Silicon oxide-carbon composites (SiOCCs) were deposited directly in a reactant aqueous solution using a liquidphase plasma (LPP) method and applied as a supercapacitor electrode. The SiOCCs formed rapidly at the initial stages of the LPP reaction by the carbonization of benzene and TMPS, but the production of SiOCC decreased over the reaction time. The SiOCCs formed cluster chains by agglomeration, which were composed mostly of carbon with oxygen and silicon distributed uniformly. A higher TMPS content in the reactant solution resulted in the inclusion of more silicon and oxygen in SiOCCs. Most of the Si components synthesized by the LPP reaction form SiO2 bonds and some have carbon-bonded chemical structures. The SiOCCs particles were agglomerated in amorphous form with a size of approximately 10 to 40 nm and the d-spacing appeared to contain SiO2 particles of approximately 0.31 nm. As the content of silicon oxide in SiOCCs is increased, the specific surface area increased and the specific capacitance increased. In addition, the pseudocapacitance characteristics showed the lowest resistance. On the other hand, a higher silicon oxide content in SiOCCs resulted in higher capacitance loss due to volume expansion of silicon dioxide in the charge-discharge process.