Battery Fires
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!
However, in rare cases, lithium batteries can catch fire – often in dramatic ways.
| Year | Device | Battery Maker | Number of Devices Recalled | Number of Reported Incidents |
|---|---|---|---|---|
| Oct. 2000 | Dell Notebook | Sanyo | 27,000 | 1 |
| May 2001 | Dell Notebook | N/A | 284,000 | 1 |
| Sept. 2002 | EV Global Motors Electric Bicycle | N/A | 2,000 | 5 |
| Oct. 2004 | Kyocera Cell-phone | Counterfeit | 1,000,0000 | 14 |
| March 2005 | Apple Notebook | LG Chem | 128,000 | 4 |
| June 2005 | Belkin GPS | N/A | 10,300 | 15 |
| August 2005 | Nikon Digital Camera | N/A | 710,000 | 4 |
| April 2006 | Disney (Memcorp) Portable DVD Player | McNair Technology / Unitech Battery | 102,000 | 17 |
| August 2006 | Dell Notebook | Sony | 4,100,000 | 6 |
Source: Values in the table are taken from NY times article – “Dell Will Recall Batteries in PC’s”, Aug 2006. Further details can be obtained at Consumer Product Safety Commission website.
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 elucidate general principles behind lithium battery fires.
Things to Consider Following A Battery Fire
Undoubtedly, product liability is a major concern; however, if you are considering a recall you need to answer the following questions:
- Cause of the fire – was the battery failure caused by user’s abusive actions or was it an unprovoked failure?
- Do the defective batteries belong to a particular manufacturing batch?
- Is there a particular dominant failure mechanism that is initiating the battery fires?
- What are the likely consequences and severity of the battery fire?
- What kind of statistical confidence can be assigned to future failures?
Here are a couple of battery failure modes that may lead to high temperatures and may result in a battery fire.
- Manufacturing defect: Manufacturing defects can result in a “hole” in the separating membrane leading to a short-circuit. Metal particle impurities in the polymer matrix can also contribute to excessive heat generation. A good quality control (QC) program at the battery manufacturing plant will ensure absence of defects. A quality check on the separator technology is critical for preventing leaks and therefore, techniques used to verify the consistency of the electrolyte separator are critical to prevent a short-circuit.
- Progressive wear: As a result of charging-discharging, a lithium battery can form dendrites. Dendrites are finger-like protrusions formed by accumulation of lithium metal. Over a period of time these dendrites can grow to touch the other electrode resulting in a short-circuit, heat generation, and a fire. More commonly in lithium batteries is formation of small dendrites leading to localized hot-spots and a reduction in cycling efficiency of the battery but not a fire.
