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onion-like carbon nanocapsules as high-performance anode material for lithium-ion batteries
Author's Accepted Manuscript
Facile synthesis of core/shell-structured Sn/ onion-like carbon nanocapsules as Highperformance anode material for lithium-ion batteries Caiyun Cui, Xianguo Liu, Niandu Wu, Yuping Sun
www.elsevier.com/locate/matlet
PII: DOI: Reference:
S0167-577X(14)02221-6 http://dx.doi.org/10.1016/j.matlet.2014.12.055 MLBLUE18206
To appear in:
Materials Letters
Received date: 8 October 2014 Revised date: 9 December 2014 Accepted date: 11 December 2014 Cite this article as: Caiyun Cui, Xianguo Liu, Niandu Wu, Yuping Sun, Facile synthesis of core/shell-structured Sn/onion-like carbon nanocapsules as Highperformance anode material for lithium-ion batteries, Materials Letters, http: //dx.doi.org/10.1016/j.matlet.2014.12.055 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Facile synthesis of core/shell-structured Sn/onion-like carbon nanocapsules as high-performance anode material for lithium-ion batteries Caiyun Cuia, Xianguo Liua,*, Niandu Wua, Yuping Sunb a
School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, PR
China. b
Center for Engineering practice and Innovation Education, Anhui University of Technology, Maanshan
243032, PR China.
Abstract Core/shell-structured Sn/C nanocapsules with Sn nanoparticles as the core and defective onion-like carbon as the shell are synthesized by a modified arc-discharge method. The Sn/C nanocapsule anode maintains a high discharge capacity of 585 mAh g-1 after 100 cycles at 0.1 A g-1 and obtains a high reversible capacity of ~ 480 mAh g-1 at 5 A g-1. The remarkable electrochemical performance is attributed to the effective combination of the Sn nanoparticle cores and the defective onion-like carbon shells, which simultaneously solves the major problems of pulverization, loss of electrical contact, and particle aggregation encountered in Sn anode.
Keywords: Core-shell; Sn; Carbon materials; Nanocomposites; Anode; Lithium-ion batteries
*Corresponding author Address: School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, PR China. Tel/Fax: +86-555-2311570 E-mail address: [email protected] 1
1. Introduction Rechargeable lithium-ion batteries (LIBs), as the most important type of power sources for portable electronic devices, are being actively considered as battery power systems for electric and hybrid vehicles [1-8]. To improve the energy density, cycling stability, and rate capacity of such battery power systems, a great deal of efforts has been put on enhancing electrode performance. Tin (Sn) has received enormous research interest as a potential substitute for carbon anode because of its higher theoretical capacity (993 mAh g-1) than the traditional carbon anode (372 mAh g-1) [2]. However, practical applications of Sn anode is impeded by the large volume change of about 259% during the alloying/dealloying [1-5]. Therefore, it is urgently needed to modify Sn anode with enhanced structural stability for prolonged cycle life. Designing uniquely nanostructured Sn anode such as 0D nanoparticles [1,2,8], 1D nanorods/nanowires [3, 4], 2D nanosheets [5], and 3D porous nanostructures [6], is one of the effective ways to withstand the huge volume change during the charge-discharge process. Another way is to introduce carbon materials into Sn anode [7,8]. Recently, Sn nanoparticles self-inserted between graphene interlayers, Sn nanoparticles encapsulated in spherical hollow carbon and Sn nanoparticles dispersed in a carbon matrix have been reported as anode materials for LIBs [2]. Among Sn/C nanocomposites, core/shell structured nanocapsules with Sn nanoparticles as the core and onion-like carbon as the shell are of particular interest due to the improved strain accommodation capability and thus the enhanced structural stability. For examples, NiO/C, Co3O4/C, and CuO/C nanocapsules all exhibit markedly enhanced lithium storage performance by virtue of their structural characteristics [9-11]. In this paper, we report the synthesis and electrochemical properties of Sn/C nanocapsules with Sn nanoparticles as the core and defective onion-like carbon as the shell. The obtained Sn/C
2
nanocapsules exhibit excellent cycling stability and rate performance in LIBs. 2.
Experiment The Sn/C nanocapsules were synthesized by an arc-discharge method in accordance with the
report in Ref [12]. Bulk Sn was used as the anode, while the cathode was a graphite needle. After the chamber was evacuated in a vacuum of 6.6×10-3 Pa, liquid ethanol of 50 mL was introduced into the chamber together with pure argon of 1.2 ×104 Pa. During the present arc-discharge process, the arc was shot at a joint near the Sn and the current was maintained at 50 A for 15 min. After being passviated in argon for 12 h, the Sn/C nanocapsules were collected on the top of the chamber. The phase analysis for the product was performed by using a powder X-ray diffraction (XRD) technique, acquired by a Bruker D8 Advance X-ray diffractometer. The morphology and size distribution of the products were observed by a high-resolution transmission electron microscope (HRTEM) images from JEOL-2100F. The electrodes for the electrochemical characterization were fabricated by mixing
Sn/C
nanocapsules, acetylene black as a conducting agent, and polyvinylidene difluoride (70:15:15 by weight) dissolved in N-methyl-2-pyrrolidone as a binder to form a slurry, followed by coating on copper foil as well as pressing and drying in a vacuum baking oven at 120 oC for 3 h. The coin-type cells (CR2016) were assembled in an argon-filled glove box. Celgard 2325 was used as the separator. Pure lithium disks were used as the counter and reference electrodes. The electrolyte was 1 M LiPF6 in ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (1:1:1 by volume). Cyclic voltammograms (CV) were recorded using the PAR2273 Electrochemical Measurement System (EG&G Princeton Applied Research), and the cells were cycled by Land 2001A with a scan rate of 0.1 mV s-1 at room temperature.
3
3.
Results and Discussion
Fig. 1 XRD pattern of Sn/C nanocapsules.
The XRD pattern for the Sn/C nanocapsules is given in Fig. 1. It is clearly seen that all peaks can be well-indexed to Sn (JCPDS No. 04-0673). There are no Sn-oxide peaks detectable in the XRD patterns, indicating that the products may be free from surface oxidation. It should be noted that there are no evidences of carbon, suggesting its small amount (less than 3% in the products), if any [9-11]. Carbon atoms are usually favorable to form the shell of nanoparticles in an onion-like structure and can protect it from oxidization.
Fig. 2 (a) TEM and (b) HRTEM images of Sn/C nanocapsules.
The TEM image in Fig. 2(a) shows a group of spherical Sn/C nanocapsules with a diameter 4
distribution of 5-30 nm. From Fig. 2(a), hollow structure is seen between the Sn nanoparticles and the onion-like carbon shell, and this hollow structure can accommodate the volume change of the Sn nanoparticles during the charge-discharge cycling. The HRTEM image in Fig. 2(b) indicates that the nanoparticle core is well-coated by the onion-like C shell with a thickness of about 1.85 nm. In the Sn nanoparticle core, the d-spacing is found to be 0.202 nm, corresponding to the {211} of Sn. The lattice plane spacing of the coating layers is about 0.34 nm, corresponding to the (002) of graphite. Nevertheless, a mass of lattice imperfections can be seen in the outer shells as a consequence of the serious bending and collapsing of the graphite atom layer.
Fig. 3. Electrochemical properties of as-prepared Sn/C nanocapsules. (a) CV curves at a rate of 0.1 mV s-1, (b) charge/discharge profiles at different cycles with a current density of 100 mA g-1, (c) cycling performance and Coulombic efficiency at a current density of 100 mA g-1, and (d) rate performance.
The Sn/C nanocapsules are used as anode material for LIBs to study the electrochemical properties. To understand the Li-ion insertion and extraction process in the nanocapsules during the discharge/charge cycling, CV was measured between 0.005 V and 2.0 V vs Li/Li+ at a scan rate of 0.1 5
mVs-1. During the first cathodic sweep, a reduction peak locates at 0.59 V and the several anodic peaks are related to the deintercalation of lithium from the cathode materials for the first time [13]. In the subsequent sweeps, two reduction peaks are observed at 0.30 and 0.57 V, which are mainly due to the alloying of lithium with Sn for the formation of different types of Li-Sn alloys, while the oxidation peaks at 0.70 and 0.79 V are associated with the reversible delithiation process of lithium from different types of LixSn alloys and the background is related to Li+ extraction form carbon shells [12]. Except for the first one, all CV cycles overlap well, indicating a good capacity retention after the first cycle. Fig. 3(b) shows the charge/discharge voltage curves for the 1st, 5th, 10th, and 20th cycles of the Sn/C/Li cell with a current densities of 100 mA g-1 (0.2 C). It is clearly demonstrated that the first discharge and charge capacities are 1012.0 and 622.1 mAh g-1 of the Sn/C nanocapsule anode with a low coulombic efficiency of 61.5%. Such large initial irreversible loss is generally related to the decomposition of electrolyte, the formation of a SEI layer on the anode surface, and the storage of Li+ in onion-like carbon nanoshell [14]. Comparing to the theoretical capacity of Sn (992 mAh g-1) and also graphite (372 mAh g-1), the extra discharge capacity of our Sn/C nanocapsules is mainly caused by the decomposition of the electrolyte with the SEI formation [6]. The subsequent discharge curve differs considerably from the first cycle because of the formation of the dense SEI film on the surface of the anodes in the first discharge cycle [13]. Despite the large initial loss, our Sn/C nanocapsule anode exhibits very stable cycling performance under such testing conditions (Fig. 3(c)). The discharge capacity also reaches 585 mAh g-1 after 100 cycles, which is still higher than 372 mAh g-1 of graphite. The efficiency increases to above 96 % after the 5th cycle. The rate performance of Sn/C nanocapsules at different current densities is shown in Fig. 3(d).
6
The specific reversible capacity falls moderately with increasing current density from a value of about 620 mAh g-1 at 0.1 A g-1 to about 520 mAh g-1 at 2 A g-1. Even at a higher current density of 5 A g-1, the capacity of ~ 480 mAh g-1 is still higher than the practical capacity of graphite. At each current density, the capacity is fairly stable. The superior rate capability of our Sn/C nanocapsules can be explained by the combination of the electric conductivity from the onion-like carbon nanoshell and the short diffusion path for both electrons and ions provided by the Sn nanoparticles and the defective carbon nanoshells. When decreasing the current desnisty from 5A g-1 to 0.1 A g-1, about 97.6 % of the initial reversible capacity at 0.1 A g-1 is recovered, indicating that the core/shell structure of our Sn/C nanocapsules could preserve the integrity of the electrode and thus could be tolerant to variations in charge and discharge currents [15]. 4. Conclusion A facile and practical synthesis route has been developed to synthesize Sn/C nanocapsules. As the anode of LIBs, the Sn/C nanocapsules with the combination of Sn nanoparticle core and the defective onion-like carbon nanoshells have demonstrated improved cycling stability and rate capability. The discharge capacity has reached a high value of about 585 mAh g-1 after 100 cycles. At an elevated current density of 5 A g-1, a high reversible capacity of about 480 mAh g-1 has been obtained. The arc-discharge method makes Sn/C nancapsules very promising as an anode material for LIBs. Acknowledgments This study was supported by the National Natural Science Foundation of China (No. 51201002).
7
References [1] Nobili F, Meschini I, Mancini M, Tossici R, Croce F. Electrochim Acta 2013;107 85-92. [2] Xu YH, Liu Q, Zhu YJ, Liu YH, Wang CS. Nano Lett 2013; 13: 470-4. [3] Hsu KC, Liu CE, Chen PC, Chiu HT. J Mater Chem 2012; 22: 21533-9. [4] Ni W, Wang YB, Xu R. Part Part Syst Charact 2013; 30: 873-80. [5] Zhou XY, Zou YL, Yang J. J Power Sources 2014; 253: 287-93. [6] Wang G, Ma YQ, Liu ZY, Wu JN. Electrochim Acta 2012; 65: 275-9. [7] Lu ZZ, Wang HK. CrystEngComm 2014; 16: 550-5. [8] Wang CD, Li Y, Chui YS, Wu QH, Chen XF, Zhang WJ. Nanoscale 2013; 5: 10599-604. [9] Liu XG, Or SW, Jin CG, Lv YH, Sun YP. Carbon 2013; 60: 215-20. [10] Liu XG, Or SW, Jin CG, Lv YH, Sun YP. Electrochim Acta 2013; 100: 140-6. [11] Liu XG, Bi NN, Or SW, Sun YP. J Alloys Compd 2014; 587: 1-5. [12] Wang ZH, Han Z, Geng DY, Zhang ZD. Chem Phys Lett 2010; 489: 187-90. [13] Tao XY, Wu R, Xia Y, Huang H, Chai WC, Zhang WK. ACS Appl Mater Interfaces 2014; 4: 3696-702. [14] Yu Y, Gu L,Wang CL, Dhanabalan A, Maier J. Ange Chem Inter Ed 2009; 17: 6485-9. [15] Zhu ZQ, Wang SW, Du J, Jin Q, Zhang TR, Chen J. Nano Lett 2014; 14: 153-7.
8
HIGHLIGHTS
Sn@C core-shell nanocapsules have been prepared. Sn@C nanocapsules obtain a discharge capacity of 585 mAh g-1 after 100 cycles at 0.1 A g-1. The core-shell structure leads to the remarkable electrochemical performances.
Graphical Abstract
9
Facile synthesis of core/shell-structured Sn/ onion-like carbon nanocapsules as Highperformance anode material for lithium-ion batteries Caiyun Cui, Xianguo Liu, Niandu Wu, Yuping Sun
www.elsevier.com/locate/matlet
PII: DOI: Reference:
S0167-577X(14)02221-6 http://dx.doi.org/10.1016/j.matlet.2014.12.055 MLBLUE18206
To appear in:
Materials Letters
Received date: 8 October 2014 Revised date: 9 December 2014 Accepted date: 11 December 2014 Cite this article as: Caiyun Cui, Xianguo Liu, Niandu Wu, Yuping Sun, Facile synthesis of core/shell-structured Sn/onion-like carbon nanocapsules as Highperformance anode material for lithium-ion batteries, Materials Letters, http: //dx.doi.org/10.1016/j.matlet.2014.12.055 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Facile synthesis of core/shell-structured Sn/onion-like carbon nanocapsules as high-performance anode material for lithium-ion batteries Caiyun Cuia, Xianguo Liua,*, Niandu Wua, Yuping Sunb a
School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, PR
China. b
Center for Engineering practice and Innovation Education, Anhui University of Technology, Maanshan
243032, PR China.
Abstract Core/shell-structured Sn/C nanocapsules with Sn nanoparticles as the core and defective onion-like carbon as the shell are synthesized by a modified arc-discharge method. The Sn/C nanocapsule anode maintains a high discharge capacity of 585 mAh g-1 after 100 cycles at 0.1 A g-1 and obtains a high reversible capacity of ~ 480 mAh g-1 at 5 A g-1. The remarkable electrochemical performance is attributed to the effective combination of the Sn nanoparticle cores and the defective onion-like carbon shells, which simultaneously solves the major problems of pulverization, loss of electrical contact, and particle aggregation encountered in Sn anode.
Keywords: Core-shell; Sn; Carbon materials; Nanocomposites; Anode; Lithium-ion batteries
*Corresponding author Address: School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, PR China. Tel/Fax: +86-555-2311570 E-mail address: [email protected] 1
1. Introduction Rechargeable lithium-ion batteries (LIBs), as the most important type of power sources for portable electronic devices, are being actively considered as battery power systems for electric and hybrid vehicles [1-8]. To improve the energy density, cycling stability, and rate capacity of such battery power systems, a great deal of efforts has been put on enhancing electrode performance. Tin (Sn) has received enormous research interest as a potential substitute for carbon anode because of its higher theoretical capacity (993 mAh g-1) than the traditional carbon anode (372 mAh g-1) [2]. However, practical applications of Sn anode is impeded by the large volume change of about 259% during the alloying/dealloying [1-5]. Therefore, it is urgently needed to modify Sn anode with enhanced structural stability for prolonged cycle life. Designing uniquely nanostructured Sn anode such as 0D nanoparticles [1,2,8], 1D nanorods/nanowires [3, 4], 2D nanosheets [5], and 3D porous nanostructures [6], is one of the effective ways to withstand the huge volume change during the charge-discharge process. Another way is to introduce carbon materials into Sn anode [7,8]. Recently, Sn nanoparticles self-inserted between graphene interlayers, Sn nanoparticles encapsulated in spherical hollow carbon and Sn nanoparticles dispersed in a carbon matrix have been reported as anode materials for LIBs [2]. Among Sn/C nanocomposites, core/shell structured nanocapsules with Sn nanoparticles as the core and onion-like carbon as the shell are of particular interest due to the improved strain accommodation capability and thus the enhanced structural stability. For examples, NiO/C, Co3O4/C, and CuO/C nanocapsules all exhibit markedly enhanced lithium storage performance by virtue of their structural characteristics [9-11]. In this paper, we report the synthesis and electrochemical properties of Sn/C nanocapsules with Sn nanoparticles as the core and defective onion-like carbon as the shell. The obtained Sn/C
2
nanocapsules exhibit excellent cycling stability and rate performance in LIBs. 2.
Experiment The Sn/C nanocapsules were synthesized by an arc-discharge method in accordance with the
report in Ref [12]. Bulk Sn was used as the anode, while the cathode was a graphite needle. After the chamber was evacuated in a vacuum of 6.6×10-3 Pa, liquid ethanol of 50 mL was introduced into the chamber together with pure argon of 1.2 ×104 Pa. During the present arc-discharge process, the arc was shot at a joint near the Sn and the current was maintained at 50 A for 15 min. After being passviated in argon for 12 h, the Sn/C nanocapsules were collected on the top of the chamber. The phase analysis for the product was performed by using a powder X-ray diffraction (XRD) technique, acquired by a Bruker D8 Advance X-ray diffractometer. The morphology and size distribution of the products were observed by a high-resolution transmission electron microscope (HRTEM) images from JEOL-2100F. The electrodes for the electrochemical characterization were fabricated by mixing
Sn/C
nanocapsules, acetylene black as a conducting agent, and polyvinylidene difluoride (70:15:15 by weight) dissolved in N-methyl-2-pyrrolidone as a binder to form a slurry, followed by coating on copper foil as well as pressing and drying in a vacuum baking oven at 120 oC for 3 h. The coin-type cells (CR2016) were assembled in an argon-filled glove box. Celgard 2325 was used as the separator. Pure lithium disks were used as the counter and reference electrodes. The electrolyte was 1 M LiPF6 in ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (1:1:1 by volume). Cyclic voltammograms (CV) were recorded using the PAR2273 Electrochemical Measurement System (EG&G Princeton Applied Research), and the cells were cycled by Land 2001A with a scan rate of 0.1 mV s-1 at room temperature.
3
3.
Results and Discussion
Fig. 1 XRD pattern of Sn/C nanocapsules.
The XRD pattern for the Sn/C nanocapsules is given in Fig. 1. It is clearly seen that all peaks can be well-indexed to Sn (JCPDS No. 04-0673). There are no Sn-oxide peaks detectable in the XRD patterns, indicating that the products may be free from surface oxidation. It should be noted that there are no evidences of carbon, suggesting its small amount (less than 3% in the products), if any [9-11]. Carbon atoms are usually favorable to form the shell of nanoparticles in an onion-like structure and can protect it from oxidization.
Fig. 2 (a) TEM and (b) HRTEM images of Sn/C nanocapsules.
The TEM image in Fig. 2(a) shows a group of spherical Sn/C nanocapsules with a diameter 4
distribution of 5-30 nm. From Fig. 2(a), hollow structure is seen between the Sn nanoparticles and the onion-like carbon shell, and this hollow structure can accommodate the volume change of the Sn nanoparticles during the charge-discharge cycling. The HRTEM image in Fig. 2(b) indicates that the nanoparticle core is well-coated by the onion-like C shell with a thickness of about 1.85 nm. In the Sn nanoparticle core, the d-spacing is found to be 0.202 nm, corresponding to the {211} of Sn. The lattice plane spacing of the coating layers is about 0.34 nm, corresponding to the (002) of graphite. Nevertheless, a mass of lattice imperfections can be seen in the outer shells as a consequence of the serious bending and collapsing of the graphite atom layer.
Fig. 3. Electrochemical properties of as-prepared Sn/C nanocapsules. (a) CV curves at a rate of 0.1 mV s-1, (b) charge/discharge profiles at different cycles with a current density of 100 mA g-1, (c) cycling performance and Coulombic efficiency at a current density of 100 mA g-1, and (d) rate performance.
The Sn/C nanocapsules are used as anode material for LIBs to study the electrochemical properties. To understand the Li-ion insertion and extraction process in the nanocapsules during the discharge/charge cycling, CV was measured between 0.005 V and 2.0 V vs Li/Li+ at a scan rate of 0.1 5
mVs-1. During the first cathodic sweep, a reduction peak locates at 0.59 V and the several anodic peaks are related to the deintercalation of lithium from the cathode materials for the first time [13]. In the subsequent sweeps, two reduction peaks are observed at 0.30 and 0.57 V, which are mainly due to the alloying of lithium with Sn for the formation of different types of Li-Sn alloys, while the oxidation peaks at 0.70 and 0.79 V are associated with the reversible delithiation process of lithium from different types of LixSn alloys and the background is related to Li+ extraction form carbon shells [12]. Except for the first one, all CV cycles overlap well, indicating a good capacity retention after the first cycle. Fig. 3(b) shows the charge/discharge voltage curves for the 1st, 5th, 10th, and 20th cycles of the Sn/C/Li cell with a current densities of 100 mA g-1 (0.2 C). It is clearly demonstrated that the first discharge and charge capacities are 1012.0 and 622.1 mAh g-1 of the Sn/C nanocapsule anode with a low coulombic efficiency of 61.5%. Such large initial irreversible loss is generally related to the decomposition of electrolyte, the formation of a SEI layer on the anode surface, and the storage of Li+ in onion-like carbon nanoshell [14]. Comparing to the theoretical capacity of Sn (992 mAh g-1) and also graphite (372 mAh g-1), the extra discharge capacity of our Sn/C nanocapsules is mainly caused by the decomposition of the electrolyte with the SEI formation [6]. The subsequent discharge curve differs considerably from the first cycle because of the formation of the dense SEI film on the surface of the anodes in the first discharge cycle [13]. Despite the large initial loss, our Sn/C nanocapsule anode exhibits very stable cycling performance under such testing conditions (Fig. 3(c)). The discharge capacity also reaches 585 mAh g-1 after 100 cycles, which is still higher than 372 mAh g-1 of graphite. The efficiency increases to above 96 % after the 5th cycle. The rate performance of Sn/C nanocapsules at different current densities is shown in Fig. 3(d).
6
The specific reversible capacity falls moderately with increasing current density from a value of about 620 mAh g-1 at 0.1 A g-1 to about 520 mAh g-1 at 2 A g-1. Even at a higher current density of 5 A g-1, the capacity of ~ 480 mAh g-1 is still higher than the practical capacity of graphite. At each current density, the capacity is fairly stable. The superior rate capability of our Sn/C nanocapsules can be explained by the combination of the electric conductivity from the onion-like carbon nanoshell and the short diffusion path for both electrons and ions provided by the Sn nanoparticles and the defective carbon nanoshells. When decreasing the current desnisty from 5A g-1 to 0.1 A g-1, about 97.6 % of the initial reversible capacity at 0.1 A g-1 is recovered, indicating that the core/shell structure of our Sn/C nanocapsules could preserve the integrity of the electrode and thus could be tolerant to variations in charge and discharge currents [15]. 4. Conclusion A facile and practical synthesis route has been developed to synthesize Sn/C nanocapsules. As the anode of LIBs, the Sn/C nanocapsules with the combination of Sn nanoparticle core and the defective onion-like carbon nanoshells have demonstrated improved cycling stability and rate capability. The discharge capacity has reached a high value of about 585 mAh g-1 after 100 cycles. At an elevated current density of 5 A g-1, a high reversible capacity of about 480 mAh g-1 has been obtained. The arc-discharge method makes Sn/C nancapsules very promising as an anode material for LIBs. Acknowledgments This study was supported by the National Natural Science Foundation of China (No. 51201002).
7
References [1] Nobili F, Meschini I, Mancini M, Tossici R, Croce F. Electrochim Acta 2013;107 85-92. [2] Xu YH, Liu Q, Zhu YJ, Liu YH, Wang CS. Nano Lett 2013; 13: 470-4. [3] Hsu KC, Liu CE, Chen PC, Chiu HT. J Mater Chem 2012; 22: 21533-9. [4] Ni W, Wang YB, Xu R. Part Part Syst Charact 2013; 30: 873-80. [5] Zhou XY, Zou YL, Yang J. J Power Sources 2014; 253: 287-93. [6] Wang G, Ma YQ, Liu ZY, Wu JN. Electrochim Acta 2012; 65: 275-9. [7] Lu ZZ, Wang HK. CrystEngComm 2014; 16: 550-5. [8] Wang CD, Li Y, Chui YS, Wu QH, Chen XF, Zhang WJ. Nanoscale 2013; 5: 10599-604. [9] Liu XG, Or SW, Jin CG, Lv YH, Sun YP. Carbon 2013; 60: 215-20. [10] Liu XG, Or SW, Jin CG, Lv YH, Sun YP. Electrochim Acta 2013; 100: 140-6. [11] Liu XG, Bi NN, Or SW, Sun YP. J Alloys Compd 2014; 587: 1-5. [12] Wang ZH, Han Z, Geng DY, Zhang ZD. Chem Phys Lett 2010; 489: 187-90. [13] Tao XY, Wu R, Xia Y, Huang H, Chai WC, Zhang WK. ACS Appl Mater Interfaces 2014; 4: 3696-702. [14] Yu Y, Gu L,Wang CL, Dhanabalan A, Maier J. Ange Chem Inter Ed 2009; 17: 6485-9. [15] Zhu ZQ, Wang SW, Du J, Jin Q, Zhang TR, Chen J. Nano Lett 2014; 14: 153-7.
8
HIGHLIGHTS
Sn@C core-shell nanocapsules have been prepared. Sn@C nanocapsules obtain a discharge capacity of 585 mAh g-1 after 100 cycles at 0.1 A g-1. The core-shell structure leads to the remarkable electrochemical performances.
Graphical Abstract
9