Template-Engaged Synthesis of 1D Hierarchical Chainlike LiCoO2

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Template-engaged synthesis of 1D hierarchical chainlike LiCoO2 cathode materials with enhanced high-voltage lithium storage capabilities Naiteng Wu, Yun Zhang, Yunhong Wei, Heng Liu, and Hao Wu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b09159 • Publication Date (Web): 02 Sep 2016 Downloaded from http://pubs.acs.org on September 6, 2016

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ACS Applied Materials & Interfaces

Template-engaged Synthesis of 1D Hierarchical Chainlike LiCoO2 Cathode Materials with Enhanced High-voltage Lithium Storage Capabilities Naiteng Wu, †‡ Yun Zhang, †,* Yunhong Wei, † Heng Liu † and Hao Wu, †,* †

College of Materials Science and Engineering, Sichuan University, Chengdu,

610064, P. R. China. ‡

College of Chemistry and Chemical Engineering, Luoyang Normal University,

Luoyang, 471934, P. R. China.

* Corresponding authors. E-mail: [email protected] and [email protected]

ABSTRACT: A novel 1D hierarchical chainlike LiCoO2 organized by flake-shaped primary particles is synthesized via a facile template-engaged strategy by using CoC2O4·2H2O as a self-sacrificial template obtained from a simple coprecipitation method. The resultant LiCoO2 has a well-built hierarchical structure, consisting of secondary micrometer-sized chains and submicrometer-sized primary flakes, whilst these primary LiCoO2 flakes have specifically exposed fast-Li+-diffused active {010} facets. Owing to this unique hierarchical structure, the chainlike LiCoO2 serves as a stable cathode material for lithium-ion batteries (LIBs) operated at a high cutoff voltage up to 4.5 V, enabling highly reversible capacity, remarkable rate performance, and long-term cycle life. Specifically, the chainlike LiCoO2 can deliver a reversible 1

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discharge capacity as high as 168, 156, 150, and 120 mA h g−1 under the current density of 0.1, 0.5, 1, and 5 C, respectively, while about 85% retention of the initial capacity can be retained after 200 cycles under 1 C at room temperature. Moreover, the chainlike LiCoO2 also shows an excellent cycling stability at a wide operating temperature range, showing the capacity retention of ~73 % after 200 cycles at 55 ºC and of ~68 % after 50 cycles at -10 ºC, respectively. The work described here suggests the great potential of the hierarchical chainlike LiCoO2 as high-voltage cathode materials aimed towards developing advanced LIBs with high energy density and power density.

KEYWORDS: LiCoO2, Chainlike morphology, hierarchical structure, cathode material, lithium-ion batteries

1. INTRODUCTION: LiCoO2, as one of the most commonly used cathode materials, has been widely applied for lithium ion batteries (LIBs) owing to its high energy density and stable cycle life, despite its high price and slight toxicity.1 Nevertheless, LiCoO2 only exert half (~140 mAh/g) of its theoretical capacity at 4.2 V to balance the relationship of cycling stability and capacity.2 Rising the operation voltage (> 4.2 V) is an effective route to yield higher capacity of LiCoO2, along with increased energy density of cells.3 Unfortunately, the layered structure of Li1-xCoO2 easily collapses at x >0.5, once the operation voltage increases beyond 4.2 V.3-5 The large lattice expansion of 2


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Li1-xCoO2 along the c axis during delithiation process is the main factor responsible for the structural instability, thus giving rise to rapid capacity decay of cells.2,6 Surface modifying2,7,8 and cation doping9,10 have been intensively implemented to address the above issues. Unfortunately, most of the approaches commonly undergo the lost of reversible capacity and the fail in structure integrity.11 Alternatively, nanostructured LiCoO2 cathode materials can realize improved electrochemical activities due to drastically reduced ionic diffusion length and enlarged electrode-electrolyte contact area.12,13 To date, various nanostructures of LiCoO2 including nanoplates,14 nanowire,12,15 and nanospheres16 have been widely reported. In particular, one-dimensional (1D) nanostructures, such as nanotube, nanowire and nanorod, are extraordinarily appealing, because they not only efficiently reduce the diffusion length for Li+ ions, but also ensure sufficient electrode-electrolyte contact areas through its large surface-to-volume ratio of the 1D nanostructure.17,18 For example, Chen et al. synthesized LiCoO2 nanotubes exhibiting higher discharge capacity over its nanoparticles counterpart.19 Such a positive effect has also been sighted on other types of cathode materials, like LiMn2O4 nanorods,17 FeF3 nanowires18 and LiNi0.8Co0.15Al0.05O2 microrods.20 Nevertheless, owing to the larger specific surface area, nanostructured LiCoO2 electrodes are prone to undergo severe side reactions with electrolyte more than their bulk counterparts,13 especially at a high cutoff voltage (e.g. 4.5 V).21,22 Moreover, some complicated and tedious procedures are often involved in the synthesis of the nanomaterials, which could be a significant problem for scalable production and subsequent LIBs applications. 3



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Recently, hierarchical micro/nanostructures have attracted considerable attention because their submicron-sized primary particles can significantly shorten the transport paths both for Li+ ions and electron, meanwhile the micrometer-sized secondary agglomerate can endow the hierarchical electrode materials with longer cycle life over their nanostructured and bulk counterparts.23,24 In this regard, it is of great significance to develop novel strategies for elaborate design and fabrication of LiCoO2 materials which possesses well-defined hierarchical architectures with enhanced high-voltage lithium storage properties. Taking these into consideration, in this work, we report a simple surfactant-free synthetic strategy to fabricate highly uniform 1D hierarchical chainlike LiCoO2 (denoted as LCO-chain), which is based on using cobalt oxalate microrods as both precursors and self-sacrificial templates. The synthetic strategy was illustrated in Figure 1a. CoC2O4·2H2O microrods, serving as precursors owing to their characteristic 1D rodlike architectures (Figure S1a), were first prepared using oxalic acid as precipitant by a simple and surfactant-free coprecipitation approach. The resultant rod-like CoC2O4·2H2O precursors were then lithiated, and further converted into the final product of 1D hierarchical LiCoO2 chains. For the purpose of comparison, we also adopted a commercial LiCoO2 (denotes as LCO-com) as the counterpart of the LCO-chain, and evaluate their electrochemical performances in terms of discharge capacities and rate capabilities at 4.5 V, as well as especially the cycling properties in a temperature range from -10 to 55 °C.

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Figure 1. Schematic diagram of (a) the synthetic route of LCO-chain and (b and c) the crystal structure of LiCoO2. 2. EXPERIMENTAL SECTION 2.1. Preparation of CoC2O4·2H2O microrods. CoC2O4·2H2O microrod precursors were obtained through a conventional precipitation method without any surfactant. Typically, 30 mmol of CoSO4·7H2O (Analytical Reagent, A.R.) was first dissolved in 100 mL of aqueous solution. After that, CoSO4 solution was slowly added to 120 mL of H2C2O4 solution (0.3 mol/L) under vigorous stirring at room temperature. After continue stirring for 2 h, the pink suspension was filtered, washed and finally dried at 80 ºC to get the CoC2O4·2H2O microrods. 2.2. Synthesis of chainlike LiCoO2. Chainlike LiCoO2 products were prepared by employing a solid-state reaction method. Typically, the as-obtained CoC2O4·2H2O precursors were mixed thoroughly with excess Li2CO3 (A.R.) in a molar ratio of Co: Li = 1: 1.02. The mixture was first heated at 600 ºC for 5 h, and then sintered at 850 ºC for 15 h to obtain the final chainlike LiCoO2 samples (denoted as LCO-chain).

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For the purpose of comparison, a nanosized LiCoO2 counterpart (denoted as LCO-nano) with a similar 1D wirelike morphology was synthesized according to the previously literature.12 Besides, a commercial LiCoO2 counterpart (denoted as LCO-com) was also purchased from Beijing Mengguli Power Source Tech. Co. LTD. 2.3. Materials Characterization X-ray diffraction was performed to detect the phase purity and crystal structure of all samples using a Bruker DX-1000 with Cu Kα radiation in the 2θ angular range from 10º to 70º. The morphology and microstructure of the samples were characterized by scanning electron microscope (SEM; Hitachi S-4800, 15 kV), coupled with energy dispersive spectroscopy (EDS; Oxford Instrument), and transmission electron microscope (TEM; JEOL JEM-2100F, 200 kV). The specific surface areas of the LiCoO2 samples were determined by Nitrogen sorption measurements (Tristar 30 instrument, Micromeritics). 2.4. Electrochemical Performance Measurements The electrochemical measurements were performed using CR2032 coin-type cells and the detailed processes of the cells preparation are the same as that in our previous work.20 The cells were evaluated on the Neware test system (Shen Zhen, CT-3008W) under the current densities varying from 0.1 to 5 C (1 C=140 mA g-1) in the voltage range of 2.7 ~ 4.3/4.5 V versus Li/Li+. All of the charge-discharge evaluations were operated at room temperature, 55, and -10 ºC. Specifically, the measurements either at 55 or -10 ºC were performed by using a high/low 6


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temperature test chamber (SDH6005, Chongqin Yingbo Co.), in which the cells were placed and the working temperature was maintained at 55 or -10 ºC during the whole charge/discharge process. The electrochemical impedance spectra (EIS) tests were conducted on a CHI600E electrochemical workstation (Shanghai Chenhua Co.) The EIS measurements were performed over a frequency range of 100 kHz to 10 mHz with an applied amplitude of 5 mV.

3. RESULTS AND DISCUSSIONS The morphology and crystal structure of the prepared CoC2O4·2H2O precursors were first characterized using SEM and XRD. As shown in the SEM image (Figure 2a), the CoC2O4·2H2O precursors exhibit micron-sized rod-shaped morphology under the SEM observation, and these 1D structured microrods are generally uniform and monodispersed with 1-2 µm in width and 15-20 µm in length. Figure 2b presents the XRD pattern of the CoC2O4·2H2O precursors, in which all the diffraction peaks of precursor correspond well to the standard CoC2O4·2H2O (JCPDS: 25-0250).

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Figure 2. (a) SEM images and (b) XRD pattern of the as-prepared CoC2O4·2H2O precursors

After sintering the CoC2O4·2H2O precursors with Li2CO3 for 5, 10, and 15 h, respectively, all the diffraction peaks of the as-prepared samples can be indexed to a typical α-NaFeO2 layered structure, as shown in Figure 3a. The distinct split doublets of (006)/(102) and (018)/(110) indicate the ordered distribution of Co3+ and Li+ in the lattice.25 By prolonging the sintering times, the intensity of the diffraction peaks is gradually increased, especially toward the peak of (003). The crystal parameters of the resultant samples were summarized in Table S1. The

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crystal parameters like c, c/a, I(003)/I(104) and d(006) became enlarged with the extension of sintering times from 5 to 15 h. The largest c/a ratio of the LCO-chain sintering at 15 h implies that the lattice has preferentially grown along the c axis, while the largest lattice distance of (006) reflects its high integrity and orderliness of the layered hexagonal structure.25 As the counterparts, the commercial and prepared nanosized LiCoO2 also show the well-defined layered structure, as proved by their XRD pattern (Figure S1).

Figure 3. XRD patterns (a) and SEM images of the samples sintered at different times, (b) 5 h, (c) 10 h, (d) 15 h The detailed morphology features of samples were further characterized using SEM and TEM. The SEM images, shown in Figure 3b-d, first reveal the morphology evolution of the samples upon the sintering time from 5 to 15 h. 9



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Obviously, the 1D chainlike morphology can be formed at the incipient stage during the sintering process, suggesting that the oxalate precursors are easy to react with the lithium salts at this sintering temperature. Combining with above XRD analysis, it is demonstrated that the layer structure together with the chainlike shape of the LiCoO2 samples can be indeed improved and stabilized by increasing the sintering times. Figure 4a shows the panoramic SEM image of the LCO-chain, which exhibits the typical 1D rodlike morphology, indicative of a well structure inheritance from the microrod precursors even after high temperature solid state reaction with lithium salts. However, a closer SEM observation (Figure 4b) depicts that different from the smooth rodlike morphology of the CoC2O4·2H2O precursors, the surface of the 1D-structured LiCoO2 product is pretty rough with irregular particles stacked presumably due to the growth of primary crystals in the high temperature sintering process, and accordingly its morphology appears like a “iron chain” with about 15-20 µm in length and 0.5-1 µm in width. As further revealed from the magnified SEM images (Figure 4c), a single micro-sized chain is composed of numerous flake-shaped primary particles with about 200-300 nm in thickness and 200-800 nm in width, while these submicron-sized primary LiCoO2 flakes are linked together, and act as building blocks to be well organized into the 1D hierarchical chainlike architecture. Notably, the overall 1D morphology of the LCO-chain is similar to that of the LCO-nano counterpart. As shown in Figure S2a, the LCO-nano are composed of many nanosized primary particles and display a 1D 10


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hierarchical wirelike secondary structure with a smaller size dimension of about 200 nm in diameter and 20 µm in length. This morphology feature is almost consistent with the reported literature.12 In addition, the SEM image of the commercial LiCoO2, as shown in Figure S2b, reveals that it consists of bulk particles with irregular shape and uneven size dimension. The nitrogen adsorption-desorption analysis of samples, as showed in Figure S3, indicating that the BET specific area of LCO-chain is about 1.84 m2 g-1, slightly larger than that of the LCO-com (0.31 m2 g-1) but smaller than that of the LCO-nano (20.4 m2 g-1). This demonstrates that in addition to ensuring the contact between electrode and electrolyte, such appropriate specific surface area of the LCO-chain would also allow to optimize the electrochemical activity and minimize unfavorable side reaction in subsequent electrochemical evaluation, compared with its bulk and nanosized counterpart, respectively.

Figure 4. (a-c) SEM images of the prepared chainlike LiCoO2 products at different 11



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magnification; (d) Typical TEM images of LCO-chain; (e1 and f1) Magnified TEM images from the lateral (e1) and frontal view (f1) of a single primary particle derived from the marked square region in (d); (e2 and f2) HRTEM images derived from the red square region in (e1) and (f1), and their relevant (e3 and f3) SAED patterns.

Detailed structure features of LCO-chain were further investigated using TEM and HRTEM. As shown in Figure 4d, a chainlike morphology of the LCO-chain is coincident with the above SEM analysis. Moreover, Figure 4e1 and 4f1 clearly show that the secondary LiCoO2 chain is mainly constructed by organization of flake-shaped primary particles with distinct sidewall and surface. Notably, the HRTEM image (Figure 4e2) from the lateral plane of a single primary flake in Figure 4e1 clearly shows two sets of lattice fringes with the interplanar distances of ~2.39 and ~4.64 Å at an angle of 80°, being consistent with the d-spacings of the (101) and (003) facets of LiCoO2, respectively. This observation indicates that this lateral plane of the flake is the (010) facet. Besides, the selected area electron diffraction (SAED) in Figure 4e3 clearly exhibits an array of parallel symmetry dots, proving that this primary flake is single-crystalline with a hexagonal crystal structure enclosed by {010} facets. Furthermore, Figure 4f2 depicts the lattice fringes of the frontal plane displayed in Figure 4f1, in which the lattice spacings are measured to be ~2.39 Å at an angle of 120°, corresponding to the (100) and (010) facet of LiCoO2, respectively. Combined with the corresponding SEAD pattern (Figure 4f3), an array of hexagonal symmetry dots reveals that this frontal plane of this flake is the (001) facet. In light of the crystal structure of LiCoO2, as illustrated in Figure 1, it is shown that Li+ ions are 12


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difficult to transport through the closed-packed {001} facets, as shown in Figure 1b, whereas the {010} facets are perpendicular to the {001} facets, and possess open 2D interlayer spaces to favor the transportation of Li+ ions along the a- and b-axis as shown in Figure 1c. This indicates that the flake-shaped primary LiCoO2 particles possess a preferential crystallographic orientation for Li+ migration, i.e. {010} facets on the straight edges, where the Li+ ions can intercalate/deintercalate through these electrochemically active crystal facets, thus helping to improve the rate capability of the 1D chainlike LiCoO2 materials. Given the unique 1D hierarchical architecture, LCO-chain promises to serve as a superior cathode material for LIBs. The electrochemical properties of products were first evaluated at a commonly used voltage range of 2.7-4.3 V. Figure S4a shows the typical initial charge/discharge curves of LCO-chain and LCO-com at 0.1 C. The initial discharge capacity of LCO-chain is about 151 mAh g-1, close to that of LCO-com (153 mAh g-1). Moreover, the LCO-chain delivers a good capacity retention as high as 89 % after 100 cycles under 1 C rate (Figure S4b), which is almost the same as the LCO-com (88.5 %), depicting that the electrochemical performance of the as-prepared LCO-chain is comparable to that of the commercial LiCoO2 when operated in 2.7 - 4.3 V voltage range. As known, increasing the operation voltage (≥ 4.3 V) is able to yield higher capacity of LiCoO2-based cell. Hence, we further carried out the electrochemical measurements by elevating the cutoff voltage up to 4.5 V. Figure 5a presents the initial charge/discharge curves of the three cells, i.e. LCO-chain, LCO-com, and 13



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LCO-nano, in 2.7 - 4.5 V at 0.1 C, where both of LCO-chain and LCO-com deliver about 168 mAh g-1 of initial discharge capacity, much higher than that with 4.3 V cutoff voltage. During the initial discharge process, the LCO-nano exhibits the longest discharge plateau and reaches about 188 mAh g-1. The improved discharge capacity of LCO-nano should be owing to its nanosized primary particles, which endow the electrode materials with increased electrochemical activity and larger contact area with the electrolyte, resulting in more efficient intercalate/deintercalate process of Li ion. The comparison of the rate properties from 0.1 to 5 C was displayed in Figure 5b. Owing to the low diffusion rate of the Li+ ions into/off electrode at high rates,26 the capacities of the three cells decrease as the cycling current density increases. The LCO-chain is still able to deliver a stable discharge capacity of 168, 164, 156, 150, 140, and 120 mAh g-1 when cycled at the current density of 0.1, 0.2, 0.5, 1, 2, and 5 C, respectively. Notably, the discharge capacity of LCO-chain under 5 C can reach to 120 mAh g-1, much higher than that of LCO-com (52 mAh g-1) and LCO-nano (81 mAh g-1). When the current density was reversed back to 0.1 C after rate cycling measurements, a stable high discharge capacity of 165 mAh g-1 can be recovered for LCO-chain, whereas its counterparts show obvious capacity decay after the rate tests. Hence, the excellent rate property of LCO-chain can be attributed to the unique chainlike hierarchical architecture together with specifically exposed active crystallographic orientation for Li+ migration. Figure 5c presents the cycling performances of LCO-chain, LCO-com, and LCO-nano under 1 C in 2.7-4.5 V. Obviously, the LCO-chain exhibits an excellent 14


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cyclic stability at the high cutoff voltage, since it retains about 85 % of the initial capacity (154 mAh g-1) at the end of 200 cycles. Oppositely, the LCO-com exhibits an inferior cycle life because only about 20 mAh g-1 (13 % retention) can be delivered after the same cycling evaluation. The LCO-nano also delivers inferior cycle retention after only 100 cycles (45% retention). The different cycling performance of LCO-nano between our work and ref. 12 also confirms that the high cut-off voltage would deteriorate the cycling stability of LiCoO2-based materials. This indicates that the synthesized LCO-chain possesses a remarkably improved high-voltage cycling stability over the commercial and nanosized LiCoO2. Moreover, Figure 5d displays a clear difference in the Nyquist plots between LCO-chain and LCO-com cells with the electrochemical impedance spectroscopy evaluation. The resistances of both cells were fitted by an equivalent circuit, as shown in the inset of Figure 5d. Notably, the charge transfer resistance (Rct) for the LCO-chain is about 138.7 Ω, much smaller than that for the commercial LiCoO2 (Rct=732.1 Ω, Table S2).

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Figure 5. (a) Initial charge and discharge curves of electrodes in 2.7-4.5 V under 0.1 C; (b) Rate capability under different current rates, (c) Cycling performances of the electrodes in 2.7-4.5 V under 1 C at 25 °C and (d) Nyquist plots of the LCO-chain and LCO-com electrodes at a charge state of 4.5 V after 200 cycles under 1 C at room temperature. This observation highlights the advantage of the robust 1D hierarchical chainlike structure of LCO-chain which might effectively facilitate the charge/mass transfer at the electrode−electrolyte interface during the electrochemical process. Furthermore, the Li+ ion diffusion coefficient of the LCO-chain is approximately 9.7 times larger than that of the LCO-com (listed in Table S2), also confirming that the hierarchical LCO-chain materials, organized by flake-shaped building blocks that own electrochemically active crystal facets, can effectively shorten the pathways for Li+ 16


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diffusion as compared to the bulk commercial LiCoO2. More importantly, the superior rate and cycling performances of the chainlike LiCoO2 are competitive to most of the reported nanosized LiCoO2-based cathode materials like LiCoO2 nanowires, nanospheres, and nanoplates, as well as the surface-modified LiCoO2 ones (see details in Table S3 for comparison). Figure 6a and 6b present the SEM images of the LCO-chain and LCO-com electrodes after 200 cycles in 2.7-4.5 V under 1C. Notably, the initial structural integrity of the LCO-chain (Figure 6a) has been well maintained at the end of long-term cycling test. However, the structure of LCO-com (Figure 6b) has changed, as broken particles and terraced surface are noticeable on the cycled electrode.4,27 Further structure and morphology analyses using TEM (Figure 6c) show that LCO-chain is almost no change in the morphology. From the corresponding FFT pattern (Fast Fourier Transform), there can be observed an array of hexagonal symmetry dost, proves that the LCO-chain maintain the hexagonal layered structure after long high cut-off voltage cycles. The TEM result of cycled LCO-com is same as the SEM analyses, there is an obvious section in Figure 6d, which is much different from the initial commercial LiCoO2. Besides, the corresponding FFT pattern of LCO-com also reveals the change of crystal phase after long-term cycles.

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Figure 6. SEM and TEM images of (a, c) LCO-chain and (b, d) LCO-com electrodes after 200 cycles under 1 C and their corresponding (e) XRD patterns, e1 and e2 show the (003) peak of the initial (dash line) and cycled (solid line) electrode materials, respectively. Additional XRD analyses (Figure 6e) as well suggest that a good layered structure still remains for the LCO-chain electrode material, but there is an obvious impurity peak in the XRD pattern of the LCO-com, implying a possible degradation of the LCO-com electrode after cycles. Figure 6e1 and e2 compare the intensity and position of the (003) diffraction peak for the LCO-chain and LCO-com before and

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after cycling. It can be clearly seen that both the intensity and position of such characteristic peak for the LCO-chain have almost not changed after cycling, but there is an obvious decline and shift toward this diffraction peak for the LCO-com, confirming that it would undergo a structural deform after the repeated charging and discharging. All these indicate that the hierarchical chainlike LiCoO2 is able to tolerate the stress from the volume expansion and alleviate the irreversible phase transition during the repeated cycles.

Figure 7. Cycling performance and corresponding Coulombic efficiency of the cells under 1 C at (a) 55 ºC and (b) -10 ºC The capability of working at a wider temperature range is an important performance index to evaluate electrode materials for LIBs. Hence, the electrochemical performances of LCO-chain cathode operated at 55 and -10 °C were 19



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also been evaluated in 2.7-4.5 V. Impressively, the LCO-chain cathode material still possesses an outstanding cycling stability under the elevated temperature (The initial charge-discharge curves were shown in Figure S6a). As shown in Figure 7a, the LCO-chain can retain about 73% of the initial capacity (163 mAh g-1) after 200 cycles at 55 °C under 1 C rate, much better than the LCO-com (72 mAh g-1, 44% retention) even at the end of 100 cycles. Figure S6b further displays the initial charge-discharge curve of LCO-chain operated at -10 °C under 0.1 C rate. Obviously, the polarization for the LCO-chain electrode became more serious, mainly due to the relatively lower concentration of Li+ ions throughout the electrode surface.9,28 However, the LCO-chain still exhibits an intriguing low-temperature electrochemical activity, delivering a discharge capacity as high as 163 mAh g-1. Following cycling test for LCO-chain at -10 °C under 1 C rate, as depicted in Figure 7b, also demonstrates that although an obvious decline in capacity appears during cycling, this electrode can still remain 104 mAh g-1 (68 % retention) after 50 cycles. These valued features promise a wide working temperature range for the LCO-chain when served as a stable cathode material for high-voltage LIBs.

4 CONCLUSIONS In summary, we reported a facile strategy to synthesize a novel 1D hierarchical chainlike LiCoO2 organized by submicron-sized primary flakes for high-voltage lithium storage. The hierarchical LiCoO2 chains were synthesized via a template-engaged approach by using cobalt oxalate microrods as both precursor and 20


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self-sacrificial templates. The well-organized chainlike structure along with flake-shaped building block give rise to many appealing features, especially a robust 1D architecture and preferential 2D Li+ diffusion channel. By virtue of the unique structural advantages, the as-prepared hierarchical LiCoO2 chains manifest improved reversible capacity, high rate capability, and cycling performances at room, elevated, and subzero temperatures when served as high-voltage cathodes for LIBs. ACKNOWLEDGMENT This work is financially supported by the National Natural Science Foundation of China (51502180), the National Basic Research Program of China (973 program 2013CB934700), Foundation for the Author of National Excellent Doctor Dissertation of P. R. China (no. FANEDD201435), and the Fundamental Research Funds for the Central Universities (2016SCU04A18)

SUPPORTING INFORMATION The Supporting Information is available free of charge on the ACS Publications website at DOI: Details are provided for additional XRD, SEM, N2 adsorption/desorption, electrochemical performance data, the EIS data and the performance comparison with previously reported LiCoO2 cathode materials.

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Table of Contents Figure

25


Template-Engaged Synthesis of 1D Hierarchical Chainlike LiCoO2

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