhanced electrochemical activity for lithium ion battery

To control the morphology of inorganic electrode materials for high performance lithium ion batteries, bamboo carbon with highly ordered three-dimensional microscopic porosity was employed to act as a template to confine the growth of spinel Li4Ti5O12 anode nanoparticle in its sol–gel synthesis. The bamboo carbon was removed by high temperature calcination thereafter to produce pure spinel Li4Ti5O12 (BC-LTO). The electrochemical properties of BC-LTO were thoroughly evaluated in lithium ion batteries and compared with the electrochemical properties of the spinel Li4Ti5O12 synthesized without bamboo carbon template (P-LTO). The crystal structures of BC-LTO and P-LTO were identified as the same spinel structure by X-ray diffraction. The positive effects of adding bamboo carbon during the electrode synthesis were observed to be reducing both the particle size and size distribution of BC-LTO as evidenced by scanning electron microscopy (SEM). Cyclic voltammetry (CV) analysis demonstrated that BC-LTO had a higher lithium insertion/extraction reversibility than P-LTO. The BC-LTO anode delivered a capacity of 160mAhg−1 after 50cycles at a rate of 0.2C, much higher than the P-LTO anode which only delivered 139mAhg−1 under the same conditions. Detailed galvanostatic charge/discharge tests using various current rates were carried out, and the results demonstrated that BC-LTO is a promising candidate anode material for high performance lithium ion batteries. The bamboo carbon assisted sol–gel method was therefore proven to be effective in our study, and should be able to be applied to other electrochemical systems.

Hydrothermal synthesis and characterization of titanium dioxide nanotubes as novel lithium adsorbents

The ion exchange process is a promising method for lithium extraction from brine and seawater having low concentrations of this element. To achieve this goal, it is vital to use an effective adsorbent with maximum lithium adsorption potential together with a stable structure during extraction and insertion of the ions. In this study, titanium dioxide and then lithium titanate spinel with nanotube morphology was synthesized via a simple two-step hydrothermal process. The produced Li4Ti5O12 spinel ternary oxide nanotube with about 70nm diameter was then treated with dilute acidic solution in order to prepare an adsorbent suitable for lithium adsorption from local brine. Morphological and phase analysis of the obtained nanostructured samples were done by using transmission and scanning electron microscopes along with X-ray diffraction. Lithium ion exchange capacity of this adsorbent was finally evaluated by means of adsorption isotherm. The results showed titanium dioxide adsorbent could recover 39.43mg/g of the lithium present in 120mg/L of lithium solution.

True atomic-scale imaging of a spinel Li4Ti5O12(111) surface in aqueous solution by frequency-modulation atomic force microscopy

Spinel-type lithium titanium oxide (LTO; Li4Ti5O12) is a negative electrode material for lithium-ion batteries. Revealing the atomic-scale surface structure of LTO in liquid is highly necessary to investigate its surface properties in practical environments. Here, we reveal an atomic-scale image of the LTO(111) surface in LiCl aqueous solution using frequency-modulation atomic force microscopy. Atomically flat terraces and single steps having heights of multiples of 0.5 nm were observed in the aqueous solution. Hexagonal bright spots separated by 0.6 nm were also observed on the flat terrace part, corresponding to the atomistic contrast observed in the ultrahigh vacuum condition, which suggests that the basic atomic structure of the LTO(111) surface is retained without dramatic reconstruction even in the aqueous solution.

Oligomer-salt derived 3D, heavily nitrogen doped, porous carbon for Li-ion hybrid electrochemical capacitors application

3D high surface area porous carbon is seen to form via self assembly of porous graphene sheets by direct pyrolysis of an oligomer salt tailored for the realization of molecular level activation. The oligomer salt was derived from 4-amino benzoic acid as the monomer by a facile free radical polymerization process. Incorporation of the functional groups (COONa) eliminate the need for any external activating agents (KOH, ZnCl2, etc.) and also render high degree of sub-nanoscale homogeneity. This oligomer derived carbon (ODC) exhibits efficient performance in non-aqueous charge storage application namely Li-ion hybrid electrochemical capacitor (Li-HEC) owing to its high surface area, 3D interconnectivity and an appropriate pore size distribution. The Li-HEC fabricated with ODC based electrodes delivered a maximum energy density of ∼63Whkg−1 with spinel Li4Ti5O12 as the anode.

Al2O3 Coated Li4Ti5O12 Electrode with Enhanced Cycle Performance for Lithium Ion Battery

Spinel Li4Ti5O12 anode was prepared by traditional doctor blade method. The as-prepared electrode was coated with a thin Al2O3 layer by a facile radio frequency (RF) magnetron sputtering afterwards. The structure and morphology were characterized by XRD and SEM. The electrochemical performance was collected by galvanostatic discharge-charge tests. The measuring potential range was between 0.01 V and 3.0 V. The reversible capacity was as high as 194 mAh/g when discharge/charged at a current density of 35 mA/g. The coating layer did not hinder the performance under high current density, showing the discharge capacity of 134 mAh/g at 175 mA/g. The capacity retention after 100 cycles at 88 mA/g is 91%, much higher than that of the pristine Li4Ti5O12 electrode. The greatly improved cycle stability was attributed to the reduced polarization and the enhanced integrity of the electrode structure.

Li3.9Cu0.1Ti5O12/CNTs composite for the anode of high-power lithium-ion batteries: Intrinsic and extrinsic effects

Although spinel Li4Ti5O12 is an attractive anode material for lithium-ion batteries (LIBs), it suffers from its poor rate performance. To improve the rate performance, a Li3.9Cu0.1Ti5O12 and carbon nanotubes (CNTs) composite was fabricated through mixing CNTs with Li3.9Cu0.1Ti5O12 particles. X-ray diffraction combined with Rietveld refinement, X-ray photoelectron spectroscopy, field emission scanning electron microscope, transmission electron microscope, nitrogen adsorption–desorption measurement, electrochemical impedance spectroscopy, two-terminal electronic conductivity test and galvanostatic discharge–charge test were employed for the characterizations. The Cu+ substituting negligibly changed the particle size but modified the crystal structure. Consequently, the electronic and Li+ ion conductivities of Li3.9Cu0.1Ti5O12 were respectively increased to 4.0×10−8 S cm−1 and 5.6×10−7 S cm−1, which are at least forty and four times larger than those of the pristine Li4Ti5O12. Through incorporating CNTs, the electrical conduction between the Li3.9Cu0.1Ti5O12 particles was enhanced. As a result of these simultaneous improvements arising from the synergistic effect combining intrinsic improvement by Cu+ substituting and extrinsic enhancement by CNTs compositing, Li3.9Cu0.1Ti5O12/CNTs shows a significantly improved rate performance, which is better than those of Li3.9Cu0.1Ti5O12, Li4Ti5O12/CNTs and Li4Ti5O12. The specific capacity of Li3.9Cu0.1Ti5O12/CNTs at 10C is up to 103 mAh g−1 between 1.0 and 2.5V (vs. Li/Li+), in contrast to those of Li3.9Cu0.1Ti5O12, Li4Ti5O12/CNTs and Li4Ti5O12 to be only 29, 68, 12 mAh g−1 at the same rate. In addition, Li3.9Cu0.1Ti5O12/CNTs exhibits high cyclic stability with capacity retention of 96.3% over 100 cycles. These advanced electrochemical performances may render Li3.9Cu0.1Ti5O12/CNTs a promising candidate for the anodes of high-power LIBs.

Fabrication of Li4Ti5O12 Spinel Thin Films for Li Mirobattery Applications

Lithium titanium oxide spinel Li4Ti5O12 has been reported to be a zero-strain lithium insertion host material because it exhibits extremely small variations of the lattice parameters during the charge and discharge processes. In general, Poor adhesion between thin-film electrode and substrates is the common cause for performance degradation of thin-film electrode during repeated charge/discharge tests. Thus, Li4Ti5O12 spinel may be the ideal candidate for the anode of thin-film Li ion battery for long cycle applications.However, different electrochemical behaviors will be expected when Li4Ti5O12 spinel is prepared in thin-film compared to that in power forms. Therefore, the objective of this work is (1) to fabricate thin film of Li4Ti5O12 spinel by using RF-sputtering technique, (2) to investigate the effect of annealing temperature/atmospheres on the electrical/electrochemical properties of thin film Li4Ti5O12, (3) to evaluate the feasibility of using thin film of Li4Ti5O12 as anode for Li microbattery applications.In this study, the Li4Ti5O12 thin film was deposited on either the Si substrate or glass substrate by sputtering technique. The crystallization of deposited Li4Ti5O12 thin film will be enhanced by annealing at various atmospheres and temperatures. The single phase Li4Ti5O12 was finally obtained after co-sputtering of Li-containg and Ti-containing targets. The crystal structure and crystallization will be examined by glancing XRD. The resistivity of Li4Ti5O12 thin film will be evaluated by four probe technique and our novel micromeaurement system. The capacity of Li4Ti5O12 thin film will be evaluated from charge/discharge tests.

Superior rate performance of Li4Ti5O12/TiO2/C/CNTs composites via microemulsion-assisted method as anodes for lithium ion battery

Spinel Li4Ti5O12 (LTO) is a promising anode material of lithium ion batteries for electric vehicles and hybrid electric vehicles due to its long cycle life, well-known stable structure, and high safety. Whereas, the electronic conductivity of spinel LTO is intrinsically low. To circumvent this drawback, composites of Li4Ti5O12/TiO2/Carbon/Carbon nanotubes (LTO/TiO2/C/CNTs) are prepared by a novel wet-chemical method (reversed-phase microemulsion method), including high electronic conductive CNTs and excess TiO2. The presence of carbon can suppress the growth of LTO particles and lead the appearance of TiO2 during synthesis process. The average particle size of LTO is about 30nm. The LTO/TiO2/C/CNTs composites deliver exceptional electrochemical performance in the voltage window 1.0 -2.5V. It presents a discharge capacity of 224 mAh.g−1 at 0.15C and 95 mAh.g−1 at a high current rate of 24C (4.2 A.g−1). It is found that the TiO2 not only has electrochemical activity but also results in interfacial effect to hugely increase its rate performance.

A highly reversible, low-strain Mg-ion insertion anode material for rechargeable Mg-ion batteries

Rechargeable magnesium (Mg) batteries have been attracting increasing attention recently because of the abundance of the raw material, their relatively low price and their good safety characteristics. However, rechargeable Mg batteries are still in their infancy. Therefore, alternate Mg-ion insertion anode materials are highly desirable to ultimately mass-produce rechargeable Mg batteries. In this study, we introduce the spinel Li4Ti5O12 as an Mg-ion insertion-type anode material with a high reversible capacity of 175 mA h g−1. This material possesses a low-strain characteristic, resulting in an excellent long-term cycle life. The proposed Mg-storage mechanism, including phase separation and transition reaction, is evaluated using advanced atomic scale scanning transmission electron microscopy techniques. This unusual Mg storage mechanism has rarely been reported for ion insertion-type electrode materials for rechargeable batteries. Our findings offer more options for the development of Mg-ion insertion materials for long-life rechargeable Mg batteries.

Spinel Li4–2xCo3xTi5–xO12 (0 ≤ x ≤ 0.5) for Lithium-Ion Batteries: Crystal Structures, Material Properties, and Battery Performances

Although disordered spinel Li4Ti5O12 with Fd3̅m space group is an attracting anode material for lithium ion batteries, it suffers from its poor rate performance. Moreover, there are very limited studies of ordered spinel anode materials with P4332 space group. Here, spinel Li4–2xCo3xTi5–xO12 materials with Fd3̅m (0 ≤ x ≤ 0.2) or P4332 (0.25 ≤ x ≤ 0.5) space group have been synthesized. The lattice parameter and occupancy of Co2+ ions in tetrahedral 8a/8c sites quasi-linearly increase with the amount of Co2+ substitutes. Due to the increased lattice parameter and free 3d electrons in Co2+ ions, Co2+-substituted samples exhibit improved Li+ ion diffusion coefficients and electronic conductivities. The optimized sample, Li3.5Co0.75Ti4.75O12 with P4332 space group, shows the highest Li+ ion diffusion coefficient of 9.07 × 10–11 cm2 s–1 and electronic conductivity of 1.49 × 10–7 S cm–1. Consequently, Li3.5Co0.75Ti4.75O12 has the best rate performance with a large capacity of 158 mAh g–1 at a current density of 1000 mA g–1, while Li4Ti5O12 only possesses 70 mAh g–1. Furthermore, the considerable occupancy of Co2+ ions in the tetrahedral sites tailors the shape of discharge profiles. Li3.5Co0.75Ti4.75O12 exhibits a much smaller plateau hysteresis than the previously developed spinel anode materials with the same space group.

Spherical Carbon Coated Li4Ti5O12 Materials with Stable Interface

Spinel Li4Ti5O12 has become an alternative material to replace electrode in terms of solving these safety issues and improving the life time. Compared with carbon-based anode materials, Li4Ti5O12 exhibits a flatter operation potential plateau and higher operating voltage of about 1.55 V versus Li/Li+, which can make the issue of lithium dendrite deposition on the surface of anode materials entirely resolved. Unfortunately, as Li4Ti5O12 is an insulator, the low electrical conductivity becomes a major drawback which is unfavorable to higher rate capability. Besides the low electronic conductivity, severe gassing during charge/discharge cycles is a critical but often-overlooked problem of Li4Ti5O12 batteries. To date, this issue is at present unsettled but will clearly bear heavily on electrode materials, electrolyte and battery system. Gassing is not always occurs, the most serious swelling occurs only in Mn-contained cathode battery system, such as LiMn2O4 and LiNi1/3Mn1/3Co1/3O2 cathode based battery system. Stable cycle performance is more likely to occur when the cathode has high stability in electrolyte, such as LiCoO2. In this paper, our main goal is to synthesize Li4Ti5O12 materials with high rate electrochemical performance and stable interface, which can effectively suppress gassing in LiMn2O4/ Li4Ti5O12 battery system. For these purposes, the micro-spherical Li4Ti5O12 were prepared by clustering the nano-sized Li4Ti5O12 (100~200nm) without carbon and with carbon respectively. It was found that the spherical clusters of nano-Li4Ti5O12 assembled with carbon (SCN-LTO/C) exhibits significantly improved rate capability and cycling performance compared with that of non-carbon spherical clusters of nano-Li4Ti5O12 (SCN-LTO). More important, it also shows stable interface in LiMn2O4/Li4Ti5O12 system. This stable interface can significantly suppress the gas generation reaction during charging/discharging processes in LiMn2O4/Li4Ti5O12 system. In this paper, gas generation mechanisms in LiMn2O4/Li4Ti5O12 battery system are also discussed. For SCN-LTO, gassing phenomenon in the LMO/LTO batteries is ascribable to the manganese deposition in the anode materials, while for SCN-LTO/C materials, carbon coating can effectively cause the inhibition of manganese deposition and side-reactions, highlighting the importance of the stable interface for Li4Ti5O12 materials in high-performance LIBs.