Conventional battery electrodes are made through processes requiring tooling. The ability to 3D print these electrodes opens new cell and pack geometries, as well as better energy density and performance. Photo Credits: Photocentric
The future of transportation is electric vehicles (EVs), and the heart of an EV is the battery. Yet the options for improving battery performance are limited with the methods currently used to make them.
How limited? Battery electrodes are commonly made by slip casting a slurry of active material into a sheet, punching out pouch or coin cells, and then arranging those cells to fit inside a rectangular or cylindrical casing. Creating a more powerful battery with this method entails building thicker electrodes — which can result in problematic cracking — and larger cells by stacking the electrodes on top of one another. The pursuit of better performance thus can lead to heavier, bulkier battery packs that don’t provide optimal efficiency or range for a given product.
Sarah Karmel, head of chemistry for Photocentric.
“There is no flexibility in the battery design,” says Sarah Karmel, head of chemistry for Photocentric, which is working on a solution. The UK-based provider of stereolithography-style 3D printers is currently exploring the promise of 3D printing electrodes for EVs and other battery-powered products such as drones. Additively manufactured electrodes that can be made in any shape and configuration could open the door to EVs that are faster to charge and lighter weight, translating to better range — and helping to overcome what have thus far been limiting factors for these vehicles.
3D Printing for Optimized Battery Electrode Architecture
Additive manufacturing (AM) has brought geometric freedom to other industries and applications; think a jet fuel nozzle that is now just one part instead of twenty, or a structural component for an electric car that is half the weight of its conventionally shaped and welded predecessor. The ability to 3D print batteries will bring geometric freedom as well, allowing cells and packs to be designed to fit the product, rather than forcing the product to accommodate a conventional battery pack. This is a significant change that could bring new freedoms to EV design. But this is just the start.
The flexibility Karmel sees for EV batteries is not limited to the overall shape of the cell or battery pack. There are additional design opportunities to be found within the electrodes themselves, the anodes and cathodes that together form battery cells. By working with a simulation partner, Photocentric is learning to design and 3D print optimized electrode architectures not previously possible.
Conventional battery electrode architectures (left) limit the possible configurations of the anode and cathode. A 3D printed architecture (right) allows for innovative designs like intercalated electrodes that increase energy density.
“The electrodes are working together in a different way,” Karmel says, and these new architectures support more energy-dense batteries that can occupy smaller, more geometrically flexible footprints. Anodes and cathodes can be made to intercalate, for example, to produce a cell that is more energy dense and efficient than one with a stacked configuration.
The 3D printing process makes it possible to alter the microstructure of the electrodes for better performance. Microscopic porosity introduces pathways for ions to wander, resulting in increased ion flow and greater volumetric energy density. The same amount of power can therefore be achieved from a smaller, lighter battery that can be made in a greater variety of configurations, to precisely fit the vehicle or application.
More pores provide more pathways for ions, which helps to increase energy density in a battery electrode.
Building Batteries with Photopolymerization
The process for these 3D printing batteries is similar to creating any other part with a photopolymerization process. The electrodes are 3D printed using a proprietary photopolylmer resin that serves as a binder for commercial electrode powder and conductive additives; the green printed parts are then cleaned and cured, followed by debinding and sintering to remove the polymer and leave only the active electrode material behind. Photocentric has actually developed a self-contained system for 3D printing batteries; parts travel from printing to washing and postprocessing automatically, avoiding the risks of contamination or damage to delicate electrodes.
The 3D printed battery project likely to have an impact on electric vehicles also dovetails with Photocentric’s pursuit of sustainability in its own operations. Photocentric 3D printers rely on visible rather than UV light to cure photopolymer parts — a factor that means the machines use less energy to run. New sustainable materials from renewable sources and recycling efforts are also underway.
Thus far the company is working with electrode materials including lithium cobalt oxide (LCO) and lithium titanate (LTO); Karmel says the platform is material agnostic and could support other established battery chemistries as well. Photocentric’s aim now is to find industry partners that can provide input on the best chemistry and most useful geometries, and to demonstrate its 3D printed batteries in a vehicle.
“We can print batteries that work in the lab, but the question now is how will it perform in the device itself?” Karmel asks. If successful in use, 3D printed battery electrodes could lay the groundwork for lighter electric vehicles that offer better range, without changing the size of the battery pack; or for smaller battery packs in more convenient shapes and configurations that can provide the same range as today’s large arrays of heavy cells. Better performance could increase EV adoption and in turn, point toward more sustainable transportation.
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