Solder-reflow resistant solid-state micro-supercapacitors based on ionogels

Abstract

All-solid-state devices and thermal resistance to solder reflow are crucial issues with respect to micro-supercapacitors.While the latter issue can be addressed by using ionic liquids, the former shows promising results by employing the ionogel approach. The present study focuses on a novel formulation of ionogels -for use as solid state electrolytes in micro-supercapacitors with silicon nanowire electrodes -which promotes the crack-free formation of an efficient solid electrolyte onto silicon nanostructures in a single-step sol-gel process. The capacitance obtained was the same as that for a device using non-confined ionic liquid, showing a good wetting of the 3D nanostructured silicon electrodes by the sol precursor of the solid ionogel. The assembled symmetric micro-supercapacitor exhibit very high cycling stability and can sustain the reflow soldering process used in the fabrication of microelectronic devices without compromising their electrochemical performance, and even improving their frequency response.

New electrolyte mixture of propylene carbonate and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N1114 TFSI) for high performance silicon nanowire (SiNW)-based supercapacitor applications

“…3d. The lifetime of the device in this study can be considered as an outstanding value taking into account both the mixture effect and the results reported for pure protic and aprotic ionic liquids with stability values around 70-80% after millions of GCD cycles [4,5,7,8]. Based on the criteria aforementioned, a loss of capacitance of 30% was achieved after 380000 cycles, which can be considered still an excellent result based on EDLCs [39].…”

“…f) Areal capacitance versus scan rate at different working temperatures, 0 C (black square), 20 C (red triangle) and 80 C (blue circle) respectively. average values depending on morphological characteristics of SiNWs and electrochemical conditions) [16], ionic liquids (PYR 13 TFSI, AC: 23 mF cm À2 or EMIM TFSI, AC: 13 mF cm À2 ) [5,33], or ionogels (AC: 60 mF cm À2 ) [8] electrolytes. This tendency demonstrates the potential of this mixture for micro-supercapacitor applications.…”

“…Power and energy density values were ranged from 0.2Á10 3 to 16Á10 3 mWcm À2 (1.4 to 50.8 mWcm À3 ) and from 0.25 to 0.3 mWhcm À2 (0.75 to 0.95 mWhcm À3 ) at current densities ranging from 0.1 to 11 mA.cm À2 respectively. These values were compared to the state-of-the-art using similar studies dealing with silicon nanostructures such as CVD-SiNWs [1,[4][5][6]8,21], silicon nanotrees (SiNTrs) [15] or silicon carbide nanowires (SiCNWs) [34] in presence of various electrolytes. Additionally, a comparison with other micro-supercapacitors based on the functionalization of CVD-SiNWs by using pseudocapacitive materials such as electroactive conducting polymers (PEDOT and PPy) [35,36] or transition metal oxides (MnO 2 ) [37] has been also reported.…”

“…In this direction, ionogel electrolytes, as a new tendency in the field of ionic liquids for energy storage devices, based on sol-gel silica with ionic liquid (EMIM TFSI) demonstrated also their potential to withstand solder reflow process (e.g. 280 C during 40s), which is one of the critical points in the Si-based micro-electronics industry for the integration of components such as micro-supercapacitors [8]. In overall, the performance of SiNW-MSCs using different electrolytes based on organic solvents, ionic liquids or ionogels have attracted a great deal of attention to be integrated as reliable micro-power sources in miniaturized electronic devices [9].…”

Ionic liquid electrolyte for supercapacitor with high temperature compatibility

“…Owing to their unique performance characteristics, SCs are often integrated in microelectronics systems [2]. Many concurrent encapsulation and packaging techniques for printed circuit board (PCB) electronics, such as reflow soldering [3], are high temperature (HT) processes, which require the SC to withstand elevated temperature (more than 100 °C) for a certain period of time [2]. The HT exposure specifically requires an electrolyte that is compatible with harsh temperature and pressure.…”