Ishikawa Toru, Haga Shohei, Shigenobu Keisuke, Sudoh Taku, Tsuzuki Seiji, Shinoda Wataru, Dokko Kaoru, Watanabe Masayoshi, Ueno Kazuhide
Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa, 240-8501, Japan.
Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama, Okayama, 700-8530, Japan.
Faraday Discuss. 2024 Oct 25;253(0):385-406. doi: 10.1039/d4fd00024b.
Li-S batteries have attracted attention as next-generation rechargeable batteries owing to their high theoretical capacity and cost-effectiveness. Sparingly solvating electrolytes hold promise because they suppress the dissolution and shuttling of polysulfide intermediates to increase the coulombic efficiency and extend the cycle life. This study investigated the solubility of polysulfide (LiS) in a range of liquid electrolytes, including organic electrolytes, highly concentrated electrolytes, and ionic liquids. The LiS solubility was well correlated with the donor number (DN), estimated Na-NMR, and was lower than 100 mM_(elemental sulfur) in electrolytes with DN < 14, regardless of the type of electrolyte. Highly concentrated electrolytes comprising lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and linear chain dialkyl ethers such as methyl propyl ether (MPE), -butyl methyl ether (BME), and ethyl propyl ether (EPE) were studied as sparingly solvating electrolytes for Li-S batteries. Monomethyl ethers, such as BME, showed more pronounced Li-ion coordination and higher ionic conductivity, whereas the steric hindrance of the longer alkyl chains in EPE lowered the solvation number, enhanced ion association, and lowered the ionic conductivity despite the solvents having similar dielectric constants. The charge-discharge rate capabilities of Li-S cells with dialkyl ether-based electrolytes were more impressive than those of cells with a localized high-concentration electrolyte using sulfolane (SL) and hydrofluoroether (HFE), [Li(SL)][TFSA]-2HFE. The higher rate performance was attributed to the superior Li-ion transport properties of the dialkyl ether-based electrolytes. A pouch-type cell using lightweight [Li(BME)][TFSA] demonstrated an energy density exceeding 300 W h kg under lean electrolyte conditions.
锂硫电池因其高理论容量和成本效益而作为下一代可充电电池受到关注。稀溶剂化电解质具有前景，因为它们抑制多硫化物中间体的溶解和穿梭，以提高库仑效率并延长循环寿命。本研究调查了多硫化物（LiS）在一系列液体电解质中的溶解度，包括有机电解质、高浓度电解质和离子液体。LiS溶解度与供体数（DN）、估计的钠核磁共振良好相关，并且在DN < 14的电解质中，无论电解质类型如何，其低于100 mM_（元素硫）。研究了由双（三氟甲磺酰）亚胺锂（LiTFSA）和线性链二烷基醚如甲基丙基醚（MPE）、丁基甲基醚（BME）和乙基丙基醚（EPE）组成的高浓度电解质作为锂硫电池的稀溶剂化电解质。单甲基醚如BME表现出更明显的锂离子配位和更高的离子电导率，而EPE中较长烷基链的空间位阻降低了溶剂化数，增强了离子缔合，并降低了离子电导率，尽管这些溶剂具有相似的介电常数。使用基于二烷基醚的电解质的锂硫电池的充放电倍率性能比使用环丁砜（SL）和氢氟醚（HFE）的局部高浓度电解质[Li(SL)][TFSA]-2HFE的电池更令人印象深刻。更高的倍率性能归因于基于二烷基醚的电解质具有优异的锂离子传输性能。使用轻质[Li(BME)][TFSA]的软包电池在贫电解质条件下表现出超过300 W h kg的能量密度。
