Patterning Planar, Flexible Li-S Battery Full-Cells on Laser-Induced Graphene Traces

Laser conversion of commercial polymers to laser-induced graphene (LIG) using inexpensive and accessible CO2 lasers has enabled rapid prototyping of promising electronic and electrochemical devices. Frequently used to pattern interdigitated supercapacitors, few approaches have been developed to pattern batteries – in particular full cells. Herein, we report an LIG-based approach to a planar, interdigitated Li-S battery. We show that sulfur can be deposited by selective nucleation and growth on the LIG cathode fingers in a supersaturated sulfur solution. Melt imbibition then leads to loadings as high as 3.9 mg/cm2 and 75 wt% sulfur. Lithium metal anodes are electrodeposited onto the LIG anode fingers by a silver-seeded, pulse-reverse-pulse method which enables loadings up to 10.5 mAh/cm2 to be deposited without short-circuiting the interdigitated structure. The resulting binder/separator-free flexible battery achieves a capacity of over 1 mAh/cm2 and an energy density of 200 mWh/cm3. Unfortunately, due to the use of near stoichiometric lithium, the cycle-life is sensitive to lithium degradation. While future work will be necessary to make this a practical, flexible battery, the interdigitated structure is well-suited to future operando and ex situ studies of Li-S and related battery chemistries.