High adherent polyacrylonitrile as a potential binder for high-capacity Fe7S8 cathode

FeSx (1 ≤ x ≤ 1.14) is one of the most promising conversion-type cathodes as lithium metal batteries due to its low-cost and high energy density. Nevertheless, it suffers from heavy volume change, which brings in fast capacity decay. In this study, we employ four different binders (PVDF, PAN, SBR/CMC, and PAA/CMC) to improve their electrochemical performance. It is found that PAN demonstrates the best performance from 559.5 mAh/g (first) to 458.5 mAh/g (100th) at 0.2 C in the voltage window of 1.0 − 3.0 V. This can be ascribed to its high adhesion strength, good electrical conductivity, low swelling properties, high polarity, and good mechanical stability. The findings highlight the importance of a binder material to guide good cycling stabilities for conversion-type or high-volume change cathodes.