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Carbon nanosheet frameworks derived from sodium alginate as anode materials for sodium-ion batteries
Author’s Accepted Manuscript Carbon nanosheet frameworks derived from sodium alginate as anode materials for sodium-ion batteries Hailing Hu, Liyuan Cao, Zhanwei Xu, Lei Zhou, Jiayin Li, Jianfeng Huang www.elsevier.com
PII: DOI: Reference:
S0167-577X(16)31404-5 http://dx.doi.org/10.1016/j.matlet.2016.08.110 MLBLUE21394
To appear in: Materials Letters Received date: 1 July 2016 Revised date: 12 August 2016 Accepted date: 22 August 2016 Cite this article as: Hailing Hu, Liyuan Cao, Zhanwei Xu, Lei Zhou, Jiayin Li and Jianfeng Huang, Carbon nanosheet frameworks derived from sodium alginate as anode materials for sodium-ion batteries, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.08.110 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.
Carbon nanosheet frameworks derived from sodium alginate as anode materials for sodium-ion batteries Hailing Hu, Liyuan Cao*, Zhanwei Xu, Lei Zhou, Jiayin Li, Jianfeng Huang* School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021, China [email protected] [email protected]
Abstract Hard carbon materials are considered as one of the most promising anodes for sodium-ion batteries (SIBs). Here, the carbon nanosheet frameworks (CNFs) derived from sodium alginate without activation or any further treatments. CNFs have large cavities, thin walls and large interlayer distance (0.39 nm), resulting in a high reversible sodium storage capacity (216 mA h g-1 at 100 mA g-1) and a good cycle stability (160 mA h g-1 at 100 mA g-1 over 340 cycles) in SIBs. Meanwhile, CNFs show excellent rate capability (66 mA h g-1 at 5000 mA g-1). The high capacity, excellent cycle performance combined with facile synthesis procedure make CNFs to be a promising anode material for practical SIBs. Graphical abstract
1
The carbon nanosheet frameworks (CNFs) derived from sodium alginate without activation or any further treatments. The open nanosheet frameworks can accelerate the charge-transfer reaction on a large electrode/electrolytes interface and provide the short diffusion path. Thus, the CNFs exhibit promising electrochemical properties.
Keywords: Carbon materials, Sodium alginate, Nanosheet frameworks, Electrical properties, Sodium-ion batteries
1. Introduction Lithium-ion batteries (LIBs) have dominated the current rechargeable battery market owing to their excellent electrochemical performance and environmental friendliness [1]. However, LIBs are not very suitable for large-scale electrical energy storage because of their relatively high cost and limited terrestrial reserves of lithium [2]. Because of the relatively low cost, abundant sodium resources and similar
2
electrochemical properties between sodium and lithium, sodium-ion batteries (SIBs) have recently attracted tremendous attentions as a promising alternative to LIBs in the field of large-scale electrical energy storage [3]. Nowadays, carbon is recognized as one of the promising electrode materials for energy storage systems, respecting to their unique electrochemistry functions and low cost [4]. It is well acknowledged that the most-used graphite anode material in commercial LIBs shows poor electrochemical performance (the reversible capacity less than 5 mA h g-1) in SIBs due to the graphene interlayer spacing that cannot accommodate the larger Na ions [5, 6]. A variety of carbon materials hard carbons [7], carbon nanotubes [8] and reduced graphene oxides [9] were investigated as anodes for SIBs. Hard carbon is considered as one of the most promising carbonaceous anode materials for SIBs because of its advantages of stability, relatively high capacity and easy to preparation. As the nanostructure and porous structure can provide some active sites for Na ion storage as well as decrease the diffusion distance of Na ion and enhance the rate capability [10-13]. Nanostructured morphology and porous structure are generally agreed to be effective ways to improve the electrochemical performance of hard carbon materials. However, nano or porous carbons are prepared through pyrolysis sucrose and polymers with complex treatments [14, 15], which prevent the application in SIBs for large-scale energy storage market. Herein, carbon nanosheet frameworks (CNFs) were synthesized by pyrolysis of sodium alginate (SA) at 800 °C under vacuum without activation or any further treatments. The CNFs show very high reversible sodium storage capacities up to 216 mA h g-1. They also exhibit superior cycling stability with only 7.6 % capacity loss over 340 cycles at 100 mA g-1. The high capacity, excellent cycle performance,
3
combined with facile synthesis procedure make CNFs to be a promising anode material for practical SIBs. 2. Experimental The typical synthesis route of CNFs is given as follows: Firstly, SA ((C6H7O6Na)n, Sinopharn Chemical Reagent Co., Ltd ) was dissolved in 100 mL deionized water with magnetic stirring and heating at 80 ◦C for 1 h, then a viscous-yellow solution was obtained after further drying by vacuum freeze-dying for 48 h. Secondly, the obtained yellow gelatinous substance was carbonized at 800 ◦C for 2 h under vacuum. After that the carbonized products was added to 100 ml 2 mol L-1 HCl with a later stirred at 400 r min-1 for 2 h. Finally, the obtained products were washed with deionized water and ethanol alternatively for several times, and dried in an oven at 80 ◦C for 12 h. The obtained of CNFs were characterized by X-ray diffraction (XRD, D/max2200PC, Rigaku, Japan) and Raman spectroscopy (RAMAN, Renishaw-invia, Britain). The morphology of CNFs were observed by scanning electron microscope (SEM, S-4800, Hitachi, Japan) and transmission electron microscopy (TEM, JEM-3010). Electrochemical measurements were performed using CR2032 coin-type cells. The working electrodes were fabricated by spreading the mixed slurry of the active materials, acetylene black and polyvinylidene fluoride binder in a solvent of N-methyl-2-pyrrolidone with a weight ratio of 80:10:10 onto copper foil, and then drying at 80 ◦C in a vacuum for 12 h. The typical loading amount of active material was 2-2.5 mg cm-2. Sodium pellet was used as a counter electrode. The electrolyte was a solution of 1M NaClO4in a mixture of ethylene carbonate and diethyl carbonate (EC: DEC = 1:1). The cells were charged and discharged using a Neware battery tester (Neware, Shenzhen) with a potential range of 0.01-3.00 V. Cyclic voltammetry (CV) measurements spectroscopy was performed by a CHI660E
4
electrochemical station (Shanghai Chenhua, China). All tests were performed at 20 ◦C. 3. Results and discussion
Fig 1. (a) XRD pattern and (b) Raman Spectra of CNFs. Fig. 1 shows the XRD pattern of CNFs. Two broad diffraction peaks appeared at ~ 24o and ~44.5o, corresponding to the (002) and (101) planes of graphite, confirming that the obtained carbon materials were amorphous carbons. From the 2θ degree of (002) peak, the interlayer distance of graphitic layers was calculated to be 0.39 nm, which was obviously larger than that of graphite (0.335 nm) [8]. The large interlayer distance of CFNs can facilitate the reversible storage and transport of larger sodium ion [9]. Fig. 1b depicts the Raman spectroscopy of CNFs. It presented two characteristic bands of the disorder-induced D-band peak at 1355 cm-1 and in-plane vibrational G band peak at 1590 cm-1 [10]. The intensity ratio of the D-band over the G-band was 0.93, which verified that the CNFs were disordered and amorphous carbons.
5
Fig 2. SEM images of CNFs (a) low magnification and (b) higher magnification; (c) TEM and (d) HRTEM micrographs of CNFs. As seen from SEM in Fig 2.a and b, the carbon with 3D nanosheet frameworks morphology and the thickness of the nanosheets can be estimated in the range of 10 to 20 nm. The nanosheet frameworks had large cavities and thin walls, which permited the organic electrolyte to enter the material and shortened the path of the sodium ions and electrons, beneficial for enhancing the performance of the material [10-13]. Forming such interesting nanosheet frameworks may be related to organic molecules emitting gases in pyrolysis as well as Na activation, and the mechanism of Na activation was similar to the KOH activation [16]. Fig. 2c shows a typical thin film like fold, indicating the sparing restacking of graphene layers in CNFs. The lattice spacing of the (002) crystal planes was estimated to be 0.39 nm from the HRTEM of CNFs (Fig. 2d), corresponding to the result of XRD.
Fig 3. Electrochemical performance of CNFs: (a) CV curves at a scan rate of 0.5 mv s-1; (b) charge / discharge profiles at 100 mA g-1; (c) cyclability at 100 mA g-1; (d) capacity over cycling at different rates. Fig. 3a shows the CV curves of CNFs at a scanning rate of 0.5 mV s-1 in the range of 0.01 - 3 V.
6
During the first scan, a broad reduction peak appeared in region from 0.89 V to 1.5 V, which related to irreversible reaction of the electrolyte with surface functional groups. Another irreversible peak at 0.46 V was ascribed to the formation of a solid electrolyte interphase (SEI) and irreversible insertion of Na ion in to carbon structure. Those irreversible reactions led to the integral area of the first scan much larger than the subsequent scans. Fig.3b shows the charge/discharge profiles of CNFs electrode at a constant current density of 100 mA g-1. The initial discharge curve had a sloping plateau between 0.89 V to 1.5 V, which was accordant with the first CV curve. In the first cycle, the electrode delivered the specific discharge and charge capacities of 554.3 and 216.9 mA h g-1, corresponding to an initial coulombic efficiency of 37%. The low coulombic efficiency was caused by the formation of SEI, the irreversible Na adsorption at graphene defect sites and irreversible Na intercalation between the graphene layers. Furthermore, the CNFs showed very impressive cycling performance, as shown in Fig. 3c. When cycling at 100 mA g-1, the electrode exhibited a stable capacity of 160 mA h g-1 over cycle 340 with coulombic efficiency of~100% after first few cycles. More importantly, the CNFs also exhibited a great rate capability, which was another critical property for practical application in SIBs and was required for fast discharging/charging (Fig. 3d). While cycling at different current densities of 100, 200, 500, 1000 and 5000 mA g-1, capacities of 200.5, 140.9, 122.6, 100.3 and 66 mA h g-1 can still be delivered. When the current density was back to100 mA g-1, the capacity recovered to 179 mA h g-1. In order to further confirm the electrochemical performance of CNFs, some relevant information are summarized in Table S1. It is found that the as-prepared show good cycling stability and excellent rate capability. The good electrochemical performance of CNF was mainly due to large interlayer spacing and the nanosheet frameworks structural. The large interlayer distance accelerates the intercalation of sodium ions
7
fast transport and high sodium storage in the electrode. Furthermore, the nanosheet frameworks facilitate the efficient ion transportation by shortening the transport length. Thus, CNFs can synergistically enhance the reversible sodium storage capacity, cycle stability and rate capacity. 4. Conclusions CNFs were obtained from SA by facile pyrolysis without activation or any further treatments. The unique structural feature endowed CNFs with a high initial capacity (216 mA h g-1 at 100 mA g-1), good cycling stability (160 mA h g-1 at 100 mA g-1 over 340 cycles), and excellent rate capability (66 mA h g-1 at 5000 mA g-1). Moreover, the easy synthesis, sustainable resource, destitute activator and the high electrochemical performance make CNF to be a promising anode material for SIBs. Acknowledgements This work was supported by the National Natural Science Foundation of China (No. 51102196), the science and technology project of the young star of Shaanxi Province (2014KJXX-68), the Innovation Team Assistance Foundation of Shaanxi Province (2013KCT-06) and the scientific research project of Shaanxi education department (14Jk1104). Their supports are gratefully acknowledged.
References [1] Tang J., Yang J., Zhou X., et al. Materials Letters, 2013, 109(10):253-256. [2] Nykvist B., Nilsson M. Nature Climate Change, 2016, 5(4):329-332. [3] Slater M. D., Kim D., Lee E., et al. Advanced Functional Materials 23(8):947-958. [4] Pan H., Hu Y. S., Chen L. Energy & Environmental Science, 2013, 6(8):2338-2360. [5] Wang H., Yu W., Jing S., et al. Electrochimica Acta, 2016, 188:103-110.
8
[6] Palomares V., Serras P., Villaluenga I., et al. Energy & Environmental Science, 2012, 5(3):5884-5901. [7] Xiao L., Cao Y., Henderson W. A., et al. Nano Energy, 2016, 19:279–288. [8] Luo W., Schardt J., Bommier C., et al. Journal of Materials Chemistry A, 2013, 1(36):10662-10666. [9] Yan D., Xu X., Lu T., et al. Journal of Power Sources, 2016, 316:132-138. [10] Ding J., Wang H., Li Z., et al. ACS Nano, 2013, 7(12):11004-11015. [11] Jianhua H., Chuanbao C., Faryal I., et al. ACS Nano, 2015, 9(3):2556-64. [12] Ning S., Huan L., and Bin Xu. Journal of Materials Chemistry A, 2015, 3(41):20560-2056. [13] He Z., Faqi Y., Wenpei K. et al. Carbon, 2015, 95:354–363.1063-1072. [14] Wenzel S., Hara T., Janek J., et al. Energy & Environmental Science, 2011, 4(9):3342-3345. [15] Hong K., Long Q., Zeng R., et al. Journal of Materials Chemistry A, 2014, 2(32):12733-12738. [16] Wang J., Kaskel S. Journal of Materials Chemistry, 2012, 22(45):23710-23725.
Highlights
Carbon nanosheet frameworks (CNFs) are prepared by pyrolysis of sodium alginate.
As-synthesized CNFs have a large interlayer distance about 0.39nm.
The obtained CNFs exhibit an excellent electrochemical performance.
9
PII: DOI: Reference:
S0167-577X(16)31404-5 http://dx.doi.org/10.1016/j.matlet.2016.08.110 MLBLUE21394
To appear in: Materials Letters Received date: 1 July 2016 Revised date: 12 August 2016 Accepted date: 22 August 2016 Cite this article as: Hailing Hu, Liyuan Cao, Zhanwei Xu, Lei Zhou, Jiayin Li and Jianfeng Huang, Carbon nanosheet frameworks derived from sodium alginate as anode materials for sodium-ion batteries, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.08.110 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.
Carbon nanosheet frameworks derived from sodium alginate as anode materials for sodium-ion batteries Hailing Hu, Liyuan Cao*, Zhanwei Xu, Lei Zhou, Jiayin Li, Jianfeng Huang* School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021, China [email protected] [email protected]
Abstract Hard carbon materials are considered as one of the most promising anodes for sodium-ion batteries (SIBs). Here, the carbon nanosheet frameworks (CNFs) derived from sodium alginate without activation or any further treatments. CNFs have large cavities, thin walls and large interlayer distance (0.39 nm), resulting in a high reversible sodium storage capacity (216 mA h g-1 at 100 mA g-1) and a good cycle stability (160 mA h g-1 at 100 mA g-1 over 340 cycles) in SIBs. Meanwhile, CNFs show excellent rate capability (66 mA h g-1 at 5000 mA g-1). The high capacity, excellent cycle performance combined with facile synthesis procedure make CNFs to be a promising anode material for practical SIBs. Graphical abstract
1
The carbon nanosheet frameworks (CNFs) derived from sodium alginate without activation or any further treatments. The open nanosheet frameworks can accelerate the charge-transfer reaction on a large electrode/electrolytes interface and provide the short diffusion path. Thus, the CNFs exhibit promising electrochemical properties.
Keywords: Carbon materials, Sodium alginate, Nanosheet frameworks, Electrical properties, Sodium-ion batteries
1. Introduction Lithium-ion batteries (LIBs) have dominated the current rechargeable battery market owing to their excellent electrochemical performance and environmental friendliness [1]. However, LIBs are not very suitable for large-scale electrical energy storage because of their relatively high cost and limited terrestrial reserves of lithium [2]. Because of the relatively low cost, abundant sodium resources and similar
2
electrochemical properties between sodium and lithium, sodium-ion batteries (SIBs) have recently attracted tremendous attentions as a promising alternative to LIBs in the field of large-scale electrical energy storage [3]. Nowadays, carbon is recognized as one of the promising electrode materials for energy storage systems, respecting to their unique electrochemistry functions and low cost [4]. It is well acknowledged that the most-used graphite anode material in commercial LIBs shows poor electrochemical performance (the reversible capacity less than 5 mA h g-1) in SIBs due to the graphene interlayer spacing that cannot accommodate the larger Na ions [5, 6]. A variety of carbon materials hard carbons [7], carbon nanotubes [8] and reduced graphene oxides [9] were investigated as anodes for SIBs. Hard carbon is considered as one of the most promising carbonaceous anode materials for SIBs because of its advantages of stability, relatively high capacity and easy to preparation. As the nanostructure and porous structure can provide some active sites for Na ion storage as well as decrease the diffusion distance of Na ion and enhance the rate capability [10-13]. Nanostructured morphology and porous structure are generally agreed to be effective ways to improve the electrochemical performance of hard carbon materials. However, nano or porous carbons are prepared through pyrolysis sucrose and polymers with complex treatments [14, 15], which prevent the application in SIBs for large-scale energy storage market. Herein, carbon nanosheet frameworks (CNFs) were synthesized by pyrolysis of sodium alginate (SA) at 800 °C under vacuum without activation or any further treatments. The CNFs show very high reversible sodium storage capacities up to 216 mA h g-1. They also exhibit superior cycling stability with only 7.6 % capacity loss over 340 cycles at 100 mA g-1. The high capacity, excellent cycle performance,
3
combined with facile synthesis procedure make CNFs to be a promising anode material for practical SIBs. 2. Experimental The typical synthesis route of CNFs is given as follows: Firstly, SA ((C6H7O6Na)n, Sinopharn Chemical Reagent Co., Ltd ) was dissolved in 100 mL deionized water with magnetic stirring and heating at 80 ◦C for 1 h, then a viscous-yellow solution was obtained after further drying by vacuum freeze-dying for 48 h. Secondly, the obtained yellow gelatinous substance was carbonized at 800 ◦C for 2 h under vacuum. After that the carbonized products was added to 100 ml 2 mol L-1 HCl with a later stirred at 400 r min-1 for 2 h. Finally, the obtained products were washed with deionized water and ethanol alternatively for several times, and dried in an oven at 80 ◦C for 12 h. The obtained of CNFs were characterized by X-ray diffraction (XRD, D/max2200PC, Rigaku, Japan) and Raman spectroscopy (RAMAN, Renishaw-invia, Britain). The morphology of CNFs were observed by scanning electron microscope (SEM, S-4800, Hitachi, Japan) and transmission electron microscopy (TEM, JEM-3010). Electrochemical measurements were performed using CR2032 coin-type cells. The working electrodes were fabricated by spreading the mixed slurry of the active materials, acetylene black and polyvinylidene fluoride binder in a solvent of N-methyl-2-pyrrolidone with a weight ratio of 80:10:10 onto copper foil, and then drying at 80 ◦C in a vacuum for 12 h. The typical loading amount of active material was 2-2.5 mg cm-2. Sodium pellet was used as a counter electrode. The electrolyte was a solution of 1M NaClO4in a mixture of ethylene carbonate and diethyl carbonate (EC: DEC = 1:1). The cells were charged and discharged using a Neware battery tester (Neware, Shenzhen) with a potential range of 0.01-3.00 V. Cyclic voltammetry (CV) measurements spectroscopy was performed by a CHI660E
4
electrochemical station (Shanghai Chenhua, China). All tests were performed at 20 ◦C. 3. Results and discussion
Fig 1. (a) XRD pattern and (b) Raman Spectra of CNFs. Fig. 1 shows the XRD pattern of CNFs. Two broad diffraction peaks appeared at ~ 24o and ~44.5o, corresponding to the (002) and (101) planes of graphite, confirming that the obtained carbon materials were amorphous carbons. From the 2θ degree of (002) peak, the interlayer distance of graphitic layers was calculated to be 0.39 nm, which was obviously larger than that of graphite (0.335 nm) [8]. The large interlayer distance of CFNs can facilitate the reversible storage and transport of larger sodium ion [9]. Fig. 1b depicts the Raman spectroscopy of CNFs. It presented two characteristic bands of the disorder-induced D-band peak at 1355 cm-1 and in-plane vibrational G band peak at 1590 cm-1 [10]. The intensity ratio of the D-band over the G-band was 0.93, which verified that the CNFs were disordered and amorphous carbons.
5
Fig 2. SEM images of CNFs (a) low magnification and (b) higher magnification; (c) TEM and (d) HRTEM micrographs of CNFs. As seen from SEM in Fig 2.a and b, the carbon with 3D nanosheet frameworks morphology and the thickness of the nanosheets can be estimated in the range of 10 to 20 nm. The nanosheet frameworks had large cavities and thin walls, which permited the organic electrolyte to enter the material and shortened the path of the sodium ions and electrons, beneficial for enhancing the performance of the material [10-13]. Forming such interesting nanosheet frameworks may be related to organic molecules emitting gases in pyrolysis as well as Na activation, and the mechanism of Na activation was similar to the KOH activation [16]. Fig. 2c shows a typical thin film like fold, indicating the sparing restacking of graphene layers in CNFs. The lattice spacing of the (002) crystal planes was estimated to be 0.39 nm from the HRTEM of CNFs (Fig. 2d), corresponding to the result of XRD.
Fig 3. Electrochemical performance of CNFs: (a) CV curves at a scan rate of 0.5 mv s-1; (b) charge / discharge profiles at 100 mA g-1; (c) cyclability at 100 mA g-1; (d) capacity over cycling at different rates. Fig. 3a shows the CV curves of CNFs at a scanning rate of 0.5 mV s-1 in the range of 0.01 - 3 V.
6
During the first scan, a broad reduction peak appeared in region from 0.89 V to 1.5 V, which related to irreversible reaction of the electrolyte with surface functional groups. Another irreversible peak at 0.46 V was ascribed to the formation of a solid electrolyte interphase (SEI) and irreversible insertion of Na ion in to carbon structure. Those irreversible reactions led to the integral area of the first scan much larger than the subsequent scans. Fig.3b shows the charge/discharge profiles of CNFs electrode at a constant current density of 100 mA g-1. The initial discharge curve had a sloping plateau between 0.89 V to 1.5 V, which was accordant with the first CV curve. In the first cycle, the electrode delivered the specific discharge and charge capacities of 554.3 and 216.9 mA h g-1, corresponding to an initial coulombic efficiency of 37%. The low coulombic efficiency was caused by the formation of SEI, the irreversible Na adsorption at graphene defect sites and irreversible Na intercalation between the graphene layers. Furthermore, the CNFs showed very impressive cycling performance, as shown in Fig. 3c. When cycling at 100 mA g-1, the electrode exhibited a stable capacity of 160 mA h g-1 over cycle 340 with coulombic efficiency of~100% after first few cycles. More importantly, the CNFs also exhibited a great rate capability, which was another critical property for practical application in SIBs and was required for fast discharging/charging (Fig. 3d). While cycling at different current densities of 100, 200, 500, 1000 and 5000 mA g-1, capacities of 200.5, 140.9, 122.6, 100.3 and 66 mA h g-1 can still be delivered. When the current density was back to100 mA g-1, the capacity recovered to 179 mA h g-1. In order to further confirm the electrochemical performance of CNFs, some relevant information are summarized in Table S1. It is found that the as-prepared show good cycling stability and excellent rate capability. The good electrochemical performance of CNF was mainly due to large interlayer spacing and the nanosheet frameworks structural. The large interlayer distance accelerates the intercalation of sodium ions
7
fast transport and high sodium storage in the electrode. Furthermore, the nanosheet frameworks facilitate the efficient ion transportation by shortening the transport length. Thus, CNFs can synergistically enhance the reversible sodium storage capacity, cycle stability and rate capacity. 4. Conclusions CNFs were obtained from SA by facile pyrolysis without activation or any further treatments. The unique structural feature endowed CNFs with a high initial capacity (216 mA h g-1 at 100 mA g-1), good cycling stability (160 mA h g-1 at 100 mA g-1 over 340 cycles), and excellent rate capability (66 mA h g-1 at 5000 mA g-1). Moreover, the easy synthesis, sustainable resource, destitute activator and the high electrochemical performance make CNF to be a promising anode material for SIBs. Acknowledgements This work was supported by the National Natural Science Foundation of China (No. 51102196), the science and technology project of the young star of Shaanxi Province (2014KJXX-68), the Innovation Team Assistance Foundation of Shaanxi Province (2013KCT-06) and the scientific research project of Shaanxi education department (14Jk1104). Their supports are gratefully acknowledged.
References [1] Tang J., Yang J., Zhou X., et al. Materials Letters, 2013, 109(10):253-256. [2] Nykvist B., Nilsson M. Nature Climate Change, 2016, 5(4):329-332. [3] Slater M. D., Kim D., Lee E., et al. Advanced Functional Materials 23(8):947-958. [4] Pan H., Hu Y. S., Chen L. Energy & Environmental Science, 2013, 6(8):2338-2360. [5] Wang H., Yu W., Jing S., et al. Electrochimica Acta, 2016, 188:103-110.
8
[6] Palomares V., Serras P., Villaluenga I., et al. Energy & Environmental Science, 2012, 5(3):5884-5901. [7] Xiao L., Cao Y., Henderson W. A., et al. Nano Energy, 2016, 19:279–288. [8] Luo W., Schardt J., Bommier C., et al. Journal of Materials Chemistry A, 2013, 1(36):10662-10666. [9] Yan D., Xu X., Lu T., et al. Journal of Power Sources, 2016, 316:132-138. [10] Ding J., Wang H., Li Z., et al. ACS Nano, 2013, 7(12):11004-11015. [11] Jianhua H., Chuanbao C., Faryal I., et al. ACS Nano, 2015, 9(3):2556-64. [12] Ning S., Huan L., and Bin Xu. Journal of Materials Chemistry A, 2015, 3(41):20560-2056. [13] He Z., Faqi Y., Wenpei K. et al. Carbon, 2015, 95:354–363.1063-1072. [14] Wenzel S., Hara T., Janek J., et al. Energy & Environmental Science, 2011, 4(9):3342-3345. [15] Hong K., Long Q., Zeng R., et al. Journal of Materials Chemistry A, 2014, 2(32):12733-12738. [16] Wang J., Kaskel S. Journal of Materials Chemistry, 2012, 22(45):23710-23725.
Highlights
Carbon nanosheet frameworks (CNFs) are prepared by pyrolysis of sodium alginate.
As-synthesized CNFs have a large interlayer distance about 0.39nm.
The obtained CNFs exhibit an excellent electrochemical performance.
9