Understanding the effects of different microstructural contributions in the electrochemical response of Nickel-based semiconductor electrodes with 3D hierarchical networks shapes

It is well known that exposed surface area, nanoparticles connectivity and its consolidation level in a nanostructure are key points in the enhancement of the electrochemical performance in energy storage devices. The design and optimization of different electrodes with specific microarchitectures (based on the arrangement manipulation of NiO nanoplatelets, used as building blocks), has allowed distinguishing the effects of each microstructural contribution in their final electrochemical responses, overpassing thermal and mechanical mismatches between the semiconductor ceramic structure and the metallic collector. In all cases, the same electroactive material and the same coating technique were used, preventing the interference of secondary phenomena in the EIS studies, and allowing argue over the contribution of the microstructural features incorporated to the electrode (nature and shape of the collector, degree of sintering and consolidation of the ceramic microstructure, incorporation of non-noble metallic nanoparticles and the macro/meso/microposity effect) in the effective profiting of the Faradaic phenomena observed during their cycling. The modification of the Ni-based electrodes allows understanding how microstructural features infer the electron transport and the ion diffusion through the consolidated structure. The EIS analysis proves that the design of the porous hierarchical network of our semiconductors electrodes resulted in a good rate capability (with capacitance values of 1000 F g−1 or 500 C g−1), exhibiting a relaxation time constant (τ0 = 18 ms), while a slight increase of the charge-transfer resistance (Rct = 3.65Ω) is negligible if the exposed surface is high enough to maintain a high ion transport. The inclusion of non-noble nanoparticles, such as Ni NPs, in the NiO semiconductor microstructure and the optimum deposited mass and sintering treatment create a metal-ceramic electrode that enhances both the charge transfer resistance (1.55 Ω) showing relaxation time in the range (τ0 = 11 ms) and maintaining an excellent capacitive behavior (750 F g−1 or 375C g−1) at quick charge/discharge rate.