Safety first -- Why all lithium batteries are not the same

Widely used in consumer electronics, you'll find lithium-ion (Li-ion) batteries everywhere. From cell phones, to laptops, Li-ion batteries have one of the best energy-to-weight ratios, no memory effect, and a slow loss of charge when not in use. Li-ion batteries have two to three times the energy density of nickel-cadmium and nickel-metal hydride batteries, and four times the energy density of lead-acid batteries (higher energy density means lighter and more compact batteries). But are they safe?

The safety of Li-ion batteries has been in question since before 2001, when the U.S. Department of Transportation's Research and Special Programs Administration implemented increased safety checks, including puncture and crush tests, to ensure that the batteries could be safely transported. According to the results, 120,000 lithium-ion cells caught fire during the tests — strong evidence that the safety of the battery was in question.

Battery basics
All batteries produce energy from electrochemical reactions. Batteries are comprised of several components, but primarily consist of the following:

• A positive electrode and a negative electrode
• An ionic electrolyte: a solution that contains and aids the movement of ions (charged particles) back and forth between the two electrodes
• A porous separator (ensures the two electrodes do not touch but allows ions to travel back and forth between the electrodes)

When a lithium-ion battery is charged, lithium ions travel from the positive electrode to the negative electrode. On discharge, these ions return to the positive electrode releasing energy in the process.