Freshwater scarcity demands desalination technologies that are efficient, scalable, and sustainable. Capacitive deionization (CDI) is promising but remains limited by inefficient ion adsorption and poor charge utilization. Here, we show that suitably chosen polyampholytic block copolymer grafting to the internal pore surfaces of CDI electrodes can substantially enhance CDI performance, via a combination of dipolar response and steric effects. Using mean-field classical density functional theory and grand-canonical Monte Carlo simulations, we demonstrate that such polymer grafted electrodes enable strongly improved desalination performance, without altering the pore width and geometry. Even an electrode grafting by simple neutral polymers can generate an improvement, although a suitably designed diblock polymer sequence offers an additional performance gain. These results establish interfacial block copolymer grafting as a powerful route toward high-performance, membrane-free desalination.