Nano-Al₂O₃-doped PVA gel polymer electrolytes: A promising route for efficient VRLA battery applications

Aluminium oxide (Al₂O₃) nanoparticles have proven to be extremely promising additive materials for future energy storage due to their good electrochemical and conductance properties. Herein, an Al₂O₃-doped Poly(vinyl alcohol) (PVA) gel electrolyte containing 1, 3, 6, and 9 wt% Al₂O₃ relative to the PVA content, with pure PVA, was prepared and systematically evaluated for application in valve-regulated lead-acid (VRLA) batteries. Among the investigated compositions, the 6 wt% Al₂O₃@PVA gel exhibited the most favourable combination of ionic conductivity and electrochemical performance and was therefore selected for prototype battery evaluation. The characterisation included Fourier transform infrared spectroscopy for the structure of the gel, measurements of ionic conductivity, and a water retention study. Electrochemical techniques like cyclic voltammetry, electrochemical impedance spectroscopy, potentiodynamic polarisation, and galvanostatic charge-discharge were conducted simultaneously to assess how much the ideal loading of nanoscale particles. The first sample of VRLA battery with the optimised gel electrolyte gave the highest discharge capacity of 4.08 mAh at a loading current of 20 mA and at 0.32 Wh kg^-1, a considerable energy density and a power density of 3.2 W kg^-1 as shown in the Ragone plot. The cell was able to maintain about 100% coulombic efficiency, which is quite remarkable for rechargeable batteries. However, the cell's discharge capacity after 500 cycles decreased by nearly 12%, meaning that it still had a strong performance after a number of cycles. Through detailed investigation, these superior features result mainly from the combined effects of Al₂O₃ and PVA, which enhance ion mobility, mechanical resistance, and the effectiveness of electrical transport to charge. Therefore, this development opens up new applications for the lead-acid battery in different domains like renewable energy systems, electric vehicles, and portable devices.