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New 3D symmetric micro-supercapacitors



Within the framework of an international collaboration, we have elaborated new 3D symmetric micro-supercapacitors, based on diamond-coated silicon nanowire electrodes in presence of various aprotic and protic ionic liquid electrolyte.


Published on 5 September 2016
Within the framework of the NEST (Nanowires for Energy STorage) european project (2012 -2016, no. 309143) two teams from INAC (SyMMES/PCI and PhELIQS/SiNAPS), in a tight collaboration with an industrial company (IOLITEC, Heilbronn, Germany) and a technological center (FHG, Freiburg, Germany), have elaborated new 3D symmetric micro-supercapacitors, (MSCs) based on diamond-coated silicon nanowire (SiNW) electrodes in presence of various aprotic and protic ionic liquid electrolytes (e.g. N1114 TFSI and Et3NH TFSI).

Chemical structure of Butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N1114 TFSI) (Left) and Triethylammonium bis(trifluoromethylsulfonyl)imide (Et3NH TFSI) (Right). Both ionic liquids were synthesized and provided by IOLITEC.


The deposition of a nanometric boron-doped diamond film onto SiNW surface, by microwave enhanced chemical vapor deposition (MWCVD), has allowed a clear enhancement of capacitive properties compared to bare CVD-grown SiNWs due to its unique properties in terms of chemical inertness, high active surface, large overvoltage and excellent environmental stability. Accordingly, the electrochemical performance of such devices conducted at the Hybriden platform (Inac), showed a high areal capacitance (1.5 mF cm) and power density (25 mW cm-2) values within a wide operating cell voltage of 4V, as well as a fast charge-discharge rate (ms) [1]. More recently, inspired by our previous works dealing with functionalized SiNWs by conducting polymers (Aradilla et al. RSC Advances, 2014 and Journal of Materrials Chemistry A, 2015), the functionalization of diamond-coated SiNWs by poly(3,4-ethylenedioxythiophene) (PEDOT) has provided an interesting strategy in order to design multi-hierarchical hetero-nanostructures with high energy density, which is one of the most critical factors to design ultra-high performance MSCs by comparison to batteries [2]. Thus, the hybrid device reported an extraordinary value of  26 mJ cm-2 with an outstanding cycling stability (15 000 cycles) taking into account the pseudo-capacitive nature of polymer coating. On the basis of these results, the role of diamond evidences its enormous supercapacitive potential and impressive synergistic effect among electrode-electrolyte interfaces to pave the way to build the next generation of advanced high performance on-chip supercapacitors in the near future.

SEM images of a) SiNWs grown by CVD on highly doped Si substrates (PhELIQS/SiNAPS), b) Diamond-coated SiNWs (FHG) and c) PEDOT coated Diamond@SiNWs (SyMMES/PCI).

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