Design and optimization of pore structure in three-dimensional micro-nano hierarchical SnO supercapacitor electrodes for enhanced ion diffusion.

This paper introduced a novel continuous electrochemical synthesis strategy to address the challenges of slow ion/electron transport rates and low electrode reaction efficiency in Sn-based electrode materials. This approach leveraged the induction and confinement of bubble templates to assist atoms deposition, generating micron-sized tin skeletons. Subsequently, these skeletons were transformed into a secondary nanoporous structure through dissolution-deposition etching effects. From liquid-phase ions to metal skeletons to porous oxides, the sequential material transformations realized the innovative design of three-dimensional (3D) hierarchical structures. This strategy ingeniously exploited the diffusion advantages of the electrolyte in the micro-nano hierarchical structure to achieve the diffusion enhancement of ions, thus solving the "dead surface" problem in the energy storage process. This study revealed the thermodynamic and kinetic feasibility of the constructed 3D micro-nano hierarchical structure through electrochemical evaluations and theoretical calculations, and elucidated the constitutive relationship in which the electrochemical performance of the electrode materials was enhanced with decreasing pore size. In addition, design optimization of pore structures and modelling exploration of pore size limit values were conducted based on density functional theory (DFT) simulations. These simulations demonstrated the advantages of hierarchical structures with controllable pore sizes in facilitating electrolyte ion diffusion, predicting an optimal pore size of 55 μm for 3D hierarchical porous SnO electrodes. The integration of this innovative structural design with simulation insights offered significant implications for enhancing the sluggish electrode reaction kinetics of metal oxide electrode materials, advancing the controllable fabrication of high-performance energy storage devices.