Rahul Panat, an associate professor of mechanical engineering at Carneige, worked with Missouri University of Science and Technology to 3D print this microlattice structure.
“In the case of lithium-ion batteries, the electrodes with porous architectures can lead to higher charge capacities,” said Panat. “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 unused. 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 researchers estimate that this technology will be ready to translate to industrial applications in two to three years.
The microlattice structure (Ag) used as lithium-ion batteries’ electrodes was shown to improve battery performance in several ways such as a fourfold increase in specific capacity and a twofold increase in areal capacity when compared to a solid block (Ag) electrode. The electrodes retained their complex 3D lattice structures after forty electrochemical cycles, demonstrating their mechanical robustness and allowing a high capacity for the same weight or alternately, for the same capacity, a vastly reduced weight for transportation applications.
The researchers had to develop a new 3D printing method to create the porous microlattice architectures while using the existing capabilities of an Aerosol Jet 3D printing system. This also allows the researchers to print planar sensors and other electronics.
Until now, 3D printed battery efforts were limited to extrusion-based printing, where a wire of material is extruded from a nozzle, creating continuous structures. Interdigitated structures were possible using this method. With the method developed in Panat’s lab, the researchers are able to 3D print the battery electrodes by rapidly assembling individual droplets one-by-one into three-dimensional structures. The resulting structures have complex geometries impossible to fabricate using typical extrusion methods.
“Because these droplets are separated from each other, we can create these new complex geometries,” said 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 3-D printing to create these kinds of complex structures.”
The technique could be used for consumer electronics, medical devices industry, as well as aerospace applications. This research will integrate well with the biomedical electronic devices, where miniaturized batteries are required.
The team, which also includes mechanical engineering Ph.D. student Mohammad Sadeq Saleh at Carnegie and postdoctoral researcher Jie Li at the Missouri University of Science and Technology, is also working on creating more complex three-dimensional structures, which can simultaneously be used as structural materials and as functional materials. For example, a part of a drone can act as a wing, a structural material, while simultaneously acting as a functional material such as a battery.