Major Improvement in the Cycling Ability of Pseudocapacitive Vanadium Nitride Films for Micro‐Supercapacitor

Abstract

on a substrate by deposition methods allowing a fine control of film quality and thickness. [1][2][3] When talking about MSC, the total thickness of the stacked films is below 50 µm (substrate ≈ 500 µm) and the footprint surface (<1 cm 2 ) is controlled by etching technique (top down approach: chemical or plasma etching methods) or localized growth of the active material on current collector (bottom up approach: ink jet printing, electrodeposition).The first MSC was made in 2001 by Yoon et al.: the magnetron sputtering deposition technique was selected to stack electrode material and solid electrolyte on a silicon wafer giving rise to Si/SiO 2 /RuO 2 / LiPON/RuO 2 stacked layers. [4,5] The capacitance retention of this MSC was restricted (<1000 cycles) and the rate capability was limited owing to the low ionic conductivity of the LIPON solid electrolyte [6][7][8] (σ ionic ≈ 10 −6 S cm −1 at room temperature) but the triangular shape of the galvanostatic charge-discharge plot confirmed the pseudocapacitive properties of the RuO 2 /LIPON/RuO 2 MSC. More than 20 years after this first demonstration, it must be said that Vanadium nitride film made using a thin film deposition technique is a promising electrode material for micro-supercapacitor applications owing to its high electrical conductivity and high volumetric and surface capacitance values in aqueous electrolyte. Nevertheless, the cycling stability has to be improved to deliver good capacitance during a large number of cycles. Here, it is shown that vanadium nitride films made by a magnetron sputtering deposition method exhibit remarkable cycling stability (high capacitance retention value after 150 000 cycles), ultra-high rate capability (75% of the initial capacitance at 1.6 V s −1 ), while providing high surface capacitance values (≈1.4 F cm −2 ) and very low ageing of the VN electrodes (no loss of performance after 13 months). Additionally, new findings regarding the location of vanadium oxides species responsible for the charge storage mechanism in pseudocapacitive VN films are revealed by transmission electron microscopy electron energy-loss spectroscopy analyses at the nanoscale.

The Many Deaths of Supercapacitors: Degradation, Aging, and Performance Fading

“…[ 163 ] Recently, VN thin films were cycled in KOH electrolyte with impressive capacitance retention upon 150 000 cycles ( Figure 10 A). [ 164 ]…”

“…capacitance retention and Coulombic efficiency of VN film evaluated during 150,000 cycles at different scan rates (Reproduced with permission. [ 164 ] Copyright 2023, Wiley VCH). Activated carbon (–)//5 m LiNO 3 //MnO 2 (+) asymmetric supercapacitor; B) residual current recorded at different polarization voltages; C) self‐discharge of the cell previously polarized at different cell voltages (A. Morel, D. Bélanger and T. Brousse, unpublished results).…”

“…After that, 150 000 cycles were demonstrated with virtually no fade in capacitance (Figure 10A). [ 164 ]…”

Advances on Microsupercapacitors: Real Fast Miniaturized Devices toward Technological Dreams for Powering Embedded Electronics?

“…Specifically, a lower energy density than the practical requirement is a challenge that limits the application of MSCs. A recent paper published in 2023 shows a significant improvement of the cycling and aging performance of sputtered vanadium nitride films with no loss of the initial capacitance value after 150 000 cycles and no degradation of the electrode performance after 13 months …”

“…A recent paper published in 2023 shows a significant improvement of the cycling and aging performance of sputtered vanadium nitride films with no loss of the initial capacitance value after 150 000 cycles and no degradation of the electrode performance after 13 months. 57 Up to now, there have been no commercially available MSCs delivering sufficient performance for powering miniaturized IoT devices. There are some issues both at the electrode material level and at the electrolyte level.…”