Layered-Structure SbPO 4 /Reduced Graphene Oxide: An Advanced Anode Material for Sodium Ion Batteries Jun Pan, Shulin Chen, # Qiang Fu, Yuanwei Sun, # Yuchen Zhang, Na Lin, Peng Gao,* # Jian Yang,* and Yitai Qian Key Laboratory of Colloid and Interface Chemistry Ministry of Education School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P. R. China # International Center for Quantum Materials, and Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, P. R. China State Key Lab of Crystal Materials, Shandong University, Jinan 250100, P. R. China Hefei National Laboratory for Physical Science at Microscale Department of Chemistry University of Science and Technology of China, Hefei 230026, P. R. China 1
Movie S1. Sodium insertion in SbPO 4 nanostructures was recorded at low magnification. Movie S2. Sodium insertion in SbPO 4 nanostructures was recorded at selected area electron diffraction. Figure S1. Raman spectra of SbPO 4 /rgo. Figure S2. FTIR spectra of (a) SbPO 4 /rgo and SbPO 4, (b) GO and rgo. 2
Despite such a reduction of rgo is easy to occur at a high temperature, we still need a direct evidence to support this point. Therefore, FTIR spectrum of SbPO 4 /rgo is measured. However, SbPO 4 alone also exhibits strong absorption bands overlapped with those of oxygen-containing groups from GO and rgo (Figure S2a), which makes the judgement on the reduction of GO difficult. So, we remove SbPO 4 from the protocol and treat GO under the same conditions to clarify if oxygen-containing groups are reduced by the treatments in the paper. As illustrated in Figure S2b, the absorption bands attenuate at 1385 cm -1 and 1630 cm -1 and disappear at 1725 cm -1, suggesting the less oxygen-containing groups after this synthesis. This result well supports the reduction of GO and then the formation of rgo. Figure S3. TGA of SbPO 4 /rgo. 3
Figure S4. XRD pattern of SbPO 4 /rgo calcined at 650 o C in the air. Figure S5. XPS spectrum of SbPO 4 /rgo. Figure S6. Growth direction of SbPO 4. (a) TEM images of SbPO 4 /rgo, (b) FFT pattern of SbPO 4 /rgo. 4
Figure S7. EDX spectra of SbPO 4. Figure S8. N 2 sorption isotherms of SbPO 4 /rgo. Figure S9. Ex situ SAED pattern of SbPO 4 /rgo charged to 1.5 V. 5
Figure S10. Charge/discharge profiles of SbPO 4 /rgo at 0.1 A g -1 (a) over 0.01-1.5 V and (b) over 0.01-2.5 V. Figure S11. HRTEM image and SAED pattern of the electrode charged to 2.5 V. Figure S12. Cycling performance and rate performance of SbPO 4 /rgo charged to 2.5 V. 6
Figure S13. Cycling performance of rgo at current density of 0.5 A g -1. Figure S14. (a) The first discharge/charge curves of pre-sodiated composite and untreated composite. (b) The first discharge/charge curves of the composite at different discharge/charge windows. 7
Figure S15. TEM and SEM images of (a, c) SbPO 4 /rgo and (b, d) SbPO 4 after 100 cycles at 0.5 A g -1. Figure S16. Unit cells of the graphene (left) and the Sb (012) (right) surfaces. The graphene and the Sb (012) surfaces are not commensurate, which makes strain inevitable at the interface owing to the periodic boundary conditions that are exerted in the density functional theory calculations. Using a larger periodicity by including more atoms in the unit cell, on the one hand, can reduce the magnitude of the strain, while on the other hand, it also leads to a significant increase of the computational cost. Thus, a good balance between the magnitude of the strain and the size of the unit cell should be achieved when one searches for a 8
suitable interface model. In Supplementary Fig. 11, we present the unit cells of the two surfaces used in the simulations, which corresponds to 44 carbon and 48 antimony atoms (four Sb layers), respectively. In this model, the lattice parameter of Sb (012) is kept, whereas graphene is subjected to low tension, with a mean value of 0.85%. Figure S17. Configuration of the rgo model used in the simulations. The gray, red, and white spheres represent carbon, oxygen, and hydrogen atoms, respectively. The rgo model was constructed referring to the XPS results in the experiments. Here, C-O groups were mainly taken into account, since, among the various functional groups at rgo, the content of C-O was found to be the most. According to the XPS peak areas, the proportion of such type of carbon atoms in all is about one-seventh (on both sides of rgo). Thus, in our model, the ratio of oxygen (on one side) to carbon atoms is set to 3:41. The configuration of the rgo model is shown in Supplementary Fig. 12. To simulate a defective graphene substrate, we generated a single carbon vacancy near each C-O group, where one of the two dangling carbon atoms was saturated by a hydrogen atom. 9
Figure S18. XPS spectra of SbPO 4 /rgo and SbPO 4 discharged to 0.5 V after three cycles. Figure S19. Capacity retention of SbPO 4 /rgo and SbPO 4 at different current density. 10
Figure S20. Full cell demonstration. (a) XRD pattern of Na 3 V 2 (PO 4 ) 3 /C. (b) TEM image of Na 3 V 2 (PO 4 ) 3 /C. (c) Charge-discharge profiles at the current density of 0.5 A g -1. (d) Cycling performance of Na 3 V 2 (PO 4 ) 3 /C at current density of 0.5 A g -1. 11
Table S1. The sodium storage properties of reported Sb-related anodes Sb-related anode Capacity [ma h g -1 ] Cycle life Capacity retention Sb/Sb 2 O 3 550 at 0.66 A g -1 180 92.8 1 Sb/C 371 at 0.5 A g -1 100 94 2 Sb@C 230 at 1 A g -1 2000 56 3 Sb 521 at 0.2 A g -1 250 84 4 Sb@C 280 at 1 A g -1 200 84.8 5 ZnS-Sb 2 Se 3 @C 630 at 0.1A g -1 120 61 6 SnSb@Carbon 396 at 0.1 A g -1 100 77 7 Sb 2 MoO 6 372 at 0.2 A g -1 220 93.2 8 NP-Sb 574 at 0.1 A g -1 200 82.8 9 Sb-C 250 at 1 A g -1 200 90 10 [%] Ref. SbPO 4 /rgo 280 at 0.5 A g -1 146 at 1 A g -1 100 at 1 A g -1 100 200 1000 99 96.8 66 This work References (1) Pan, J.; Wang, N. N.; Zhou, Y. L.; Yang, X. F., Zhou, W. Y., Qian, Y. T.; Yang, J. Simple Synthesis of a Porous Sb/Sb 2 O 3 Nanocomposite for a High-Capacity Anode Material in Na- Ion Batteries. Nano Res. 2017, 10, 1794-1803. (2) Duan, J.; Zhang, W.; Wu, C.; Fan, Q. J.; Zhang, W. X.; Hu, X. L.; Huang, Y. H. Self- Wrapped Sb/C Nanocomposite as Anode Material for High-Performance Sodium-Ion Batteries. Nano Energy 2015, 16, 479-487. (3) Liu, Z. M.; Yu, X. Y.; Lou, X. W.; Paik, U. Sb@C Coaxial Nanotubes as a Superior Long- Life and High-Rate Anode for Sodium Ion Batteries. Energy Environ. Sci. 2016, 9, 2314-2318. 12
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