Study on the effect of Li doping in spinel Li4+xTi5−xO12 (0 ⩽ x ⩽ 0.2) materials for lithium-ion batteries

The effect of Li doping in spinel Li_4+xTi_5−xO₁₂ (0 ⩽ x ⩽ 0.2) materials on the structural and electrochemical properties were investigated. The ratio of the capacity in the voltage plateau (1.5 V) to the overall discharge capacity for Li_4.1Ti_4.9O₁₂ (x = 0.1) and Li_4.2Ti_4.8O₁₂ (x = 0.2) were higher than that of Li₄Ti₅O₁₂ especially at high current rates due to their enhanced lithium-ion and electronic conductivity by the substitution of Ti atoms by Li atoms. With the increasing of Li doping amount, lithium-ion and electronic conductivity of Li_4+xTi_5−xO₁₂ increased, however its cycling stability was depressed when the Li doping was of x = 0.2. The Li doping of x = 0.1, the appropriate Li doping amount, showed improved rate capability and better high rate performance comparing to undoped Li_4+xTi_5−xO₁₂ (x = 0).     

Li4Ti5O12/reduced graphite oxide nano-hybrid material for high rate lithium-ion batteries

A spinel Li₄Ti₅O₁₂ nanoplatelet/reduced graphite oxide nano-hybrid was successfully synthesized by a two-step microwave-assisted solvothermal reaction and heat treatment. The Li₄Ti₅O₁₂ in the hybrid could deliver a discharge capacity of 154 mAhg^? 1 of Li₄Ti₅O₁₂ at 1 C-rate, 128 mAhg^-1 of Li₄Ti₅O₁₂ at 50 C-rate and 101 mAhg^-1 of Li₄Ti₅O₁₂ at 100 C-rate. It demonstrated promising potential as an anode material in a Li-ion battery with excellent rate capability and good cycling.     

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

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

A strategy for scalable synthesis of Li4Ti5O12/reduced graphene oxide toward high rate lithium-ion batteries

Li₄Ti₅O₁₂/reduced graphene oxide (RGO) composites were prepared via a simple strategy. The as-prepared composites present Li₄Ti₅O₁₂ nanoparticles uniformly immobilized on the RGO sheets. The Li₄Ti₅O₁₂/RGO composites possess excellent electrochemical properties with good cycle stability and high specific capacities of 154 mAh g^− 1 (at 10C) and 149 mAh g^− 1 (at 20C), much higher than the results found in other literatures. The superior electrochemical performance of the Li₄Ti₅O₁₂/RGO composites is attributed to its unique hybrid structure of conductive graphene network with the uniformly dispersed Li₄Ti₅O₁₂ nanoparticles.     

Sulfone-based electrolytes for high-voltage Li-ion batteries

Sulfone-based electrolytes have been investigated as electrolytes for lithium-ion cells using high-voltage positive electrodes, such as LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ spinels, and Li₄Ti₅O₁₂ spinel as negative electrode. In the presence of imide salt (LiTFSI) and ethyl methyl sulfone or tetramethyl sulfone (TMS) electrolytes, the Li₄Ti₅O₁₂/LiMn₂O₄ cell exhibited a specific capacity of 80 mAh g^?1 with an excellent capacity retention after 100 cycles. In a cell with high-voltage LiNi_0.5Mn_1.5O₄ positive electrode and 1 M LiPF₆ in TMS as electrolyte, the capacity reached 110 mAh g^?1 at the C/12 rate. When TMS was blended with ethyl methyl carbonate, the Li₄Ti₅O₁₂/LiNi_0.5Mn_1.5O₄ cell delivered an initial capacity of 80 mAh g^?1 and cycled fairly well for 1000 cycles under 2C rate. The exceptional electrochemical stability of the sulfone electrolytes and their compatibility with the Li₄Ti₅O₁₂ safer and stable anode were the main reason behind the outstanding electrochemical performance observed with high-potential spinel cathode materials. These electrolytes could be promising alternative electrolytes for high-energy density battery applications such as plug-in hybrid and electric vehicles that require a long cycle life.     

Li2CuTi3O8–Li4Ti5O12 double spinel anode material with improved rate performance for Li-ion batteries

Ti-based anode materials with the nominal compositions Li₄Ti₅Cu_xO_12 + x (x = 0, 0.075, 0.15, 0.3, 0.6, 1.20 and 1.67) were synthesized at 800 °C by a solid-state reaction process. X-ray diffraction analysis indicated that the sintered samples were composed of intergrown spinel-type Li₄Ti₅O₁₂ and Li₂CuTi₃O₈, and a small amount of Li₂O. Scanning electron microscopy, electrical resistance measurement and galvanostatic cell cycling were also employed to characterize the structure and properties of the double spinel samples. It is proposed that the first lithiation of the component Li₂CuTi₃O₈ leads to the in situ production of Cu that can significantly improve the rate performance of Li₄Ti₅Cu_xO_12 + x. The optimal nominal composition is Li₄Ti₅Cu_0.15O_12.15.     

Ab initio studies of structural and electronic properties of Li4Ti5O12 spinel

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

Sol–gel fabrication of lithium-ion microarray battery

Microarray electrodes of LiMn₂O₄ and Li_4/3Ti_5/3O₄ were prepared on a glass substrate using a sol–gel method. The prepared LiMn₂O₄ and Li_4/3Ti_5/3O₄ microarray electrodes were characterized with scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. Using a polymer-gel electrolyte, lithium ion microbattery of Li_4/3Ti_5/3O₄/polymer-gel/LiMn₂O₄ (cell area: 6.6 × 10⁻² cm²) was successfully constructed. The microbattery operated reversibly at 2.5 V, and the discharge capacity was 300 nA h, which corresponded to an energy density of 11 μW h cm⁻².     

Li(4−x)/3Ti(5−2x)/3CrxO4 (0 ≤ x ≤ 0.9) spinels: New negatives for lithium batteries

Members of the spinel solid solution between Li_4/3Ti_5/3O₄ and LiCrTiO₄, i.e., Li_(4−x)/3Ti_(5−2x)/3Cr_xO₄ (0 ≤ x ≤ 0.9), have been investigated as possible negative electrodes for future lithium-ion batteries. Electrochemical behaviour have been studied over the potential range 1–3.5 V vs Li⁺/Li. Results are promising with anodic capacities between 129 and 163 mA h/g with a flat operating voltage at about 1.5 V, which is attributed to the pair Ti⁴⁺/Ti³⁺. The inclusion of Cr³⁺ in the spinel structure enhances the specific capacity. In-situ X-ray diffraction experiments confirm that the reaction proceeds in a topotactic manner.     

LiMn2O4 hollow nanosphere electrode material with excellent cycling reversibility and rate capability

Lithium-rich Li_1.05Mn₂O₄ hollow nanospheres have been successfully prepared by air-calcining lithiated MnO₂ precursor at a low temperature of 550 °C, which was synthesized by chemical lithiation of hollow MnO₂ nanospheres with LiI at 70 °C for 12 h. The lithium-rich Li_1.05Mn₂O₄ hollow nanospheres exhibit an excellent cycling stability and rate capability as a cathode material for rechargeable lithium batteries: it maintains 90% of its initial capacity after 500 cycles, and keeps 70% of the reversible capacity at 0.1 C rat, even at 15 C rate.     

Self-assembled Li4Ti5O12/TiO2/Li3PO4 for integrated Li–ion microbatteries

This work aims to maximize the number of active sites for energy storage per geometric area, by approaching the investigation to 3D design for microelectrode arrays. Self-organized Li₄Ti₅O₁₂/TiO₂/Li₃PO₄ composite nanoforest layer (LTL) is obtained from a layer of self organized TiO₂/Li₃PO₄ nanotubes. The electrochemical response of this thin film electrode prepared at 700 °C exhibited lithium insertion and de-insertion at 1.55 and 1.57 V respectively, which is the typical potential found for lithium titanates. The effects of lithium phosphate on lithium titanate are explored for the first time. By cycling between 2.7 and 0.75 V the LTL/LiFePO₄ full cell delivered 145 mA h g^− 1 at an average potential of 1.85 V leading to an energy density of 260 W h kg^− 1 at C/2. Raman spectroscopy revealed that the γ-Li₃PO₄/lithium titanate structure is preserved after prolonged cycling. This means that Li₃PO₄ plays an important role for enhancing the electronic conductivity and lithium ion diffusion.     

Reversible lithium storage in Na2Li2Ti6O14 as anode for lithium ion batteries

The sodium lithium titanate with composition Na₂Li₂Ti₆O₁₄ has been synthesized by a sol–gel method. Thermogravimetric analysis and differential thermal analysis (TG–DTA) of the thermal decomposition process of the precursor and X-ray diffraction (XRD) data indicate the crystallization of sodium lithium titanate has occurred at about 600 °C. Electrochemical lithium insertion into Na₂Li₂Ti₆O₁₄ for lithium ion battery has been investigated for the first time. These results indicate the discharge and charge potential plateaus are about 1.3 V. The initial discharge capacity is much higher than the charge capacity and irreversible capacity exists in the voltage window 1–3 V. Subsequently, the discharge capacity decreases slowly, but the charge capacity increases slightly in the following cycles. After a few cycles, the specific capacity remains almost constant values and the sample exhibits the excellent retention of capacity on cycling.     

A novel all-solid-state thin-film-type lithium-ion battery with in situ prepared positive and negative electrode materials

A novel all-solid-state thin-film-type rechargeable lithium-ion battery employing in situ prepared both positive and negative electrode materials is proposed. A lithium-ion conducting solid electrolyte sheet of Li₂O–Al₂O₃–TiO₂–P₂O₅-based glass–ceramic manufactured by OHARA Inc. (OHARA sheet) was used as the solid electrolyte, which was sandwiched by Cu and Mn metal films. The Cu/OHARA sheet/Mn layer became an all-solid-state lithium-ion battery after applying d.c. 16 V to the layer, and the resultant battery operated at 0.3–0.8 V with reversible capacity of 0.45 μAh cm^?2. High voltage battery was successfully prepared by applying the d.c. high voltage to a five-series of Cu/OHARA sheet/Mn layer, resulting in all-solid-state battery operating at 1.5–4.0 V. The proposed fabrication process will become a new technology to develop advanced all-solid-state rechargeable lithium-ion batteries.     

Li2ZnTi3O8 nanorods: A new anode material for lithium-ion battery

Spinel Li₂ZnTi₃O₈ nanorods were first synthesized using titanate nanowires as a precursor. The synthesized nanorods are highly crystalline and used as an anode material in a rechargeable Li-ion battery. A large capacity of 220 mA h g^? 1 was kept after 30 cycles at a current density of 0.1 A g^? 1, which is close to the theoretic capacity. The electrochemical measurements indicate that the anode material made of spinel Li₂ZnTi₃O₈ nanorods displayed a highly reversible capacity and excellent cycling stability.     

Nb2O5 nanobelts: A lithium intercalation host with large capacity and high rate capability

In this study, Nb₂O₅ nanobelts, with a ca. ∼15 nm in thickness, ca. ∼60 nm in width and several tens of mircrometers in length, have first been used as the electrode material for lithium intercalation over the potential window of 3.0–1.2 V (vs. Li⁺/Li). It delivers an initial intercalation capacity of 250 mA hg⁻¹ at 0.1 Ag⁻¹ current density, corresponding to x = 2.5 for L_xNb₂O₅, and can still keep relative stable and reaches as large as 180 mA hg⁻¹ after 50 cycles. Surprisingly, the electrodes composed of Nb₂O₅ nanobelts can work smoothly even at high current density of 10 Ag⁻¹, and shows higher specific capacity and excellent cycling stable, as well as sloped feature in voltage profile. Cycling test indicates Nb₂O₅ nanobelts electrode shows a high reversible charge/discharge capacity, high rate capability with excellent cycling stability.     

High rate performance of lithium manganese nitride and oxynitride as negative electrodes in lithium batteries

The performance of Li_7.9MnN_3.2O_1.6 and Li₇MnN₄ as electrode materials in lithium batteries was analyzed. At 1C rate, capacities of 180 and 230 mAh/g, respectively, were obtained after 50 cycles. If the first charge is done at 0.1C, outstanding capacities of 120–135 mAh/g are observed after 100 cycles at 5C. More lithium can be removed during the charge at 0.1C, leading to a large amount of lithium vacancies that enhance mobility and rate capability. It is proposed that incomplete filling of the vacancies occurs upon cycling, so that the mobility remains high. This performance compares well to that of Li₄Ti₅O₁₂.     

Effect of Nb-doping on electrochemical stability of Li4Ti5O12 discharged to 0?V

Li₄Ti_4.95Nb_0.05O₁₂ is synthesized by a citric acid-assistant sol–gel method. X-ray diffraction (XRD) reveals that highly crystalline Li₄Ti_4.95Nb_0.05O₁₂ without any impurity is obtained. The electrochemical performances of the Li₄Ti_4.95Nb_0.05O₁₂ and the Li₄Ti₅O₁₂ in the range from 0 to 2.5 V are investigated. The Li₄Ti_4.95Nb_0.05O₁₂ presents a higher specific capacity and better cycling stability than the Li₄Ti₅O₁₂ due to the improved conductivity. The Li₄Ti_4.95Nb_0.05O₁₂ exhibits a capacity as high as 231.2 mAh g⁻¹ after 100 cycles, which is much higher than the Li₄Ti₅O₁₂ (111.1 mAh g⁻¹). The effect of Nb-doping on electrochemical performance of Li₄Ti₅O₁₂ discharged to 0 V has also been discussed.     

High capacity Li[Li0.2Mn0.54Ni0.13Co0.13]O2–V2O5 composite cathodes with low irreversible capacity loss for lithium ion batteries

With an aim to suppress the huge irreversible capacity loss encountered in high capacity layered oxide solid solutions between Li₂MnO₃ and LiMO₂ (M = Mn, Ni, and Co), layered Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂–V₂O₅ composite cathodes with various V₂O₅ contents have been investigated. The irreversible capacity loss decreases from 68 mAh/g at 100% Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ to 0 mAh/g around 89 wt.% Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂–11 wt.% V₂O₅ as the lithium-free V₂O₅ serves as an insertion host to accommodate the lithium ions that could not be inserted back into the layered lattice after the first charge. The Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂–V₂O₅ composite cathodes with about 10–12 wt.% V₂O₅ exhibit an attractive discharge capacity of close to 300 mAh/g with little irreversible capacity loss and good cyclability.     

High-performance thin-film Li4Ti5O12 electrodes fabricated by using ink-jet printing technique and their electrochemical properties

Li₄Ti₅O₁₂ thin-film anode with high discharge capacity and excellent cycle stability for rechargeable lithium ion batteries was prepared successfully by using ink-jet printing technique. The prepared Li₄Ti₅O₁₂ thin film were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammograms, and galvanostatic charge–discharge measurements. It was found that the average thickness of 10-layer Li₄Ti₅O₁₂ film was about 1.7~1.8 μm and the active material Li₄Ti₅O₁₂ in the thin film was nano-sized about 50–300 nm. It was also found that the prepared Li₄Ti₅O₁₂ thin film exhibited a high discharge capacity of about 174 mAh/g and the discharge capacity in the 300th cycle retained 88% of the largest discharge capacity at a current density of 10.4 μA/cm² in the potential range of 1.0–2.0 V.     

A disordered rock-salt Li-excess cathode material with high capacity and substantial oxygen redox activity: Li1.25Nb0.25Mn0.5O2

A disordered rocksalt Li-excess cathode material, Li_1.25Nb_0.25Mn_0.5O₂, was synthesized and investigated. It shows a large initial discharge capacity of 287 mAh g^− 1 in the first cycle, which is much higher than the theoretical capacity of 146 mAh g^− 1 based on the Mn³⁺/Mn⁴⁺ redox reaction. In situ X-ray diffraction (XRD) demonstrates that the compound remains cation-disordered during the first cycle. Electron energy loss spectroscopy (EELS) suggests that Mn and O are likely to both be redox active, resulting in the large reversible capacity. Our results show that Li_1.25Nb_0.25Mn_0.5O₂ is a promising cathode material for high capacity Li-ion batteries and that reversible oxygen redox in the bulk may be a viable way forward to increase the energy density of lithium-ion batteries.