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.

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