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Jul 31, 2018 | By Thomas

Engineers at the Carnegie Mellon University have developed a new method of 3D printing battery electrodes that creates a 3D microlattice structure with controlled porosity. Their 3D printing method could lead to vastly improved capacity and charge-discharge rates for lithium-ion batteries.

Lithium-ion battery capacity can be vastly improved if their electrodes have pores and channels. Until now, the internal geometry that produced the best porous electrodes through additive manufacturing was interdigitated geometry ((i.e., metal prongs interlocked like the fingers of two hands, with the lithium moving between the two sides), which allows lithium to transport through the battery efficiently during charging and discharging. But it is not optimal.

Rahul Panat, an associate professor of mechanical engineering at Carnegie Mellon University, and a team of researchers from Carnegie Mellon in collaboration with Missouri University of Science and Technology have developed a new method of fabricating battery electrodes using aerosol jet 3D printing, and their results are published in the journal Additive Manufacturing.

The cross-section view shows the silver mesh enabling the charge (Li+ ions) transportation to the current collector and how most of the printed material has been utilized.
Credit: Rahul Panat, Carnegie Mellon University College of Engineering

"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 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," Panat explained.

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. Also, the electrodes retained their complex 3D lattice structures after forty electrochemical cycles demonstrating their mechanical robustness.

SEM images of 3D printed electrodes for Li-ion batteries used for electrochemical cycling in the researchers’ study. Image taken from top of microlattice electrodes with height of about 250mm. Source: Rahul Panat and Mohammad Sadeq Saleh

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.

The Carnegie Mellon researchers developed their own 3D printing method to create the porous microlattice architectures while leveraging the existing capabilities of an Aerosol Jet 3D printing system. With this method, the researchers are able to 3D print the battery electrodes by rapidly assembling individual droplets one-by-one into 3D 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 3D printing to create these kinds of complex structures."

This 3D printing method will be very important for consumer electronics, medical devices industry, as well as aerospace applications. The researchers estimate that this technology will be ready to translate to industrial applications in about 2-3 years.

 

 

Posted in 3D Printing Application

 

 

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