Information Source: Battery University
Safety is a sensitive issue that gets much media and legal attention, especially with Li-ion batteries. Any energy storage device carries a risk, and in the 1800s steam engines exploded and people got hurt.
Lithium-ion has a high specific energy and even though safe, high usage by millions of consumers is bound to generate failures. In 2006, a one-in-200,000 breakdown triggered a recall of almost six million lithium-ion packs. Heat-related battery failures are taken very seriously, and manufacturers choose a conservative approach.
Li-ion using conventional metal oxides is nearing its theoretical limit on specific energy. Rather than optimizing runtime, battery makers are improving manufacturing methods to enhance safety and increase the calendar life. The real problem lies in rare occasions when an electrical short develops inside the cell. In such a case, the external protection peripherals are ineffective to stop the thermal runaway, once in progress.
A mild short will only cause elevated self-discharge and the heat buildup is minimal because the discharging power is very low. If, however, enough microscopic metallic particles converge on one spot, a sizable current begins to flow between the electrodes of the cell, and the spot heats up. Heat is always an enemy of the battery. When fully charged, elevated temperature causes a harmful reaction between the positive and negative electrodes and the electrolyte.
This thermal runaway that occurs is known as "venting with flame". The preferred term by the battery industry is "Rapid disassembly".
So what do you do with a device in Thermal Runaway? We are glad that you asked because this actually applies to ANY device (not just electronic cigarette batteries) that contains a Li-ion battery.
- Immediately remove the device from proximity to flammable materials and bring it to a non-combustible surface
- If at all possible, put a disintegrating device outdoors and let it burn out
- If this occurs in an airplane, FAA tells flight attendants not to use fire extinguishers but specify water or pop (soda)
- Water cools the adjacent material and prevents the fire from spreading. Many research laboratories and factories also use water to put out battery fires.
- Allow good ventilation while the battery burns itself out
Summary: Now that you have had your safety briefing, let us assure you that the lithium-ion Electronic Cigarette batteries are as safe as any other lithium-ion power device and that heat-related failures are rare.