Hydrofluoric acid: the chemical hazard hiding in electric and hybrid vehicle batteries


Ever wondered what types of batteries are used to power electric and hybrid vehicles (EHVs)? Well, the majority of EHVs being driven on our roads today will use lithium-ion (Li-ion) or lithium polymer batteries.


These batteries offer high energy density in comparison to the relative weight, they can store several hours of electricity and they can be quickly and easily recharged. They also pose a potentially lethal chemical hazard to anyone working on or near EHVs.


How to lithium-ion batteries work?

To understand the hazards that lithium-ion batteries present, we must first understand what they’re made of and how they actually function.


Lithium-ion batteries work by delivering a chemically reversible lithium ion exchange reaction between two electrodes. The negative electrode is often made of graphite and the positive electrode of cobalt dioxide or manganese dioxide. When these two electrodes are immersed in a liquid electrolyte (usually a solution of lithium hexafluorophosphate salts in a mixture of ethylene carbonate and propylene carbonate or tetrahydrofurane) a reaction occurs and the battery releases energy in the form of electricity.


Since the electrolyte is a liquid, there is always the possibility that it could leak from inside the battery – we’ve all seen standard AA batteries that have leaked leaving white potassium hydroxide crystals on their outer casing, right? Well, that’s the danger with lithium-ion batteries. If the electrolyte inside them does leak and comes into contact with moisture in the air or water, a chemical reaction happens and hydrofluoric acid is produced.


Electrolyte leakage isn’t just the only potential hazard posed by lithium-ion batteries. When working with EHVs, there is also the risk that lithium-ion batteries could explode if they are degraded, misused or their internal temperature rises to over 75°C. If a lithium-ion battery combusts, it will produce hydrofluoric acid and hydrogen fluoride gas, an acute poison that can permanently damage our lungs and eyes.


What is hydrofluoric acid?

Hydrofluoric acid is a solution of hydrogen fluoride in water. A colourless liquid, hydrofluoric acid is highly corrosive – it can dissolve glass! – and is extremely toxic. If it comes into contact with our skin or eyes, it can cause severe chemical burns that are very painful and slow to heal. If left untreated, it is absorbed into the body’s tissues and bones causing their destruction. It interferes with our body’s calcium metabolism and contact with concentrated hydrofluoric acid can result in systemic toxicity, cardiac arrest and even death.


Perhaps the most disquieting and sinister property of hydrofluoric acid is the delayed serious tissue damage it can cause. If your skins is exposed to just one tiny drop of low concentration of hydrofluoric acid, it may not produce any immediate pain or burning sensation. It may take several hours for any pain to materialise at which point irreparable damage could have been done. For this very reason, any exposure to hydrofluoric acid, however small, must be considered significant and immediate first aid must be administered.


How to treat hydrofluoric acid burns with first aid

In the first instance, the affected area should be flushed with water for one minute and a hydrofluoric acid antidote gel instantly applied until pain ceases. This has been proven to be the most quick and effective first aid treatment for hydrofluoric acid burns.


Hydrofluoric acid antidote gels work by neutralising the acid. They contain calcium gluconate which does the job of mixing with the hydrofluoric acid to form calcium fluoride. This calcium fluoride then prevents the extraction of calcium from the body tissue and bones.


After first aid has been given, the patient must seek immediate professional medical advice.


Prosol UK products (follow link for more information):

First Aid Kit for Lithium Battery Acid Skin Contact (FAA8660)

First Aid Kit for Burns including H-F Gel (BFA8602)

Warning Battery Acid Sign (W18)