Freeform Fabrication of Zinc Air Batteries with Tailored Geometry and Performance

This work is focused on the freeform fabrication of complete zinc-air batteries. This method of production gives great freedom in the geometry and construction of the battery, allowing tailoring of the output characteristics, and the possibility of embedding a customized battery within a larger integrated freeform fabricated device. Our batteries utilize a gelling agent to prevent phase separation in the zinc anode and catalyst layers, permitting the use of nozzles down to 1.3mm in diameter. Polyvinyl alcohol is utilized for the separator layer, which replaces the unprintable paper separator used in commercial batteries. With various freeform batteries we have achieved a specific capacity of 60mAh/g of zinc, an average power 7.25mW, and continuous service life of 63h, all with a load of 100 ohms. The specific capacity of our freeform batteries is about 1 order of magnitude lower than that of commercial zinc-air batteries, although under different test conditions. We have investigated the effect of cell active surface area on performance for a cylindrical cell-geometry, and have produced a flexible, two-cell battery with unusual geometry. The tailoring of performance and geometry possible with freeform fabrication will be of great value in the design of optimized smart devices with unusual geometry, portable electronics, and prototypes.Mechanical Engineerin