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

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.