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Keywords:

  • hybrid materials;
  • interfaces;
  • nickel cobaltate;
  • nanostructures;
  • supercapacitors

Abstract

Pseudocapacitors bridge the gap between supercapacitors and batteries. Controllable microstructures grown on substrates have achieved success with regard to energy storage. However, traditional designs have only focused on the surface of scaffolds, which results in high specific capacitance values for the electroactive material rather than the electrodes. Inspired by slurry-casting, a dual-scale shell-structured NiCo2O4 on nickel foam was assembled by using a simple and flexible solution-based strategy. First, NiCo2O4 nanosheets covering the Ni foam skeleton surface loosely (the sample is denoted as ′pasted′) is obtained by a solution-grown and ′dip-and-dry′ process (in a cobalt–nickel hydroxide solution) followed by annealing. Secondly, the NiCo2O4 nanosheets are filled in the pores of the Ni scaffold (the obtained material is denoted as ′tailored′) through chemical bath deposition process followed by annealing. The capacitance per weight of electroactive materials is not outstanding (1029 F g−1 at 10 mA cm−2), but is competitive with regard to area (3.23 F cm−2 at 10 mA cm−2). However, features in the cycling performance imply that the electrode exhibits a hybrid supercapacitor–battery behavior and that thermodynamic hysteresis promotes the ’breaking’ and ’fusing’ behavior of the material. The overall design highlights a new pathway to step out from surface to space.