Determining the Absolute Anodic Stability Threshold of Polymer Electrolytes: A Capacity-Based Electrochemical Method
Determining the Absolute Anodic Stability Threshold of Polymer Electrolytes: A Capacity-Based Electrochemical Method
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DOI：
10.1021/acs.chemmater.0c04248
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发表时间：
2021-03-03
影响因子：
8.6
通讯作者：
Tenhaeff, Wyatt E.
中科院分区：
文献类型：
--
作者：
Li, Zhuo;Zhao, Yineng;Tenhaeff, Wyatt E.
本质上安全、可逆、高能量密度的固态锂金属电池需要在阴极的高电位下具有电化学兼容性的固体电解液。在科学文献中，报道的固体电解质，特别是聚合物材料的阳极稳定性有很大的差异。针对常用的表征方法，如线性扫描伏安法的局限性，本研究引入了一种基于电容的电化学方法，称为可逆性测试，作为确定聚合物电解液阳极稳定性的可靠替代方法。可逆性测试在循环伏安测量期间整合阳极和阴极电流，以通过容量比确定不可逆性(RHO)。当电解液电化学稳定时，容量比不变，但在超过电解液稳定阈值的电位时，容量比发生偏差。用该可逆性测试方法测定了聚氧化乙烯(PEO)和氢化丁二烯橡胶(HNBR)与双(三氟甲磺酰亚胺)锂(LiTFSI)共混物的阳极稳定性分别为3.6V和3.7Vvs Li/Li+。用尺寸排阻色谱验证了PEO的稳定性阈值。当充电电压超过3.6V时，PEO的bar(W)上的(M)单调下降，表明进一步氧化。因此，可逆性试验被确立为一种灵敏和通用的表征聚合物电解质氧化稳定性的方法。
Inherently safe, reversible, energy-dense solid-state lithium metal batteries require solid electrolytes that are electrochemically compatible at the high potentials of the cathode. In the scientific literature, there are significant discrepancies in the reported anodic stabilities of solid-state electrolytes, especially polymeric materials. Addressing the limitations of popular characterization approaches, such as linear sweep voltammetry, this study introduces a capacity-based electrochemical method, termed the reversibility test, as a reliable alternative in determining the anodic stability of polymer electrolytes. The reversibility test integrates the anodic and cathodic currents during a cyclic voltammetry measurement to identify irreversibility (rho) through the capacity ratios. The capacity ratio is unchanged when the electrolyte is electrochemically stable but deviates at potentials exceeding the electrolyte's stability threshold. Using this reversibility test, the anodic stabilities of poly(ethylene oxide) (PEO) and hydrogenated nitrile butadiene rubber (HNBR), both blended with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), were determined to be 3.6 and 3.7 V vs Li/Li+, respectively. The stability threshold of PEO is validated by size exclusion chromatography. At charge potentials exceeding 3.6 V, the (M) over bar (W) of PEO monotonically decreases, indicating further oxidation. Thus, the reversibility test is established as a sensitive and versatile characterization method for determining the oxidative stability of polymer electrolytes.