Synergistic enhancement of ionic conductivity and cycling stability in tetracyanoethylene added PEO–LiTDI solid polymer electrolytes

This work reports the impact of tetracyanoethylene (TCE) addition on structural, mechanical, ionic conductivity, and electrochemical properties of poly(ethylene oxide) (PEO)-lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI) solid polymer electrolytes for Li-ion batteries. X-ray diffraction studies confirm that the addition of TCE amorphizes the crystalline regions of PEO, enhancing the amorphous phase and therefore the lithium-ion conductivity. The incorporation of TCE also further increased the elongation-at-fracture of the PEO 20 -LiTDI system, showing a remarkable improvement in mechanical flexibility. Ionic conductivity increased significantly with increasing TCE content and attained an optimal value of 4.15 × 10 − 4 S/cm at 40 wt% TCE, against 9.64 × 10 − 7 S/cm of the original system at room temperature (23 °C). The transference number measurement gave t ion = 0.968, indicating dominant ionic conduction, while LSV showed electrochemical stability up to 4.36 V. An optimized electrolyte showed an opening discharge capacity of 158.5 mAh g −1 at 0.1 C and presented 92.24% of its capacity retention after 100 cycles, featuring excellent interfacial stability and cycling durability when used in a solid-state lithium cell. The addition of TCE significantly improves the structural flexibility, mechanical stability, ionic transport, and resultant electrochemical performance of PEO 20 -LiTDI electrolytes for their applications to next-generation solid-state Li-ion batteries.