Optimizing Electrochemically Active Surfaces of Carbonaceous Electrodes for Ionogel Based Supercapacitors

Abstract

Ionic liquids (ILs) or solidified ionic liquids, known as ionogels, have been actively employed in supercapacitors (SCs) owing to their superior electrochemical stabilities to aqueous and organic electrolytes. However, initial efforts of using ILs and ionogels in SCs were not successful because bulky and sluggish ions cannot effectively access tiny pores of conventional microporous carbons. To address this, a strategy is developed to optimize the electrochemically active surfaces of carbonaceous electrodes and thus to improve the energy storage performance by incorporating 3D ordered/interconnected large mesoporous carbons with ionogel electrolytes. Precisely designed large mesopores interconnected via windows promote mass transport of the electrolyte ions within the solid ionogel electrolytes and effectively utilize the surface of the carbon electrodes for capacitive energy storage, giving rise to record‐high energy storage performance that surpasses the upper bound of the Ragone plots of the current state‐of‐the‐art SCs. In addition, all‐solid‐state SCs with outstanding bending/folding durability are successfully demonstrated. Overall, these results provide critical insight into surface utilization of carbon electrodes as well as capacitive energy storage, when viscous and bulky ILs or ionogels are used as electrolytes.

Ionic Liquid Electrolytes for Electrochemical Energy Storage Devices

“…Furthermore, PVdF-HFP/[EMI][BF 4 ] achieved an improved specific capacitance of 323 F g −1 at 4 V by optimizing the electrochemically active surface of the carbonaceous electrodes. To achieve an electrochemically high performance, this research proposed morphological manipulation for controlling carbon electrode materials to be suitable for IL electrolytes [ 97 ].…”

3D Printable, Highly Stretchable, Superior Stable Ionogels Based on Poly(ionic liquid) with Hyperbranched Polymers as Macro-cross-linkers for High-Performance Strain Sensors

“…Generally, conductive hydrogels are the most widely used 3D printable ionic conductive gel materials with high ionic conductivity, high stretchability, and good biocompatibility. − However, the obtained hydrogels often suffer from poor stability, unstable electrical performance, and narrow temperature range, limiting their long-term application. − Compared to ionic conductive hydrogels, ionogel, as a new type of ionic conductive gel materials based on ionic liquid (IL), − is one of the most promising candidate flexible electrodes/electrolytes for use in wearable electronic devices because of their big advantages such as wide electrochemical windows, excellent electrochemical and thermal stability, nonvolatility, and nonflammability. − Some recent reported stretchable ionogels with double networks (DN) show high stretchability (>1000%); however, the complex preparation process and steps will make it hard to be prepared by using in situ 3D print technique. , Moreover, some kinds with physical networks show poor thermomechanical stability and narrow temperature tolerance (−20–100 °C), , and the elasticity modulus sharply decreases with increasing temperature, , even ionogels change into solutions at higher temperature, which severely limits their long-term application . Importantly, single network (SN) chemical ionogels can be prepared by in situ photopolymerization methods and show good stability, excellent durability, and relatively high electrochemical performance. , In our previous work, chemically cross-linked liquid crystalline nanocomposite ionogels with superior ionic conductivity and high thermomechanical stability have been successfully fabricated via an in situ photopolymerization method .…”

Controlling Morphologies and Structures of PANI@Carbon with Superior Rate Performance for Supercapacitors

“…Supercapacitors mainly consist of electrodes, electrolyte, and a membrane. The electrode material is the most important factor affecting the energy storage performances of supercapacitors and is normally divided into the electric double layer and pseudocapacitance. − The former involves carbon materials with lower energy density and longer service life than the latter. Metal–organic frameworks (MOFs) are considered potential precursors to prepare activated porous carbon (PC) with adjustable morphologies and pore structure because of their outstanding structure advantages as templates. , For example, a hierarchically ordered PC material from ZIF-8 was prepared by the template method to increase the macropore structure and displayed an ultrahigh capacitance of 475.5 F g –1 at 0.5 A g –1 .…”