Sn Wears Super Skin: A New Design For Long Cycling Batteries

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1 Supporting Information Wears Super Skin: A New Design For Long Cycling Batteries Shuai Kang, Xi Chen, Junjie Niu* Department of Materials Science and Engineering, CEAS, University of Wisconsin-Milwaukee Milwaukee, WI 53211, USA. niu@uwm.edu This PDF file includes: Figures S1 to S10, Table S1 Figure Legends 1

2 Supplementary Figures and Legends: a (a) (b) ( 2 00) 5 nm O 2-x 50 nm (c) 500 nm 5 nm (d) 200 nm Figure S1. Morphology analysis of the commercial particles. TEM images at (a) low and (b) high magnifications, indicating an amorphous oxide layer of 3-5 nm. SEM images at (c) low and (d) high magnifications. Electron microscopy images show the particle has a spherical shape with an average diameter of ~150 nm (ranging from 50 to 200 nm). 2

3 (a) Si Intensity / a.u. C O Ir Ti Ti Energy / ev (b) Weight / % Melting point of 347 o C 240 o C Dehydration 1.3 % 505 o C Temperature / o C Oxidation of 21.5 % Time / minute 600 o C Figure S2. Component and structure anatomy of the hybrid composites. (a) EDS spectrum of the composites. The Si is from the substrate. C is from the carbon tape and Ir is from the conductive coating during sample preparations. (b) TG-DSC data of the composites tested from room temperature to 600 C at a heating rate of 5 C/min and then hold at 600 C in air. (c) Schematic of a typical hybrid composite with a total size of ~180 nm along with a ~130 nm kernel and a ~5 nm TiO 2 skin. A 76.6 wt% of the with a sufficient space was calculated, which allows it to accommodate the maximum volume expansion of 260% DSC / mw mg -1 (c) TiO nm 130 nm m =76.6% 5 nm The EDS data demonstrate the existence of, Ti and O in the composite. The TG-DSC results indicate the weight evolution of composites. First, the sample went through a dehydration process, displaying a weight loss of 1.3 wt% at 220 C. Then, a typical melting peak was observed at 240 C. A negligible weight loss was then found along with two exothermic and one endothermic peaks, which correspond to the TiO 2 phase transformation from amorphous to 3

4 anatase (347 C) and to rutile (505 C), respectively. After 600 C, the weight percentile was stabled at 120% due to the almost saturated oxidation, which makes the total weight increase of 21.5%. Here we assume that all in the composite was oxidized to O 2. In the following equations, m is the overall mass. is the mole weight of O 2, g/mol. mo m = m 2 m = M Thus, m M O 2 O m = 0.796m 2 M is the mole weight of, which is g/mol, and M O2 That means, the mass percentile of is 79.6% on the basis of TG-DSC results, which is closed to the calculation in (c). 4

5 (a) Before annealing 180 o C 250 o C 300 o C 350 o C 400 o C 450 o C 500 o C (b) / mah g / mah g h 2 h 0.5 h 3 h Cycle number (c) Cycle number 20 ml 40 ml 60 ml 80 ml 100 ml / mah g Cycle number Figure S3. Annealing temperature, reaction time and acid etching effects on the battery performance at 0.5 C. (a) Battery cycling performance with varying annealing temperatures for 10 minutes (the heating/cooling speed is 10 C/min). (b) Battery cycling performance with varying reaction time (0.025 ml TiOSO 4 and 0.1 ml H 2 SO 4 in a 30 ml DI water solution). (c) Battery cycling performance with different H 2 SO 4 (0.5 mmol/l) amounts in the acid etching step. As can be observed from the battery cycling performance, an optimized condition of annealing temperature of 400 C, a reaction time of 1 h and a 60 ml H 2 SO 4 etching for a maximum battery capacity under long cycling is determined. 5

6 1000 Commercial / ma h g Cycles Figure S4. The coin cell cycling performance with commercial particles at 0.5 C. 6

7 C C Potential / V st cycle 10 th cycle 100 th cycle 1000 th cycle 3000 th cycle Potential / V st cycle 10 th cycle 100 th cycle 1000 th cycle 3000 th cycle Specific capacity / Specific capacity / C C Potential / V st cycle 10 th cycle 100 th cycle 1000 th cycle th cycle Potential / V st cycle 10 th cycle 100 th cycle 1000 th cycle th cycle Specific capacity / mahg Specific capacity / Figure S5. The charge/discharge curves of the hybrid composite batteries with long-term cycling. 7

8 / mah g mg cm -2 1 mg cm -2 2 mg cm -2 3 mg cm C / mah g mg cm -2 1 mg cm -2 2 mg cm -2 3 mg cm -2 1 C Cycle number Cycle number Figure S6. Active material loading effects on the battery cycling performance at 0.5 C and 1.0 C, respectively. 8

9 (a) (b) 100 nm 100 nm Figure S7. Ex-situ TEM observations of the structure evolution of hybrid composites upon lithiation. (a) Before and (b) after lithiation (discharging stop at 0.01V after the battery ran 100 cycles at 0.5 C). A good accommodation from the cage is clearly observed upon a large volume expansion from the kernel. 9

10 (a) (b) 500 nm 500 nm Figure S8. SEM images of the hybrid composites. (a) Before and (b) after charging/discharging 100 cycles at 0.5 C. The inset in (a) is the enlarged morphology of a broken composite cage. No obvious morphology changes indicate an excellent mechanical stability of the spherical hybrid composite upon long cycling. 10

11 Figure S9. Component and morphology evolution of the hybrid composites. (a) and (b), HAADF-STEM images and the corresponding element mappings of, C, O, Ti and F of different individual composites after charging/discharging 100 cycles at 0.5 C. Compared to the initial shape in Fig. 2, it shows a similar cage configuration with negligible deformation and crack of the kernel, indicating a great electro-chemo-mechanical property. 11

12 (a) Intensity / a.u. 3p 3 O KL 1 3p 1 3s 3p 3 O KL 1 F KL 1 3p 1 F 1s 3s 3d 3d 5 3 O 1s Ti 2s Ti 2p 3d 5 3d 3 O 1s Ti 2s Ti 2p Before cycling O 2s 4d C 1s 4s 4p After cycling O 2s 4d C 1s 4s 4p (b) Intensity / a.u. F 1s (LiF) F 1s (LiPF 6 ) Measured l Background l Fitted Binding Energy / ev Binding Energy / ev Figure S10. Chemical composition evolution of the hybrid composites. (a) XPS survey of the anode electrode material before and after charging/discharging 100 cycles. F peaks are marked with red circles. (b) Measured and fitted high-resolution XPS spectra of F1s from the electrode material after charging/discharging 100 cycles. Before cycling, the presence of, O, and Ti are confirmed. The appearance of F from LiF after cycling is regarded from the formed SEI layer on the outer surface of composites. The F from LiPF 6 is considered from the electrolyte residuals. 12

13 Table S1. Coin cell battery performance comparison. Initial capacity/ after 50 cycles/ after 100 cycles/ after 200 cycles/ after 500cycles/ after 1000cycles/ after 3000cycles/ after 5000cycles/ Reference /CNTs (2C) Ultra-small /C (0.2C) /Graphene (1C) /TiO 2 (0.5C) /TiO 2 (5C) /TiO 2 (10C) Ref Ref Ref Ref Ref This work This work This work References: 1. Huang, X.; Cui, S.; Chang, J.; Hallac, P. B.; Fell, C. R.; Luo, Y.; Metz, B.; Jiang, J.; Hurley, P. T.; Chen, Angew. Chem. Int. Ed. 2015, 54, Qin, J.; He, C.; Zhao, N.; Wang, Z.; Shi, C.; Liu, E.-Z.; Li, J. ACS Nano. 2014, 8, Zhang, Y.; Jiang, L.; Wang, C. Nanoscale 2015, 7, Wang, C.; Li, Y.; Chui, Y.-S.; Wu, Q.-H.; Chen, X.; Zhang, W. Nanoscale 2013, 5,