E-cigarettes, smartphones… More and more accidents are now linked to the use of lithium-ion batteries! In late summer 2016, dozens of cases of Samsung's Galaxy Note 7 overheating and even exploding caused dismay and instinct with suspicion. This problem is frequently found with e-cigarette batteries that degass or even explode following improper handling. But then, should we be concerned about the safety of lithium-ion batteries?
Laptops, e-cigarettes, electric cars and even ... planes that catch fire: the list is cause for concern. Knowing that the same component is singled out: the so-called “lithium-ion” battery, present in all the implicated devices. Marketed in 1991, these batteries are now ubiquitous in the objects of our daily life, from computers to cell phones and tablets.
« This technology marked a revolution in the world of portable electronics, analysis Renaud Bouchet, professor of electrochemistry at the Grenoble Polytechnic Institute.If you wanted to store the same amount of energy with a nickel-metal hydride battery, for example, it would have to be two to three times heavier and bulkier!« Logic, therefore, that the manufacturers have relied on it to develop most of our portable devices.
Especially since the operation of a lithium-ion battery is very simple, much more than that of a lead-acid battery, for example. It is based on three elements: a positive electrode (cathode), another negative (anode), and an electronic liquid layer between the two (electrolyte). During the discharge, lithium ions present in the anode migrate towards the cathode, which causes the anode to release electrons and, therefore, delivers an electric current. When charging, it is the opposite: when a current is supplied to the battery, the anode regains electrons, which attracts the lithium ions from the cathode to it.
Today it is difficult to imagine such practical and efficient e-cigarettes without the use of these lithium-ion batteries.
A TECHNOLOGY THAT HAS NO REAL DANGER!
So where do the problems come from? « This technology presents no real danger to safety, and its chemistry is well controlled , assures Jean-Marie Tarascon, specialist in solid-state chemistry France secondary school. The overheating of such a battery can have only two origins: either its shape prevents the evacuation of heat during charging; or the two electrodes are in contact, which creates a short circuit and causes thermal runaway.«
The electrolyte, which serves to insulate the two electrodes, being in fact most of the time highly flammable, it must be kept away from any excessive heat. Otherwise, one of the warning signs of overheating may be the swelling of the battery: it is better to avoid using it ...
At present, however, any company is able to design a safe battery by following two simple principles: take into account heating during charging and incorporate a sufficiently thick separator (plastic material that coats the electrolyte) to prevent contact between the electrodes.
SEVERAL DECADES OF WAITING FOR MORE SECURITY?
However, in their race for performance, some manufacturers make the choice to cut corners on safety. Indeed, « For the moment, the only way to improve the autonomy of a battery is to increase the thickness of the electrodes, while reducing that of the separator, in order to keep a constant volume« , attests Renaud Bouchet. And that poses several problems.
First, by reducing the thickness of the separator - sometimes by half! -, manufacturers increase the probability of a fault at the heart of it. In some cases, this can lead to contact between the electrodes, and therefore to a short circuit. Another problem: during charging, anomalies can form at the anode. Lithium ions do not fit properly into the negative electrode and form small metal deposits, called dendrites. Which can also be at the origin of a short circuit, by creating kinds of conductive bridges between the two electrodes. Hence the usefulness, once again, of a fairly thick separator.
What is more, the appearance of these famous dendrites turns out to be more frequent when the intensity of the current is increased during charging, which becomes necessary with thicker electrodes. Ditto when manufacturers try to reduce the charging time: the only way to achieve this is to increase a little more the intensity of the electric current delivered during the charge, and therefore to increase the risk of short-circuit caused by the formation of dendrites.
In short, companies are pushing lithium-ion technology to its limits, which leads to accidents. Can we still hope to have more powerful batteries without them exploding in our face? Despite the manufacturers' assurance, only the advent of new chemicals will guarantee this. Which could take decades.
Regarding the e-cigarette, in 99% of battery explosions, it is not the model that is responsible but the user, the accident often results from negligence in handling lithium-ion batteries.
In order to avoid any problem with this kind of batteries certain safety rules must be respected for safe use :
- Do not use a mechanical mod if you do not have the necessary knowledge. These cannot be used with just any battery ...
- Never put one or more batteries in your pockets (presence of keys, parts that can short-circuit)
- Always store or transport your batteries in boxes keeping them separate from each other
If you have a doubt, or if you are not familiar with it, consider inquiring before buying, using or storing batteries. here is a complete tutorial dedicated to Li-Ion batteries which will help you to see more clearly.
Source : Science-et-vie.com