By Edwin Thomas | Updated Aug 30, 2022
A battery is an electrochemical device that generates electricity through controlled chemical reactions between an anode, a cathode, and an electrolyte. In all common types—including lead‑acid and lithium‑ion—the anode is the positive terminal, and the cathode is the negative terminal. The electrolyte facilitates ion transport; without it, the electrodes would short‑circuit.
Lead‑acid batteries use lead plates and lead dioxide for the anode and cathode, respectively, bridged by a dilute sulfuric‑acid electrolyte (~33 % H₂SO₄). During discharge, the electrodes are gradually converted to lead sulfate; recharging reverses this conversion, restoring the original composition.
Lithium‑ion cells employ a graphite anode and a cathode made from materials such as lithium cobalt oxide, lithium iron phosphate, or lithium manganese oxide. The electrolyte is a lithium‑salt solution in an organic solvent. Recharging reverses the lithium migration that occurs during discharge.
Lead‑acid batteries are one of the oldest rechargeable designs, originating in the mid‑19th century. They have a low energy‑to‑weight ratio, resulting in large, heavy packs for the power they deliver. However, their high surge‑to‑weight ratio makes them ideal for applications that require a sudden burst of power—such as automotive starters. Production costs are low, but they require long recharge times and are not well suited to steady, low‑power loads.
Compared with lead‑acid, lithium‑ion batteries offer a superior power‑to‑weight and power‑to‑volume ratio, enabling the slim, long‑lasting devices we rely on today. Some chemistries can also provide high surge capability. The trade‑offs are higher manufacturing costs and a gradual loss of capacity over time, even when the battery is idle. A typical lead‑acid pack can maintain performance for several years, whereas most consumer lithium‑ion batteries noticeably degrade after one to two years.
Choosing between lead‑acid and lithium‑ion depends on the application: heavy‑weight starters benefit from lead‑acid’s surge performance and low cost, while portable electronics demand the lightness and longevity of lithium‑ion. Understanding the underlying chemistry helps you match the right battery to your needs.
