Layered Vanadium Disulfide Electrodes for Printed Zinc Ion Batteries

Aqueous Zinc Ion Batteries (ZIBs) are receiving growing attention as beyond-lithium power sources for wearable electronics and sensors, owing to their high theoretical capacity, environmental friendliness, and low cost. However, Zn²⁺ ions have a high charge density, almost double the charge density of Li⁺, which is detrimental for the intercalation kinetic and the structural stability of the battery electrodes.<br/>Layered transition metal dichalcogenides (TMDs) have ideal features for high-performing energy storage devices, including high surface area and large two-dimensional diffusion channels inside their structure. The adjacent layers in the TMD structure are connected by weak van der Waals interactions, resulting in a large interlayer spacing which enables rapid ion diffusion kinetic and promotes the reversible insertion and extraction of multivalent ions. Among TMDs, vanadium disulfide is a promising cathode material for ZIBs, owing to its large interlayer spacing (~ 5.76 Å) and metallic character. Despite these beneficial features, vanadium disulfide has mainly been investigated in coin-cell batteries, which are difficult to directly integrate in wearable electronics.<br/>Here, we demonstrate the combination of an easily-scalable hydrothermal synthesis with a room-temperature 3D Printing process to fabricate vanadium disulfide electrodes with customized geometry. The hydrothermal vanadium disulfide was mixed with a polymeric binder and conductive additives to obtain a stable ink with optimal printability. The architecture of the VS₂ electrodes was rationally tailored <i>via </i>the printing process to facilitate the electrolyte penetration and promote fast charge transfer. Finally, the printed vanadium disulfide electrodes were coupled with zinc anodes to assemble aqueous zinc-ion batteries. The full cells were tested in a water-in-salt electrolyte, which improved the stability of the vanadium disulfide electrode, extending the achievable potential window and energy density.