Electrochemical Study of Poly(2,6‐Anthraquinonyl Sulfide) as Cathode for Alkali‐Metal‐Ion Batteries

Abstract Organic electrode materials are extensively applied for alkali metal (lithium, sodium, and potassium)‐ion batteries (LIBs, SIBs, and PIBs) due to their sustainability and low cost. As a typical organic cathode, poly(2,6‐anthraquinonyl sulfide) (PAQS) shows high theoretical capacity, yet its electrochemical behavior and mechanisms in alkali‐metal‐ion batteries still require clarification. Herein, PAQS microspheres are synthesized and applied as cathodes for LIBs, SIBs, and PIBs. When using traditional low‐concentration electrolytes, the reduction voltage and the initial discharge capacity of PAQS electrode in LIB, SIBs, PIBs are 2.11 V/103 mAh g −1 , 1.76/1.30 V/134 mAh g −1 , 1.94/1.54 V/198 mAh g −1 at 100 mA g −1 , respectively, while the cycling stability of PAQS is in the order of LIBs > SIBs > PIBs. To further promote the practical application of PIBs, a facile method is demonstrated to improve the cycle stability of PAQS for PIBs by using a novel high‐concentration electrolyte. The cycling stability of PIBs with PAQS can be improved significantly to 1200 cycles with a capacity decay of 0.031% per cycle. This work may provide guidelines for developing innovative organic materials used in applicable metal‐ion batteries demonstrates the impact of electrolyte optimization on improving the cycling stability.