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Lead-acid batteries are a widely used type of rechargeable battery with a long history, first invented by French physicist Gaston Planté in 1859. They are widely used in applications such as automotive starting, power systems, emergency lighting, and portable devices due to their low cost, high reliability, and mature technology.
The working principle of lead-acid batteries is based on the electrochemical reaction between lead and lead dioxide. The battery consists of two main electrodes: the positive electrode (anode) is lead dioxide (PbO₂), and the negative electrode (cathode) is sponge lead (Pb). These two electrodes are immersed in a sulfuric acid solution, which acts as an electrolyte and participates in the reaction.
During discharge (i.e., when the battery outputs electrical energy), the lead dioxide at the positive electrode reacts with the sulfuric acid in the electrolyte to form lead sulfate (PbSO₄) and water, releasing electrons in the process; the sponge lead at the negative electrode also reacts with the sulfuric acid in the electrolyte to form lead sulfate, consuming electrons.
During charging (i.e., when electrical energy is stored in the battery), an external power source reverses the discharge process, causing the lead sulfate to decompose into lead dioxide and sponge lead, and the sulfuric acid concentration is restored.
The components of lead-acid batteries include:
1. Electrode materials: Positive electrode: lead dioxide (PbO₂). Negative electrode: sponge lead (Pb).
2. Electrolyte: sulfuric acid solution (H₂SO₄).
3. Separator: typically made of acid-resistant materials, such as polypropylene or glass fiber.
4. Casing: typically made of robust plastics, such as polypropylene.
The advantages of lead-acid batteries include low cost, simple maintenance, moderate energy density, and high recyclability. Disadvantages include large weight, large volume, capacity affected by temperature, and limited charge-discharge cycle life.
