Block polymer (BP) electrolytes offer significant advantages relative to existing liquid or polymer electrolytes due to their independently tunable ion transport and mechanical stability properties as a result of nanoscale self-assembly. Many of these nanostructured electrolytes are composed of a BP that is doped with a lithium salt to impart conductivity but which also alters the self-assembly (structure and thermodynamics) in comparison to the neat BP. By elucidating the effects of lithium salt concentration and counterion chemistry on the relevant salt and polymer density distributions, BP electrolytes with more efficient conductivity pathways can be developed. In this work, neutron and X-ray reflectometry (NR and XRR, respectively) were harnessed to determine the spatial distribution of salt and polymer in lamellae-forming polystyrene-block-poly(oligo-oxyethylene methacrylate) [PS-b-POEM] films doped with various lithium salts. From the NR results, the distribution of lithium salts across domains appeared to match that of the POEM in the BP electrolyte for all salts tested. This finding of a salt distribution that was directly proportional to the POEM density profile facilitated quantitative analysis of polymer and salt XRR profiles using a strong-segregation theory framework. Through this approach, effective Flory–Huggins interaction parameters (χ_eff)s were deconvoluted from POEM statistical segment lengths (b_POEM)s. For all salts tested, χ_eff increased at low salt concentrations and then plateaued at higher salt concentrations, while b_POEM increased linearly across all salt concentrations. These findings can be leveraged to advance the next generation of salt-doped BP electrolyte materials that enhance the performance and mechanical stability of lithium-ion batteries.

中文翻译：

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定量分析纳米结构离子导电嵌段聚合物中的锂盐和聚合物密度分布

相对于现有的液体或聚合物电解质，嵌段聚合物（BP）电解质具有显着的优势，这归因于其由于纳米级自组装而可独立调节的离子传输和机械稳定性能。这些纳米结构电解质中的许多是由掺杂有锂盐以赋予导电性的BP组成的，但与纯BP相比，它也改变了自组装（结构和热力学）。通过阐明锂盐浓度和抗衡离子化学对相关盐和聚合物密度分布的影响，可以开发出具有更高效电导率途径的BP电解质。在这项工作中，利用中子和X射线反射法（分别为NR和XRR）来确定形成薄片的聚苯乙烯中盐和聚合物的空间分布。掺杂有各种锂盐的嵌段聚（甲基-氧-氧乙烯甲基丙烯酸酯）[PS- b -POEM]薄膜。从NR结果来看，对于所有测试的盐，锂盐跨域的分布似乎与BP电解质中POEM的分布相匹配。盐分布与POEM密度分布成正比的发现有助于使用强分离理论框架对聚合物和盐XRR分布进行定量分析。通过这种方法，有效的Flory-Huggins相互作用参数（_χeff）从POEM统计段长度（b _POEM）中反卷积。对于所有测试的盐，χ _EFF增加在低盐浓度，然后在更高的盐浓度下趋于稳定，而b _POEM在所有盐浓度下均呈线性增加。这些发现可用于推进下一代盐掺杂的BP电解质材料，这些材料可增强锂离子电池的性能和机械稳定性。