The Performance Of Organic Cathode Material Calix [8] Quinone In Aqueous Zinc Ion Batteries

Aqueous Zn-ion batteries（AZIBs）with environmental protection,low cost and high safety,have gradually attracted the attention of scientific researchers,and become the research hotspot of secondary batteries at present,and occupy an increasingly important position in the field of electrochemical energy storage.Inorganic materials are characterized by high cost,difficult to recover,easy to dissolve,capacity attenuation and other deficiencies,while organic electrode materials are mostly composed of C,H,O,N,S and other elements,which are abundant and cheap and easy to obtain,and can be flexibly designed molecular structure,showing excellent electrochemical performance.In this paper,for the first time,a small organic molecule Calix[8]quinone（C8Q）composed of 8 p-benzoquinone units was used as the cathode material of AZIBs.Its electrochemical performance was tested and analyzed through the electrolytic liquid system with different anion structure(OTf^-,SO₄^2-)and different concentration ratio.The zinc storage mechanism of C8Q materials was studied by a series of ex-situ characterization methods.（1）In the ZnSO₄ electrolyte system,the initial specific discharge capacity of C8Q electrode reached 202 m Ah g^-1 after 1,500 cycles under the condition of 1 M low concentration electrolyte and 1 A g^-1 current density,and the discharge capacity was 94 m Ah g^-1.In the high concentration salt electrolyte system of 4 M,the content of free water molecules is greatly reduced,and the solvation effect of Zn²⁺is effectively inhibited.Under the current density of 1 A g^-1,the initial specific discharge capacity of C8Q electrode reaches227 m Ah g^-1,after 1,500 cycles,the discharge capacity is stable at 133 m Ah g^-1.The average coulomb efficiency is 99.99%.Even in 5 A g^-1 high current density,the battery can still stable 5000 cycles,specific capacity of 93 m Ah g^-1.In addition,by the characterization and analysis of the ex-situ FTIR,ex-situ XPS,and EDS elements of the C8Q electrodes under three different states of initial,charge and discharge,it was verified that C=O in the structure of C8Q was the electrochemical active site for zinc storage.（2）In high concentration electrolytic liquid system of 3 M Zn（OTf）₂,the initial capacity of C8Q electrode is 237 m Ah g^-1 at 0.1 A g^-1 current density.When the current density gradually increases to 5 A g^-1,10 A g^-1,and 15 A g^-1,The discharge capacities were still 147 m Ah g^-1,142 m Ah g^-1,and 138 m Ah g^-1,showing nearly equal reversible capacity and excellent rate performance.Even at 10 A g^-1 super current density,after 10000 cycles of the battery,the discharge capacity can be stable at 95 m Ah g^-1 and the coulomb efficiency is 100%.In 3 M Zn（OTf）₂ electrolytic liquid system,the Zinc-ion battery shows excellent cycle stability and outstanding rate performance.In addition,the pseudocapacitance test shows that the transmission of Zn²⁺is mainly controlled by the surface of the electrode material,and the battery exhibits rapid reaction kinetics.