Oxidation States Regulation of Cobalt Active Sites through Crystal Surface Engineering for Enhanced Polysulfide Conversion in Lithium-Sulfur Batteries

Rujian Xiao; Dan Luo; Jiayi Wang; Han Lu; Heng Ma; Eser Metin Akinoglu; Mingliang Jin; Xin Wang; Yongguang Zhang; Zhongwei Chen

doi:10.1002/advs.202202352

Oxidation States Regulation of Cobalt Active Sites through Crystal Surface Engineering for Enhanced Polysulfide Conversion in Lithium-Sulfur Batteries

Adv Sci (Weinh). 2022 Nov;9(31):e2202352. doi: 10.1002/advs.202202352. Epub 2022 Sep 15.

Authors

Rujian Xiao¹, Dan Luo^{1

2}, Jiayi Wang¹, Han Lu³, Heng Ma⁴, Eser Metin Akinoglu³, Mingliang Jin^{1

3}, Xin Wang^{1

3}, Yongguang Zhang^{3

4}, Zhongwei Chen²

Affiliations

¹ South China Academy of Advanced Optoelectronics, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangdong, 510006, China.
² Department of Chemical Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
³ International Academy of Optoelectronics at Zhaoqing, South China Normal University, Zhaoqing, 526060, China.
⁴ School of Materials Science and Engineering, Hebei University of Technology, Tianjin, 300130, China.

Abstract

In this work, unique Co₃ O₄ /N-doped reduced graphene oxide (Co₃ O₄ /N-rGO) composites as favorable sulfur immobilizers and promoters for lithium-sulfur (Li-S) batteries are developed. The prepared Co₃ O₄ nanopolyhedrons (Co₃ O₄ -NP) and Co₃ O₄ nanocubes mainly expose (112) and (001) surfaces, respectively, with different atomic configurations of Co²⁺ /Co³⁺ sites. Experiments and theoretical calculations confirm that the octahedral coordination Co³⁺ (Co³⁺ _Oh ) sites with different oxidation states from tetrahedral coordination Co²⁺ sites optimize the adsorption and catalytic conversion of lithium polysulfides. Specially, the Co₃ O₄ -NP crystals loaded on N-rGO expose (112) planes with ample Co³⁺ _Oh active sites, exhibiting stronger adsorbability and superior catalytic activity for polysulfides, thus inhibiting the shuttle effect. Therefore, the S@Co₃ O₄ -NP/N-rGO cathodes deliver excellent electrochemical properties, for example, stable cyclability at 1 C with a low capacity decay rate of 0.058% over 500 cycles, superb rate capability up to 3 C, and high areal capacity of 4.1 mAh cm^-2 . This catalyst's design incorporating crystal surface engineering and oxidation state regulation strategies also provides new approaches for addressing the complicated issues of Li-S batteries.

Keywords: crystal surface engineering; lithium-sulfur batteries; oxidation states; polysulfide conversion.

Abstract

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