Lithium/Sodium Storage Properties Of Organic Cathode Materials Phenyl Imine Benzoquinone

Lithium/sodium ion secondary batteries have been commercialized and widely used in portable devices and electric vehicles at the moment.However,inorganic cathode materials based on transition metals are expensive,difficult to recycle and pollute the environment.In contrast,the low price and green environmental protection of organic cathode materials have gradually attracted extensive attention from researchers.Among them,quinones have the advantages of fast kinetic rate,no limitation of reaction system and high specific capacity,which are expected to be produced and applied.Organic molecules are easy to dissolve in the traditional electrolyte.Through reasonable molecular design and structure regulation and the use of ionic liquid electrolyte,the problem of quinones dissolving can be effectively solved,so as to improve the cycling stability of the battery.In this paper,phenyl imine benzoquinone（PIBQ）was designed and synthesized.It was used as the cathode of lithium/sodium ion secondary battery to test its electrochemical performance,and the mechanism of lithium/sodium storage was revealed by combining various test methods.（1）PIBQ molecule was designed based on the structure of benzoquinone（BQ）active molecules.By Schiff base reaction,the two BQ units are connected by a benzene ring and two carbon-nitrogen double bonds.Compared with the characteristics of BQ easy sublimation at room temperature,PIBQ has more stable physical properties.As the cathode material of lithium/sodium-ion secondary batteries,the four carbonyl groups in the PIBQ structure are the active sites of charge and discharge,and the theoretical specific capacity is311 m Ah g^-1.（2）In the lithium-ion battery tests,the PIBQ positive electrode obtained a reversible capacity of 308 m Ah g^-1 in the electrolyte of 0.3 M Li TFSI-PY13TFSI,which reached 99%of the theoretical capacity.At 0.2 C,the discharge capacity was stable at 270 m Ah g^-1 after100 cycles,which was 52%higher than that in the traditional 1 M Li PF₆-EC/DMC electrolyte.PIBQ was tested at 2 C in 0.3 M Li TFSI-PY13TFSI ionic liquid electrolyte,the capacity retention rate was 64%after 2000 long cycles.（3）As the cathode material of sodium-ion battery,PIBQ has a discharge capacity of262 m Ah g^-1 after circulating 100 times in 0.3 M Na TFSI-PY13TFSI electrolyte at 0.2 C;In the rate performance test,the discharge capacity of PIBQ at 2 C is 138 m Ah g^-1,and even if returns to a current density of 0.1 C,it still has a reversible capacity of 270 m Ah g^-1.After the PIBQ at the same current density was cycled 20 times in the 1 M Na PF₆-EC/DMC electrolyte,the discharge capacity drastically reduced to 85 m Ah g^-1.