New 3D printing method gives boost to lithium-ion batteries

Engineers in the US have developed a 3D printing method that 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 contain microscale pores and channels. To date, the internal geometry that produced the best porous electrodes through additive was interdigitated, which allows lithium to transport through the battery efficiently during charging and discharging, but is not optimal.

Now, 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 3D printing battery electrodes that creates a 3D microlattice structure with controlled porosity. Their results are published in Additive Manufacturing.

"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 utilisation, and thereby higher energy storage capacity. In normal batteries, 30-50 per cent of the total electrode volume is unutilised. 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 microlattice structure (Ag) used as lithium-ion batteries' electrodes was shown to provide a fourfold increase in specific capacity and a twofold increase in areal capacity compared to a solid block (Ag) electrode. According to CMU, the electrodes also retained their complex 3D lattice structures after forty electrochemical cycles, demonstrating their mechanical robustness.

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.

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 3D printing to create these kinds of complex structures."

The researchers estimate that technology from this new 3D printing method will be ready for industrial applications in approximately two-to-three years.