Supporting Information

Transcription

1 Supporting Information Iron Telluride Decorated Reduced Graphene Oxide Hybrid Microspheres as Anode Materials with Improved Na-Ion Storage Properties Jung Sang Cho 1, Seung Yeon Lee 1, Jung-Kul Lee 2, *, and Yun Chan Kang 1, * Address: 1 Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul , Republic of Korea. 2 Department of Chemical Engineering, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul , Republic of Korea. *Corresponding author. yckang@korea.ac.kr, jkrhee@konkuk.ac.kr. S-1

2 Characterization The crystal structures of the FeTe 2 -rgo hybrid and bare FeTe 2 powders were investigated using X-ray diffractometry (XRD, X pert PRO MPD) with Cu-K α radiation (λ = Å) at the Korea Basic Science Institute (Daegu). The morphologies of the two samples were investigated using scanning electron microscopy (SEM, TESCAN, VEGA3 SBH) and highresolution transmission electron microscopy (HR-TEM, JEOL, JEM-2100F) at a working voltage of 200 kv. The specific surface areas of the powders before and after post-treatment at various temperatures were calculated by a Brunauer-Emmett-Teller analysis of nitrogenadsorption (TriStar 3000). X-ray photoelectron spectroscopy (XPS, Thermo Scientific K- Alpha) of the powders was performed with Al Kα radiation ( ev). The structure of the carbon in the microspheres was characterized via Raman spectroscopy (Jobin Yvon LabRam HR800, excitation source: nm He-Ne laser) at room temperature. To determine the amount of rgo in the FeTe 2 -rgo hybrid powders, thermogravimetric analysis (TGA, TA Instruments, SDT Q600) and elemental analysis (EA, Eurovector, EA3000) was performed in air at a heating rate of 10 C min -1. Electrochemical measurements The electrochemical properties of the FeTe 2 -rgo hybrid and bare FeTe 2 powders were analyzed using a 2032-type coin cell. The anode was prepared by mixing the active material, carbon black, and sodium carboxymethyl cellulose at a weight ratio of 7:2:1. Na metal and microporous polypropylene film were used as the counter electrode and the separator, respectively. The electrolyte was 1 M NaClO 4 and 5% fluoroethylene carbonate dissolved in a mixture of ethylene carbonate/dimethyl carbonate (1:1 v/v). The discharge/charge characteristics of the samples were investigated by cycling over a potential range of V at various current densities. Cyclic voltammograms (CVs) were measured at a scan rate of 0.07 mv s -1. The size of the negative electrode containing the FeTe 2 powders was 1.0 cm 1.0 cm and the mass loading was approximately 2.0 mg cm -2. The electrode density of the FeTe 2 -decorated rgo hybrid powders was approximately 1.62 g cm -3. Electrochemical impedance spectra were obtained by AC electrochemical impedance spectroscopy (EIS, edaq SP1 ZIVE Potentiostat) over a frequency range of 0.01 Hz 1000 khz. S-2

3 Figure S1. Schematic diagram of the spray pyrolysis applied in the preparation of the Fe 3 O 4 - decorated rgo hybrid powders as a precursor powder. S-3

4 Figure S2. (a) Schematic diagram and (b) digital photo of the pilot-scale spray drying system applied in the preparation of the precursor powders for the bare Fe 2 O 3 powders. S-4

5 Figure S3. Morphologies and phase analysis of the Fe3O4-decorated rgo hybrid powders prepared at 600 oc in Ar atmosphere by spray pyrolysis: (a) SEM image, (b-d) TEM images, (e) HR-TEM image, and (f) XRD pattern. S-5

6 Figure S4. TG analysis of the FeTe 2 -decorated rgo hybrid powders. Table S1. Elemental analysis of the FeTe 2 -decorated rgo hybrid powders. S-6

7 Figure S5. SEM images and XRD patterns of the bare FeTe 2 powders prepared (a) after spray drying process, (b) subsequent combustion process for the sake of carbon decomposition in the structure, and (c) subsequent tellurization process. S-7

8 R e : the electrolyte resistance, corresponding to the intercept of high frequency semicircle at Z re axis R f : the SEI layer resistance corresponding to the high-frequency semicircle Q 1 : the dielectric relaxation capacitance corresponding to the high-frequency semicircle R ct : the denote the charger transfer resistance related to the middle-frequency semicircle Q 2 : the associated double-layer capacitance related to the middle-frequency semicircle Z w : the Na-ion diffusion resistance Figure S6. Randle-type equivalent circuit model used for AC impedance fitting. S-8

9 Figure S7. CV curves of the bare FeTe 2 powders. S-9

10 Table S2. Sodium-ion storage properties of various metal compounds materials. Materials FeTe 2 -rgo composite SnS 2 -rgo composite CuO nanorod arrays Voltage range (V) Current rate Initial Coulombic efficiency [%] A g % A g % 0.2 A g - 1 ~88 % TiO 2 nanotube A g % MoS 2 /graphene composite SnSe/carbon nanocomposite MoSe 2 yolk-shell A g % A g % A g % Initial discharge/charge Capacity Final discharge capacity Cycle number 493/373 mah g mah g Ref This work 839/630 mah g mah g S1 ~700/~620 mah g ma h g S2 110/75 mah g mah g S3 407/338 mah g S4 748/412 mah g mah g S5 527/448 mah g mah g S6 Sn 4 P A g mah g S7 FeSe 2 microspheres Flower-like Sb 2 S 3 MnS hollow microspheres VS 4 /rgo composite powder NiS 2 -graphene nanosheets A g A g A g -1 ~65 % A g % C 65 % Cu 3 P nanowire A g -1 - CoSe x -rgo composite NiSe 2 /C porous nanofiber A g % A g % 442/- mah g mah g S8 970/707 mah g mah g S9 ~750/~490 mah g mah g S10 450/338 mahg mah g S11 529/- mah g mah g S12 -/196 mah g mah g S13 656/460 mah g mah g S14 717/516 mah g mah g S15 SnSe alloy A g mah g S16 Reference (S1) Qu, B.; Ma, C.; Ji, G.; Xu, C., Xu, J.; Meng, Y. S.; Wang, T.; Lee, J. Y. Layered SnS 2 Reduced Graphene Oxide Composite A High Capacity, High Rate, and Long Cycle Life Sodium Ion Battery Anode Material. Adv. Mater. 2014, 26, (S2) Yuan, S.; Huang, X. L.; Ma, D. L.; Wang, H. G.; Meng, F. Z.; Zhang, X. B. Engraving Copper Foil to Give Large Scale Binder Free Porous CuO Arrays for a High Performance Sodium Ion Battery Anode. Adv. Mater. 2014, 26, S-10

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