Planar micro-supercapacitors toward high performance energy storage devices: design, application and prospects

The burgeoning revolutions of portable and integrated electronic products have drastically stimulated the upgrade of traditional power supplies toward miniaturized scales. In this regard, planar micro-supercapacitors (PMSCs) are considered as candidates for energy storage devices owing to the unique two-dimensional structure, fast charge/discharge rate, high power density and long cycling lifetime. However, the manufacturing of PMSCs requires advanced techniques to provide rational designs on microelectrodes and reduce the size while maintaining high-resolution. The vacuum filtration and spray coating techniques have been used to design millimeter-scale electrodes with the assistance of an interdigital mask. The electrochemical strategy and other mask-free techniques can further reduce the size of the microelectrodes and meet the requirements of high-resolution PMSCs, including electrolytic and electrophoretic deposition, inkjet printing, laser scribing, plasma jet, nanoimprint lithography and 3D printing techniques. The precise design of PMSCs contributes to energy storage devices, sensors and filters. Furthermore, it is vital to design a microelectrode with superior structural integrity for the controllable manufacture of high precision and high performance PMSCs by considering the mechanism and key factors of microfabrication strategies. The well-designed planar micro-supercapacitors can be manufactured through a variety of techniques for the applications in flexible electronics, biosensors, power grids and integrated chips.