Improving Registration Accuracy of Multilayer Screen-Printed Graphite Electrodes with Secondary Pore Networks for Fast Charging Lithium-ion Batteries

Abstract

A multi-layer screen-printed flexible graphite electrode-based lithium-ion battery was fabricated with improved registration accuracy. Laser patterning process was employed to create the registration marks on the substrate for aligning the samples during multi-layer screen-printing. A homogenous ink slurry was prepared by mixing graphite as active material along with carbon black (Super-P C45) as conductive additive and polyvinylidene fluoride (PVDF) as binder in N-Methyl-2-pyrrolidone (NMP) solvent. A two-layered lithium-ion battery electrode was prepared by depositing the homogeneous slurry via screen consisting of 100 µm pore pattern design with edge to edge distance of 100 µm (between pores) on a flexible copper foil using screen printing process. The two layers provided the required mass loading of 2.6 mg/cm2 which results in high-capacity density. The pore structures of the second electrode layer were aligned well with the first printed electrode layer with the help of registration marks during screen printing process. The presence of secondary pore networks facilitates paths for accelerated ionic transfer of lithium ions along the electrode leading to fast-charging batteries with high capacity density. The electrodes were calendered to obtain an average porosity of ~33% for 2 layers. Half-cell was assembled using lithium foil as anode, screen-printed graphite ink as cathode and lithium hexafluorophosphate (LiPF6) as electrolyte. The multilayer graphite electrode processed with well aligned pore networks (feasible because of laser based registration marks) and screen-printing showed a capacity of 348mAh/g at 0.1 C formation at the end of 3 cycles.