Polyphosphazene Based Inorganic-Organic Hybrid Cathode Containing Pyrene Tetraone Sides for Aqueous Zinc-Ion Batteries

Abstract

Aqueous rechargeable zinc-ion batteries (ARZBs) are intriguing for electrochemical energy storage applications because of their safety and cost-effectiveness. Regarding cathode materials, rapid development has been observed with the organic-based cathode materials that offer much higher structural integrity upon successive (de-)insertion of charge carries ions. Even though promising results demonstrated with organic electrodes, they still suffer from the short cycle-life due to their discharge products solubility in electrolyte. Herein, electrochemical performance and charge storage mechanism of the synthesized polyphosphazene-based inorganic-organic hybrid electrode containing pyrene-4,5,9,10-tetraone (PTO) redox active lateral group, poly[(bis(2-amino-4,5,9,10-pyrenetetraone)], abbreviated as (PPAPT), were investigated in ARZBs. The charge storage mechanism of PPAPT was examined by various ex-situ [Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS)] and in-situ [pH change with bromocresol green indicator and electrochemical quartz crystal microbalance (EQCM)] characterization techniques as well as computational density functional theory (DFT) revealing that the PPAPT electrode (de-)coordinates both zinc and proton. The electrode and its discharge product are insoluble in the electrolyte demonstrated by UV-vis analysis and exhibited a stable cycling performance with a discharge capacity of 125.4 mAh g(-1) after 1000 cycles at a current density of 10 C.