From your laptop and cell phone to your child’s favorite toys, lithium batteries have become a ubiquitous source of power for modern life. Unfortunately, these rechargeable batteries have some serious flaws that go beyond lifespan or the time it takes to recharge them. As recent episodes with the Samsung Note 7 phone (as well as the so-called hoverboards, e-cigarettes, and others) brought to light, lithium batteries, in the right circumstances, can combust.
Meanwhile, traveling with a laptop or other lithium battery in your checked bag allows for other risks. If these batteries are so volatile, how have they become the standard for portable power? When is it safe to ship them, and how do they get transported from manufacturers to retailers and consumers around the world?
How Lithium Ion Batteries Work
A lithium-ion battery contains a few very important parts: the anode; cathode; electrolyte; separator; and current collectors, positive and negative. The anode and cathode are what store the lithium, while the electrolyte carries positively charged lithium ions from the anode to the cathode and back, through the separator. The movement releases electrons in the anode, creating a charge in the positive charge collector. The current flows from the positive collector to the device to the negative collector. The separator blocks the flow of electrons in the battery, which will be important later.
The Department of Energy has an excellent visual representation of how the process works, from discharging and powering an item to recharging.
Li-ion batteries are, per pound, ones of the most energetic rechargeable batteries, making them highly desirable for consumer electronics. They are often stacked together, as in a Tesla car, meaning the “battery” is actually hundreds or thousands of smaller batteries, or “cells,” making up one large battery. Each battery has an energy density of up to 160 watt hours per kilogram, or about twice what an alkaline or nickel-cadmium rechargeable battery has. Under the right conditions, however, they can be volatile.
Why Lithium Batteries Explode
There’s two main causes for li-ion battery explosions. The first is heat. If the battery gets hot enough, such as inside a laptop without proper ventilation, the electrolyte could ignite. The second cause is a separator failure, causing a short. If the electrodes touch, the battery will quickly heat up. Recall that the batteries are highly energetic, which means they will get extremely hot — up to 1,000 degrees F — very quickly, causing the battery to vent the electrolyte. Introducing oxygen to the electrolyte can ignite or even explode the substance. Once it is on fire, it will spread to other cells, and, in a domino effect, all of the batteries will catch fire.
Explosions themselves are relatively rare. For the most part, the batteries will simply burn. Consumer Reports notes that for the Samsung Galaxy Note7, it was a manufacturer defect that caused the explosions, rather than the batteries themselves. With millions of Li-ion batteries in use, it’s unlikely the average consumer will come in contact with a defective — and thus explosive — battery.
Lithium Batteries on Airplanes: Risks and Regulations to Know
That does not mean there aren’t precautions on place for Li-ion batteries on planes. The Department of Transportation started changing guidelines in 2014, including batteries for transport, which we’ll touch on later.
For consumers, the DOT has a table showing what is permitted and what is forbidden on flights. In general, if the Li-ion batteries are installed in a device that has less than 160 watt-hours, it’s likely permitted. If not, it is forbidden. Spare batteries not installed cannot be in checked baggage. Lithium metal batteries with more than 2 grams of lithium — which are generally after-market — are forbidden entirely.
Larger batteries and batteries not installed in a device might not have enough protection from being jostled and thus compromising the separator.
Shipping Lithium Batteries
This brings us to shipping Li-ion batteries and the hoverboard debacle. The DOT found 32 cargo containers full of improperly packaged “hoverboards,” also called self-balancing boards. Many of the boards were recalled due to problems with the batteries.
If you intend on shipping Li-ion batteries by air, the International Air Transport Association provides a guidance document for transporting the batteries. IATA provides more information here. The batteries must pass UN 38.3 testing requirements in order to be transported.
You can find more requirements for shipping Li-ion batteries at the Cornell Law School. Generally, consumer-grade Li-ion batteries do not need to be shipped under Class 9, assuming they are under 100 watt-hour. Caution labeling is required.
Unlike consumers, manufacturers and retailers tend to ship by land and sea. The risks of pressurization and combustion are less of a concern, as altitude change is much less drastic, but there are still rules and guidelines for shipping batteries via freight. Generally, shipping by freight is thought to be the safer, easier option for transporting batteries.