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Effect of enhanced structural stability of Si-O-C anode by carbon nanotubes for lithium-ion battery
Materials Letters 245 (2019) 200–203
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Effect of enhanced structural stability of Si-O-C anode by carbon nanotubes for lithium-ion battery Seongki Ahn a, Hiroki Nara a, Tokihiko Yokoshima a, Toshiyuki Momma a,b,c,⇑, Tetsuya Osaka a,b,c a
Research Organization for Nano and Life Innovation, Waseda University, 513, Wasedatsurumakicho, Shinjuku-ku, Tokyo 162-0041, Japan Faculty of Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan c Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26, Nishiwaseda, Shinjuku-ku, Tokyo 169-0051, Japan b
a r t i c l e
i n f o
Article history: Received 5 January 2019 Received in revised form 1 March 2019 Accepted 6 March 2019 Available online 7 March 2019 Keywords: Silicon anode Si-O-C composite CNTs Lithium-ion battery Full-cell configuration
a b s t r a c t Herein, we synthesized the structural stabilized Si-O-C composite using carbon nanotubes (CNTs). The SiO-C/CNTs is employed and tested as an anode for lithium-ion batteries (LIBs) assembled with the LiCoO2 cathode. Through the usage of CNTs, it is possible to improve the cyclability and capacity retention ratio by enhanced structural stability. The enhanced electrochemical performance of LiCoO2//Si-O-C full-cell with CNTs indicates the high potential as a way to produce the high-performance LIBs. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Silicon has attracted as a promising alternative anode material for high energy density lithium-ion batteries (LIBs) due to its high theoretical capacity than graphite which is widely used as an anode (Li4.4Si: 4200 mAh g 1, Li6C: 372 mAh g 1). For these reasons, silicon-based materials are drawing attention as the upcoming anode materials for next-generation energy storage devices [1,2]. We have reported the Si-O-C composite prepared by electrodeposition in an organic solvent [3]. The Si-O-C composite shows the outstanding cyclability with a good discharge capacity of 842 mAh g 1 at the 7200th cycle. The reason for this exceptional result is that the homogeneous dispersion of amorphous silicon in the organic/inorganic compound, and the co-deposited oxygen and carbon act as buffer materials to reduce the pulverization of SiO-C composite during charge/discharge cycling [4]. Despite the outstanding performance of Si-O-C composite, it is not easily transposable to build the full-cell configuration because of structural weakness of Si-O-C composite. To overcome this issue, various attempts have been conducted to increase the structural stability
⇑ Corresponding author at: Faculty of Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan E-mail address: [email protected] (T. Momma). https://doi.org/10.1016/j.matlet.2019.03.012 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
of Si-O-C composite using Ni micro-nanocone substrate [5], and carbon-paper [6]. Herein, we synthesized the 3D structured carbon nanotubes (CNTs) layer on a Cu substrate to increase the structural stability of Si-O-C composite, abbreviated as Si-O-C/CNTs hereafter. In our previous report, we have revealed that the CNTs layer enhances the structural stability of the Si-O-C composite, showing the stable cyclability for 100 cycles at 0.1 C-rate [7]. However, structural stability at the high C-rate condition and applicability as an anode for full-cell configuration were not investigated. In this study, we examined the structural stability of Si-O-C composite by the halfcell test at the high C-rate condition to measure the amounts of silicon loss after for 500 cycles. Besides, we verified that the amounts of deposited silicon could be controlled by quantities of electricity for electrodeposition for the full-cell design. The LIBs full-cell consisted of Si-O-C/CNTs exhibited the improved cyclability than that of full-cell assembled by Si-O-C composite. We believe that using CNTs is a way to realize the full-cell configuration using Si-O-C composite. 2. Experimental The CNTs layer was synthesized by electrophoretic deposition. The Si-O-C composite was synthesized by electrodeposition on Cu or CNTs/Cu substrate, respectively. The detailed preparation process and characterization is shown in the Supporting Information and in our previous report [7].
S. Ahn et al. / Materials Letters 245 (2019) 200–203
3. Results and discussion Fig. 1(a)–(d) illustrates the surface morphology of Si-O-C and SiO-C/CNTs before and after charge/discharge test for 500 cycles. Before the charge/discharge test, both samples show the homogeneously deposited Si-O-C on Cu and CNTs/Cu substrate. After the charge/discharge test, the Si-O-C/Cu shows the cracked surface with exfoliation of Si-O-C composite because of silicon volume change during lithiation/de-lithiation. However, Si-O-C/CNTs indicates swelled Si-O-C composite without exfoliation of Si-O-C. In our previous report, we revealed that the CNTs layer enhances the adhesion strength between Si-O-C composite and Cu substrate after during silicon volume change [7]. Likewise, in this study, the improved structural stability of Si-O-C composite by addition of CNTs layer could be identified even after the 500 cycles at higher C-rate of 2 C. The amount of deposited silicon of Si-O-C and Si-O-C/CNTs was measured by ICP analysis in Fig. 1(e). Before the charge/discharge test, the Si-O-C and Si-O-C/CNTs possess the silicon amounts of 44 and 55 lg cm 2, respectively. After cycling for the 500 cycles, the silicon amounts of both samples were decreased to 29 and 49 lg cm 2, respectively. To compare the decreasing silicon ratio, the silicon retention ratio was calculated in Fig. 1(f). The silicon amounts of Si-O-C decreased by 31% after a charge/discharge test, whereas, the Si-O-C/CNTs has higher silicon retention ratio. From these results, we can suggest that using of CNTs is a good way to prevent structural destruction of Si-O-C composite after volume change. The electrochemical performance of LIBs full-cell assembled with lithium cobalt oxide (LCO) and Si-O-C or Si-O-C/CNTs was tested to check the effect of enhanced structural stability of SiO-C composite by addition of CNTs. Before fabrication of fullcell, the capacity balance between cathode and anode must be controlled to obtain the optimized full-cell performance. The detail information of cell balancing is described in the Supporting Information. Fig. 2(a) shows the cyclability of LCO//Si-O-C and LCO//Si-O-C/CNTs at 0.1 C-rate. The LCO//Si-O-C delivered a discharge capacity of 147 and 50 mAh g 1 at the 1st and 30th cycle. The rapid capacity fading was observed from 1st to 10th cycle, accompanied by rapid degradation of coulombic efficiency from 93 to 88%. At the initial cycle, the volume of silicon composite is changed by lithiation/de-lithiation and this electrochemical behavior of silicon effects on the structural destruction of Si-O-C composite [8]. The structural defeats of Si-O-C composite
201
lead to consecutive lithium ions consumption for the SEI formation on the cracked surface, and this is one of the reasons for the capacity fading and low columbic efficiency at initial cycles. In this study, the Si-O-C composite was synthesized at a passing charge of 4 C cm 2 for optimizing full-cell configuration. The Si-O-C composite synthesized at a passing charge of 4 C cm 2 shows poor cyclability than Si-O-C/CNTs composite deposited at a passing charge of 2 C cm 2 as shown in Fig. S2, implying that the Si-O-C composite has lower structural stability. For that reason, in the case of LCO//Si-O-C/CNTs, the LIBs full-cell shows stable cyclability at initial cycles with a stable coulombic efficiency of 95% and 96% at the 1st and 10th cycle. The capacity retention ratio of both samples is calculated and shown in Fig. 2(b). The LCO//Si-O-C shows the rapid decreasing in capacity retention ratio. There were many reports to reveal the relationship between cell optimization and poor cell performance [9]. Herein, the cell optimization of LIBs full-cell was conducted very carefully as described in Supporting Information. So, the poor electrochemical performance of LIBs full-cell is attributed to the low cyclability of Si-O-C composite synthesized at a passing charge of 4 C cm 2. The IR drop change was calculated by charge/discharge curves for 10 cycles in Fig. 2(c). The LCO//Si-O-C shows the higher IR drop change than LCO//Si-O-C/CNTs. We supposed that the isolated Si-O-C clusters came from the structural collapse of Si-O-C composite might increase the internal resistance during the charge/discharge process. Fig. 2(d) demonstrates the capacity retention ratio of both samples at a 2 C-rate. The LCO//Si-O-C shows rapid capacity decay rate of 98% for 100 cycles, whereas, LCO//Si-O-C/CNTs presents improved capacity decay rate of 53%. From these results, it could be revealed that the enhanced structural stability of Si-O-C composite by CNTs influences on improving the cell performance of LIBs fullcell configuration even at the high C-rate condition. To further examine the internal resistance of LCO//Si-O-C and LCO//Si-O-C/CNTs, the electrochemical impedance spectroscopy (EIS) was conducted with a frequency range of 1 MHz-1 Hz in Fig. 3. The 100% of DOD (depth of discharge) state was employed for EIS measurement, and the DOD state of each sample was controlled by a discharge state at 2.75 V (100% of DOD). All spectra from both samples demonstrate that the suppressed semi-circles from a high to the middle-frequency region and linear part at the low-frequency region represents the charge transfer resistance (Rct) of LCO cathode and the Warburg diffusion related to lithium ions diffusion in solid active materials [10,11].
Fig. 1. Plane view SEM images of Si-O-C composite; before charge/discharge of (a) Si-O-C, (b) Si-O-C/CNTs, and after cycling for the 500 cycles of (c) Si-O-C, (d) Si-O-C/CNTs at 2 C-rate. ICP measurement results; (e) the amounts of deposited silicon, and (f) retention ratio of silicon amounts.
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S. Ahn et al. / Materials Letters 245 (2019) 200–203
Fig. 2. (a) Cyclability of LCO//Si-O-C and LCO//Si-O-C/CNTs with columbic efficiency, (b) capacity retention ratio, and (c) comparison of IR drop tested at 0.1 C-rate. (d) Capacity retention ratio tested at 2C-rate.
internal resistance of Si-O-C composite by preventing the structural collapse of Si-O-C. Also, the high electric conductivity of CNTs as electron pathway is also one of the reasons to decrease the internal resistance, resulting in good rate-performance in Fig. S4.
4. Conclusions In this paper, we revealed that employing CNTs layer into Si-OC composite protects the structural collapse of Si-O-C composite during silicon volume change. From the charge/discharge test and EIS measurement of LIBs full-cell, it was observed that the employing of CNTs improves full-cell performance and reduces the internal stress by preventing the structural collapse even at the high C-rate condition. We believe that using Si-O-C/CNTs composite as anode will provide some novel ideas for highperformance LIBs. Acknowledgements Fig. 3. Nyquist plots of LCO//Si-O-C and LCO//Si-O-C/CNTs tested with a frequency range of 1 MHz-1 Hz before charge/discharge.
The LCO//Si-O-C/CNTs demonstrates the smaller magnitudes of the semicircle than LCO//Si-O-C. This result implies that the Rct was remarkably reduced by employing CNTs, which acts a role bridge to improve the electrical conductivity of the entire fullcell. Figure S3 shows that the CNTs were linked between Si-O-C composites. Therefore, it is supposed that the CNTs decreases the
This work is partly supported by Advanced Low Carbon Technology Research and Development Program Special Priority Research Area ‘‘Next-generation Rechargeable Battery” (ALCASpring) from the Japan Science and Technology Agency (JST), Japan.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.03.012.
S. Ahn et al. / Materials Letters 245 (2019) 200–203
References [1] H. Jung, M. Park, Y.-G. Yoon, G.-B. Kim, S.-K. Joo, J. Power Sources 115 (2003) 346–351. [2] S. Ohara, J. Suzuki, K. Sekine, T. Takamura, J. Power Sources 136 (2004) 303– 306. [3] T. Momma, S. Aoki, H. Nara, T. Yokoshima, T. Osaka, Electrochem. Commun. 13 (2011) 969–972. [4] H. Nara, T. Yokoshima, T. Momma, T. Osaka, Energy Environ. Sci. 5 (2012) 6500–6505. [5] T. Hang, H. Nara, T. Yokoshima, T. Momma, T. Osaka, J. Power Sources 222 (2013) 503–509.
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[6] S. Ahn, M. Jeong, K. Miyamoto, T. Yokoshima, H. Nara, T. Momma, T. Osaka, J. Electrochem. Soc. 164 (2017) A355–A359. [7] S. Ahn, M. Jeong, T. Yokoshima, H. Nara, T. Momma, T. Osaka, J. Power Sources 336 (2016) 203–211. [8] H. Nara, T. Yokoshima, M. Otaki, T. Momma, T. Osaka, Electrochim. Acta 110 (2013) 403–410. [9] M.-S. Balogun, W. Qiu, Y. Luo, H. Meng, W. Mai, A. Onasanya, T.K. Olaniyi, Y. Tong, Nano Res. 9 (2016) 2823–2851. [10] H. Sun, X. He, J. Ren, J. Li, C. Jiang, C. Wan, Electrochim. Acta 52 (2007) 4312– 4316. [11] Y.-S. Han, J.-Y. Lee, Electrochim. Acta 48 (2003) 1073–1079.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Effect of enhanced structural stability of Si-O-C anode by carbon nanotubes for lithium-ion battery Seongki Ahn a, Hiroki Nara a, Tokihiko Yokoshima a, Toshiyuki Momma a,b,c,⇑, Tetsuya Osaka a,b,c a
Research Organization for Nano and Life Innovation, Waseda University, 513, Wasedatsurumakicho, Shinjuku-ku, Tokyo 162-0041, Japan Faculty of Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan c Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26, Nishiwaseda, Shinjuku-ku, Tokyo 169-0051, Japan b
a r t i c l e
i n f o
Article history: Received 5 January 2019 Received in revised form 1 March 2019 Accepted 6 March 2019 Available online 7 March 2019 Keywords: Silicon anode Si-O-C composite CNTs Lithium-ion battery Full-cell configuration
a b s t r a c t Herein, we synthesized the structural stabilized Si-O-C composite using carbon nanotubes (CNTs). The SiO-C/CNTs is employed and tested as an anode for lithium-ion batteries (LIBs) assembled with the LiCoO2 cathode. Through the usage of CNTs, it is possible to improve the cyclability and capacity retention ratio by enhanced structural stability. The enhanced electrochemical performance of LiCoO2//Si-O-C full-cell with CNTs indicates the high potential as a way to produce the high-performance LIBs. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Silicon has attracted as a promising alternative anode material for high energy density lithium-ion batteries (LIBs) due to its high theoretical capacity than graphite which is widely used as an anode (Li4.4Si: 4200 mAh g 1, Li6C: 372 mAh g 1). For these reasons, silicon-based materials are drawing attention as the upcoming anode materials for next-generation energy storage devices [1,2]. We have reported the Si-O-C composite prepared by electrodeposition in an organic solvent [3]. The Si-O-C composite shows the outstanding cyclability with a good discharge capacity of 842 mAh g 1 at the 7200th cycle. The reason for this exceptional result is that the homogeneous dispersion of amorphous silicon in the organic/inorganic compound, and the co-deposited oxygen and carbon act as buffer materials to reduce the pulverization of SiO-C composite during charge/discharge cycling [4]. Despite the outstanding performance of Si-O-C composite, it is not easily transposable to build the full-cell configuration because of structural weakness of Si-O-C composite. To overcome this issue, various attempts have been conducted to increase the structural stability
⇑ Corresponding author at: Faculty of Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan E-mail address: [email protected] (T. Momma). https://doi.org/10.1016/j.matlet.2019.03.012 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
of Si-O-C composite using Ni micro-nanocone substrate [5], and carbon-paper [6]. Herein, we synthesized the 3D structured carbon nanotubes (CNTs) layer on a Cu substrate to increase the structural stability of Si-O-C composite, abbreviated as Si-O-C/CNTs hereafter. In our previous report, we have revealed that the CNTs layer enhances the structural stability of the Si-O-C composite, showing the stable cyclability for 100 cycles at 0.1 C-rate [7]. However, structural stability at the high C-rate condition and applicability as an anode for full-cell configuration were not investigated. In this study, we examined the structural stability of Si-O-C composite by the halfcell test at the high C-rate condition to measure the amounts of silicon loss after for 500 cycles. Besides, we verified that the amounts of deposited silicon could be controlled by quantities of electricity for electrodeposition for the full-cell design. The LIBs full-cell consisted of Si-O-C/CNTs exhibited the improved cyclability than that of full-cell assembled by Si-O-C composite. We believe that using CNTs is a way to realize the full-cell configuration using Si-O-C composite. 2. Experimental The CNTs layer was synthesized by electrophoretic deposition. The Si-O-C composite was synthesized by electrodeposition on Cu or CNTs/Cu substrate, respectively. The detailed preparation process and characterization is shown in the Supporting Information and in our previous report [7].
S. Ahn et al. / Materials Letters 245 (2019) 200–203
3. Results and discussion Fig. 1(a)–(d) illustrates the surface morphology of Si-O-C and SiO-C/CNTs before and after charge/discharge test for 500 cycles. Before the charge/discharge test, both samples show the homogeneously deposited Si-O-C on Cu and CNTs/Cu substrate. After the charge/discharge test, the Si-O-C/Cu shows the cracked surface with exfoliation of Si-O-C composite because of silicon volume change during lithiation/de-lithiation. However, Si-O-C/CNTs indicates swelled Si-O-C composite without exfoliation of Si-O-C. In our previous report, we revealed that the CNTs layer enhances the adhesion strength between Si-O-C composite and Cu substrate after during silicon volume change [7]. Likewise, in this study, the improved structural stability of Si-O-C composite by addition of CNTs layer could be identified even after the 500 cycles at higher C-rate of 2 C. The amount of deposited silicon of Si-O-C and Si-O-C/CNTs was measured by ICP analysis in Fig. 1(e). Before the charge/discharge test, the Si-O-C and Si-O-C/CNTs possess the silicon amounts of 44 and 55 lg cm 2, respectively. After cycling for the 500 cycles, the silicon amounts of both samples were decreased to 29 and 49 lg cm 2, respectively. To compare the decreasing silicon ratio, the silicon retention ratio was calculated in Fig. 1(f). The silicon amounts of Si-O-C decreased by 31% after a charge/discharge test, whereas, the Si-O-C/CNTs has higher silicon retention ratio. From these results, we can suggest that using of CNTs is a good way to prevent structural destruction of Si-O-C composite after volume change. The electrochemical performance of LIBs full-cell assembled with lithium cobalt oxide (LCO) and Si-O-C or Si-O-C/CNTs was tested to check the effect of enhanced structural stability of SiO-C composite by addition of CNTs. Before fabrication of fullcell, the capacity balance between cathode and anode must be controlled to obtain the optimized full-cell performance. The detail information of cell balancing is described in the Supporting Information. Fig. 2(a) shows the cyclability of LCO//Si-O-C and LCO//Si-O-C/CNTs at 0.1 C-rate. The LCO//Si-O-C delivered a discharge capacity of 147 and 50 mAh g 1 at the 1st and 30th cycle. The rapid capacity fading was observed from 1st to 10th cycle, accompanied by rapid degradation of coulombic efficiency from 93 to 88%. At the initial cycle, the volume of silicon composite is changed by lithiation/de-lithiation and this electrochemical behavior of silicon effects on the structural destruction of Si-O-C composite [8]. The structural defeats of Si-O-C composite
201
lead to consecutive lithium ions consumption for the SEI formation on the cracked surface, and this is one of the reasons for the capacity fading and low columbic efficiency at initial cycles. In this study, the Si-O-C composite was synthesized at a passing charge of 4 C cm 2 for optimizing full-cell configuration. The Si-O-C composite synthesized at a passing charge of 4 C cm 2 shows poor cyclability than Si-O-C/CNTs composite deposited at a passing charge of 2 C cm 2 as shown in Fig. S2, implying that the Si-O-C composite has lower structural stability. For that reason, in the case of LCO//Si-O-C/CNTs, the LIBs full-cell shows stable cyclability at initial cycles with a stable coulombic efficiency of 95% and 96% at the 1st and 10th cycle. The capacity retention ratio of both samples is calculated and shown in Fig. 2(b). The LCO//Si-O-C shows the rapid decreasing in capacity retention ratio. There were many reports to reveal the relationship between cell optimization and poor cell performance [9]. Herein, the cell optimization of LIBs full-cell was conducted very carefully as described in Supporting Information. So, the poor electrochemical performance of LIBs full-cell is attributed to the low cyclability of Si-O-C composite synthesized at a passing charge of 4 C cm 2. The IR drop change was calculated by charge/discharge curves for 10 cycles in Fig. 2(c). The LCO//Si-O-C shows the higher IR drop change than LCO//Si-O-C/CNTs. We supposed that the isolated Si-O-C clusters came from the structural collapse of Si-O-C composite might increase the internal resistance during the charge/discharge process. Fig. 2(d) demonstrates the capacity retention ratio of both samples at a 2 C-rate. The LCO//Si-O-C shows rapid capacity decay rate of 98% for 100 cycles, whereas, LCO//Si-O-C/CNTs presents improved capacity decay rate of 53%. From these results, it could be revealed that the enhanced structural stability of Si-O-C composite by CNTs influences on improving the cell performance of LIBs fullcell configuration even at the high C-rate condition. To further examine the internal resistance of LCO//Si-O-C and LCO//Si-O-C/CNTs, the electrochemical impedance spectroscopy (EIS) was conducted with a frequency range of 1 MHz-1 Hz in Fig. 3. The 100% of DOD (depth of discharge) state was employed for EIS measurement, and the DOD state of each sample was controlled by a discharge state at 2.75 V (100% of DOD). All spectra from both samples demonstrate that the suppressed semi-circles from a high to the middle-frequency region and linear part at the low-frequency region represents the charge transfer resistance (Rct) of LCO cathode and the Warburg diffusion related to lithium ions diffusion in solid active materials [10,11].
Fig. 1. Plane view SEM images of Si-O-C composite; before charge/discharge of (a) Si-O-C, (b) Si-O-C/CNTs, and after cycling for the 500 cycles of (c) Si-O-C, (d) Si-O-C/CNTs at 2 C-rate. ICP measurement results; (e) the amounts of deposited silicon, and (f) retention ratio of silicon amounts.
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Fig. 2. (a) Cyclability of LCO//Si-O-C and LCO//Si-O-C/CNTs with columbic efficiency, (b) capacity retention ratio, and (c) comparison of IR drop tested at 0.1 C-rate. (d) Capacity retention ratio tested at 2C-rate.
internal resistance of Si-O-C composite by preventing the structural collapse of Si-O-C. Also, the high electric conductivity of CNTs as electron pathway is also one of the reasons to decrease the internal resistance, resulting in good rate-performance in Fig. S4.
4. Conclusions In this paper, we revealed that employing CNTs layer into Si-OC composite protects the structural collapse of Si-O-C composite during silicon volume change. From the charge/discharge test and EIS measurement of LIBs full-cell, it was observed that the employing of CNTs improves full-cell performance and reduces the internal stress by preventing the structural collapse even at the high C-rate condition. We believe that using Si-O-C/CNTs composite as anode will provide some novel ideas for highperformance LIBs. Acknowledgements Fig. 3. Nyquist plots of LCO//Si-O-C and LCO//Si-O-C/CNTs tested with a frequency range of 1 MHz-1 Hz before charge/discharge.
The LCO//Si-O-C/CNTs demonstrates the smaller magnitudes of the semicircle than LCO//Si-O-C. This result implies that the Rct was remarkably reduced by employing CNTs, which acts a role bridge to improve the electrical conductivity of the entire fullcell. Figure S3 shows that the CNTs were linked between Si-O-C composites. Therefore, it is supposed that the CNTs decreases the
This work is partly supported by Advanced Low Carbon Technology Research and Development Program Special Priority Research Area ‘‘Next-generation Rechargeable Battery” (ALCASpring) from the Japan Science and Technology Agency (JST), Japan.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.03.012.
S. Ahn et al. / Materials Letters 245 (2019) 200–203
References [1] H. Jung, M. Park, Y.-G. Yoon, G.-B. Kim, S.-K. Joo, J. Power Sources 115 (2003) 346–351. [2] S. Ohara, J. Suzuki, K. Sekine, T. Takamura, J. Power Sources 136 (2004) 303– 306. [3] T. Momma, S. Aoki, H. Nara, T. Yokoshima, T. Osaka, Electrochem. Commun. 13 (2011) 969–972. [4] H. Nara, T. Yokoshima, T. Momma, T. Osaka, Energy Environ. Sci. 5 (2012) 6500–6505. [5] T. Hang, H. Nara, T. Yokoshima, T. Momma, T. Osaka, J. Power Sources 222 (2013) 503–509.
203
[6] S. Ahn, M. Jeong, K. Miyamoto, T. Yokoshima, H. Nara, T. Momma, T. Osaka, J. Electrochem. Soc. 164 (2017) A355–A359. [7] S. Ahn, M. Jeong, T. Yokoshima, H. Nara, T. Momma, T. Osaka, J. Power Sources 336 (2016) 203–211. [8] H. Nara, T. Yokoshima, M. Otaki, T. Momma, T. Osaka, Electrochim. Acta 110 (2013) 403–410. [9] M.-S. Balogun, W. Qiu, Y. Luo, H. Meng, W. Mai, A. Onasanya, T.K. Olaniyi, Y. Tong, Nano Res. 9 (2016) 2823–2851. [10] H. Sun, X. He, J. Ren, J. Li, C. Jiang, C. Wan, Electrochim. Acta 52 (2007) 4312– 4316. [11] Y.-S. Han, J.-Y. Lee, Electrochim. Acta 48 (2003) 1073–1079.