Additive manufacturing (3D printing) can be used to manufacture porous electrodes for lithium-ion batteries, but because of the nature of the manufacturing process, the design of these 3D-printed electrodes is limited to just a few possible architectures. Until now, the internal geometry that produced the best porous electrodes through additive manu-factoring was what's known as an interdigitated geometry — metal prongs interlocked like the fingers of two clasped hands, with the lithium shuttling between the two sides.
Lithium-ion battery capacity can be vastly improved if, on the microscale, their electrodes have pores and channels. An interdigitated geometry, though it does allow lithium to transport through the battery efficiently during charging and discharging, is not optimal.
A new method of 3D-printing battery electrodes was developed that creates a 3D microlattice structure with controlled porosity. 3D-printing this microlattice structure vastly improves the capacity and charge-discharge rates for lithium-ion batteries. These 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 to 50% of the total electrode volume is unutilized. The new method overcomes this issue by using 3D printing to create a microlattice electrode architecture that allows the efficient transport of lithium through the entire electrode, which also increases the battery charging rates.
The additive manufacturing method represents a major advance in printing complex geometries for 3D battery architectures, as well as an important step toward geometrically optimizing 3D configurations for electrochemical energy storage. The researchers estimate that this technology will be ready to translate to industrial applications in about 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. Furthermore, the electrodes retained their complex 3D lattice structures after 40 electrochemical cycles, demonstrating their mechanical robustness. The batteries can thus have high capacity for the same weight or alternately, for the same capacity — a vastly reduced weight and an important attribute for transportation applications.
The 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 new 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.