Preparation Of Coal-based Carbon Materials And Its Lithium/sodium Storage Properties

Today,social progress,economic develop rapidly.The demand for fossil energy has increased dramatically with the demand for population and industrial production.Although the current reserves of fossil energy are abundant,they still face the problem of depletion of resources.The development of new energy fields is a hot spot today.As a hot spot in new energy sources,the development of lithium-ion batteries has received great attention.In recent years,electric bicycles powered by lithium-ion batteries have developed rapidly,occupying a place in China's transportation,moreover,the new energy type electric vehicle is also powered by a high-power lithium-ion battery,and the development of portable equipment is also increasing the demand for lithium-ion batteries.It is the focus of scholars to explore electrode materials with large capacity,long life and good safety performance.Compared with lithium-ion batteries,sodiumion batteries have the similar working principle.The sodium is abundant in the earth's crust,and the successful commercialization of lithium-ion batteries has spurred the development of the sodium-ion battery industry.Based on the previous studies,this paper uses raw coal as the carbon source,controls the temperature and the amount of activator KOH as variables.Exploring the electrochemical properties of coal-based carbon materials obtained by heat treatment at 700 ° C,800 ° C,900 ° C,and 1100 ° C in sodium ion batteries and lithium ion batteries,respectively.The effects of carbon/base 1:1,1:3,1:5,1:6 on the morphology of coal-based carbon materials and the effects of electrochemical properties were also investigated.The main conclusions are as follows:(1)When investigating the influence of temperature,the non-graphitized(<2000 °C)heat treatment process,that is,the high temperature annealing at 700-1000 °C,the raw coal is processed,and the product is subjected to field emission scanning electron microscope and Raman spectroscopy tests show that the material is an amorphous carbon material with properties similar to those of hard carbon materials.When testing the electrochemical performance,it was found that the materials obtained by the four temperature treatments have good cycle stability.The reversible specific capacity of CT-700 assembled into lithium ion battery is stable at about 296 mAh/g,and the rate performance of CT-700 is better,the capacity retention after cycle is 95.7%;When CT-700 assembled into sodium ion battery The reversible specific capacity was stabilized at about 290 mAh/g,and the capacity retention rate was 87%.In summary,CT-700 has good electrochemical stability.(2)Using KOH as an activator,another carbon material was obtained by annealing at 800 °C.The surface of this material was uneven and porous,and the theoretical specific capacity was high.Test electrochemical performance found that CK-5 has the best electrochemical performance.In lithium-ion batteries,the reversible specific capacity of CK-5 is 362mAh/g,and the reversible specific capacity can reach 180mAh/g even at high current density.In sodium ion batteries,the reversible specific capacity of CK-5 can reach 298 mAh/g,reversible specific capacity at high current density of approximately 135 mAh/g.(3)Comparing the electrochemical performance of CK-5 with commercial graphite,it can be found that the comprehensive performance of CK-5 sodium ion battery is better than graphite.The above results illustrate the development prospects of coal resources as carbon materials.In addition to considering economics,this material also has a good performance in the electrochemical performance of sodium ion batteries.