Prof. WU Zhongshuai and Prof. FU Qiang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) demonstrated new-concept planar and shapeless micro-supercapacitors by encapsulating high capacitance electrodes within a robust hydrogel matrix. Their study was published in Adv. Funct. Mater.
Electrochemical energy storage devices (EESDs) are currently at the frontier of clean energy research. However, they are not able to keep up with the rapid progress in energy generation and consumption devices due to constraints on their form. The root cause of this problem is the mechanically incompatible adhesion of different electrodes with electrolyte and the substrate.
Moreover, the substrate, although being an inactive component, contributes most to the total weight and volume of the entire device, hindering the high performance of 2D active materials and reducing the total energy output of EESDs. Therefore, it is necessary to innovate new architectures for EESDs that will allow the removal of inactive components and maintain high capacitance of devices with ultrathin geometry.
Substrate-free and shapeless micro-supercapacitors for next-generation electronics (Image by DAS Pratteek)
The researchers from DICP proposed a prototype planar and shapeless micro-supercapacitor (SMSC) by encapsulating ultrathin MXene-based electrodes (5 mm) inside thin film hydrogel electrolyte (37 mm) to realize ultraflexible features along with high capacitance output from a single device. The total areal capacitance of 40.8 mF cm-2, delivered by a single device is among the highest reported value for MXene-based supercapacitors.
Additionally, the flexibility is unparalleled since the device can be bent, folded, spiraled, crumpled and even passed through fluid channels, thanks to its ultrathin and shapeless nature.
Furthermore, this technology is easily scalable not only to other electrode fabrication methods, but also to different active materials as well.
This was validated by the demonstration of 9 series-connected SMSCs with screen-printed graphene electrodes delivering a 7.2 V in an extremely deformed state after crumpling them from 0.11 to 0.01 cm3. Such devices hold promises for finally closing the gap between electronics and EESDs for creating independently powered, next-generation nanomachines for a variety of unprecedented applications.
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