Because of their dependability and long effective lifespan, lithium ion rechargeable batteries are used in almost all modern electronic gadgets – cell phones, laptops, digital cameras, power tools, video games, PDA, household devices, e-bikes, security lighting, iPods, and automobiles. As the electronic market grows, it is evident that the lithium battery market will grow exponentially!
In rare cases, lithium batteries can catch fire – often in dramatic ways.
Lithium battery fires are not a common place occurrence. Based on my survey, it appears roughly 1-10 lithium batteries per million battery population catch fire.
Why Does a Lithium Battery Burn?
A lithium battery consists of two lithium foils sandwiching a polymer electrolyte – usually a porous thin film enclosing a liquid or gelled electrolyte. The various types of lithium batteries vary in size and shape but are identical in construction and generally differ in cathode material and polymer solid electrolyte.
During normal usage, the lithium ions flow from the anode to the cathode (generally a mixed metal electrode) through a polymer matrix filled with electrolyte. The polymer electrolyte thickness is of the order of microns i.e. paper thin.
Although the exact failure mechanism will vary for individual cases, I’ll explain general principles behind lithium battery fires.
Anode and cathode materials of a battery can spontaneously react – it is this natural chemical potential that is exploited to make a battery work. In a battery, we control the spontaneous reaction by introducing a separating medium termed electrolyte.
If one were to remove the separating medium, anode-cathode materials can spontaneously react and generate a lot of heat. This excessive heat in turn can lead to (a) evaporation and possible ignition of the electrolyte; or (b) generation of flammable vapor due to side-reactions, decomposition products, or metal-catalyzed reactions. Thus the hydrocarbons from polymer electrolyte are serving as the “fuel”.