GeO2-Ordered Mesoporous Carbon Nanocomposite for

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Ge/GeO2-ordered mesoporous carbon nanocomposite for rechargeable lithium-ion batteries with a long-term cycling performance Lingxing Zeng, Xiaoxia Huang, Xi Chen, Cheng Zheng, Qingrong Qian, Qinghua Chen, and Mingdeng Wei ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.5b08470 • Publication Date (Web): 14 Dec 2015 Downloaded from http://pubs.acs.org on December 21, 2015

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ACS Applied Materials & Interfaces

Ge/GeO2-ordered mesoporous carbon nanocomposite for rechargeable lithium-ion batteries with a long-term cycling performance Lingxing Zeng,a,b,c Xiaoxia Huang,a Xi Chen,a Cheng Zheng,b Qingrong Qian,*a, c Qinghua Chen,a, c and Mingdeng Wei*b a

Engineering Research Center of Polymer Green Recycling of Ministry of Education, College of

Environment Science and Engineering, Fujian Normal University, Fuzhou, Fujian 350007, China b

c

Institute of Advanced Energy Materials, Fuzhou University, Fuzhou, Fujian 350002, China

Fujian Key Laboratory of Pollution Control & Resource Reuse, Fuzhou, Fujian 350007, China

ABSTRACT: Germanium-based nanostructures are receiving intense interest in lithium-ion batteries because they have ultrahigh lithium ion storage ability. However, the Germaniumbased anodes undergo the considerably large volume change during the charge/discharge processes, leading to a fast capacity fade. In the present work, Ge/GeO2-ordered mesoporous carbon (Ge/GeO2-OMC) nanocomposite was successfully fabricated via a facile nanocasting route by using mesoporous carbon as a nano-reactor, and was then used as anode for lithium-ion batteries. Benefited from its unique 3-dimensional ‘meso-nano’ structure, the Ge/GeO2-OMC nanocomposite exhibited large reversible capacity, excellent long-time cycling stability and high

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rate performance. For instance, a large reversible capacity of 1018 mA h g-1 was obtained after 100 cycles at a current density of 0.1 A g-1, which might be attributed to the unique structure of Ge/GeO2-OMC nanocomposite. In addition, a reversible capacity of 492 mA h g-1 can be retained when cycled to 500 cycles at a current density of 1 A g-1.

KEYWORDS: Ge/GeO2-OMC, nanocomposite, nanoreactor, long cycle life, lithium-ion batteries

1. Introduction Nowadays, lithium-ion batteries (LIBs) are widely used as a renewable power source for portable electronic devices because of their high energy density, environmental friendliness and safety. As well known, graphite, the currently commercialized anode electrode possesses a low theoretical capacity (~372 mA h g-1) and hardly meets the ever increasing requirements for high power density and long cycle life of LIBs.1-5 This impels us to design novel high performance anode materials for substituting graphite.6-14 A great deal of recent researches have been devoted to Ge-based anodes that are considered as an alternative to commercial graphite because of their high theoretical capacity (1623 mA h g-1 for Ge, 2152 mA h g-1 for GeO2)

15-16

and faster charge transfer properties. Nevertheless, Ge-

based anodes undergo large volume changes and progressive agglomeration during the electrochemical reaction process, resulted in a rapid capacity fade and the end of cycle life.17-19 Considerable efforts have been made to improve their electrochemical performance, such as fabricating low dimensional nanostructure, designing hollow/porous structure and developing carbon hybrid nanocomposite.20-25 A cluster Ge/C nanostructure displayed an exceptionally high


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rate capability up to the 64 A g-1.26 Nano-GeO2/MC composite delivered a stable charge capacity of 452 mA h g-1 after 380 cycles at 1.5 A g-1.27 The amorphous GeOx coated reduced graphene oxide balls showed a high capacity of 795 mA h g-1 at 2 A g-1.28

A vertically aligned

graphene@amorphous GeOx nanoflakes maintained a reversible capacity of 1008 mA h g−1 and an excellent rate performance.29 Our previous work also revealed that a GeO2/reduced graphene oxide composite on Ni foam substrate could exhibit a large capacity of 1159 mA h g-1 even after 500 cycles.30 Although modest strides have been achieved, Ge-based anode materials with a long cycle life as well as a large capacity are still quite limited and urgently demanded.31-35 Ordered mesoporous carbon (OMC) has attracted remarkable attention, not only owing to its intrinsic characters (such as uniform pore diameter, large pore volume and high conductivity), but also function as a promising nano-reactor for fabricating nanomaterials in recent years.36-38 OMC has already been introduced into various nanostructures, including S, SnO2, MoS2, MnOx, TiO2, LiFePO4 and ZnV2O4.39-48 These composites exhibited enhanced specific capacity and better cycling performance. On the other hand, recent reports have corroborated that the nanosized Ge can catalyze the conversion reaction of GeO2 resulting in the enhanced cycling performance of GeO2 anode.16 To the best of our knowledge, however, the OMC-supported Ge/GeO2 structure, although highly demanded for energy storage, has not been reported. In the present work, Ge/GeO2-OMC nanocomposite was successfully fabricated via a facile nanocasting route by using mesoporous carbon as a nano-reactor, and was then used as an anode for LIBs. The fabrication process for Ge/GeO2-OMC nanocomposite is depicted in Scheme 1. The OMC with 2-dimentional ordered mesoporous channel was used as a template for synthesizing Ge/GeO2-OMC nanocomposite. The (NH4)2GeO3 precursor solution was obtained through a reaction of GeO2 and NH3·H2O aqueous solution.12 Different components of Ge/GeO2 were loaded with the carbon matrix of OMC by impregnation of (NH4)2GeO3 precursor solution,



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followed by calcination in 5% H2/95% Ar or Ar at 600 °C. The (NH4)2GeO3 precursor was decomposed to GeO2 firstly, and then partial GeO2 was further reduced to Ge by H2 and/or OMC. This material exhibited large reversible capacity, excellent long-time cycling stability and high rate performance.

Scheme 1 The schematic illustration of the preparation of Ge/GeO2-OMC nanocomposite. Experimental Sample preparation and characterization In current work, all chemical reagents were used without any purification. GeO2 powder and P123 (EO20PO70EO20) were purchased from Sigma-Aldrich, other chemical regents were supplied by Sinopharm Chemical Reagent Co. and were used without further purification. The synthesis route of SBA-15 silica was similar to the synthesis procedure described by Zhao.49 OMC was fabricated by using SBA-15 silica as the hard template and sucrose as the carbon source following the synthesis procedure reported by Ryoo.50,

51

For a typical synthesis of

Ge/GeO2-OMC nanocomposite, 0.2 g of OMC powder was firstly introduced in 10 mL of 5 M HNO3 solution under stirring for 1 h at 70 °C to make the powder more easily dispersible in


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ethanol. The 0.18 g of GeO2 was dispersed into the mixed solvent containing 5 mL of ethanol and 5 mL of distilled water. After drop-wise adding concentrated NH4OH solution (5 mL) into the above mixture, a transparent solution was quickly formed. Then 0.2 g of OMC powder was dispersed in the mixture solution by ultrasonication for 0.5 h, and finally the obtained solution was vigorously stirred 8 h at room temperature. The mixture was then dried at 75 °C for 2 h and calcined under 5% H2/95% Ar at 600 °C for 4 h.

As a reference sample, Ge/GeO2-OMC-2

nanocomposite was synthesized in the same way as Ge/GeO2-OMC nanocomposite, except for calcining at 600 oC in Ar. As another reference, bulk Ge/GeO2 was also synthesized except for calcining at 600 °C in 5% H2/95% Ar without OMC template. The structure of the products was evaluated by powder X-ray diffraction (XRD) recorded on a PANalytical X’ Pert diffractometer equipped with Co Kα radiation (λ = 1.789 Å) in the range of 10-70o, and the data would be changed to Cu Kα data. The morphology of the products was analyzed using scanning electron microscopy (SEM, Hitachi 4800).

Transmission electron

microscopy (TEM) images and high-resolution transmission electron microscopy (HRTEM) images were taken on FEI F20 S-TWIN at an acceleration voltage of 200 kV.

Nitrogen

adsorption-desorption isotherms were measured at 77 K on a nitrogen sorption apparatus (Micromeritics ASAP2020), the corresponding surface areas were determined using the Brunauer–Emmet–Teller (BET) method from the relative pressure range from 0.06 to 0.3. The carbon content of sample was evaluated by using Vario EL-Cube (Elementar, Germany).

Electrochemical measurements Electrochemical tests were performed using coin-type cells assembled in an argon-filled glove box.

The work electrodes were composed of 75 wt% active materials (Ge/GeO2-OMC

nanocomposite), 15 wt% acetylene black and 10 wt% polyvinylidene difluoride (PVDF). The



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electrode slurry was cast onto a Cu foil as the working electrode and dried at 110 °C for 12 h in vacuum. LiPF6 (1 M) in a mixture of EC, EMC and DMC with a weight ratio of 1:1:1 was used as the electrolyte, and the metallic lithium foil served as the counter and reference electrodes. The UP 3093 (Japan) microporous polypropylene membrane was used as separator. The specific capacity values of Ge/GeO2-OMC nanocomposite are calculated on the basis of the total mass of Ge/GeO2 and OMC. The electrochemical properties of Ge/GeO2-OMC-2 nanocomposite, bulk Ge/GeO2 and OMC were also tested under the same conditions. The coin cells (2025-type) were assembled in an argon-filled glove box with the quantity of oxygen and moisture below 1 ppm. Galvanostatic charge-discharge curves and cycling performance were measured with a Land CT 2001A electrochemical workstation at current densities of 100-2000 mA g-1 and voltage range from 0.01 to 3.0 V (vs. Li+/Li) at room temperature.

Cyclic voltammograms (CV) and

electrochemical impedance spectroscopy (EIS) were recorded on Zahner electrochemical workstation (IM6, Zahner Elektrik Co., Germany). CV was measured at a scanning rate of 1 mV s-1 in the voltage range of 0.01-3.0 V. For EIS measurement, the AC modulation amplitude is 10 mV and the frequency range is 5 MHz - 50 mHz.

Results and discussion The XRD patterns of Ge/GeO2-OMC nanocomposite and OMC are shown in Fig. 1. As seen from Fig. 1a, the peaks at 27.3º, 45.3º, 53.7º and 66.1º can be attributed to (1 1 1), (2 2 0), (3 1 1) and (4 0 0) planes of cubic phase Ge (JCPDS 089-2768), respectively, and the other peaks can be assigned to the hexagonal phase GeO2 (JCPDS 036-1463). It can also be found that the XRD patterns of OMC were only two broaden diffraction peaks at 2θ of 27º and 51º, suggesting the amorphous characterization of OMC.52

As depicted in Fig. S1, two reference samples

(Ge/GeO2-OMC-2 nanocomposite and bulk Ge/GeO2) are also composed of cubic phase Ge


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(JCPDS 089-2768) and hexagonal phase GeO2 (JCPDS 036-1463). The (NH4)2GeO3 precursor was decomposed to GeO2 firstly and then partial GeO2 was further reduced to Ge by H2 and/or OMC. It can be found that the Ge/GeO2-OMC-2 nanocomposite has less amount of Ge than Ge/GeO2-OMC nanocomposite. Ge GeO2

Intensity (a.u.)

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a b

10

20

30

40

50

60

70

2Theta (degree)

Fig. 1 XRD patterns of (a) Ge/GeO2-OMC nanocomposite and (b) OMC. The morphologies and microstructures of the OMC and Ge/GeO2-OMC nanocomposite were characterized by SEM and TEM measurements.

Fig. 2a shows SEM image of the OMC

composed of micrometer-sized rod with a diameter of ca. 400 nm. The microstructures of two samples are further characterized by TEM measurement and the results are shown in Fig. 2b-d. As shown in Fig. 2b, the well-ordered hexagonal arrays of cylindrical wall arrangement was observed, illustrating that OMC possessed the well-ordered mesoporous channels. Fig. 2c-d depicts TEM images of the Ge/GeO2-OMC nanocomposite. It can be found that the Ge/GeO2OMC nanocomposite retained the same mesostructure as the ordered mesoporous carbon matrix. The mesoporous channels of carbon matrix were stained with the Ge/GeO2 nanoparticles as vividly discernible by dark images along the matrix. The Ge/GeO2 nanoparticles were highly 7 Environment ACS Paragon Plus


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dispersed and distributed in the mesoporous carbon channels, indicating that the ultra small Ge/GeO2 nanoparticles can be achieved through a facile nanocasting route. As depicted in Fig. 2d, the size of Ge/GeO2 nanoparticles in the Ge/GeO2-OMC nanocomposite ranged from 4 to 10 nm. The HRTEM image further confirmed the presence of nano-sized Ge and GeO2, as depicted in the inset of Figure 2d. The lattice fringes with d-spacing of 0.199 and 0.343 nm are the characteristics of (220) lattice planes for Ge and (101) lattice planes for GeO2, respectively.

a

1 µm

b

50 nm

d

c GeO2 0.343nm （ 101））

Ge 200 nm

100 nm

0.199nm （ 220））

Fig. 2 SEM and TEM images of (a, b) OMC and (c, d) Ge/GeO2-OMC nanocomposite. The inset is HR-TEM image of Ge/GeO2-OMC nanocomposite. The porous features of samples were measured by nitrogen adsorption-desorption isotherm. Fig. 3 presents that nitrogen adsorption-desorption isotherms and the corresponding Barrett– 8 Environment ACS Paragon Plus

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Joyner–Halenda (BJH) pore-size-distribution plots (inset of Fig. 3) of the OMC and Ge/GeO2OMC nanocomposite. The isotherms of both samples exhibited type IV characteristics, which is typical of mesoporous materials.53, 54 The surface area and pore volume were estimated by the BET method to be 1159 m2 g−1 and 1.3 cm3 g−1 for OMC and 343 m2 g−1 and 0.35 cm3 g−1 for Ge/GeO2-OMC nanocomposite, respectively.

The BET surface area and pore volume of

Ge/GeO2-OMC nanocomposite decreased significantly inferred that ultra small Ge/GeO2 nanopaticles were successfully incorporated into the porous of OMC matrix. From the pore size distribution, OMC was 4.1 nm, while Ge/GeO2-OMC nanocomposite was decreased to 3.2 nm (inset of Fig. 3). The decrease of pore size for the latter was probably due to the filling of Ge/GeO2 nanopaticles into the interspace between carbon matrix channels.43,47 According to the result of elemental analysis, the carbon content of Ge/GeO2-OMC nanocomposite was found to be ca. 58 wt%.

Fig. 3 (a) N2 adsorption-desorption isotherms and (b) BJH pore size distribution plots for OMC and Ge/GeO2-OMC nanocomposite. The electrochemical behaviors of Ge/GeO2-OMC nanocomposite electrode was measured by CV measurement for initial 15 cycles at a scanning rate of 1 mV s−1 between 0.01 and 3.0 V and



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the results are given in Fig. 4. During the first sweep, there was one weak reduction peak located at 1.1 V and remained in the following cathodic cycles, which could be possibly related to the formation of amorphous LixGeOx.26 With a further decrease in electrode potential, the reduction peaks near 0.5 and 0.2 V were assigned to the lithiation of LixGeOx and formation of LixGe alloy.26 In the anodic scan, the oxidation peak appearing at 0.6 V was due to the delithiation process of LixGe alloy.33 The oxidation peak at about 1.3 V has been confirmed that Ge was reoxidated to GeO2,16 leading to partly reversible in the conversion reaction of GeO2 (equation (1)) and finally resulting in a high specific capacity of Ge/GeO2-OMC nanocomposite even at a low germanium content. The following CV curves remained coincident, which was in agreement with the charge-discharge curve properties.

The electrochemical reaction mechanism of

Ge/GeO2-OMC nanocomposite electrode can be expressed as the following equations (1) and (2): GeO2 + 4Li+ + 4e- →Ge + 2Li2O

(1)

Ge + 4.4Li+ + 4.4e- ↔ Li4.4Ge

(2)

Fig. 4 Cyclic voltammograms curves of Ge/GeO2-OMC nanocomposite at a scan rate of 1 mV s1

.


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Fig. 5 (a) The cycling performance of Ge/GeO2-OMC nanocomposite, OMC, Ge/GeO2-OMC nanocomposite and bulk Ge/GeO2 at a current density of 100 mA g-1 between 0.01-3.0 V. Open and filled symbols denote for charge and discharge capacities, respectively. (b) The charge and discharge profiles of Ge/GeO2-OMC nanocomposite at a current density of 100 mA g-1 between 0.01-3.0 V. Fig. 5a depicts the cycling performance of the Ge/GeO2-OMC nanocomposite and OMC at 100 mA g-1 within a potential range of 0.01-3 V. The capacity of Ge/GeO2-OMC nanocomposite was calculated on the total mass of Ge/GeO2 and OMC. It can be found that the former exhibited better cycling stability than that of the latter. A discharge capacity of OMC was merely 429 mA h g-1 after 50 cycles, while Ge/GeO2-OMC nanocomposite showed a capacity of 961 mAh g-1. Even after 100 cycles, the latter can still maintain 1018 mA h g-1. However, a discharge capacity of 393 mA h g-1 was obtained for OMC electrode after 100 cycles.

Obviously, the

electrochemical performance of the Ge/GeO2-OMC nanocomposite is better than that of the OMC under the same conditions. In order to understand well the electrochemical performance of the Ge/GeO2-OMC nanocomposite, especially to investigate the catalytic role of Ge and



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contribution of mesoporous carbon matrix to the enhanced lithium-ion storage performance, bulk Ge/GeO2 and Ge/GeO2-OMC-2 nanocomposite with little amount of Ge were obtained and their electrochemical performances were also measured (Fig. 5a).

The cycling performance of

Ge/GeO2-OMC-2 nanocomposite and bulk Ge/GeO2 were also measured at 100 mA g-1 between 0.01-3.0 V. For comparison, the Ge/GeO2-OMC-2 nanocomposite and bulk Ge/GeO2 were evaluated under the same conditions. The discharge capacities of Ge/GeO2-OMC-2 and bulk Ge/GeO2 electrode were 576 and 224 mA h g-1 after 100 cycles, respectively. Obviously, the electrochemical performances of the Ge/GeO2-OMC nanocomposite are better than that of the Ge/GeO2-OMC-2 nanocomposite, OMC and bulk Ge/GeO2 under the same conditions, indicating that the Ge/GeO2-OMC nanocomposite with suitable amount of Ge nanocrystal and carbon matrix is beneficial to improve the specific capacity retention and cycling performance of the Ge/GeO2 anode. Fig. 5b displays the charge-discharge potential profiles of Ge/GeO2-OMC nanocomposite at a current density of 100 mA g-1 in a voltage range of 0.01-3.0 V. All voltage platforms were consistent with the CV peaks. The initial discharge specific capacity was 1770 mA h g-1 and the charge capacity was 1191 mA h g-1 for the Ge/GeO2-OMC nanocomposite, corresponding to a Coulombic efficiency of 67.3%, which was prior to those of Ge-based materials in previous reports.25, 27, 29, 35 The initial irreversible capacity loss may be mainly attributed to irreversible processes such as inevitable formation of SEI layer and Li2O by the irreversible reaction.33 Despite the initial irreversible capacity loss, it appeared from the excellent cycle stability of the Ge/GeO2-OMC nanocomposite that most of the Ge/GeO2 composite reversibly reacted with Li+ and that the abrupt capacity degradation caused by the detachment of active materials was significantly suppressed. The 5th and 100th discharge profiles were almost coincided with each other, indicating the excellent cycling stability of Ge/GeO2-OMC nanocomposite.55 Fig. S2


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shows CV curves of Ge/GeO2-OMC-2 nanocomposite and bulk Ge/GeO2 at a scan rate of 1 mV s-1. Fig.S3 shows the charge and discharge profiles of Ge/GeO2-OMC-2 nanocomposite and bulk Ge/GeO2 at a current density of 100 mA g-1 between 0.01-3.0 V.

Fig. 6 The cycling performance of Ge/GeO2-OMC nanocomposite at different current densities. Open and filled symbols denote for charge and discharge capacities, respectively. The rate capability of Ge/GeO2-OMC nanocomposite was investigated by applying different current densities from 100 to 2000 mA g-1 (Fig. 6). Generally, higher current densities lead to lower specific capacities. As shown in Fig. 6, the Ge/GeO2-OMC nanocomposite exhibited a stable cycling performance at different current densities. After 100 cycles, the Ge/GeO2-OMC nanocomposite electrode delivered reversible capacities of 1018, 824, 685, 531 and 395 mA h g-1 at current densities of 100, 200, 500, 1000 and 2000 mA g-1, respectively.

This result

demonstrated that this material exhibited a high reversible capacity and can endure high-rate cycling without structural damage.56-59



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Fig. 7 The Coulombic efficiency and cycling performance of Ge/GeO2-OMC nanocomposite at the specific current of 1000 mA g-1. To investigate the long-time cycling stability at high rates, we increased the charge-discharge current density to 1000 mA g-1. Fig. 7 shows the long-time cycling performance and Coulombic efficiency of Ge/GeO2-OMC nanocomposite at a high current density of 1000 mA g-1 in a potential range of 0.01-3 V. It can be found that the electrode retained a large capacity of 531 mA h g-1 at a high current density of 1000 mA g-1 after 100 cycles. Importantly, the Coulombic efficiency became stable and was over 98% after the third cycle. Even after 500 cycles, the Ge/GeO2-OMC nanocomposite electrode still retained the capacity of 492 mA h g-1 and maintained as high as 92.7% of its reversible capacity between 100 and 500 cycles (~0.018% per cycle), indicating an excellent cycling stability. Additionally, an average specific discharge capacity in 500 cycles at 1000 mA g-1 was found to be about 517 mA h g-1. The high specific capacity and long-time cycling stability for Ge/GeO2-OMC nanocomposite demonstrated that this material is a good candidate for high performance of rechargeable LIBs.


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Fig. 8 (a) Nyquist plots and (b) the relationship between Zre and ω-1/2 for the Ge/GeO2-OMC nanocomposite and bulk Ge/GeO2 electrode after 50 cycles from 5 MHz to 0.05 Hz in the fully charged state. Fig. 8a shows the Nyquist profiles of Ge/GeO2-OMC nanocomposite and bulk Ge/GeO2 electrodes after 50 cycles from 5 MHz to 0.05 Hz in the fully charged state. It can be seen that two plots are composed of one semicircle at high frequencies and a short inclined line in the low frequency regions. The semicircle in high frequencies is related to the contact resistance and charge transfer resistance. In the low frequency regions, the short inclined line of the relationship between Zre and ω-1/2 is related to the ion diffusion within the anode material. Obviously, the semicircle for Ge/GeO2-OMC nanocomposite was much smaller than that of bulk Ge/GeO2, suggesting that the former has lower contact and charge transfer resistances. As shown in Fig. 8b, the Ge/GeO2-OMC nanocomposite exhibited lower slope than bulk Ge/GeO2, indicating the facile ion transportation of Ge/GeO2-OMC nanocomposite electrode. Based on the above analysis of the results, the high electrochemical performance of Ge/GeO2OMC nanocomposite in terms of large reversible capacities, excellent long-time cycling stability and high rate capability is probably attributed to the buffering effect of mesoporous carbon



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matrix, the small size of Ge/GeO2 nanoparticles, high conductivity of mesoporous carbon and catalytic effect of Ge nanoparticles. In detail, the interconnected mesoporous structure of OMC not only acts as a protective matrix for accommodating the volume expansion of Ge/GeO2 nanoparticles and prevents the aggregation of Ge/GeO2 nanoparticles during the cycling process, but also facilitates the electronic conductivity and ion transportation. Meanwhile, the partial reversible conversion reaction of GeO2 was catalyzed by Ge nanoparticles, resulting in a large specific capacity.16

All of these aspects contribute to the large reversible capacities, excellent

long-time cycling stability and high rate capability of the Ge/GeO2-OMC nanocomposite.

Conclusions In summary, we have successfully fabricated the Ge/GeO2-OMC nanocomposite via a simple nanocasting route by using ordered mesoporous carbon as a nano-reactor. It was found that ultra small Ge/GeO2 nanoparticles in the nanocomposite were distributed within the mesoporous carbon matrix. Fundamentally, the ultra small Ge/GeO2 nanoparticles were the main active materials offering a large reversible capacity. In the nanocomposite, the OMC component could not only act as a protective matrix for accommodating the volume change of Ge/GeO2 nanoparticles, but also facilitate the electronic conductivity and ion transportation. When used as an anode for LIBs, the Ge/GeO2-OMC nanocomposite exhibited large reversible capacity of 1018 mAh g-1 at 0.1 A g-1 after 100 cycles, high rate capability and excellent long-time cycling stability (500 cycles).

Therefore, such a novel Ge/GeO2-OMC nanocomposite is a good

candidate for energy storage and other critical devices.

AUTHOR INFORMATION Corresponding Author


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*E-mail: [email protected]; Tel/Fax: 86 591 83753180; [email protected]; Tel/Fax: 86 591 83465156; ACKNOWLEDGMENT This work was financially supported by National Natural Science Foundation of China (NSFC 21173049 and 51502036), Educational Commission of Fujian Province (JA15115) and Fujian Province Economic and Trade Commission Fund (2013720). ASSOCIATED CONTENT Supporting Information Available: XRD patterns, CV curves and charge and discharge profiles of Ge/GeO2-OMC nanocomposite, Ge/GeO2-OMC-2 nanocomposite and bulk Ge/GeO2. This material is available free of charge via the Internet at http://pubs.acs.org.

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GeO2-Ordered Mesoporous Carbon Nanocomposite for

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