A Facile Synthetic Approach to Reduced Graphene Oxide-Fe<sub>3</sub>O<sub>4</sub> Composite as High Performance Anode for Lithium-ion Batteries

Cite this Article

Yanhong Chang, Jing Li, Bin Wang, Hui Luo, Linjie Zhi. A Facile Synthetic Approach to Reduced Graphene Oxide-Fe₃O₄ Composite as High Performance Anode for Lithium-ion Batteries . Journal of Materials Science & Technology, 2014, 30(8): 759-764 Copy to clipboard

Permissions

A Facile Synthetic Approach to Reduced Graphene Oxide-Fe₃O₄ Composite as High Performance Anode for Lithium-ion Batteries

Yanhong Chang^1,^2,^*, Jing Li^1,³, Bin Wang³, Hui Luo⁴, Linjie Zhi^3,^**

1 School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China

2 Key Laboratory of Educational Ministry for High Efficient Mining and Safety in Metal Mine,University of Science and Technology Beijing, Beijing 100083, China

3 National Center for Nanoscience and Technology, Beijing 100190, China

4 School of Chemical and Biological Engineering, University of Science and Technology Beijing,Beijing 100083, China

* Corresponding author. Assoc. Prof., Ph.D.; Tel.: t86 1062333292; Fax: t86 10 82385795; E-mail address:yhchang@ustb.edu.cn (Y. Chang); ** Corresponding author. Prof., Ph.D.; Tel.: t86 10 82545594; Fax: t8610 82545574; E-mail address:zhilj@nanoctr.cn (L. Zhi).

Abstract

O₄ (rGO-Fe₃O₄) composite has been prepared via a facile and effective hydrothermal method by synthesizing Fe₃O₄ nanospheres on the planes of reduced graphene oxide (rGO). Characterizations suggest the successful attachment of Fe₃O₄ nanospheres to rGO sheets. The rGO-Fe₃O₄ composite (66.7 wt% of Fe₃O₄ in the composite) exhibits a stable capacity of 668 mAh g^-1 without noticeable fading for up to 200 cycles in the voltage range of 0.001-3.0 V, and the superior performance of rGO-Fe₃O₄ is clearly established by comparison of the results with those from bare Fe₃O₄ nanospheres (capacity declined to 117 mAh g^-1 only at the 200th cycle). The excellent electrochemical performance of rGO-Fe₃O₄ composite can be attributed to the fact that the uniform dispersion of the Fe₃O₄ nanospheres growing on the rGO sheets avoids aggregation during Li uptake-release cycling, which is desired for cycle stability. Meanwhile, the rGO sheets afford not only elastic buffer to alleviate the volume variations of Fe₃O₄ nanospheres, but also good ionic and electronic transport medium in the electrode.

Keyword: Facile synthetic approach; rGO; Fe₃O₄ nanospheres; Composite; Lithium-ion batteries; High performance

Show Figures

1. Introduction

Developing devices and related materials for producing and storing electricity are key issues to meet the increasing energy demand. Rechargeable lithium-ion batteries (LIBs) are currently being explored for high-power energy applications in a wide range of both civil and military, such as electronic devices, electric vehicles and implantable medical devices^{[ 1], [ 2], [ 3]}. Their energy density and power density mainly depend on the physical and chemical properties of both cathode and anode materials. Graphite is widely commercial anode material for LIBs, however, the theoretical specific capacity of graphite is only 372 mAh g^-1. Resulting from the growing demand for high energy and power density, the attention has been shifted from graphitic anodes to electrochemically active metals and transition metal oxides, such as Si^{[ 4]}, Sn^{[ 5]}, Co₃O₄^{[ 6]}, Fe₂O₃^{[ 7]}, and Fe₃O₄^{[ 6]}, due to their high theoretical capacities and promising potential. Among them, Fe₃O₄ has been considered as one of the most prominent candidates for next generation LIBs anode materials for its higher specific capacity, eco-benignity and natural abundance^{[ 8], [ 9], [ 10]}. Nevertheless, the Fe₃O₄ anode materials have poor cycle performance during the continuous charge/discharge cycling because of the severe aggregation and drastic volume change of Fe₃O₄ particles^{[ 8], [ 9], [ 10], [ 11]}, which reduces the surface area of active materials and leads to the breakdown of electrical connection between anode materials and current collectors, respectively. To alleviate these problems, nanostructured oxide/carbon hybrids, such as carbon nanotube composites^{[ 11], [ 12]}, carbon coated nanospindles^{[ 8]}/nanorods^{[ 13]}/nanocapsules^{[ 14]} are being thought to conquer the challenge with good cyclic performance as well as to maintain high specific capacity. Among these approaches, carbon coating has been proved to effectively improve the cyclic performance, which serves as a buffer to relieve the volume change and preserve the electrode integrity^{[ 9], [ 15], [ 16]}.

Graphene, a single layer of sp²-bonded carbon atoms patterned in a hexagonal lattice, exhibits prominent thermal stability^{[ 17]}, superior electronic conductivity^{[ 18]}, remarkable structural flexibility^{[ 19]}, and high specific surface area^{[ 20]}. These unique properties of graphene make it become an ideal material for many applications, including microelectronics, batteries, supercapacitors, sensors and mechanical resonators^{[ 21], [ 22], [ 23], [ 24], [ 25]}. In LIBs, graphene-based composites have emerged as quite intriguing electrode materials^{[ 26], [ 27], [ 28], [ 29], [ 30]}. Recently, the Fe₃O₄ particles combined with graphene have been reported and display several advantages^{[ 31], [ 32], [ 33], [ 34]}. Firstly, ultrathin graphene sheets can prevent the aggregation of Fe₃O₄ particles^{[ 35], [ 36]}. Secondly, the graphene can provide void space against the volume changes of the Fe₃O₄ particles during lithium-ion insertion/extraction process^{[ 37]}, which can improve the cycling performance. Finally, the Fe₃O₄ particles are anchored on the planes of graphene, which may lead to a high rate performance due to the high electronic conductivity of graphene sheets and short path length for Li⁺ transport of Fe₃O₄ particles^{[ 38]}. However, the reported strategies for preparing graphene-Fe₃O₄ composite are complicated, involving additional reduction agents such as N₂H₄^{[ 39]}, NaBH₄^{[ 40]} and additional annealing steps^{[ 31]}.

Herein, we reported a facile one-pot hydrothermal route to prepare rGO-Fe₃O₄ composite combining Fe₃O₄ nanospheres with rGO sheets, directly from graphene oxide (GO) and iron chloride (FeCl₃·6H₂O) in the presence of ethylene glycol. The illustration of the synthesis process is shown in Scheme 1. Through this rapid and robust in situ approach, the reduction of GO and the deposition of Fe₃O₄ nanospheres on rGO sheets occurred simultaneously under alkaline condition by hydrolyzing of potassium acetate (KAc), and ethylene glycol (EG) served as both solvent and reducing agent. The resultant hybrid rGO-Fe₃O₄ composite materials were obtained by hydrothermal method without additional reducing agent or further annealing step. Characterizations showed that the Fe₃O₄ nanospheres were uniformly distributed on the rGO sheets. The electrochemical performance of rGO-Fe₃O₄ composite as anode electrode material for LIBs was investigated and compared with bare Fe₃O₄. The experimental results indicated that the rGO-Fe₃O₄ composite could indeed deliver a high reversible specific capacity together with excellent cycle performance.

Scheme 1.Synthesis process of rGO-Fe₃O₄ composite.

2. Experimental

2.1. Materials

Graphite powder was obtained from Tianjin Chemicals Company (China). Other reagents were purchased from Beijing Chemicals Company (China), all chemicals used in our experiments were reagent grade without further purification.

2.2. Characterization and apparatus

The morphology and structure of the samples were characterized by transmission electron microscopy (TEM, Tecnai G2 F20 U-TWIN), scanning electron microscopy (SEM, Hitachi S4800), polycrystalline X-ray diffraction (XRD, Rigaku-D/max 2005B²+/PCX), and X-ray photoelectron spectroscopy (XPS, PH1500C) under room temperature. Fourier transform infrared spectra (FTIR) were recorded on a Spectrum One FTIR spectrometer from 4000 to 400 cm^-1. The thermal properties of the samples were recorded by a thermogravimeter (TGA/DSC, Netzsch-STA 449C) measured from room temperature to 1000 °C at a heating rate of 10 °C/min in air.

2.3. Preparation of rGO-Fe₃O₄ composite

GO was synthesized from natural graphite powder by a modified Hummers method^{[ 41]}. Then, aqueous suspension of GO at a concentration of 5 mg ml^-1 was prepared. In a typical procedure^{[ 32]}, 50 ml of ethylene glycol was dropped into 10 ml GO suspension by dropper and the mixture was sonicated for 1 h, then 0.2 g of FeCl₃·6H₂O was homogeneously dissolved in the obtained light brown dispersion. Subsequently, 4.3 g of potassium acetate (KAc) and 1.0 g of polyethylene glycol were poured in the mixed solution, followed by stirring constantly for 1 h, and then the mixture was sealed in a Teflon-lined stainless steel autoclave at 200 °C for 16 h. After hydrothermal treatment, the autoclave was naturally cooled to room temperature, and the rGO-Fe₃O₄ composite was then obtained after centrifugation and washing with ethanol. The as-obtained sample was dried at 50 °C in a vacuum oven for 12 h. To prepare rGO and bare Fe₃O₄ nanospheres for comparison, the synthesis was carried out in the absence of FeCl₃·6H₂O or GO under the same other conditions as the preparation rGO-Fe₃O₄, respectively.

2.4. Electrode preparation and electrochemical characterization

The electrochemical properties of the prepared rGO-Fe₃O₄ composite and bare Fe₃O₄ nanospheres as anode materials for LIBs were evaluated by galvanostatic charge-discharge technique at 25 °C. The test electrodes were prepared by mixing active material (80 wt%) with acetylene black (10 wt%) as a conductive agent and polyvinylidenedifluoride (10 wt%) dissolved in N-methyl-2-pyrrolidone (NMP) as a binder to form a slurry. The slurry was then coated onto a copper foil with 14 mm diameter. These electrodes were then pressed and dried under vacuum at 100 °C for 12 h. CR2032 coin-type cells were ultimately assembled in an argon-filled glovebox. The prepared rGO-Fe₃O₄ composite or bare Fe₃O₄ nanospheres was used as test electrode, metallic lithium as the counter/reference electrode, 1 mol/l LiPF₆ dissolved in a mixture of ethylene carbonate (EC), diethyl carbonate (DEC) (1:1 by volume) as the electrolyte, and polypropylene film as a separator. The charge/discharge measurements were carried out by using the land battery program-control test system (CT2001A) at a constant current density of 100 mA g^-1 over a voltage range of 0.001-3.0 V vs Li/Li⁺.

3. Results and Discussion

Fig. 1(a) shows the typical SEM image of rGO-Fe₃O₄ composite, which exhibits that the Fe₃O₄ nanospheres with a few aggregations are dispersed on the basal planes of rGO sheets. This appropriate connection between Fe₃O₄ and rGO enhances electrode stability against cycling processes for lithium storage. In a magnified SEM image of composite (Fig. 1(b)), both the fringe of rGO sheets and the morphology of Fe₃O₄ nanospheres can be observed, and the diameter of most of the nanospheres is slightly different ranging from 100 to 200 nm. The TEM images (Fig. 1(c and d)) of the composite reveal morphology features which are in agreement with the SEM result. From the TEM image at a higher magnification (Fig. 1(d)), it clearly shows the lattice fringes of Fe₃O₄ with a spacing of 0.48 nm, which agrees well with the d-spacing of the (111) plane of Fe₃O₄.

	Figure Option View Download New Window
	Fig. 1. (a) SEM image of rGO-Fe₃O₄ composite, (b) high magnification SEM image of rGO-Fe₃O₄ composite, (c) TEM image of rGO-Fe₃O₄ composite, (d) high magnification TEM image of rGO-Fe₃O₄ composite.

Typical XRD patterns of the natural graphite, as-prepared rGO-Fe₃O₄ composite, rGO, and Fe₃O₄ nanospheres are presented in Fig. 2. As displayed in Fig. 2(a), the original graphite shows the sharp characteristic (002) diffraction peak at around 2 θ = 26.5°. After oxidation treatment ( Fig. 2(b)), the rGO-Fe₃O₄ composite and rGO possess the weaker, broader diffraction peak of (002) than pristine graphite because of the introduction of oxygen-containing functional groups on the graphite sheets. These results suggest that more disordered stacking rGO sheets are presented in the rGO-Fe₃O₄ composite^{[ 16]}. All of the other diffraction peaks can be indexed as the face-centered cubic structured Fe₃O₄ nanospheres that coincide well with the standard data of Fe₃O₄ (JCPDS card 19-0629), which indicates that the rGO-Fe₃O₄ composite consists of disorderedly stacked rGO sheets and well crystallized Fe₃O₄.

	Figure Option View Download New Window
	Fig. 2. XRD patterns of: (a) natural graphite, (b) rGO, Fe₃O₄ nanospheres, and rGO-Fe₃O₄ composite.

To determine the chemical composition of rGO-Fe₃O₄ composite, XPS measurement was carried out (Fig. 3(a)). The broad peaks around 710.9 and 724.5 eV are typical for the Fe2 p, corresponding to the Fe2 p_3/2 and Fe2 p_1/2 spin orbit peaks of Fe₃O₄, respectively (as shown in the inset of Fig. 3(a)), implying the formation of a mixed oxide of Fe(II) and Fe(III). In Fig. 3(b), the C1 s XPS spectrum of GO contains three components: the non-oxygenated ring C-C (284.8 eV), C-O species (286.3 eV) and C=O species (288.7 eV)^{[ 26]}. After the hydrothermal reduction ( Fig. 3(c)), the intensity of oxygenated peaks is significantly less than that of non-oxygenated peaks, and the remarkable decrease of oxygenated functional groups indicates the deoxygenation of GO during the reaction process. FTIR spectra of rGO and rGO-Fe₃O₄ composite are shown in Fig. 3(d). For rGO, the broad and intense band at 3446 cm^-1 and the peak at near 1580 cm^-1 are possibly attributed to the vibrations of O-H and C=C groups on the rGO sheets. Peaks located at 1069 and 1228 cm^-1 are most often related to stretching vibrations of C-O groups. For rGO-Fe₃O₄ composite, the band at 581 cm^-1 was the characteristic stretching vibrations of Fe-O^{[ 39]}. The FTIR results further testified the reduction reaction in the hydrothermal process, and the FTIR spectrum of the rGO-Fe₃O₄ composite became a combination of the absorption bands of rGO and Fe₃O₄ after mixing the two components.

	Figure Option View Download New Window
	Fig. 3. (a) XPS spectra of rGO-Fe₃O₄ composite, the inset is the high-resolution spectra of Fe2 p, (b) C1 s XPS spectra of GO, (c) C1 s XPS spectra of rGO-Fe₃O₄ composite, (d) FTIR spectra of rGO and rGO-Fe₃O₄ composite.

For quantifying the amount of rGO and Fe₃O₄ in the rGO-Fe₃O₄ composite, TGA was carried out in air from room temperature to 1000 °C at a rate of 10 °C/min. As can be seen from Fig. 4, there are three weight loss processes. A slight weight loss below 140 °C is attributed to the evaporation of the adsorbed moisture or gas molecules. Then the rGO-Fe₃O₄ composite experiences abrupt weight loss between 140 and 400 °C, which can be assigned to the destruction of labile oxygen-containing functional groups. The TGA/DSC curves of rGO-Fe₃O₄ composite present a characteristic step/peak in the range from 400 to 800 °C. Correspondingly, the DSC curve shows a strong exothermal peak centered at 440 °C. It can be assigned to the decomposition of rGO nanosheets^{[ 36]}. When the temperature reaches 800 °C, the weight of the sample remains and almost no weight loss occurs after this temperature. Therefore, the mass retained directly translates into the amount of Fe₃O₄ in the composite. By using this method, it was estimated that the amount of Fe₃O₄ in rGO-Fe₃O₄ composite was about 66.7 wt%.

	Figure Option View Download New Window
	Fig. 4. TGA and DSC curves of rGO-Fe₃O₄ composite in air atmosphere.

The electrochemical performance of rGO-Fe₃O₄ composite as anode was examined through galvanostatic charge/discharge cycling at 100 mA g^-1, for comparison, anodic property of bare Fe₃O₄ nanospheres was also tested under the same conditions (Fig. 5(a and b)). In the first discharge step, both rGO-Fe₃O₄ and bare Fe₃O₄ present an extended/long voltage plateau at about 0.70 V, followed by a sloping curve down to the cutoff voltage of 0.001 V, indicating a typical character for transition metal oxide anodes^{[ 30]}. It can be seen that the first discharge and charge capacities are 992.9 and 642 mAh g^-1 for rGO-Fe₃O₄ composite (the Coulombic efficiency is 65%), 655.6 and 362.6 mAh g^-1 for bare Fe₃O₄ (the Coulombic efficiency is 55%), respectively. Compared with the bare Fe₃O₄, the extra capacity of the rGO-Fe₃O₄ composite may be ascribed to the larger electrochemical active surface area of rGO sheets and grain boundary area of the Fe₃O₄ nanospheres^{[ 16]}. Large irreversible capacity observed in the first cycle may be caused by the formation of solid electrolyte interphase (SEI) and the reaction of the lithium-ion with oxygen-containing functional groups remaining unreduced on the surface of rGO sheets^{[ 35]}.

	Figure Option View Download New Window
	Fig. 5. Charge/discharge profiles of: (a) Fe₃O₄, (b) rGO-Fe₃O₄ composite.

After ten charge/discharge cycles, the rGO-Fe₃O₄ electrode (Fig. 5(b)) presents much better electrochemical lithium storage performance than the bare Fe₃O₄ electrode. For rGO-Fe₃O₄ electrode, it exhibits a high reversible capacity of 580 mAh g^-1 after the 50th cycle. By contrast, the value of bare Fe₃O₄ nanospheres deteriorates significantly to merely 223.6 mAh g^-1 after 50 cycles. These results indicate that rGO-Fe₃O₄ composite is electrochemically stable which makes it a promising anode material for LIBs.

Fig. 6(a) shows the cycling behavior of rGO-Fe₃O₄ composite and bare Fe₃O₄ nanospheres at a current density of 100 mA g^-1 for 200 cycles. Obviously, the rGO-Fe₃O₄ composite exhibits a much better cycle performance than Fe₃O₄. Although the discharge capacity of bare Fe₃O₄ electrode is 655.6 mAh g^-1 in the first cycle, the capacity continuously decreases and reaches 117 mAh g^-1 after 200 cycles, which is only for 17.8% of the initial capacity, indicating poor capacity retention. rGO-Fe₃O₄ electrode, after being decorated with rGO sheets, reveals the improved cyclic performance. The capacity of the rGO-Fe₃O₄ is 630 mAh g^-1 after 200 cycles, 63.4% of the initial capacity (992.9 mAh g^-1), which is attributed to the efficient interaction between Fe₃O₄ nanospheres and the rGO sheets in the rGO-Fe₃O₄ composite where the Fe₃O₄ nanospheres work as spacer between them; and both sides of rGO sheets can adsorb lithium-ion, which leads to two layers of lithium for its insertion/desertion during charging and discharging^{[ 38]}.

	Figure Option View Download New Window
	Fig. 6. (a) Charge (solid) and discharge (hollow) capacity vs cycle number for rGO-Fe₃O₄ composite and Fe₃O₄, (b) rate performance of rGO-Fe₃O₄ composite.

The rate performance during the lithium-ion insertion/extraction processes is a key factor for successful practical application as anode electrodes. Herein, rate performance of rGO-Fe₃O₄ composite was evaluated by carrying out charge/discharge measurements under different current densities. As shown in Fig. 6(b), the discharge capacities are retained at 689 and 616 mAh g^-1 at the current of 50 and 100 mA g^-1, respectively. As the current density reaches 400 mA g^-1, the discharge capacity remains stable at approximately 536 mAh g^-1, which is still comparable to commercial graphite electrodes. The capacity at a higher current of 1000 mA g^-1, although fading, still can deliver 502 mAh g^-1. It is noted that, when the current is restored to 50 mA g^-1 after 40 cycles, the rGO-Fe₃O₄ still delivers 696 mAh g^-1. The high reversible capacity, improved cycle stability and rate performance can be attributed to the high electronic conductivity of rGO sheets as substrate in the composite. rGO sheets have Li storage capacities, provide excellent electrical contact during cycling, inhibit the volume expansion and prevent Fe₃O₄ nanospheres from agglomeration. Meanwhile, the Fe₃O₄ nanospheres are homogeneously distributed in the carbon matrix, which ensures that the formed Li₂O and Fe contact well without separation. All of these factors are advantageous for the kinetics toward Li insertion/extraction.

4. Conclusion

A facile and effective hydrothermal process has been developed to prepare rGO-Fe₃O₄ composite. The Fe₃O₄ nanospheres with a size of about 100-200 nm were assembled on rGO sheets uniformly, and were effectively prevented from aggregating by rGO sheets. As an anode electrode for LIBs, rGO-Fe₃O₄ composite exhibited higher specific capacity and better cycle stability than bare Fe₃O₄ electrodes. Further work to investigate the influence factors (for example, the 3D structure of graphene) on the electrochemical performance of the composite is still in progress in our group. This optimized rGO-Fe₃O₄ composite with enhanced performance will have a promising potential in the application of lithium-ion batteries.

Acknowledgements

This work was supported by the Fundamental Research Funds for the Central Universities (FRF-SD-12-007A), and the National Natural Science Foundation of China (No. 21276023).

The authors have declared that no competing interests exist.

作者声明: 无竞争性利益关系

Reference

View Option

1.	S. Arico, P. Bruce, B. Scrosati, J. M. Tarascon, W. Van Schalkwijk;Nat. Mater. , 4 (2005), pp. 366-377 [Cited within: 1] [JCR: 35.749]
2.	M. G. Kim, J. Cho;Adv. Funct. Mater. , 19 (2009), pp. 1497-1514 [Cited within: 1] [JCR: 9.765]
3.	P. G. Bruce, B. Scrosati, J. M. Tarascon;Angew. Chem. Int. Ed. , 47 (2008), pp. 2930-2946 [Cited within: 1]
4.	C. K. Chan, H. L. Peng, G. Liu, K. McIlwrath, X. F. Zhang, R. A. Huggins, Y. Cui;Nat. Nanotechnol. , 3 (2008), pp. 31-35 [Cited within: 1] [JCR: 31.17]
5.	G. Derrien, J. Hassoun, S. Panero, B. Scrosati;Adv. Mater. , 19 (2007), pp. 2336-2340 [Cited within: 1] [JCR: 14.829]
6.	P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, J. M. Tarascon;Nature, 407 (2000), pp. 496-499 [Cited within: 2] [JCR: 38.597]
7.	J. Li, H. M. Dahn, L. J. Krause, D. B. Le, J. R. Dahn;J. Electrochem. Soc. , 155 (2008), pp. A812-A816 [Cited within: 1] [JCR: 2.588]
8.	W. M. Zhang, X. L. Wu, J. S. Hu, Y. G. Guo, L. J. Wan;Adv. Funct. Mater. , 18 (2008), pp. 3941-3946 [Cited within: 3] [JCR: 9.765]
9.	T. Muraliganth, A. V. Murugan, A. Manthiram;Chem. Commun. (2009), pp. 7360-7362 [Cited within: 3] [JCR: 6.378]
10.	S. Q. Wang, J. Y. Zhang, C. H. Chen;J. Power Sources, 195 (2010), pp. 5379-5381 [Cited within: 2] [JCR: 4.675]
11.	Y. He, L. Huang, J. S. Cai, X. M. Zheng, S. G. Sun;Electrochim. Acta, 55 (2010), pp. 1140-1144 [Cited within: 2] [JCR: 3.777]
12.	C. M. Ban, Z. C. Wu, D. T. Gillaspie, L. Chen, Y. F. Yan, J. L. Blackburn, A. C. Dillon;Adv. Mater. , 22 (2010), pp. E145-E149 [Cited within: 1] [JCR: 14.829]
13.	H. Liu, G. X. Wang, J. Z. Wang, D. Wexler;Electrochem. Commun. , 10 (2008), pp. 1879-1882 [Cited within: 1] [JCR: 4.425]
14.	P. Wu, N. Du, H. Zhang, J. X. Yu, D. R. Yang;J. Phys. Chem. C, 115 (2011), pp. 3612-3620 [Cited within: 1] [JCR: 4.814]
15.	G. M. Zhou, D. W. Wang, F. Li, L. L. Zhang, N. Li, Z. S. Wu, L. Wen, G. Q. Lu, H. M. Cheng;Chem. Mater. , 22 (2010), pp. 5306-5313 [Cited within: 1] [JCR: 8.238]
16.	J. Z. Wang, C. Zhong, D. Wexler, N. H. Idris, Z. X. Wang, L. Q. Chen, H. K. Liu;Chem. Eur. J. , 17 (2011), pp. 661-667 [Cited within: 3] [JCR: 3.499]
17.	A. A. Baland in, S. Ghosh, W. Z. Bao, I. Calizo, D. Teweldebrhan, F. Miao, C. N. Lau;Nano Lett. , 8 (2008), pp. 902-907 [Cited within: 1] [JCR: 13.025]
18.	K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V. Grigorieva, S. V. Dubonos, A. A. Firsov;Nature, 438 (2005), pp. 197-200 [Cited within: 1] [JCR: 38.597]
19.	C. Lee, X. D. Wei, J. W. Kysar, J. Hone;Science, 321 (2008), pp. 385-388 [Cited within: 1]
20.	A. Peigney, C. Laurent, E. Flahaut, R. R. Bacsa;Carbon, 39 (2001), pp. 507-514 [Cited within: 1] [JCR: 5.868]
21.	A. K. Geim, K. S. Novoselov;Nat. Mater. , 6 (2007), pp. 183-191 [Cited within: 1] [JCR: 35.749]
22.	A. K. Geim;Science, 324 (2009), pp. 1530-1534 [Cited within: 1]
23.	E. Yoo, J. Kim, E. Hosono, H. Zhou, T. Kudo, I. Honma;Nano Lett. , 8 (2008), pp. 2277-2282 [Cited within: 1] [JCR: 13.025]
24.	P. Guo, H. H. Song, X. H. Chen;Electrochem. Commun. , 11 (2009), pp. 1320-1324 [Cited within: 1] [JCR: 4.425]
25.	P. C. Lian, X. F. Zhu, S. Z. Liang, Z. Li, W. S. Yang, H. H. Wang;Electrochim. Acta, 55 (2010), pp. 3909-3914 [Cited within: 1] [JCR: 3.777]
26.	S. M. Paek, E. Yoo, I. Honma;Nano Lett. , 9 (2009), pp. 72-75 [Cited within: 2] [JCR: 13.025]
27.	J. Yao, X. P. Shen, B. Wang, H. K. Liu, G. X. Wang;Electrochem. Commun. , 11 (2009), pp. 1849-1852 [Cited within: 1] [JCR: 4.425]
28.	G. X. Wang, B. Wang, X. L. Wang, J. Park, S. X. Dou, H. Ahn, K. Kim;J. Mater. Chem. , 19 (2009), pp. 8378-8384 [Cited within: 1] [JCR: 5.968]
29.	Y. S. He, D. W. Bai, X. W. Yang, J. Chen, X. Z. Liao, Z. F. Ma;Electrochem. Commun. , 12 (2010), pp. 570-573 [Cited within: 1] [JCR: 4.425]
30.	Z. S. Wu, W. C. Ren, L. Wen, L. B. Gao, J. P. Zhao, Z. P. Chen, G. M. Zhou, F. Li, H. M. Cheng;ACS Nano, 4 (2010), pp. 3187-3194 [Cited within: 2] [JCR: 12.062]
31.	J. J. Liang, Y. F. Xu, D. Sui, L. Zhang, Y. Huang, Y. F. Ma, F. F. Li, Y. S. Chen;J. Phys. Chem. C, 114 (2010), pp. 17465-17471 [Cited within: 2] [JCR: 4.814]
32.	K. Zhou, Y. Zhu, X. Yang, C. Li;New J. Chem. , 34 (2010), pp. 2950-2955 [Cited within: 2] [JCR: 2.966]
33.	L. Wang, Y. Yu, P. C. Chen, D. W. Zhang, C. H. Chen;J. Power Sources, 183 (2008), pp. 717-723 [Cited within: 1] [JCR: 4.675]
34.	G. H. Lee, J. G. Park, Y. M. Sung, K. Y. Chung, W. Il Cho, D. W. Kim;Nanotechnology, 20 (2009), pp. 1-5 [Cited within: 1] [JCR: 3.842]
35.	J. Su, M. H. Cao, L. Ren, C. W. Hu;J. Phys. Chem. C, 115 (2011), pp. 14469-14477 [Cited within: 2] [JCR: 4.814]
36.	H. K. He, C. Gao;ACS Appl. Mater. Int. , 2 (2010), pp. 3201-3210 [Cited within: 2]
37.	E. Kang, Y. S. Jung, A. S. Cavanagh, G. H. Kim, S. M. George, A. C. Dillon, J. K. Kim, J. Lee;Adv. Funct. Mater. , 21 (2011), pp. 2430-2438 [Cited within: 1] [JCR: 9.765]
38.	J. S. Chen, Y. M. Zhang, X. W. Lou;ACS Appl. Mater. Int. , 3 (2011), pp. 3276-3279 [Cited within: 2]
39.	H. P. Cong, X. C. Ren, P. Wang, S. H. Yu;ACS Nano, 6 (2012), pp. 2693-2703 [Cited within: 2] [JCR: 12.062]
40.	K. Lu, G. X. Zhao, X. K. Wang;Chin. Sci. Bull. , 57 (2012), pp. 1223-1234 [Cited within: 1] [JCR: 1.319]
41.	C. Nethravathi, M. Rajamathi;Carbon, 46 (2008), pp. 1994-1998 [Cited within: 1] [JCR: 5.868]

2005

35.749

0.0

Arico

, P.

Bruce

, B.

Scrosati

, J. M.

Tarascon

, W.

Van Schalkwijk

;Nat. Mater. , 4 (2005), pp. 366-377

New materials hold the key to fundamental advances in energy conversion and storage, both of which are vital in order to meet the challenge of global warming and the finite nature of fossil fuels. Nanomaterials in particular offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. This review describes some recent developments in the discovery of nanoelectrolytes and nanoelectrodes for lithium batteries, fuel cells and supercapacitors. The advantages and disadvantages of the nanoscale in materials design for such devices are highlighted.

... Rechargeable lithium-ion batteries (LIBs) are currently being explored for high-power energy applications in a wide range of both civil and military, such as electronic devices, electric vehicles and implantable medical devices^{[1], [2], [3]} ...

2009

9.765

0.0

M. G.

Kim

, J.

Cho

;Adv. Funct. Mater. , 19 (2009), pp. 1497-1514

1 Division of Energy Engineering Ulsan National Institute of Science & Technology Ulsan 689-805 (Korea) 2 Beamline Research Division Pohang Accelerator Laboratory Pohang 790-784 (Korea) * Division of Energy Engineering Ulsan National Institute of Science & Technology Ulsan 689-805 (Korea).

> Reversible nanostructured electrode materials are at the center of research relating to rechargeable lithium batteries, which require high power, high capacity, and high safety. The higher capacities and higher rate capabilities for the nanostructured electrode materials than for the bulk counterparts can be attributed to the higher surface area, which reduces the overpotential and allows faster reaction kinetics at the electrode surface. These electrochemical enhancements can lead to versatile potential applications of the batteries and can provide breakthroughs for the currently limited power suppliers of mobile electronics. This Feature Article describes recent research advances on nanostructured cathode and anode materials, such as metals, metal oxides, metal phosphides and LiCoO 2 , LiNi 1– x M x O 2 with zero-, one-, two-, and three-dimensional morphologies.

2008

0.0

P. G.

Bruce

, B.

Scrosati

, J. M.

Tarascon

;Angew. Chem. Int. Ed. , 47 (2008), pp. 2930-2946

1 School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST, UK, Fax: (+44) 1334-463808 2 Dipartimento di Chimica, Università di Roma, Rome, Italy 3 Laboratoire de Reactivite et de Chimie des Solides, Universite de Picardie, Amiens, France

> Energy storage is more important today than at any time in human history. Future generations of rechargeable lithium batteries are required to power portable electronic devices (cellphones, laptop computers etc.), store electricity from renewable sources, and as a vital component in new hybrid electric vehicles. To achieve the increase in energy and power density essential to meet the future challenges of energy storage, new materials chemistry, and especially new nanomaterials chemistry, is essential. We must find ways of synthesizing new nanomaterials with new properties or combinations of properties, for use as electrodes and electrolytes in lithium batteries. Herein we review some of the recent scientific advances in nanomaterials, and especially in nanostructured materials, for rechargeable lithium-ion batteries.

2008

31.17

0.0

C. K.

Chan

, H. L.

Peng

, G.

Liu

, K.

McIlwrath

, X. F.

Zhang

, R. A.

Huggins

, Y.

Cui

;Nat. Nanotechnol. , 3 (2008), pp. 31-35

There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices 1 . Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g −1 ; ref. 2 ). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials 3, 4 , silicon anodes have limited applications 5 because silicon's volume changes by 400 % upon insertion and extraction of lithium which results in pulverization and capacity fading 2 . Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75 % of this maximum, with little fading during cycling.

... Resulting from the growing demand for high energy and power density, the attention has been shifted from graphitic anodes to electrochemically active metals and transition metal oxides, such as Si^[4], Sn^[5], Co₃O₄^[6], Fe₂O₃^[7], and Fe₃O₄^[6], due to their high theoretical capacities and promising potential ...

2007

14.829

0.0

Derrien

, J.

Hassoun

, S.

Panero

, B.

Scrosati

;Adv. Mater. , 19 (2007), pp. 2336-2340

Chemistry Department, University of Rome “La Sapienza”, 00185 Rome (Italy)

2000

38.597

0.0

Poizot

, S.

Laruelle

, S.

Grugeon

, L.

Dupont

, J. M.

Tarascon

;Nature, 407 (2000), pp. 496-499

Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and how science impacts upon all aspects of society and life.

2008

2.588

0.0

2008

9.765

0.0

W. M.

Zhang

, X. L.

, J. S.

, Y. G.

Guo

, L. J.

Wan

;Adv. Funct. Mater. , 18 (2008), pp. 3941-3946

1 Key Laboratory of Molecular Nanostructure and Nanotechnology Institute of Chemistry, Chinese Academy of Sciences (CAS) Beijing 100190 (PR China) 2 Beijing National Laboratory for Molecular Sciences (BNLMS) Beijing 100190 (PR China) 3 Graduate School of CAS Beijing 100064 (PR China) * Beijing National Laboratory for Molecular Sciences (BNLMS) Beijing 100190 (PR China).

> Carbon-coated Fe 3 O 4 nanospindles are synthesized by partial reduction of monodispersed hematite nanospindles with carbon coatings, and investigated with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electrochemical experiments. The Fe 3 O 4 C nanospindles show high reversible capacity (∼745 mA h g −1 at C/5 and ∼600 mA h g −1 at C/2), high coulombic efficiency in the first cycle, as well as significantly enhanced cycling performance and high rate capability compared with bare hematite spindles and commercial magnetite particles. The improvements can be attributed to the uniform and continuous carbon coating layers, which have several functions, including: i) maintaining the integrity of particles, ii) increasing the electronic conductivity of electrodes leading to the formation of uniform and thin solid electrolyte interphase (SEI) films on the surface, and iii) stabilizing the as-formed SEI films. The results give clear evidence of the utility of carbon coatings to improve the electrochemical performance of nanostructured transition metal oxides as superior anode materials for lithium-ion batteries.

... Among them, Fe₃O₄ has been considered as one of the most prominent candidates for next generation LIBs anode materials for its higher specific capacity, eco-benignity and natural abundance^{[8], [9], [10]} ...

... Nevertheless, the Fe₃O₄ anode materials have poor cycle performance during the continuous charge/discharge cycling because of the severe aggregation and drastic volume change of Fe₃O₄ particles^{[8], [9], [10], [11]}, which reduces the surface area of active materials and leads to the breakdown of electrical connection between anode materials and current collectors, respectively ...

... To alleviate these problems, nanostructured oxide/carbon hybrids, such as carbon nanotube composites^{[11], [12]}, carbon coated nanospindles^[8]/nanorods^[13]/nanocapsules^[14] are being thought to conquer the challenge with good cyclic performance as well as to maintain high specific capacity ...

2009

6.378

0.0

... Among these approaches, carbon coating has been proved to effectively improve the cyclic performance, which serves as a buffer to relieve the volume change and preserve the electrode integrity^{[9], [15], [16]} ...

2010

4.675

0.0

S. Q.

Wang

, J. Y.

Zhang

, C. H.

Chen

;J. Power Sources, 195 (2010), pp. 5379-5381

2010

3.777

0.0

, L.

Huang

, J. S.

Cai

, X. M.

Zheng

, S. G.

Sun

;Electrochim. Acta, 55 (2010), pp. 1140-1144

Abstract Polyvinyl alcohol (PVA) was used as a hydrogen bond functionalizing agent to modify multi-walled carbon nanotubes (CNTs). Nanoparticles of Fe 3 O 4 were then formed along the sidewalls of the as-modified CNTs by the chemical coprecipitation of Fe 2+ and Fe 3+ in the presence of CNTs in an alkaline solution. The structure and electrochemical performance of the Fe 3 O 4 /CNTs nanocomposite electrodes have been investigated in detail. Electrochemical tests indicated that at the 145th cycle, the CNTs–66.7 wt.%Fe 3 O 4 nanocomposite electrode can deliver a high discharge capacity of 656 mAh g −1 and stable cyclic retention. The improvement of reversible capacity and cyclic performance of the Fe 3 O 4 /CNTs nanocomposite could be attributed to the nanosized Fe 3 O 4 particles and the network of CNTs.

2010

14.829

0.0

C. M.

Ban

, Z. C.

, D. T.

Gillaspie

, L.

Chen

, Y. F.

Yan

, J. L.

Blackburn

, A. C.

Dillon

;Adv. Mater. , 22 (2010), pp. E145-E149

1 Materials and Chemical Science Center National Renewable Energy Lab 1617 Cole Boulevard, Golden, Colorado 80401 (USA) 2 National Center for Photovoltaics National Renewable Energy Lab 1617 Cole Boulevard, Golden, Colorado 80401 (USA) * Materials and Chemical Science Center National Renewable Energy Lab 1617 Cole Boulevard, Golden, Colorado 80401 (USA).

2008

4.425

0.0

Liu

, G. X.

Wang

, J. Z.

Wang

, D.

Wexler

;Electrochem. Commun. , 10 (2008), pp. 1879-1882

Abstract Carbon coated magnetite (Fe 3 O 4 ) core-shell nanorods were synthesized by a hydrothermal method using Fe 2 O 3 nanorods as the precursor. Transmission electron spectroscopy (TEM) and high resolution TEM (HRTEM) analysis indicated that a carbon layer was coated on the surfaces of the individual Fe 3 O 4 nanorods. The electrochemical properties of Fe 3 O 4 /carbon nanorods as anodes in lithium-ion cells were evaluated by cyclic voltammetry, ac impedance spectroscopy, and galvanostatic charge/discharge techniques. The as-prepared Fe 3 O 4 /C core-shell nanorods show an initial lithium storage capacity of 1120 mAh/g and a reversible capacity of 394 mAh/g after 100 cycles, demonstrating better performance than that of the commercial graphite anode material.

2011

4.814

0.0

2010

8.238

0.0

G. M.

Zhou

, D. W.

Wang

, F.

, L. L.

Zhang

, N.

, Z. S.

, L.

Wen

, G. Q.

, H. M.

Cheng

;Chem. Mater. , 22 (2010), pp. 5306-5313

† Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, P. R. China ‡ ARC Centre of Excellence for Functional Nanomaterials, AIBN, The University of Queensland, St Lucia, Brisbane 4072, Australia *Corresponding author. E-mail: cheng@imr.ac.cn (H.-M.C); fli@imr.ac.cn (F.L.).

A well-organized flexible interleaved composite of graphene nanosheets (GNSs) decorated with Fe 3 O 4 particles was synthesized through in situ reduction of iron hydroxide between GNSs. The GNS/Fe 3 O 4 composite shows a reversible specific capacity approaching 1026 mA h g −1 after 30 cycles at 35 mA g −1 and 580 mAh g −1 after 100 cycles at 700 mA g −1 as well as improved cyclic stability and excellent rate capability. The multifunctional features of the GNS/Fe 3 O 4 composite are considered as follows: (i) GNSs play a “flexible confinement” function to enwrap Fe 3 O 4 particles, which can compensate for the volume change of Fe 3 O 4 and prevent the detachment and agglomeration of pulverized Fe 3 O 4 , thus extending the cycling life of the electrode; (ii) GNSs provide a large contact surface for individual dispersion of well-adhered Fe 3 O 4 particles and act as an excellent conductive agent to provide a highway for electron transport, improving the accessible capacity; (iii) Fe 3 O 4 particles separate GNSs and prevent their restacking thus improving the adsorption and immersion of electrolyte on the surface of electroactive material; and (iv) the porosity formed by lateral GNSs and Fe 3 O 4 particles facilitates ion transportation. As a result, this unique laterally confined GNS/Fe 3 O 4 composite can dramatically improve the cycling stability and the rate capability of Fe 3 O 4 as an anode material for lithium ion batteries.

2011

3.499

0.0

J. Z.

Wang

, C.

Zhong

, D.

Wexler

, N. H.

Idris

, Z. X.

Wang

, L. Q.

Chen

, H. K.

Liu

;Chem. Eur. J. , 17 (2011), pp. 661-667

1 Institute for Superconducting and Electronic Materials, University of Wollongong, Squires Way, Fairy Meadow, NSW 2519 (Australia), Fax: (+61) 2-4221-5731 2 ARC Center of Excellence for Electromaterials Science, University of Wollongong, Squires Way, Fairy Meadow, NSW 2519 (Australia) 3 School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Northfield Avenue, Wollongong, NSW 2522 (Australia) 4 Laboratory for Solid State Ionics, Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing 100190 (China) * Institute for Superconducting and Electronic Materials, University of Wollongong, Squires Way, Fairy Meadow, NSW 2519 (Australia), Fax: (+61) 2-4221-5731

> Fe 3 O 4 –graphene composites with three-dimensional laminated structures have been synthesised by a simple in situ hydrothermal method. From field-emission and transmission electron microscopy results, the Fe 3 O 4 nanoparticles, around 3–15 nm in size, are highly encapsulated in a graphene nanosheet matrix. The reversible Li-cycling properties of Fe 3 O 4 –graphene have been evaluated by galvanostatic discharge–charge cycling, cyclic voltammetry and impedance spectroscopy. Results show that the Fe 3 O 4 –graphene nanocomposite with a graphene content of 38.0 wt % exhibits a stable capacity of about 650 mAh g −1 with no noticeable fading for up to 100 cycles in the voltage range of 0.0–3.0 V. The superior performance of Fe 3 O 4 –graphene is clearly established by comparison of the results with those from bare Fe 3 O 4 . The graphene nanosheets in the composite materials could act not only as lithium storage active materials, but also as an electronically conductive matrix to improve the electrochemical performance of Fe 3 O 4 .

... These results suggest that more disordered stacking rGO sheets are presented in the rGO-Fe₃O₄ composite ^[16] ...

... Compared with the bare Fe₃O₄, the extra capacity of the rGO-Fe₃O₄ composite may be ascribed to the larger electrochemical active surface area of rGO sheets and grain boundary area of the Fe₃O₄ nanospheres^[16] ...

2008

13.025

0.0

A. A.

Baland in

, S.

Ghosh

, W. Z.

Bao

, I.

Calizo

, D.

Teweldebrhan

, F.

Miao

, C. N.

Lau

;Nano Lett. , 8 (2008), pp. 902-907

Nano-Device Laboratory, Department of Electrical Engineering, University of California−Riverside, Riverside, California 92521, Materials Science and Engineering Program, Bourns College of Engineering, University of California−Riverside, Riverside, California 92521, Department of Physics and Astronomy, University of California−Riverside, Riverside, California 92521 * Corresponding author. E-mail: balandin@ee.ucr.edu . Web address: http://ndl.ee.ucr.edu .,† Nano-Device Laboratory, Department of Electrical Engineering, University of California−Riverside. ,‡ Materials Science and Engineering Program, Bourns College of Engineering, University of California−Riverside. ,§ Department of Physics and Astronomy, University of California−Riverside.

We report the measurement of the thermal conductivity of a suspended single-layer graphene. The room temperature values of the thermal conductivity in the range ∼(4.84 ± 0.44) × 10 3 to (5.30 ± 0.48) × 10 3 W/mK were extracted for a single-layer graphene from the dependence of the Raman G peak frequency on the excitation laser power and independently measured G peak temperature coefficient. The extremely high value of the thermal conductivity suggests that graphene can outperform carbon nanotubes in heat conduction. The superb thermal conduction property of graphene is beneficial for the proposed electronic applications and establishes graphene as an excellent material for thermal management.

... Graphene, a single layer of sp²-bonded carbon atoms patterned in a hexagonal lattice, exhibits prominent thermal stability ^[17], superior electronic conductivity ^[18], remarkable structural flexibility ^[19], and high specific surface area ^[20] ...

2005

38.597

0.0

K. S.

Novoselov

, A. K.

Geim

, S. V.

Morozov

, D.

Jiang

, M. I.

Katsnelson

, I. V.

Grigorieva

, S. V.

Dubonos

, A. A.

Firsov

;Nature, 438 (2005), pp. 197-200

2008

0.0

Lee

, X. D.

Wei

, J. W.

Kysar

, J.

Hone

;Science, 321 (2008), pp. 385-388

1 Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA. 2 Defense Advanced Research Projects Agency Center for Integrated Micro/Nano-Electromechanical Transducers (iMINT), ColumbiaUniversity, New York, NY 10027, USA. 3 Center for Nanostructured Materials, Columbia University, New York, NY 10027, USA. 4 Center for Electronic Transport in Molecular Nanostructures, Columbia University, New York, NY 10027, USA. ↵ * To whom correspondence should be addressed. E-mail: jh2228@columbia.edu

2001

5.868

0.0

Peigney

, C.

Laurent

, E.

Flahaut

, R. R.

Bacsa

;Carbon, 39 (2001), pp. 507-514

Abstract The theoretical external specific surface area of single- and multi-walled carbon nanotubes and of carbon nanotube bundles is calculated as a function of their characteristics (diameter, number of walls, number of nanotubes in a bundle). The results are reported in diagrams and tables useful to correlate the microscopic characteristics and the specific surface area of samples. The calculated values are in good agreement with the microscopic characteristics and the specific surface area measurements which have been previously reported in the literature. The specific surface area is a macroscopic parameter which can be helpful to adjust the synthesis conditions of carbon nanotubes.

2007

35.749

0.0

A. K.

Geim

, K. S.

Novoselov

;Nat. Mater. , 6 (2007), pp. 183-191

Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

... These unique properties of graphene make it become an ideal material for many applications, including microelectronics, batteries, supercapacitors, sensors and mechanical resonators ^{[21], [22], [23], [24], [25]} ...

2009

0.0

A. K.

Geim

;Science, 324 (2009), pp. 1530-1534

Manchester Centre for Mesoscience and Nanotechnology, University of Manchester, Oxford Road, Manchester M13 9PL, UK.

2008

13.025

0.0

Yoo

, J.

Kim

, E.

Hosono

, H.

Zhou

, T.

Kudo

, I.

Honma

;Nano Lett. , 8 (2008), pp. 2277-2282

Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Umezono 1-1-1, Central 2, Tsukuba, Ibaraki 305-8568 Japan; Nano Ionics Materials Group, National Institute of Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044 Japan * Corresponding author. Phone and fax: +81 298 61 5648 . E-mail: i.homma@aist.go.jp .,† National Institute of Advanced Industrial Science and Technology. ,‡ National Institute of Materials Science.

The lithium storage properties of graphene nanosheet (GNS) materials as high capacity anode materials for rechargeable lithium secondary batteries (LIB) were investigated. Graphite is a practical anode material used for LIB, because of its capability for reversible lithium ion intercalation in the layered crystals, and the structural similarities of GNS to graphite may provide another type of intercalation anode compound. While the accommodation of lithium in these layered compounds is influenced by the layer spacing between the graphene nanosheets, control of the intergraphene sheet distance through interacting molecules such as carbon nanotubes (CNT) or fullerenes (C 60 ) might be crucial for enhancement of the storage capacity. The specific capacity of GNS was found to be 540 mAh/g, which is much larger than that of graphite, and this was increased up to 730 mAh/g and 784 mAh/g, respectively, by the incorporation of macromolecules of CNT and C 60 to the GNS.

2009

4.425

0.0

Guo

, H. H.

Song

, X. H.

Chen

;Electrochem. Commun. , 11 (2009), pp. 1320-1324

Abstract Graphene nanosheets (GNSs) were prepared from artificial graphite by oxidation, rapid expansion and ultrasonic treatment. The morphology, structure and electrochemical performance of GNSs as anode material for lithium-ion batteries were systematically investigated by high-resolution transmission electron microscope, scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy and a variety of electrochemical testing techniques. It was found that GNSs exhibited a relatively high reversible capacity of 672 mA h/g and fine cycle performance. The exchange current density of GNSs increased with the growth of cycle numbers exhibiting the peculiar electrochemical performance.

2010

3.777

0.0

P. C.

Lian

, X. F.

Zhu

, S. Z.

Liang

, Z.

, W. S.

Yang

, H. H.

Wang

;Electrochim. Acta, 55 (2010), pp. 3909-3914

Abstract High quality graphene sheets were prepared from graphite powder through oxidation followed by rapid thermal expansion in nitrogen atmosphere. The preparation process was systematically investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and Brunauer–Emmett–Teller (BET) measurements. The morphology and structure of graphene sheets were characterized by scanning electron microscope (SEM) and high-resolution transmission electron microscopy (HRTEM). The electrochemical performances were evaluated in coin-type cells versus metallic lithium. It is found that the graphene sheets possess a curled morphology consisting of a thin wrinkled paper-like structure, fewer layers (∼4 layers) and large specific surface area (492.5 m 2 g −1 ). The first reversible specific capacity of the prepared graphene sheets was as high as 1264 mA h g −1 at a current density of 100 mA g −1 . Even at a high current density of 500 mA g −1 , the reversible specific capacity remained at 718 mA h g −1 . After 40 cycles, the reversible capacity was still kept at 848 mA h g −1 at the current density of 100 mA g −1 . These results indicate that the prepared high quality graphene sheets possess excellent electrochemical performances for lithium storage.

2009

13.025

0.0

S. M.

Paek

, E.

Yoo

, I.

Honma

;Nano Lett. , 9 (2009), pp. 72-75

Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba, Ibaraki 305-8568, Japan * To whom correspondence should be addressed. E-mail: i.homma@aist.go.jp . Tel/Fax: +81-29-861-5648 .

To fabricate nanoporous electrode materials with delaminated structure, the graphene nanosheets (GNS) in the ethylene glycol solution were reassembled in the presence of rutile SnO 2 nanoparticles. According to the TEM analysis, the graphene nanosheets are homogeneously distributed between the loosely packed SnO 2 nanoparticles in such a way that the nanoporous structure with a large amount of void spaces could be prepared. The obtained SnO 2 /GNS exhibits a reversible capacity of 810 mAh/g; furthermore, its cycling performance is drastically enhanced in comparison with that of the bare SnO 2 nanoparticle. After 30 cycles, the charge capacity of SnO 2 /GNS still remained 570 mAh/g, that is, about 70% retention of the reversible capacity, while the specific capacity of the bare SnO 2 nanoparticle on the first charge was 550 mAh/g, dropping rapidly to 60 mAh/g only after 15 cycles. The dimensional confinement of tin oxide nanoparticles by the surrounding GNS limits the volume expansion upon lithium insertion, and the developed pores between SnO 2 and GNS could be used as buffered spaces during charge/discharge, resulting in the superior cyclic performances.

... In LIBs, graphene-based composites have emerged as quite intriguing electrode materials ^{[26], [27], [28], [29], [30]} ...

... 7 eV) ^[26] ...

2009

4.425

0.0

Yao

, X. P.

Shen

, B.

Wang

, H. K.

Liu

, G. X.

Wang

;Electrochem. Commun. , 11 (2009), pp. 1849-1852

Abstract An in situ chemical synthesis approach has been developed to prepare SnO 2 –graphene nanocomposite. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO 2 nanoparticles (4–6 nm in size) on graphene matrix. The electrochemical reactivities of the SnO 2 –graphene nanocomposite as anode material were measured by cyclic voltammetry and galvanostatic charge/discharge cycling. The as-synthesized SnO 2 –graphene nanocomposite exhibited a reversible lithium storage capacity of 765 mAh/g in the first cycle and an enhanced cyclability, which can be ascribed to 3D architecture of the SnO 2 –graphene nanocomposite.

... In LIBs, graphene-based composites have emerged as quite intriguing electrode materials ^{[26], [27], [28], [29], [30]} ...

2009

5.968

0.0

... In LIBs, graphene-based composites have emerged as quite intriguing electrode materials ^{[26], [27], [28], [29], [30]} ...

2010

4.425

0.0

Y. S.

, D. W.

Bai

, X. W.

Yang

, J.

Chen

, X. Z.

Liao

, Z. F.

;Electrochem. Commun. , 12 (2010), pp. 570-573

Abstract A Co(OH) 2 −graphene nanosheets (Co(OH) 2 −GNS) composite as a high performance anode material was firstly prepared through a simultaneous hydrothermal method. The structure, morphology and electrochemical performance of the obtained samples were systematically investigated by X-ray diffraction (XRD), transmission electron microscope (TEM) and electrochemical measurements. According to the TEM analysis, the surface of the Co(OH) 2 is surrounded with GNS in the Co(OH) 2 −GNS composite. The specific discharge (lithiation) and charge (delithiation) capacities of Co(OH) 2 −GNS attain to 1599 and 1120 mAh/g at a current density of 200 mA/g in the first cycle, respectively. After 30 cycles, the reversible capacity of Co(OH) 2 −GNS is still 910 mAh/g with the retention of 82%. The particular structure of Co(OH) 2 particles surrounded by the GNS could limit the volume change during cycling and provide an excellent electronic conduction pathway, which could be the main reason for the remarkable improvement of electrochemical performance.

... In LIBs, graphene-based composites have emerged as quite intriguing electrode materials ^{[26], [27], [28], [29], [30]} ...

2010

12.062

0.0

Z. S.

, W. C.

Ren

, L.

Wen

, L. B.

Gao

, J. P.

Zhao

, Z. P.

Chen

, G. M.

Zhou

, F.

, H. M.

Cheng

;ACS Nano, 4 (2010), pp. 3187-3194

Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People’s Republic of China * Address correspondence to cheng@imr.ac.cn , wcren@imr.ac.cn .

We report a facile strategy to synthesize the nanocomposite of Co 3 O 4 nanoparticles anchored on conducting graphene as an advanced anode material for high-performance lithium-ion batteries. The Co 3 O 4 nanoparticles obtained are 10−30 nm in size and homogeneously anchor on graphene sheets as spacers to keep the neighboring sheets separated. This Co 3 O 4 /graphene nanocomposite displays superior Li-battery performance with large reversible capacity, excellent cyclic performance, and good rate capability, highlighting the importance of the anchoring of nanoparticles on graphene sheets for maximum utilization of electrochemically active Co 3 O 4 nanoparticles and graphene for energy storage applications in high-performance lithium-ion batteries.

... In LIBs, graphene-based composites have emerged as quite intriguing electrode materials ^{[26], [27], [28], [29], [30]} ...

... 001 V, indicating a typical character for transition metal oxide anodes^[30] ...

2010

4.814

0.0

J. J.

Liang

, Y. F.

, D.

Sui

, L.

Zhang

, Y.

Huang

, Y. F.

, F. F.

, Y. S.

Chen

;J. Phys. Chem. C, 114 (2010), pp. 17465-17471

Key Laboratory of Functional Polymer Materials and Center for Nanoscale Science & Technology, Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China * To whom correspondence should be addressed. E-mail: yschen99@nankai.edu.cn .

The emerging field of free-standing and flexible paperlike materials based on graphene sheets has become the focus of considerable research in recent years because of the scientific and technological significance of these materials. In particular, multifunctional flexible graphene-based films or papers are in high demand for various applications. Herein, we report the fabrication of magnetic, electrically conducting, and flexible paper composed of graphene and nanoscale Fe 3 O 4 particles made using a simple yet versatile solution-processed approach. The conductive, magnetic, and mechanical properties of these free-standing hybrid papers with different loadings of nanoscale Fe 3 O 4 particles were investigated. In addition to the excellent electrical conductivity and mechanical strength, the obtained flexible graphene/Fe 3 O 4 hybrid papers also show superparamagnetism, which can be tuned easily through modulation of the loading of Fe 3 O 4 nanoparticles. Combining all of these outstanding properties, we have fabricated and demonstrated a magnetic-controlled conductive switch using these flexible and multifunctional graphene/Fe 3 O 4 hybrid papers.

... Recently, the Fe₃O₄ particles combined with graphene have been reported and display several advantages ^{[31], [32], [33], [34]} ...

... However, the reported strategies for preparing graphene-Fe₃O₄ composite are complicated, involving additional reduction agents such as N₂H₄^[39], NaBH₄^[40] and additional annealing steps ^[31] ...

2010

2.966

0.0

... Recently, the Fe₃O₄ particles combined with graphene have been reported and display several advantages ^{[31], [32], [33], [34]} ...

... In a typical procedure^[32], 50 ml of ethylene glycol was dropped into 10 ml GO suspension by dropper and the mixture was sonicated for 1 h, then 0 ...

2008

4.675

0.0

Wang

, Y.

, P. C.

Chen

, D. W.

Zhang

, C. H.

Chen

;J. Power Sources, 183 (2008), pp. 717-723

... Recently, the Fe₃O₄ particles combined with graphene have been reported and display several advantages ^{[31], [32], [33], [34]} ...

2009

3.842

0.0

... Recently, the Fe₃O₄ particles combined with graphene have been reported and display several advantages ^{[31], [32], [33], [34]} ...

2011

4.814

0.0

... Firstly, ultrathin graphene sheets can prevent the aggregation of Fe₃O₄ particles ^{[35], [36]} ...

... Large irreversible capacity observed in the first cycle may be caused by the formation of solid electrolyte interphase (SEI) and the reaction of the lithium-ion with oxygen-containing functional groups remaining unreduced on the surface of rGO sheets^[35] ...

2010

0.0

H. K.

, C.

Gao

;ACS Appl. Mater. Int. , 2 (2010), pp. 3201-3210

MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, P. R. China * Corresponding author. E-mail: chaogao@zju.edu.cn .

The amazing properties of graphene are triggering extensive interests of both scientists and engineers, whereas how to fully utilize the unique attributes of graphene to construct novel graphene-based composites with tailor-made, integrated functions remains to be a challenge. Here, we report a facile approach to multifunctional iron oxide nanoparticle-attached graphene nanosheets (graphene@Fe 3 O 4 ) which show the integrated properties of strong supraparamagnetism, electrical conductivity, highly chemical reactivity, good solubility, and excellent processability. The synthesis method is efficient, scalable, green, and controllable and has the feature of reduction of graphene oxide and formation of Fe 3 O 4 nanoparticles in one step. When the feed ratios are adjusted, the average diameter of Fe 3 O 4 nanoparticles (1.2−6.3 nm), the coverage density of Fe 3 O 4 nanoparticles on graphene nanosheets (5.3−57.9%), and the saturated magnetization of graphene@Fe 3 O 4 (0.5−44.1 emu/g) can be controlled readily. Because of the good solubility of the as-prepared graphene@Fe 3 O 4 , highly flexible and multifunctional films composed of polyurethane and a high content of graphene@Fe 3 O 4 (up to 60 wt %) were fabricated by the solution-processing technique. The graphene@Fe 3 O 4 hybrid sheets showed electrical conductivity of 0.7 S/m and can be aligned into a layered-stacking pattern in an external magnetic field. The versatile graphene@Fe 3 O 4 nanosheets hold great promise in a wide range of fields, including magnetic resonance imaging, electromagnetic interference shielding, microwave absorbing, and so forth.

... Firstly, ultrathin graphene sheets can prevent the aggregation of Fe₃O₄ particles ^{[35], [36]} ...

... It can be assigned to the decomposition of rGO nanosheets^[36] ...

2011

9.765

0.0

Kang

, Y. S.

Jung

, A. S.

Cavanagh

, G. H.

Kim

, S. M.

George

, A. C.

Dillon

, J. K.

Kim

, J.

Lee

;Adv. Funct. Mater. , 21 (2011), pp. 2430-2438

1 Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyo-ja dong, Pohang, 790-784, Korea 2 School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31, Hyo-ja dong, Pohang, 790-784, Korea 3 National Renewable Energy Laboratory, Golden, CO80401, USA 4 Department of Physics, University of Colorado at Boulder, Boulder, CO 80309-0215, USA 5 George, Department of Chemistry and Biochemistry, and Department of Chemical and Biological Engineering, University of Colorado at Boulder, CO 80309-0215, USA * Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyo-ja dong, Pohang, 790-784, Korea.

> Fe 3 O 4 nanocrystals confined in mesocellular carbon foam (MSU-F-C) are synthesized by a “ host–guest ” approach and tested as an anode material for lithium-ion batteries (LIBs). Briefly, an iron oxide precursor, Fe(NO 3 ) 3 ·9H 2 O, is impregnated in MSU-F-C having uniform cellular pores ∼30 nm in diameter, followed by heat-treatment at 400 °C for 4 h under Ar. Magnetite Fe 3 O 4 nanocrystals with sizes between 13–27 nm are then successfully fabricated inside the pores of the MSU-F-C, as confirmed by transmission electron microscopy (TEM), dark-field scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and nitrogen sorption isotherms. The presence of the carbon most likely allows for reduction of some of the Fe 3+ ions to Fe 2+ ions via a carbothermoreduction process. A Fe 3 O 4 /MSU-F-C nanocomposite with 45 wt% Fe 3 O 4 exhibited a first charge capacity of 1007 mA h g −1 (Li + extraction) at 0.1 A g −1 (∼0.1 C rate) with 111% capacity retention at the 150 th cycle, and retained 37% capacity at 7 A g −1 (∼7 C rate). Because the three dimensionally interconnected open pores are larger than the average nanosized Fe 3 O 4 particles, the large volume expansion of Fe 3 O 4 upon Li-insertion is easily accommodated inside the pores, resulting in excellent electrochemical performance as a LIB anode. Furthermore, when an ultrathin Al 2 O 3 layer (

... Secondly, the graphene can provide void space against the volume changes of the Fe₃O₄ particles during lithium-ion insertion/extraction process ^[37], which can improve the cycling performance ...

2011

0.0

J. S.

Chen

, Y. M.

Zhang

, X. W.

Lou

;ACS Appl. Mater. Int. , 3 (2011), pp. 3276-3279

School of Chemical and Biomedical Engineering, Nanyang Technological University , 70 Nanyang Drive, Singapore 637457 Energy Research Institute @ NTU, Nanyang Technological University , 50 Nanyang Drive, Singapore 637553 E-mail: xwlou@ntu.edu.sg . Tel.: +65 6316 8879 ; Fax: +65 6791 1761 .

Poly(acrylic acid) (PAA)-entangled Fe 3 O 4 nanospheres are synthesized via a facile solvothermal method. In this system, ethylenediamine plays a very important role to control the uniformity of the nanospheres, and the PAA molecules serve as the carbon source that transforms into a carbon matrix after the heat treatment under an inert atmosphere. These uniform Fe 3 O 4 nanospheres with carbon matrix support manifest greatly enhanced lithium storage properties over prolonged cycling, with a reversible capacity of 712 mA h g –1 retained after 60 charge/discharge cycles. However, the carbon-free counterpart can only deliver a much lower capacity of 328 mA h g –1 .

... Finally, the Fe₃O₄ particles are anchored on the planes of graphene, which may lead to a high rate performance due to the high electronic conductivity of graphene sheets and short path length for Li⁺ transport of Fe₃O₄ particles ^[38] ...

... and both sides of rGO sheets can adsorb lithium-ion, which leads to two layers of lithium for its insertion/desertion during charging and discharging^[38] ...

2012

12.062

0.0

H. P.

Cong

, X. C.

Ren

, P.

Wang

, S. H.

;ACS Nano, 6 (2012), pp. 2693-2703

Division of Nanomaterials and Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemistry, National Synchrotron Radiation Laboratory, University of Science and Technology of China , Hefei, Anhui 230026, People's Republic of China *Address correspondence to shyu@ustc.edu.cn .

We report a one-step fabrication of macroscopic multifunctional graphene-based hydrogels with robust interconnected networks under the synergistic effects of the reduction of graphene oxide sheets by ferrous ions and in situ simultaneous deposition of nanoparticles on graphene sheets. The functional components, such as α-FeOOH nanorods and magnetic Fe 3 O 4 nanoparticles, can be easily incorporated with graphene sheets to assemble macroscopic graphene monoliths just by control of pH value under mild conditions. Such functional graphene-based hydrogels exhibit excellent capability for removal of pollutants and, thus, could be used as promising adsorbents for water purification. The method presented here is proved to be versatile to induce macroscopic assembly of reduced graphene sheets with other functional metal oxides and thus to access a variety of graphene-based multifunctional nanocomposites in the form of macroscopic hydrogels or aerogels.

... For rGO-Fe₃O₄ composite, the band at 581 cm^-1 was the characteristic stretching vibrations of Fe-O ^[39] ...

2012

1.319

0.0

, G. X.

Zhao

, X. K.

Wang

;Chin. Sci. Bull. , 57 (2012), pp. 1223-1234

Graphene is an interesting two-dimensional carbon allotrope that has attracted considerable research interest because of its unique structure and physicochemical properties. Studies have been conducted on graphene-based nanomaterials including modified graphene, graphene/semiconductor hybrids, graphene/metal nanoparticle composites, and graphene-complex oxide composites. These nanomaterials inherit the unique properties of graphene, and the addition of functional groups or the nanoparticle composites on their surfaces improves their performance. Applications of these materials in pollutant removal and environmental remediation have been explored. From the viewpoint of environmental chemistry and materials, this paper reviews recent important advances in synthesis of graphene-related materials and their application in treatment of environmental pollution. The roles of graphene- based materials in pollutant removal and potential research are discussed.

1. Key Laboratory of Audit Information Engineering, Nanjing Audit University, Nanjing 210029, China; 2. Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China

2008

5.868

0.0

Nethravathi

, M.

Rajamathi

;Carbon, 46 (2008), pp. 1994-1998

Abstract Chemically modified graphene sheets are obtained through solvothermal reduction of colloidal dispersions of graphite oxide in various solvents. Reduction occurs at relatively low temperatures (120–200 °C). Reaction temperature, the self-generated pressure in the sealed reaction vessel and the reducing power of the solvent influences the extent of reduction of graphite oxide sheets to modified graphene sheets.

... Preparation of rGO-Fe₃O₄ compositeGO was synthesized from natural graphite powder by a modified Hummers method^[41] ...