Lithium-ion (Li-ion) Battery Safety

While lithium-ion battery technology has some attractive attributes, it is not without its problems. The liquid electrolyte used in today's Li-ion batteries is extremely flammable. Combine this unfortunate characteristic with the production of carbon dioxide gas when overcharged, and venting of flammable electrolyte can result. One manufacturer of notebook computers actually delayed delivery of a new model because the Li-ion batteries used in their systems sparked and caught fire in the lab just prior to shipment.
Overcharging of Li-ion cells must be avoided at all cost. Not only is the safety concern present, but Li-ion batteries are damaged by any degree of overcharge. Overcharging a Li-ion cell by as little as 1% can degrade its cycle life. Conversely, undercharging a Li-ion cell by the same amount doesn't take advantage of the full storage capacity of the cell.

It is essential that Li-ion batteries are only charged using a battery charger specifically built for the purpose.