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Electrochemical properties of poly(ethylene oxide) electrolytes above the entanglement threshold
Solid State Ionics ( IF 3.0 ) Pub Date : 2021-04-24 , DOI: 10.1016/j.ssi.2021.115609
Kevin W. Gao , Nitash P. Balsara

Ion transport in electrolytes depends on three transport coefficients, conductivity (κ), salt diffusion coefficient (D), and the cation transference number with respect to the solvent velocity (t+0), and the thermodynamic factor (Tf). Current methods for determining these parameters involve four separate experiments, and the coupled nature of the equations used to determine them generally results in large experimental uncertainty. We present data obtained from 64 independent polymer electrolytes comprising poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. The molecular weights of PEO ranged from 5 to 275 kg mol−1; these samples are all above the entanglement threshold. We minimize the experimental uncertainty in transport and thermodynamic measurements by exploiting the fact that ion transport in entangled polymer electrolytes should be independent of molecular weight. The dependence of κ, D, t+0, and Tf as a function of salt concentration in the range 0.035 ≤ r ≤ 0.30 are presented with a 95% confidence interval, where r is the molar ratio of lithium ions to ethylene oxide monomer units. While κ, D, and Tf are all positive as required by thermodynamic constraints, there is no constraint on the sign of t+0. We find that t+0 is negative in the salt concentration range of 0.093 ≤ r ≤ 0.189.



中文翻译:

纠缠阈值以上的聚(环氧乙烷)电解质的电化学性质

电解质中的离子迁移取决于三个迁移系数,即电导率(κ),盐扩散系数(D)和相对于溶剂速度的阳离子迁移数(Ť+0)和热力学因子(T f)。用于确定这些参数的当前方法涉及四个单独的实验,并且用于确定它们的方程式的耦合性质通常导致较大的实验不确定性。我们提供了从包括聚环氧乙烷(PEO)和双(三氟甲磺酰基)亚胺锂(LiTFSI)锂的64种独立的聚合物电解质中获得的数据。PEO的分子量在5至275 kg mol -1之间; 这些样本都高于纠缠阈值。通过利用纠缠的聚合物电解质中离子迁移应独立于分子量的事实,我们将迁移和热力学测量中的实验不确定性降至最低。的依赖κdŤ+0Ť ˚F盐浓度的范围0.035≤函数 [R  ≤0.30都带有95%的置信区间,其中[R是锂离子的环氧乙烷单体单元的摩尔比。根据热力学约束条件,虽然κDT f均为正,但对的符号没有约束Ť+0。我们发现Ť+0是在0.093≤的盐浓度范围负 ř  ≤0.189。

更新日期:2021-04-24
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