Drop-on-Demand 3D Printed Lithium-Ion Batteries

Abstract

The recent trend of accelerated miniaturization of electronic devices has increased the demand for microbatteries of different geometries and chemistries, with high customizability and low manufacturing cost. Devices for applications such as personal wearable electronics, medical implants and remote sensors require small-size, but high-energy-density batteries, often with extraordinary design restriction and highly specific requirements. To facilitate the production of microbatteries of this type, we plan to use drop-on-demand dispensing, a highly robust printing method already used for various types of functional materials. This method, based on piezoelectrically actuated mechanical droplet formation, enables high accuracy and repeatability in the printing of active-material inks with different properties and rheology parameters. We have used this method to print various types of active materials for lithium-ion batteries, including cathode (lithium iron phosphate, LFP) and anode (silicon-nickel-based nanoparticles). Both yielded repeatable printability at a resolution below 200µm, which allows customization of the printing to various geometries, including 3D construction of upright electrodes. We found that the electrochemical performance of printed active materials is highly competitive with traditional manufacturing methods. Cathodes show very high specific capacity, up to 160mAh/g LFP, close to its theoretical capacity and good cyclability. Electrochemical impedance spectroscopy of cathodes shows that cathode chemistry and performance are unaffected by the printing process. Hence, direct implementation of well-established equivalent-circuit models is enabled for data analysis. Anodes also show high capacity – up to 1200mAh/g anode – and electrochemical behavior consistent with that of anodes prepared by traditional methods. We studied the adhesion of printed anodes to several current collectors and present methods of improving it. The anodes with improved adhesion gave longer cycle life and better performance of microbatteries printed in nonconventional geometries. Our results inspire further studies, development of manufacturing protocols, and designs for highly customizable batteries. Such development is of particular importance for small-scale and flexible production in many fields of applications, such as in-situ 3D printing of embedded batteries during the assembly process of electronic devices.