Pristine Li4Ti5O12 Research Articles

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.

Cd-Doped Li4–xCdxTi5O12 (x = 0.20) as a High Rate Capable and Stable Anode Material for Lithium-Ion Batteries

Li4Ti5O12 (LTO), an excellent anode for lithium-ion batteries (LIBs), suffers from low electronic conductivity, limiting its high-power rate application. An aliovalent metal ion doping strategy that tunes the electronic/ionic conductivity can mitigate this issue. In this work, we investigated a series of Cd2+ dopings on the Li4–xCdxTi5O12 (x = 0, 0.05, 0.10, and 0.20) anode material by considering its effect on structural and electrochemical performance in Li- and Na-ion batteries. Combined Rietveld refinement and X-ray absorption spectroscopy (XAS) analysis explicitly identified Cd2+ doping into the Li(8a) tetrahedral site of the cubic spinel LTO structure. According to high-resolution powder diffraction (HRPD), scanning electron microscopy (SEM), 4-point probe, and X-ray photoelectron spectroscopy (XPS), an increase in Cd2+ doping from 5 to 20% at the Li (8a) site in the LTO results in a reduction in particle size, an expansion of lattice, an increase in conductivity, and an increase in Ti3+ content to Ti4+ ratio. High-resolution scanning transmission electron microscopy (HR-STEM) confirms that cadmium ions are interstitially doped in the LTO structure. Compared to the pristine LTO electrode in the Li half cell, the Li3.80Cd0.20Ti5O12 (Cd0.20-LTO) electrode showed a significant improvement in capacity at high rates and excellent cycling performance. The improvement in performance for Cd0.20-doped LTO is a consequence of the reduction in the diffusion path and the faster Li-ion kinetics. Therefore, this Cd-doped LTO series of electrodes demonstrates advantageous features for Li-ion battery systems.

Enhancing the rate performances of Li4Ti5O12 by Mo4+ doping and MoO2-Mo dispersed on the surface

Li4Ti5O12 is considered as a promising anode material because of its high safety and excellent cycling stability. However, its practical application is limited due to the poor rate performances. This problem can be effectively compensated by introducing highly conductive materials and/or doping. Herein, Mo4+ doped Li4Ti5O12/MoO2-Mo composites were prepared by the simple solid-state method under a reducing atmosphere with MoO3 as an additive. MoO3 is reduced to MoO2 and Mo mixture under the heating atmosphere. From the results of XRD after cell refinement, it is inferred that only a small part of Mo4+ ions are doped into the lattice of lithium titanate. XRD, STEM, EDS mapping and XPS reveal that particles with a size of only tens of nanometers adhered to the surface of lithium titanate should be MoO2/Mo mixture. The electrochemical results of EIS and CV show that the modified sample display a lower charge transfer resistance and a larger diffusion coefficient of lithium ions as a result of the combined effects of Mo4+ doping and interfacial modification. Compared with pristine Li4Ti5O12 prepared under the same atmosphere, the modified Li4Ti5O12 exhibits a capacity of approximately 140 mAh·g−1 under a high current density of 1.7 A·g−1, which is about 20 mAh·g−1 higher than the former one. And the modified Li4Ti5O12 has better capacity retention after 500 cycles at 5 C, which may be related with the surface modification.

Synthesis, characterisation and electrochemical evaluation of lithium titanate anode for lithium ion cells

Lithium titanate, Li4Ti5O12 (LTO), a promising anode material for high power lithium ion (Li-ion) cells, was synthesised by sol-gel method using hydrated titania and lithium carbonate as precursors. The synthesised material was characterised by Fourier-transform infrared spectroscopy and X-ray diffraction methods. The morphology of the material was studied by scanning electron microscopy. The electrochemical evaluation of LTO electrode in Li-ion cells was carried out by assembling LTO electrode versus Li metal as counter electrode in half cell. The cell was subjected to initial charge-discharge cycles at C/10 rate and then tested at different rates viz. C/5, C/2, 1C, 2C, 5C, 10C and 20C. The specific capacity at these rates was 170, 167, 165, 164, 161, 160, 160 and 155 mAh/g, respectively. The columbic efficiency of the cell was close to 100% at these rates. Herein, we demonstrate that a pristine LTO formed by simple sol-gel method can retain more than 90% of the capacity at high current rate of 20C.

Electrochemical characteristics of Ge incorporated Li4Ti5O12 as an anode for Li-ion battery applications

Lithium titanate (LTO) is recognized to be a promising anode material for lithium-ion batteries due to its remarkable structural benefits. However, the poor electronic conductivity and lower capacity hindered its widespread commercialization. To analyze the possibility of enhancing the performance of LTO through doping, pristine LTO (Li4Ti5O12), as well as germanium (Ge4+) doped LTO (Li4GexTi5-xO12; x = 0.1 and 0.2) were synthesized by conventional solid-state reaction. Characterizations confirmed the partial replacement of Ti4+ by Ge4+ evenly throughout the material without making any stress or deformation to the host lattice. The electrochemical characterization results established that the presence of germanium effectively reduced the cell impedance as well as improved Li+ ion diffusion. The doping was able to enhance capacity compared to pristine LTO. The best of the doped compositions (Li4Ge0.1Ti4.9O12) was able to deliver a capacity of 159 mA h g−1 at 0.1 C rate and 145 mA h g-1 at 1 C with more than 85 % retention after 300 cycles.

Improved Electrochemical Properties of Li4Ti5O12 Nanopowders (NPs) via Addition of LiAlO2 and Li6SiON Polymer Electrolytes, Derived from Agricultural Waste

Li4Ti5O12 (LTO) has received considerable interest as an alternate anode material for high power density batteries for large scale applications. However, LTO suffers from poor Li+ diffusivity and poor electronic conductivity, resulting in capacity loss and poor rate performance. Here we demonstrate a facile synthesis of LTO NPs using liquid-feed flame spray pyrolysis (LF-FSP) which provides high surface area (∼38 m2/g) spinel structure LTO NPs with average particle sizes (APSs) of 45 ± 0.3 nm. Pristine LTO-Li half-cells exhibit reversible capacity of 70 mAh/g at 10 C. In this study, we show that mixing LiAlO2 NPs (5 wt %) and Li6SiON polymer precursor (10 wt %) with pristine LTO via ball-milling and ultrasonication followed by tape casting enhances the LTO rate performance providing reversible capacity of ∼217 mAh/g at 5 C over 500 cycles. The Li6SiON polymer electrolyte is synthesized from rice hull ash (RHA), an agricultural waste, providing a green synthetic approach to electrode coating materials. CV and EIS studies indicate that adding the solid and polymer electrolytes reduces charge-transfer resistance and electrode polarization, enhancing both reversibility and the LTO Li+ diffusion coefficient from 4.6 × 10–14 to 2.7 × 10–12 cm2/s.

Solid coated Li4Ti5O12 (LTO) using polyaniline (PANI) as anode materials for improving thermal safety for lithium ion battery

In generally, the thermal behaviour of cathode and electrolyte are the major concerns for the safety of lithium-ion battery, In contrast to rare attention on thermal effects of anode materials. In this work, Li4Ti5O12/polyaniline (PANI@LTO) composites were synthesized by solid coating method. The SEM/TEM images of the PANI@LTO composites reveal that the PANI nanorods were crashed and wrapped around the LTO particles. FTIR analysis shows the interaction between the NH groups and the surface of the LTO material by mechanical action, which cause changes of oxidation state of PANI in the PANI@LTO composites, compared with the pristine PANI materials. As an anode material for lithium ion battery, the PANI coatings have improved the rate performance of the LTO materials. The specific capacities of the composite at rates of 2C and 5C are 137.8, and 117.2 mAhg−1, which are higher than those of the pristine LTO (99.5 and 77.6 mAhg−1, respectively) materials. In addition, the PANI@LTO composites show better cycling stability at 2C rates, after 100 cycles maintained 74.3%, compared to 60.4% of the pristine LTO materials. For thermal behaviour, the test was conducted under 60 °C at 2C rate, the initial capacity of the PANI@LTO composites was 152.5 mAhg−1 that is higher than the value of 137.8 mAhg−1at room temperature. However, the pristine LTO materials show similar initial capacity with that at room temperature. In addition, the PANI@LTO composites maintain better thermal stability, the capacity of the PANI@LTO composites were retained 83.2% after 80 cycles at 60 °C, compared to 54% loss on the LTO electrode under same condition. These results suggest that PANI might be a promising material to improve capacity and benefit thermal safety of lithium ion battery.

Influence of Mechanical Processing and the Procedure Used to Introduce a Carbon Material on the Electrochemical Properties of Li4Ti5O12/C Composites

Li4Ti5O12/C anode materials of different particle size have been prepared by a sol–gel process, followed by mechanical processing in a planetary mill. Carbon was introduced both by an in situ process and by mechanically mixing lithium titanate with carbon black (Timcal). The materials thus prepared have been characterized by X-ray diffraction, electron microscopy, and low-temperature nitrogen adsorption measurements and electrochemically tested. The decrease in the particle size of Li4Ti5O12 with increasing milling rate is larger in the case of the composites containing carbon black (Timcal). At a low charge/discharge rate (0.1C), the electrochemical capacity of the composites processed in a planetary mill at rotation rates of ≤400 rpm exceeds that of the pristine Li4Ti5O12. At high current densities (18C), the Li4Ti5O12/carbon black (Timcal) composite processed at 200 rpm exhibits the highest electrochemical capacity (107 mAh/g).

The synthesis and characterizations of Li4Ti5O12–CNTs anode material

An anode material with Li4Ti5O12 nanocrystals entangled by carbon nanotubes is prepared by polymerization of titanium tetra-isopropoxide with ethylene glycol in the presentence of carbon nanotubes. The resulted polymer is hydrolyzed in LiOH/H2O solution, and then thermally decomposed to obtain the topic anode material. The characterizations show that the synthesis method yields a type of material that has both of high electronic conductivity and high lithium ion diffusion rate. The material has stable deep discharge capability (down to 0.01 V), high specific capacity (237 mAhg−1 at 0.30 Ag-1), and long cycling life time (254 mAhg−1 at 0.10 Ag-1, more than 500 discharge/charge cycles). High specific capacities of 258 and 158 mAhg−1 are obtained at current densities of 0.10 and 3.00 Ag-1, respectively. The deep discharge capability of the material offers an average voltage below 1.0 V (vs metal Li), which is lower than that of pristine Li4Ti5O12 (1.55 V).

Insight into effects of graphene and zinc oxide in Li4Ti5O12 as anode materials for Li-ion full-cell battery

Programmable design of nanocomposites of Li4Ti5O12 (LTO) conducted through hydrothermal route in the presence of ethylenediamine as basic and capping agent. In this work, effect of ZnO and Graphene on the Li4Ti5O12 based nanocomposites as anode materials investigated for Li-Ion battery performances. The full cells battery assembled with LTO based nanocomposites on Cu foil as the anode electrode and commercial LMO (LiMn2O4) on aluminum foil as cathode electrode. X-Ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), along with Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission electron microscopy (TEM) images was applied for study the composition and structure of as-prepared samples. The electrochemical lithium storage capacity of prepared nanocomposites was compared with pristine LTO via chronopotentiometry charge-discharge techniques at 1.5–4.0 V and current rate of 100 mA/g. As a result, the electrode which is provided by LTO/TiO2/ZnO and LTO/TiO2/graphene nanocomposites provided 765 and 670 mAh/g discharge capacity compared with pristine LTO/TiO2 (550 mAh/g) after 15 cycles. Based on the obtained results, fabricated nanocomposites can be promising compounds to improve the electrochemical performance of lithium storage.

Enhancing Lithium Storage Performances of the Li4Ti5O12 Anode by Introducing the CuV2O6 Phase.

The low electronic conductivity of spinel-structured Li4Ti5O12 could be improved by introducing CuV2O6. Herein, several Li4Ti5O12/CuV2O6 composites with different CuV2O6 contents have been successfully prepared by a facile liquid-phase dispersion technique. The amount of CuV2O6 in composites is shown to affect the particle size and electrochemical performances of Li4Ti5O12. The Li4Ti5O12/CuV2O6 composite prepared with a 5 wt % CuV2O6 content (referred to as 5 wt % Li4Ti5O12/CuV2O6) exhibits the best electrochemical performances among all the Li4Ti5O12/CuV2O6 composites. The initial discharge/charge capacities of the 5 wt % Li4Ti5O12/CuV2O6 composite reach 241.1/199.8 mAh g-1 and retain at 136.8/135.7 mAh g-1 over 500 cycles at 30 mA g-1 between 1.0 and 3.0 V. In addition, initial discharge/charge capacities of the 5 wt % Li4Ti5O12/CuV2O6 composite amount to 129.8/90.5 mAh g-1 even at 1200 mA g-1 with maintained discharge/charge capacities of 71.1/71.1 mAh g-1 over 2500 cycles, which are superior to the pristine Li4Ti5O12 in all cases. The detailed electrode kinetic analysis reveals that the introduction of the CuV2O6 phase can enhance the lithium-ion transferring rate and cycling stability of Li4Ti5O12. The enhanced lithium-storage mechanism of the 5 wt % Li4Ti5O12/CuV2O6 composite is clarified by in situ X-ray diffraction (XRD) analysis. The acquired data confirms that in situ formation of small amounts of metallic Cu during discharge/charge processes highly enhance the electronic conductivity and decreases the charge-transfer resistance of Li4Ti5O12. In sum, the as-obtained 5 wt % Li4Ti5O12/CuV2O6 composite has potential for future construction of high-rate and long-lifespan anode materials for Li-ion batteries. The work also provides an innovative route to improve electrochemical performances of Li4Ti5O12.

Solution-Based, Anion-Doping of Li4 Ti5 O12 Nanoflowers for Lithium-Ion Battery Applications.

Solution-based, anionic doping represents a convenient strategy with which to improve upon the conductivity of candidate anode materials such as Li4 Ti5 O12 (LTO). As such, novel synthetic hydrothermally-inspired protocols have primarily been devised herein, aimed at the large-scale production of unique halogen-doped, micron-scale, three-dimensional, hierarchical LTO flower-like motifs. Although fluorine (F) doping has been explored, the use of chlorine (Cl) dopants is the primary focus here. Several experimental variables, such as dopant amount, lithium hydroxide concentration, and titanium butoxide purity, were probed and perfected. Furthermore, the Cl doping process did not damage the intrinsic LTO morphology. The analysis, based on interpreting a compilation of SEM, XRD, XPS, and TEM-EDS results, was used to determine an optimized dopant concentration of Cl. Electrochemical tests demonstrated an increased capacity via cycling of 12 % for a Cl-doped sample as compared with pristine LTO. Moreover, the Cl-doped LTO sample described in this study exhibited the highest discharge capacity yet reported at an observed rate of 2C for this material at 143mAh g-1 . Overall, these data suggest that the Cl dopant likely enhances not only the ion transport capabilities, but also the overall electrical conductivity of our as-prepared structures. To help explain these favorable findings, theoretical DFT calculations were used to postulate that the electronic conductivity and Li diffusion were likely improved by the presence of increased Ti3+ ion concentration coupled with widening of the Li migration channel.

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

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 of this work is to replace expensive Co with Mg and also to exploit advantages of both MCO and LTO. Three samples of MCO/LTO particles with different MCO proportion have various average particle sizes of 38.1, 56.9, and 58.5 nm, confirmed by scanning electron microscopy. Electrochemical studies show that a MCO/LTO anode offers a discharge capacity of ca. 300 mAh g−1, which is two times higher than that achieved by pristine LTO. The MCO/LTO anode also retains 75% of its initial capacity, even if the discharge rate is increased to 5 C. Cyclic stability test reveals that the composite anode still maintains nearly 85.5% of its initial capacity after 150 cycles. Electrochemical impedance spectroscopy indicates that the equivalent series resistance of MCO/LTO electrodes is significantly lower than that of LTO, i.e., from 35.5 to 9.9 Ω. The enhanced performance of the composite electrodes can be attributed to its improved conductivity as well as to the surface modification of LTO particles by MCO nanoparticle deposition which leads to increased number of active sites on the former.

Phase transformation of spinel Li4Ti5O12 to anatase TiO2 by catalytic delithiation

The metal oxides were derived from lithium metal oxides through the phase transformation of a lithium metal oxide to metal oxide by catalytic delithiation using silesquioxane-coated lithium metal oxide as a precursor. The metal oxide was gradually formed from the surface of the lithium metal oxide contacting with silesquioxane through the phase transformation. Lithium silicate (Li2SiO3) was subsequently formed by the reaction between lithium and silesquioxane. Detailed characterizations were performed using spinel Li4Ti5O12. Li4Ti5O12/TiO2 composites with three identifiable areas: a core (Li4Ti5O12), shell (TiO2), and coating layer (Li2SiO3) were derived by the simple thermal treatment of silesquioxane-coated lithium metal oxide in inert gas. During the thermal treatment, the silesquioxane coating layer was formed owing to the phase transformation of spinel Li4Ti5O12 to anatase TiO2. In addition, it sequentially reacted with lithium while forming an Li2SiO3 coating layer. TiO2 hydrogenation was further induced, which had Ti3+ sites and oxygen vacancies. The Li2SiO3-coated Li4Ti5O12/TiO2 composite exhibited significantly improved specific capacity, rate capability, and cycling stability, in comparison to pristine Li4Ti5O12. The improved electrochemical properties of the composite can be attributed to the following factors. (1) The phase transformation of spinel Li4Ti5O12 to anatase TiO2 increased the specific capacity of the composite because anatase TiO2 has a higher theoretical capacity than spinel Li4Ti5O12. (2) TiO2 hydrogenation increased the electronic and ionic conductivities by introducing Ti3+ sites and oxygen vacancies. (3) The Li2SiO3 coating layer suppressed gas production by protecting the composite surface from the electrolytes.

Ni and F co-modification to enhance the electrochemical properties of Li4Ti5O12 anode materials for lithium-ion batteries

As a negative electrode material, the main drawbacks of Li4Ti5O12 (LTO) are its low electric conductivity and poor Li-ion diffusion coefficient. Fortunately, elements modification to address these problems is an effective method. Herein, we firstly report Ni and F co-modified LTO material which is synthesized via a solid-state reaction. Powder X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy were conducted to investigate the structure and morphology. Afterwards, we surprisingly find that Ni and F co-modification can reduce the overall charge transfer resistance of LTO for part of Ti4+ converts into Ti3+ and Ni2+ ions supply the charge carriers. When test in battery, a superior discharge capacity of 236.1 mAh g−1 at 0.036 A g−1 is obtained, much higher than that of pristine LTO (196.9 mAh g−1). Furthermore, it still retains a discharge capacity of 174.6 mAh g−1 after 200 cycles at 0.18 A g−1 and exhibits an excellent rate performance.

Synthesis and Characterization of Ca-doped Li4Ti5O12 Using CaCO3 from Chicken Eggshell as a Dopant for Lithium-Ion Battery Anode Material

In order to improve the performance of Li4Ti5O12 (LTO) anode, this research was focused on Ca2+ion doping as a substitute to Li+ ion to form Li4-xCaxTi5O12with values of x=0, 0.05, 0.075, and 0.125 using solid-state reaction. The Ca2+ion source was CaCO3which synthesized from the chicken eggshell. The LTO was prepared by a solid-state method using TiO2 Degussa. The pristine LTO and Ca-doped LTO sample powder was characterized by XRD, SEM, and were also tested its electrochemical performance by EIS, CV and CD. The CaCO3 dopant characterization results showed CaCO3 in calcite polymorph as the main phase, with agglomerated fine particulate morphology and high purity. Characterization of LTO sample powder with XRD revealed that dopant Ca successfully enter the structure of LTO spinel, with maximum addition level x=0.05, which excessive addition led to CaTiO3 impurity forming. SEM result showed all Ca-doped LTO have almost similar morphology, which was agglomerated particulate. Ca-doped LTO samples have smaller particle size compared to pristine LTO. Electronic conductivity improvement was spotted at all of Ca-doped LTO sample, with Li3.75Ca0.125Ti5O12 (LCaTO-3) showed the lowest charge transfer resistance of 29.5 Ω. Li3.75Ca0.125Ti5O12(LCaTO-3) also had the highest initial discharge capacity of 168.2 mAh/g. Nevertheless, in high rate application, the best performance was showed by Li3.85Ca0.075Ti5O12(LCaTO-2) with the discharge capacity of 30.2 mAh/g at 12 C, which capacity retention percentage of 21.43% compared to its discharge capacity at 0.2 C.

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.

Plasma-Introduced Oxygen Defects Confined in Li4Ti5O12 Nanosheets for Boosting Lithium-Ion Diffusion.

Although Li4Ti5O12 (LTO) is considered as a promising anode material for high-power Li-ion batteries with high safety, the sluggish Li-ion diffusion coefficient restricts its widespread application. In this work, oxygen vacancy was successfully incorporated into LTO by an eco-friendly and cost-effective plasma process. The deficient LTO delivers much higher capacities of 173.4 mAh g-1 at 1C rate after 100 cycles and 140.5 mAh g-1 at 5C after 1000 cycles than those of pristine LTO. Meanwhile, even at a high rate of 20C, it displays an ultrahigh capacity of 133.1 mAh g-1 after 500 cycles with a Coulombic efficiency of 100%. Detailed analysis reveals that the lithium storage mechanisms in the oxygen-deficient LTO, especially at high rate, were dominated by the insertion behavior and dual-phase conversion due to the fast ion-diffusion ability, rather than the widely reported surface capacitance by other approaches. This work highlights that defect generation by plasma in nanomaterials is an effective way to promote ion mobility, especially at high rates, and thus can be extended to other electrode materials for advanced energy-storage applications.

Preparation and Characterization of Oxygen-Deficient Li4Ti5O12 Anode Material in Reducing Atmosphere for Lithium Ion Batteries

The poor electrical conductivity of Li4Ti5O12 has limited its practical application as high rates performance anode for lithium ion batteries. An oxygen deficient Li4Ti5O12 is investigated by a reducing atmosphere for lithium ion batteries in this work. Compared with pristine Li4Ti5O12 calcined at argon and air, the oxygen deficient Li4Ti5O12 exhibits significant improvement of electrochemical performance, it could deliver a specific capacity of 114.8 mAh g −1 even at a high charge/discharge rate of 10C and exhibit excellent cycling performance at low rates. However, more oxygen vacancies will increase the distortion of the lattice, causing serious deterioration in anode performance. Herein, an appropriate concentration of oxygen deficiency in oxygen-deficient Li4Ti5O12 is obtained by controlling the reducing atmosphere flow of ∼170 mL/min to possess optimal electrochemical performance.

Enhance the electrochemical performance of Li4Ti5O12 with Co doping via a facile mechanical activation strategy

Co-doped Li4Ti5O12 nanosheets are synthesized via a facile hydrothermal method assisted by mechanical activation technology. The as-prepared Co-doped Li4Ti5O12 is characterized by X-ray diffraction, scanning electron microscope and transmission electron microscopy. The morphology measurement shows that the Co-doped Li4Ti5O12 still maintain the three-dimensional nanosheet structures and good crystallinity after Co doping. As we expected, Co-doped Li4Ti5O12 exhibits higher initial discharge specific capacity, improved cycling performance, and impressive rate capability compared with pristine Li4Ti5O12 nanosheets. Even under 20 °C charge/discharge rates, the initial discharge capacity of Co-doped Li4Ti5O12 is up to 106 mAh g−1. The electrochemical impedance spectra measurement further displays that the charge-transfer resistance of Co-doped Li4Ti5O12 is much lower than that of pristine one after 20 cycles. The improved electrochemical performance of Co-doped Li4Ti5O12 is mainly because the Co doping can effectively enlarge the size of the channel by altering the lattice parameter, which can facilitate Li+ diffusion and electron transportation.