The Impact of Aluminum Doping on the Performance of MgVO Spinel Cathodes for High-Rate Zinc-Ion Energy Storage.

This study explores the development of aluminum-doped MgVO spinel cathodes for aqueous zinc-ion batteries (AZIBs), addressing the challenges of poor Zn ion diffusion and structural instability. Al ions were pre-inserted into the spinel structure using a sol-gel method, which enhanced the material's structural stability and electrical conductivity. The doping of Al mitigates the electrostatic interactions between Zn ions and the cathode, thereby improving ion diffusion and facilitating efficient charge/discharge processes. While pseudocapacitive behavior plays a dominant role in fast charge storage, the diffusion of Zn within the bulk material remains crucial for long-term performance and stability. Our findings demonstrate that Al-MgVO exhibits enhanced Zn diffusion kinetics and robust structural integrity under high-rate cycling conditions, contributing to its high electrochemical performance. The Al-MgVO cathode retains a capacity of 254.3 mAh g at a high current density of 10 A g after 1000 cycles (93.6% retention), and 186.8 mAh g at 20 A g after 2000 cycles (90.2% retention). These improvements, driven by enhanced bulk diffusion and the stabilization of the crystal framework through Al doping, make it a promising candidate for high-rate energy storage applications.