Rutile-TiO2 nanocoating for a high-rate Li4Ti5O12 anode of a lithium-ion battery

Well-defined Li(4)Ti(5)O(12) nanosheets terminated with rutile-TiO(2) at the edges were synthesized by a facile solution-based method and revealed directly at atomic resolution by an advanced spherical aberration imaging technique. The rutile-TiO(2) terminated Li(4)Ti(5)O(12) nanosheets show much improved rate capability and specific capacity compared with pure Li(4)Ti(5)O(12) nanosheets when used as anode materials for lithium ion batteries. The results here give clear evidence of the utility of rutile-TiO(2) as a carbon-free coating layer to improve the kinetics of Li(4)Ti(5)O(12) toward fast lithium insertion/extraction. The carbon-free nanocoating of rutile-TiO(2) is highly effective in improving the electrochemical properties of Li(4)Ti(5)O(12), promising advanced batteries with high volumetric energy density, high surface stability, and long cycle life compared with the commonly used carbon nanocoating in electrode materials.     

Li_4Ti_5O_(12)纳米片的合成及储锂性能研究

以无定形的水合二氧化钛为前驱物,水热法合成了200～400nm大小的Li4Ti5O12纳米片作为锂离子电池负极材料.XRD(X射线衍射)、SEM(扫描电子显微镜)和TEM(透射电镜)分析表征样品的物相结构、表观形貌;循环伏安、充放电循环和电化学交流阻抗技术分别测定该纳米Li4Ti5O12在有机电解液和室温离子液体S114TFSI电解液中的电化学性能.结果表明,该材料具有较高的放电容量和良好的循环性能,有望成为锂二次电池新型负极材料.     

多孔炭模板法制备Li4Ti5O12及其嵌锂行为

采用水合氧化钛溶胶为原料, 多孔炭为模板剂, 设计制备了一种新型准纳米晶锂钛复合氧化物, 并用SEM、XRD、恒流充放电及交流阻抗测试表征了材料的形貌、结构和电化学性能. 结果表明, 该氧化物晶粒尺寸约200 nm, 为典型的尖晶石Li4Ti5O12结构. 在0.5C(1C=0.2 mA·cm-2)电流条件下的首次嵌脱锂效率为99.8%, 嵌脱锂电位平坦, 可逆容量为117 mAh·g-1; 当电流从0.5C增至5C时, 其可逆嵌锂容量仍在100 mAh·g-1以上, 容量保持率大于86%, 倍率充放电性能优异. 交流阻抗测试结果表明, 模板剂多孔炭的应用使合成的尖晶石Li4Ti5O12具有更佳的导电性能, 且多孔特征明显.     

锂钛复合氧化物锂离子电池负极材料的研究

采用 3种化学方法合成锂钛复合氧化物 .应用X -射线衍射分析对其结构进行表征以及电化学性能测试 ,结果表明 :由Li2 CO3、TiO2 高温合成的锂钛复合氧化物为尖晶石结构的Li4Ti5 O12 .Li4Ti5 O12 电极在 1 .5V左右有一放电平台 ,充放电可逆性良好 ,即充电电压平台与此接近 ,且电极的比容量较大 ,循环性能良好 .以 0 .30mA·cm- 2 充放电时 ,首次放电容量可达 30 0mAh·g- 1,可逆比容量为 1 0 0mAh·g- 1,经多次充放电循环后 ,其结构仍保持稳定性 .试验电池测试表明 ,Li4Ti5 O12 可选作Li4Ti5 O12 /LiCoO2 锂离子电池的负极材料 .     

纳米微晶TiO2合成Li4Ti5O12及其嵌锂行为

用溶胶-凝胶法并经热处理制备不同形态和晶体尺寸的TiO2，分别与Li2CO3高温固相反应生成锂钛复合氧化物，经电化学测试发现,用300 ℃热处理所得纳米微晶TiO2制备的Li4Ti5O12具有良好的嵌锂性能，其可逆比容量大于95 mA•h•g－1，充放电效率近100％，循环性能良好，电压平台平稳,在嵌锂至容量≥85％或脱锂至容量≥90％时均有明显的电压变化，可用作锂离子电池负极材料.     

Changes in electronic structure upon lithium insertion into the A-site deficient perovskite type oxides (Li,La)TiO3

Investigation on variation of the electronic structure accompanying the electrochemical lithium insertion into the perovskite type oxide, (Li,La)TiO3, has been carried out by X-ray absorption spectroscopy (XAS). During the electrochemical lithium insertion, titanium ion reduced its oxidation state from Ti4+ to Ti3+, while La3+ does not contribute to the reduction reaction resulting from Ti K-edge and La L3-edge XAS, respectively. Furthermore, O K-edge XAS showed marked spectral changes with electrochemical lithium insertion, indicating the electronic structure around oxide ion affected by lithium insertion reaction. From the XAS measurement, we have concluded the variation observed in O K-edge XAS was related to the strong interaction with inserted Li ion. To confirm this, first-principles band calculations were performed for the perovskite structure before and after electrochemical lithium insertion. The calculated results showed that the electron originated from inserted Li transferred to neighboring oxide ion locally as well as to Ti ion. This may be due to local neutralization effect of Li to reduce the electrostatic interaction in the crystal.     

Epitaxial growth and electrochemical properties of Li4Ti5O12 thin-film lithium battery anodes

Epitaxial Li(4)Ti(5)O(12) thin-films were successfully synthesized on SrTiO(3) single-crystal substrates with (111), (110), and (100) lattice plane orientations using pulsed laser deposition (PLD). Thin-film X-ray diffraction (XRD) revealed that the Li(4)Ti(5)O(12) films had the same orientation as the SrTiO(3) substrates: Li(4)Ti(5)O(12) (111) on SrTiO(3) (111), Li(4)Ti(5)O(12) (110) on SrTiO(3) (110), and Li(4)Ti(5)O(12) (100) on SrTiO(3) (100). These epitaxial films contained island structures, and the morphology of the (111), (110), and (100) films, observed by field emission scanning electron microscopy (FE-SEM), exhibited angular, needle-like, and circular shapes, respectively. The electrochemical properties of 20 nm thick Li(4)Ti(5)O(12) (111) and (110) films were investigated by cyclic voltammetry. Reversible intercalation proceeded through both lattice planes due to the three-dimensional diffusion pathway of lithium in the spinel framework. Reduction peaks in the first cathodic scan appeared at different positions from those in subsequent scans, suggesting a surface reconstruction at the Li(4)Ti(5)O(12) surface due to interfacial reactions.     

Nitridation-driven conductive Li4Ti5O12 for lithium ion batteries

To modify oxide structure and introduce a thin conductive film on Li4Ti5O12, thermal nitridation was adopted for the first time. NH3 decomposes surface Li4Ti5O12 to conductive TiN at high temperature, and surprisingly, it also modifies the surface structure in a way to accommodate the single phase Li insertion and extraction. The electrochemically induced Li4+deltaTi5O12 with a TiN coating layer shows great electrochemical properties at high current densities.     

锂离子电池负极材料Li4Ti5O12的半固相法制备及碳包覆改性

由半固相法制得锂离子电池负极材料Li4Ti5O12,并研究了Li4Ti5O12的碳包覆改性.采用XRD、SEM、TEM以及HRTEM观察和分析产物的相结构与形貌.采用恒流充放电、循环伏安法和交流阻抗技术测试了材料的电化学性质.结果表明,Li4Ti5O12因颗粒团聚电化学性能严重下降,该电极在0.1C和0.5C首周期放电容量分别为121.7和87.6 mAh·g-1;碳包覆Li4Ti5O12/C材料呈球形分布,能抑制颗粒团聚,该电极倍率<0.5C时的放电比容量大于180 mAh·g-1,超过Li4Ti5O12的理论放电比容量(175 mAh·g-1);在1C、5C和10C倍率下,其容量仍保持在136、79.9和58.3 mAh·g-1,碳包覆改性材料具有优异的循环寿命和高倍率性能.     

Sb2O3掺杂Li4Ti5O12的电化学性能

采用Sb2O3掺杂改性Li4Ti5O12.用恒流充放电、循环伏安和交流阻抗技术对样品的电化学性能进行了测试.结果显示,当Ti:Sb＝4：1时,首次放电容量高达595.84mAhog-1,首次的库仑效率为45.7％,存在不可逆容量损失.提出了可能的反应机理,并用该机理解释了影响容量衰减的因素.经过20次充放电循环后,容量保持在249.57 mAhog-1.电化学阻抗谱表明,Sb的掺杂使得电化学反应阻抗减小了.     

三维有序大孔锂离子筛的制备及其交换性能研究

由110 nm聚苯乙烯(PS)微球组装晶体胶体模板,并用此模板合成三维有序大孔(3-dimensionally ordered macroporous,3DOM)锂离子筛前驱体Li4Ti5O12,用1.0 mol.L-1的盐酸改型制得锂离子筛H4Ti5O12(LiTi-H)。用XRD、SEM、饱和交换容量、pH滴定曲线等表征了材料的形貌、结构和离子交换性能。同时测定了25℃时LiTi-H在0.05 mol.L-1Li+体系吸附锂的动力学数据,并采用吸附动力学Bangham方程和Elovich方程关联离子筛LiTi-H对Li+的离子交换动力学数据。结果表明:PS胶体晶体模板和3DOMLi4Ti5O12锂离子筛前驱体均排列规则有序,大孔直径约90 nm,Li4Ti5O12为尖晶石结构;3DOM Li4Ti5O12酸稳定性好,锂离子筛LiTi-H对Li+具有较高的选择性,对Li+的饱和交换容量达56.70 mg(Li+).g-1;动力学模型用Elovich模型关联较好,离子筛对Li+的离子交换动力学方程是Q=-26.510 4+11.977 4lnt(25℃)。     

Temperature Effect on the Behavior of a Lithium Titanate Electrode

Russian Journal of Electrochemistry - The effect of temperature (over the–15 to +60°С range) on the insertion of lithium into Li4Ti5O12 is systematically studied. At a current of...     

P(VdF-HFP)-基离子液体复合聚合物电解质的阴极稳定性及热稳定性

以聚偏氟乙烯-六氟丙烯P(VdF-HFP)聚合物为基体, 制备了含离子液体1-甲基-3-乙基咪唑六氟磷酸盐(EMIPF6)、用于锂离子电池的离子液体复合聚合物电解质[P(VdF-HFP)/LiPF₆/EMIPF₆/EC(碳酸乙烯酯)-PC(碳酸丙烯酯)]. 采用热重分析法以及燃烧实验测试了复合聚合物电解质的热稳定性. 离子电导率测试表明, 离子液体的存在显著改善了复合聚合物电解质的离子传输; 循环伏安测试表明, 添加剂EC和PC的加入提高了复合电解质的阴极稳定性, 制得的离子液体复合聚合物电解质在0.3-4.3 V 电压范围内稳定存在. Li₄Ti₅O₁₂ 和LiCoO₂为电极材料、P(VdF-HFP)/LiPF₆/EMIPF₆/EC-PC 为电解质的半电池表现出优良的循环性能, 0.1C充放电倍率下, Li/LiCoO₂和Li/Li₄Ti₅O₁₂半电池的可逆容量分别为130和144 mAh·g^-1. 但EC、PC在一定程度上降低了离子液体复合聚合物电解质的热稳定性.     

Combining the pair distribution function and computational methods to understand lithium insertion in Brookite (TiO2)

X-ray pair distribution function (PDF) methods and first-principles calculations have been combined to probe the structure of electrochemically lithiated TiO(2) Brookite. Traditional powder diffraction studies suggest that Brookite amorphizes upon lithium insertion, with the Bragg reflections disappearing. However, PDF analysis indicates that the TiO(2) framework connectivity is maintained throughout lithium intercalation, with expansions along the a and b axes. The Li(+) ions within the framework are poorly observed in the X-ray PDF, which is dominated by contributions from the more strongly scattering Ti and O atoms. First-principles calculations were used to identify energetically favorable Li(+) sites within the Brookite lattice and to develop a complete structural model of the lithiated material. This model replicates the local structure and decreased intermediate range order observed in the PDF data. The analysis suggests that local structural distortions of the TiO(2) lattice accommodate lithium in five-coordinate sites. This structural model is consistent with the observed electrochemical behavior.     

高倍率性能正极材料LiFe_(0.9)Mg_(0.1)PO_4的结构

应用高温固相反应合成锂离子电池正极材料LiFePO4和LiFe0.9Mg0.1PO4.不同浓度的K2S2O8水溶液氧化LiFe0.9Mg0.1PO4制备部分脱锂两相混合物Li0.4Fe0.9Mg0.1PO4及完全脱锂单相化合物Li0.1Fe0.9Mg0.1PO4.X射线衍射物相分析(XRD),选区电子衍射(SAED)和高分辨原子图像(HRTEM)测试表明,脱锂相Li0.1Fe0.9Mg0.1PO4是单相化合物,没有发生相分离.点阵参数计算表明,LiFe0.9Mg0.1PO4体系嵌锂相和脱锂相的晶格错配度与LiFePO4体系相比有所降低,这正是锂离子电池正极材料LiFe0.9Mg0.1PO4具有高倍率循环充放电比容量的结构基础.     

Full structural and electrochemical characterization of Li2Ti6O13 as anode for Li-ion batteries

A detailed structural and electrochemical study of the ion exchanged Li(2)Ti(6)O(13) titanate as a new anode for Li-ion batteries is presented. Subtle structural differences between the parent Na(2)Ti(6)O(13), where Na is in an eightfold coordinated site, and the Li-derivative, where Li is fourfold coordinated, determine important differences in the electrochemical behaviour. While the Li insertion in Na(2)Ti(6)O(13) proceeds reversibly the reaction of lithium with Li(2)Ti(6)O(13) is accompanied by an irreversible phase transformation after the first discharge. Interestingly, this new phase undergoes reversible Li insertion reaction developing a capacity of 170 mAh g(-1) at an average voltage of 1.7 V vs. Li(+)/Li. Compared with other titanates this result is promising to develop a new anode material for lithium ion rechargeable batteries. Neutron powder diffraction revealed that Na in Na(2)Ti(6)O(13) and Li in Li(2)Ti(6)O(13) obtained by Na/Li ion exchange at 325 °C occupy different tunnel sites within the basically same (Ti(6)O(13))(2-) framework. On the other hand, electrochemical performance of Li(2)Ti(6)O(13) itself and the phase released after the first full discharge is strongly affected by the synthesis temperature. For example, heating Li(2)Ti(6)O(13) at 350 °C produces a drastic decrease of the reversible capacity of the phase obtained after full discharge, from 170 mAh g(-1) to ca. 90 mAh g(-1). This latter value has been reported for Li(2)Ti(6)O(13) prepared by ion exchange at higher temperature.     

An unsymmetrical lithium-ion pathway between charge and discharge processes in a two-phase stage of Li4Ti5O12

In this work, we investigated lithium-ion diffusion in spinel Li(4)Ti(5)O(12) nano-particles with carbon coating by electrochemical impedance spectroscopy (EIS), and proposed a hybrid model of the unsymmetrical lithium-ion pathway between charge and discharge processes. In this hybrid model, the charge process still follows the core-shell model, but in the discharge process, the phase transition evolves by growth of a few nuclei on the surface. And this hybrid model is possibly attributed to the nonuniform electron conductivity inside the Li(4)Ti(5)O(12) particles. Additionally, the relaxation process and the particle morphology are also carefully discussed in the experiment to show that this hybrid model is quite practical. Thereby, this investigation presents an unsymmetrical lithium-ion pathway in Li(4)Ti(5)O(12) particles, which could be extended to other active materials in lithium ion batteries.     

无机离子交换剂Mg1.5Mn0.5Ti0.75O4对Li 的交换选择性实验

利用共沉淀,固相反应热结晶法,合成具有尖晶石型的复合金属氧化物Mg1.5Mn0.5Ti0.75O4。具有尖晶石型结构的物质,可以插入大量的替代离子并且改变自身锂和氧的化学计量数,与此同时,还保持了结构的稳定。这种特性能够使得它们被用于离子交换研究,用来满足提取锂的需求。通过检测该复合氧化物的饱和交换能力值,分配系数值等,从而确定出该物质具体特性。实验表明,经过酸化的Mg1.5Mn0.5Ti0.75O4,其Mg2 的抽出比率能够达到72%,Mn4 和Ti4 的溶解比率低于8.2%。实验分析得出,Li 能够从无机离子交换剂Mg1.5Mn0.5Ti0.75O4中抽出以及插入,主要是归因于离子交换机理。被酸化的样品对Li 有一个10.6mmol?g-1的离子交换能力,并且对Li 还具有记忆性的离子筛性能。     

Low temperature nanostructured lithium titanates: controlling the phase composition, crystal structure and surface area

Low temperature lithium titanate compounds (i.e., Li₄Ti₅O₁₂ and Li₂TiO₃) with nanocrystalline and mesoporous structure were prepared by a straightforward aqueous particulate sol–gel route. The effect of Li:Ti molar ratio was studied on crystallisation behaviour of lithium titanates. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders were crystallised at the low temperature of 500 °C and the short annealing time of 1 h. Moreover, it was found that Li:Ti molar ratio and annealing temperature influence the preferable orientation growth of the lithium titanate compounds. Transmission electron microscope (TEM) images showed that the average crystallite size of the powders annealed at 400 °C was in the range 2–4 nm and a gradual increase occurred up to 10 nm by heat treatment at 800 °C. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had mesoporous and nanocrystalline structure with the average grain size of 21–28 nm at 600 °C and 49–62 nm at 800 °C depending upon the Li:Ti molar ratio. Moreover, atomic force microscope (AFM) images confirmed that the lithium titanate films had columnar like morphology at 600 °C, whereas they showed hill-valley like morphology at 800 °C. Based on Brunauer–Emmett–Taylor (BET) analysis, the synthesized powders showed mesoporous structure containing pores with needle and plate shapes. The surface area of the powders was enhanced by increasing Li:Ti molar ratio and reached as high as 77 m²/g for the ratio of Li:Ti = 75:25 at 500 °C. This is one of the smallest crystallite size and the highest surface areas reported in the literature, and the materials could be used in many applications such as rechargeable lithium batteries and tritium breeding materials.     

Electronically driven structural distortions in lithium intercalates of the n = 2 Ruddlesden-Popper-type host Y2Ti2O5S2: synthesis, structure, and properties of LixY2Ti2O5S2 (0 < x < 2)

Lithium intercalation into the oxide slabs of the cation-deficient n = 2 Ruddlesden-Popper oxysulfide Y(2)Ti(2)O(5)S(2) to produce Li(x)Y(2)Ti(2)O(5)S(2) (0 < x < 2) is described. Neutron powder diffraction measurements reveal that at low levels of lithium intercalation into Y(2)Ti(2)O(5)S(2), the tetragonal symmetry of the host is retained: Li(0.30(5))Y(2)Ti(2)O(5)S(2), I4/mmm, a = 3.80002(2) A, c = 22.6396(2) A, Z = 2. The lithium ion occupies a site coordinated by four oxide ions in an approximately square planar geometry in the perovskite-like oxide slabs of the structure. At higher levels of lithium intercalation, the symmetry of the cell is lowered to orthorhombic: Li(0.99(5))Y(2)Ti(2)O(5)S(2), Immm, a = 3.82697(3) A, b = 3.91378(3) A, c = 22.2718(2) A, Z = 2, with ordering of Li(+) ions over two inequivalent sites. At still higher levels of lithium intercalation, tetragonal symmetry is regained: Li(1.52(5))Y(2)Ti(2)O(5)S(2), I4/mmm, a = 3.91443(4) A, c = 22.0669(3) A, Z = 2. A phase gap exists close to the transition from the tetragonal to orthorhombic structures (0.6 < x < 0.8). The changes in symmetry of the system with electron count may be considered analogous to a cooperative electronically driven Jahn-Teller type distortion. Magnetic susceptibility and resistivity measurements are consistent with metallic properties for x > 1, and the two-phase region is identified as coincident with an insulator to metal transition.