Laser Assisted Rapid Prototyping of In-Plane, Flexible, Rechargeable Aqueous Zn-S Batteries

CO₂ laser-assisted graphitization of high-melting-point polymers, such as polyimide enables customizable patterning for rapid fabrication of microelectronics and miniaturized energy storage devices. Herein, we present the inaugural demonstration of an ultrafast fabrication of a binder-free flexible in-plane zinc-sulfur battery with laser-induced graphene (LIG) supported interdigitated electrodes, i.e., zinc anode and sulfur cathode. We demonstrate a sublimation-transport-desublimation process for trapping and redistributing elemental sulfur onto laser-induced graphene (LIG) via direct laser treatment, leading to the deposition of plastic/amorphous sulfur. This process enables a uniform sulfur distribution within the LIG matrix and enables covalent bonding with the defect sites of LIG, resulting in a binder-free, high-sulfur-content S@LIG electrode with a sulfur content ∼58 ± 13.8%. The sulfur species during the discharge/charge process were studied via ex situ XRD/XPS analysis. We observed that the shuttling of soluble sulfates, generated from oxidized sulfur during laser treatment, induces parasitic reactions with zinc in aqueous electrolytes, leading to accelerated capacity fading. This issue was mitigated using a gel polymer electrolyte. A semi-solid-state, flexible in-plane Zn-S prototype cell was demonstrated, delivering impressive electrochemical performance with a capacity of 59 µAh cm^{- 2}, sustained over 80 cycles at a current density of 25 µA/cm².