Which type of battery is most prone to combustion when overcharged or overheated?

Lithium-ion (Li-Ion) batteries are indeed known for their vulnerability to combustion when subjected to overcharging or overheating. This occurs due to the chemical reactions occurring within the battery. When a Li-Ion battery is overcharged, it can lead to thermal runaway, a phenomenon where the temperature of the battery increases uncontrollably due to exothermic reactions. This rise in temperature can cause the electrolyte to break down and can ignite the flammable organic solvents present in the battery, resulting in combustion or even explosions.

The design of Li-Ion batteries, which typically includes a separator and a liquid electrolyte, contributes to this risk. High temperatures can cause the separator to fail, allowing internal components to short-circuit, potentially leading to fire. As a result, proper charging protocols and thermal management are crucial for the safe use of Li-Ion technology in various applications.

In contrast, other battery types listed, such as lead-acid, nickel-cadmium, and nickel-metal hydride, have different chemical properties and constructions that generally make them less prone to catastrophic combustion under similar conditions. Thus, the correct answer highlights the specific risks associated with lithium-ion battery technology.