Rechargeable batteries are great for storing energy and powering electronics from smartphones to electric vehicles. In cold environments, however, they can be more difficult to charge and may even catch on fire.
I’m a mechanical engineering professor who’s been interested in batteries since college. I now lead a battery research group at Drexel University.
In just this past decade, I have watched the price of lithium-ion batteries drop as the production market has grown much larger. Future projections predict the market could reach thousands of GWh per year by 2030, a significant increase.
But, lithium-ion batteries aren’t perfect – this rise comes with risks, such as their tendency to slow down during cold weather and even catch on fire.
Behind the Li-ion battery
The electrochemical energy storage within batteries works by storing electricity in the form of ions. Ions are atoms that have a nonzero charge because they have either too many or not enough electrons.
When you plug in your electric car or phone, the electricity provided by the outlet drives these ions from the battery’s positive electrode into its negative electrode. The electrodes are solid materials in a battery that can store ions, and all batteries have both a positive and a negative electrode.
Electrons pass through the battery as electricity. With each electron that passes to one electrode, a lithium ion also passes into the same electrode. This ensures the balance of charges in the battery. As you drive your car, the stored ions in the negative electrode move back to the positive electrode, and the resulting flow of electricity powers the motor.
When a lithium-ion battery delivers energy to a device, lithium ions – atoms that carry an electrical charge – move from the negative electrode, the anode, to the positive electrode, the cathode. The ions move in reverse when recharging.
Argonne National Laboratory, CC BY-NC-SA
While AA or AAA batteries can power small electronics, they can be used only once and cannot be charged. Rechargeable Li-ion batteries can operate for thousands of cycles of full charge and discharge. For each cycle, they can also store a much higher amount of charge than an AA or AAA battery.
Since lithium is the lightest metal, it has a high specific capacity, meaning it can store a huge amount of charge per weight. This is why lithium-ion batteries are useful not just for portable electronics but for powering modes of transportation with limited weight or volume, such as electric cars.
Battery fires
However, lithium-ion batteries have risks that AA or AAA batteries don’t. For one, they’re more likely to catch on fire. For example, the number of electric bike battery fires reported in New York City has increased from 30 to nearly 300 in the past five years.
Lots of different issues can cause a battery fire. Poorly manufactured cells could contain defects, such as trace…