Three-Dimensional Hierarchical Core/shell Electrodes Using Highly Conformal TiO₂ and Co₃O₄ Thin Films for High-Performance Supercapattery Devices

The rational design and development of novel electrode materials with promising nanostructures is an effective technique to improve their supercapacitive performance. This work presents high-performance core/shell electrodes based on three-dimensional hierarchical nanostructures coated with conformal thin transition-metal oxide layers using atomic layer deposition (ALD). This effective interface engineering creates disorder in the electronic structure and coordination environment at the interface of the heteronanostructure, which provides many more reaction sites and rapid ion diffusion. At 3 A g–1, the positive CuCo2O4/Ni4Mo/MoO2@ALD-Co3O4 electrode introduced here exhibits a specific capacity of 1029.1 C g–1, and the fabricated negative Fe3O4@ALD-TiO2 electrode significantly outperforms conventional carbon-based electrodes, with a maximum specific capacity of 372.6 C g–1. The supercapattery cell assembled from these two interface- and surface-tailored electrodes exhibits a very high energy density of 110.4 W h kg–1 with exceptional capacity retention over 20,000 cycles, demonstrating the immense potential of ALD for the next generation of supercapacitors.