Effect of electrolyte composition on the performance of sulfur cathode based on solid-phase conversion mechanism

doi:10.19799/j.cnki.2095-4239.2019.0282

Abstract

Abstract:

Lithium-sulfur battery (Li-S) shows a great promise as a new generation electric energy storage technology due to its very high theoretical energy density (2600 W·h/kg). However, fabricating a sulfur cathode with acceptable high electrochemical utilization and long-term cyclability is a great challenge, mainly due to the unavoidable generation, dissolution and deactivation of soluble lithium polysulfide (PS) intermediates generated during the discharge process. Our previous study has demonstrated that the redox chemistry of sulfur cathodes can be converted from dissolution-deposition mechanism to a solid-phase conversion (SPC) reaction by in situ formation of a thin and compact solid electrolyte interface (SEI) on the sulfur surface through a prompt nucleophilic reaction of soluble PSs with vinyl carbonate (VC) molecule specially designed as a co-solvent in the ether-based electrolyte, thus separating the direct contact of electrolyte with the active sulfur and completely suppressing the generation and dissolution of PSs. To obtain the research results more in line with the practical application, we prepared a high-sulfur loading sulfur/carbon composite cathode (7mg/cm²) in this work, and investigated the influence of electrolyte composition, including VC content and LiTFSI concentration, on the performance of solid-phase conversion sulfur electrode. The experimental results demonstrated that, in a co-solvent electrolyte of 2.5 mol/L LiTFSI + VC/DOL/DME (volume ratio is 10:5:5) with high VC content and high LiTFSI concentration, thus-prepared high sulfur loading cathode can exhibit a high reversible specific capacity of 1090 mA·h/g and excellent cycling performance with a capacity retention of 97.2% after 50 cycles. This study provides a new insight for future development of high sulfur loading, structurally and electrochemically stable sulfur cathodes for new generation advanced Li-S batteries.

Key words: Li-S battery, sulfur electrode, co-solvent electrolyte, solid-phase conversion mechanism, high loading cathode

CLC Number:

TM 911

WU Xiangjiang, HE Feng, CAO Yuliang, AI Xinping. Effect of electrolyte composition on the performance of sulfur cathode based on solid-phase conversion mechanism[J]. Energy Storage Science and Technology, 2020, 9(2): 331-338.

Figures/Tables 5

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种类	VC与醚类溶剂的体积比	LiTFSI浓度/mol·L^-1
“低VC低LiTFSI”电解液	1：10	1.0
“高VC低LiTFSI”电解液	10：10	1.0
“低VC高LiTFSI”电解液	1：10	2.5
“高VC高LiTFSI”电解液	10：10	2.5

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