Institut Charles Gerhardt Montpellier, UMR 5253, Université de Montpellier, CC 1502, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.
Université Bordeaux, ISM, CNRS, UMR 5255, F-33400 Talence, France.
Faraday Discuss. 2018 Jan 1;206:393-404. doi: 10.1039/c7fd00174f. Epub 2017 Sep 22.
Nowadays commercial supercapacitors are based on purely capacitive storage at the porous carbons that are used for the electrodes. However, the limits that capacitive storage imposes on energy density calls to investigate new materials to improve the capacitance of the device. This new type of electrodes (e.g., RuO, MnO…) involves pseudo-capacitive faradaic redox processes with the solid material. Ion exchange with solid materials is, however, much slower than the adsorption process in capacitive storage and inevitably leads to significant loss of power. Faradaic process in the liquid state, in contrast can be similarly fast as capacitive processes due to the fast ion transport. Designing new devices with liquid like dynamics and improved specific capacitance is challenging. We present a new approach to increase the specific capacitance using biredox ionic liquids, where redox moieties are tethered to the electrolyte ions, allowing high redox concentrations and significant pseudo-capacitive storage in the liquid state. Anions and cations are functionalized with anthraquinone (AQ) and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) moieties, respectively. Glassy carbon, carbon-onion, and commercial activated carbon electrodes that exhibit different double layer structures and thus different diffusion dynamics were used to simultaneously study the electrochemical response of biredox ionic liquids at the positive and negative electrode.
如今，商业超级电容器基于用于电极的多孔碳的纯电容存储。然而，电容存储对能量密度的限制要求研究新的材料来提高器件的电容。这种新型电极（例如 RuO、MnO…）涉及与固体材料的赝电容法拉第氧化还原过程。然而，与电容存储中的吸附过程相比，固体材料的离子交换要慢得多，并且不可避免地导致功率损耗显著增加。相比之下，由于快速的离子传输，液态中的法拉第过程可以与电容过程一样快。设计具有类似液体动力学和提高比电容的新型器件具有挑战性。我们提出了一种使用双氧化还原离子液体来提高比电容的新方法，其中氧化还原部分与电解质离子连接，允许在液态中具有高氧化还原浓度和显著的赝电容存储。阴离子和阳离子分别用蒽醌（AQ）和 2,2,6,6-四甲基哌啶-1-氧基（TEMPO）部分官能化。使用具有不同双层结构和不同扩散动力学的玻璃碳、洋葱碳和商业活性炭电极来同时研究双氧化还原离子液体在正负极的电化学响应。
