Researchers from Carnegie Mellon University and Missouri University of Science and Technology have developed a new method to 3D print battery electrodes. The new method creates a lattice structure that has a controlled porosity. The porosity improves the capacity and charge/discharge rates of lithium-ion batteries.

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. Source: Rahul Panat, Carnegie Mellon University College of EngineeringLattice 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. Source: Rahul Panat, Carnegie Mellon University College of Engineering

3D printing has previously been used to manufacture porous electrodes for lithium-ion batteries. But the design of the electrodes is limited to only a few architecture options because of the specific manufacturing process.

The internal geometry that produces the best porous electrodes using 3D printing is interdigitated geometry. It consists of metal prongs interlocked like the fingers of clasped hands, with the lithium traveling between the two sides. Because of the limited designs, the productivity of the batteries is also limited.

The research team believes that the capacity of lithium-ion batteries can be improved if the electrodes have pores and channels. The new 3D-printing method not only improves the capacity of lithium-ion batteries but also the charge and discharge rates.

"In the case of lithium-ion batteries, the electrodes with porous architectures can lead to higher charge capacities," says 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 percent of the total electrode volume is unutilized. Our method overcomes this issue by using 3D printing where we create a micro-lattice electrode architecture that allows the efficient transport of lithium through the entire electrode, which also increases the battery charging rates."

The new micro-lattice structure printed with the new 3D-printing method has proven to improve the battery performance. The structure showed four times increase in specific capacity and two times increase in areal capacity compared to a solid block electrode. The new electrodes retained the 3D lattice structures even after 40 electrochemical cycles. The new batteries have high capacity at the same or less weight as typical batteries.

The new 3D-printing method was demonstrated using an existing Aerosol Jet 3D-printing system. By using this system the researchers were able to print planar sensors and other electronics at a microscale. They also 3D-printed battery electrodes by rapidly assembling individual droplets into 3D structures that have complex geometries that were previously impossible.

"Because these droplets are separated from each other, we can create these new complex geometries," says 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 new technique could be a major development for consumer electronics, medical devices and the aerospace industry.

The paper on the research was published in the journal Additive Manufacturing.

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