Phosphoric acid doped conductive polyainiline (PANI)/silica nanocomposites usedas supercapacitor electrodes are tested in this article. The nanocomposites with10.0, 20.0, 40.0, and 60.0 wt % silica nanoparticle loadings were synthesizedvia a facile surface initiated polymerization method. The morphology andchemical structure of the nanocomposites were characterized by scanning electronmicroscopy and Fourier transform infrared spectroscopy. The electrochemicalperformances of the nanocomposites were evaluated by cyclic voltammetry,galvanostatic charge–discharge measurement, and electrochemical impedancespectroscopy techniques. The nanocomposites with a loading of 10.0 wt % silicananoparticles displayed an optimum supercapacitive performances with a maximumgravimetric capacitance of 344.1 F/g at a scan rate of 5.0 mV/s (280.3 F/g forPANI nanoparticles) when normalized to the mass of PANI. Meanwhile, a maximumenergy density of 37.4 Wh/kg (34.7 for pure PANI nanoparticles) at a powerdensity of 430 W/kg (415 W/kg for pure PANI) is obtained from thecharge–discharge measurement at a current density of 1.0 A/g. The effect ofelectrolytes on the electrochemical performances was also studied by usingsulfuric acid and sodium sulfate in aqueous solution, respectively. Apseudocapacitance contribution was observed arising from PANI in the acidH2SO4 electrolyte medium whereas most of the capacitancecame from the electric double layer capacitance in the neutralNa2SO4 electrolyte. In addition, external magnetic fieldwas applied onto the nanocomposite electrode, which showed reduced capacitancesdue to the induced positive magnetoresistance. The cyclic stability studiesrevealed a much more superior stability of the nanocomposites than that of purePANI after 500 charge–discharge cycles.