Study On Preparation And Lithium Storage Performance Of Three-dimensional Large Skeleton Carbon Materials

The anode electrode material is an important part of the lithium-ion battery,which is crucial to the performance of the entire battery device.At present,the widely used anode electrode material is graphitic carbon material,but this material has the inherent disadvantage of lower theoretical specific capacity.Therefore,how to increase the specific capacity of carbon materials has become a hot issue in the field of lithium-ion battery research.Among many carbon materials,graphene-like porous carbon materials exhibit excellent electrochemical performance due to their complex pore structure,good electrical conductivity and large specific surface area,and is considered to be one of the potential anode materials for lithium-ion batteries.Based on this,in this thesis,a carbon material with a three-dimensional large skeleton morphology structure is designed and prepared by regulating the synthesis mechanism,and on the basis of which element doping is studied,the structure-activity relationship between the morphology structure characteristics and the electrochemical properties of the material is revealed the structure-activity relationship between the morphology structure characteristics and the electrochemical properties of the material is revealed,The mechanism of the effect of element doping on the electrochemical behavior of materials is clarified.The main research contents and results of this paper are as follows:（1）Explore the best synthesis mechanism of the three-dimensional large skeleton structure.By changing the ratio of different raw materials and sintering temperature,the phases and properties of the obtained materials were characterized.The best synthesis mechanism of the three-dimensional large skeleton structure was explored as the ratio of PVPk30 and Fe（NO）₃·9H₂O is 1:1.5 and the sintering temperature is 750℃.Under this condition,a complete and uniform three-dimensional large skeleton structure is obtained,and there is in-situ N doping.The lithium-ion battery made of this material exhibits excellent electrochemical performance.（2）The three-dimensional large skeleton precursor material synthesized in（1）was pickled to prepare the three-dimensional large skeleton carbon material C@CS,and the physical properties and electrochemical mechanism of the material were studied.The research results show that the prepared C@CS retains the three-dimensional morphology of the precursor,the microstructure is porous,and the specific surface area is relatively large.Electrochemical studies have shown that the charge and discharge process of this material is mainly a pseudo-capacitance mechanism,and its specific capacity is much higher than that of traditional graphite materials.When the current density is 100 m A·g^-1,it can reach 1 652 m Ah·g^-1;and the remaining capacity can still reach 654.7 m Ah·g^-1 after200 cycles at the current density is 1 000 m A·g^-1;compared with the second cycle,the capacity remains reduced by 87.91%.（3）Phosphorus doped into C@CS successfully prepared phosphorus-doped three-dimensional large skeleton carbon material P-C@CS,and its morphology and structure were characterized and the electrochemical mechanism was studied.The research shows that the P-C@CS material still maintains the structure of the three-dimensional large skeleton,and the specific surface area and lattice spacing are larger than that of C@CS.In addition,the R_ct and R_sei of the electrode are lower than that of C@CS,and the specific capacity is significantly higher than that of C@CS material.At a current density of 100 m A·g^-1,it can reach 2 049.6 m Ah·g^-1.When the current density is1 000 m A·g^-1,it can still reach 667.2 m Ah·g^-1 after 200 cycles.Due to the increase in material defects,the cycle retention rate dropped slightly to 76.6%,but the capacity was still higher than C@CS.（4）Doping sulfur into C@CS successfully prepared the sulfur-doped three-dimensional large skeleton carbon material S-C@CS,and carried out the characterization of the morphology and structure and the study of electrochemical mechanism.The research shows that the S-C@CS material still maintains a good three-dimensional large skeleton structure,the material is porous,and the specific surface area and lattice spacing are further increased compared with P-C@CS.The R_ct and R_sei of the electrode are also lower,the polarization is greatly reduced,and the specific capacity is higher than that of C@CS and P-C@CS materials.At a current density of 100 m A·g^-1,it can reach 2 321 m Ah·g^-1.When the current density of 1 000 m A·g^-1,it can still reach820.4 m Ah·g^-1 after 200 cycles.Although S-C@CS has increased material defects,it still has an increased cycle retention rate of 88.39%.