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To promote sulfur conversion kinetics by a solid auxiliary redox couple embedded in cathode for Li-S batteries

Abstract

The sluggish kinetics of sulfur conversion reactions in Li-S battery is a critical challenge to its applications. Many researches have been dedicated to promote the conversion process including either functionalized matrix materials in cathodes or redox mediators in electrolytes. Here, by embedding a solid auxiliary redox species, we designed and prepared a composite which can be used as matrix for sulfur cathode. Differing from the conventional method in which all the so-called redox mediator is utilized to be dissolved in electrolyte, we employ a solid auxiliary redox species — a cobalt phthalocyanine complex supported on the graphene structures as skeleton materials of sulfur to promote the conversion kinetics in Li-S batteries. The graphene-Cobalt phthalocyanine hybrid plays a prominent role of promoting the kinetics of polysulfide conversion with multi-functions of reducing the activation energy hill, transferring electron, suppressing shuttle effect, etc. Consequently, the Li-S battery with Graphene-Cobalt phthalocyanine-sulfur cathode showed excellent electrochemical performance over the Graphene-Sulfur cathode. Typically, high initial capacity of 1400 mA h g-1 achieved at 0.1C during initial activation cycle and also, the 1st and 300th cycles capacities at 0.5C are 1116 and 860 mA h g-1 respectively. Additionally, at 0.3C rate, high capacities of 1182 and 869 mA h g-1 are obtained during the 1st and 500th cycles respectively. And, enhanced rate capability has been attained delivering a capacity of 874 mA h g-1 at 2C rate.

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Supplementary files

Article information


Submitted
07 Apr 2020
Accepted
06 May 2020
First published
08 May 2020

Sustainable Energy Fuels, 2020, Accepted Manuscript
Article type
Paper

To promote sulfur conversion kinetics by a solid auxiliary redox couple embedded in cathode for Li-S batteries

G. Girma, J. Fan, P. Xu, R. Yuan, L. Cao, M. Zheng and Q. Dong, Sustainable Energy Fuels, 2020, Accepted Manuscript , DOI: 10.1039/D0SE00553C

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