Energy Density Key to the Next Generation of Li-Ion Batteries

Energy lights density abstract, horizontal, over black background

There has been enough discussion on lithium-ion batteries that most of us are familiar with them. We are fine with relying on them to power our cell phones and portable music players. But when it comes to powering our cars, we are a bit more skeptical. That’s why engineers are working on increasing energy density. It is the key to the next generation of lithium-ion batteries.

A 2018 research study published by the Proceedings of the National Academy of Sciences (PNAS) suggests that the combination of a lack of range and slow charging times are preventing widespread electric vehicle (EV) adoption. Simply put, the researchers say that people are afraid to buy EVs because of the risk of running out of power in the middle of a trip.

Such fears seem reasonable considering you can barely drive a mile or two without finding a gas station. So again, we are okay with lithium-ion batteries for household electronics and computers, but not for cars. That brings us back to the concept of energy density.

Energy Density vs. Power Density

There are two ways to measure battery energy. The first is energy density; the second is power density. Energy density is the amount of power a battery can store. However, according to battery maker Pale Blue Earth, batteries do not store electricity. They store potential energy by way of lithium ions.

Power density is a measurement of the amount of electricity a battery can generate as it discharges. When a battery is not being used, potential energy is stored in lithium ions located at the negative end. During discharge, those ions pass through an electrolyte on their way to the positive end, creating a chemical reaction that generates electricity. Power density measures that electricity.

The U.S. Department of Energy offers a clear illustration using a swimming pool. They compare energy density to the size of the pool, which is to say how much water it can hold. Power density is compared to how quickly that pool could be drained if necessary.

Energy Density and EVs

All of this can now be applied to the main issue with EVs: range. To begin with, we know that lithium-ion batteries have a higher energy density than disposable alkalines. That is one of the reasons people appreciate rechargeable li-ion batteries as much as they do. Higher energy density translates into more power with each charge, without increasing the size of the battery.

What holds true for your portable music player also holds true for electric cars. If you can increase the energy density of the batteries, you get more energy from each charge without adding size or weight. The researchers involved in the previously mentioned study believe that this one of the keys to encouraging widespread EV adoption. The Department of Energy agrees.

Increasing energy density means a longer range for EVs. It means more miles between charges. More importantly, a significant increase in energy density could actually allow manufacturers to make their batteries smaller. That would translate to less weight and, subsequently, greater range.

Of course, fast charging is important as well. You appreciate that your USB lithium-ion rechargeables can be recharged in an hour or so. Likewise, it is a safe bet that you do not want to wait at a charging station for that long when you’re trying to get to grandma’s house. You want to charge your EV as quickly as you used to fill your gas tank. So in addition to increasing energy density, engineers are working on speeding up charging. We will see how it goes.