Supporting Information

Polyhedral TiO2 particle-based cathode for Li-S

batteries with high volumetric capacity and high

performance in lean electrolyte

Jaehyun Lee and Jun Hyuk Moon*

Department of Chemical and Biomolecular Engineering, Sogang University, Baekbeom-ro

35, Mapo-gu, Seoul, 04107, Republic of Korea

Corresponding author, E-mail: junhyuk@sogang.ac.kr

Fig. S1. (a, b) SEM image of colloidal crystal of a polymer sphere as a template.

Fig. S2. SEM image of (a,b) 3D, ordered, macroporous TiO2 and (c) poly-TiO2 particles.

Fig. S3. Digital images of (a) poly-TiO2 and (b) nc-TiO2 particles. For samples with the same mass, the poly-TiO2 particles occupy a volume almost 6 times smaller than the commercially available nc-TiO2 nanoparticle

Fig. S4. (a) Schematic illustration of secondary particles of poly-TiO2 and nc-TiO2. (b) TEM image of secondary particles of poly TiO2 and nc-TiO2 particles.

Fig. S5. N2 adsorption-desorption isotherms of nc-TiO2

Fig. S6. XRD patterns of poly-TiO2 / S, poly-TiO2 and sulfur

Fig. S7. Digital images and contact angle images of liquid sulfur on (a) poly-TiO2 and (b) nc-TiO2 films

Fig. S8. Digital image after 0, 3, 6, 12 hours of Li PS solution, and the Li PS solution containing the same mass of nc-TiO2 or poly-TiO2. (5 mmol/g Li2S6 solution containing nc-TiO2 and poly-TiO2)

Fig. S9. High-resolution XPS of S 2p spectra of Li PS-adsorbed nc-TiO2. Compared to nc-TiO2, poly-TiO2 shows a higher intensity shoulder in the 166-171 eV range. This may be due to the relatively large specific area of poly-TiO2.

Fig. S10. TGA curves to 600 °C for poly-TiO2 / S at a rate of 10 °C min-1 in air condition.

Fig. S11. the cross-sectional SEM images of sulfur-impregnated poly-TiO2, nc-TiO2 based electrode and elemental mapping of Ti (pink) and S (yellow).

Fig. S12. SEM image of sulfur-impregnated nc-TiO2 and elemental mapping of Ti (pink) and S (yellow).

Fig. S13. (up) CV curves of nc-TiO2 cathode cell (scan rate of 0.1 mV/s), (down) CV curve of nc-TiO2 cathode cell at various scan rates.

Fig. S14. (a) Charge / discharge profiles at various C rates from 0.1 C to 2 C for nc-TiO2 / S cells. (b) Capacity contributions of high-order polysulfide conversion (Q1) and low-order polysulfide conversion (Q2) and the Q2/Q1 ratios at various C rates for the nc-TiO2 / S electrode cells.

Fig. S15. Comparison of kinetics in Li2S deposition conversion on poly-TiO2 and nc-TiO2

electrodes. We compare kinetics through the response of the cathodic peak (Li2S4 to Li2S) current to the scan rate is related to the rate of the sulfur transformation reaction;. According

to the equation D

Li+¿∝ I p2

S2 n2 CLi2 v

¿

where Ip is the peak current, n is the charge transfer number, S is the geometric area of the active electrode, CLi is the concentration of lithium ions in the cathode, and v is the potential scan rate. The slopes of curves are positively correlated to the corresponding lithium ion diffusion. [1]

Fig. S16. Cycling performance of the nc-TiO2 / S electrode under the lean electrolyte conditions of E / S=6 µL / mg and E/S=2.8 µL / mg. (Volume of elec. solution (E), weight of sulfur (s)).

Fig. S17. The specific capacity of the nc-TiO2 electrode cell according to charging / discharging cycles (sulfur loading = 1.8 mg / cm2)

Table S1. Comparison of TiO2 of various morphologies.

Reference DOI TiO2 morphology BET results

10.1039/C6TA06285G [2]

Hierarchical TiO2 spheres Surface area : 116.6 m2 g−1

Pore volume : 0.55 cm3 g−1

10.1021/acs.iecr.9b03393 [3]

TiO2 @ Hollow Carbon Nanoballs Surface area : 155 m2 g−1

Pore volume : 1.37 cm3 g−1

10.1088/0957-4484/27/4/045403 [4]

TiO2 mesoporous spheres Surface area : 152 m2 g−1

Pore volume : 0.3 cm3 g−1

10.1088/1361-6528/aad543 [5]

TiO2 matrix Surface area : 50.73 m2 g−1

Pore volume : 0.33 cm3 g−1

10.1038/srep22990 (2016) [6]

Hierarchical TiO2 spheres Unknown

10.1002/chem.201404686 [7]

TiO2‐Anchored Hollow Carbon Nanofiber

Surface area : 62.5 m2 g−1

Pore volume : 0.126 cm3 g−1

10.1016/j.electacta.2018.11.030 [8]

TiO2 microcubes Surface area : 98.3 m2 g−1

Pore volume : 0.22 cm3 g−1

10.1016/j.jelechem.2014.11.007 [9]

TiO2 nanofibers Surface area : 12.1 m2 g−1

Pore volume : Unknown

Table S2. Compares the capacity values of recent results with an E / S ratio of less than 15.

Reference Cathode E/S ratio (μL/mg)

Specific capacity

Adv. Energy Mater., 2019, 9, 1803477 [10]

Hollow NiCo2O4 Nanofibers 5 Ca. 700 mAh / g (0.1C, after 100 cycles)

ACS Energy Lett.2018, 3, 3, 568 [11]

Hybrid TiS2-polysulfide cathode 5 466 mAh/g (0.2C, after 200 cycles)

Ca. 550 mAh / g 100cycles

Adv. Funct. Mater., 2019, 29(23), 1901051 [12]

Conductive CoOOH sheet 8 Ca. 700 mAh / g (0.2C, after 100 cycles)

Energy Environ. Sci., 2018, 11, 2372 [13]

Stringed “tube on cube” CNT nanohybrid

3 Ca. 500 mAh / g (0.2C, after 100 cycles)

Nat. Commun., 2017, 8, 482 [14]

2D carbon yolk-shell 15 Ca. 850 mAh / g (1C, after 100cycles)

Energy Environ. Sci., 2019, 12, 3144 [15]

C/TiO2–TiN/S electrodes 6.8 534 mAh/g (0.2C, after 400 cycles)

J. Mater. Chem. A, 2020, Advance Article [16]

Na-PB/CNT electrodes 10 690 mAh/g (0.2C, after 200 cycles)

Our work Polyhedral TiO2

2.8 607 mAh / g (1C, after 100 cycles)

6 759 mAh / g (1C, after 100 cycles)

12 790 mAh / g (1C, after 100 cycles)

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