Modeling and simulation of magnesium electrodeposition on TiO₂ nanotubes for Mg-ion microbattery applications

Nanostructured titanium dioxide (TiO₂) has gained recognition as a promising material for advanced microbattery electrodes, attributed to its high surface area and advantageous electrochemical properties. Nonetheless, the impact of electrode geometry and current microdistribution on surface degradation and ion transport remains inadequately understood. This study examines magnesium discharge behavior on TiO₂ nanotube (TiO₂-NTs) substrates through a combined experimental and computational methodology. TiO₂-NTs were synthesized and subjected to electrochemical characterization, and a two-dimensional COMSOL model was developed to simulate Mg²⁺ discharge, incorporating variable nanotube length, mass transport, and reaction kinetics. The simulations demonstrated that nanotube geometry significantly influences current distribution, potentially leading to gap closure and a reduction in active surface area due to non-uniform Mg deposition. Enhanced diffusion coefficients and optimized reaction kinetics facilitated more uniform coverage, whereas deeper nanotubes presented greater challenges for effective ion transport. These findings highlight the critical importance of nano-architectural optimization in the design of high-performance Mg-ion microbatteries.