- Email: [email protected]
Biomorphic combustion synthesis of hematite porous structure with enhanced Li storage properties
Materials Letters 168 (2016) 107–110
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Biomorphic combustion synthesis of hematite porous structure with enhanced Li storage properties Q.Q. Xiong a,b,n, Z.G. Ji a, H.Y. Qin a a b
College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, People’s Republic of China State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310018, People’s Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 9 November 2015 Accepted 10 January 2016 Available online 11 January 2016
Uniform porous Fe2O3 nanostructure was prepared by a facile and effective biomorphic combustion synthesis. Porous Fe2O3 nanostructure is assembled by primary nanoparticles and lots of open pores between interconnected nanoparticles. As an anode material for the lithium-ion batteries (LIBs), the resultant porous Fe2O3 electrode shows high specific capacity and good cycle stability (891.8 mAh g 1 at 200 mA g 1 up to 150 cycles), as well as enhanced rate capability. The excellent electrochemical performance can be attributed to 3D porous structure with the short pathway for the diffusion of Li þ , high interfacial contact area between the nanoparticles and electrolyte, and good accommodation of structural stress. & 2016 Elsevier B.V. All rights reserved.
Keywords: Hematite Nanoparticles Porous materials Combustion synthesis Lithium-ion battery
1. Introduction Recently, 3d transition metal oxides have been widely investigated as promising anodes in the field of LIBs since they were firstly proposed by Tarascon et al. [1]. They possess much higher capacities (two or three times) than that of graphite, and smaller volume change during the charge-discharge process than that of alloy anodes, which will hopefully realize the wide application of LIBs in various fields such as electric vehicles, military, and the like [2–4]. Among them, iron oxide, such as hematite (α-Fe2O3), has gained much attention due to its high theoretic capacity (1007 mAh g 1), non-toxicity, natural abundance, and low cost. Despite its many advantages, Fe2O3 suffers from low electrical conductivity, large volume expansion during the conversion reaction process, thus resulting in large irreversible loss, poor electrochemical performance and limiting its wide practical application [5]. These issues can partially overcome by developing different nanostructures, which is an effective strategy to ameliorate the electrochemical capability for their large surface area, the sufficient contact between active material and electrolyte, and the short Li ion diffusion path. In this work, we used a facile and high-efficiency biomorphic combustion synthesis to prepare porous Fe2O3 nanostructure with cotton as template. It should be noted that this synthetic process meets the demand of the green and sustainable modern industry n Corresponding author at: College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, People's Republic of China. E-mail address: [email protected] (Q.Q. Xiong).
http://dx.doi.org/10.1016/j.matlet.2016.01.047 0167-577X/& 2016 Elsevier B.V. All rights reserved.
and is more suitable for large-scale production. Compared to many other methods, this biomorphic combustion synthesis requires less complicated reactants and synthetic conditions, which are more attractive with respect to both cost and scalability. In the asprepared sample, the primary Fe2O3 nanoparticles form a secondary structure, resulting in an organized 3D porous nanostructure. While the small dimensions of the primary nanoparticles make ionic and electronic transport much easier, the secondary porous structure can well accommodate the strain associated with Li þ intercalation and the volume expansion of active materials. Thus, as the anode material for LIBs, the porous Fe2O3 nanostructure shows greatly enhanced electrochemical performance.
2. Experimental Porous Fe2O3 structure was synthesized via a cellulose combustion method. 40.4 g Fe(NO3)3 9H2O was dissolved in 100 mL of ethanol with stirring, into which clean cotton was soaked for 4 h. Then the wet cotton was directly put into a chamber furnace which was pre-heated to 500 °C in air, and treated at this temperature for 1 h to obtain the porous Fe2O3 structure. The morphology and microstructure of products were characterized using X-ray diffractometer (XRD, Rigaku D/max 2550 PC, Cu Kα), scanning electron microscope (SEM, Hitachi S-4700) and transmission electron microscope (TEM, JEM 200CX at 160 kV and Tecnai G2 F30 at 200 kV). The electrochemical measurements were performed using a coin-type half cell (CR 2025). The slurry consisted of 85 wt% Fe2O3, 10 wt% acetylene black and 5 wt% polyvinylidene fluoride (PVDF)
Q.Q. Xiong et al. / Materials Letters 168 (2016) 107–110
(d)
20
30
40
50
(214) (300)
(116)
(012)
Intensity (a.u.)
(c)
(b)
(018)
(a)
(024)
SEM, TEM and powder XRD were used to analyze the morphology and crystallinity of as-prepared porous Fe2O3 nanostructure. In Fig. 1a, the sample shows a 3D porous matrix rather than the morphology of the original cotton fibers, which is ascribed to the combustion method. Combustion synthesis involves an exothermic and self-sustaining chemical reaction, resulting in the collapse of the original fibrous structure of the cotton [6]. The relatively high-magnification SEM image is shown in Fig. 1b. Porous Fe2O3 nanostructure contains primary particles of about 100 nm in diameter, and these primary particles form a 3D porous matrix. The detailed morphological and structural features of the powder are also examined by TEM. Fig. 1c further confirms the 3D porous nanostructure. There are lots of open pores ranging from 20–100 nm between interconnected nanoparticles. The HRTEM image in the inset shows well-resolved atomic lattice fringes with
(113)
3. Results and discussion
adjacent lattice planes of 0.25 nm, which is in good agreement with the value of the (110) plane of rhombohedral Fe2O3. The crystal structure of sample is analyzed by XRD analysis in Fig. 1d. All the diffraction peaks confirm that the crystal structure is in agreement with the standard values for the rhombohedral phase of Fe2O3 [JCPDS Card no. 33-0664]. The Li storage capability of porous Fe2O3 nanostructure is fully characterized to demonstrate its potential use as anode for LIBs. The CV collected at a scan rate of 0.1 mV s 1 is shown in Fig. 2a. During the first discharge process, there is one large cathodic peak located at 0.71 V, along with a very small peak centered at 1.5 V. The small peak indicates the intercalation of Li into the crystal structure of the Fe2O3 nanostructure. The strong peak at 0.71 V can be attributed to the complete reduction of Fe3 þ to Fe0 and the irreversible decomposition reaction of electrolyte. During the anodic polarization process, two peaks are present at 1.63 and 1.84 V, corresponding to the oxidation of Fe0 to Fe2 þ and further oxidation to Fe3 þ . During the second cycle, the full lithiation voltage shifts to 0.92 V, which is higher than that in the first cycle (about 0.71 V). It is probably due to the reduced polarization of the porous Fe2O3 electrode resulting from a microstructural alteration after the first lithiation [7]. Fig. 2b shows typical discharge and charge voltage profiles of the first two cycles at 200 mA g 1. During first discharging process, a poorly defined plateau (1.2– 0.9 V) and a perfect one at about 0.85 V are observed, which are in agreement with the CV results. The two plateaus are followed by a continuous sloping curve down to the cut voltage of 0.01 V. The first discharge capacity of porous Fe2O3 electrode is 1195.5 mAh g 1, whereas the first charge capacity is
(104)
was pasted on copper foil. Test cells were assembled in an argonfilled glove box with the metallic lithium foil as both the reference and counter electrodes, 1 M LiPF6 in ethylene carbonate (EC)-dimethyl carbonate (DME) (1:1 in volume) as the electrolyte, and a polypropylene (PP) micro-porous film (Cellgard 2300) as the separator. The galvanostatic charge-discharge tests were conducted on LAND battery program-control test system in the voltage range of 0.01–3.0 V (versus Li/Li þ ) at room temperature (25 71 °C). Cyclic voltammetry (CV) was performed on CHI660C electrochemical workstation.
(110)
108
60
70
80
2 Theta degree Fig. 1. Morphology and crystallinity characterization of porous Fe2O3 nanoparticles: (a,b) SEM images; (c) TEM image, with HRTEM image (inset); (d) XRD pattern.
Q.Q. Xiong et al. / Materials Letters 168 (2016) 107–110
(a)
109
(b) 3.0
Potential(V vs. Li/Li
+
)
0.5
Current (A g
-1
)
0.0 -0.5 -1.0
1 st 2 nd
-1.5 -2.0 0.0
0.5
1.0
1.5
2.0
Potential (V vs. Li/Li
2.5
900
0.5 -1
600
75
100
125
0.0 150
Coulombic Efficiency -1 Capacity (mAh g )
) -1
Capacity (mAh g
1200
50
0.5
Discharge
0
200
400
600
800 1000 1200 1400
Capacity(mAh g
1.0
25
1.0
)
(d)
0
1 st 2 nd
1.5
+
1500
300
Charge
2.0
0.0
3.0
(c)
200 mA g
2.5
-1
)
1500 1200
200 mA g
900
1000 mA g 500 mA g
1500 mA g
600
1250 mA g 2000 mA g
300 0
0
5
Cycle Number
10
15
20
25
30
Cycle Number
Fig. 2. Electrochemical performance of porous Fe2O3 electrode: (a) CV curve for the first two cycles at a scan rate of 0.1 mV s 1 between 0.01 and 3.0 V; (b) charge/discharge profiles at the first two cycles at 200 mA g 1; (c) cycling performance at 200 mA g 1; (d) rate capability at different current densities ranging from 200 to 2000 mA g 1.
997.7 mAh g 1, resulting in an initial columbic efficiency of 83.5%. The extra capacity compared with the theoretic capacity results from the formation of SEI film and an interfacial charging mechanism, where Li ions and electrons can be stored at the interface [8]. However, the initial columbic efficiency is low because of the irreversible capacity, which can be attributed to the irreversible reactions involved in the formation of SEI film, the decomposition of the electrolyte and the formation of irreversible Li2O. Fig. 2c shows the discharge capacity versus cycle number and the corresponding Coulombic efficiency of porous Fe2O3 electrode at a constant rate of 200 mA g 1. It shows that the porous Fe2O3 electrode exhibits excellent cyclic performance. After 150 cycles, it can still deliver a specific capacity of 891.8 mAh g 1, retaining 86.4% of the capacity of the second cycle. As is well known, the formation and stabilization of the SEI layer is a gradual process, so that a growing Coulombic efficiency gradually emerges [9]. From the 10th cycle, the Coulombic efficiency of porous Fe2O3 electrode is steady and above 98%. The rate capability of the porous Fe2O3 electrode is demonstrated in Fig. 2d. At current densities of 200, 500, 1000, 1250, 1500 and 2000 mA g 1, the reversible specific capacity is 1030.5, 879.3, 792.5, 710.8, 640.8 and 584.3 mAh g 1, respectively. With increasing the rate from 200 to 2000 mA g 1, the discharge capacity of the porous Fe2O3 electrode decreases gradually, indicating the diffusion-controlled kinetics process for the electrode reaction [10]. Compared with other reported Fe2O3based materials [11–13], the porous Fe2O3 nanostructure manifests greatly enhanced cycling capability and rate retention. These remarkable lithium storage properties are related to the unique nanostructure of the porous Fe2O3 nanoparticles. Firstly, the Fe2O3 nanoparticles of about 100 nm in diameter will provide a short pathway for the diffusion of lithium ion. Secondly, the open pores
in porous Fe2O3 nanoparticles can not only offer more exposed active sites between active material and electrolyte, but also keep stable by buffering the volume expansion.
4. Conclusions Uniform porous Fe2O3 nanoparticles were synthesized by biomorphic combustion synthesis method using cotton as the template in large scale. The porous Fe2O3 electrode shows excellent cycling and rate performance due to its relatively high surface area, good contact of active materials and electrolyte and good accommodation of the volume change.
Acknowledgments This work is supported by the National Science and Technology Support Program (2012BAC08B08).
References [1] P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, J.M. Tarascon, Nature 407 (2000) 496–499. [2] M. Armand, J.M. Tarascon, Nature 451 (2008) 652–657. [3] A.S. Arico, P. Bruce, B. Scrosati, J.M. Tarascon, W.V. Schalkwijk, Nat. Mater. 4 (2005) 366–377. [4] Y.F. Yuan, Y.B. Pei, J. Fang, H.L. Zhu, J.L. Yang, S.Y. Guo, Mater. Lett. 91 (2013) 279–282. [5] B. Wang, J.S. Chen, H.B. Wu, Z.Y. Wang, X.W. Lou, J. Am. Chem. Soc. 133 (2011) 17146–17148. [6] S.R. Jain, K.C. Adiga, V.R.P. Verneker, Combust. Flame 40 (1981) 71–79.
110
Q.Q. Xiong et al. / Materials Letters 168 (2016) 107–110
[7] Q. Peng, Y.J. Dong, Y.D. Li, Angew. Chem. Int. Ed. 42 (2003) 3027–3030. [8] A. Debart, L. Dupont, P. Poizot, J.B. Leriche, J.M. Tarascon, J. Electrochem. Soc. 148 (2001) A1266–A1274. [9] X. Huang, H. Yu, J. Chen, Z.Y. Lu, R. Yazami, H.H. Hng, Adv. Mater. 26 (2014) 1296–1303. [10] C. Montella, J. Mater. Chem. 20 (2010) 2092–2098.
[11] J.J. Wang, H. Zhou, J. Nanda, P.V. Braun, Chem. Mater. 27 (2015) 2803–2811. [12] Y. Park, M. Oh, J.S. Park, S.H. Baek, M. Kim, S. Kim, J.H. Kim, Carbon 94 (2015) 9–17. [13] Y.K. Wang, L.C. Yang, R.Z. Hu, W. Sun, J.W. Liu, L.Z. Ouyang, B. Yuan, H.H. Wang, M. Zhu, J. Power Sources 288 (2015) 314–319.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Biomorphic combustion synthesis of hematite porous structure with enhanced Li storage properties Q.Q. Xiong a,b,n, Z.G. Ji a, H.Y. Qin a a b
College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, People’s Republic of China State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310018, People’s Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 9 November 2015 Accepted 10 January 2016 Available online 11 January 2016
Uniform porous Fe2O3 nanostructure was prepared by a facile and effective biomorphic combustion synthesis. Porous Fe2O3 nanostructure is assembled by primary nanoparticles and lots of open pores between interconnected nanoparticles. As an anode material for the lithium-ion batteries (LIBs), the resultant porous Fe2O3 electrode shows high specific capacity and good cycle stability (891.8 mAh g 1 at 200 mA g 1 up to 150 cycles), as well as enhanced rate capability. The excellent electrochemical performance can be attributed to 3D porous structure with the short pathway for the diffusion of Li þ , high interfacial contact area between the nanoparticles and electrolyte, and good accommodation of structural stress. & 2016 Elsevier B.V. All rights reserved.
Keywords: Hematite Nanoparticles Porous materials Combustion synthesis Lithium-ion battery
1. Introduction Recently, 3d transition metal oxides have been widely investigated as promising anodes in the field of LIBs since they were firstly proposed by Tarascon et al. [1]. They possess much higher capacities (two or three times) than that of graphite, and smaller volume change during the charge-discharge process than that of alloy anodes, which will hopefully realize the wide application of LIBs in various fields such as electric vehicles, military, and the like [2–4]. Among them, iron oxide, such as hematite (α-Fe2O3), has gained much attention due to its high theoretic capacity (1007 mAh g 1), non-toxicity, natural abundance, and low cost. Despite its many advantages, Fe2O3 suffers from low electrical conductivity, large volume expansion during the conversion reaction process, thus resulting in large irreversible loss, poor electrochemical performance and limiting its wide practical application [5]. These issues can partially overcome by developing different nanostructures, which is an effective strategy to ameliorate the electrochemical capability for their large surface area, the sufficient contact between active material and electrolyte, and the short Li ion diffusion path. In this work, we used a facile and high-efficiency biomorphic combustion synthesis to prepare porous Fe2O3 nanostructure with cotton as template. It should be noted that this synthetic process meets the demand of the green and sustainable modern industry n Corresponding author at: College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, People's Republic of China. E-mail address: [email protected] (Q.Q. Xiong).
http://dx.doi.org/10.1016/j.matlet.2016.01.047 0167-577X/& 2016 Elsevier B.V. All rights reserved.
and is more suitable for large-scale production. Compared to many other methods, this biomorphic combustion synthesis requires less complicated reactants and synthetic conditions, which are more attractive with respect to both cost and scalability. In the asprepared sample, the primary Fe2O3 nanoparticles form a secondary structure, resulting in an organized 3D porous nanostructure. While the small dimensions of the primary nanoparticles make ionic and electronic transport much easier, the secondary porous structure can well accommodate the strain associated with Li þ intercalation and the volume expansion of active materials. Thus, as the anode material for LIBs, the porous Fe2O3 nanostructure shows greatly enhanced electrochemical performance.
2. Experimental Porous Fe2O3 structure was synthesized via a cellulose combustion method. 40.4 g Fe(NO3)3 9H2O was dissolved in 100 mL of ethanol with stirring, into which clean cotton was soaked for 4 h. Then the wet cotton was directly put into a chamber furnace which was pre-heated to 500 °C in air, and treated at this temperature for 1 h to obtain the porous Fe2O3 structure. The morphology and microstructure of products were characterized using X-ray diffractometer (XRD, Rigaku D/max 2550 PC, Cu Kα), scanning electron microscope (SEM, Hitachi S-4700) and transmission electron microscope (TEM, JEM 200CX at 160 kV and Tecnai G2 F30 at 200 kV). The electrochemical measurements were performed using a coin-type half cell (CR 2025). The slurry consisted of 85 wt% Fe2O3, 10 wt% acetylene black and 5 wt% polyvinylidene fluoride (PVDF)
Q.Q. Xiong et al. / Materials Letters 168 (2016) 107–110
(d)
20
30
40
50
(214) (300)
(116)
(012)
Intensity (a.u.)
(c)
(b)
(018)
(a)
(024)
SEM, TEM and powder XRD were used to analyze the morphology and crystallinity of as-prepared porous Fe2O3 nanostructure. In Fig. 1a, the sample shows a 3D porous matrix rather than the morphology of the original cotton fibers, which is ascribed to the combustion method. Combustion synthesis involves an exothermic and self-sustaining chemical reaction, resulting in the collapse of the original fibrous structure of the cotton [6]. The relatively high-magnification SEM image is shown in Fig. 1b. Porous Fe2O3 nanostructure contains primary particles of about 100 nm in diameter, and these primary particles form a 3D porous matrix. The detailed morphological and structural features of the powder are also examined by TEM. Fig. 1c further confirms the 3D porous nanostructure. There are lots of open pores ranging from 20–100 nm between interconnected nanoparticles. The HRTEM image in the inset shows well-resolved atomic lattice fringes with
(113)
3. Results and discussion
adjacent lattice planes of 0.25 nm, which is in good agreement with the value of the (110) plane of rhombohedral Fe2O3. The crystal structure of sample is analyzed by XRD analysis in Fig. 1d. All the diffraction peaks confirm that the crystal structure is in agreement with the standard values for the rhombohedral phase of Fe2O3 [JCPDS Card no. 33-0664]. The Li storage capability of porous Fe2O3 nanostructure is fully characterized to demonstrate its potential use as anode for LIBs. The CV collected at a scan rate of 0.1 mV s 1 is shown in Fig. 2a. During the first discharge process, there is one large cathodic peak located at 0.71 V, along with a very small peak centered at 1.5 V. The small peak indicates the intercalation of Li into the crystal structure of the Fe2O3 nanostructure. The strong peak at 0.71 V can be attributed to the complete reduction of Fe3 þ to Fe0 and the irreversible decomposition reaction of electrolyte. During the anodic polarization process, two peaks are present at 1.63 and 1.84 V, corresponding to the oxidation of Fe0 to Fe2 þ and further oxidation to Fe3 þ . During the second cycle, the full lithiation voltage shifts to 0.92 V, which is higher than that in the first cycle (about 0.71 V). It is probably due to the reduced polarization of the porous Fe2O3 electrode resulting from a microstructural alteration after the first lithiation [7]. Fig. 2b shows typical discharge and charge voltage profiles of the first two cycles at 200 mA g 1. During first discharging process, a poorly defined plateau (1.2– 0.9 V) and a perfect one at about 0.85 V are observed, which are in agreement with the CV results. The two plateaus are followed by a continuous sloping curve down to the cut voltage of 0.01 V. The first discharge capacity of porous Fe2O3 electrode is 1195.5 mAh g 1, whereas the first charge capacity is
(104)
was pasted on copper foil. Test cells were assembled in an argonfilled glove box with the metallic lithium foil as both the reference and counter electrodes, 1 M LiPF6 in ethylene carbonate (EC)-dimethyl carbonate (DME) (1:1 in volume) as the electrolyte, and a polypropylene (PP) micro-porous film (Cellgard 2300) as the separator. The galvanostatic charge-discharge tests were conducted on LAND battery program-control test system in the voltage range of 0.01–3.0 V (versus Li/Li þ ) at room temperature (25 71 °C). Cyclic voltammetry (CV) was performed on CHI660C electrochemical workstation.
(110)
108
60
70
80
2 Theta degree Fig. 1. Morphology and crystallinity characterization of porous Fe2O3 nanoparticles: (a,b) SEM images; (c) TEM image, with HRTEM image (inset); (d) XRD pattern.
Q.Q. Xiong et al. / Materials Letters 168 (2016) 107–110
(a)
109
(b) 3.0
Potential(V vs. Li/Li
+
)
0.5
Current (A g
-1
)
0.0 -0.5 -1.0
1 st 2 nd
-1.5 -2.0 0.0
0.5
1.0
1.5
2.0
Potential (V vs. Li/Li
2.5
900
0.5 -1
600
75
100
125
0.0 150
Coulombic Efficiency -1 Capacity (mAh g )
) -1
Capacity (mAh g
1200
50
0.5
Discharge
0
200
400
600
800 1000 1200 1400
Capacity(mAh g
1.0
25
1.0
)
(d)
0
1 st 2 nd
1.5
+
1500
300
Charge
2.0
0.0
3.0
(c)
200 mA g
2.5
-1
)
1500 1200
200 mA g
900
1000 mA g 500 mA g
1500 mA g
600
1250 mA g 2000 mA g
300 0
0
5
Cycle Number
10
15
20
25
30
Cycle Number
Fig. 2. Electrochemical performance of porous Fe2O3 electrode: (a) CV curve for the first two cycles at a scan rate of 0.1 mV s 1 between 0.01 and 3.0 V; (b) charge/discharge profiles at the first two cycles at 200 mA g 1; (c) cycling performance at 200 mA g 1; (d) rate capability at different current densities ranging from 200 to 2000 mA g 1.
997.7 mAh g 1, resulting in an initial columbic efficiency of 83.5%. The extra capacity compared with the theoretic capacity results from the formation of SEI film and an interfacial charging mechanism, where Li ions and electrons can be stored at the interface [8]. However, the initial columbic efficiency is low because of the irreversible capacity, which can be attributed to the irreversible reactions involved in the formation of SEI film, the decomposition of the electrolyte and the formation of irreversible Li2O. Fig. 2c shows the discharge capacity versus cycle number and the corresponding Coulombic efficiency of porous Fe2O3 electrode at a constant rate of 200 mA g 1. It shows that the porous Fe2O3 electrode exhibits excellent cyclic performance. After 150 cycles, it can still deliver a specific capacity of 891.8 mAh g 1, retaining 86.4% of the capacity of the second cycle. As is well known, the formation and stabilization of the SEI layer is a gradual process, so that a growing Coulombic efficiency gradually emerges [9]. From the 10th cycle, the Coulombic efficiency of porous Fe2O3 electrode is steady and above 98%. The rate capability of the porous Fe2O3 electrode is demonstrated in Fig. 2d. At current densities of 200, 500, 1000, 1250, 1500 and 2000 mA g 1, the reversible specific capacity is 1030.5, 879.3, 792.5, 710.8, 640.8 and 584.3 mAh g 1, respectively. With increasing the rate from 200 to 2000 mA g 1, the discharge capacity of the porous Fe2O3 electrode decreases gradually, indicating the diffusion-controlled kinetics process for the electrode reaction [10]. Compared with other reported Fe2O3based materials [11–13], the porous Fe2O3 nanostructure manifests greatly enhanced cycling capability and rate retention. These remarkable lithium storage properties are related to the unique nanostructure of the porous Fe2O3 nanoparticles. Firstly, the Fe2O3 nanoparticles of about 100 nm in diameter will provide a short pathway for the diffusion of lithium ion. Secondly, the open pores
in porous Fe2O3 nanoparticles can not only offer more exposed active sites between active material and electrolyte, but also keep stable by buffering the volume expansion.
4. Conclusions Uniform porous Fe2O3 nanoparticles were synthesized by biomorphic combustion synthesis method using cotton as the template in large scale. The porous Fe2O3 electrode shows excellent cycling and rate performance due to its relatively high surface area, good contact of active materials and electrolyte and good accommodation of the volume change.
Acknowledgments This work is supported by the National Science and Technology Support Program (2012BAC08B08).
References [1] P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, J.M. Tarascon, Nature 407 (2000) 496–499. [2] M. Armand, J.M. Tarascon, Nature 451 (2008) 652–657. [3] A.S. Arico, P. Bruce, B. Scrosati, J.M. Tarascon, W.V. Schalkwijk, Nat. Mater. 4 (2005) 366–377. [4] Y.F. Yuan, Y.B. Pei, J. Fang, H.L. Zhu, J.L. Yang, S.Y. Guo, Mater. Lett. 91 (2013) 279–282. [5] B. Wang, J.S. Chen, H.B. Wu, Z.Y. Wang, X.W. Lou, J. Am. Chem. Soc. 133 (2011) 17146–17148. [6] S.R. Jain, K.C. Adiga, V.R.P. Verneker, Combust. Flame 40 (1981) 71–79.
110
Q.Q. Xiong et al. / Materials Letters 168 (2016) 107–110
[7] Q. Peng, Y.J. Dong, Y.D. Li, Angew. Chem. Int. Ed. 42 (2003) 3027–3030. [8] A. Debart, L. Dupont, P. Poizot, J.B. Leriche, J.M. Tarascon, J. Electrochem. Soc. 148 (2001) A1266–A1274. [9] X. Huang, H. Yu, J. Chen, Z.Y. Lu, R. Yazami, H.H. Hng, Adv. Mater. 26 (2014) 1296–1303. [10] C. Montella, J. Mater. Chem. 20 (2010) 2092–2098.
[11] J.J. Wang, H. Zhou, J. Nanda, P.V. Braun, Chem. Mater. 27 (2015) 2803–2811. [12] Y. Park, M. Oh, J.S. Park, S.H. Baek, M. Kim, S. Kim, J.H. Kim, Carbon 94 (2015) 9–17. [13] Y.K. Wang, L.C. Yang, R.Z. Hu, W. Sun, J.W. Liu, L.Z. Ouyang, B. Yuan, H.H. Wang, M. Zhu, J. Power Sources 288 (2015) 314–319.