Improved energy density could be as crucial to our clean-energy future as the flux capacitor is to time travel.
Fortunately, the former bit of science isn't make-believe. If perfected, energy density could revolutionize the use of clean power and its effectiveness at electrifying our vehicles, homes, and devices.
What's more, you don't have to be Doc Brown to understand the terminology and its importance.
What is energy density?
Energy density is how much energy can be stored in a battery in relation to its mass, per the Department of Energy. Power density, on the other hand, is the amount of juice a battery can supply (the rate it can transmit the energy) in relation to its mass.
Batteries that energize our EVs, drones, and even boats have energy and power densities.
"To draw a clearer picture, think of draining a pool. Energy density is similar to the size of the pool, while power density is comparable to draining the pool as quickly as possible," according to the DOE description.
Danilo Onorino, global energy portfolio manager for Dogma Capital SA, explained in a LinkedIn article that energy density is typically measured by the amount of energy stored per battery volume or by the amount of energy stored per battery weight.
Drones, for instance, need high gravimetric energy density (energy by weight) in their battery packs, so the craft's weight is low for successful flight, per Onorino's description.
Why is energy density important?
Better energy density benefits our daily lives, resulting in smaller and/or lighter batteries. In EVs, that means lighter vehicles with more passenger space that can travel farther on each charge.
As Onorino explained, high energy density also allows smartphones to be made thinner.
"Energy density is a critical factor in battery performance and determines the practicality of batteries for various applications," according to Onorino.
Improved energy density can also lower the cost of battery production and materials, per the LinkedIn report.
How is energy density improved and maximized?
Scientists worldwide are experimenting with different kinds of battery materials that are thinner, lighter, and can store more energy. Onorino wrote that swapping silicon in for graphite as an anode material could be one improvement, for example.
Supercapacitor technology could greatly benefit from energy density breakthroughs. For example, experts at the University of California San Diego recently created a structural supercapacitor in the form of a mini boat.
Using a flexible, durable, and conductive material shaped into the form of a boat hull, they added an anode, cathode, and other battery parts, forming a supercapacitor. A single solar panel can charge the handheld craft. Fascinatingly, the craft's structure serves as its battery.
The boat has a high power density (meaning its components can transmit energy quickly); however, experts must improve its energy density. If they can, boats, cars, and our devices could one day be powered by their own structures, thanks to the improved energy density in the structural supercapacitor.
"While today's lithium-ion batteries have achieved impressive energy densities … the fundamental limits of both volumetric and gravimetric energy density are being approached [and] to achieve higher energy density, next-generation technologies and materials are necessary," Onorino explained, noting also that "the pursuit of better energy density is driven by the constant competition to outperform rivals in various industries."
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