Correlating between the height of three-dimensional core-shell electrodes and ion transport for their electrochemical performance

Abstract

The height of electrodes for in-situ grown 3D core-shell electrodes on a collector, which can directly affect the transport of electrolyte ions, is an important issue that needs to be concerned. Herein, nanocone Co2(OH)2CO3 (CCH) with different heights were synthesized as representative demos to explore the possible factors, including the height h, ion diffusion coefficient D, and Warburg coefficient σ for addressing the ion transport issue. A compromise balance between the height and ion diffusion coefficient was obtained after a series of dynamic analyses. The results showed that the optimal height of CCH can improve ion transport and shorten the charge transfer distance while avoiding stacking and curling. The best electrochemical performance renders the minimum Warburg and maximum ion diffusion coefficients. Furthermore, in-situ EIS and Raman showed that the active sites of CCH were the exposed Co in octahedral units, which can form linkage of octahedrally-electrolyte upon suitable cycling height can reveal more cations, thereby producing more extraordinary electrochemical performance. This work emphasizes the importance of ion diffusion behavior for electrochemical performance within electrodes. It gives a guide for constructing core-shell electrodes with a high electrochemical performance by engineering the microscopic height of materials.