Effective Interlayer Engineering of Two-Dimensional. for Improving Alkali Ion Storage

Transcription

1 Supporting Information for Effective Interlayer Engineering of Two-Dimensional VOPO 4 Nanosheets via Controlled Organic Intercalation for Improving Alkali Ion Storage Lele Peng,, Yue Zhu,, Xu Peng, Zhiwei Fang, Wangsheng Chu, Yu Wang, Yujun Xie, Yafei Li, Judy J. Cha, and Guihua Yu,* Materials Science and Engineering Program and Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States. National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui , China. College of Chemistry and Materials Science, Nanjing Normal University, Nanjing, Jiangsu , China. Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, United States. *Correspondence should be addressed: ghyu@austin.utexas.edu These authors contributed equally.

2 Experimental Details Synthesis of VOPO 4 2H 2 O bulk chunks. VOPO 4 2H 2 O bulk chunks were synthesized according to a simple reflux method reported in the previous literature g of V 2 O 5 powders (Aldrich) and 26.6 ml concentrated H 3 PO 4 (85%, Aldrich) were dispersed in ml of DI H 2 O. The mixed dispersion was then refluxed at 110 C for 16 h. Thereafter, the dispersion was permitted cool down to room temperature. The yellow-greenish precipitate was finally collected by centrifugation and washed several times with water and acetone. The resulting sample was dried in vacuum at 60 C for 3 h. Intercalation of TEG and THF molecules into VOPO 4 nanosheets. The intercalation compounds were obtained by a displacement reaction. In a typical intercalation process, 100 mg VOPO 4 2H 2 O bulk chunks were dispersed in 7 ml isopropanol (IPA) solvent, and then 8 ml organic intercalants, like TEG and THF, were added into the VOPO 4 IPA dispersion. After magnetic stirring under 110 C for 2 days, the blue-greenish TEG-VOPO 4 sample and the darkgreen THF-VOPO 4 samples were obtained. The as-obtained powders were further washed with IPA for three times, and dried in vacuum at 80 C for overnight. Characterizations. The structure of the as-synthesized samples was characterized by powder X- ray diffraction (XRD) patterns performed on a Philips Miniflex diffractometer. The morphology of the samples was investigated using scanning electron microscope (SEM), scanning transmission electron microscope (STEM) (Hitachi S5500), and transmission electron microscope (TEM) (JEOL 2010F). The TG analysis was tested by a TGA/SDTA851e thermogravimetric analyzer under an air atmosphere from 25 to 850 C at a heating rate of 10 C min 1.

3 Electrochemical Measurements. The working electrodes were prepared by mixing active materials (TEG and THF intercalated VOPO 4 nanosheets and the pure VOPO 4 nanosheet control sample), sodium carboxymethyl cellulose (CMC) and superp carbon at a weight ratio of 85:10:5. Then the slurries were drop-casted onto the aluminum foil. The as-prepared electrodes were dried under vacuum at 110 C for 10 h. The loading of active materials was ~1.0 mg cm -2. After being sealed, the electrodes were assembled into coin cells (CR2032) in an argon-filled glovebox using Celgard 2320 as separator, 1 mol L 1 NaClO 4 in propylene carbonate (PC) with 2% fluoroethylene carbonate (FEC) added as the electrolyte and Na metal as the counter electrode. The assembled coin cells were tested on the LAND and Biologic VMP3 battery test systems with a voltage range of 2.5~4.3 V. Energy barrier calculation details. DFT calculations were performed using Vienna ab Initio Simulation package (VASP) package, 2 with ion electron interaction treated by the projectoraugmented plane wave (PAW) pseudopotentials. 3,4 The Perdew Burke Ernzerhof (PBE) generalized gradient approximation (GGA) functional 5 and a plane-wave cutoff energy of 400 ev were used in all computations. The convergence of energy and forces were set to ev and 0.04 ev/å, respectively. The Brillouin zone was sampled with k-points. The climbing-image nudged elastic band (CI-NEB) method was adopted to determine the minimum diffusion path of Na on the surface of VOPO 4. 6,7 Specially, the CI-NEB simulations were calculated based on a 2 2 supercell (56 atoms) and 11 images (including initial and final states). For the Brillouin zone, a k-points grid was adopted for the supercell. The ordinary and enlarged interlayer spacing were realized by fixed the atoms of VOPO 4 bilayer with specific distances. Specially, two possible diffusion pathways, namely P1 and P2, were identified for the controlled pure and TEG intercalated VOPO 4 nanosheets.

4 Figure S1. STEM image of the THF intercalated VOPO 4 nanosheets (THF-VOPO 4 ), showing the flat surface and ultrathin thickness. Scale bar is 500 nm.

5 Figure S2. (a) Schematic illustration of the organic molecules intercalated VOPO 4 nanosheets. (b) Raman spectra of the pure VOPO 4 2H 2 O bulk chunks, THF and TEF intercalated VOPO 4 nanosheets.

6 Figure S3. Thermogravimetric analysis (TGA) of the pure VOPO 4 2H 2 O bulk chunks, THF and TEF intercalated VOPO 4 nanosheets.

7 Figure S4. XPS curves of the VOPO 4 2H 2 O bulk chunks, THF and TEF intercalated VOPO 4 nanosheets.

8 Figure S5. Charge-discharge curves of the TEG (a), THF (b) intercalated VOPO 4 nanosheets at various C rates.

9 Figure S6. XRD patterns and the TEM image of the TEG-intercalated VOPO 4 nanosheets after cycling tests.

10 Figure S7. Kinetics analysis of the 2D THF intercalated VOPO 4 nanosheets for sodium ion storage. (a) CV curves at various scan rates from 0.02 to 0.2 mv s 1 for THF intercalated VOPO 4 nanosheets. (b) Determination of the b-value using the relationship between peak current and scan rate. (c) Separation of the capacitive and diffusion currents at a scan rate of 0.5 mv/s. (d) Contribution ratio of the capacitive and diffusion-controlled charge at various scan rates.

11 Table S1. Summary of the kinetics parameters of the 2D TEG, THF intercalated VOPO 4 nanosheets and the pure VOPO 4 nanosheets for sodium ion storage. CV scan range (mv/s) b-value cathodic/anodic Capacitive contribution at 0.1 mv/s Capacitive contribution at 5 mv/s Polarization at 0.02 mv/s (mv) TEG 0.02 ~ / % 96.2% 244 THF 0.02 ~ / % 93.3% 270 Pure 0.02~ / % 91.5% 340

12 Table S2. Comparison of the electrochemical performance, including capacity, capacity retention and rate capability, between the reported cathodes and our work. Materials Na 5/6 [Li 1/4 Mn 3/4 ]O 2 particles Na x [Fe 1/2 Mn 1/2 ]O 2 particles Na 0.66 Li 0.18 Mn 0.71 Ni 0.21 Co 0.08O 2+d composites Types P2-type P2-type P2+O3 type Capacity (mah g -1 ) 187 (1/24 C) 190 (1/20 C) 195 (0.1 C) Na 0.8 Ni 0.4 Ti 0.6 O 2 particles O3 type 84 (0.2 C) NaCrO 2 /C composites # Na[Ni 0.75 Co 0.02 Mn 0.23 ]O 2 - Na[Ni 0.58 Co 0.06 Mn 0.36 ]O 2 spherical particle. O3 type O3 type 122 (0.1 C) 157 (0.1 C) Capacity retention Rate capability (mah g -1 ) Ref N.A. 140 (2 C) 8 87% (30 cycles, 1/20 C) 73% (150 cycles, 0.5 C) 74% (150 cycles, 1 C) 90% (300 cycles, 1 C) 80% (100 cycles, 0.5 C) 63 (4 C) 9 70 (5 C) (1 C) (20 C) (0.5 C) 13 V 2 O 5 nh 2 O aerogel Other type 300 (0.1 58% (30 cycles, C) 0.5 C) 90 (~4.4 C) 14 Na 3 V 2 (PO 4 ) 3 /C NASICON 115 (0.2 62% (20000 composite * type C) cycles, 30 C) 100 (30 C) 15 Na 2 MnPO 4 F/C Fluorophos 140 ( % (50 cycles, nanocomposite phates C) 0.05 C) 62 (1C) 16 Na 3.12 M 2.44 (P 2 O 7 ) 2 Pyrophosp (M=Fe, Fe 0.5 Mn 0.5, Mn) hates 68 (0.5 C) N.A. 42 (10 C) 17 Na 2 FeP 2 O 7 particle Pyrophosp 90 (1/20 hates C) N.A. 34 (4 C) 18 NaFe(SO 4 ) 2 particle Sulfates 85 ( % (80 cycles, C) 0.05 C) 41 (2 C) 19 Layered VOPO 4 Layered 152 (0.05 structures C) N.A. 70 (0.5 C) 20 Ultrathin VOPO 4 Layered 140 (0.1 73% (500 nanosheets structures C) cycles, 5 C) 48 (10 C) 21 TEG intercalated Layered 151 (0.1 88% (500 This 74 (20 C) VOPO 4 nanosheets structures C) cycles, 5 C) work THF intercalated Layered 149 (0.1 76% ( (20 C) This

13 VOPO 4 nanosheets structures C) cycles, 5 C) work Note: # A thin layer of carbon was coated on the surface of the NaCrO 2 cathode, which will improve the rate capability. * Na 3 V 2 (PO 4 ) 3 particles were embedded in highly conductive and interconnected carbon frameworks. The carbon matrix forms an electronic wiring pathway among the Na 3 V 2 (PO 4 ) 3 particles increasing their capacity utilization and rate capability.

14 References 1. Yamamoto, N.; Hiyoshi, N.; Okuhara, T. Chem. Mater. 2002, 14, Kresse, G.; Hafner, J. Phys. Rev. B 1993, 47, Blöchl, P. E. Phys. Rev. B 1994, 50, Kresse, G.; Joubert, D. Phys. Rev. B 1999, 59, Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, Henkelman, G.; Jónsson, H. J. Chem. Phys. 2000, 113, Henkelman, G.; Uberuaga, B. P.; Jónsson, H. J. Chem. Phys. 2000, 113, Yabuuchi, N.; Hara, R.; Kajiyama, M.; Kubota, K.; Ishigaki, T.; Hoshikawa, A.; Komaba, S. Adv. Energy Mater. 2014, 4, Yabuuchi, N.; Kajiyama, M.; Iwatate, J.; Nishikawa, H.; Hitomi, S.; Okuyama, R.; Usui, R.; Yamada, Y.; Komaba, S. Nat. Mater. 2012, 11, Guo, S.; Liu, P.; Yu, H.; Zhu, Y.; Chen, M.; Ishida, M.; Zhou, H. Angew. Chem. Int. Ed. 2015, 54, Guo, S.; Yu, H.; Liu, P.; Ren, Y.; Zhang, T.; Chen, M.; Ishida M.; Zhou, H. Energy Environ. Sci. 2015, 8, Yu, C.-Y.; Park, J.-S.; Jung, H.-G.; Chung, K.-Y.; Aurbach, D.; Sun, Y.-K.; Myung, S.-T.; Energy Environ. Sci. 2015, 8, Hwang, J.-Y.; Oh, S.-M.; Myung, S.-T.; Chung, K.-Y.; Belharouak, I.; Sun, Y.-K. Nat. Commun. 2015, 6, Wei, Q.; Liu, J.; Feng, W.; Sheng, J.; Tian, X.; He, L.; An, Q.; Mai, L. J. Mater. Chem. A 2015, 3, Fang, Y.; Xiao, L.; Ai, X.; Cao, Y.; Yang, H. Adv. Mater. 2015, 27,

15 16. Lin, X.; Hou, X.; Wu, X.; Wang, S.; Gao, M.; Yang, Y. RSC Adv. 2014, 4, Ha, K.-H.; Woo, S. H.; Mok, D.; Choi, N.-S.; Park, Y.; Oh, S. M.; Kim, Y.; Kim, J.; Lee, J.; Nazar, L. F.; Lee, K. T. Adv. Energy Mater. 2013, 3, Kim, H.; Shakoor, R. A.; Park, C.; Lim, S. Y.; Kim, J. S.; Jo, Y. M.; Cho, W.; Miyasaka, K.; Kahraman, R.; Jung, Y.; Choi, J. W. Adv. Funct. Mater. 2013, 23, Singh, P.; Shiva, K.; Celio, H.; Goodenough, J. B. Energy Environ. Sci. 2015, 8, He, G.; Kan, W. H.; Manthiram, A. Chem. Mater. 2016, 28, Zhu, Y.; Peng, L.; Chen, D.; Yu, G. Nano Lett. 2016, 16,