Li4Ti5O12 Microspheres Research Articles

Oxygen vacancy-modulated zeolitic Li4Ti5O12 microsphere anode for superior lithium-ion battery

Spinel Li4Ti5O12 (LTO) is a promising anode material for state-of-the-art high-power lithium-ion batteries (LIBs) owing to its “zero strain” characteristics during fast charging/discharging, long cycle life, and high rate capability. However, the poor ionic/electronic conductivity and sluggish ionic diffusion coefficient of LTO restrict its practical utility. Porous zeolitic LTO (Z-LTO) microspheres were synthesized herein as anode materials for LIBs using TiO2 and LiOH∙H2O via a hydrothermal method combined with Ar/H2 thermal treatment. The increased concentration of Ti3+ self-doping-derived oxygen vacancies in as-synthesized Z-LTO and porous microspherical Z-LTO aggregates greatly improved the electronic conductivity and structural stability. These features contributed to achieving much higher discharge capacities of ∼210 and ∼180 mAh g−1 at 0.5 C and 1 C rates, respectively, as well as excellent ultra-high rate capability of 45 mAh g–1 at 50 C rate, while still maintaining the outstanding long-life cyclic stability (∼181 mAh g−1 at 5 C rate after 2000 cycles), with 90% capacity retention, compared to commercial LTO (C-LTO). Charge contribution kinetics analysis indicated that the lithium storage mechanisms in Z-LTO, particularly at a high rate, were dominantly diffusion-controlled due to the larger ion-diffusion ability (DLi ≈ 4.18 × 10−8 cm2 s−1). This finding confirms that the generation of surface defects by creating Ti3+/Ti4+ pairs and oxygen vacancy engineering in LTO is an effective approach for enhancing the ion/electron mobility, which can be extended to boost the battery performance of other materials with low ionic conductivities for advanced energy storage systems.

Carbon-coated Li4Ti5O12 microspheres synthesized through solid-state reaction in a carbon reduction atmosphere for high-rate lithium-ion batteries

Carbon-coated Li4Ti5O12 microspheres synthesized through solid-state reaction in a carbon reduction atmosphere for high-rate lithium-ion batteries

Polymer-templated mesoporous lithium titanate microspheres for high-performance lithium batteries.

The spinel Li4Ti5O12 (LTO) is a promising lithium ion battery anode material with the potential to supplement graphite as an industry standard, but its low electrical conductivity and Li–ion diffusivity need to be overcome. Here, mesoporous LTO microspheres with carbon-coatings were formed by phase separation of a homopolymer from microphase-separated block copolymers of varying molar masses containing sol–gel precursors. Upon heating the composite underwent a sol–gel condensation reaction followed by the eventual pyrolysis of the polymer templates. The optimised mesoporous LTO microspheres demonstrated an excellent electrochemical performance with an excellent specific discharge capacity of 164 mA h g−1, 95% of which was retained after 1000 cycles at a C-rate of 10.

Carbon-Coated Li4ti5o12 Microspheres Synthesized Through Solid-State Reaction in a Carbon Reduction Atmosphere for High-Rate Lithium-Ion Batteries

Carbon-Coated Li4ti5o12 Microspheres Synthesized Through Solid-State Reaction in a Carbon Reduction Atmosphere for High-Rate Lithium-Ion Batteries

Enhanced high-rate performance of Br-doping Li4Ti5O12 microspheres as anode materials for lithium-ion batteries

Br-doping Li4Ti5O12 microspheres (LTOS) with micro-nano hierarchical structure are synthesized using cetyltrimethylammonium hydroxide-assisted hydrothermal and further calcination. The structure and morphology of the obtained Br-doping LTOS were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. It is found that the spherical morphology and spinel-type microstructure of LTOS do not change after appropriate Br doping, but the relative content of Ti3+ increases, which are beneficial for the fast transmission of electronics and ions. Therefore, the rate performances of LTOS are evidently improved after Br doping. Among the doped samples, 0.2Br-LTOS delivers the superior rate performance and cyclic ability. Their specific capacities at 1C, 5C, 10C, 20C, 30C and 40C are 133, 127, 121, 114, 109 and 105 mAh·g−1, respectively. Even at 50C and 60C, their specific capacities are still as high as 101 and 96 mAh·g−1, respectively. Moreover, their capacity retention ratio is about 87.8% after 1000 cycles at 10C, which is higher than 76.5% of pure LTOS.

MWCNT-embedded Li4Ti5O12 microspheres interfacially modified with polyaniline as ternary composites for high-performance lithium ion battery anodes

In this study we used a spray-drying process and in situ polymerization to construct ternary composites of Li4Ti5O12 (LTO) embedded with multi-walled carbon nanotubes (MWCNTs) and interfacially modified with polyaniline (PANI). In these composites, the introduced MWCNTs served as conductive backbones within the spray-dried LTO microspheres, thereby lowering the internal resistance of the microcomposites. The polymerized PANI acted as a conductive adhesive to strengthen the interactions between the MWCNTs and the LTO, leading to a sturdier interface and enhanced ionic transport properties. With the combined effects of the embedded MWCNTs and the interfacially polymerized PANI, we observed significant enhancements in both the conductivity and the ionic diffusion kinetics of the LTO composites. As a result, the ternary composites displayed outstanding electrochemical performance, including enhanced rate capability and remarkable cycling stability. The ternary system delivered a discharge capacitance (134.98 mA h/g) at 20 C that was higher than those of bare LTO (38.6 mA h/g) and MWCNT/LTO (114.88 mA h/g). Furthermore, the composites also exhibited 92.7% retention of their specific capacitance after 200 repeated charge/discharge tests, indicating their excellent cycling life.

Nanosheet-assembled hierarchical Li4Ti5O12 microspheres for high-volumetric-density and high-rate Li-ion battery anode

Fast-charging (high-rate) is a critical need for lithium-ion batteries (LIBs). While superior rate performance can be achieved by nanostructured electrodes, their tap density is often low, which leads to low volumetric energy density and limits their practical applications. Here, we report nanosheet-assembled Li4Ti5O12 (LTO) hierarchical microspheres which can simultaneously achieve high tap density, high rate performance and long cycle life. These microspheres were prepared with high yield by facile solvothermal reaction followed by a short thermal annealing process. The formation mechanism of such LTO microspheres was systematically investigated to understand their morphology evolution and phase transformation process. These well-designed hierarchical microspheres with controlled features on both nanometer- and micrometer-scales enable dense particle packing, easy lithium-ion diffusion and high structure robustness. Optimal LTO microspheres can offer extremely high rate capability (e.g., 155 mAh g−1 at 50 C), and excellent cycling stability (99.5% capacity retention after 2000 cycles at 50 C, 95.4% capacity retention after 3000 cycles at 30 C) with a tap density of 1.32 g cm−3. Furthermore, their superior performance was also demonstrated with LiNi0.5Mn1.5O4 cathode in full cells, which showed 93.4% of capacity retention after 1000 cycles at 3C. These results suggest the great promise of using such high-volumetric-density LTO as an anode material for high-rate and long-life LIBs.

Conductive PProDOT-Me2–capped Li4Ti5O12 microspheres with an optimized Ti3+/Ti4+ ratio for enhanced and rapid lithium-ion storage

Abstract Li 4 Ti 5 O 12 (LTO) has attracted much attention for its use as an anode material within lithium-ion batteries (LIBs), owing to its excellent safety and outstanding cyclability. Unfortunately, the poor electronic conductivity of LTO greatly limits the rate capability of the LIBs and, therefore, its practical applications. The conductivity of LTO can be enhanced significantly through thermal treatment under hypoxic conditions to form oxygen vacancies. The defective LTO with oxygen vacancies has a much higher electric conductivity, owing to partial reduction of the Ti ions (from Ti 4+ to Ti 3+ ). Too many oxygen vacancies generated in the LTO will, however, also cause severe lattice distortion, inhibiting ionic transfer. In this study, we optimized the Ti 3+ /Ti 4+ ratio of LTO by annealing it under various conditions. We also modified the surface of LTO with a thin layer of poly (dimethyl 3,4-propylenedioxythiophene) (PProDOT-Me 2 ) through in situ chemical polymerization. Studies of the surface morphology and chemical composition confirmed that PProDOT-Me 2 had been successfully capped on the LTO surface. Combining the effects of the optimal Ti 3+ /Ti 4+ ratio and the surface modification with PProDOT-Me 2 resulted in the charge and ionic transport properties of LTO both improving significantly. Accordingly, the nanocomposites displayed greatly enhanced rate capabilities, relative to those of the unmodified material.

Spray-drying synthesis of Li4Ti5O12 microspheres in pilot scale using TiO2 nanosheets as starting materials and their application in high-rate lithium ion battery

Spray-drying technique has been widely used for synthesis of energy storage materials due to its low cost and easy scale up. However, in mass production, this method usually suffers from the incomplete solid-state reaction owing to the aggregation or poor reactivity of precursors caused by their large particle size and unfavorable morphology. In this study, spinel Li4Ti5O12 (LTO) has been synthesized by using TiO2 nanosheets as precursor through spray-drying for large-scale production. The TiO2 nanosheets are prepared via a facile and scalable wet grinding method. The high aspect ratio TiO2 nanosheets can efficiently reduce the diffusion length of Li element during the solid-state reaction leading to higher reactivity. It has been found that the temperature required for the formation of LTO phase can be significantly reduced by using the two-dimensional (2D) TiO2 nanosheets as starting materials. As a result, through a pilot-scale spray drying process, the LTO reacted from the TiO2 nanosheets shows a pure spinel structure due to the better morphology of TiO2 nanosheets. In contrast, using the unprocessed TiO2 as precursor, the resulting LTO still reveals other impure phases leading to a poor electrochemical performance. The pure LTO shows a higher discharge capacity of ∼160.8 mAh/g at 0.1 C, with an excellent rate performance and superior cycling life in comparison with the LTO containing impurity phases.

Doping and surface modification enhance the applicability of Li4Ti5O12 microspheres as high-rate anode materials for lithium ion batteries

In this study we prepared Mg2+ and Cr3+ co-doped and phosphidated Li4Ti5O12 (LTO) microspheres using a spray-drying method. Doping with both Mg2+ and Cr3+ improved the electronic conduction of LTO, due to partial reduction of Ti4+ (from Ti4+ to Ti3+) and narrowing of the band gap, respectively. Moreover, the phosphidation process formed a uniform conductive glass layer on the LTO surface, leading to higher ionic conductivity. As a result, the modified LTO exhibited improved rate capability and cyclic stability, compared with those of the pristine LTO. In particular, the Mg2+ and Cr3+ co-doped and phosphidated LTO exhibited superior performance as a result of the combined effects of ion-doping and interfacial modification. Finally, the capacity improved significantly, especially at high C rates [e.g., 127.72 mA h g–1 at 20 C—77.6% of the value recorded at 0.1 C (164.62 mA h g–1)], due to the dual effects of the enhanced electric and ionic conductivities.

Template-free synthesis of biomass-derived carbon coated Li4Ti5O12 microspheres as high performance anodes for lithium-ion batteries

The hierarchical Li4Ti5O12/C microspheres based on the waste biomass of phoenix tree leaf are synthesized as anodes for lithium-ion batteries. The phoenix tree leaf derived activated carbon (CPTL) are uniformly coated on the surface of acanthosphere-like Li4Ti5O12 (LTO) microspheres using a facial hydrothermal method to fabricate hierarchical porous structures with conductive interconnected 3D networks. Results show that the LTO-CPTL composite with 3 wt% carbon delivers the best electrochemical performance at both ambient and low temperatures with an initial discharge capacity of 212 mAh g−1 at 1 C and capacity retention of 95% after 500 cycles. The present study demonstrates a facile and cost-efficient way to fabricate high performance electrode materials for batteries.

Enhanced high-rate performance of Li4Ti5O12 microspheres/multiwalled carbon nanotubes composites prepared by electrostatic self-assembly

Li4Ti5O12 microspheres (LTOS)/multiwalled carbon nanotubes (MWCNTs) composites with different contents of MWCNTs have been prepared by electrostatic self-assembly. In the preparation, the surface charge of cetyltrimethylammonium bromide (CTAB)-functionalized HNO3-treated MWCNTs (CTAB-functionalized MWCNTs) in aqueous solution is positive because of the hydrophobic force between MWCNTs and the long alkane chain of CTAB, while that of LTOS is negative. Therefore, electrostatic attraction occurs between LTOS and CTAB-functionalized MWCNTs when they approach, and LTOS/MWCNTs composites are obtained after removing CTAB by calcination. Notably, LTOS/MWCNTs composites with 10 wt.% MWCNTs exhibit superior rate performance and cyclic stability. Their specific capacities at 5C, 10C, 20C, 40C and 60C are 170, 168, 167, 165 and 160 mAh·g−1, respectively. Even at 80C and 90C, the specific capacities are still as high as 154 and 152 mAh·g−1. Moreover, the specific capacity retains 140 mAh g−1 after 2000 cycles at 10C. The excellent performance of LTOS/MWCNTs composites is mainly owing to the conductive network forming by MWCNTs connecting different LTOS, acting as highway for the fast transmission of electrons and ions during charge-discharge process.

Synthesis and characterization of iron − doped Li4Ti5O12 microspheres as anode for lithium-ion batteries

Li4Ti5O12 microspheres and the equivalent iron doped materials, with 0.1 and 0.2 mol of Fe per unit formula, were synthesized by a solvothermal method. The presence of the dopant was verified by X-Ray diffraction with Rietveld refinement and XPS experiments. It was found that the dopant is included in the lattice structure as Fe (III), at lower concentration the dopant is found primarily on Ti (IV) sites while at higher concentration it occupies both Ti and Li sites. Conductivity measurements indicate that the higher iron concentration increases the material intrinsic electronic conductivity; however, the effect of Fe doping at lower concentration on the conductivity is almost null. Because of the Fe doping, the charge/discharge plateaus are obtained at higher/lower voltages, which might be correlated to lower charge transfer resistance, even though the electrochemical measurements show slightly lower capacities and very similar rate capabilities. Additionally, EIS experiments indicate that the presence of the dopant causes lower charge transfer resistance and enhanced finite lithium diffusion. However, as the size of the particles is still very large, the improved Li+ intercalation properties do not influence the rate capability since this property should be more related to shortened diffusion paths.

Hierarchical Li4Ti5O12 nanosheet arrays anchoring on carbon fiber cloth as ultra-stable free-standing anode of Li-ion battery

A flexible, free-standing composite anode with Li4Ti5O12 nanosheet arrays anchoring on plain-weaved carbon fiber cloth (LTO@CC) is prepared by a hydrothermal and post-annealing process assisted by a TiO2 seed layer. The LTO@CC anode free from polymeric binder and conducting agent exhibited much higher lithium storage capacity and cycling stability than the conventional slurry-processed electrode using the dandelion-like Li4Ti5O12 microspheres prepared by the same hydrothermal process. A high specific capacity of 128.8mAhg−1 was obtained at a current rate of 30C (1C = 175mAg−1), and almost negligible capacity loses was observed when the cell was cycled at 10, 20 and 30C each for 100 cycles. The carbon fiber matrix contributed to Li storage at low current rate, but the LTO nanosheet arrays have played the dominant role on the excellent rate capability. The improved electrochemical performance can be attributed to the synergetic effect between the hierarchical Li4Ti5O12 nanosheet arrays and the carbon fiber matrix, which integrated short Li+ diffusion length, three-dimensional conductive architecture and well preserved structural integrity during the high rate and repeated charge-discharge measurements.

700 F hybrid capacitors cells composed of activated carbon and Li4Ti5O12 microspheres with ultra-long cycle life

To address the large-scale application demands of high energy density, high power density, and long cycle lifetime, 700-F hybrid capacitor pouch cells have been prepared, comprising ∼240-μm-thick activated carbon cathodes, and ∼60-μm-thick Li4Ti5O12 anodes. Microspherical Li4Ti5O12 (M-LTO) synthesized by spray-drying features 200–400 nm primary particles and interconnected nanopore structures. M-LTO half-cells exhibits high specific capacities (175 mAhh g−1), good rate capabilities (148 mAhh g−1 at 20 C), and ultra-long cycling stabilities (90% specific capacity retention after 10,000 cycles). In addition, the obtained hybrid capacitors comprising activated carbon (AC) and M-LTO shows excellent cell performances, achieving a maximum energy density of 51.65 Wh kg−1, a maximum power density of 2466 W kg−1, and ∼92% capacitance retention after 10,000 cycles, thus meeting the demands for large-scale applications such as trolleybuses.

Synthesis of Li4Ti5O12 Microspheres and Their Electrochemical Performance As Anode Materials for Li-Ion Batteries

Lithium titanate, Li4Ti5O12 (LTO) has drawn significant attention in the lithium ion battery because it shows some interesting features such as a low toxicity and low volume change (2-3%) on both lithium insertion and de-insertion, along with an excellent cycling life. Especially, the mesoporous LTO microspheres are considered as an ideal anode material because of their good rate performance, morphological properties, and a large tap density. However, it is very challenging to synthesize monodispersed LTO microspheres with desirable structural characteristics and electrochemical performances. In this study, LTO microspheres were synthesized using a facile process and cheap Ti-source (TiOSO4). The round shaped secondary particles (μm scale) were consisted of LTO primary particles (< 100 nm). The structural properties and electrochemical performances of Li4Ti5O12 microspheres will be discussed in the Meeting.

Ultrathin Li4Ti5O12 Nanosheet Based Hierarchical Microspheres for High‐Rate and Long‐Cycle Life Li‐Ion Batteries

AbstractUltrathin Li4Ti5O12 nanosheet based hierarchical microspheres are synthesized through a three‐step hydrothermal procedure. The average thickness of the Li4Ti5O12 sheets is only ≈(6.6 ± 0.25) nm and the specific surface area of the sample is 178 m2 g−1. When applied into lithium ion batteries as anode materials, the hierarchical Li4Ti5O12 microspheres exhibit high specific capacities at high rates (156 mA h g−1 at 20 C, 150 mA h g−1 at 50 C) and maintain a capacity of 126 mA h g−1 after 3000 cycles at 20 C. The results clearly suggest that the utility of hierarchical structures based on ultrathin nanosheets can promote the lithium insertion/extraction reactions in Li4Ti5O12. The obtained hierarchical Li4Ti5O12 with ultrathin nanosheets and large specific surface area can be perfect anode materials for the lithium ion batteries applied in high power facilities, such as electric vehicles and hybrid electric vehicles.

High Tap Density Li4Ti5O12 Microspheres: Synthetic Conditions and Advanced Electrochemical Performance

AbstractPreparation of uniform, spherical Li4Ti5O12 with high tap density is significant to achieve a high volumetric energy density in lithium‐ion batteries. Herein, Li4Ti5O12 microspheres with variable tap density and tunable size distribution were synthesized by a newly designed industrial spray‐drying approach. The slurry concentration, sintering time, sintering conditions after spraying, and the effect of lithium/titanium molar ratio on the lithium‐ion (Li+) storage capability were investigated. A narrow particle size distribution of around 10 μm and a high tap density close to 1.4 g cm−3 of the Li4Ti5O12 spheres can be obtained under the optimized conditions. The Li4Ti5O12 spheres can deliver a much higher capacity of 168 mAh g−1 at a rate of 1 C and show a high capacity retention of 97.7 % over 400 cycles. The synthetic conditions are confirmed to be critical for improving the electron conductivity and Li+ diffusivity by adjusting the crystal and spatial structures. As‐prepared high‐performance Li4Ti5O12 is an ideal electrode for lithium‐ion batteries or capacitors; meanwhile, the presented approach is also applicable for preparing other kind of spherical materials.

Preparation of Li4Ti5O12 Microspheres with a Pure Cr2O3 Coating Layer and its Effect for Lithium Storage

The pure Cr2O3 coated Li4Ti5O12 microspheres were prepared by a facile and cheap solution-based method with basic chromium(III) nitrate solution (pH=11.9). And their Li-storage properties were investigated as anode materials for lithium rechargeable batteries. The pure Cr2O3 works as an adhesive interface to strengthen the connections between Li4Ti5O12 particles, providing more electric conduction channels, and reduce the inter-particle resistance. Moreover, LixCr2O3, formed by the lithiation of Cr2O3, can further stabilize Li7Ti5O12 with high electric conductivity on the surface of particles. While in the acid chromium solution (pH=3.2) modification, besides Cr2O3, Li2CrO4 and TiO2 phases were also found in the final product. Li2CrO4 is toxic and the presence of TiO2 is not welcome to improve the electrochemical performance of Li4Ti5O12 microspheres. The reversible capacity of 1% Cr2O3-coated sample with the basic chromium solution modification was 180 mAh/g at 0.1 C, and 134 mAh/g at 10 C. Moreover, it was even as high as 127 mAh/g at 5 C after 600 cycles. At −20 °C, its reversible specific capacity was still as high as 118 mAh/g.

Insight into the formation mechanism of Li4Ti5O12 microspheres obtained by a CTAB-assisted synthetic method and their electrochemical performances

Porous Li4Ti5O12 microspheres consisting of a stack of primary nano-crystalline grains were prepared by CTAB-assisted hydrothermal synthesis followed by calcination, and the formation mechanism was proposed.