2016 was an explosive year for Samsung as it was forced to recall its Samsung Galaxy Note 7 smartphones following repeated cases of models catching on fire. While the energy densities of batteries continues to increase, the question of safety remains a big issue.
So just why do some batteries combust? The lithium-ion technology which is used in batteries contains flammable liquids as the electrolyte, so when the battery overheats or short-circuits it can catch fire. For several decades people have been looking for a stable solid that could effectively replace these liquids, and researchers at Stanford University have implemented new technology in order to speed up this search.
The researchers took inspiration from facial recognition and machine learning technology. They have designed algorithms which can screen any of the 12,000+ known lithium-containing solids to see if it is suitable for an electrolyte application. Test criteria included stability, cost, abundance and the ability to conduct lithium ions and re-route electrons through the battery’s circuit.
21 promising materials were discovered and the researchers now plan to experiment on each one to determine which are best for real-world applications. The removal of trial and error methods drastically reduces the time required to reach a solution.
One material that has been successful is flame retardant triphenyl phosphate (TPP). The researchers have designed a lithium-ion battery in which TPP ‘sits’ inside a shell within the electrolyte fluid. When the temperature reaches 150°C, the shell melts and the chemical compound is released, extinguishing the fire. During tests, battery fires were recorded to be put out in 0.4 seconds.
Talking to the BBC, Ian Fogg, Senior Analyst at IHS commented: "Manufacturers have been balancing out consumer demand for longer-lived batteries, and more powerful devices with better graphics and larger more detailed displays, with the sophistication of battery tech. It's very difficult to push up the capacity of batteries and there is always a risk that a battery in any device could fail." The Stanford University research is a promising step in the right direction for long-lasting and safe batteries. Hopefully spontaneous combustion will remain confined to 2016.