In recent weeks, there have been multiple cases about battery explosions. Especially with the Samsung Galaxy Note 7. The battery of the Note 7 owners had been exploding or catching fire. The problem was so severe that Samsung had to recall most of it’s Note 7 Smartphones back. Now Samsung has started giving replaced phones back to it’s customer. After all this mess that Samsung Note created, lot of other similar cases also came to surface like iPhone explosion, Mobile phone catching fire. Yantragyan will now put all your queries regarding Smartphone batteries to end. We will now explain to you as detailed and simple possible. Everything about smartphone batteries and what causes explosion in them.
Explanation Of the Explosion in Battery of Samsung Note 7
The explosion in the batteries is caused due to short circuiting. When Anode and cathode of the battery come in very close contact with each other. The result is heating which further act as the catalyst, causing further heating. Thus finally this over heating results in battery catching fire or exploding.
Further Explanation –
We have tried to explain in detail the whole process of mobile battery and what causes heating. You see the batteries which are being used these days in most of the devices like smartphones,laptop, etc. These batteries are based on Lithium(Li)Ion technology. Lithium is the metal suitable for the making batteries due to it’s highly reactive nature. High energy and power densities, along with smaller size of lithium-ion batteries compared to other like nickel type, is the reason for popularity of lithium type batteries.
But these features of lithium batteries are also the reason for some of the problems associated with it. Lithium type batteries have high thermal instability. A particular concern in this context is a scenario called thermal runaway in which one or more exothermic (heat releasing) side-reactions occur. Leading to elevated temperature ranges that in turn lead to an uncontrollable and excessive release of heat.
To understand that we first have to know about basic functioning of the Lithium type batteries. The three main basic components in it are electrodes, electrolyte and the separator. Current rechargeable Lithium batteries based on electrodes in which their is ion insertion/extraction through electrolyte.
The process can be explained as the transfer of charge that occurs between the interface of a batteries electrode and electrolyte solution. There is process of reduction (gain of charge) and oxidation (loss of charge) of the species going on.
Above basic diagram explains the internal process going on when we are using our device normally(Discharge mode) and When we charge our phone. We can see from the above figure two Electrodes , Anode and Cathode. These electrodes are separated from each other via a separator which is Lithium in this case. The two electrodes are placed in electrolyte solution.
When the battery is charged or discharged, these redox reactions change the molecular or crystalline structure of the electrode material. Therefore batteries become less and less usable after each charge/discharge cycle. This is why we need new batteries for our device ever once in a while.
Now coming to more detailed Lithium battery layout as shown in figure below. Here Graphite is used as Anode Electrode and Cathode is ‘Aluminum-doped lithium nickel cobalt oxide ‘. Yes, it is the full name of cathode.
We will not go into further detail by explaining the reactions, as this will another whole post. The basic conclusion can be listed like this ” the electro-chemical reaction between the electrodes and electrolyte produces charge, this charge is utilized by your device to operate.”
What causes Excessive heat in battery which finally leads to fire hazards ?
There is scenario called thermal runaway in which one or more exothermic(heat releasing) side-reactions occur. Leading to elevated temperature ranges that in turn lead to an uncontrollable and excessive release of heat. You can correctly assume all the leading battery experts are constantly innovating to reduce this Thermal runaway problem.
Now there are certain factors which lead to excessive heat generation at first. These are electro-chemical reaction (between electrodes and electrolyte), internal resistance of the electrodes (more resistance equates to more heat, also depends on quality of material) , overcharging, mechanical abuse to the battery, short circuit, and high temperatures due to external factors can lead to critical failure of lithium-ion cells. These abuse conditions can initiate thermal runaway within a cell. Wherein a chain reaction of exothermic(heat releasing) side-reactions can cause a cell to reach temperatures of over 600°C.
In most common cases, these factors are high external temperatures of battery and overcharging. These days overcharging issue is mostly resolved because manufacturers usually have overcharging limiting circuits in the phone itself. But using third party low quality chargers increases the risk. High external temperature of batteries are usually due to excessive heat generated from processor of the device (example Snapdragon 810, mediatek etc). Battery, when placed very near to the processor or there not proper insulation between the two by the manufacturer.
That having been said, the problem in the Samsung battery is caused due to Short- circuiting. This is due to a manufacturing defect made while making the battery. The short circuit occurs between the two electrodes as they are placed very near to each other. The heat generated by other factors like electro-chemical reaction acts as catalyst to this short- circuit problem. Finally making battery explode or catch fire due to large amounts heat generated.
Now you know, how the whole battery works and what causes explosion in it. Other time someone asks you about mobile batteries you know what you have to say. You can simply share the article as well. Like us facebook for more tech updates
Image Sources: https://pubs.acs.org/cen/coverstory/87/8730cover2.html and citeseerx.ist.psu.edu