The Li-ion batteries are safe for operation but with a huge number of products in the market, the failures can’t be avoided. Battery makers point out that there are some rare occasions the microscopic metal particles may come into contact with the other parts of the battery and this contact can lead to a short circuit. Battery manufacturers tend to avoid these small particles from the batteries.
Battery manufacturers may compromise on the cleanliness aspect of the manufacturing zone that may result in impurities making its way to the workforce going unnoticed. This ultimately results in a failure.
The lithium-ion batteries if used as intended are safe. Incorrect uses involve excessive vibration, elevated heat and charging below freezing. Heat combined with a full charge is very stressful for the Li-ion battery. The failure rate though is very less for the lithium-ion batteries. The chances of you being struck by lightning are 1 in 13000 and the chances of your battery failing are 1 in 10 million.
If the battery overheats, hisses, bulges, immediately move the device away from flammable materials and place it on a non-combustible surface. If at all possible, remove the battery and put it outdoors to burn out. Small fires can be extinguished using a foam extinguisher, CO2, ABC dry chemical, powdered graphite, copper powder or soda. Water-based products are readily available and are most commonly used to extinguish the fire. Water cools the area and prevents the fire from spreading.
But when we have a large Li-ion fire, water will not be of any help. Lithium batteries have plenty of lithium metal that reacts with water and exacerbates the situation. Water with copper material can be used but it is not available easily and not economical in use. Class D fire extinguishers must be used when dealing with Li-ion fires.
When the fire starts spreading the heat of the failing cell inside the battery pack the fire propagates to the next cell causing them to become thermally unstable. This gives rise to a chain reaction and each cell disintegrates in its own given time. This can result in the pack being destroyed in several seconds or over a time span of several hours.
The gas that is released from the venting Li-ion cell is CO2. Other gasses that are released are through a vapourised electrolyte. The reason for same can be faulty separators by aging, rough handling, excessive vibration etc.
Source: Battery University
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