A capacity-expanding separated interface nerve electrode (SINE) can be used to deliver a nerve conduction block to one or more nerves. The SINE can include a source electrode coupled to a waveform generator. The source electrode can deliver an electrical neuromodulation signal (e.g., a direct current (DC) signal) to an ionically conductive medium. The SINE can also include a vessel holding the ionically conductive medium, which can include a material that facilitates a transformation of the electrical neuromodulation signal to an ionic neuromodulation signal with a high charge capacity. The SINE can also include a nerve interface that can deliver the ionic neuromodulation signal to a nerve. The SINE can be used in combination with a return electrode that is also coupled to the waveform generator.