| Popis: |
Aqueous zinc-ion batteries (AZIBs) provide alternative methods for expanding energy storage due to the inexpensive, safe, and non-toxic nature of zinc. The exploration of viable organic cathodes that can store Zn2+ with high reversibility and with fast kinetics is currently lacking. To elucidate the viability of bond formation in low-cost organosulfur compounds as organic cathode materials (OEMs), we investigate how functionalization of Zn-thiolate complexes 1 and 2 affects the electrochemical performance in coin-type cells. The energy storage mechanism was ascertained as a predominant (de)insertion of Zn2+ with a minor (de)insertion of H+ via ex-situ analysis of Zn-2 cells with X-ray fluorescence, Raman spectroscopy, and power X-ray diffraction. H+ insertion forms the thiol 4, whose higher solubility and higher voltage polarization leads to capacity decay in Zn-2 cells. Formation of 4 was verified via a pH-dependent galvanostatic cycling study. Strategies to prevent H+ insertion were investigated by increasing Zn2+ concentration and using a Nafion membrane. The optimized conditions for Zn-2 cells display 107 mAh g-1 initial specific capacity with 71% capacity retention over 100 cycles. This study provides insight into the implementation and optimization of the thiolate/disulfide bond formation as OEMs in AZIBs. |
