1 Supporting Information N-doped Amorphous Carbon Coated Fe3O4 ...
Supporting Information N-doped Amorphous Carbon Coated Fe3O4/SnO2 Co-axial Nanofibers as a Binder-free Self-supported Electrode for Lithium Ion Batteries Wenhe Xie, Suyuan Li, Suiyan Wang, Song Xue, Zhengjiao Liu, Xinyu Jiang and Deyan He* School of Physical Science and Technology, and Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China *E-mail: [email protected] Experimental details Fabrication of the Fe3O4/SnO2 composite nanofibers: 0.265 g FeCl2·4H2O, 0.15 g SnCl2·2H2O (with a Fe : Sn molar ratio of 2 : 1) and 0.3 g polyvinylpyrrolidone (PVP) were dissolved in 2.4 g N,N-dimethylformamide (DMF) under vigorous magnetic stirring for several hours. Then the mixture was electrospun using a 25-gauge injection needle with a flow rate of 0.15 mL/h under an applied voltage of 15 kV. The distance between the needlepoint and the grounded collector of aluminium foil was 17 cm. The as-spun nanofibers were in turn calcined at 500 °C for 4 h in air and pure argon atmosphere. Fabrication of the pure SnO2 nanofibers: 2 mM SnCl2·2H2O and 0.3 g PVP were first dissolved in 2.4 g DMF under vigorous magnetic stirring for several hours. The obtained mixture was then electrospun with the same experimental conditions as mentioned above. Finally, the asspun nanofibers were calcined at 500°C for 4 h in air.
1
Fabrication of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers (with a Fe : Sn molar ratio of 1 : 1): 1 mM FeCl2·4H2O, 1mM SnCl2·2H2O and 0.3 g PVP were dissolved in 2.4 g DMF under vigorous magnetic stirring for several hours. The obtained mixture was electrospun and the as-spun nanofibers were calcined with the same experimental conditions as mentioned above. The coating and the carbonization of polydopamine followed the same procedure described in the main text.
Figure S1. SEM images of (a) the Fe3O4/SnO2 nanofibers and (b) the pure SnO2 nanofibers
2
Figure S2. N2 adsorption/desorption isotherms and the corresponding BJH distributions (insets) of (a) the Fe2O3/SnO2 composite nanofibers and (b) the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers. The estimated surface areas are 107.47 and 54.96 m2/g, and the average pore diameters are about 5.44 and 4.55 nm for the Fe2O3/SnO2 composite nanofibers and the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers, respectively.
Figure S3. TEM elemental maps of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers.
3
Figure S4. XRD patterns of the Fe2O3/SnO2 composite nanofibers, the Fe3O4/SnO2 composite nanofibers and the pure SnO2 nanofibers. The molar ratio of Fe to Sn is 2 : 1.
Figure S5. Cycling performances of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers (with a Fe : Sn molar ratio of 1 : 1), the Fe3O4/SnO2 composite nanofiber and the pure SnO2 nanofiber electrodes at a current density of 100 mA/g.
4
Figure S6. TEM and HRTEM images of a single nanofiber after the rate performance test. The thickness of the carbon shell increased to 22 nm. No lattice fringes are found in the HRTEM image, indicating that the metal oxides are amorphous after cycling.
Figure S7. SEM image of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers after cycling.
5
Figure S8. Nyquist plots of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofiber， the Fe2O3/SnO2 composite nanofiber and the Fe3O4/SnO2 nanofiber electrodes after the first cycle.
6
1
Fabrication of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers (with a Fe : Sn molar ratio of 1 : 1): 1 mM FeCl2·4H2O, 1mM SnCl2·2H2O and 0.3 g PVP were dissolved in 2.4 g DMF under vigorous magnetic stirring for several hours. The obtained mixture was electrospun and the as-spun nanofibers were calcined with the same experimental conditions as mentioned above. The coating and the carbonization of polydopamine followed the same procedure described in the main text.
Figure S1. SEM images of (a) the Fe3O4/SnO2 nanofibers and (b) the pure SnO2 nanofibers
2
Figure S2. N2 adsorption/desorption isotherms and the corresponding BJH distributions (insets) of (a) the Fe2O3/SnO2 composite nanofibers and (b) the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers. The estimated surface areas are 107.47 and 54.96 m2/g, and the average pore diameters are about 5.44 and 4.55 nm for the Fe2O3/SnO2 composite nanofibers and the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers, respectively.
Figure S3. TEM elemental maps of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers.
3
Figure S4. XRD patterns of the Fe2O3/SnO2 composite nanofibers, the Fe3O4/SnO2 composite nanofibers and the pure SnO2 nanofibers. The molar ratio of Fe to Sn is 2 : 1.
Figure S5. Cycling performances of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers (with a Fe : Sn molar ratio of 1 : 1), the Fe3O4/SnO2 composite nanofiber and the pure SnO2 nanofiber electrodes at a current density of 100 mA/g.
4
Figure S6. TEM and HRTEM images of a single nanofiber after the rate performance test. The thickness of the carbon shell increased to 22 nm. No lattice fringes are found in the HRTEM image, indicating that the metal oxides are amorphous after cycling.
Figure S7. SEM image of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofibers after cycling.
5
Figure S8. Nyquist plots of the carbonized polydopamine coated Fe3O4/SnO2 co-axial nanofiber， the Fe2O3/SnO2 composite nanofiber and the Fe3O4/SnO2 nanofiber electrodes after the first cycle.
6
