Densification Of Carbon Materials And Their Electrochemical Properties For Energy Storage

The development and utilization of green energy has become a focus of widespread concern in the face of various threats such as environmental pollution and resource depletion.Supercapacitors and lithium-ion batteries,as chemical energy storage devices,are important components of green energy.Carbon materials are widely used as electrode materials for energy storage devices.However,their low bulk density and low volume capacity limit their wider application.Densification of carbon materials is an important method to solve this problem.Based on this,the aim of this paper is to conduct densification treatment for different carbon materials by wet pelletizing,so as to improve their volume specific capacities.On the basis of serial characterizations of the obtained carbon materials,the electrochemical properties of them as electrode materials are investigated.(1)The effect of densification treatment on the thermal oxidation of carbon black was studied using N330 as raw material.The morphology and structure of the products with different thermal oxidation time were investigated and their electrochemical properties were tested.The results showed that,with the extension of thermal oxidation time from 5.5h to 10.5h,the hollow structure of the sample increased gradually and the specific surface area increased from 114.2 m2g-1 to 670 m2g-1,and the crystallinity increased correspondingly.When the oxidized carbon black was applied as the electrode material of supercapacitor,at the current density of 2 A g-1,the specific capacity of 127.9 F g-1 is displayed.After 10000 cycles,the capacitance retention rate is still 80%.When the current density increases to 20 A g-1,the specific capacity of 125 F g-1 is still maintained,showing the good supercapacitor performance.(2)Densified carbon microspheres were prepared from acetylene black,onion-like carbon and flake graphite by wet pelletizing and further carbonization.The effects of granulation conditions(binder dosage,granulation water ratio,granulation time,etc.)on the density and morphology of carbon nicrospheres were investigated.The results showed that after densification,the tap density of acetylene black increases from 0.1g/cm3 to 0.14 g/cm3,and the particle size was between 0～30μm.The tap density of onion-like carbon increases from 0.53 g/cm3 to 0.71g/cm3 with the particle size distributed between 0～150 μm.The tap density of flake graphite increases from 0.53 g/cm3 to 0.75g/cm3,and the particle size was mainly distributed between 0～200 μm.The graphitization degree of onion-like carbon and graphite microspheres decrease slightly after granulation,but the crystal structure of graphite still remains.(3)Both the onion-like carbon and graphite before and after granulation were used as electrode materials for lithium-ion batteries to reveal their electrochemical properties.The results showed that,when the electrode material was onion-like carbon,the specific capacity of onion-like carbon before and after granulation are both 310 mAh/g at a current density of 50 mA/g,and the first cycle efficiency was 88%and 87%,respectively.After 80 cycles,the capacity retention rate was still above 98%.Due to the increases of tap density,the specific volumetric capacity increases from 170 mAh cm-3 to 245 mAh cm 3.When graphite as the electrode material,at the current density of 50 mA/g,the specific capacity of flake graphite and graphite microspheres are the same of 365 mAh/g,and the specific volumetric capacity was 203 mAh cm-3 and 292 mAh cm-3,respectively.After 80 cycles,the capacitance retention rate is above 95%at the current density of 50 mA/g.