Supporting Information. Construction of Multishelled Binary Metal Oxides via Coabsorption of Positive

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1 Supporting Information Construction of Multishelled Binary Metal Oxides via Coabsorption of Positive and Negative Ions as a Superior Cathode for Sodium-Ion Batteries Xiaoxian Zhao,,,, Jiangyan Wang,, Ranbo Yu,*, Dan Wang*,. StateKey Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, No. 1, Beierjie, Zhongguancun, Beijing, , P. R. China. Department of Physical Chemistry, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, No. 30, Xueyuan Road, Haidian District, Beijing , P. R. China. Fax: ; Tel: These authors contributed equally to this work. *Correspondence to: ranboyu@ustb.edu.cn; danwang@ipe.ac.cn. This file includes: Part 1: Tables S1-S7; Part 2: Figures S1-S22; Part 3: Supporting references S1

2 Table S1. The Mo/Fe molar ratios in products obtained under different adding molar ratios of (NH4)2MoO4 to FeCl3 precursors. molar ratios of (NH4)2MoO4 to FeCl3 precursors Mo/Fe molar ratios in products S2

3 Table S2. The preparation condition of multi-shelled Fe2(MoO4)3 hollow sphere Temperature/ o C Time/h Molar ratio of Mo/Fe precursor Mass of citric acid/g Volume ratio of ethanol Single Double Triple Quadruple % Quintuple % NS No add 0 S3

4 Table S3. The relative molecular mass before and after adding (NH4)2MoO4 to citric acid solution Citric acid Citric acid+(nh4)2moo4 m/z Formula Score m/z Formula Score C 5 H 3 O C 6 H 3 Mo 2 O C 6 H 7 O C 6 H 5 Mo 2 O C 12 H 15 O C 2 H 5 Mo 2 O S4

5 Table S4. The atomic fractional coordinates and refinement error of multi-shelled Fe2(MoO4)3 hollow sphere refined from PDF# Name Type Fractional coordinates Mult X Y Z Mo5 Mo O2 O O15 O Mo1 Mo O18 O O14 O O5 O O24 O O4 O Mo4 Mo O8 O O7 O O19 O O23 O O1 O O17 O O11 O S5

6 O10 O O9 O O6 O Mo6 Mo O21 O Fe2 FE O16 O O20 O Mo3 Mo O22 O O13 O Fe4 FE Mo2 Mo O3 O Fe3 FE Fe1 FE O12 O Error wrp Rp wrp Rp DWd S6

7 Table S5. The cell parameters of Fe2(MoO4)3 hollow sphere parameters a b c α β γ Fe2(MoO4) S7

8 Table S6. The Inductively coupled plasma mass spectrometry (ICP-MS) of multishelled Fe2(MoO4)3 hollow sphere NS Sin Dou Tri Qua Qin Molar Ratio of Mo/Fe S8

9 Table S7. The specific surface area and pore volume of all multi-shelled structure materials are and NS material NS Sin Dou Tri Qua Qin Pore volume BET Note: nanosheet (NS), Single-shelled hollow sphere (Sin), Double shelled hollow sphere (Dou), Triple-shelled hollow sphere (Tri), Quadruple-shelled hollow sphere (Qua), Quintuple-shelled (Qin) hollow sphere. S9

10 Figure S1. (a) Optical image of mixture solution of FeCl3 and (NH4)2MoO4 when the ph is decreased to be 0.23 by adding HCl solution, without citric acid adding; (b) TEM image of obtained products at a ph of 0.23 without citric acid adding; (c) Optical image of mixture solution of FeCl3, (NH4)2MoO4 and citric acid when the ph is increased to be 1.0 by adding NH3 H2O solution; (d) TEM image of obtained products at a ph of 1.0 with citric acid adding. Without citric acid adding, the precipitation reaction happens even when the ph of solution was decreased to be about 0.23 by adding HCl solution. As a result, the binary metal oxide (Fe2(MoO4)3) precursor nucleates and precipitates on the surface of carbonaceous microsphere (CMS) template, instead of penetrating into the inside of CMS templates. As a result, only random solid micro-/nano-particles can be obtained after calcination. S10

11 With citric acid adding, the hydrolysis of Fe 3+ happens as the ph is increased a little to be 1.0 by adding NH3 H2O solution. As a result, many nanoparticles can be observed besides hollow spheres from the TEM image, indicating the nonuniformity of the products. S11

12 Figure S2. The characterizations of CMS adsorbed in aqueous without citric acid (a: TEM before calcination; b: SEM before calcination; c to f: EDS before calcination; g: TEM after calcination; h: SEM after calcination). When CMS is put into the slurry without citric acid, the precursor only can be precipitated on the surface of CMS, which is proved by the EDS analysis (as shown in Fig. S1c to S1f, the element Fe, Mo, O can be observed on the surface of CMS). Meanwhile, only the uniform single-shelled and particle structure materials will be obtained shown in Fig. S1g and S1h, which confirm above deduction. S12

13 Figure S3. The enlarged part from m/z 450 to of mass spectrum (MS) after adding (NH4)2MoO4 In the figure, the part a is experiment result, the part b is the simulated result. According to above figure, the experiment result is almost same to the simulated result of C6H5Mo2O12, which mean after chelation between citric acid and MoO4 2-, the C6H5Mo2O12 can be obtained. S13

14 Figure S4. The line element mapping by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) of CMS absorbed metal ion under different time (a,b: after sonication; c, d: 1h; e, f: 24h). As shown in above figure, with the increase of absorption time, the depth of metal ion into CMS is increased, meanwhile, the outside concentration is thicker than inner leading the formation of closed Quintuple-shelled Fe2(MoO4)3. S14

15 Figure S5. The morphology of Fe2(MoO4)3 synthesized by sequential templating method at different (a: 0.6g; b: 0.8g; c: 1.0g; d: 1.3g; e: 1.56g; f: 1.8g) adding amount of citric acid. S15

16 Intensity (a.u.) MoO 3 Fe 2 (MoO 4 ) 3 Mo/Fe=2.21 Mo/Fe=1.78 Mo/Fe=1.73 Mo/Fe=1.63 Mo/Fe=1.60 Mo/Fe=1.58 Mo/Fe=1.54 Mo/Fe= Theta ( o ) Figure S6. The crystal structure of hollow sphere products with different molar ratio of Mo/Fe by controlling the adding ratio of (NH4)2MoO4 to FeCl3 precursors. S16

17 Figure S7. The morphology of products prepared by sequential templating method with different molar ratio of Mo/Fe (a: 2.21; b: 1.78; c: 1.73; d: 1.63; e: 1.60; f: 1.58; g: 1.54; h: 1.504). S17

18 Figure S8. The CV curves (a) and cycling life (b) of multi-shelled Fe2(MoO4)3 hollow sphere at different Mo/Fe ratio as electrode material for sodium battery. S18

19 Figure S9. The SEM (a: double-shell; b: triple-shell; c: quadruple-shell; d: quintupleshell) and TEM (e: single-shell; f: double-shell; g: triple-shell; h: quadruple-shell; i: quintuple-shell) image of multi-shelled Fe2(MoO4)3 hollow sphere. S19

20 Intensity (a.u.) Obs Calc Bckgr Diff Theta ( o ) Figure S10. The refinement result of multi-shelled Fe2(MoO4)3 hollow sphere refined from PDF# S20

21 Intensity (a.u.) MoO 3 Mo/Fe = Mo/Fe = 1.78 Mo/Fe = Raman shift (cm -1 ) Figure S11. The Raman curves of multi-shelled hollow sphere products with different molar ratios of Mo to Fe. The peaks at 995 cm -1 is assigned to the asymmetric stretch of the terminal oxygen atoms (Mo 6+ = O), which is resulted from an unshared oxygen atom of hydrated MoO3. The 667 and 820 cm -1 peaks represent the doubly coordinated oxygen (Mo2-O) stretching mode along the c axis, which is resulted from corner-sharing oxygen atoms common to two octahedral in hydrated MoO3 1.The peak at 776 cm -1 and a shoulder at 820 cm -1 appear due to asymmetric stretching of the three MoO4 units. A relatively weaker peak at 966 cm -1 and a shoulder at 933 cm -1 appear due to the symmetric stretching of distorted Mo=O bonds in the MoO4 units in Fe2(MoO4)3 lattice 2. When the molar ratio of Mo/Fe in the products was decreased, the 995, 820 and 667 cm -1 peaks belonging to MoO3 were decreased. Besides, those peaks totally disappear when the molar ratio decreases to 1.5, indicating the product is pure Fe2(MoO4)3 with no MoO3 impurity existing. S21

22 Figure S12. The XRD curves of NiMoO4 (a), MnMoO4 (b), CoWO4 (c) and MnWO4 (d) hollow spheres prepared by coadsorption of negative and positive ion. The XRD curves are coincidence to NiMoO4, MnMoO4, CoWO4 and MnWO4 respectively. S22

23 Figure S13. The XPS curves of NiMoO4 (a), MnMoO4 (b), CoWO4 (c) and MnWO4 (d) hollow spheres prepared by coadsorption of negative and positive ion. The XRD curves are coincidence to NiMoO4, MnMoO4, CoWO4 and MnWO4 respectively. The XPS results of NiMoO4, MnMoO4, CoWO4 and MnWO4 hollow sphere figured out the binary metal oxide hollow sphere is composed of Ni 2+ and Mo 6+, Mn 2+ and Mo 6+, Co 2+ and W 6+, Mn 2+ and W 6+ respectively. S23

24 Figure S14. The other kinds of binary metal oxide hollow sphere prepared by chelation of citric acid with metal ion (a: NiMoO4; b: MnMoO4; c: CoWO4; d: MnWO4). S24

25 Figure S15. The TEM images of NiMoO4 (a), MnMoO4 (b), CoWO4 (c) and MnWO4 (d) hollow spheres prepared by coadsorption of negative and positive ion. As shown in above figure, the multi-shelled structure can be clarified clearly. S25

26 Weight loss (%) Fe+Mo Ni+Mo Mn+Mo Co+W Mn+W Temperature ( o C) Figure S16. The thermogravimetric Analysis (TGA) curves of CMS absorbed different kinds of binary precursors. The catalytic combustion of different metal ion to CMS, therefore, the weight loss of CMS is different. Meanwhile, the stronger catalytic ability is, the faster weight loss is. So the catalytic combustion of Fe and Mo precursor is strongest which lead to more-shelled Fe2(MoO4)3 hollow sphere under same preparation condition. S26

27 Figure S17. The element mapping images of NiMoO4 (a), MnMoO4 (b), CoWO4 (c) and MnWO4 (d) hollow spheres prepared by coadsorption of negative and positive ion. The elements of Ni and Mo, Mn and Mo, Co and W, Mn and W are dispersed in multishelled structure uniformly. S27

28 Figure S18. SEM (a) and TEM (b) images of Fe2(MoO4)3 nanosheet (NS). The nanosheet (NS) was synthesized as follow: firstly, the FeCl3 6H2O and (NH4)2MoO4 were dissolved into deionized water respectively, and then stoichiometric FeCl3 6H2O solution was added into aqueous (NH4)2MoO4 solution during agitation, until the solution becomes gel. Then, the gel was dried in oven at the temperature of 70 ºC for 10h. Finally, the powder was calcined at a temperature of 500 ºC for 2h. After cooling down, Fe2(MoO4)3 nanosheet was collected. S28

29 Figure S19. Brunauer-Emmett-Teller (BET) analysis curves (a) and Barrett Joyner Halenda (BJH) pore-size distribution (b) of multi-shelled Fe2(MoO4)3 hollow spheres and nanosheet (NS). S29

30 Z (ohm) NS Single Double Triple Quad Quin /2 (Hz -1/2 ) Figure S20. The relationship between Z' and square root of frequency (ω -1/2 ) in the low-frequency region. The sodium ion diffusion coefficients (D) of multi-shelled Fe2(MoO4)3 hollow sphere and NS are calculated according to the following equation: R 2 T 2 D = 2A 2 n 4 F 4 C 2 σ 2 where R is the gas constant, T is the absolute temperature, A is the surface area of the cathode, n is the number of electrons per molecule during oxidization, F is Faraday s constant, C is the concentration of the lithium ion, and σ is the Warburg factor which has a relationship with Z': Z = R D + R C + σω 1/2 S30

31 Figure S21. TEM images of the morphology of (a) double-, (b) triple-, (c) quadruple-, (d) quintuple-shelled Fe2(MoO4)3 hollow sphere after 100 cycles. After 100 cycles, the morphology of multi-shelled hollow sphere can be retained perfectly, which make sure the superior cycling performance, it is ascribed to ability to mitigate the strain during charge and discharge process. S31

32 Figure S22. XRD analysis of quintuple-shelled Fe2(MoO4)3 hollow spheres after 100 cycles of charging-discharging, then again charged to 4.0 V or discharged to 1.5 V. After 100 cycles of charging-discharging, the Fe2(MoO4)3 (taking quintupleshelled Fe2(MoO4)3 hollow spheres as an example) based cells were again charged to 4.0 V or discharged to 1.5 V. Then the cells were disassembled and washed with dimethyl carbonate. And then after dry, the powder on the electrode film was collected for X-ray diffraction (XRD) characterization. As shown in Figure S22, even after 100 cycles of charging-discharging, when the quintuple-shelled hollow spheres were again charged to 4.0 V, most of the peaks can be assigned to Fe2(MoO4)3, indicating the good phase-reversibility of the hollow spheres. Meanwhile, we would like to point out that Na2Fe2(MoO4)3 can also be detected, which is reasonable given that sodium ions cannot be totally extracted leading to the slight capacity decay after 100 cycles. Besides, when the quintuple-shelled hollow spheres were again discharged to 1.5 V after 100 cycles, only Na2Fe2(MoO4)3 can be detected, which means all Fe2(MoO4)3 has be fully S32

33 inserted with sodium, indicating the good reversibility of the Fe2(MoO4)3 hollow spheres. S33

34 References [1] Wang, S.; Dou, K.; Dong, Y.; Zou, Y.; Zeng, H. Int. J. Nanomanuf. 2016, 12, [2] Pramanik, A.; Maiti, S.; Mahanty, S. Chem. Eng. J. 2017, 307, S34