Kaolinite Reinforced β-Phase-Enriched Electrospun PVDF-HFP Nanocomposite Separator for Sodium-Ion Batteries

Abstract

Sodium-ion batteries (SIBs) have emerged as key technologies, and separator engineering plays a pivotal role in improving their performance. This study reports a nonwoven separator fabricated by electrospinning that incorporates kaolinite, a naturally occurring clay mineral, into the host polymer PVDF-HFP, which has highly polar sites that provide a high affinity for the polar electrolyte. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses confirmed the successful incorporation of kaolinite into the electrospun PVDF-HFP matrix. At the same time, the electrospun nanocomposite separator exhibited a high β-phase content, indicating the formation of highly electroactive phases. Field emission scanning electron microscopy (FESEM) analysis revealed a porous nonwoven fibrous architecture with uniform fiber distribution, indicating the successful formation of a continuous nanofibrous network. The electrochemical performance was evaluated through the galvanostatic charge−discharge (GCD), rate capability, cyclic stability, and electrochemical impedance spectroscopy (EIS) of the half-cell. The polymer composite separator exhibited an ionic conductivity of 1.80 mS cm−1. The specific discharge capacity of 153.8 mAh g−1 was achieved at a 0.1 C rate, with 77% capacity retention after 200 charge−discharge cycles at a 0.5 C rate. Furthermore, the separator demonstrated improved thermal stability and mechanical strength, thereby enabling a safer battery operation. These results highlight the effectiveness of the Kaolinite reinforced β-phase-enriched electrospun PVDF-HFP nanocomposite separator for SIBs.