What is the main difference between a lead-acid battery and a lithium-ion battery?

The primary distinction between lead-acid batteries and lithium-ion batteries lies in their energy density, which refers to the amount of energy stored per unit volume or weight. Lead-acid batteries typically have a lower energy density compared to lithium-ion batteries, meaning that for the same size and weight, a lithium-ion battery can store significantly more energy. This results in lithium-ion batteries being more efficient in applications requiring compact energy storage, such as in electric vehicles and portable electronics.

Higher energy density in lithium-ion batteries allows them to provide more power while being lighter and more compact than lead-acid batteries, making them the preferred choice in many modern applications. This fundamental characteristic underlines why the distinction referenced in the answer is crucial in understanding the advantages and limitations of each battery type.