Researchers from Carnegie Mellon University and the Missouri University of Science and Technology have developed a new technique for 3D printing battery electrodes that could dramatically improve the capacity of lithium-ion batteries as well as charging rates. The innovative method, recently published in the journal Additive Manufacturing, is capable of producing a 3D microlattice structure with controlled porosity in side the battery electrodes.
Though additive manufacturing has been used in the past to print porous electrodes for lithium-ion batteries, the scope of 3D printed batteries has still been limited to a handful of architectures, which in turn has limited the capacity of the batteries. As the researchers explain, typical 3D printed geometries for porous electrodes used interdigitated geometries, which resemble interlocking metal prongs with lithium shuttling between the two sides. By adding a microlattice porous structure to the 3D printed electrodes, the researchers have further optimized the capacity of 3D printed batteries significantly.
“In the case of lithium-ion batteries, the electrodes with porous architectures can lead to higher charge capacities,” explained Rahul Panat, associate professor of mechanical engineering at Carnegie Mellon University. “This is because such architectures allow the lithium to penetrate through the electrode volume leading to very high electrode utilization, and thereby higher energy storage capacity. In normal batteries, 30-50% of the total electrode volume is unutilized. Our method overcomes this issue by using 3D printing where we create a microlattice electrode architecture that allows the efficient transport of lithium through the entire electrode, which also increases the battery charging rates.”
The 3D printing technique in question was developed by the Carnegie Mellon research team though it also relied on an existing Aerosol Jet 3D printing system installed at the College of Engineering this year. The Aerosol Jet system has enabled the team to print planar sensors and electronics on a micro-scale, which has furthered the research project.
Interestingly, the researchers say their project marks one of the first instances where 3D printed batteries have been made using a non-extrusion based method. That is, rather that utilize a wire feedstock and nozzle extrusion, the team has demonstrated the ability to produce battery electrodes by depositing tiny droplets into 3D printed structures. This approach has increased the complexity achievable for the battery structures.
“Because these droplets are separated from each other, we can create these new complex geometries,” added Panat. “If this was a single stream of material, as is in the case of extrusion printing, we wouldn’t be able to make them. This is a new thing. I don’t believe anybody until now has used 3D printing to create these kinds of complex structures.”
In terms of the benefits of the 3D printed electrodes, the researchers say the printed microlattice structure used as a lithium-ion battery’s electrodes improved battery performance in a range of ways. For one, they reported a fourfold increase in specific capacity and a twofol increase in areal capacity compared to a solid block electrode. The 3D printed electrodes are also mechanically robust as they retained their lattice structure after 40 electrochemical cycles. Importantly, because of their porous structure, the lithium-ion batteries are also lighter than counterparts of the same capacity.
The innovative research marks an important breakthrough in the 3D printing of battery architectures as well as a step forward to achieving geometrically optimized 3D configurations for electrochemical energy storage. According to the team, the 3D printed battery technology could be ready for industrial applications in as soon as two to three years.
Looking to applications, Panat and his team believe the 3D printing method for batteries could have an important impact in the realms of consumer electronics, medical devices and aerospace. For applications where miniaturized batteries are required—such as for biomedical devices—the improved 3D printed batteries could also prove vital.