Fleur Thissandier

Micro-ultracapacitors with highly doped silicon nanowires electrodes

Highly n-doped silicon nanowires (SiNWs) with several lengths have been deposited via chemical vapor deposition on silicon substrate. These nanostructured silicon substrates have been used as electrodes to build symmetrical micro-ultracapacitors. These devices show a quasi-ideal capacitive behavior in organic electrolyte (1 M NEt4BF4 in propylene carbonate). Their capacitance increases with the length of SiNWs on the electrode and has been improved up to 10 μFcm−2 by using 20 μm SiNWs, i.e., ≈10-fold bulk silicon capacitance. This device exhibits promising galvanostatic charge/discharge cycling stability with a maximum power density of 1.4 mW cm−2.

Novel hybrid micro-supercapacitor based on conducting polymer coated silicon nanowires for electrochemical energy storage

The development of a novel hybrid symmetric micro-supercapacitor based on poly(3,4-ethylenedioxythiophene) coated silicon nanowires using an ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) as an electrolyte has been demonstrated. The hybrid supercapacitor device was able to deliver a specific energy of 10 W h kg−1 and a maximal power density of 85 kW kg−1 at a cell voltage of 1.5 V. The hybrid device exhibited long lifetime and an outstanding electrochemical stability retaining 80% of the initial capacitance after thousands of galvanostatic charge–discharge cycles at a high current density of 1 mA cm−2. The improvement of the capacitive properties compared with the bare SiNWs was attributed to the pseudo-capacitive behavior induced by the conducting polymer coating.