Li4Ti5O12 Particles Research Articles

Analysis of intrinsic properties of Li4Ti5O12 using single-particle technique

Attractive electrochemical properties of Li4Ti5O12 (LTO) as an anode material for lithium-ion batteries originate primarily from the lithium-ion diffusion behavior in the crystal lattice. Therefore, it is extremely important to understand the inherent material properties that are favorable for superior kinetic performance. Here we report on the intrinsic electrochemical properties of LTO without the influence of inactive electrode components (e.g., binder, conductive agent) using single-particle measurement technique. Electrochemical analysis revealed an exceptionally high rate capability of a single LTO particle compared to the conventional LTO-based electrode. In particular, a single LTO particle demonstrates capacity retention of 88% even at 440 C-rate, while conventional LTO-based electrode shows a two-fold decrease in capacity at 30 C-rate, though it is temperature dependent. Particular attention is paid to determine the correlation of phase transition behavior in a single LTO particle with activation energies of exchange current (io), charge transfer resistance (Rct) at the electrode/electrolyte interface, and diffusivity (D) of lithium-ion in the lattice obtained by single-particle measurement technique.

Investigation of Li4Ti5O12 As a High Power Anode Material in Li-Ion Capacitor (LIC),

Li-ion capacitor (LIC) technology is an advanced energy storage device that helps bridge the massive gap between Li-ion batteries (LIBs) and electric double-layer capacitor (EDLC), by incorporating the inherent advantages of both devices. It uses a LIB material as an anode (e.g. hard carbon or graphite) and EDLC (e.g. activated carbon) as a cathode to improve the energy density, power density, and cycle life. However, there are some applications that need an extremely fast rate of charge and discharge (high rate performance) which the present LIB electrode material used in LIC cannot provide. This is due to various limitations of the LIB electrode material which are; structural damage of the material during high rate performance, the safety of the material, and the cyclability. Lithium titanate oxide (Li4Ti5O12) is a material that can satisfy the requirements needed in high rate performance. This is because of its zero-strain insertion feature, very high safety, high efficiency, and excellent cyclability. However, it has an inherent problem of low electronic conductivity and poor ion diffusion. In order to address this issues, various approaches have been carried out by many researchers and it includes nano-structuring of the particle size to improve Li+ ion diffusion, surface coating with carbon, composting and many more. In this work, investigation of Li4Ti5O12 as an anode material in LIC is done by using one synthesis method (sol-gel) to synthesize Li4Ti5O12 of different particle sizes. The effect of different particle sizes of the synthesized Li4Ti5O12 on its performance as an anode in LIC is studied in terms of energy density, power density, efficiency, and cycle life. Cathode to anode ratio effect in LIC performance is also carried out. Also, the study of different carbon coating thicknesses on the Li4Ti5O12 particles and how it affects its performance will also be carried out.

(Invited) Nanoscale (XPEEM) Spectroscopy Unveils the Complex Local (Electro-) Chemical Surface Reactions of Cycled Electrodes in Li-Ion Batteries

Understanding the electrode-electrolyte interface evolution during cycling as well as the surface structural change of the active materials is crucial to improve the safety and the life-cycle of Li-ion batteries. Despite the large effort directed at elucidating the nature and origin of the surface reactivity of the electrodes in liquid organic electrolytes, there is still no complete knowledge of the various mechanisms that take place at such interfaces. The lack of agreement in the reported findings is caused mainly by the surface complexity of the commercial electrodes (multiple particles, high roughness and porosity) and by the intrinsic limitations of the commonly used surface characterization techniques, (mainly the poor lateral resolution). Thus, in this contribution the recent development on X-Ray Photoelectron Emission Spectroscopy (XPEEM) will be presented, as a surface analytical technique capable of providing local information on single particles of anode and cathode materials, while maintaining the complex formulation of composite electrodes. The unique combination of the nanoscale lateral resolution and the spectroscopic capability, confined to within the depth analysis range of 3-4 nm, enable us to provide the missing piece of the exact mechanism of the electrolyte-electrode interactions. Two commercially-relevant electrodes for Li-ion battery will be presented during the talk, namely Li4Ti5O12 (LTO) and the high-voltage cathode lithium rich Li1+x (NiaCobMn1-a-b)1-xO2 (Li-rich NCM) after cycling in the conventional liquid carbonate electrolytes. In the first system, the controversial surface reactivity of LTO when is cycled in carbonate-based electrolyte is resolved. Despite the theoretical prediction of a stable electrochemical interface, the electrolyte reduction is found to occurs solely on LTO particles during lithiation. With the support of density functional theory (DFT) calculations, we show that this behavior is caused by the solvents adsorbed on the LTO outer planes driven by the Li-ion insertion. The DFT calculation indicates that Li-ion insertion leads to a shift of the LUMO of the adsorbed solvents to energies below the Fermi level position of lithiated Li7Ti5O12 and thus to chemical instability.[1]In the second system, at the Li-rich NCM interface, two major parasitic reactions were identified at high potential. The first reaction is related to the electrolyte oxidation, whereas the second is associated with the Li-rich NCM surface degradation.[2] Those parasitic reactions are caused mainly by the oxidation of oxygen leading to the chemical oxidation of the electrolyte solvents and to the formation of a surface layer containing reduced transition metals (TMs).[3] The presence of electrolyte by-products and TMs "cross-talk" is also demonstrated between the cathode and the anode, creating on the latter a layer rich of micrometer-sized agglomerates of TMs. The impact of these parasitic reactions on the electrodes electrochemical cycling performance will be discussed. Finally, as a further development of the technique, operando XPEEM will be presented and discussed on all-solid-state batteries for the working electrode LiCoO2 mixed with (Li2S)3-P2S5 (LPS), used as a solid electrolyte. [1] D. Leanza, C. A. F. Vaz, I. Czekaj, P. Novák, M. El Kazzi, Journal of Material Chemistry A, 2018, 6, 3534–3542. [2] D. Leanza, C. A. F. Vaz, G. Melinte, X. Mu, P. Novák, M. El Kazzi, ACS Appl. Mater. Interfaces, 2019, 11, 6054−6065. [3] D. Leanza, M. Mirolo, C. A. F. Vaz, P. Novák, M. El Kazzi, Batteries & Supercaps, 2019, 2, 1-12.

Effect of fluoroethylene carbonate as an electrolyte solvent in the LiNi0.5Mn1.5O4/Li4Ti5O12 cell

Fluoroethylene carbonate (FEC) is used as solvent for the antioxidation electrolyte system in the LiNi0.5Mn1.5O4/Li4Ti5O12 cell. We use scanning electron microscopy to analyze the solid electrolyte interphase (SEI) film covered from the surface of individual particles to the top of electrodes. The stable, uniform SEI films formed on individual Li4Ti5O12 particles with FEC solvent are responsible for the significantly improved electrochemical performance. Meanwhile, our results show that severe swelling could be observed and heavier manganese (Mn2+) deposition could be detected on top of the Li4Ti5O12 electrode surface. In this study, we adopt the metathesis reaction to illustrate the relationship between gradual changes in the SEI film and swelling problems during cycling performance. Moreover, the reduction mechanisms of FEC proposed in this study have provided a better understanding of the key issue on electrolyte system that for commercial LiNi0.5Mn1.5O4/Li4Ti5O12 cell.

Atomic Layer Fluorination of the Li4Ti5O12 Surface: A Multiprobing Survey

Li4Ti5O12 (LTO) particles are successfully modified by an atomic layer fluorination process using a one-shot solvent-free synthesis performed with a solid-state fluorinating agent, xenon difluoride...

Interconnected Ultrasmall V2O3 and Li4Ti5O12 Particles Construct Robust Interfaces for Long-Cycling Anodes of Lithium-Ion Batteries.

Designing composite structures of active materials is critical for high-performance lithium-ion batteries, as it determines the reversibility of lithium-ion insertion and extraction of the electrodes. The V2O3 anode has a high specific capacity but presents poor cycling stability due to a large volume change. Herein, a novel C@V2O3-Li4Ti5O12 composite with ultrastable cycling stability is constructed. In this composite structure, the interconnected ultrasmall V2O3 and Li4Ti5O12 nanoparticles (5-10 nm) construct robust interfaces in the carbon matrix. The Li4Ti5O12 nanoparticles with excellent cycling stability and a minor volume change act as fixtures that effectively restrict the volume change of V2O3 nanoparticles and improve the cycling stability of the C@V2O3-Li4Ti5O12 composite. The C@V2O3-Li4Ti5O12 composite maintains no degradation during 500 cycles under a current density of 100 mA g-1. The results demonstrate that constructing a highly stable interface between the active nanoparticles with smaller and larger volume changes is of great significance to suppress their pulverization and achieve high reversibility. This work contributes to a new strategy to design the structure of long-cycling anode materials for highly stable lithium-ion batteries.

Li4Ti5O12 coated with ultrathin aluminum-doped zinc oxide films as an anode material for lithium-ion batteries

Aluminum-doped zinc oxide (AZO) films were coated on the surface of Li4Ti5O12 (LTO) particles via atomic layer deposition (ALD) in a fluidized bed reactor. The electrochemical characterization results indicated that the coating of AZO significantly improved the electrochemical performance of LTO between 0.1 V and 3.0 V with a proper coating thickness. Among all AZO-coated LTO samples, 250-10AZO (nine cycles of ZnO ALD followed by one cycle of Al2O3 ALD at a deposition temperature of 250 °C) showed the best performance. After 250 cycles of charge/discharge at a 1 C rate (1 C = 175 mA g−1), the capacity decreased from 203 to 190 mAh g−1 with a capacity retention of ~94% at room temperature and from 224 to 216 mAh g−1 with a capacity retention of ~96% at 55 °C. The AZO coating layer with an appropriate thickness not only increased the capacity of LTO by enhancing conductivity, but also assisted the LTO electrodes to form a beneficial interface layer to protect the LTO from the continuous attack by harmful components in the electrolyte, especially under extreme conditions, such as high temperature and high current rates.

Solid-state synthesized Li4Ti5O12 for ultrafast lithium ion storage enabled by carbon-coating induced particle size tailoring

We synthesize the size-tailored Ce:Li4Ti5O12 via a facile solid-state method. During the synthesis, a carbon-coating forms in-situ on the Ce:Li4Ti5O12 particles to limit their grain growth. The coating is later removed to facilitate the Li+ diffusion during charge/discharge. The composition, structure, and morphology of the obtained samples are characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma elemental analysis, thermal gravimetric analysis, scanning electron microscopy, and transmission electron microscopy. The results confirm the particle-size tailoring effect induced by the carbon-coating. The size-tailored Ce:Li4Ti5O12 electrode demonstrates high reversible capacity of 164, 161, 158, 149, 136, and 116 mAh g−1 at 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, which are significantly improved from the pristine Li4Ti5O12. Moreover, it is also capable of maintaining 96% and 92% of the initial capacity at the high rate of 10C and 20C after 1000 cycles, exhibiting excellent cycling stability. Finally, we fabricate a full cell with LiFePO4 cathode, which delivers reversible capacity of 110 mAh g−1 at 5C with little capacity fading after 1200 cycles, confirming the outstanding electrochemical performance of size-tailored Ce:Li4Ti5O12 anode.

Enhanced electrochemical performance of Li4Ti5O12/carbon nanotubes/glucose composite as anode material for lithium ion batteries

Li4Ti5O12 (LTO)/carbon nanotubes (CNTs)/glucose (g) composite is synthesized via solid method followed by sonicating. The influences of carbon nanotubes and glucose additives on the microstructure and electrochemical performances of LTO are investigated. As-prepared LTO composited with 2.5 wt% CNTs and 2 wt% glucose (LTO/2.5CNTs/2 g) exhibits excellent electrochemical performances. On the one hand, LTO/2.5CNTs/2 g composite shows well dispersed between LTO particles and CNTs with width of 200–400 nm. On the other hand, with higher surface areas 45.8839 m2 g−1 and pore volume of 0.2036 ml g−1, the discharge capacity of LTO/2.5CNTs/2 g can reach 251.9 mAh g−1 at 20 mA g−1, while its discharge capacity still reaches 119.3 mAh g−1 at 2 A g−1. Additionally, LTO/2.5CNTs/2 g composite achieves initial discharge capacity of 173.2 mAh g−1 at 1 A g−1, stabilizing at 118.9 mAh g−1 after 1000 cycles. More importantly, its band gap is the least with Li+ diffusion coefficient 1.14 × 10−11 cm2 s−1.

A versatile method for grafting polymers onto Li4Ti5O12 particles applicable to lithium-ion batteries

We report a novel and versatile method of grafting polymers onto lithium titanium oxide (LTO) by dispersion-mediated interfacial polymerization. A myriad of polymers can be grafted by this method, and the hybrid-polymer particles are compatible with all kinds of binders used in lithium-ion batteries. This method is capable of producing thin and homogenous polymer films that are useful for battery applications. A coating of poly(styrene) effectively prevents degradation of the cell after float test without affecting performance at high C rates.

Electrochemical performance of single Li4Ti5O12 particle for lithium ion battery anode

Single particle measurement is a known characterization method for electrode materials. In a conventional single particle measurement, highly advanced techniques are necessary to electrically bring a microelectrode into contact with a single-particulate active material while observing with an optical microscope. Our measurement method doesn't require a high level of skill by using a “particle-current collector integrated microelectrode”, in which the single active material particle was directly-contacted on the tip of the microelectrode by platinum deposition. In this study, the intrinsic properties of a conventional Li4Ti5O12 (LTO) single particle were investigated by using the integrated microelectrode without any binder and carbon additives. Cyclic voltammograms and charge-discharge profiles at various temperatures between 10 and 40°C revealed that Li+ extraction (discharge) was faster than Li+ insertion (charge) because of the difference in Li+ diffusion into the single LTO particle, thereby exhibiting remarkable discharge capacity retention (>80%) even at 1000C and 10°C. Cycle performance at charge-discharge rate of 30C showed excellent reversibility, in which capacity retention and Coulombic efficiency were estimated to be 96.4% and 99.97%, respectively, even after 5000cycles.

Hierarchical macropore-mesoporous shell carbon dispersed with Li4Ti5O12 for excellent high rate sub-freezing Li-ion battery performance

The significant reduction in capacity and cyclability of lithium-ion batteries (LIBs) at low temperature is still limiting its application in cold climate. Limited literature has addressed the low temperature performance of LIB anodes, mostly restrict to low current performance showing low durability (<100 cycles). This is the first report of excellent durability in Li4Ti5O12-based composite cycling at a high current (10C) over 1000 cycles under sub-zero temperatures. We embed Li4Ti5O12 nanoparticles in hierarchical macropore-mesoporous shell carbon network (HCMS carbon) to form Li4Ti5O12/HCMS carbon nanocomposite. The HCMS carbon is an ideal support for Li4Ti5O12 to achieve excellent high rate sub-freezing LIB performance by providing short, intertwining Li-ion diffusion pathways between embedded Li4Ti5O12 particles and Li-ion reservoirs, and ample routes for continuous, multi-directional electron flow to Li4Ti5O12 particles. At −20 °C, the Li4Ti5O12/HCMS carbon composite delivers the highest literature-reported specific energy of 80 Wh/kg at a high specific power of 3000 W/kg. This work demonstrates our Li4Ti5O12/HCMS carbon composite can be a viable LIB anode material with fast and efficient Li-ion and electron transport active in sub-zero temperature operation.

Enhanced cyclic stability at elevated temperature of spinel LiNi0.5Mn1.5O4 by Li4Ti5O12 coating as cathode material for high voltage lithium ion batteries

The cyclic stability of LiNi0.5Mn1.5O4 at elevated temperature is a crucial factor for commercial Li-ion batteries. To improve the capacity retention of the spinel cathode material, surface modification has been widely recognized as one of the most effective approaches. In this work, a continuous and uniform layer assembled with nanoscale Li4Ti5O12 particles was coated on LiNi0.5Mn1.5O4 via hydrothermal method with moderate temperature. With a coating quantity of 0.5 wt%, the as-prepared LiNi0.5Mn1.5O4@ Li4Ti5O12 delivers an initial special discharge capacity of 141.2 mAh g−1 at 0.2 C and retention of 93.66% after 500 cycles at 1 C at room temperature, and it exhibits capacity retention of 97.03% after 140 cycles at 1 C at 55 °C. In addition to the protective effect against electrolyte, from observation on the surface feature during long term lithium insertion/extraction process, the Li4Ti5O12 coating layer suppresses the continuous growth of a dense and cathode electrolyte interfaces from the electrolyte decomposition.

Effective enhancement in rate capability and cyclability of Li4Ti5O12 enabled by coating lithium magnesium silicate

In terms of the unique features of good suspensibility in water, superior absorbability, adhensivity, cation exchangeability and rapid ion diffusion channels, lithium magnesium silicate (LMSO) might be an appropriate modifier for Li4Ti5O12 (LTO) by simply forming coating on LTO particles. According to a series of comparative experiments performed under various conditions, when the mixture of LTO and LMSO was roasted at 700 °C to form LMSO-coated LTO, the rate properties were significantly boosted (attaining cycling capacities of 160.2, 157.8, 155.8, 151.3 and 145.5 mAh g−1 with multiplying current density from 0.1 to 1.6 A g−1). Upon cycling at 0.5 A g−1 for 900 cycles, a capacity of 140.6 mAh g−1 was maintained. Compared to the pristine LTO, the markedly boosted rate properties and cyclability are ascribed to the LMSO coating for suppressing grain aggregation and growth, the optimized Li+ and electron transfer in electrolyte by interacting with LMSO, the enhanced electronic conductivity of LTO resulted from superficial co-doping of Mg2+ and Si4+, the meliorated ionic conductivity associating with the Li+ diffusion channels and cation exchangeability of LMSO, as well as the diminished polarization after the modification by LMSO.

In Situ Supramolecular Self-Assembly Assisted Synthesis of Li4Ti5O12–Carbon-Reduced Graphene Oxide Microspheres for Lithium-Ion Batteries

Li4Ti5O12 (LTO)-carbon (C)-reduced graphene oxide (rGO) microspheres are synthesized via in situ supramolecular self-assembly, combined with spray drying and high-temperature calcination. Dopamine can polymerize on the surface of Ti(OH)4 and form polydopamine, through which graphene oxide(GO) connects with Ti(OH)4 uniformly and tightly to form a homogeneous supramolecular sol system. During the high-temperature calcination, polydopamine is carbonized to carbon to connect LTO with rGO, so that the aggregation of rGO is inhibited, and small-sized LTO particles are obtained. The scanning electron microscopy (SEM) image shows that in the as-prepared LTO-C-rGO microspheres, LTO particles with diameters of ∼50 nm remained homogeneous and wrapped in a three-dimensional network built by the rGO nanosheets. Electrochemical measurements show that the LTO-C-rGO anode exhibits a high reversible capacity of 184 mAh g–1 at 1 C and a high capacity retention of 94.5% after 500 cycles at 20 C. The above excellent electrochemical performance benefits from the unique structure of LTO-C-rGO, which enhances the ion diffusion and facilitates electron transport.

Fabrication and performance of Li4Ti5O12/cotton-driven carbon fiber as anode for lithium-ion batteries

In this paper, we reported a simple, inexpensive, and green biomimetic technique for developing high-performance Li4Ti5O12 for lithium-ion batteries. Carbon-coated Li4Ti5O12 particles were synthesized by using cotton-driven carbon fiber as both a structural template and a biocarbon source. The conductive and uniform cotton-driven carbon fiber coated on the surface of the Li4Ti5O12 particles significantly improved the electrochemical performance of the composite, which exhibited a higher reversible capacity and a better rate capability than those of pure Li4Ti5O12. The average grain size of Li4Ti5O12/cotton fiber (CF) was approximately 200–400 nm, which was considerably smaller, more uniform, and regular than that of pure Li4Ti5O12. The initial charge capacity of the Li4Ti5O12/CF electrodes was 183.3 mAh g−1 at 100 mA g−1 (0.57 C). After 100 cycles, the electrodes retained a capacity of 152.9 mAh g−1, which was 30.6% higher than that of Li4Ti5O12 (117.1 mAh g−1). The superior electrochemical performance can be attributed to the improved ionic and electronic conductivities in the electrode produced by the uniform cotton-driven carbon fiber coating layer.

Li4Ti5O12 powders by spray-drying: influence of the solution concentration and particle size on the electrochemical properties

The lithium battery electrode compound Li4Ti5O12 was synthesized by calcination of precursor powders obtained through spray-drying of solutions prepared with titanium isopropoxide and lithium nitrate. X-ray diffraction and thermal analysis coupled to mass spectrometry show that single phase crystalline Li4Ti5O12 particles can be obtained after calcination at 800 °C for 2 hours. Decreasing the solution concentration leads to smaller particle sizes but also to an unexpected decrease of the electrochemical capacity, probably related to the presence of residual Li2TiO3. On the contrary, the capacity of the Li4Ti5O12 powder prepared with the high concentration solution can be increased from 150 mAh/g to 165 mAh/g (C/4 rate) by grinding. These results highlight the fact that smaller particles do not systematically display better performances for Li+ intercalation/desintercalation and confirm the need for a comprehensive approach including parameters such as crystallinity, phase purity or agglomeration.

Conductive PEDOT-decorated Li4Ti5O12 as next-generation anode material for electrochemical lithium storage

Spinel Li4Ti5O12 material has been regarded as the next-generation anode for lithium-ion batteries owing to its excellent safety and good structural stability. Nevertheless, the low electrical conductivity and bad Li+-ion diffusion efficiency of pristine Li4Ti5O12 greatly limit its wide applications in electrochemical energy storage. Herein, the nanosized Li4Ti5O12 crystals are prepared via a simple sol-gel method to shorten the diffusion pathway of Li+-ion. Meanwhile, the conductive PEDOT layer is adopted to modify the electrical conductivity of Li4Ti5O12. The PEDOT-coated Li4Ti5O12 composite is successfully prepared by using the in-situ polymerization method. Benefit from the advantages of nanosized Li4Ti5O12 particles and conductive PEDOT coating, the obtained electrode exhibits enhanced electrochemical performances. It can deliver the initial discharge capacities of 169.6 and 125.2 mAh g−1 at 0.1 and 20 C. These results demonstrate that the designed composite is a potential electrode for high-rate electrochemical lithium storage.

A facile way to prepare carbon-coated Li4Ti5O12 porous fiber with excellent rate performance as anode in lithium ion battery

Carbon is an economy and effective material for improving the electron conductivity of Li4Ti5O12, coating carbon on Li4Ti5O12 is commonly through the means of calcinating the mixture of titanium, lithium and organic compounds in an inert atmosphere, which needs a careful control to avoid the reduction of Ti4+ in Li4Ti5O12 by the in-situ formed carbon. In this work, a facile way is applied to fabricate carbon on Li4Ti5O12 by using filter paper to absorb the solution containing Ti(OC4H9)4 and LiAC with a calcination at 700 °C in air. The formation of carbon on Li4Ti5O12 mainly related with the swelling property of the crystalliferous region in cellulose fiber. TEM image shows Li4Ti5O12 particles have the average diameter about 100 nm, which are coated by a thin layer of carbon with the thickness around 5 nm, and Li4Ti5O12 particles connect with each other by carbon, forming porous fiber, which facilitates the transfer of electron and Li+. In comparison with Li4Ti5O12 synthesized by sol-gel method, Li4Ti5O12/C present superior rate capability with the discharge capacity of about 165 mAh g−1 at 0.2 C and 141 mAh g−1 at 20 C.

Enhanced lithium-storage performance of Li4Ti5O12 coated with boron-doped carbon layer for rechargeable Li-ion batteries

In this study, the B-doped carbon coating has been applied to enhance the lithium-storage performance of Li4Ti5O12 anode material for Li-ion batteries. The designed B-doped carbon improved Li4Ti5O12 composite (abbreviated as Li4Ti5O12@C-B) is successfully synthesized using a sol-gel approach followed by a microwave heating route. The XRD and HRTEM results demonstrate that the well-crystallized Li4Ti5O12 particles are uniformly coated with the B-doped carbon layer with a thickness of about several nanometers. The existence of boron doping in the carbon layer is also confirmed by XPS and EDX mapping. Compared with the undoped Li4Ti5O12@C, the Li4Ti5O12@C-B anode shows superior electrochemical performances such as higher reversible capacity and better cycling stability. The enhanced lithium-storage property can be attributed to the doped boron element which could bring many amazing improvements on the carbon coating. Therefore, this novel strategy of B-doped carbon coating can be widely used to improve the electronic conductivity of other electrode materials for electrochemical energy storage.