Amidst all the Samsung Note 7 recall news last week due to continuing battery issues, a Kim Komando Show listener asked how to tell if a smartphone battery may explode and how to prevent such an event from happening. The listener also mentioned that she heard Dr. Oz mention that the iPhone 7 battery also explodes.
First, virtually all smartphones, laptops and portable rechargeable gadgets still use current lithium-ion technology for their batteries. This includes smartphones such as the discontinued exploding Note 7 and the iPhone 7.
Lithium-ion batteries are typically reliable. With millions and millions of lithium-ion batteries out there, the reports of explosions are still relatively minuscule. Out of the more than a million Note 7's out in the world, only a little over 100 units caught fire or exploded.
The iPhone explosions are even less frequent, and unlike the Note 7 cases where the phones spontaneously combusted, the iPhone reports were mostly caused by customer errors such as mishandling or structural compromises.
Even then, lithium-ion batteries pack so much energy in such small spaces that we are literally carrying mini-bombs in our pockets or purses each time we handle our gadgets.
How does a lithium-ion battery work?
A rechargeable lithium-ion battery consists of three main elements: a positively charged cathode on one side, a negatively charged anode on the other, and liquid electrolyte in between.
During charging, the lithium ions flow from one side to another, using the liquid electrolyte as the conduit. When a gadget is used and the battery discharges, the ions move in the opposite direction, generating the energy that powers the device.
With this energy exchange, it is crucial that the charged anode and cathode elements never come in contact with each other. If they do, energy is redirected to the liquid electrolyte instead, which may start a heat reaction and even a fire.
To prevent this from happening, battery manufacturers keep the anode and cathode apart by installing separators within the lithium-ion battery. The integrity of these separators is crucial to the safety of the battery because defects and breaches in these separators may cause explosions.
With that said, it is speculated that the battery issue that caused problems in the first batch of Samsung Note 7's are faulty separators in the lithium-ion battery causing the anode and the cathode to come in contact.
Also, although we can't verify what Dr. Oz said, the reported iPhone explosions may have been caused by structural damage to batteries' separators due to mishandling in shipping or by inadvertent bending rather than self-combustion.
Another cause of battery explosions is overcharging. Overcharging a lithium-ion battery, especially with a charger that's higher than the recommended voltage, can result in an excessive buildup of metallic lithium on the anode also known as "plating."
When plating happens, the metallic buildup of lithium can cause short circuits in the battery.
Worse, the cathode can become unstable and will start producing CO2 instead. This causes pressure to build up inside the battery and if left unchecked, the separators and the safety membrane will rupture, causing a fire and an explosion.
Thankfully, modern lithium-ion batteries have self-checking protection mechanisms that prevent overcharging.
Larger and faster-charging batteries
The Galaxy Note 7 also featured a new "fast charging" USB-C technology. Samsung touted the Note 7's battery as bigger with faster charging times than iPhone 7 but could these claims have caused the phone's battery problems down the road?
First, the larger 3,500 mAh battery of the Note 7 is already pushing the lithium-ion battery to its limits. (In comparison, the iPhone 7 Plus has a 2,900 mAh battery.) This larger battery means a higher voltage, more heat generation and a larger surface area for the battery's components.
Secondly, fast charging via USB-C is still an unproven technology and it may have supplied a larger voltage than what the Note 7's battery can handle. Similar to overcharging, charging too quickly with a voltage higher than the battery itself can also cause plating.
Too much and too fast, pressure and heat build up, damaging the separators, eventually leading to anode/cathode contact, a flame-out, and finally, an explosion.
This heat produced by a larger battery and quick charging can also cause a process called "thermal runaway." With this condition, if the cathode gets hot enough, it will start a cycle of reactions that will produce even more heat, which could lead to, yes you guessed it, an explosion.
Although Samsung has not really acknowledged the cause of the Note 7's battery issues, these factors could have played a big part in aggravating the problems.
Tips to prevent a lithium-ion battery from exploding:
- As much as possible, don't bend, puncture or stress your smartphone. Dropping a gadget hard enough can also cause the battery to explode. Check out how this cyclist fell and the impact caused his iPhone to explode.
- Don't use third-party chargers. Only use official and manufacturer-approved chargers. As mentioned earlier, using non-approved chargers can lead to plating due to mismatched voltages.
- Don't charge in hot environments nor leave your phone in a hot car or under the sun. Aside from the "thermal runaway" process, exposing your phone to extreme heat can diminish its capacity. Also, if your phone is getting too hot while charging, immediately disconnect. Here are our tips on how to make lithium-ion batteries last longer.
- Don't leave your phone charging unattended. Here's another no-no. Please be mindful of your charging, especially at night. Do not charge your phone in your bed nor put it under a pillow.
The positive takeaway from this Samsung Note 7 exploding battery fiasco is that gadget manufacturers will now rethink and will surely be extra careful about how they are pushing lithium-ion batteries and technology. Maybe that extra power is not worth exchanging for consumer safety.