Battery-Type Desalination Behavior Confined Within Capsules for Efficient Capacitive Deionization

Battery-type faradaic materials are considered a class of promising electrodes for capacitive deionization (CDI) due to their superior ability to store ions through redox reactions. However, the desalination potential of such electrode materials has not been fully explored subject to the accessibility, conductivity, stability, etc. Herein, embedded battery material Ag nanoparticles is designed in capsule-structural units composed of graphene and constructed freestanding composite electrodes for CDI. Particularly, these Ag nanoparticles confined in interconnected graphene capsules can be both efficiently accessed by the electrolyte and rationally protected by the capsule networks, significantly unlocking their potential as desalination materials. Impressively, the optimized Ag-involved anodes can achieve an ultrahigh NaCl desalination capacity of ≈360 mg g^-1 (≈218 mg g^-1 for Cl^-) at 1.4 V and exhibit good cycling stability. Moreover, the as-designed anodes also have very competitive desalination capacities for other anions, such as SO2- 4 (≈90 mg g^-1) and CrO2- 4 (≈77 mg g^-1), suggesting the broad applicability of such Ag-involved electrodes. This work shows that the ingenious introduction of space-confined structures is an effective means of unlocking the desalination potential of Ag-based materials, opening up alternative avenues for the development of other high-performance battery-type desalination electrodes.