Electrochemical characteristics of spinel Li4Ti5O12 discharged to 0.01 V

Cycling stability, reversible capacity and rate performance of Li₄Ti₅O₁₂ discharged to 0.01 V were investigated. A couple of obvious and repeatable peaks under 0.6 V observed by CV indicated that Li₄Ti₅O₁₂ possessed reversible capacity below 0.6 V. When discharge voltage of Li₄Ti₅O₁₂ extended from 0.6 to 0.01 V, its cycling stability was not affected and its reversible capacity and high rate performance were improved. Although the capacity obtained from 2.0 to 0.6 V gradually decreased with increasing the applied current density, the capacity obtained from 0.6 to 0.01 V showed little loss. AB was both electronic conducting additive and lithium-ion conducting additive for Li₄Ti₅O₁₂ under 0.6 V.     

Sub-micrometric LiCr0.2Ni0.4Mn1.4O4 spinel as 5 V-cathode material exhibiting huge rate capability at 25 and 55 °C

Single phase LiCr_0.2Ni_0.4Mn_1.4O₄ spinel has been synthesized by a simple sucrose assisted combustion method that yields highly crystalline homogeneous sub-micrometric samples (650 nm). The LiCr_0.2Ni_0.4Mn_1.4O₄, with capacity retention of 92% at 60 C discharge rate, shows the highest rate capability among LiNi_0.5Mn_1.5O₄-type cathodes. It delivers very high-power (34.8 kW kg^?1 at 60 C). Studies developed at 55 °C demonstrate that LiCr_0.2Ni_0.4Mn_1.4O₄ retains huge rate capability and large cycleability at high temperature.     

Preparation and electrochemical performance of monodisperse Li4Ti5O12 hollow spheres

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.     

Preparation and electrochemical lithium storage of flower-like spinel Li4Ti5O12 consisting of nanosheets

In this paper, flower-like spinel Li₄Ti₅O₁₂ consisting of nanosheets was synthesized by a hydrothermal process in glycol solution and following calcination. The as-prepared product was characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction and cyclic voltammetry. The capacity of the sample used as anode material for lithium ion battery was measured. This structured Li₄Ti₅O₁₂ exhibited a high reversible capacity and an excellent rate capability of 165.8 m Ahg⁻¹ at 8 C, indicating potential application for lithium ion batteries with high rate performance and high capacity.     

Synthesis and electrochemical properties of activated carbons and Li4Ti5O12 as electrode materials for supercapacitors

New activated nanoporous carbons, produced by carbonization of mixtures of coal tar pitch and furfural with subsequent steam activation, as well as electrochemically active oxide Li₄Ti₅O₁₂, prepared by thermal co-decomposition of oxalates, were tested and characterized as electrode materials for electrochemical supercapacitors. The phase composition, microstructure, surface morphology and porous structure of the materials were studied. Pure carbon electrodes as well as composite electrodes based on these materials obtained were fabricated. Two types of supercapacitor (SC) cells were assembled and subjected to charge–discharge cycling study at different current rates: (1) symmetric sandwich-type SC cells with identical activated carbon electrodes and different organic electrolytes, and (2) asymmetric hybrid SC cell composed by activated graphitized carbon as a negative electrode and activated carbon–Li₄Ti₅O₁₂ oxide composite as a positive electrode, and an organic electrolyte (LiPF₆–dimethyl carbonate/ethylene carbonate (DMC/EC). Four types of carbons with different specific surface area (1,000–1,600 m² g^?1) and texture parameters, as well as three types of organic electrolytes: Et₄NBF₄–propylene carbonate (PC), LiBF₄–PC and LiPF₆–DMC/EC in the symmetric SC cell, were tested and compared with each other. Capacitance value up to 70 F g^?1 for the symmetric SC, depending on the electrolyte microstructure and conductivity of the carbon material used, and capacitance of about 150 F g^?1 for the asymmetric SC cell, with good cycleability for both supercapacitor systems, were obtained.     

Enhanced electrochemical performance of Li1.2Ni0.2Mn0.6O2 cathode materials through facile layered/spinel phase tuning

Journal of Solid State Electrochemistry - Series Li1.2Ni0.2Mn0.6O2 (LNMO) cathode materials have been synthesized by an improved one-step solvothermal method. Structural characterization reveals...     

Boosting the electrochemical performance of Li4Ti5O12 through nitrogen‐doped carbon coating

The poor electronic conductivity restricts the wide applications of Li₄Ti₅O₁₂ as anode materials in Li‐ion batteries. We report a facile approach to fabricate nitrogen‐doped carbon‐coated Li₄Ti₅O₁₂ through carbonizing pyrrole and pyridine at different temperatures. Comparative experiments demonstrated that the carbon content plays a key role in governing the cycling performance and rate capability of Li₄Ti₅O₁₂. The composites with higher carbon content exhibited superior cycling performance, and the composite prepared at 600 °C using pyridine as the carbon source gave the best cycling and rate performance.     

Synthesis and electrochemical performance of nanoporous Li4Ti5O12 anode material for lithium-ion batteries

Nanoporous Li₄Ti₅O₁₂ (N-LTO) was prepared by sol–gel method using monodisperse polystyrene spheres as a template and followed by calcination process. The as-prepared N-LTO has a spinel structure, large special surface area, and nanoporous structure with the pore average diameter of about 100?nm and wall thickness of 50?nm. Electrochemical experiments show that N-LTO exhibits a high initial discharge capacity of 189?mAh?g^?1 at 0.1?C rate cycled between 0.5 and 3.0?V and excellent capacity retention of 170?mAh?g^?1 after 100?cycles. EIS and CV analysis show that N-LTO has a higher mobility for Li⁺ diffusion and a higher exchange current density, indicating an improved electrochemical performance. It is believed that the nanoporous structure has a larger electrode/electrolyte contact area, resulting in better electrochemical properties at high charge/discharge rates.     

Structure and electrochemical performance of spinel LiMn1.95Ni0.05O3.98F0.02 coated with Li-La-Zr-O solid electrolyte

LiMn_1.95Ni_0.05O_3.98F_0.02 octahedral particles with lithium-ion solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) coating are prepared by a Pechini method. The relationship between the structure and electrochemical performance of the modified samples is investigated. As revealed by X-ray diffraction and scanning electron microscope, LLZO coating does not change the cubic spinel crystal structure of the pristine matrix (space group $ Fd\overline{3}m $ ). Moreover, the LLZO coating materials exist as nanosheets or nanoparticles. The morphology of the coating varies as the weight percentage increases from 1.0 to 3.0. LiMn_1.95Ni_0.05O_3.98F_0.02 coated with 2.0 wt% LLZO exhibits better cycle performance and rate capability at elevated temperature (i.e., 55 °C), while the coating exists as distinct reticulation covering the surface.     

Ab initio studies of structural and electronic properties of Li4Ti5O12 spinel

Structural and electronic properties of Li₄Ti₅O₁₂ spinel are studied from density functional theory based first principles calculations. Differences on these properties between delithiated state Li₄Ti₅O₁₂ and lithiated state Li₇Ti₅O₁₂ are compared. The optimized lattice constant of Li₄Ti₅O₁₂ is 8.619 Å, which is even a little larger (0.2%) than 8.604 Å of the lithiated state Li₇Ti₅O₁₂. The arrangement of the Li and Ti atoms at the 16d sites of the spinel structure is also investigated in a cubic unit cell. Large 1 × 1 × 3 supercell models are constructed and used to calculate the total energy and electronic structure. The average intercalation potential is also calculated, with metallic lithium as reference.     

The electrochemical performance of sodium-ion-modified spinel LiMn2O4 used for lithium-ion batteries

The spinel LiMn₂O₄ cathode material has been considered as one of the most potential cathode active materials for rechargeable lithium ion batteries. The sodium-doped LiMn₂O₄ is synthesized by solid-state reaction. The X-ray diffraction analysis reveals that the Li_1?x Na _x Mn₂O₄ (0?≤?x?≤?0.01) exhibits a single phase with cubic spinel structure. The particles of the doped samples exhibit better crystallinity and uniform distribution. The diffusion coefficient of the Li_0.99Na_0.01Mn₂O₄ sample is 2.45?×?10^?10 cm^?2 s^?1 and 3.74?×?10^?10 cm^?2 s^?1, which is much higher than that of the undoped spinel LiMn₂O₄ sample, indicating the Na⁺-ion doping is favorable to lithium ion migration in the spinel structure. The galvanostatic charge–discharge results show that the Na⁺-ion doping could improve cycling performance and rate capability, which is mainly due to the higher ion diffusion coefficient and more stable spinel structure.     

Effect of TiO2-coating on structure and electrochemical performance of LiCo0.2Ni0.4Mn0.4O2

LiCo_0.2Ni_0.4Mn_0.4O₂, as the cathode material for lithium ion batteries, was modified by TiO₂-coating. The effect of TiO₂-coating on the structure and electrochemical performance of LiCo_0.2Ni_0.4Mn_0.4O₂ was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and galvanostatic charge-discharge tests. The results suggest that a small amount of TiO₂-coating does not change the crystalline structure, but considerably improves the electrochemical performance of LiCo_0.2Ni_0.4Mn_0.4O₂ in terms of capacity delivery and cyclability. XPS measurements confirm that the improved electrochemical performance is most possibly attributed to a decrease in interaction between the layered material and non-aqueous electrolyte during the charge-discharge processes. __________ Translated from Chinese Journal of Inorganic Chemistry, 2007, 23(5): 753–758 [译自: 无机化学学报]     

Synthesis of MgCo2O4-coated Li4Ti5O12 composite anodes using co-precipitation method for lithium-ion batteries

Journal of Solid State Electrochemistry - In the present work, we report synthesis of MgCo2O4 (MCO)/Li4Ti5O12 (LTO) composites for Li-ion battery anodes by a co-precipitation method. The objective...     

Cycling behaviour of Li/Li4Ti5O12 cells studied by electrochemical impedance spectroscopy

We studied the behaviour of Li/Li(4)Ti(5)O(12) cells by electrochemical impedance spectroscopy to gain insight into the changes at the electrode/electrolyte interfaces during extensive cycling. A simple equivalent-circuit model is able to describe the impedance of the complete battery as a function of both state-of-charge and state-of-degradation. The formation of the solid-electrolyte interface and dendrite growth at the Li metal electrode have a strong influence on the impedance measurements although the battery performance is not significantly affected.     

Effects of Cr doping on structural and electrochemical properties of Li4Ti5O12 nanostructure for sodium-ion battery anode

Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several cand...     

A study on structure-performance relationship of overcharged 18650-size Li4Ti5O12/LiMn2O4 battery

The electrochemical properties and thermal generation behavior of 18650 Li₄Ti₅O₁₂/LiMn₂O₄ batteries were tested before and after overcharge. The experimental results showed that after overcharge, the specific capacity decreased obviously. The higher the current density was, the more obvious the capacity decreased. For instance, the overcharged battery had almost no capacity when the current density increased to 5C. At the same time, the overcharged battery presented a much more apparent thermal runaway trend compared to the normal battery. After measuring the electrochemical impedance spectroscopy of the batteries and characterizing the crystal structure/nanostructure of the electrode materials, these phenomena could be attributed to the following two reasons: (1) the decomposition of the electrolyte arisen from the overcharge process resulted in increased internal resistance; (2) the thermal runaway due to the increased internal resistance resulted in the damage to crystal structure/nanostructure and aggregation of the electrode materials, thus leading to the secondary decrease in capacity.     

Epitaxial growth and electrochemical properties of Li4Ti5O12 thin-film lithium battery anodes

Epitaxial Li(4)Ti(5)O(12) thin-films were successfully synthesized on SrTiO(3) single-crystal substrates with (111), (110), and (100) lattice plane orientations using pulsed laser deposition (PLD). Thin-film X-ray diffraction (XRD) revealed that the Li(4)Ti(5)O(12) films had the same orientation as the SrTiO(3) substrates: Li(4)Ti(5)O(12) (111) on SrTiO(3) (111), Li(4)Ti(5)O(12) (110) on SrTiO(3) (110), and Li(4)Ti(5)O(12) (100) on SrTiO(3) (100). These epitaxial films contained island structures, and the morphology of the (111), (110), and (100) films, observed by field emission scanning electron microscopy (FE-SEM), exhibited angular, needle-like, and circular shapes, respectively. The electrochemical properties of 20 nm thick Li(4)Ti(5)O(12) (111) and (110) films were investigated by cyclic voltammetry. Reversible intercalation proceeded through both lattice planes due to the three-dimensional diffusion pathway of lithium in the spinel framework. Reduction peaks in the first cathodic scan appeared at different positions from those in subsequent scans, suggesting a surface reconstruction at the Li(4)Ti(5)O(12) surface due to interfacial reactions.     

Impact of titanium precursors on formation and electrochemical properties of Li4Ti5O12 anode materials for lithium-ion batteries

This work describes comparative study on the application of Li₄Ti₅O₁₂ (LTO) as anode materials for lithium-ion batteries which were successfully prepared by sol-gel synthesis with the use of two titanium sources. One of them was anatase-type titanium dioxide (TiO₂), whereas the second was tetrabutyl titanate (TBT). Both obtained LTO materials were very similar in terms of their crystallinity and purity. In turn, the sample synthetized with TBT source revealed better particle dispersibility, and its particles were slightly lower in size. These particular features resulted in higher Li⁺ diffusion coefficient and better kinetic of Li⁺ ions during charge transfer reactions for the LTO synthetized with TBT source. This reflected in specific capacitance values for both electrodes which equalled 150 mAh g⁻¹, 120 mAh g⁻¹, and 63 mAh g⁻¹ for TBT-LTO and 120 mAh g⁻¹, 80 mAh g⁻¹, and 58 mAh g⁻¹ for TiO₂-LTO at C-rates of 1, 5, and 10 C, respectively.

     

Improvement of overcharge performance using Li4Ti5O12 as negative electrode for LiFePO4 power battery

Liquid state soft packed LiFePO₄ cathode lithium ion cells with capacity of 2 Ah were fabricated using graphite or Li₄Ti₅O₁₂ as negative electrodes to investigate the 3 C/10 V overcharge characteristics at room temperature. The LiFePO₄/Li₄Ti₅O₁₂ cell remained safe after the 3 C/10 V overcharge test while the LiFePO₄/graphite cell went to thermal runaway. Temperature and voltage variations during overcharge were recorded and analyzed. The cells after overcharge were disassembled to check the changes of the separated cell components. The results showed that the Li₄Ti₅O₁₂ as anode active material for LiFePO₄ cell showed obvious safety advantage compared with the graphite anode. The lithium ionic diffusion models of Li₄Ti₅O₁₂ anode and graphite anode were built respectively with the help of morphology characterizations performed by scanning electron microscopy. It was found that the different particle shapes and lithium ionic diffusion modes caused different lithium ionic conductivities during overcharge process.     

Cathodic performance of anatase (TiO2)-coated Li(Ni0.8Co0.2)O2

We report the use of Li(Ni_0.8Co_0.2)O₂ coated with different amounts of anatase (TiO₂) as a cathode material for lithium-ion cells. Electrochemical behavior is modified owing to coating and/or incorporation of titanium into the first few surface layers of Li(Ni_0.8Co_0.2)O₂. Compositions with molar concentrations of x=0.005 and 0.02 exhibit better capacity retention than the mother compound (40 cycles, 0.5 C rate, 2.75–4.30 V). Electronic Publication