Xu Yongqi, Pan Bingyige, Li Wei-Shi, Dong Lei, Wang Xinping, Zhao Fu-Gang
Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Department of Chemistry, Zhejiang Sci-Tech University, 928 Second Street, Hangzhou 310018, China.
Key Laboratory of Synthetic and Self-Assembly Chemistry for Functional Molecules, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
ACS Appl Mater Interfaces. 2021 Sep 8;13(35):41537-41544. doi: 10.1021/acsami.1c08406. Epub 2021 Aug 24.
The energy density formula illuminated that widening the voltage window and maximizing capacitance are effective strategies to boost the energy density of supercapacitors. However, aqueous electrolyte-based devices generally afford a voltage window less than 1.2 V in view of water electrolysis, and chemically converted graphene yields mediocre capacitance. Herein, multi-electron redox-reversible, structurally stable indanthrone (IDT) π-backbones were rationally coupled with the reduced graphene oxide (rGO) framework to form IDT@rGO molecular heterojunctions. Such conductive agent- and binder-free film electrodes delivered a maximized capacitance of up to 345 F g in a potential range of -0.2 to 1.0 V. The partner film electrode-TiCT MXene which worked in the negative potential range of -0.1 to -0.6 V-afforded a capacitance as large as 769 F g. Thanks to the perfect complementary potentials of the IDT@rGO heterojunction positive electrode and TiCT MXene negative partner, the polyvinyl alcohol/HSO hydrogel electrolyte-based flexible asymmetric supercapacitor delivered an enlarged voltage window of 1.6 V and an impressive energy density of 17 W h kg at a high power density of 8 kW kg, plus remarkable rate capability and cycling life (capacitance retention of ∼90% after 10000 cycles) as well as exceptional flexibility and bendability.
能量密度公式表明，拓宽电压窗口和使电容最大化是提高超级电容器能量密度的有效策略。然而，鉴于水电解，基于水系电解质的器件通常提供小于1.2 V的电压窗口，并且化学转化的石墨烯产生的电容一般。在此，多电子氧化还原可逆、结构稳定的阴丹酮（IDT）π骨架与还原氧化石墨烯（rGO）框架合理耦合，形成IDT@rGO分子异质结。这种无导电剂和无粘合剂的薄膜电极在-0.2至1.0 V的电位范围内提供高达345 F g的最大电容。在-0.1至-0.6 V的负电位范围内工作的配对薄膜电极-TiCT MXene-提供高达769 F g的电容。由于IDT@rGO异质结正极和TiCT MXene负极配对的完美互补电位，基于聚乙烯醇/HSO水凝胶电解质的柔性不对称超级电容器在8 kW kg的高功率密度下提供了1.6 V的扩大电压窗口和17 W h kg的令人印象深刻的能量密度，以及出色的倍率性能和循环寿命（10000次循环后电容保持率约为90%）以及卓越的柔韧性和可弯曲性。
