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Increasing the molecular weight of conjugated polyelectrolytes improves the electrochemical stability of their pseudocapacitor gels
Journal of Materials Chemistry A ( IF 11.9 ) Pub Date : 2022-09-21 , DOI: 10.1039/d2ta05053f
Ricardo Javier Vázquez, Glenn Quek, Samantha R. McCuskey, Luana Llanes, Binu Kundukad, Xuehang Wang, Guillermo C. Bazan

Conjugated polyelectrolyte (CPE) hydrogels synergize the electrical properties of redox-active polymers with the physical properties of hydrogels. Of particular relevance is their implementation as pseudocapacitors due to their high ionic conductivity, strong ionic–electronic coupling, and large electroactive surface area. To date, efforts to improve the cycling stability of such hydrogels are predominated by the use of additives – optimization of the CPE's intrinsic properties remains underexplored. Herein, the systematic increase in the molecular weight (MW) of a self-doped CPE, namely CPE-K, has been demonstrated as an effective strategy to enhance the cycling stability of the resulting hydrogel. At high MW, mechanically stronger hydrogels were obtained with a specific capacitance as high as 88 ± 4 F g−1 at 0.25 A g−1 and a cycling stability of 76% capacitance retention after 100 000 cycles at 2.5 A g−1. Furthermore, this strategy yields a wider working pseudocapacitive window, less internal resistance, and higher ionic conductivity within the 3D conductive network. We attribute the enhanced electrochemical performance to stronger inter-chain contacts for optimal morphological organization, as revealed by rheological measurements, resulting in stress-tolerant hydrogels with a higher degree of percolation within a 3D conductive network. These results position CPE-K hydrogels as a state-of-the-art organic material for long-term pseudocapacitive technologies and potentially for the next generation of multi-functional pseudocapacitive devices that go beyond high energy density and power density.

中文翻译:

增加共轭聚电解质的分子量可提高其赝电容器凝胶的电化学稳定性

共轭聚电解质 (CPE) 水凝胶将氧化还原活性聚合物的电性能与水凝胶的物理性能相结合。特别相关的是它们作为赝电容器的实现,因为它们具有高离子电导率、强离子-电子耦合和大电活性表面积。迄今为止,改善此类水凝胶循环稳定性的努力主要是使用添加剂——优化 CPE 的内在特性仍未得到充分探索。在此,自掺杂CPE(即CPE-K)的分子量(MW)的系统增加已被证明是提高所得水凝胶循环稳定性的有效策略。在高 MW 下,获得了机械强度更高的水凝胶,其比电容高达 88 ± 4 F g -1在 0.25 A g -1和 2.5 A g -1下 100 000 次循环后循环稳定性为 76% 的电容保持率. 此外,该策略在 3D 导电网络中产生了更宽的工作赝电容窗口、更小的内阻和更高的离子电导率。正如流变测量所揭示的,我们将增强的电化学性能归因于更强的链间接触以获得最佳形态组织,从而产生在 3D 导电网络中具有更高渗透度的耐应力水凝胶。这些结果将 CPE-K 水凝胶定位为用于长期赝电容技术的最先进的有机材料,并有可能用于超越高能量密度和功率密度的下一代多功能赝电容设备。
更新日期:2022-09-21
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