Why Do Lithium-Ion Batteries Explode?

“Many of these lithium-ion batteries are now bursting into flames”.

Sounds scary, right? According to that CBS report from last year: the batteries found in e-cigarettes and electric hoverboards are catching on fire. If you’re not aware, those batteries are lithium-ion – the very same ones used in power banks. Thankfully portable chargers house multiple protections to protect against this and more. Join us as we explore why batteries catch on fire or explode and the protections employed to prevent this.
 

How Do Lithium-ion Batteries Work?

Lithium-ion batteries are actually made up of multiple cells with each cell consisting of a few different parts. The outer most layer is made of conductive surfaces like aluminum and copper. Sandwiched between these two are positive and negative electrodes called the cathode and anode, respectively. Between them is an electrolyte layer, which allows the charge to flow freely between the two electrodes. In the middle of all of this is a glass separator that helps to prevent short-circuiting by keeping the electrolyte layers apart from each other. All these parts work together when the battery is discharging or charging. When the battery is discharging, the lithium-ions go from the anode via the electrolyte to the cathode. The opposite is true when recharging.

How charging and discharging work. Photo courtesy of www.redmag.com

How Do Lithium-ion Batteries Become Damaged?

Lithium-ion batteries can be damaged which can lead to battery problems or even a fire. Here is how:

• Shipping damage: Sometimes shipping the product can result in damage. This may involve frequent shaking, a loosened or damaged USB interface, or IC chip harm.
• Bad welding: The tab that is welded between battery terminals is too thin or poorly welded resulting in a compromised electrical connection. This can also lead to short-circuiting.
• High temperatures: Despite temperature protections, lithium-ion batteries can still be subject to short-circuiting or even melting from extremely high temperatures.
• Contaminated electrodes: As they are made from different substances and feature a different charge, a contaminated cathode or anode will pierce the separator resulting in short-circuiting. To avoid this, each electrode is processed in a different room.

In these situations, the immense amount of energy stored in the battery cannot be used in a correct and safe manner. Instead, the heat from this energy builds up and up. This process is known as thermal runaway.

What Exactly Is Thermal Runaway?

When the battery is charging it builds up heat and pressure. This is typically at a level that the battery can handle. However, in situations such as over-charging, the build-up is too strong and without a place to release it, the electrolyte (which itself is a flammable solvent) begins to burn. This can then lead to an explosion. To prevent this, quality lithium-ion batteries include a protection that disconnects the battery before this happens.

Which Protections Do Power Banks Have?

Lithium-ion batteries found in power banks contain protections to guard against thermal runaway. Other safeguards ensure the battery continues to work and has a long life span. The number of protections found in power banks depends on who produced it. A RAVPower power bank typically features these common protections:

• Over Current Protection: Stops the power bank from delivering a current that exceeds the amplitude of the connected device. Safety mechanisms like circuit breakers, over current relays, and fuses provide instantaneous protection.
• Over Charge Protection: Prevents the power bank from continuing to charge a device that is outside the protection range (3.00 V to 4.20 V). This will avoid thermal runaway.
• Short Circuit Protection: This is another type of over current protection. In this situation, the protection ensures that there is always a direct path for the current to travel. This prevents the cell from overheating which can cause a fire.
• Over Discharge Protection: Stops the discharge rate from falling below 2.7 V/cell to 3.00 V/cell. This reduces battery cell stress and allows some extra power to self-discharge down to 2.50 V/cell. When that happens, the lithium-ion battery will “sleep” to protect against itself.
• High Temperature Protection: Prevents the power bank from charging or discharging when battery temperature exceeds 60°/140F*.

*This may change depending on the size of the battery

A full list of RAVPower power bank protections

How Do You Choose a Safe Li-Ion Battery?

Choosing as safe lithium-ion battery can be tricky, as the average consumer does not know the manufacturing processes behind the battery they are buying. The number one advice would be to buy through trusted brands. This means buying recognized brands that you know are reliable. With hundreds of different types of products using lithium-ion batteries, we cannot possibly recommend you a brand for each industry. However, when it comes to power banks and charging, we know one brand whose products are always reliable.

Another solution is to look for products that contains additional safeguards. This will not only protect the battery from damage, but will ensure you get a long product lifespan.

While battery protections serve multiple functions, they mainly do it protect you from the very slim chance of an accident from a damaged battery. Thankfully quality control standards are always improving. Even better, scientists are currently researching new types of batteries that last longer and are even safer. There’s even word of a battery in development that won’t ever explode. Sign us up!

For RAVPower’s selection of power banks, please click here
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Remember to let us know in the comments below if you have ever had a battery problem.