The development of passivated silicon nanowire (SiNW) based micro-supercapacitor electrodes for on-chip applications using an environmentally benign aqueous electrolyte is reported. The SiNWs, produced by low-temperature (50 °C) electrochemical etching, corrode during charge/discharge cycling in the aqueous environment, but upon coating with a silicon carbide passivation layer, the corrosion is mitigated. The as-formed materials are in electrical contact with the substrate, requiring no additional current collector. The passivated NWs achieve capacitance values up to ∼1.7 mF/cm2 projected area (comparable to state-of-the art carbon based micro-supercapacitor electrodes), exhibit robust cycling stability, and maintain capacitive behavior over a wide range of charge/discharge rates.

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Microsupercapacitors are attractive energy storage devices for integration with autonomous microsensor networks due to their high-power capabilities and robust cycle lifetimes. Here, we demonstrate porous silicon nanowires synthesized via a lithography compatible low-temperature wet etch and encapsulated in an ultrathin graphitic carbon sheath, as electrochemical double layer capacitor electrodes. Specific capacitance values reaching 325 mF cm(-2) are achieved, representing the highest specific ECDL capacitance for planar microsupercapacitor electrode materials to date.

Silicon nano-particle based electrodes are attractive for implementation in lithium ion batteries due to the improvement in specific capacity over the currently used graphite based electrodes. Here we investigate polyacrylic acid (PAA) and lithium polyacrylate (Li-PAA) polymer binders' role in the electrochemical performance of silicon nanoparticle based electrodes. The binders are evaluated in comparison to sodium carboxymethyl cellulose (Na-CMC), and polyether imide (PEI). Large variations in the cumulative irreversible capacity is observed for the different binders after 20 cycles while limiting the alloying capacity to 1000 mA h g −1 . Coulombic efficiencies at the first cycle and upon cycling are optimized for PAA and Li-PAA binders considering the binder proportion and the molecular weight. Coulombic efficiencies greater than 99% are obtained after 5 cycles. In depth physico-chemical characterizations of the binders, electrode slurries, and electrodes are performed. From these characterizations the polymers' mechanical properties, binder partitioning in the electrode, and binder interactions with the silicon particles are elucidated. Through correlation of these results with electrochemical performance, the basis for PAA and Li-PAA binders' behavior is proposed in silicon nano-particle electrodes.