Li4Ti5O12 Research Articles

An Advanced Cell for Measuring In Situ Electronic Conductivity Evolutions in All‐Solid‐State Battery Composites

Ion and electron transport is of paramount importance for solid‐state technology and its limitation presently prevents the access to liquid cells performance. Herein, this work tackles this issue by proposing an easily implementable cell design enabling to follow the cathode composite's electronic conductivity evolution, in situ and during cycling. For proof of concept, distinct active material (AM) based composites are studied, namely LiCoO2 (LCO), LiNiO2, LiNi0.9Co0.1O2 (NC 9010), NMC 811, NMC 622, NMC 111 (NMC family: LiNi1‐yMnyCoyO2), and Li4Ti5O12 (LTO) mixed with Li6PS5Cl solid electrolyte (SE). This work shows the feasibility to track AM's phase transitions associated with changes in the material's electronic transport properties. Moreover, this work demonstrates the impact of the Ni content in the various layered oxides, on the interparticle loss of contact at high state‐of‐charge affecting electronic transport. Lastly, by tuning LTO particle size and morphology, this work shows the effect of primary and secondary particle size on the specific metal–insulator transition pertaining to this material. Altogether, this new testing cell opens‐up a broad spectrum of experimental possibilities aiming to access in situ mode key metrics to benefit the optimization of solid‐state batteries research.

Enabling the Operation of Highly Compatible LiI-3-Hydroxypropionitrile Small-Molecule Solid-State Electrolytes in Lithium Metal Batteries via Stepped-Amorphization Strategy.

Integrating the advantages of both inorganic ceramic and organic polymer solid-state electrolytes, small-molecule solid-state electrolytes represented by LiI-3-hydroxypropionitrile (LiI-HPN) inorganic-organic hybrid systems possess good interfacial compatibility and high modulus. However, their lack of intrinsic Li+ conduction ability hinders potential application in lithium metal batteries until now, despite containing LiI phase composition. Herein, inspired by evolution tendency of ionic conduction behaviors together with first-principles molecular dynamics simulations, we propose a stepped-amorphization strategy to break the Li+ conduction bottleneck of LiI-HPN. It involves three progressive steps of composition (LiI-content increasing), time (long-time standing), and temperature (high-temperature melting) regulations, to essentially construct a small-molecule-based composite solid-state electrolyte with intensified amorphous degree, which realizes efficient conversion from an I- to Li+ conductor and improved conductivity. As a proof, the stepped-optimized LiI-HPN is successfully operated in lithium metal batteries cooperated with Li4 Ti5 O12 cathode to deliver considerable compatibility and stability over 250 cycles. This work not only clarifies the ionic conduction mechanisms of LiI-HPN inorganic-organic hybrid systems, but also provides a reasonable strategy to broaden the application scenarios of highly compatible small-molecule solid-state electrolytes.

Highly Conductive Iodine and Fluorine Dual-Doped Argyrodite Solid Electrolyte for Lithium Metal Batteries

Sulfide-type argyrodite solid electrolytes (SEs) with halide doping have attracted serious interest. Although other halides such as Cl and Br have been found to enhance Li-ion transport in argyrodites, the direct synthesis of efficiently conductive Li6PS5I without postprocessing has rarely been investigated. In this work, we report the one-step synthesis of highly conductive Li6PS5I with an impressive ionic conductivity of 2.5 × 10–4 S cm–1 at room temperature through a solvent-based method. Moreover, by introducing F– to partially replace I–, hybrid-doped argyrodites Li6PS5FxI1–x (x = 0.25, 0.5, 0.75) have been synthesized. Li6PS5F0.25I0.75 achieves the highest conductivity of 3.5 × 10–4 S cm–1 due to the energetic preference for anion-disordering among F–/I– and S2–, which facilitate faster Li transport as supported by density functional theory (DFT) calculations. With higher F content in argyrodites, Li6PS5F0.75I0.25 displays the best electrochemical stability toward Li metal, as evidenced by long-term stable cycling in Li symmetric cells up to 1100 h. Solid-state Li metal batteries with an active cathode of Li4Ti5O12 (LTO) display an initial specific capacity of 140 mAh g–1 and remain at 105 mAh g–1 after 200 cycles, suggesting great battery cycling performance. This research has developed new compositions in the argyrodite SE family which could lead to advancements in the development of solid-state Li metal batteries.

Electrolyte contact changes nano-Li4Ti5O12 bulk properties via surface polarons

It is of general interest to combine the faradaic processes based high energy density of a battery with the non-faradaic processes based high power density of a capacitor in one cell. Surface area and functional groups of electrode materials strongly affect these properties. For the anode material Li4Ti5O12 (LTO), we suggest a polaron based mechanism that influences Li ion uptake and mobility. Here we show electrolytes containing a lithium salt induce an observable change in the bulk NMR relaxation properties of LTO nano particles. The longitudinal 7Li NMR relaxation time of bulk LTO can change by almost an order of magnitude and, therefore, reacts very sensitively to the cation and its concentration in the surrounding electrolyte. The reversible effect is largely independent of the used anions and of potential anion decomposition products. It is concluded that lithium salt containing electrolytes increase the mobility of surface polarons. These polarons and additional lithium cations from the electrolyte can now diffuse through the bulk, induce the observed enhanced relaxation rate and enable the non-faradaic process. This picture of a Li+ ion equilibrium between electrolyte and solid may help with improving the charging properties of electrode materials.

Ability of Li4Ti5O12 to suppress Li metal deposition under overpotential conditions confirmed by electrochemical surface plasmon resonance spectroscopy

Undesirable Li metal deposition on the negative electrode increases the risks associated with the use of Li-ion batteries. Generally, spinel-type lithium-titanium oxide Li4Ti5O12 (LTO)-based negative electrodes are well known as safe dendrite-free options, due to their higher working potential. However, the ability of LTO-based materials to prevent Li metal deposition has not been well confirmed under sudden overpotential application. This study examines the behavior of Li metal electrodeposition under various overpotential conditions for unloaded and LTO-loaded Cu electrodes. Electrochemical surface plasmon resonance spectroscopy (EC-SPR) is used as the optical diagnostic technique, owing to its sensitivity in detecting Li metal deposition. Li metal deposition is easily detected for the unloaded Cu electrode at overpotential of − 0.2 V (voltage) versus Li counter electrode (LiCE), whereas no Li metal deposition occurs for the LTO-loaded Cu electrode under the same overpotential. The safety of LTO is investigated by analyzing the reaction kinetics.

Improving electrochemical properties of Li4Ti5O12/TiO2 diphase anode materials via Co-Cl co-doping

The rapid development of highly durable electric vehicles has put forward higher requirements for lithium-ion batteries. Li4Ti5O12 (LTO) is widely studied owing to its long service life and safety. However, owing to their low electrical conductivity and diffusion, lithium ions have limited practical applications. In this study, Co-Cl co-doped LTO/TiO2 diphase (LTOT) nanosheets were prepared via the hydrothermal method. The synergistic effect of Co-Cl co-doping reduced the charge-transfer resistance of LTOT and increased the lithium-ion diffusion coefficient, thereby improving the dynamic behavior of the electrode material, which further enhances the rate capability and cycle performance of LTOT. The optimized LTOT:Co-Cl composite exhibited excellent cycle performance and rate capability (the ninth cycle reversible capacities were 253.8, 222.2, 200.1, 185.7, 169.9, 161.3, and 146.3 mAh·g−1 at the current density of 1, 2, 5, 10, 20, 30, and 50 C (1 C = 175 mA·g−1) rate, respectively). In addition, LTOT:Co-Cl maintained a capacity of 120 mAh·g−1 after 5000 cycles at 50 C with a retention rate of 83 %, indicating that the average decay rate per cycle is only 0.003 % during the long charge/discharge process.

Recycling of All-Solid-State Li-ion Batteries: A Case Study of the Separation of Individual Components Within a System Composed of LTO, LLZTO and NMC.

With the current global projection of over 130 million electric vehicles (EVs), there soon will be a need for battery waste management. Especially for all-solid-state lithium-ion batteries (lithium ASSBs), aspects of waste management and circular economy have not been addressed so far. Within such ASSBs, the use of solid-electrolytes like garnet-type Li6.5 La3 Zr1.5 Ta0.5 O12 (LLZTO) may shift focus on strategies to recover not only the transition metal elements but also elements like La/Zr/Ta. In this work, we present a two-step recycling approach using citric acid as the leaching agent to separate and recover the individual components of a model cell comprising of Li4 Ti5 O12 (LTO) anode, Li6.5 La3 Zr1.5 Ta0.5 O12 (LLZTO) garnet electrolyte and LiNi1/3 Mn1/3 Co1/3 O2 (NMC) cathode. We observe that by adjusting the concentration of citric acid, it was possible to separate the materials from each other without strong mixing of individual phases and also to maintain their principle performance characteristics. Thus, the process developed has a potential for upscaling and can guide towards considering separation capability of battery components in the development of lithium ASSBs.

Laser assisted method for synthesis Li4Ti5O12/polyether sulfone composite for lithium ion batteries anodic materials

Spinel Li4Ti5O12 (LTO) is a potential anode material for innovative high-power lithium-ion batteries (LIBs) because of its "zero strain" features during quick charging/discharging, extended cycle life, and elevated rate capability. However, LTO has limited application due to its poor ionic/electronic conductivity and slow ionic diffusion coefficient. In this work, LTO/polyether sulfone (PES) composite is synthesized via pulsed laser ablation in liquid media technique based on an infrared Nd:YAG nanosecond laser. The influences of laser ablation power were used to vary the particle sizes of the generated LTO nanoparticles on the formation of the LTO/PES structure, followed by the electrochemical performances of LTO. Various methods were used to investigate the composite's structural, optical, and morphological properties. The interactions between the polymer and nanoparticles, as well as the fine dispersion of NPs, were evident in the optical tests, which showed that the absorbance greatly improved and the energy band gap decreased. Also, the morphological images display the cubic shape of pure LTO NPs with varying particle sizes between 5 and 26 nm as the laser power changes. Furthermore, from XRD characterization, the intensity of this crystalline peak of PES decreases as a function of LTO wt. % increase without appearing of any other impurities. After that, the electrochemical performances were tested for all prepared samples, which showed that the as-prepared composite structure with a lower particle size exhibits excellent electrochemical performances. This result demonstrates that providing surface defects by forming Ti3+/Ti4+ pairs and oxygen vacancies in LTO is a successful method for increasing ion/electron mobility. This method can be applied to improve the battery efficiency of other substances with low ionic conductivities in the developed batteries.

Cr-doped LiNi0.5Mn1.5O4 derived from bimetallic Ni/Mn metal-organic framework as high-performance cathode for lithium-ion batteries

Metal-organic frameworks (MOFs) have potential applications in the field of electrochemical energy storage due to their unique characteristics, such as structural diversity, tolerability, and chemical homogeneity. LiNi0.5Mn1.5O4 (LNMO) is a great cathode material due to its wide working voltage, high energy density, and excellent rate capability. In this study, bimetallic Ni/Mn-MOFs and Cr-doped Ni/Mn-MOFs have been prepared by solvothermal reaction, which can be used as the precursor for the synthesis of pristine and Cr-doped LNMOs. The results indicate that the MOF-derived LNMO has better electrochemical behavior than the sample obtained from the conventional co-precipitation route. The resulting MOF-derived LNMO exhibits a high specific capacity (SC, 132.4 mAh/g at 0.2C), good rate ability (116.5 mAh/g at 10C), and remarkable long-cycle performance (80.1 % capacity retention for 200 cycles at 4C). More significantly, the full lithium-ion batteries (LIBs) incorporated with the MOF-derived LNMO as a cathode and Li4Ti5O12 (LTO) as an anode exhibit superior energy storage properties. This finding provides an efficient strategy for preparing high-performance LNMO cathode materials.

Three-Dimensional Network Microstructure Design of the Li4Ti5O12/rGO Nanocomposite as an Anode Material for High-Performance Lithium-Ion Batteries

At present, the wide commercial application of Li4Ti5O12 (LTO) is limited as an anode for lithium-ion batteries because of its poor conductivity and lower rate performance. In this paper, LTO nanoparticles were embedded in a reduced graphene oxide (rGO) conductive network by an in situ electrostatic self-assembly effect using a simple hydrothermal reduction method. The microstructure and electrochemical performance of the LTO/rGO composite were investigated. The highlighted results showed that LTO nanoparticles were combined with rGO nanosheets by a Ti–O–C covalent bond, which was more stable than other bonding methods. At the same time, the addition of rGO not only enriches the structure and increases the specific surface area but also effectively prevents the agglomeration of LTO. The higher conductivity of LTO nanoparticles was bestowed by the rGO three-dimensional (3D) network, causing structural stability and high electrochemical performance. The LTO/rGO composite has high first discharge capacity (643.9 mAh/g at 0.5C), remarkable rate performance (290 mAh/g at 10C), and excellent cycle stability (271.7 mAh/g after the 1000th cycle at 10C) when tested in a half battery. Furthermore, it has higher discharge capacity (181.8 mAh/g at 1C, the first Coulombic efficiency was 90.1%) and excellent cycle stability (142.8 mAh/g after 500 cycles at 20C) when assembled into a full battery as the anode with commercial LiFePO4 (LFP) as the cathode. The lithium storage mechanism of the LTO/graphene composite was further discussed by first-principles calculations. With the addition of graphene to LTO, the electron transport ability was improved and the diffusion energy barrier was reduced. This made the composite expected to become a promising anode material for lithium-ion batteries.

A Separator with Double Coatings of Li4 Ti5 O12 and Conductive Carbon for Li-S Battery of Good Electrochemical Performance.

The market demand for energy pushes researchers to pay a lot of attention to Li-S batteries. However, the 'shuttle effect', the corrosion of lithium anodes, and the formation of lithium dendrites make the poor cycling performances (especially under high current densities and high sulfur loading) of Li-S batteries, which limit their commercial applications. Here, a separator is prepared and modified with Super P and LTO (abbreviation SPLTOPD) through a simple coating method. The LTO can improve the transport ability of Li+ cations, and the Super P can reduce the charge transfer resistance. The prepared SPLTOPD can effectively barrier the pass-through of polysulfides, catalyze the reactions of polysulfides into S2- , and increase the ionic conductivity of the Li-S batteries. The SPLTOPD can also prevent the aggregation of insulating sulfur species on the surface of the cathode. The assembled Li-S batteries with the SPLTOPD can cycle 870 cycles at 5 C with the capacity attenuation of 0.066% per cycle. When the sulfur loading is up to 7.6 mg cm-2 , the specific discharge capacity at 0.2 C can reach 839 mAh g-1 , and the surface of lithium anode after 100 cycles does not show the existence lithium dendrites or a corrosion layer. This work provides an effective way for the preparation of commercial separators for Li-S batteries.

Investigation of structural, optical, and electrochemical properties of niobium-doped Li4Ti5O12 for high-performance aqueous capacitor electrode

In this study, nanocrystalline niobium-doped lithium titanate Li4Ti5O12 (LTO) was successfully synthesized with various stoichiometric ratios (x = 0, 0.025, 0.05, 0.075, 0.1) using a niobium ethoxide precursor via the solid-state synthesis method. X-ray diffraction spectroscopy results revealed that the synthesized samples possess a spinel structure without any impurities, and lattice constants expanded from 8.357 Å to 8.363 Å as the concentration of niobium ions increased. Scanning electron microscopy (SEM) analysis demonstrated that particle sizes ranged from 1.13 to 1.56 μm. The smallest particle size was observed in the LTO-Nb-0.075 sample. The maximum absorptions were detected in the ultraviolet region, and the band gaps of Nb-doped Li4Ti5-xNbxO12 (x = 0, 0.025, 0.05, 0.075, 0.1) were determined using Tauc plots. These results showed that the band gaps of Nb-doped LTO were lowered compared to pure LTO, suggesting enhanced electron conductivity. X-ray photoelectron spectroscopy (XPS) measurements confirmed that the band gaps of Nb-doped samples decreased as the formation of oxygen vacancies and Ti3+ ions increased due to Nb5+ substitution. All synthesized samples displayed well-defined redox peaks in pairs during the cyclic voltammetry (CV) measurement. The optimal stoichiometric ratio for doping lithium titanate was found to be x = 0.075, as it yielded the highest specific capacitance of 3.59 F/g and the lowered band gap value of 3.13 eV. Therefore, this study provides further encouragement for applying LTO electrodes in aqueous capacitors and electrical uses.

High‐Pressure Induction and Quantitative Regulation of Oxygen Vacancy Defects in Lithium Titanate

AbstractInspired by the functional properties of ion defect induction and charge compensation in defect engineering, these methods are expected to be an effective strategy to solve the constraints of Li4Ti5O12 (LTO) inherent conductivity and diffusion dynamics, and further improve battery rate performance. The oxygen vacancy (OV) content in LTO can be controlled quantitatively by high‐pressure induction using the high‐pressure and high‐temperature (HPHT) method. In addition, the relationship between the electrochemical properties and OV is further explored. The theoretical calculations indicate that the OV defects cause the electrons to delocalize into the conduction band of the LTO, and thus fundamentally improve the intrinsic conductivity. In particular, the high‐pressure quenching strategy of HPHT causes LTO to instantly produce crack holes with massive crystalline layers, which can be regarded as storage for the electrolyte to facilitate ion diffusion. The fabricated LTO anodes containing OVs compensate for the limitation of the poor rate performance with a capacity of 176 mAh g−1 at 20 C. Pressure‐induced OV defects not only open up a new perspective in the field of lithium‐ion batteries (LIBs), but also provide a certain degree of freedom for the functional design characteristics of defect engineering.

Converting Nafion into Li+ -Conductive Nanoporous Materials.

Sulfonated polymers have long been used as proton-conducting materials in fuel cells, and their ionic transport features are highly attractive for electrolytes in lithium-ion/metal batteries (LIBs/LMBs). However, most studies are still based on a preconceived notion of using them directly as polymeric ionic carriers, which precludes exploring them as nanoporous media to construct efficient lithium ions (Li+ ) transport network. Here, effective Li+ -conducting channels realized by swelling nanofibrous Nafion is demonstrated, which is a classical sulfonated polymer in fuel cells. The sulfonic acid groups, interact with LIBs liquid electrolytes to form porous ionic matrix of Nafion and assist partial desolvation of Li+ -solvates to further enhance Li+ transport. Li-symmetric cells and Li-metal full cells (Li4 Ti5 O12 or high-voltage LiNi0.6 Co0.2 Mn0.2 O2 as a cathode) with such membrane show excellent cycling performance and stabilized Li-metal anode. The finding provides a strategy to convert the vast sulfonated polymer family into efficient Li+ electrolyte, promoting the development of high-energy-density LMBs.

Temperature effects on electrochemical performance of Li4Ti5O12

Li4Ti5O12(LTO) is one of the most popular [Formula: see text]-storage anode materials. However, the influences of different operating temperatures on the electrochemical performance of LTO and the underlying mechanisms are still unclear. Herein, we systematically investigate its temperature-dependent electrochemical performance, electrochemical kinetics, and crystal-structural evolution at −10[Formula: see text]C, [Formula: see text]C, [Formula: see text]C, [Formula: see text]C, and [Formula: see text]C. When the operation temperature increases from −10[Formula: see text]C to [Formula: see text]C, more intensive electrolyte decomposition increases the irreversible capacity in the first cycle, which decreases the initial Coulombic efficiency. Meanwhile, the electrochemical kinetics becomes faster, leading to reduced electrode polarization, faster [Formula: see text]Transport, and higher rate capability. Finally, the maximum unit-cell-volume shrinkage enlarges, resulting in the decay of the cyclic stability. However, when the temperature further rises to 60°C, the rate capacity and cyclic stability rapidly decay due to the severe electrolyte decomposition catalyzed by [Formula: see text] and the formation of thick solid electrolyte interface (SEI) films.

Sodium Niobate with a Large Interlayer Spacing: A Fast-Charging, Long-Life, and Low-Temperature Friendly Lithium-Storage Material.

Niobate Li+ -storage anode materials with shear ReO3 crystal structures have attracted intensive attention due to their inherent safety and large capacities. However, they generally suffer from limited rate performance, cyclic stability, and temperature adaptability, which are rooted in their insufficient interlayer spacings. Here, sodium niobate (NaNb13 O33 ) micron-sized particles are developed as a new anode material owning the largest interlayer spacing among the known shear ReO3 -type niobates. The large interlayer spacing of NaNb13 O33 enables very fast Li+ diffusivity, remarkably contributing to its superior rate performance with a 2500 to 125mAg-1 capacity percentage of 63.2%. Moreover, its large interlayer spacing increases the volume-accommodation capability during lithiation, allowing small unit-cell-volume variations (maximum 6.02%), which leads to its outstanding cyclic stability with 87.9% capacity retention after as long as 5000 cycles at 2500mAg-1 . Its cyclic stability is the best in the research field of niobate micron-sized particles, and comparable to that of "zero-strain" Li4 Ti5 O12 . At a low temperature of -10°C, it also exhibits high rate performance with a 1250 to 125mAg-1 capacity percentage of 65.6%, and even better cyclic stability with 105.4% capacity retention after 5000 cycles at 1250mAg-1 . These comprehensively good electrochemical results pave the way for the practical application of NaNb13 O33 in high-performance Li+ storage.

A Novel Graphene Based Bi-Function Humidity Tolerant Binder for Lithium-Ion Battery.

Binders play a critical role in rechargeable lithium-ion batteries (LIBs) by holding granular electrode materials, conductive carbons, and current collectors firmly together to form and maintain a continuous electron conduction phase with sufficient mechanical strength. In the commercial LIBs, the dominant binder is polyvinylidene fluoride for the cathode (LiCoO2 , LiFePO4 , LiNix Coty Mnz O2 , etc.) and carboxyl methylcellulose/styrene-butadiene rubber for the anode (graphite and Li4 Ti5 O12 ). However, these polymer binders have several drawbacks, particularly, a lack of electronic and lithium-ion conductivities. Here, a novel organic/inorganic hybrid conductive binder (LAP-rGO) for both the anode and cathode of LIBs is reported. The binder consists of 2D reduced graphene oxide sheets with anchored long alkane chains. Electrodes prepared using this binder exhibit sufficient high bond strength, fast electrolyte diffusion, high rate charge/discharge performance, and excellent cycling stability. Around 130 mAh g-1 capacity enhancement at 5C is demonstrated for LiFePO4 and Li4 Ti5 O12 electrodes owing to the combined improvement in electron and lithium ion transportation. LAP-rGO bond graphite anode shows specific capacity beyond its theoretical value. Electrode slurries prepared using this new binder have superior processing and coating properties that can be prepared under a high humidity and dried using less energy.

Two-Dimensional Films Based on Graphene/Li4Ti5O12 and Carbon Nanotube/Li4Ti5O12 Nanocomposites as a Prospective Material for Lithium-Ion Batteries: Insight from Ab Initio Modeling.

The combination of spinel Li4Ti5O12 (LTO) with carbon nanostructures, such as graphene (G) and carbon nanotubes (CNTs), provides all of the required properties for modern chemical power sources such as Li-ion batteries (LIBs) and supercapacitors (SCs). G/LTO and CNT/LTO composites demonstrate a superior reversible capacity, cycling stability, and good rate performances. In this paper, an ab initio attempt to estimate the electronic and capacitive properties of such composites was made for the first time. It was found that the interaction between LTO particles and CNTs was higher than that with graphene due to the larger amount of transfer charge. Increasing the graphene concentration raised the Fermi level and enhanced the conductive properties of G/LTO composites. For CNT/LTO samples, the radius of CNT did not affect the Fermi level. For both G/LTO and CNT/LTO composites, an increase in the carbon ratio resulted in a similar reduction in quantum capacitance (QC). It was observed that during the charge cycle in the real experiment, the non-Faradaic process prevailed during the charge cycle, while the Faradaic process prevailed during the discharge cycle. The obtained results confirm and explain the experimental data and improve the understanding of the processes occurring in G/LTO and CNT/LTO composites for their usages in LIBs and SCs.

Vacancy-clusters in-situ induced via microwave-irradiation enable high-durability and capacitor-level rate li-ion storage

The minutes-level charging capability is an actually-inevitable result of the contemporary battery industry, which thus demands the highly-effective battery electrodes with excellent electrode kinetics. Here, we newly-design the novel electrode nanomaterials via a rapid microwave-hydrothermal method to in-situ grown the oxygen-vacancy Li4Ti5O12 (LTO) nanoclusters on the functionalized carbon nanotubes (FCNTs). Density functional theory (DFT) studies discover that the enriched vacancies indeed tune the electron localization at atom-level, which then well-influences the corresponding state of densities, resulting in the superior electron conductivity and high Li+ affinity. In addition, the nano-level vacancy-clusters, groupings of vacancy-LTO nanoparticles, provide a strong in-built electric-field micro-environment. Combined with highly-effective electron highway of FCNTs, the resultant electrode delivers a remarkable capacitor-level rate-ability (store ∼ 55.5% of the theoretical capacity only within 2 min) and long-lived durability (2000 cycles at 2C with an ultralow decay rate of 0.003% per cycle). Furthermore, we have respectively developed pouch-type and fiber-shape full-battery based on above LTO-based anode, both of which have high mechanical properties and stable capacity delivery. This study provides promising prospects for LTO-based materials in fast-charging and flexible batteries.

Enhanced Electrochemical Performance of Rare-Earth Metal-Ion-Doped Nanocrystalline Li4Ti5O12Electrodes in High-Power Li-Ion Batteries

A comprehensive and comparative exploration research performed, aiming to elucidate the fundamental mechanisms of rare-earth (RE) metal-ion doping into Li4Ti5O12 (LTO), reveals the enhanced electrochemical performance of the nanocrystalline RE-LTO electrodes in high-power Li-ion batteries. Pristi ne Li4Ti5O12 (LTO) and rare-earth metal-doped Li4-x/3Ti5-2x/3LnxO12 (RE-LTO with RE = Dy, Ce, Nd, Sm, and Eu; x ≈ 0.1) nanocrystalline anode materials were synthesized using a simple mechanochemical method and subsequent calcination at 850 °C. The X-ray diffraction (XRD) patterns of pristine and RE-LTO samples exhibit predominant (111) orientation along with other characteristic peaks corresponding to cubic spinel lattice. No evidence of RE-doping-induced changes was seen in the crystal structure and phase. The average crystallite size for pristine and RE-LTO samples varies in the range of 50-40 nm, confirming the formation of nanoscale crystalline materials and revealing the good efficiency of the ball-milling-assisted process adopted to synthesize nanoscale particles. Raman spectroscopic analyses of the chemical bonding indicate and further validate the phase structural quality in addition to corroborating with XRD data for the cubic spinel structure formation. Transmission electron microscopy (TEM) reveals that both pristine and RE-LTO particles have a similar cubic shape, but RE-LTO particles are better interconnected, which provide a high specific surface area for enhanced Li+-ion storage. The detailed electrochemical characterization confirms that the RE-LTO electrodes constitute promising anode materials for high-power Li-ion batteries. The RE-LTO electrodes deliver better discharge capacities (in the range of 172-198 mAh g-1 at 1C rate) than virgin LTO (168 mAh g-1). Among them, Eu-LTO provides the best discharge capacity of 198 mAh g-1 at a 1C rate. When cycled at a high current rate of 50C, all RE-LTO electrodes show nearly 70% of their initial discharge capacities, resulting in higher rate capability than virgin LTO (63%). The results discussed in this work unfold the fundamental mechanisms of RE doping into LTO and demonstrate the enhanced electrochemical performance derived via chemical composition tailoring in RE-LTO compounds for application in high-power Li-ion batteries.