Lithium barium titanate: A stable lithium storage material for lithium-ion batteries

Accepted Manuscript Lithium barium titanate: A stable lithium storage material for lithium-ion batteries Xiaoting Lin, Peng Li, Lianyi Shao, Miao Shui, Dongjie Wang, Nengbing Long, Yuanlong Ren, Jie Shu PII:

S0378-7753(14)02171-5

DOI:

10.1016/j.jpowsour.2014.12.132

Reference:

POWER 20411

To appear in:

Journal of Power Sources

Received Date: 11 November 2014 Revised Date:

22 December 2014

Accepted Date: 26 December 2014

Please cite this article as: X. Lin, P. Li, L. Shao, M. Shui, D. Wang, N. Long, Y. Ren, J. Shu, Lithium barium titanate: A stable lithium storage material for lithium-ion batteries, Journal of Power Sources (2015), doi: 10.1016/j.jpowsour.2014.12.132. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Graphical Abstract

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Lithium barium titanate: A stable lithium storage material for lithium-ion batteries

Xiaoting Lin, Peng Li, Lianyi Shao, Miao Shui, Dongjie Wang, Nengbing Long,

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Yuanlong Ren, Jie Shu*

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Lithium barium titanate: A stable lithium storage material for

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lithium-ion batteries

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Xiaoting Lin, Peng Li, Lianyi Shao, Miao Shui, Dongjie Wang, Nengbing Long,

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Yuanlong Ren, Jie Shu*

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Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo

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315211, Zhejiang Province, People’s Republic of China

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* Corresponding author: Jie Shu

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Tel.: +86-574-87600787

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Fax: +86-574-87609987

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E-mail: [email protected]

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Abstract A series of Li2BaTi6O14 samples are synthesized by a traditional solid-state

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method by calcining at different temperatures from 800 to 1000 oC. Structural analysis

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and electrochemical evaluation suggest that the optimum calcining temperature for

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Li2BaTi6O14 is 950 oC. The Li2BaTi6O14 calcined at 950 oC exhibits a high purity

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phase with an excellent reversible capacity of 145.7 mAh g-1 for the first cycle at a

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current density of 50 mA g-1. After 50 cycles, the reversible capacity can be

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maintained at 137.7 mAh g-1, with the capacity retention of 94.51 %. Moreover, this

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sample also shows outstanding rate property with a high reversible capacity of 118

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mAh g-1 at 300 mA g-1. The excellent electrochemical performance is attributed to the

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stable lithium storage host structure, decreased electrochemical resistance and

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improved lithium-ion diffusion coefficient. In-situ and ex-situ structure analysis

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shows that the electrochemical reaction of Li2BaTi6O14 with Li is a highly reversible

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lithiation-delithiation process. Therefore, Li2BaTi6O14 may be a promising alternative

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anode material for lithium-ion batteries.

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Keywords: Lithium barium titanate; Stable host structure; Electrochemical behavior;

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Anode material; Lithium-ion batteries.

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1. Introduction With increasing concerns on energy shortage and environmental issues from

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fossil fuels, the demand for green and sustainable energy sources is urgent [1].

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Lithium-ion batteries with high energy density, rechargeability, and safety are

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considered to be one of the most promising green energy resources to be widely used

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in electric vehicles and hybrid electric vehicles, and the demand for high performance

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in lithium-ion batteries has stimulated researchers to explore different types of anode

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materials [2, 3].

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Since the crystal structure and electrical properties of LiFeTiO4 reported by M.A.

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Arillo in 1998 [4], there is an increasing interest in the study of spinel structured

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materials such as LiVTiO4 [5], LiCrTiO4 [6] due to their rich electrical properties. At

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the same time, the electrochemical behaviors of Li2MTi3O8 (M=Zn [7-10], Co [11],

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Mg [12], Mn [13, 14], Co0.5Cu0.5 [15] etc.) with lithium have also been investigated as

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anode materials for lithium-ion batteries. Li2MTi3O8 demonstrates many advantages

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compared to the conventional used graphite, which has high operating potential,

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specific storage capacity and stable structure [15]. However, the poor cycling

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performance is still a challenge [16, 17]. Thus, the synthesis of a new anode material

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with high capacity and high cycling stability is still a challenge. More recently, much

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effort has been devoted to the exploration of Li2MTi6O14 (M=Sr [18-22], Ba [21, 22],

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Pb [22], 2Na [23-25]), which possess lower potential and higher theoretical capacity

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compared to Li4Ti5O12 [26, 27]. The synthesis method, structural analysis and

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electrochemical characterization of Li2SrTi6O14 and Li2Na2Ti6O14 have been

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extensively studied [21, 22]. However, the electrochemical properties of Li2BaTi6O14

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have not been systematically investigated in detail.

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ACCEPTED MANUSCRIPT In the present work, we have successfully studied the temperature effect on the

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phases, morphologies and electrochemical properties of Li2BaTi6O14 via traditional

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solid-state method at different calcining temperatures. The as-synthesized

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Li2BaTi6O14 was tested as anode material for lithium-ion batteries and presented high

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reversible capacity and excellent cycling performance. In order to better understand

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the lithium storage mechanism in Li2BaTi6O14, we also utilized in-situ and ex-situ

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techniques to make a careful study of the electrochemical reversibility of Li2BaTi6O14

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during the first charge-discharge cycle.

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2. Experimental

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In this experiment, Li2BaTi6O14 was synthesized by a traditional solid-state

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method and all chemicals used in the experiments were analytical reagent. Firstly,

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stoichiometric amounts of BaCO3 (Aladdin, 99.5 %), LiCO3 (Aladdin, 99.5 %), and

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TiO2 (Aladdin, 5-10 nm, 99.5 %) were mixed at a molar ratio of Ba/Li/Ti =1:2.02:6

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(0.02 unit of Li used to compensate for Li volatilization at high temperature) and

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pretreated by planetary ball milling in ethanol for 12 hours. The obtained precursor

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slurry was dried at 80 oC for 24 hours, then progressively heated up to 600 oC to

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decompose the carbonate salts and calcined at the temperatures varying from 800 to

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1000 oC for 10 hours in air atmosphere.

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The phase identification and crystallinity analysis of the final samples were

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characterized by Bruker D8 Focus X-ray diffraction (XRD, diffractometer with Cu-

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Kα radiation, λ=1.5406 Å) with scattering angles of 10o-50o in a step of 0.02o. The

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surface morphology and particle size of samples were observed by Hitachi S4800

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scanning electron microscopy (SEM). The fine crystal structure of Li2BaTi6O14 was

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analyzed by JEOL JEM-2010 high-resolution transmission electron microscopy

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(HRTEM) The electrochemical performances of the products were evaluated by coin-type

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cells. Working electrodes were fabricated by mixing of 80 wt.% active materials, 10

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wt.% carbon black as conductive additive and 10 wt.% polyvinylidene difluoride as

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binder, and N-methyl-2-pyrrolidone as solvent. Next, the mixed viscous slurry was

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coated onto copper foil and dried at 100 oC for 12 hours in a vacuum oven, and then

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cut into discs with a diameter of 15 mm. In the coin-type cells, the as-prepared film

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was used as the working electrode and lithium foil was provided as the counter

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electrode separated by a Whatman glass fiber. The electrolyte was 1 mol L-1 LiPF6

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dissolved in a mixture of ethylene carbonate and dimethyl carbonate (1:1, v/v).

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For electrochemical measurements, charge-discharge behavior and rate

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performance of coin-type cells were measured by multi-channel Land CT2001A

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battery test system at room temperature. In addition, cyclic voltammogram (CV) was

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performed at a scan rate of 0.1 mV s-1 from 0.5 to 3.0 V on a CHI 1000B

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electrochemical workstation at room temperature. Electrochemical impedance

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spectroscopy (EIS) patterns were obtained on a CHI 660D electrochemical

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workstation in the frequency range from 0.01 to 100000 Hz at room temperature.

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The in-situ structural evolutions of Li2BaTi6O14 obtained at 950 oC during Li+

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extraction/insertion were observed by in-situ XRD using the same Bruker D8 Focus

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X-ray diffraction instrument as described above. Prior to the in-situ X-ray diffraction

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tests, Li2BaTi6O14 powders was mixed with carbon black and subsequently ground in

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agate mortar and then ready for the following in-situ XRD tests. The structure and

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equipment of the in-situ XRD battery were described in our previous paper [28, 29].

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All the coin-type cells and in-situ cells were assembled in an argon-filled glove box,

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structural evolution of Li2BaTi6O14 was observed by JEOL JEM-2010 high-resolution

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transmission electron microscopy. For HRTEM observation, Li2BaTi6O14 powders

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were scraped from the cycled electrodes and dispersed in dimethyl carbonate using

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ultrasonic. After that, the sample was dropped onto copper grid, and then evacuated

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for 5 hours. The transfer of copper grid to the HRTEM chamber was performed within

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thirty seconds under argon blowing.

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3. Results and discussion

Fig. 1 shows the XRD patterns of Li2BaTi6O14 obtained at various calcining

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temperatures from 800 to 1000 oC. Seen from the X-ray diffraction curves, two weak

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impurity diffraction peaks located at 24.42o and 25.84o are detected at the sintering

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temperatures from 800 to 900 oC, which can be ascribed to the (021) crystal face of

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BaCO3 (JCPDS No. 85-0720) and the (111) crystal face of TiO2 (JCPDS No. 29-1360)

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and reveals that the decomposition reaction under 900 oC was not complete. In

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contrast, the XRD patterns of Li2BaTi6O14 synthesized at 950 and 1000 oC are in

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accordance with the previous report [21, 22]. No obvious evidence of diffraction

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peaks from impurity phase is observed in either of two patterns. It suggests that the

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calcining temperature to form high pure Li2BaTi6O14 phase is at least 950 oC during

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the solid state reaction.

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Fig. 2 shows the Rietveld refinement results of the XRD pattern for Li2BaTi6O14

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calcined at 950 oC. The lattice parameters of Li2BaTi6O14 from this analysis are

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a=16.5405 Å, b=11.2452 Å, and c=11.5642 Å, which are in good agreement with

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those reported by D. Dambournet et al [19, 21, 22]. A structural model for this

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material is given in Fig. 3. It is obvious that the structure of Li2BaTi6O14 consists of a

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three-dimensional network constructed by corner- and edge-sharing TiO6 octahedra.

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The tetrahedral and octahedral vacant sites in the structure would allow lithium-ion

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insertion and extraction. The SEM images of the five Li2BaTi6O14 samples calcined at different

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temperatures are presented in Fig. 4. It can be seen that the sizes and morphologies of

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Li2BaTi6O14 materials are different from each other under different calcining

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conditions. The diameter of the Li2BaTi6O14 particles increases with the increase of

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calcining temperature. As shown in Fig. 4a-4f, the size of Li2BaTi6O14 particles

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sintering at 800, 850, and 900 oC is less than 1µm and appears to be non-uniform. By

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increasing the calcining temperature to 950 oC, the particle size increases significantly

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to about 1.5 µm with better crystalline features (Fig. 4g). When the calcining

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temperature is further increased to 1000 oC, the particles agglomerate and melt into

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large particles (Fig. 4h). As the morphology and particle size of a material have great

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effect on its electrochemical performance, the agglomerated particles in the case of

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Li2BaTi6O14 may reduce its specific capacity [30].

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In order to verify the above conjecture, the CV curves of the five samples are

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performed at a scan rate of 0.1 mV s-1 as shown in Fig. 5. For a better comparison, all

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the Li2BaTi6O14 electrodes were used with the same mass of active material during the

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CV test. The data demonstrate that there is no difference in oxidation-reduction

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process between the first and the subsequent cycles. Viewed from Fig. 5a-5c, there are

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three pairs of redox peaks in the CVs of the materials sintering at 800, 850, and 900

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and 1.54 V during discharge, respectively. The main two redox peaks at 1.19/1.16 V

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and 1.49/1.36 V can be contributed to the lithiation-delithiation process between

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Li2BaTi6O14 and Li2+xBaTi6O14. The weak oxidation and reduction peaks located at

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ACCEPTED MANUSCRIPT 1.61 and 1.54 V in their CV curves should be associated with lithium ion

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insertion/extraction within the trace impurity TiO2 lattice, which is attributed to the

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incomplete solid-state reaction under 900 oC. Upon raising the calcining temperature

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to 950 oC or above, only two sharp pairs of redox peaks corresponding to the

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Li2BaTi6O14-Li2+xBaTi6O14 redox couples can be observed in Fig. 5d-5e, indicating

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that the disappearance of impurity TiO2. Of particular significance is that Li2BaTi6O14

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powder sintering at 950 oC presents the best electrochemical activity with well

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separated four peaks and the highest peak current as shown in Fig. 5d. It indicates that

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the lithium-ion intercalation/deintercalation into/out of Li2BaTi6O14 obtained at 950

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The lithiation/delithiation behaviors and electrochemical performance of the as-

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prepared

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charge/discharge tests in a potential range from 0.5 to 2.0 V at a current density of 50

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mA g-1. Viewed from Fig. 6, the charge and discharge curves of Li2BaTi6O14 obtained

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at 950 oC or above have a pair of distinct potential plateaus and two slopes, which are

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corresponding to the redox peaks in the CV profiles in Fig. 5d and 5e. According to

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previous reports, it is known that all the electrochemical energies for lithium storage

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in this compound come from the reversible redox reactions between trivalent titanium

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ion (Ti3+) and tetravalent titanium ion (Ti4+) [31]. For comparison, an additional pair

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of short working plateaus at 1.53/1.61 V can be detected in the charge/discharge

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curves of Li2BaTi6O14 obtained at 800, 850 and 900 oC except for the above

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mentioned electrochemical behaviors as shown in Fig. 5a-5c. This phenomenon is in

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consistent with the redox peaks of impurity TiO2 in the CVs. Besides, electrolyte

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irreversible decomposition is also responsible for the slope between 0.5 and 1.0 V

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during the initial discharge process. As shown in Fig. 6a, the initial reverse charge

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capacities are 144.3, 136.0, 136.5, 145.7 and 151.0 mAh g-1 for Li2BaTi6O14 samples

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obtained at the sintering temperatures of 800, 850, 900, 950, and 1000

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respectively. After 25 cycles, the highest reversible capacity of 142.3 mAh g-1 is

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obtained for Li2BaTi6O14 calcined at the temperature of 950 oC (Fig. 6b). Along with

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the repeated charge/discharge process as shown in Fig. 6c, Li2BaTi6O14 calcined at

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950 oC still can exhibit a reversible capacity of 137.7 mAh g-1 in the 50th cycle, which

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is also higher than the 50th specific charge capacities of 86.7, 99.8, 134.1, and 120.4

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mAh g-1 for samples synthesized at other temperatures (800, 850, 900 and 1000 oC),

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and the detailed charge/discharge capacities for as-prepared samples are presented in

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Table 1. Based on the above analysis, it is clear that the particle size, surface

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morphology and crystallinity originating from different calcining temperatures have

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obvious effect on the electrochemical properties of Li2BaTi6O14.

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The EIS spectra of the five electrodes before cycles and the corresponding fitting

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results using an equivalent circuit are shown in Fig. 7a. All the EIS curves are

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composed of a depressed semicircle in the high frequency region, and an inclined line

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in the low frequency region. The semicircle is approximately related to the charge

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transfer resistance (Rct) for lithium ion reaction at the interface of electrolyte and

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Li2BaTi6O14. According to the fitting results of ZSimpWin software, the charge

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transfer resistance (Rct) of Li2BaTi6O14 calcined at 950 oC is 127.3 Ω, which is

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obviously lower than those of 213.8, 195.9, 151.4, and 187.8 Ω for Li2BaTi6O14

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calcined at 800, 850, 900, and 1000 oC, respectively. This lower Rct result suggests

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that the Li2BaTi6O14 calcined at 950 oC possesses better kinetic behavior. The inclined

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line is attributed to the diffusion of the lithium ions in the bulk material, and the

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lithium ion diffusion coefficient (DLi) can be roughly calculated from the following

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Equation [26, 27]:

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R 2T 2 D= 2 4 4 2 2 2A n F C σ

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Where the meaning of R is the gas constant (8.314 J mol-1 K-1), T is the absolute

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temperature (298 K), A is the surface area of the electrode (1.77 cm2), n is the number

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of electrons transferred in the half-reaction for the redox couple, F is the Faraday

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constant (96500 C mol-1), C is the molar concentration of Li+, and σ is the Warburg

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factor, which has relationship with Z’ [26, 27]:

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Z ' = Re + Rct + σω −1/2

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Where Re is the resistance of electrolyte, Rct is the charge transfer resistance and ω is

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the angular frequency. Both Re and Rct are independent of frequency. σ is obtained

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from the plot slope of Z’ vs. ω-1/2 as shown in Fig. 7b. When the Li+ concentration

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adopts 2.67×10-3 mol cm-3 in the study, the value of DLi is calculated about 1.92×10-17,

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1.73×10-17, 6.48×10-17, 6.73×10-17, and 3.57×10-17 cm2 s-1 for Li2BaTi6O14 calcined at

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800, 850, 900, 950 and 1000 oC, respectively. It is obvious that Li2BaTi6O14

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synthesized at 950 oC has the highest lithium diffusion coefficient among all the five

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samples, which is in consistent with the above cycling performance.

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According to the results discussed above, we can conclude that the most suitable

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temperature to synthesize the Li2BaTi6O14 is 950 oC. Since high rate performance is

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an important factor that needs to be considered in fabricating power batteries in

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industry, further electrochemical analysis is necessary at high current densities. Rate

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performance of Li2BaTi6O14 synthesized at 950 oC is evaluated at different current

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densities from 50 to 300 mA g-1. As shown in Fig. 8a, the reversible capacity at the

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current density of 100 mA g-1 is 140.5 mAh g-1. Increased the current density to 200

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mA g-1, Li2BaTi6O14 can deliver a reversible capacity of 127.4 mAh g-1. Even cycled

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Seen from the discharge curves (Fig. 8a), the delithiation behaviors at high rates are

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almost the same as those obtained at 50 mA g-1. Therefore, Li2BaTi6O14 not only

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displays outstanding high-rate capability but also reveals excellent cycle stability as

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shown in Fig. 8b. These rate cycling results further confirm the good electrochemical

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performance of Li2BaTi6O14 synthesized at 950 oC.

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To illuminate the insertion/extraction behavior of Li2BaTi6O14 synthesized at 950

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structural evolutions by using an in-situ XRD technique. In the in-situ XRD cell,

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beryllium disc is used as the X-ray transmission window and current collector, which

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was oxidized during repeated usage. As shown in Fig. 9a, the diffraction peaks at

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38.70o, 41.36o, and 44.1o are attributed to beryllium oxide, according to the JCPDS

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card No. 78-1557. Seen from Fig. 9c and 9d, it can be found that the characteristic

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diffraction peaks of Li2BaTi6O14 located at 32.7o, 33.6o, 43.7o and 44.9o gradually

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shift towards lower angles after 3.25 Li per formula storage in the structure and then

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return reversibly to their original Bragg positions when it is recharged up to 2.0 V.

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Besides, the diffraction peaks located at 20.4o, 27.8o, 29.9o and 37.1o for the original

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Li2BaTi6O14 disappears along with the lithiation process. The shifting and

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disappearance of diffraction peaks are attributed to Li+ insertion into Li2BaTi6O14 by a

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two-step process, that Li2BaTi6O14 exhibits a flat plateau at around 1.43 V and a slope

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between 0.5 and 1.17 V during the lithium ion insertion in Fig. 6a. Upon recharge

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process, all the diffraction peaks can reappear and move to the pristine Bragg

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positions during delithiation, which is in accordance with the high-degree reversibility

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of the change in relative intensity vs. 2θ patterns as illustrated in Fig. 10. This

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phenomenon can be further proved by ex-situ TEM and HRTEM technique.

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Fig. 11a represents an overall TEM image of Li2BaTi6O14 particles synthesized . It indicates that the size of particles is in the range of 0.5-1.5 µm.

at 950

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Furthermore, ordered crystalline lines are clearly seen in the HRTEM images of Fig.

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11b. The d-spacings of the planes are 2.781 and 5.069 Å, corresponding to the (512)

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and (021) planes of Li2BaTi6O14. These lattice parameters are in accordance with the

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JCPDS card No. 49-0190. After a discharge process to 0.5 V, the structure of particle

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was not destroyed with 3.25 Li per formula storage in Li2BaTi6O14 as the TEM image

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shown in Fig. 11c. Besides, the HRTEM image in Fig. 11d shows that the fringe

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spacing is measured to be 3.748 Å, corresponding to the formation of lithiated

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Li2BaTi6O14. Compared with Fig. 11c, it can be found that Li2BaTi6O14 particle still

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holds its stable structure during delithiation process, and the fringe spacing is found to

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be 5.071 Å (Fig. 11f), which can be attributed to the (021) plane of Li2BaTi6O14

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(JCPDS card No. 49-0190). These results are in good agreement with the in-situ XRD

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patterns. Based on these electrochemical behaviors, in-situ XRD patterns and ex-situ

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HRTEM images, it is known that the phase transition of Li2BaTi6O14 is highly

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reversible and this compound will be energy favorable as high power anode material,

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4. Conclusions

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In this work, Li2BaTi6O14 is prepared by a simple solid-state method between

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800 and 1000 oC. It can be found that pure phase Li2BaTi6O14 is obtained at a

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sintering temperature of 950 oC or above. Electrochemical testing manifests that the

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Li2BaTi6O14 calcined at 950 oC has the best electrochemical properties among all the

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as-prepared samples. The reversible capacity is 137.7 mAh g-1 at a current density of

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50 mA g-1 for Li2BaTi6O14 calcined at 950 oC, and the capacity retention is 94.51 %

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over 50 cycles. Furthermore, EIS analysis also presents the highest lithium ion

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diffusion coefficient of Li2BaTi6O14 calcined at 950

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insertion/extraction among all the as-prepared samples. As a result, Li2BaTi6O14

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obtained at 950 oC demonstrates the remarkable rate performance with a high capacity

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of 118 mAh g-1 at the current density of 300 mA g-1. Besides, the phase transition of

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Li2BaTi6O14 is highly reversible as proved by in-situ XRD and ex-situ HRTEM

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techniques. Therefore, this material can be a potential anode candidate for lithium-ion

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batteries.

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Acknowledgements

This work is sponsored by National 863 Program (2013AA050901), Ningbo Key

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C during lithium ion

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Innovation

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(2014A610042). The work is also supported by K.C. Wong Magna Fund and

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Outstanding Dissertation Growth Foundation of Ningbo University (No. PY2014004).

Team

(2014B81005)

Ningbo

Natural

Science

Foundation

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and

References

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Mg0.5Zn0.5) nanowires with enhanced electrochemical lithium storage, Functional

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Lithium storage behavior of manganese based complex spinel titanate as anode

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material for Li-ion batteries, Journal of Power Sources 272 (2014) 622-628.

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titanate as an advanced anode material for rechargeable lithium-ion batteries,

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chemistry and physical properties of complex lithium spinels Li2MM'3O8 (M=Mg,

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of high packing density SrLi2Ti6O14 for use as anode in 2.7-V lithium-ion battery,

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Electrochemical performance of LiCoO2/SrLi2Ti6O14 batteries for high-power

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applications, Journal of Power Sources 245 (2014) 371-376.

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Alloys and Compounds 389 (2005) 47-54.

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Copper/carbon coated lithium sodium titanate as advanced anode material for

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lithium-ion batteries, Journal of Power Sources 259 (2014) 177-182.

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Electrochemistry Communications 11 (2009) 1251-1254.

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application of a novel Li4Ti5O12 composite as anode material with enhanced fast charge-discharge performance for lithium-ion battery, Electrochimica Acta 134 (2014) 377-383.

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synthesis for lithium-ion battery, Ceramics International 40 (2014) 9853-9858.

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nanobelts and their lithium storage behavior studied by in situ X-ray diffraction,

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titanate anode material, Ionics 17 (2011) 503-509.

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phosphate/carbon composites as cathode materials for lithium-ion batteries,

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property of Li4Ti5O12 as an anode material for lithium-ion batteries,

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Electrochimica Acta 53 (2008) 7242-7247.

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Table caption

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Table 1. Charge/discharge specific capacities of five Li2BaTi6O14 samples obtained at

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different calcining temperatures.

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ACCEPTED MANUSCRIPT Figure captions

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Fig. 1. The XRD patterns of BaLi2Ti6O14 obtained at different temperatures. (a) 800 oC, (b)

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850 oC, (c) 900 oC, (d) 950 oC and (e) 1000 oC.

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Fig. 2. XRD refinement of Li2BaTi6O14 obtained at 950 oC.

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Fig. 3. The crystal structure of Li2BaTi6O14 before (a) and after (b) lithium storage.

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Fig. 4. SEM images of BaLi2Ti6O14 obtained at different temperatures. (a, b) 800 oC, (c, d)

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850 oC, (e, f) 900 oC, (g) 950 oC and (h) 1000 oC.

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Fig. 5. Cyclic voltammogram curves of Li2BaTi6O14 calcined at different temperatures. (a)

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800 oC, (b) 850 oC, (c) 900 oC, (d) 950 oC and (e) 1000 oC.

449

Fig. 6. The (a) 1st, (b) 25th, (c) 50th charge-discharge curves and corresponding cycling

450

properties (d) of Li2BaTi6O14 calcined at different temperatures at a current density of 50

451

mA g−1.

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Fig. 7. (a) Electrochemical impedance spectra of Li2BaTi6O14 calcined at different

453

temperatures, (b) the relationship between Z’ and ω-1/2 in low frequency region and (c) the

454

relationship between diffusion coefficient and calcination temperature.

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Fig. 8. (a) The charge-discharge profiles at different current densities and (b) the

456

corresponding rate performance of Li2BaTi6O14 calcined at the temperature of 950 oC.

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Fig. 9. (a) Overall in-situ XRD patterns and (b, c) Selected in-situ XRD patterns of

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Li2BaTi6O14 calcined at the temperature of 950 oC during the initial charge-discharge

459

process.

460

Fig. 10. Images of change in intensity vs. 2θ in in-situ XRD patterns of Li2BaTi6O14

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cycled in 1.0-3.0 V.

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Fig. 11. TEM and HRTEM images of (a, b) pristine Li2BaTi6O14, (c, d) Li2BaTi6O14

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discharged to 0.5 V and (e, f) Li2BaTi6O14 recharged to 3.0 V.

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ACCEPTED MANUSCRIPT Table 1. Charge/discharge specific capacities of five Li2BaTi6O14 samples obtained at different calcining temperatures. Capacity (mAh g-1) State 25th

Charge

144.3

109.6

86.7

Discharge

265.2

112.2

88.2

Charge

136.0

123.6

99.8

Discharge

259.3

128.4

104.1

o

Li2BaTi6O14-800 C

o

Charge

136.5

135.9

134.1

Discharge

246.8

136.9

134.9

Charge

145.7

142.3

137.7

Discharge

266.8

144.3

140.8

Charge

151.0

132.7

120.4

Discharge

257.9

136.3

122.6

o

Li2BaTi6O14-900 C

o

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(312) (113) (131) (420) (421) (023)(132) (511)(331) (004) (204)(512) (240) (241) (024) (314) (224) (404) (441) (424) (712) (800) (044) (802) (821) (425)(515)

(020) (021) (112) (311) (220) (221)

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ACCEPTED MANUSCRIPT Li2BaTi6O14(Sim) Li2BaTi6O14(Exp)

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Difference Observed Reflections

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2 Theta (degree)

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50

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Fig. 3. The crystal structure of Li2BaTi6O14 before (a) and after (b) lithium storage.

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Fig. 4. SEM images of BaLi2Ti6O14 obtained at different temperatures. (a, b) 800 oC, (c, d) 850 oC, (e, f) 900 oC, (g) 950 oC and (h) 1000 oC.

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(a)

0.30

Current (mA)

Current (mA)

1 st 2 nd 3 rd

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Potential (V)

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800 C o 850 C o 900 C o 950 C o 1000 C

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Fig. 9. (a) Overall in-situ XRD patterns and (b, c) Selected in-situ XRD patterns of

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Fig. 10. Images of change in intensity vs. 2θ in in-situ XRD patterns of Li2BaTi6O14

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Fig. 11. TEM and HRTEM images of (a, b) pristine Li2BaTi6O14, (c, d) Li2BaTi6O14

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Highlights

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Lithium barium titanate: A stable lithium storage material for lithium-ion batteries

Xiaoting Lin, Peng Li, Lianyi Shao, Miao Shui, Dongjie Wang, Nengbing Long,

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Yuanlong Ren, Jie Shu*

Submitted to Journal of Power Sources


High pure Li2BaTi6O14 is synthesized by a traditional solid-state method.

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Li2BaTi6O14 calcined at 950 oC exhibits the best electrochemical properties.
Li2BaTi6O14 reveals a reversible capacity of 137.7 mAh g-1 after 50 cycles

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In-situ XRD proves the reversibility of Li2BaTi6O14 during cycles.