One big problem with lithium-ion batteries is that they have the tendency to catch fire and blow up all kinds of gadgets like toys and phones. To solve that issue, a group of researchers from Stanford University created lithium-ion batteries with built-in fire extinguishers. They added a component called "triphenyl phosphate" to the plastic fibers of the part that keeps negative and positive electrodes separate. Triphenyl phosphate is a compound commonly used as a flame retardant for various electronics. If the battery's temperature reaches 150 degrees Celsius, the plastic fibers melt and release the chemical. Based on the researchers' tests, the method can stop batteries from burning up within 0.4 seconds.