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Building of hierarchical core-shell hetero-structures is currently the subject of intensive research in the electrochemical field owing to its potential for making improved electrodes for high-performance micro-supercapacitors. Here we report a novel architecture design of hierarchical MnO2@silicon nanowires (MnO2@SiNWs) hetero-structures directly supported onto silicon wafer coupled with Li-ion doped 1-Methyl-1-propylpyrrolidinium bis(trifluromethylsulfonyl)imide (PMPyrrBTA) ionic liquids as electrolyte for micro-supercapacitors. A unique 3D mesoporous MnO2@SiNWs in Li-ion doped IL electrolyte can be cycled reversibly across a voltage of 2.2 V and exhibits a high areal capacitance of 13 mFcm−2. The high conductivity of the SiNWs arrays combined with the large surface area of ultrathin MnO2 nanoflakes are responsible for the remarkable performance of these MnO2@SiNWs hetero-structures which exhibit high energy density and excellent cycling stability. This combination of hybrid electrode and hybrid electrolyte opens up a novel avenue to design electrode materials for high-performance micro-supercapacitors. [ABSTRACT FROM AUTHOR]

Developing flexible solid-state micro-supercapacitors with large potential window is crucial for many technologies. The present study focuses on the synthesis and elaboration of quasi-solid-state (QSS) electrolytes with an electrochemical stability greater than 3.0 V based on functionalized polysiloxane. Their electrochemical behavior was studied with silicon nanowires electrodes. The polysiloxane was functionalized with both ammonium and cross-linkable functions. The nanostructured electrodes were impregnated with a mixture of ionic liquid and functionalized polysiloxane. The crosslinking of the polymer electrolyte was then performed by thermal curing directly within the nanostructured electrodes. The quasi-solid system exhibits very high stability upon galvanostatic cycling i.e. during 100 000 cycles with a cell potential of 3.0 V only a capacitance loss of 2.10−5% per cycle was registered. The performance of this QSS with safe electrolyte is remarkable. [Display omitted] [ABSTRACT FROM AUTHOR]

Silicon nanowires (SiNWs) were successfully coated by uniform, adherent and homogenous ultra-thin crystalline diamond films through microwave enhanced chemical vapor deposition (MWCVD). The as-grown functionalized nanowires were employed as electrodes in a symmetric micro-supercapacitor (MSC) using a protic ionic liquid electrolyte [triethylammonium bis(trifluoromethylsulfonyl)imide; Et 3 NH TFSI]. The electrochemical performance of the device delivered a specific capacitance of 1.5 mF cm − 2 and a power density of 25 mW cm − 2 using an enlarged cell voltage of 4 V. Furthermore, a remarkable cycling stability was evaluated after 1 · 10 6 galvanostatic cycles at a high current density of 10 mA cm − 2 with an excellent capacitive behavior. These results confirm that diamond-coated SiNW micro-supercapacitors exhibit very promising performances dealing with MSCs based on CVD-grown SiNWs. [ABSTRACT FROM AUTHOR]

Abstract: The potential of silicon nanowires (SiNWs) as electrode material for large-voltage window micro-supercapacitors has been investigated. An ionic liquid electrolyte (EMI-TFSI) has been used in order to prevent the previously reported etching of silicon electrodes. Electrochemical oxidation of silicon surface at high anodic potentials leads to an extended operating voltage range (up to 4V) and slightly enhanced specific capacitance of silicon electrodes. The ability of SiNW electrodes to operate at high frequency was demonstrated and a promising specific power of 472μWcm−2 was obtained. [Copyright &y& Elsevier]