linguistic:voice_change
Batteries

The largest use of lead in the early 21st century is in lead–acid batteries. The lead in batteries undergoes no direct contact with humans, so there are fewer toxicity concerns. People who work in lead battery production or recycling plants may be exposed to lead dust and inhale it. The reactions in the battery between lead, lead dioxide, and sulfuric acid provide a reliable source of voltage. Supercapacitors incorporating lead–acid batteries have been installed in kilowatt and megawatt scale applications in Australia, Japan, and the United States in frequency regulation, solar smoothing and shifting, wind smoothing, and other applications. These batteries have lower energy density and charge-discharge efficiency than lithium-ion batteries, but are significantly cheaper.