Lead dioxide

Lead dioxide (PbO₂) is a dark brown or black lead oxide in which lead is formally in the +4 oxidation state. It is a strong oxidizing agent and the positive-electrode active material in lead–acid batteries.

Lead–acid battery: A rechargeable battery whose cells use lead-based electrodes and sulfuric acid electrolyte. Lead dioxide is the positive-electrode material that is reduced during discharge.
Positive electrode: The electrode at which reduction occurs during discharge of a galvanic cell. Lead dioxide is the active material on the positive side of a lead–acid cell.
Lead: A dense, soft, bluish-gray post-transition metal with chemical symbol Pb. Lead dioxide is one of lead’s common oxides and inherits its toxicity.
Lead poisoning: Illness caused by harmful exposure to lead, which can damage multiple organ systems. Battery manufacture, recycling, and waste handling can expose people to lead compounds.
Lead(IV) oxide crystal structure: The rutile-type arrangement of lead and oxygen atoms found in lead dioxide. Its structure helps explain the compound’s electronic and electrochemical behavior.
Lead–acid battery charging: The process that drives lead–acid battery reactions in reverse using an external electrical source. Charging regenerates lead dioxide from lead(II) sulfate at the positive plate.
Oxygen: A chemical element with symbol O that forms oxides with most elements. Oxygen combines with lead in the dioxide’s PbO₂ composition.
Lead–acid battery recycling: The recovery and processing of lead, plastic, and electrolyte from spent lead–acid batteries. Recycling recovers lead dioxide-derived material but can release toxic lead if poorly controlled.
Oxidation state: A formal accounting of electron distribution in a chemical species. Lead’s formal +4 state is central to describing PbO₂’s redox chemistry.
Electrochemical oxidation: Oxidation driven by an electrode through transfer of electrons to an external circuit. Lead dioxide electrodes can mediate oxidations in aqueous electrochemical processes.

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Lead(II,IV) oxideBroader topic: Reduction of Pb₃O₄ can produce PbO₂ under suitable conditions.