Drop-on-demand 3D printing of lithium iron phosphate cathodes

Printed secondary batteries have market potential in two main fields - highly customized personal electronic devices, and smallscale battery production. While many different technologies may be utilized to produce a printed battery, drop-on-demand (DoD) dispensing has the advantage of being highly tailor-made, notably with the ability to produce both very thin and thick batteries. We report the cathode printing protocols, morphology and electrochemical properties of patterned electrodes. Our electrode inks are aqueous, with obvious environmental and processing benefits. We chose to study the lithium iron phosphate (LFP) cathode because of its excellent electrochemical performance. DoD-printed LFP cathodes exhibit close to theoretical capacity value, highrate capability and close to 100% coulombic efficiency. The similarity of the voltage profiles, electrochemical performance and impedance components of the AC spectra of lithium cells with printed LFP cathodes to those of commercial electrodes, indicates that printing does not alter the charge/discharge mechanism of active electrode material.