Study On The Electrochemical Performance Of Polycyclic Aromatic Hydrocarbons And Their Derivatives As Secondary Battery Anode Materials

Nowadays,with the shortage of fossil fuel resources,the arising of environmental problems and the growth of the electric vehicle market,people are increasingly demanding energy storage devices.Among the various secondary batteries,lithium-ion batteries（LIBs）have the advantages of high specific energy,high specific power,and fast response speed,but the scarcity of lithium resources cannot be solved.The chemical properties of sodium are similar to those of lithium,while its obvious advantages of abundant reserves,easy develo pment and low cost over lithium making sodium ion batteries（SIBs）considered to be powerful alternatives to LIBs.However,the anode materials currently used as SIBs are still facing problems such as poor cycling stability and sluggish diffusion kinetic.It is imperative to develop new sodium storage electrode materials to meet the requirements of high-energy and high-power energy storage devices.Herein this paper,HBC and its derivative HBC-OMe were efficiently prepared by "bottom-up" organic synthesis methods.They all showed excellent cycle stability and rate performance when used as anode materials in SIBs.A variety of characterization methods were used to disclose the microstructure and crystal structure of the target product HBC,including X-ray diffraction（XRD）,Scanning electron microscope（SEM）,Transmission electron microscope（TEM）and Raman,which displays sub-microsized aggregates with abundant pores and relatively large interlayers.Galvanicstatic charge and discharge（GCD）and Electrochemical impedance spectroscopy（EIS）tests were conducted at room temperature to evaluate the electrochemical performance of HBC.After long-term cycling as SIB anode material in half cell at the current density of 0.1 A g^-1 for 400 cycles,HBC delivers a specific capacity up to 326 m Ah g^-1,even higher than that of the initial cycle,demonstrating noteable cycling stability.The galvanicstatic step discharge-charge tests at various current rates were also performed for HBC.At a large current density of 5 A g^-1,its reversible charge specific capacity can be maintained at 83 m Ah g^-1,and when charged back at 0.1 A g^-1,the charge capacity can recover 96% of that in the initial cycle,well indicative of impressive rate capability.The prominent sodium storage performance of HBC can be related to the large-interlayers and its relatively abundant porous structure between sub-microsized primary particles that can facilliate sodium diffusion and induce the formation of favorable solid-electrolyte-interface（SEI）film keeping structural integrity,respectively.In addition,we also prepared HBC-OMe and utilized it as anode material of sodium ion battery.At the current rate of 0.1 A g^-1,HBC-OMe shows a reversible charge specific capacity of up to 365 m Ah g^-1,and the capacity delivered after 110 cycles of discharge-charge can still reach as high as 341 m Ah g^-1,with a capacity retention rate of 86%,showcasing decent cycling stability at the current rate of 1 A g^-1,the reversible capacity remains at 205 m Ah g^-1 with a capacity retention rate up to 85%,exhibiting noticeable rate performance.The degradation of reversible capacity can be ascr ibed to the overly accumulated gel polymer-like SEI film on the surface of HBC-OMe particles as reavealed by SEM,leading to the reduced sodioum storage sites and frustrated Na ion diffusion.