Carbon-Doped Graphitic Carbon Nitride Inorganic Filler in Solid Polymer Electrolytes for All-Solid-State Batteries

In the quest to enhance the safety of lithium-ion batteries, substantial research is underway to develop all-solid-state batteries, facing challenges in achieving high ion conductivity in solid electrolytes. This study aims to enhance the ion conductivity by incorporating carbon-doped graphitic carbon nitride (C-doped g-C₃N₄) microspheres as an inorganic filler into the poly(ethylene oxide)-based solid polymer electrolyte (SPE). Leveraging the advantageous properties of g-C₃N₄ as an effective inorganic filler by enhancing its Lewis acid-base interactions with lithium, we modified g-C₃N₄ through carbon doping to improve the ionic conductivity of the SPE. Our experimental analysis supports the increased lithium transference number after hybridizing electrolytes with C-doped g-C₃N₄, signifying heightened ion mobility resulting from carbon substitution on g-C₃N₄. Subsequent density functional theory (DFT) calculations reveal increased lithium binding energy due to the carbon doping of g-C₃N₄, thereby ultimately enhancing the ion conductivity by promoting salt dissociation. Optimizing carbon doping levels and hybrid electrolyte composition yields improved ion conductivity and electrochemical performance, with optimal outcomes observed at 7% C-doped g-C₃N₄ with SPE. Evaluation in a pouch cell with the NCM811 cathode underscores the applicability of the hybrid electrolyte on a large scale, showcasing promising advancements in battery technology. Our carbon-doped g-C₃N₄ filler demonstrates promising potential in advancing ion conductivity through enhanced salt dissociations.