Jul 31 2018
Additive manufacturing, also called 3D printing, can be used for fabricating porous electrodes for lithium-ion batteries; however, the nature of the fabrication process is such that the design of these 3D-printed electrodes is restricted to only a few potential architectures.
Lattice architecture can provide channels for effective transportation of electrolyte inside the volume of material, while for the cube electrode, most of the material will not be exposed to the electrolyte. (Image credit: Rahul Panat and Mohammad Sadeq Saleh)
To date, the so-called interdigitated geometry is the internal geometry that created the best porous electrodes via additive manufacturing. In the interdigitated geometry, metal prongs are interlocked similar to the fingers of two clasped hands, with the lithium traveling between the two sides.
The capacity of the lithium-ion battery can be considerably enhanced if, on the microscale, their electrodes contain channels and pores. An interdigitated geometry is not optimal, although it does enable lithium to efficiently transport via the battery during the charge-discharge cycle.
Rahul Panat, an associate professor of mechanical engineering at Carnegie Mellon University, and a group of scientists from Carnegie Mellon in association with Missouri University of Science and Technology have developed a ground-breaking technique for manufacturing battery electrodes with the help of Aerosol Jet 3D printing. This new method produces a 3D microlattice structure with controlled porosity. The researchers showed that 3D printing this microlattice structure considerably enhances the capacity as well as the charge-discharge rates for lithium-ion batteries. Their study has been reported in the journal, Additive Manufacturing.
In the case of lithium-ion batteries, the electrodes with porous architectures can lead to higher charge capacities. 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.
Rahul Panat, Associate Professor of Mechanical Engineering
Presented in Panat’s paper, the additive manufacturing method represents an important development in printing intricate geometries for 3D battery designs, and also marks a major step toward geometrical optimization of 3D configurations for storing electrochemical energy. According to the researchers, this technology could be used in industrial applications in approximately two to three years.
When compared to a solid block (Ag) electrode, the microlattice structure (Ag) utilized as lithium-ion batteries’ electrodes was demonstrated to enhance the performance of the battery in a number of ways, for example, a twofold increase in areal capacity and fourfold increase in specific capacity. In addition, the electrodes were able to retain their intricate 3D lattice structures following 40 electrochemical cycles underscoring their mechanical strength. Thus, the batteries can either have high capacity for the same weight or, for the same capacity, a considerably reduced weight, which is a significant feature for transportation applications.
Researchers at the Carnegie Mellon devised their own 3D printing technique to produce the porous microlattice architectures and simultaneously leveraged the prevalent capabilities of an Aerosol Jet 3D printing system. This printing system also enables the team to print a range of electronics, including planar sensors, on a micro-scale, and earlier this year, was installed at the College of Engineering of Carnegie Mellon University.
So far, 3D-printed battery attempts were mainly restricted to extrusion-based printing, where a material wire is extruded from a nozzle, producing continuous structures. This method was used to produce interdigitated structures. With the development of this method in Panat’s laboratory, the research team can 3D print the battery electrodes by quickly assembling separate droplets one-by-one into 3D structures. The structures, thus obtained, have intricate geometries that cannot be fabricated using standard extrusion techniques.
Because these droplets are separated from each other, we can create these new complex geometries. If this was a single stream of material, as 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.
Rahul Panat, Associate Professor of Mechanical Engineering
This ground-breaking technique will be very significant for the medical devices industry, consumer electronics, and also aerospace applications. Since biomedical electronic devices require miniaturized batteries, the study will integrate well with these instruments. This work will also benefit non-biological electronic micro-devices. On a bigger scale, this technology can also be used by small drones, electronic devices, and aerospace applications themselves because of the high capacity and low weight of the batteries printed through this method.
Postdoctoral researcher Jie Li (Missouri University of Science and Technology) and Mechanical engineering Ph.D. student Mohammad Sadeq Saleh, both part of the team, are also exploring ways to create 3D structures that are more complex. Such structures can concurrently be utilized as functional materials and as structural materials. For instance, a part of a drone can function as a structural material, a win, and at the same time act as a functional material, for example, a battery.