a capacitive deionization cell comprising a first electrode , an anion membrane adjacent said first electrode forming an anion membrane - electrode conjugate , a cation membrane in spacial relation with said anion membrane defining a fluid flow path between said anion membrane and said cation membrane , and a second electrode adjacent said cation membrane forming a cation membrane - electrode conjugate , wherein said anion membrane - electrode conjugate and said cation membrane - electrode conjugate each have an effective capacitance , and the ratio of the effective capacitance of said cation membrane - electrode conjugate to the effective capacitance of said anion membrane - electrode conjugate is a non - zero number less than 2 .