A new insight into capacity fading of sulfurized polyacrylonitrile composite in carbonate electrolyte

Abstract Sulfurized polyacrylonitrile (S/PAN) composite shows great potential as a cathode material for lithium sulfur batteries, due to its advantages in cycle performance and carbonate electrolyte compatibility. However, the cell using S/PAN composite as a cathode material exhibits sluggish reaction kinetics due to the low conductivity. Moreover, capacity fading is also found in long-term cycle test and the mechanism is not well studied in previous reports. In this work, a compact composite, S/PAN confined in macro-porous carbon (MaPC), is firstly prepared by using a sulfur copolymer to improve the cycle stability. The cathode shows stable cycle stability during the initial 150 cycles at the current density of 1050 mA gsulfur−1 and the capacity maintained at 806 mAh gsulfur−1. The cycle stability is getting worse during the long-term cycle test. It is found that the capacity fading is highly related to the increasing resistance and the formation of sulfates or sulfate-like components during the repeated cycling process.