Data obtained via a Freedom of Information (FOI) request revealed that in 2019 the London Fire Brigade dealt with just 54 electric vehicle fires compared to 1,898 petrol and diesel fires.
Despite the evidence, early electric vehicles were considered dangerously at risk from fire, including lithium powered forklifts.
Lithium battery cells have an anode and cathode the same as a lead acid battery, there is also an electrolyte, although in lithium batteries it is non-hydrous (i.e. free from water) and salt based.
The difference between the lead acid and lithium cells is the compound / elements are on the plates, with the lead batteries having lead based cells.
Lithium batteries have several different versions depending on use, for traction batteries there are 2 main types;
LFP “LiFEPO4” – Lithium iron phosphate
NMC – Nickel manganese cobalt.
The plates are made of thin copper strips which are coated, the anodes are coated in graphite and the cathode, depending on the type covered in the active material, which in a LFP cell is iron phosphate.
The lithium ions are stored within the cell structure of the graphite anode when fully charged and on discharge the lithium ion’s transfer to the cathode, recharging then pushes the lithium ions back to the anode.
Manganese, as school children around the world know, certainly burns. This is the real difference between LFP and NMC cells, LFP have a slightly lower storage density / capacity but they do not catch fire.
Tesla cars were all NMC cells, however the cars now being built in the Giga Factory in Shanghai are now using LFP.
What about thermal runaway?
Thermal runaway occurs in a battery when a failure causes the cell, or area within the cell, to elevate in temperature. Again the LFP battery type’s stability makes it extremely unlikely to suffer from thermal runaway. Even when punctured through the cell, the LFP battery does not catch fire and burn. It may smoke, but is unlikely to cause any catastrophic even.