Battery energy density is the amount of energy a battery contains compared to its weight or size. We call this the specific energy density when comparing to weight and volumetric energy density when comparing size.
For example, we measure a battery’s energy in watt-hours (watts per hour, the equivalent of using one watt for one hour). We can then divide a battery’s watt hours (wh) by its kilograms (weight) or volume (liters).
Therefore, the length of time a battery can power a device compared to its weight or size equals the energy density.
Why Does Battery Energy Density Matter?
Battery energy density is crucial because the higher the energy density, the longer the battery can emit a charge in relation to its size. That being said, high energy density batteries can be useful when there isn’t much room for a battery but you need a lot of energy output. Smartphones and other handheld devices are great examples of this. Let’s pose the benefits of energy density as a question: Would you rather have a small, lightweight battery that emits power for long periods or a heavy battery that takes up a lot of space and only provides a small amount of energy? Almost everyone would say the former. This is why high energy density is vital in our world.Energy Density vs. Power Density in Batteries
It’s easy to confuse energy density and power density because they’re similar in certain ways. They both measure an electrical characteristic of a battery in comparison to its weight. Nevertheless, energy density and power density differ in one important way: while battery energy density measures the watt hours (wh) per kilogram (kg), power density measures the watt output per kilogram. This is where power vs. energy comes into play. Power density measures how fast energy can be delivered, while energy density measures how much energy a battery holds.
What Are the Benefits of Using Batteries with High Energy Density?
Batteries with high energy density have transformed the mobile world. With more energy, we can fit useful batteries in smaller spaces. This enables long-lasting phones, laptops, earbuds, or medical devices. They’re also very lightweight compared to past alternatives. Could you imagine carrying around a 5lb iPhone? Or a 10lb tablet? More energy density also means we can pack a lot of energy into larger mobile devices like cars, planes, construction equipment, and robots.What Are the Risks of High Energy Density?
When a battery packs more energy in it, it has more energy to release if something goes wrong. The liquid electrolytes found in lithium-ion batteries are highly volatile and can lead to combustion, presenting a fire hazard. Because of this, there are safety features built into these batteries, limiting how lightweight and compact they can be. Therefore, the higher the energy density of a battery, the more dangerous it can be, which poses limitations (and risks) to further advancement.What Battery Currently Has the Highest Energy Density?
Hands down, lithium-ion batteries take the cake when it comes to high energy density. They’ve transformed our world with advancements in energy consumption and portability. In fact, lithium-ion batteries’ energy density ranges between 260-270 wh/kg, while lead-acid batteries range from 50-100 wh/kg.
Overcoming Limits: Solid-State Batteries
So if we’re reaching our limits in lithium-ion battery advancements, where do we go from here? The future of battery technology lies in solid-state batteries. Remember how lithium-ion batteries have a liquid electrolyte solution? The liquid state of this solution is a fundamental problem. It’s unstable, volatile when exposed to oxygen, and can be a considerable safety risk. It also limits advancements in size and energy density because of these safety concerns. Well, solid-state batteries eliminate these issues. The electrolyte is a solid rather than a liquid in these batteries and thus has a higher energy density (2.5 times more) than current lithium-ion batteries. They also have faster charging times and fewer safety concerns, making the batteries smaller and more compact. While solid-state batteries aren’t readily available yet, they might revolutionize our world once again.
