The development of a novel hybrid symmetric micro-supercapacitor based on poly(3,4-ethylenedioxythiophene) coated silicon nanowires using an ionic liquid PYR₁₃TFSI as an electrolyte has been demonstrated.

In this work, an innovative 3-D symmetric micro-supercapacitor based on polypyrrole (PPy) coated silicon nanotree (SiNTr) hybrid electrodes has been fabricated. First, SiNTrs were grown on silicon substrates by chemical vapor deposition (CVD) and then via an electrochemical method, the conducting polymer coating was deposited onto the surface of SiNTr electrodes. This study illustrates the excellent electrochemical performance of a hybrid micro-supercapacitor device using the synergistic combination of both PPy as the electroactive pseudo-capacitive material and branched SiNWs as the electric double layer capacitive material in the presence of an aprotic ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide; PYR₁₃TFSI) as the electrolyte. The hybrid device exhibited a specific capacitance as high as ∼14 mF cm⁻² and an energy density value of ∼15 mJ cm⁻² at a wide cell voltage of 1.5 V using a high current density of 1 mA cm⁻². Furthermore, a remarkable cycling stability after thousands of galvanostatic charge–discharge cycles with a loss of approximately 30% was obtained. The results reported in this investigation demonstrated that PPy coated SiNTr-based micro-supercapacitors exhibit the best performances among hybrid micro-supercapacitors made of silicon nanowire electrodes grown by CVD in terms of specific capacitance and energy density.

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.