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Antimony Sulphide Nanorods Decorated onto Reduced Graphene Oxide Based Anodes for Sodium-Ion Battery
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ScienceDirect Materials Today: Proceedings 21 (2020) 1899–1904
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ISFM-2018
Antimony Sulphide Nanorods Decorated onto Reduced Graphene Oxide Based Anodes for Sodium-Ion Battery Love Dashairya, and Partha Saha* Department of Ceramic Engineering, National Institute of Technology, Rourkela, Odisha-769008, India
Abstract Sb2S3 and Sb2S3/rGO nanorods were developed by a facile hydrothermal route and thoroughly investigated for their crystallinity, and phase evolution using XRD, FESEM/EDS, and FTIR analysis. The electrochemical sodium-ion charge storage behavior of the synthesized anodes was examined in CR-2032 type coin cells using galvanostatic charge-discharge measurements at a current of ~50 mAg-1. The preliminary galvanostatic cycling data shows that Sb2S3, and Sb2S3/rGO exhibits a decent discharge and charge capacity of ~601 mAhg-1, ~256 mAhg-1, 528 mAh.g-1 , and ~399 mAh.g-1, respectively, for the first cycle with Coulombic efficiency ~42.6% and ~75.6%. It was found that rGO incorporation can salvage the capacity loss and improved Coulombic efficiency in the first cycle. However, the rapid capacity fades in the subsequent cycles warrant further in-depth studies to get an idea about the Na-ion storage behavior in the electrodes. © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications. Keywords: Antimony sulfide; Nanorods; Hydrothermal method; Sodium-ion battery
1. Introduction Energy storage devices such as rechargeable batteries have attracted widespread uses for power electronics since last few decades [1-4]. In this regard, maximum efforts have been spent to develop state-of-the-art lithium-ion batteries (LIB) starting from mobile devices to electric vehicles owing to its high energy density, rate capability, and
* Corresponding author. Tel.: +91-661-246-2211; fax: +91-661-247-2926. E-mail address: [email protected], [email protected] (Partha Saha) 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications.
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long cycle life [1, 5]. However, present LIB technology doesn’t fully satisfy the stringent requirements for largescale EES due to its inherent safety concern, and high manufacturing cost [6]. Since the last decade, sodium-ion batteries (SIB) appeared as a possible alternative to the technologically superior Li-ion system mainly due to earth abundance of sodium-bearing compounds (sodium abundance on earth, ∼2.6 weight percent compare to lithium ∼0.0007 weight percent in earth’s crust) and cost-effectiveness (equivalent cost in dollar for: Na: 0.075, Li: 0.50) [7, 8]. To develop SIBs, metallic sodium should be alloyed/de-alloyed with suitable negative intercalation hosts analogous to graphite used for LIBs [9]. However, sodium cannot be reversibly alloyed/de-alloyed with graphitic carbon and silicon and form sodium-carbon, and sodium-silicon alloy prompted the investigations for alternative anodes [10, 11]. Recently, various anodes have been explored including metal oxides, and sulfides [12]. Metal oxides generally deliver relatively small reversible capacities ~400 mAhg-1 for SIBs, in spite of their high theoretical capacities [13-17]. On the contrary, metal sulfides viz. MoS2, SnS2, Bi2S3 and Sb2S3 have shown promising electrochemical performance [18-21]. Among various metal sulfides, Sb2S3 appeared as a potential anode owing to its excellent theoretical capacity (~946 mAh.g−1) [22]. Sb2S3 undergoes conversion, and alloying reactions with metallic sodium during the discharge cycle and the reactions can be summarized as below [22]. Conversion: Sb2S3 + 6Na+ + 6e- → 2Sb + 3Na2S Alloying: 2Sb + 6Na+ + 6e- → 2Na3Sb During charge/de-alloying in the opposite cycle, Sb2S3 formation occurs by the reaction of Na2S with Sb [23]. Also, Sb2S3 can offer higher theoretical capacity than Sb (660 mAhg-1) due to lower mass of sulfur atoms which is a potential benefit in terms of the energy density of a cell. However, a critical drawback of any sulfide system is the inherently sluggish electronic conductivity which impairs the ability of fast Na-ion diffusion and reaction kinetics [3, 9, 24, 25]. In addition, the combination of conversion and alloying reactions associated with colossal volume expansion (~293%) are the main reasons for electrode pulverization and associated capacity fade [3, 9, 24, 25]. In addition, the incomplete reaction between the Na2S particles and Sb during charge cycle invariably decreases the actual capacity of the electrodes. One possible solution to counter the large volume expansion associated with Sb2S3 anode is to use the inactive matrix viz. carbonaceous materials as buffering agents that can accommodate the large volumetric strains [9, 26-28]. Thus, it is imperative to modify the Sb2S3 structure by introducing a carbonaceous matrix during synthesis [27]. In the present work, Sb2S3 and Sb2S3/rGO based anodes were explored for SIB. Sb2S3 and Sb2S3/rGO were synthesized via one-pot hydrothermal route using graphite oxide, antimony trichloride and thioacetamide as the precursors. Sb2S3/rGO anode was examined in a 2025-coin cell, which demonstrated improved discharge and charge capacity compared to the pristine Sb2S3 anode. 2. Experimental method 2.1. Sb2S3 and Sb2S3/rGO synthesis Graphene oxide was synthesized by chemical oxidation and exfoliation of graphite by modified Hummer’s method [29, 30]. First, 100 mg of GO was suspended in 100 mL of de-ionized water for 20 min ultrasonication. Second, 2 mmol of antimony trichloride (SbCl3, 99%, HiMedia) and 3 mmol of thioacetamide (C2H5NS, 99%, HiMedia) were dissolved into sonicated GO solution by homogeneous stirring for 30 min. After that, the solution was placed in an autoclave (200 mL capacity), sealed and kept at 180°C for 24h. After completion, the solution was cooled to room temperature, and a solid paste was obtained by centrifugation, followed by washing with DI water/propanol multiple times. Finally, the paste was kept under vacuum oven ~60°C for 12h. Pristine Sb2S3 was synthesized by a similar method in the absence of GO solution. 2.2. Materials characterization X-ray diffraction (XRD) was performed using Philips-Rigaku-Ultima-IV system using CuKα radiation (λcu = 1.5406 Å). Microstructure and semi-quantitative phase analysis were performed using a field-emission scanning electron microscope (FESEM) along with energy-dispersive spectroscopy (EDS) (Nova NanoSEM FEI450) operating at 10 kV. Fourier transform infrared spectroscopy (FTIR) (Perkin Elmer Spectrum version 10.4.00)
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spectra were collected between 400-4000 cm–1 wavenumber range Thermogravimetric (TG) analysis of the powder samples was carried out by a Netzsch TG209 F3 Tarsus thermal analyzer from RT to 800°C using a constant heating rate of 10°C/min in Argon environment. 2.3. Electrochemistry The slurry for the composite electrode was prepared using 80 wt. % of active mass (−325 mesh), 10 wt. % SuperP, 10 wt. % polyvinylidene fluoride (PVDF, 99% Sigma-Aldrich) binder along with N-methylpyrrolidinone (NMP, 99% Sigma-Aldrich) solvent by wet mixing. The slurry thus obtained was tape casted on a copper mesh, followed by drying at 70°C in a vacuum oven for 24h. The electrode further punched into 11.28 mm diameter of electrode disks with active mas loading ~4 mg/cm2. Electrodes were prepared in a CR2032 coin cells using metallic sodium as the counter/reference electrode, punched composite electrode as working electrodes, separated by a Celgard® separator in 1 molar sodium perchlorate anhydrous (NaClO4 in ethylene carbonate: dimethyl carbonate, 1:2 volumetric ratio) electrolyte solution. The coin cells were fabricated inside an MBraun glove box which maintained <0.1 ppm each of O2 and H2O to avoid any exposure of electrodes/electrolyte in the air. Cyclic voltammetry (sweep rate ∼0.05 Vs–1) and galvanostatic electrochemical test (current rate ~50 mAg-1) were performed using BST8-MA (MTI Corporation, USA) battery tester within 0.01- 2.5 V. 3. Results and Discussion Figure 1 illustrates the XRD pattern of Sb2S3 and Sb2S3/rGO, where the Braggs diffraction lines can be indexed with the standard ICDD database (96-900-7241) of Sb2S3 [4]. The XRD peaks of rGO appeared at ~26° of 2θ with the interlayer spacing (d002) corresponds to ~3.36 Å, which is the characteristic diffraction peak of rGO [30, 31]. Also, the formation of rGO sheets on to Sb2S3 was also evident due to an increase in the relative intensity of Sb2S3/rGO peak observed at ~26.53°. Crystallite size of Sb2S3 and Sb2S3/rGO was calculated as ~43.59 nm and ~62.26 nm, respectively, using the Scherrer’s equation. FESEM images (see Fig. 2a) show that Sb2S3 and Sb2S3/rGO form nanorods morphology in haystack-like structure with diameter ~0.21-4 µm and length ~3-5 µm [23]. It was also evident that Sb2S3 nanorods anchored on to wrinkled layers of rGO sheet. Elemental X-ray mapping of Sb2S3/rGO indicates that the as-synthesized Sb2S3/rGO possess Sb, S, C, and O (see Fig. 2b). Also, the weight percentage of Sb, S, C, and O was found ~60.22, ~19.38, ~16.75, and ~3.64%, respectively, in the stoichiometric ratio for Sb2S3/rGO.
Fig. 1 X-ray diffraction patterns of rGO, Sb2S3, and Sb2S3/rGO.
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Fig. 2 (a) FESEM images of Sb2S3 and Sb2S3/rGO, and (b) elemental X-ray mapping, EDS spectra displaying the distribution of elements in Sb2S3/rGO.
FTIR pattern of Sb2S3 shows standard absorption peaks at ~538, ~634, ~738, ~1633 cm-1 due to the formation of Sb-S bonds as shown in Fig. 3a [32]. However, the presence of rGO on to the Sb2S3 surface reduced the intensity of Sb-S absorption peaks in the FTIR pattern of Sb2S3/rGO (see Fig. 3a) [31]. It was observed that rGO peaks at ~1190, ~1571 and ~1718 cm-1 significantly appeared into FTIR spectra of Sb2S3/rGO due to chemically attachment of Sb2S3 onto the rGO sheets by hydrothermal treatment [33]. Also, FTIR pattern of Sb2S3/rGO displayed absorption peaks at ~1571 cm-1 due to C=C skeletal vibration which confirms that aromatic sp2 hybrid carbon skeleton is restored for rGO onto Sb2S3 nanorods [30]. Thermal stability of Sb2S3 and Sb2S3/rGO was examined by TG analysis as shown in Fig. 3b. TG pattern of Sb2S3/rGO showed mass loss ~5% at temperature range 150 to 460°C due to adsorbed water molecules removal, and evaporation of hydroxyl group of rGO sheets [34]. It is to be noted that mass loss related to sulfur vaporization and melting of the Sb2S3 was not observed up to 450°C [23, 35]. Therefore, the amount of Sb2S3 and rGO in the Sb2S3/rGO composite was determined ~95 % and ~5%, respectively, based on the following equation [36]. 100 Sb2S3 (wt. %) = /
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Fig. 3 (a) FTIR spectra of rGO, Sb2S3, and Sb2S3/rGO, and (b) TG analysis of Sb2S3 and Sb2S3/rGO.
Cyclic voltammetry of Sb2S3/rGO anode was performed at a sweep rate of ~0.5 mVs−1 within 0.01−2.0V voltage versus Na/Na+ as shown in Fig. 4a. For the Na-ion alloying, the peaks observed at ~0.4V and ~0.7V (see Fig. 4a) akin to the values reported in the literature [4]. The first peak appears due to formation of Sb nanoparticles and Na2S by Na-ion reaction with Sb2S3 via conversion reaction and the second peak correlate with the formation of NaSb and Na3Sb phase(s) by alloying reaction of Sb with Na. Also, the first anodic scan shows small peaks at ~0.8V and ~1.35V correspond to de-sodiation reactions [23].
Fig. 4 (a) Cyclic voltammetry of Sb2S3/rGO electrode at a scan rate 0.5 mVs−1, charge/discharge profiles of (b) Sb2S3 and, (c) Sb2S3/rGO at the current density of 50 mAg−1 for first five cycles.
Fig. 4b and 4c illustrate the charge-discharge capacity versus voltage profile of the Sb2S3 and Sb2S3/rGO electrodes respectively, within the potential of 0.01–2.5V versus Na/Na+. The first cycle sodiation (discharge) and de-sodiation (charge) capacity of Sb2S3 was observed ~601 mAh.g-1 and ~256 mAh.g-1, respectively, with Coulombic efficiency ~42.6%. Between the second to fifth cycle the discharge and charge capacity was ~186 mAh.g-1, ~128 mAh.g-1; ~112 mAh.g-1, ~94 mAh.g-1; ~75 mAh.g-1, ~68 mAh.g-1; ~56 mAh.g-1, ~53 mAh.g-1; respectively, with Columbic efficiency ~68.8%, ~83.9%, ~90.6%, and ~94.6%, respectively. The huge capacity drop and high irreversible loss from the 1st cycle onwards likely originate from the sulfur matrix and inactive SEI layer formation as well as the colossal volume expansion associated with the formation of NaSb, and Na3Sb intermetallic phase(s) [23, 25, 37]. However, the incorporation of rGO in the Sb2S3 matrix can salvage the capacity drop and improved Coulombic efficiency. The first cycle sodiation (discharge) and de-sodiation (charge)capacity of Sb2S3/rGO was observed ~528 mAh.g-1, and ~399 mAh.g-1, respectively, with Coulombic efficiency 75.6%, Between the second to fifth cycle the discharge and charge capacity of Sb2S3/rGO was ~405 mAh.g-1, ~325 mAh.g-1 ~334 mAh.g-1, ~277 mAh.g-1 ~274 mAh.g-1, ~242 mAh.g-1 ~242 mAh.g-1, ~220 mAh.g-1; respectively, with
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Columbic efficiency ~80.2%, ~82.9%, ~88.3%, and ~90.9%, respectively. The above results suggest that Sb2S3/rGO electrode can be a potential anode with good electrochemical reversibility than Sb2S3. 4. Conclusions We have successfully showcased a facile one-step hydrothermal route for the synthesis of Sb2S3 nanorods and Sb2S3/rGO composite using antimony trichloride, thioacetamide and GO solution as precursors. The formation of phase pure Sb2S3 nanorods bundle growing onto the reduced graphene nanosheet was confirmed by XRD analysis. The nanorods were formed with diameter ~0.21-4 µm and length ~3-5 µm. Galvanostatic cycling showed that rGO incorporation in the Sb2S3 nanorod structure improved the Na-ion charge storage behavior and Coulombic efficiency compare to pristine Sb2S3 in the first cycle. It was observed that Colombic efficiency for Sb2S3/rGO electrode gradually improved from ~75% in the first cycle to ~95% in the fifth cycle with concomitant decay in capacity. The rapid capacity fades as the cycle progresses warrants further in-depth studies using in-situ XRD, XPS, electrochemical impedance spectroscopy to delve into detail charge storage behavior of the electrodes. Acknowledgments Partha Saha acknowledges the financial grant received from Department of Science and Technology, Science and Engineering Research Board (DST-SERB) (Grant number ECR/2016/000959). References [1] S. Goriparti, E. Miele, F. De Angelis, E. Di Fabrizio, R.P. Zaccaria, C. Capiglia, J. Power Sources. 257 (2014) 421-443. [2] S.W. Kim, D.H. Seo, X. Ma, G. Ceder, K. Kang, Adv. Energy Mater. 2 (2012) 710-721. [3] Y. Kim, K.H. Ha, S.M. Oh, K.T. Lee, Chemistry-A European J. 20 (2014) 11980-11992. [4] A.S. Hameed, M. Reddy, J.L. Chen, B. Chowdari, J.J. Vittal, ACS Sustainable Chemistry & Engineering, 4 (2016) 2479-2486. [5] V. Etacheri, R. Marom, R. Elazari, G. Salitra, D. Aurbach, Energy Environ. Sci. 4 (2011) 3243-3262. [6] C. Zhao, Y. Lu, Y. Li, L. Jiang, X. Rong, Y.S. Hu, H. Li, L. Chen, Small Methods, (2017). [7] B.L. Ellis, L.F. Nazar, Current Opinion in Solid State Mater. Sci. 16 (2012) 168-177. [8] P. Saha, P.H. Jampani, M.K. Datta, D. Hong, C.U. Okoli, A. Manivannan, P.N. Kumta, J. Phys. Chem. C. 119 (2015) 5771-5782. [9] M.-S. Balogun, Y. Luo, W. Qiu, P. Liu, Y. Tong, Carbon, 98 (2016) 162-178. [10] K. Kubota, S. Komaba, J. of The Electrochem. Soc, 162 (2015) A2538-A2550. [11] M.K. Datta, R. Epur, P. Saha, K. Kadakia, S.K. Park, P.N. Kumta, J. Power Sources 225 (2013) 316-322. [12] H. Kang, Y. Liu, K. Cao, Y. Zhao, L. Jiao, Y. Wang, H. Yuan, J. Mater. Chem. A. 3 (2015) 17899-17913. [13] S. Komaba, T. Mikumo, N. Yabuuchi, A. Ogata, H. Yoshida, Y. Yamada, J. Electrochem. Soc. 157 (2010) A60. [14] Y. Liu, Z. Cheng, H. Sun, H. Arandiyan, J. Li, M. Ahmad, J. Power Sources, 273 (2015) 878-884. [15] S. Hariharan, K. Saravanan, P. Balaya, Electrochem. Comm. 31 (2013) 5-9. [16] Y. Liu, B.H. Zhang, S.Y. Xiao, L.L. Liu, Z.B. Wen, Y.P. Wu, Electrochimi. Acta 116 (2014) 512-517. [17] W. Sun, X. Rui, J. Zhu, L. Yu, Y. Zhang, Z. Xu, S. Madhavi, Q. Yan, J. Power Sources 274 (2015) 755-761. [18] W. Yang, H. Wang, T. Liu, L. Gao, Mater. Letters 167 (2016) 102-105. [19] S.M. Hwang, J. Kim, Y. Kim, Y. Kim, J. Mater. Chem. A. 4 (2016) 17946-17951. [20] X. Xie, Z. Ao, D. Su, J. Zhang, G. Wang, Adv. Funct. Mater. 25 (2015) 1393-1403. [21] B. Qu, C. Ma, G. Ji, C. Xu, J. Xu, Y.S. Meng, T. Wang, J.Y. Lee, Adv. Mater. 26 (2014) 3854-3859. [22] S. Wang, S. Yuan, Y.B. Yin, Y.H. Zhu, X.B. Zhang, J.M. Yan, Particle Particle Sys. Char. 33 (2016) 493-499. [23] H. Hou, M. Jing, Z. Huang, Y. Yang, Y. Zhang, J. Chen, Z. Wu, X. Ji, ACS Applied Mater. Interface 7 (2015) 19362-19369. [24] J.-H. Choi, C.-W. Ha, H.-Y. Choi, H.-C. Shin, C.-M. Park, Y.-N. Jo, S.-M. Lee, Electrochimi. Acta 210 (2016) 588-595. [25] Y. Zhu, P. Nie, L. Shen, S. Dong, Q. Sheng, H. Li, H. Luo, X. Zhang, Nanoscale 7 (2015) 3309-3315. [26] Y. Denis, P.V. Prikhodchenko, C.W. Mason, S.K. Batabyal, J. Gun, S. Sladkevich, A.G. Medvedev, O. Lev, Nature Comm. 4 (2013) 2922. [27] F. Wu, X. Guo, M. Li, H. Xu, Ceramic International 43 (2017) 6019-6023. [28] S.K. Behera, Chem. Comm. 47 (2011) 10371-10373. [29] W.S. Hummers, R.E. Offeman, J. Amer. Chem. Soc. 80 (1958) 1339-1339. [30] P. Saha, L. Dashairya, J. Porous Mater. (2018) 1475-1488. [31] L. Dashairya, M. Sharma, S. Basu, P. Saha, J. Alloys Compounds 735 (2018) 234-245. [32] C. Pilapong, T. Thongtem, S. Thongtem, J. Alloys Compounds 507 (2010) L38-L42. [33] L. Dashairya, M. Rout, P. Saha, Advanced Composites Hybrid Mater. 1 (2018) 135-148. [34] S. Abdolhosseinzadeh, H. Asgharzadeh, H. Seop Kim, Scientific Rep. 5 (2015) 10160. [35] G. Murtaza, M. Akhtar, M. Azad Malik, P. O’Brien, N. Revaprasadu, Mater. Sci. Semi. Proc. 40 (2015) 643-649. [36] Y. Xu, Q. Liu, Y. Zhu, Y. Liu, A. Langrock, M.R. Zachariah, C. Wang, Nano Lett. 13 (2013) 470-474. [37] Y. Zhao, A. Manthiram, Chem. Comm. 51 (2015) 13205-13208.
ScienceDirect Materials Today: Proceedings 21 (2020) 1899–1904
www.materialstoday.com/proceedings
ISFM-2018
Antimony Sulphide Nanorods Decorated onto Reduced Graphene Oxide Based Anodes for Sodium-Ion Battery Love Dashairya, and Partha Saha* Department of Ceramic Engineering, National Institute of Technology, Rourkela, Odisha-769008, India
Abstract Sb2S3 and Sb2S3/rGO nanorods were developed by a facile hydrothermal route and thoroughly investigated for their crystallinity, and phase evolution using XRD, FESEM/EDS, and FTIR analysis. The electrochemical sodium-ion charge storage behavior of the synthesized anodes was examined in CR-2032 type coin cells using galvanostatic charge-discharge measurements at a current of ~50 mAg-1. The preliminary galvanostatic cycling data shows that Sb2S3, and Sb2S3/rGO exhibits a decent discharge and charge capacity of ~601 mAhg-1, ~256 mAhg-1, 528 mAh.g-1 , and ~399 mAh.g-1, respectively, for the first cycle with Coulombic efficiency ~42.6% and ~75.6%. It was found that rGO incorporation can salvage the capacity loss and improved Coulombic efficiency in the first cycle. However, the rapid capacity fades in the subsequent cycles warrant further in-depth studies to get an idea about the Na-ion storage behavior in the electrodes. © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications. Keywords: Antimony sulfide; Nanorods; Hydrothermal method; Sodium-ion battery
1. Introduction Energy storage devices such as rechargeable batteries have attracted widespread uses for power electronics since last few decades [1-4]. In this regard, maximum efforts have been spent to develop state-of-the-art lithium-ion batteries (LIB) starting from mobile devices to electric vehicles owing to its high energy density, rate capability, and
* Corresponding author. Tel.: +91-661-246-2211; fax: +91-661-247-2926. E-mail address: [email protected], [email protected] (Partha Saha) 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications.
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long cycle life [1, 5]. However, present LIB technology doesn’t fully satisfy the stringent requirements for largescale EES due to its inherent safety concern, and high manufacturing cost [6]. Since the last decade, sodium-ion batteries (SIB) appeared as a possible alternative to the technologically superior Li-ion system mainly due to earth abundance of sodium-bearing compounds (sodium abundance on earth, ∼2.6 weight percent compare to lithium ∼0.0007 weight percent in earth’s crust) and cost-effectiveness (equivalent cost in dollar for: Na: 0.075, Li: 0.50) [7, 8]. To develop SIBs, metallic sodium should be alloyed/de-alloyed with suitable negative intercalation hosts analogous to graphite used for LIBs [9]. However, sodium cannot be reversibly alloyed/de-alloyed with graphitic carbon and silicon and form sodium-carbon, and sodium-silicon alloy prompted the investigations for alternative anodes [10, 11]. Recently, various anodes have been explored including metal oxides, and sulfides [12]. Metal oxides generally deliver relatively small reversible capacities ~400 mAhg-1 for SIBs, in spite of their high theoretical capacities [13-17]. On the contrary, metal sulfides viz. MoS2, SnS2, Bi2S3 and Sb2S3 have shown promising electrochemical performance [18-21]. Among various metal sulfides, Sb2S3 appeared as a potential anode owing to its excellent theoretical capacity (~946 mAh.g−1) [22]. Sb2S3 undergoes conversion, and alloying reactions with metallic sodium during the discharge cycle and the reactions can be summarized as below [22]. Conversion: Sb2S3 + 6Na+ + 6e- → 2Sb + 3Na2S Alloying: 2Sb + 6Na+ + 6e- → 2Na3Sb During charge/de-alloying in the opposite cycle, Sb2S3 formation occurs by the reaction of Na2S with Sb [23]. Also, Sb2S3 can offer higher theoretical capacity than Sb (660 mAhg-1) due to lower mass of sulfur atoms which is a potential benefit in terms of the energy density of a cell. However, a critical drawback of any sulfide system is the inherently sluggish electronic conductivity which impairs the ability of fast Na-ion diffusion and reaction kinetics [3, 9, 24, 25]. In addition, the combination of conversion and alloying reactions associated with colossal volume expansion (~293%) are the main reasons for electrode pulverization and associated capacity fade [3, 9, 24, 25]. In addition, the incomplete reaction between the Na2S particles and Sb during charge cycle invariably decreases the actual capacity of the electrodes. One possible solution to counter the large volume expansion associated with Sb2S3 anode is to use the inactive matrix viz. carbonaceous materials as buffering agents that can accommodate the large volumetric strains [9, 26-28]. Thus, it is imperative to modify the Sb2S3 structure by introducing a carbonaceous matrix during synthesis [27]. In the present work, Sb2S3 and Sb2S3/rGO based anodes were explored for SIB. Sb2S3 and Sb2S3/rGO were synthesized via one-pot hydrothermal route using graphite oxide, antimony trichloride and thioacetamide as the precursors. Sb2S3/rGO anode was examined in a 2025-coin cell, which demonstrated improved discharge and charge capacity compared to the pristine Sb2S3 anode. 2. Experimental method 2.1. Sb2S3 and Sb2S3/rGO synthesis Graphene oxide was synthesized by chemical oxidation and exfoliation of graphite by modified Hummer’s method [29, 30]. First, 100 mg of GO was suspended in 100 mL of de-ionized water for 20 min ultrasonication. Second, 2 mmol of antimony trichloride (SbCl3, 99%, HiMedia) and 3 mmol of thioacetamide (C2H5NS, 99%, HiMedia) were dissolved into sonicated GO solution by homogeneous stirring for 30 min. After that, the solution was placed in an autoclave (200 mL capacity), sealed and kept at 180°C for 24h. After completion, the solution was cooled to room temperature, and a solid paste was obtained by centrifugation, followed by washing with DI water/propanol multiple times. Finally, the paste was kept under vacuum oven ~60°C for 12h. Pristine Sb2S3 was synthesized by a similar method in the absence of GO solution. 2.2. Materials characterization X-ray diffraction (XRD) was performed using Philips-Rigaku-Ultima-IV system using CuKα radiation (λcu = 1.5406 Å). Microstructure and semi-quantitative phase analysis were performed using a field-emission scanning electron microscope (FESEM) along with energy-dispersive spectroscopy (EDS) (Nova NanoSEM FEI450) operating at 10 kV. Fourier transform infrared spectroscopy (FTIR) (Perkin Elmer Spectrum version 10.4.00)
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spectra were collected between 400-4000 cm–1 wavenumber range Thermogravimetric (TG) analysis of the powder samples was carried out by a Netzsch TG209 F3 Tarsus thermal analyzer from RT to 800°C using a constant heating rate of 10°C/min in Argon environment. 2.3. Electrochemistry The slurry for the composite electrode was prepared using 80 wt. % of active mass (−325 mesh), 10 wt. % SuperP, 10 wt. % polyvinylidene fluoride (PVDF, 99% Sigma-Aldrich) binder along with N-methylpyrrolidinone (NMP, 99% Sigma-Aldrich) solvent by wet mixing. The slurry thus obtained was tape casted on a copper mesh, followed by drying at 70°C in a vacuum oven for 24h. The electrode further punched into 11.28 mm diameter of electrode disks with active mas loading ~4 mg/cm2. Electrodes were prepared in a CR2032 coin cells using metallic sodium as the counter/reference electrode, punched composite electrode as working electrodes, separated by a Celgard® separator in 1 molar sodium perchlorate anhydrous (NaClO4 in ethylene carbonate: dimethyl carbonate, 1:2 volumetric ratio) electrolyte solution. The coin cells were fabricated inside an MBraun glove box which maintained <0.1 ppm each of O2 and H2O to avoid any exposure of electrodes/electrolyte in the air. Cyclic voltammetry (sweep rate ∼0.05 Vs–1) and galvanostatic electrochemical test (current rate ~50 mAg-1) were performed using BST8-MA (MTI Corporation, USA) battery tester within 0.01- 2.5 V. 3. Results and Discussion Figure 1 illustrates the XRD pattern of Sb2S3 and Sb2S3/rGO, where the Braggs diffraction lines can be indexed with the standard ICDD database (96-900-7241) of Sb2S3 [4]. The XRD peaks of rGO appeared at ~26° of 2θ with the interlayer spacing (d002) corresponds to ~3.36 Å, which is the characteristic diffraction peak of rGO [30, 31]. Also, the formation of rGO sheets on to Sb2S3 was also evident due to an increase in the relative intensity of Sb2S3/rGO peak observed at ~26.53°. Crystallite size of Sb2S3 and Sb2S3/rGO was calculated as ~43.59 nm and ~62.26 nm, respectively, using the Scherrer’s equation. FESEM images (see Fig. 2a) show that Sb2S3 and Sb2S3/rGO form nanorods morphology in haystack-like structure with diameter ~0.21-4 µm and length ~3-5 µm [23]. It was also evident that Sb2S3 nanorods anchored on to wrinkled layers of rGO sheet. Elemental X-ray mapping of Sb2S3/rGO indicates that the as-synthesized Sb2S3/rGO possess Sb, S, C, and O (see Fig. 2b). Also, the weight percentage of Sb, S, C, and O was found ~60.22, ~19.38, ~16.75, and ~3.64%, respectively, in the stoichiometric ratio for Sb2S3/rGO.
Fig. 1 X-ray diffraction patterns of rGO, Sb2S3, and Sb2S3/rGO.
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Fig. 2 (a) FESEM images of Sb2S3 and Sb2S3/rGO, and (b) elemental X-ray mapping, EDS spectra displaying the distribution of elements in Sb2S3/rGO.
FTIR pattern of Sb2S3 shows standard absorption peaks at ~538, ~634, ~738, ~1633 cm-1 due to the formation of Sb-S bonds as shown in Fig. 3a [32]. However, the presence of rGO on to the Sb2S3 surface reduced the intensity of Sb-S absorption peaks in the FTIR pattern of Sb2S3/rGO (see Fig. 3a) [31]. It was observed that rGO peaks at ~1190, ~1571 and ~1718 cm-1 significantly appeared into FTIR spectra of Sb2S3/rGO due to chemically attachment of Sb2S3 onto the rGO sheets by hydrothermal treatment [33]. Also, FTIR pattern of Sb2S3/rGO displayed absorption peaks at ~1571 cm-1 due to C=C skeletal vibration which confirms that aromatic sp2 hybrid carbon skeleton is restored for rGO onto Sb2S3 nanorods [30]. Thermal stability of Sb2S3 and Sb2S3/rGO was examined by TG analysis as shown in Fig. 3b. TG pattern of Sb2S3/rGO showed mass loss ~5% at temperature range 150 to 460°C due to adsorbed water molecules removal, and evaporation of hydroxyl group of rGO sheets [34]. It is to be noted that mass loss related to sulfur vaporization and melting of the Sb2S3 was not observed up to 450°C [23, 35]. Therefore, the amount of Sb2S3 and rGO in the Sb2S3/rGO composite was determined ~95 % and ~5%, respectively, based on the following equation [36]. 100 Sb2S3 (wt. %) = /
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Fig. 3 (a) FTIR spectra of rGO, Sb2S3, and Sb2S3/rGO, and (b) TG analysis of Sb2S3 and Sb2S3/rGO.
Cyclic voltammetry of Sb2S3/rGO anode was performed at a sweep rate of ~0.5 mVs−1 within 0.01−2.0V voltage versus Na/Na+ as shown in Fig. 4a. For the Na-ion alloying, the peaks observed at ~0.4V and ~0.7V (see Fig. 4a) akin to the values reported in the literature [4]. The first peak appears due to formation of Sb nanoparticles and Na2S by Na-ion reaction with Sb2S3 via conversion reaction and the second peak correlate with the formation of NaSb and Na3Sb phase(s) by alloying reaction of Sb with Na. Also, the first anodic scan shows small peaks at ~0.8V and ~1.35V correspond to de-sodiation reactions [23].
Fig. 4 (a) Cyclic voltammetry of Sb2S3/rGO electrode at a scan rate 0.5 mVs−1, charge/discharge profiles of (b) Sb2S3 and, (c) Sb2S3/rGO at the current density of 50 mAg−1 for first five cycles.
Fig. 4b and 4c illustrate the charge-discharge capacity versus voltage profile of the Sb2S3 and Sb2S3/rGO electrodes respectively, within the potential of 0.01–2.5V versus Na/Na+. The first cycle sodiation (discharge) and de-sodiation (charge) capacity of Sb2S3 was observed ~601 mAh.g-1 and ~256 mAh.g-1, respectively, with Coulombic efficiency ~42.6%. Between the second to fifth cycle the discharge and charge capacity was ~186 mAh.g-1, ~128 mAh.g-1; ~112 mAh.g-1, ~94 mAh.g-1; ~75 mAh.g-1, ~68 mAh.g-1; ~56 mAh.g-1, ~53 mAh.g-1; respectively, with Columbic efficiency ~68.8%, ~83.9%, ~90.6%, and ~94.6%, respectively. The huge capacity drop and high irreversible loss from the 1st cycle onwards likely originate from the sulfur matrix and inactive SEI layer formation as well as the colossal volume expansion associated with the formation of NaSb, and Na3Sb intermetallic phase(s) [23, 25, 37]. However, the incorporation of rGO in the Sb2S3 matrix can salvage the capacity drop and improved Coulombic efficiency. The first cycle sodiation (discharge) and de-sodiation (charge)capacity of Sb2S3/rGO was observed ~528 mAh.g-1, and ~399 mAh.g-1, respectively, with Coulombic efficiency 75.6%, Between the second to fifth cycle the discharge and charge capacity of Sb2S3/rGO was ~405 mAh.g-1, ~325 mAh.g-1 ~334 mAh.g-1, ~277 mAh.g-1 ~274 mAh.g-1, ~242 mAh.g-1 ~242 mAh.g-1, ~220 mAh.g-1; respectively, with
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Columbic efficiency ~80.2%, ~82.9%, ~88.3%, and ~90.9%, respectively. The above results suggest that Sb2S3/rGO electrode can be a potential anode with good electrochemical reversibility than Sb2S3. 4. Conclusions We have successfully showcased a facile one-step hydrothermal route for the synthesis of Sb2S3 nanorods and Sb2S3/rGO composite using antimony trichloride, thioacetamide and GO solution as precursors. The formation of phase pure Sb2S3 nanorods bundle growing onto the reduced graphene nanosheet was confirmed by XRD analysis. The nanorods were formed with diameter ~0.21-4 µm and length ~3-5 µm. Galvanostatic cycling showed that rGO incorporation in the Sb2S3 nanorod structure improved the Na-ion charge storage behavior and Coulombic efficiency compare to pristine Sb2S3 in the first cycle. It was observed that Colombic efficiency for Sb2S3/rGO electrode gradually improved from ~75% in the first cycle to ~95% in the fifth cycle with concomitant decay in capacity. The rapid capacity fades as the cycle progresses warrants further in-depth studies using in-situ XRD, XPS, electrochemical impedance spectroscopy to delve into detail charge storage behavior of the electrodes. Acknowledgments Partha Saha acknowledges the financial grant received from Department of Science and Technology, Science and Engineering Research Board (DST-SERB) (Grant number ECR/2016/000959). References [1] S. Goriparti, E. Miele, F. De Angelis, E. Di Fabrizio, R.P. Zaccaria, C. Capiglia, J. Power Sources. 257 (2014) 421-443. [2] S.W. Kim, D.H. Seo, X. Ma, G. Ceder, K. Kang, Adv. Energy Mater. 2 (2012) 710-721. [3] Y. Kim, K.H. Ha, S.M. Oh, K.T. Lee, Chemistry-A European J. 20 (2014) 11980-11992. [4] A.S. Hameed, M. Reddy, J.L. Chen, B. Chowdari, J.J. Vittal, ACS Sustainable Chemistry & Engineering, 4 (2016) 2479-2486. [5] V. Etacheri, R. Marom, R. Elazari, G. Salitra, D. Aurbach, Energy Environ. Sci. 4 (2011) 3243-3262. [6] C. Zhao, Y. Lu, Y. Li, L. Jiang, X. Rong, Y.S. Hu, H. Li, L. Chen, Small Methods, (2017). [7] B.L. Ellis, L.F. Nazar, Current Opinion in Solid State Mater. Sci. 16 (2012) 168-177. [8] P. Saha, P.H. Jampani, M.K. Datta, D. Hong, C.U. Okoli, A. Manivannan, P.N. Kumta, J. Phys. Chem. C. 119 (2015) 5771-5782. [9] M.-S. Balogun, Y. Luo, W. Qiu, P. Liu, Y. Tong, Carbon, 98 (2016) 162-178. [10] K. Kubota, S. Komaba, J. of The Electrochem. Soc, 162 (2015) A2538-A2550. [11] M.K. Datta, R. Epur, P. Saha, K. Kadakia, S.K. Park, P.N. Kumta, J. Power Sources 225 (2013) 316-322. [12] H. Kang, Y. Liu, K. Cao, Y. Zhao, L. Jiao, Y. Wang, H. Yuan, J. Mater. Chem. A. 3 (2015) 17899-17913. [13] S. Komaba, T. Mikumo, N. Yabuuchi, A. Ogata, H. Yoshida, Y. Yamada, J. Electrochem. Soc. 157 (2010) A60. [14] Y. Liu, Z. Cheng, H. Sun, H. Arandiyan, J. Li, M. Ahmad, J. Power Sources, 273 (2015) 878-884. [15] S. Hariharan, K. Saravanan, P. Balaya, Electrochem. Comm. 31 (2013) 5-9. [16] Y. Liu, B.H. Zhang, S.Y. Xiao, L.L. Liu, Z.B. Wen, Y.P. Wu, Electrochimi. Acta 116 (2014) 512-517. [17] W. Sun, X. Rui, J. Zhu, L. Yu, Y. Zhang, Z. Xu, S. Madhavi, Q. Yan, J. Power Sources 274 (2015) 755-761. [18] W. Yang, H. Wang, T. Liu, L. Gao, Mater. Letters 167 (2016) 102-105. [19] S.M. Hwang, J. Kim, Y. Kim, Y. Kim, J. Mater. Chem. A. 4 (2016) 17946-17951. [20] X. Xie, Z. Ao, D. Su, J. Zhang, G. Wang, Adv. Funct. Mater. 25 (2015) 1393-1403. [21] B. Qu, C. Ma, G. Ji, C. Xu, J. Xu, Y.S. Meng, T. Wang, J.Y. Lee, Adv. Mater. 26 (2014) 3854-3859. [22] S. Wang, S. Yuan, Y.B. Yin, Y.H. Zhu, X.B. Zhang, J.M. Yan, Particle Particle Sys. Char. 33 (2016) 493-499. [23] H. Hou, M. Jing, Z. Huang, Y. Yang, Y. Zhang, J. Chen, Z. Wu, X. Ji, ACS Applied Mater. Interface 7 (2015) 19362-19369. [24] J.-H. Choi, C.-W. Ha, H.-Y. Choi, H.-C. Shin, C.-M. Park, Y.-N. Jo, S.-M. Lee, Electrochimi. Acta 210 (2016) 588-595. [25] Y. Zhu, P. Nie, L. Shen, S. Dong, Q. Sheng, H. Li, H. Luo, X. Zhang, Nanoscale 7 (2015) 3309-3315. [26] Y. Denis, P.V. Prikhodchenko, C.W. Mason, S.K. Batabyal, J. Gun, S. Sladkevich, A.G. Medvedev, O. Lev, Nature Comm. 4 (2013) 2922. [27] F. Wu, X. Guo, M. Li, H. Xu, Ceramic International 43 (2017) 6019-6023. [28] S.K. Behera, Chem. Comm. 47 (2011) 10371-10373. [29] W.S. Hummers, R.E. Offeman, J. Amer. Chem. Soc. 80 (1958) 1339-1339. [30] P. Saha, L. Dashairya, J. Porous Mater. (2018) 1475-1488. [31] L. Dashairya, M. Sharma, S. Basu, P. Saha, J. Alloys Compounds 735 (2018) 234-245. [32] C. Pilapong, T. Thongtem, S. Thongtem, J. Alloys Compounds 507 (2010) L38-L42. [33] L. Dashairya, M. Rout, P. Saha, Advanced Composites Hybrid Mater. 1 (2018) 135-148. [34] S. Abdolhosseinzadeh, H. Asgharzadeh, H. Seop Kim, Scientific Rep. 5 (2015) 10160. [35] G. Murtaza, M. Akhtar, M. Azad Malik, P. O’Brien, N. Revaprasadu, Mater. Sci. Semi. Proc. 40 (2015) 643-649. [36] Y. Xu, Q. Liu, Y. Zhu, Y. Liu, A. Langrock, M.R. Zachariah, C. Wang, Nano Lett. 13 (2013) 470-474. [37] Y. Zhao, A. Manthiram, Chem. Comm. 51 (2015) 13205-13208.