Gannett Cara N, Kim Jaehwan, Tirtariyadi Dave, Milner Phillip J, Abruña Héctor D
Department of Chemistry and Chemical Biology, Cornell University Ithaca NY 14850 USA
Chem Sci. 2022 Jul 4;13(32):9191-9201. doi: 10.1039/d2sc02939a. eCollection 2022 Aug 17.
Organic electrode materials offer unique opportunities to utilize ion-electrode interactions to develop diverse, versatile, and high-performing secondary batteries, particularly for applications requiring high power densities. However, a lack of well-defined structure-property relationships for redox-active organic materials restricts the advancement of the field. Herein, we investigate a family of diimide-based polymer materials with several charge-compensating ions (Li, Na, K) in order to systematically probe how redox-active moiety, ion, and polymer flexibility dictate their thermodynamic and kinetic properties. When favorable ion-electrode interactions are employed (, soft K anions with soft perylenediimide dianions), the resulting batteries demonstrate increased working potentials and improved cycling stabilities. Further, for all polymers examined herein, we demonstrate that K accesses the highest percentage of redox-active groups due to its small solvation shell/energy. Through crown ether experiments, cyclic voltammetry, and activation energy measurements, we provide insights into the charge compensation mechanisms of three different polymer structures and rationalize these findings in terms of the differing degrees of improvements observed when cycling with K. Critically, we find that the most flexible polymer enables access to the highest fraction of active sites due to the small activation energy barrier during charge/discharge. These results suggest that improved capacities may be accessible by employing more flexible structures. Overall, our in-depth structure-activity investigation demonstrates how variables such as polymer structure and cation can be used to optimize battery performance and enable the realization of novel battery chemistries.
有机电极材料为利用离子-电极相互作用来开发多样化、多功能且高性能的二次电池提供了独特机遇，特别是对于需要高功率密度的应用。然而，氧化还原活性有机材料缺乏明确的结构-性能关系限制了该领域的发展。在此，我们研究了一族含有几种电荷补偿离子（锂、钠、钾）的二酰亚胺基聚合物材料，以便系统地探究氧化还原活性部分、离子和聚合物柔韧性如何决定其热力学和动力学性质。当采用有利的离子-电极相互作用时（例如，软的钾阴离子与软的苝二酰亚胺二阴离子），所得到的电池展现出更高的工作电位和更好的循环稳定性。此外，对于本文研究的所有聚合物，我们证明钾由于其较小的溶剂化壳层/能量而能接触到最高比例的氧化还原活性基团。通过冠醚实验、循环伏安法和活化能测量，我们深入了解了三种不同聚合物结构的电荷补偿机制，并根据与钾循环时观察到的不同程度的改善对这些发现进行了合理化解释。至关重要的是，我们发现最具柔韧性的聚合物由于充放电过程中的活化能垒较小，能够接触到最高比例的活性位点。这些结果表明，采用更具柔韧性的结构可能实现更高的容量。总体而言，我们深入的结构-活性研究表明，诸如聚合物结构和阳离子等变量可用于优化电池性能并实现新型电池化学体系。
