Microsupercapacitor with a 500 nm gap between MXene/CNT electrodes

Decreasing the size of portable, wearable, and integrated electronics requires subsequent reduction in the accompanying energy storage devices. To further decrease the size of supercapacitors without compromising device performance, adequate materials are required as well as appropriate device design. Traditionally, carbon nanomaterials have been utilized within high-performance electrochemical energy storage applications, however carbides, specifically two-dimensional (2D) transition metal carbides and or nitrides (MXenes) have shown promise. Herein, a focused-ion-beam (FIB) process is used for patterning of titanium carbide (Ti₃C₂) carbon nanotube (CNT) electrodes into a finely controlled coplanar interdigitated configuration. The symmetric micro supercapacitors produced have a narrow, 500 nm gap between the electrode fingers and exhibit high areal capacitance of ~317 mF cm⁻² at a scan rate of 50 mV s⁻¹ and still retain >30% of their capacitance (~104 mF cm⁻²) at 100 V s⁻¹. In addition, electron beam lithography and photolithography are utilized to create almost-invisible devices with ultra-small footprints (0.04 mm² device areas) that can be used for securing electronic components. This study provides a simple and reliable method for fabrication of on-chip symmetric MSCs with coplanar interdigitated electrodes.