Capacitive Deionization (CDI) has emerged over the years as a robust, energy efficient, and cost effective technology for desalination of water with a low or moderate salt content [2]. The energy efficiency of CDI for water with a salt concentration below approximately 10 g/L is due to the fact that the salt ions, which are the minority compound in the water, are removed from the mixture. Instead, other methods extract the majority phase, the water, from the salt solution. Furthermore, energy release during electrode regeneration (ion release, or electrode discharge) can be utilized to charge a neighboring cell operating in the ion electrosorption step, and in this way energy recovery is possible. As we will explain later in detail, a CDI cycle consists of two steps, the first being an ion electrosorption, or charging, step to purify the water, where ions are immobilized in porous carbon electrode pairs. In the following step, ions are released, that is, are desorbed from the electrodes, and thus the electrodes are regenerated. The basic mechanism underlying capacitive deionization is schematically shown in Fig. 1.