Impedance Characterization of the Transport Properties of Electrolytes Contained within Porous Electrodes and Separators Useful for Li-S Batteries
Impedance Characterization of the Transport Properties of Electrolytes Contained within Porous Electrodes and Separators Useful for Li-S Batteries
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DOI：
10.1149/2.0631811jes
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发表时间：
2018-08-24
影响因子：
3.9
通讯作者：
Garcia-Araez, Nuria
中科院分区：
文献类型：
--
作者：
Raccichini, Rinaldo;Furness, Liam;Garcia-Araez, Nuria
阻抗谱用于表征限制在多孔隔板和可用于锂硫电池应用的碳硫复合电极中的电解质溶液的关键传输特性（有效电导率、麦克马林数、孔隙率和曲折度）。三个相关的电解质浓度，范围在1和5摩尔，进行了研究。阻抗测量在具有两个相同电极的对称单元中进行，这克服了与反参考电极的贡献相关联的复杂性。电解质填充的碳-硫复合物电极可以由“开放”瓦尔堡元件表示，模拟离子通过与电极-电解质界面的双层充电耦合的孔的有限扩散。碳-硫复合物电极处于足够高的电位（约100 V）。3 V vs. Li+/Li），使得在阻抗测量期间不存在硫还原成多硫化物物质的电荷转移反应，因此在低频下观察到电容性行为。结果表明，离子通过多孔结构的传输速率显着依赖于电极的结构和组成以及电解质浓度。对于特定的电极/电解质组合，观察到能够增强多孔复合电极内电解质的有效电导率的协同效应，这与Li-S电池的增强性能相关。(C)作者（S）2018由ECS发布。
Impedance spectroscopy is used to characterize the key transport properties (effective conductivity, MacMullin number, porosity and tortuosity) of electrolyte solutions confined in porous separators and carbon-sulfur composite electrodes useful for application in Li-S batteries. Three relevant electrolyte concentrations, ranging between 1 and 5 molal, are studied. Impedance measurements are performed in symmetrical cells with two identical electrodes, which overcome complications associated with the contributions of the counter-reference electrode. The electrolyte-filled carbon-sulfur composite electrodes can be represented by an "open" Warburg element, modelling the finite-diffusion of ions through the pores coupled to the double-layer charging of the electrode-electrolyte interface. The carbon-sulfur composite electrodes are at a high enough potential (ca. 3 V vs. Li+/Li) so that charge-transfer reactions of sulfur reduction to polysulfide species are absent during the impedance measurements, and hence capacitive-like behavior is observed at low frequencies. The analysis of the results shows that the rate of transport of ions through porous structures is markedly dependent on the electrode's structure and composition as well as the electrolyte concentration. Synergistic effects, able to enhance the effective conductivity of the electrolyte inside porous composite electrodes, are observed for particular electrode/electrolyte combinations, which are correlated to enhanced performance in Li-S cells. (C) The Author(s) 2018. Published by ECS.