Supporting Information

Transcription

1 Supporting Information Nanoconfined Iron Oxychloride Material as a High-Performance Cathode for Rechargeable Chloride Ion Batteries Tingting Yu, Qiang Li, Xiangyu Zhao,*,, Hui Xia, Liqun Ma, Jinlan Wang, Ying Shirley Meng*, and Xiaodong Shen, College of Materials Science and Engineering, Nanjing Tech University, 5 Xinmofan Road, Nanjing , China Jiangsu Collaborative Innovation Center for Advanced Inorganic Functional Composites, Nanjing Tech University, 5 Xinmofan Road, Nanjing , China School of Physics, Southeast University, Nanjing , China School of Materials Science and Engineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing , China Department of NanoEngineering, University of California San Diego, La Jolla, CA, USA State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, 5 Xinmofan Road, Nanjing , China S1

2 Experimental section The FeOCl/CMK-3 nanocomposite was prepared by impregnating FeCl 3 6H 2 O (Alfa Aesar) into the mesoporous carbon CMK-3 (XF Nano, China) with a pore size of nm under vacuum, followed by a thermal decomposition at 453 K for 10 h. First, the FeCl 3 6H 2 O and CMK-3 powders were mixed together in a mortar. The mixture was loaded into an evacuated and sealed quartz tube, and subsequently treated at 353 K for 24 h. The obtained FeCl 3 6H 2 O/CMK-3 powders were then heat treated at 453 K for 10 h in a flask under reduced pressure. The product was washed with acetone to remove the residue iron chloride species, followed by an overnight drying at 333 K under vacuum. The as-prepared powders are denoted as FeOCl/CMK-3 with a nominal composition of FeOCl-35 wt% CMK-3. The exact carbon content in the FeOCl/CMK-3 is confirmed as 37.2 wt% by the element analysis (Vario EL Ⅲ), indicating the high efficiency of the thermal decomposition. The pure FeOCl powders were prepared by directly decomposing FeCl 3 6H 2 O at 453 K for 10 h. Measurements of X-ray powder diffraction (XRD, Rigaku SmartLab, Cu-Kα radiation), field-emission scanning electron microscopy (FE-SEM, Ultra55) and transition electron microscopy (TEM, Tecnai G2 F30 U-TWIN and JEM-2100 UHR) were performed to characterize the structure, composition, and morphology of the samples. Fourier transform infrared spectroscopy (FTIR) spectra were obtained using a Thermo Nicolet Nexus 670 Spectrometer in the wave number range from 400 to 4000 cm -1. For the sample preparation, anhydrous acetonitrile (ACN) was used to wash the samples for removing the residue electrolyte in the glove box. Electrochemical measurements were conducted using coin cells (CR2032) with lithium metal (Alfa Aesar) as anode. The cathode electrodes were fabricated by the slurry coating of the as-prepared FeOCl/CMK-3 powders, PVDF and carbon black in the mass ratio of 80:10:10. For the pure FeOCl electrode, the mass ratio is 60:10:30. N-methyl-2-pyrrolidinone S2

3 (NMP) was used as the solvent for PVDF to get homogeneous slurry, which was spread on a graphite foil (17μm, Suzhou Dasen Electronics Material Co. Ltd) and dried in a vacuum at 373 K for 20 h. A mixture of 0.5 M PP 14 Cl in PP 14 TFSI was used as electrolyte. 13,16,17 Celgard 2400 film was used as separator. Discharge and charge tests were carried out galvanostatically at 10 ma g -1 over a voltage range between 1.6 and 3.5 V by using Arbin BT2000 multichannel battery testing system at 298 K. The specific capacities were calculated according to the corresponding active material of the cathode. Electrochemical impedance spectroscopy (EIS, 100 khz to 10 mhz, 10mV) and Cyclic voltammetry (CV, 1.6 to 3.5 V, 60 μv s -1 ) data were all collected by a BioLogic (VMP3) electrochemical workstation. S3

4 Figure S1. Photos of the acetone solutions with immersion of the FeOCl materials after 48 h. FeOCl is the sample prepared by the chemical vapor transport method. FeOCl/CN-250 and FeOCl/CN-450 are prepared by the chemical vapor transport method and subsequent mechanical milling of FeOCl with carbon nanotube at the milling speeds of 250 and 450 rpm, respectively. FeOCl/GN-450 and FeOCl/CB-450 are prepared by the chemical vapor transport method and subsequent mechanical milling of FeOCl with graphene and carbon black at the milling speed of 450 rpm, respectively. It is clear that the carbon incorporation by mechanical milling leads to the decomposition of FeOCl materials and the formation of FeCl 3, which can be dissolved in the acetone. FeOCl/CMK-3 is the sample in this work and is stable in the acetone. S4

5 Figure S2. EDS pattern of the powder in Figure 1h. The Cu element is from the TEM copper grid sample holder. S5

6 Figure S3. a) XRD patterns of the FeOCl/CMK-3 with different CMK-3 contents. SEM images and the corresponding EDS patterns of the b, c) FeOCl-40CMK h and d, e) FeOCl-45CMK h samples. S6

7 Figure S4. Cycling performance of the FeOCl/CMK-3 with different CMK-3 contents. S7

8 Figure S5. XRD patterns of the as-prepared FeOCl electrodes before and after cycling in the first cycle. S8

9 DFT calculations All first principles calculations were performed with the Vienna ab initio Simulation Package (VASP). 1-3 The generalized gradient approximation (GGA) with the functional described by Perdew-Burke-Ernzerhof (PBE) functional 4, the projector-augmented wave (PAW) method 5-6 was applied to describe the wavefunctions in the core regions, while the valence wavefunctions were expanded as linear combination of plane-waves with a cutoff energy of 400 ev. In the geometry optimizations, the total energy was converged to 10-5 ev and the Hellmann-Feynman force on each relaxed atom was less than 1 mev/å. The equilibrium lattice constants (a = 3.70 Å, b = 7.81 Å and c=3.27 Å) are close to experimental result and other theoretical results. 7 The vacuum space between two adjacent sheets was set at least 15 Å to eliminate the interactive effect on each other. The weak Van der Waals interaction between BP layers is described by dispersion correction PBE+D2. 8 The DFT+U method was applied as follows, 5.0 ev for the d states of Fe, 4.8 ev for the p states of O, and 7.0 ev for the p states of Cl. 7 The Cleave energy is calculated by the energy difference between two FeOCl layers and two times of single FeOCl layer, 2*2 and 3*3 super cells are applied. The adsorption energy is calculated by, E ad = E(MO@FeOCl) E(MO) E(FeOCl) Where E(MO) indicates the energy of adsorbed molecules, E(FeOCl) stands for the energy of FeOCl bare surface, and E(MO@FeOCl) represents the energy of the molecules adsorbed on FeOCl surface. S9

10 Figure S6. Adsorption structures and adsorption energies of three molecules on FeOCl (001) surface, and the energies are calculated based on single layer of FeOCl. References (1) Kresse, G.; Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comp. Mater. Sci. 1996, 6, (2) Kresse, G.; Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 1996, 54, (3) Kresse, G.; Hafner, J. Ab initio molecular dynamics for open-shell transition metals. Phys. Rev. B 1993, 48, (4) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, (5) Kresse, G.; Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 1999, 59, (6) Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 1994, 50, (7) Zhang J., Jiao X., Xia Y., Liu F., Pang Y., Zhao X., Chen D. Enhanced Catalytic Activity in Liquid-Exfoliated FeOCl Nanosheets as a Fenton-Like Catalyst. Chem. Eur. J. 2016, 22, (8) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 2010, 132, S10

11 Figure S7. XRD patterns of the as-prepared FeOCl/CMK-3 nanocomposite treated by a 10 h immersion in NMP or ACN at 298 K. S11

12 Figure S8. EDS patterns of the FeOCl/CMK-3 electrodes before and after cycling at the first cycle. (a) as-prepared, (b) fully discharged and (c) fully charged. The Cu element is from the TEM copper grid sample holder. S12

13 Figure S9. FTIR spectra of the electrolyte, the as-prepared FeOCl powders treated by the same process of a 10 h immersion in the electrolyte as that of the FeOCl electrode, the asprepared FeOCl powders treated by a 10 h immersion in NMP, the as-prepared FeOCl powders and NMP. S13