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An inverted-capacitive deionization (i-CDI) cell of MnO 2 //polypyrrole-coated activated carbon (MnO 2 //PPy@AC) with pseudocapacitive characteristics enables unique salt-removal/salt-concentration capability. The salt adsorption capacity (SAC) of MnO 2 //PPy@AC highly depends on the discharging time and a high SAC of 27.6 mg·g−1 is obtained at the 60-min discharging time. The SAC retention of this unique cell is 100% after 10 charge/discharge cycles at 1.2/0 V. The "memory effect" of MnO 2 //PPy@AC is confirmed by the unchanged conductivity of the cell when the applied cell voltage is interrupted, which has been demonstrated for salt-removal and salt-concentration applications. Unlabelled Image • The pseudocapacitive MnO 2 //PPy system is demonstrated to be an ideal i-CDI cell. • A unique "memorized" capability of MnO 2 //PPy@AC avoids to release counter ions at OCP is demonstrated. • The ion-adsorption time is recognized as the key factor determining the SAC of MnO 2 //PPy@AC. • The memorized MnO 2 //PPy@AC cell shows the salt-removal/-concentration applications. [ABSTRACT FROM AUTHOR]