Solid-State Microsupercapacitors Assembled Using Ionic Liquids for Wide Temperature-Range Applications

Abstract

Microsupercapacitors (MSCs) have the potential to serve as power sources or energy storage units in microelectronic devices.1 We have reported a laser micromachining technique to produce in-plane interdigitated microelectrodes for microsupercapacitors, in which the electrode fingers were fabricated using high-porosity activated mesophase pitch.2 The use of an ionogel, comprising an ionic liquid and fumed silica, enables the MSC to reach stack capacitance of 12 F cm-3, stack energy of 16 mWh cm-3, and stack power of 160 W cm-3. These energy and power values are unprecedented for MSCs. The developed laser machining technique is highly scalable, enabling lithography-free fabrication and on-chip integration of MSCs into microelectronic units. We obtained results demonstrating that the laser-patterned interdigitated design substantially reduces the resistance for electrode-electrolyte interfacial diffusion and drift transport through the carbon films. The challenge of solid-state MSCs in versatile applications is the operation temperature range and high thermal stability. In this report, we present the use of an ether-bridged dication ionic liquid as an additive to commercially available ionic liquids to enable operation of MSCs at temperatures ranging from -20 to +60 ºC. The proposed fabrication strategy, using a laser for the micromachining in conjunction with a wide temperature range ionogel, provides an opportunity for the development of robust solid-state MSCs applicable a variety of micro/nano-sized energy devices.