A downhole drilling system is disclosed. The downhole drilling system may include a drill bit including a first electrode and a second electrode. The downhole drilling system may also include a pulse-generating circuit coupled to the first electrode and the second electrode. A capacitor within the pulse-generating circuit may include a plurality of electrode sheets and a plurality of dielectric sheets interleaved with the plurality of electrode sheets. Each of the dielectric sheets may include a composite material including a polymer matrix formed from a polymer component and a nanoparticle component that increases the dielectric constant of the composite material above that of the polymer component.