No abstract

No abstract

Simultaneously regulating the physical properties and chemical environment of interlayer is a critical need for enhancing the capacity and stability of layered electrode materials in energy and environmental applications. Herein, the intercalation of n-alkylamine with different alkyl chain lengths to the structure of layered Na 0.71 CoO 2 (NCO) for application in capacitive deionization is reported. The amine intercalation via acid−base reaction routes allows the expansion of layer spacing of NCO, increase the active site of Na + ions storage, reduce the diffusion energy barrier of Na + ions, improve the electronic conductivity, and suppress the structural deformation of NCO upon the desodiation/sodiation processes. Benefiting from these features, the n-propylamine-intercalated NCO delivered a high capacity of 88.9 mg g −1 and a comparable energy consumption of 0.54 kW h kg −1 . A combination of mechanism analyses and density functional theory calculations demonstrated that the synergistic effects of electrical and ionic conductivity account for the enhanced properties. Our work provides a strategy for engineering the interlayer to enable high capacity and cycling stability, which offers guidance for the design of preintercalated electrode materials.

Faradaic deionization (FDI) provides an effective solution to respond to the global water crisis. However, the ions intercalation/ deintercalation process with multiple redox reactions leads to structural collapse and unstable cyclability. Here, we develop an asymmetrical FDI device assembled by Ca 2+ -decorated Na x CoO 2 (x ≤ 0.71, y ≤ 0.05) as the Faradaic negative electrode and activated carbon as the positive electrode. Na 0.27 Ca 0.03 CoO 2 •0.6H 2 O was synthesized via a facile sol−gel and chemical oxidation method, which delivered a desalination capacity of 83.5 ± 2.4 mg g −1 and a charge efficiency close to 1, and an inappreciable capacity fading was observed after 50 cycles. It is found that the presence of Ca 2+ residing in the face-sharing sites helps to maintain the layered structure and promotes efficient deintercalation of Na + by anchoring the CoO 2 slabs, which results in its unexpected desalination capacity and good cyclability. Moreover, electrochemical quartz-crystal microbalance (EQCM) was successfully used to reveal Faradaic intercalation mechanism.

No abstract

No abstract