Femtosecond Laser‐Etched MXene Microsupercapacitors with Double‐Side Configuration via Arbitrary On‐ and Through‐Substrate Connections

Abstract

To obtain high energy and power densities of planar MSCs, a large number of nanostructured materials including activated carbon, [10,11] carbon nanotube, [12][13][14] graphene, [15][16][17] metal oxide, [18][19][20] conductive polymer, [21,22] and their composites [23,24] have been used to construct MSCs. Those with superior volumetric capacitance and power performance are desired.In recent years, electrode engineering approaches to improve the performance of MSCs have also been reported. [25][26][27][28][29][30] A narrow interspace between interdigital electrodes reduces the distance of ions diffusion and the equivalent series resistance of electrodes, leading to improved capacitance and power density of MSCs. [31] The interspace width is dependent on the preparation technologies. Specifically, for current screen printing [26] and inkjet printing, [32,33] the interspace width is over 40 µm. Photolithography technology has achieved an interspace width of 15 µm. [3,34,35] High-precision 3D printing [36,37] and electro-deposition [38,39] have attained an interspace width of 120 and 5 µm, respectively. Laser-based technology having advantages of flexible machining and precise patterning without additional assistance of templates or masks, [40] can accomplish the one-step fabrication of MSCs with interdigital electrodes. [41][42][43] The pioneering work was from Gogotsi group, which reported the preparation of MXene MSCs The capacitance of microsupercapacitors (MSCs) can double if both sides of substrates are used to construct MSCs. Nevertheless, achieving electric connections of MSCs through substrates is a challenge due to the difficulty in precisely positioning each MSC couple that has two of the same MSCs units on two sides. In this work, taking advantage of the synchronous etching on both sides of transparent polyethylene terephthalate substrates by femtosecond laser pulses, a double-sided configuration is attained with high precision in the alignment of back-to-back MSC couples and versatile doubleside MSCs are realized via arbitrary on-and through-substrate connections of MXene MSC units. The MXene double-side MSC fabricated by the series connection of 12 spiral pattern MXene MSC units with interdigital electrodes of 10 μm width interspace can output a large working voltage of 7.2 V. Additionally, femtosecond laser etching brings the transformation of MXene into titania near-etched edges with a lateral distance less than 1 µm. Such a small laser-affected area has little influence on the capacitive performance, which is one of advantages for femtosecond laser over conventional lasers. This research is valuable for one-step manufacturing of highly integrated MSCs in the field of miniaturized energy storage systems.

An Aqueous Anti‐Freezing and Heat‐Tolerant Symmetric Microsupercapacitor with 2.3 V Output Voltage

“…[9][10][11] Accordingly, the working voltage window played a vital role in improving the energy density. Unfortunately, most of the reported MSCs were symmetric and their operating voltage based on aqueous electrolytes were limited to 0.6-1 V. [2,3,[12][13][14] To solve this problem, designs by pairing two different electrodes to fabricate asymmetric MSCs (AMSCs) were proposed to get high working voltages. [15][16][17][18][19][20][21][22] Indeed, these high-voltage AMSCs usually featured a voltage of lower than 1.8 V [15][16][17][18][19][20] and very few AMSCs achieved a maximum operating voltage of 2 V. [21] Furthermore, the fabrication of AMSCs is far more complicated than that of the symmetric MSCs.…”

Laser Synthesis and Microfabrication of Micro/Nanostructured Materials Toward Energy Conversion and Storage

“…Teng et al [ 176 ] combined electrophoresis deposition with laser microfabrication to pattern the activated mesophase pitch carbon integrated with a gel electrolyte on the substrate, which was utilized for the on-chip assembly of micro-supercapacitors. In addition, Wang and Fang et al [ 177 ] fabricated a femtosecond laser-etched MXene MSCs with double-side configuration via arbitrary on- and through-substrate connections of MXene MSC units. The MXene double-side MSC fabricated by the series connection of 12 spiral pattern MXene MSC units with interdigital electrodes of 10 μm width interspace can output a large working voltage of 7.2 V. In contrast to the complexities of necessitating masks and the wet-etching process for photolithography, laser microfabrication process is low-cost, quick, and readily scalable.…”

Two-Dimensional MXene Based Materials for Micro-Supercapacitors

“…Hence, DSMSC with 10 μm interelectrode gap displays the highest volumetric capacitance of 308 Fcm −3 at 5 mVs −1 with ultra-high coulombic efficiency of 96.4% even after 10,000 cycles [70]. Quain and group reported direct writing with pen using additive-free MXene ink on flexible paper and non-paper substrates.…”