Lead-acid batteriesare a type of rechargeable battery that use lead dioxide (PbO2) as the cathode, sponge metallic lead (Pb) as the anode, and sulfuric acid (H2SO4) as the electrolyte. Known for their reliability and relatively low cost, they are among the most widely used rechargeable batteries. These batteries operate by reversible chemical reactions between the electrodes and the electrolyte, allowing them to store and release energy efficiently. 

Despite their weight and limited lifespan, lead-acid batteries offer significant advantages such as cost-effectiveness, high capacity, and established technology. They find extensive applications in various fields including automotive for starting, lighting, and ignition systems; uninterruptible power supply (UPS) systems for backup power; telecommunications for ensuring network reliability during outages; and renewable energy storage to balance generation and consumption. 

Modern advancements like sealed lead-acid (SLA) and absorbed glass mat (AGM) technologies have further enhanced their safety, performance, and maintenance requirements. While facing competition from newer technologies like lithium-ion batteries, lead-acid batteries continue to hold a crucial position in many applications due to their unique benefits.