Effect of Intrinsic Pore Distribution on Ion Diffusion Kinetics of Supercapacitor Electrode Surface

The electrolyte ion diffusion kinetics have an important impact on electrochemical energy storage. Herein, we report the effect of the intrinsic porosity of NiCoP on accelerating electrolyte ion diffusion kinetics and accommodating volume expansion during the charge/discharge process. The pore distribution model of electrode/electrolyte was designed and optimized by the finite element simulation, demonstrating the visualization and quantitative analysis of the diffusion process of the electrode/electrolyte interface with intrinsic porous structure. When the pore area ratio reached 50.01%, the theoretical diffusion coefficient of 1.41 × 10^-11 m² s^-1 would be conducive to the rapid diffusion of electrolytes. The electrode gained a specific capacity of 2805 F g^-1 at a current density of 1 A g^-1 based on the measured diffusion coefficient (1.79 × 10^-10 m² s^-1), superior to 1.44-times that of the pristine electrode. The diffusion barriers of intrinsic porous NiCoP (3.19 eV) and conventional NiCoP (47.10 eV) were calculated by the density functional theory calculations, respectively. The intrinsic porous NiCoP was prepared by the hydrothermal treatment, annealing, and phosphating processes. The pore distribution was regulated by the concentration of NaHCO₃ as a pore-forming additive. This work combines simulations and experiments to form a method to optimize diffusion kinetics at the electrode/electrolyte interface.