Graphitic carbon nitride assisted PVDF-HFP based solid electrolyte to realize high performance solid-state lithium metal batteries

Abstract

Solid polymer electrolyte (SPE) is routinely regarded as core component to tackle the potential safety hazards and energy density of conventional lithium-ion batteries. However, it is still beset by low ionic conductivity and poor interface compatibility. Currently, the utilization of SPEs to replace flammable and leaky liquid electrolytes is regarded as a powerful method to promote battery security. However, it is still an arduous task to develop a SPE with a wider electrochemical window and higher ionic conductivity. Herein, graphitic carbon nitride (g-C3N4) nanosheets were prepared by thermal oxidative exfoliation and introduced into PVDF-HFP based SPEs to prepare solid composite electrolyte for the first time. The introduction of g-C3N4 nanosheets effectively disrupts the orderly arrangement of polymer segments in the SPE, thereby diminishing the crystallinity of the solid electrolyte. The results prove that the presence of g-C3N4 nanosheets efficiently reduces the bulk impedance of the solid electrolyte membrane, enhance the ionic conductivity and ion transport number, and boost the oxidation potential and stability of the electrolyte membrane to the lithium anode. The ionic conductivity of SPE with 15 wt% g-C3N4 nanosheets is 1.67 × 10−4 S·cm−1 at 25 °C, and its oxidation potential reaches 4.7 V. The NCM622/PCSE3/Li battery delivered a specific discharge capacity of 122.8 mAh·g−1 after 100 cycles at 0.5 C.