Research On Controllable Prelithiation And Electrochemical Performance Of Carbon-based Anode Material

In lithium-ion energy storage devices,the Initial Coulomb Efficiency（ICE）of some carbon-based materials with high capacity is usually low,leading to the insufficient of lithium-ion in the battery system,which will affect the electrochemical performance of the devices.In order to compensate the extra loss of lithium-ion,the energy storage devices need to be prelithiated.Chemical prelithiation based on aromatic hydrocarbon organics has certain advantages compared with other prelithiation methods because of its molecular adjustability,advantages of prelithiation in liquid state and better safety.This thesis mainly focuses on the significance of the improvement of ICE for lithium-ion energy storage devices and the controllability adjustment of the chemical prelithiation for carbon base anode.The main research contents are as follows.Initially,the ICE of Lithium Ion Battery（LIB）and Lithium-Ion Capacitor（LIC）are increased to different degrees,respectively,which improves the cyclic stability of energy storage devices above 4%.At the same time,the ICE measured in half cell and full cell has been compared and analyzed,which solves the problem that the enhancement degree of ICE is different between half cell and full cell.Furthermore,the reaction of 4,4-dimethylbiphenyl（4,4-DMBP）and the change of the conductivity of the solution in the process of lithiation reaction has been analyzed.On this basis,the capacity of the LIB assembled by the hard carbon and Li Fe PO₄ can still be retained by 99.5%after 350 cycles by adjusting the parameters of chemical prelithiation.Finally,the relationship between the Lowest Unoccupied Molecular Orbital（LUMO）energy level and lithium embedding effect is obtained by calculating molecular orbital energy level and corresponding prelithiation experiment.And the adjustment of the effect of prelithiation in molecular structure is realized from the perspective of functional groups.Through the above studies,the controllable prelithiation for the carbon base anode is basically achieved.The mechanism of lithium preimplantation based on aromatic hydrocarbon organics has been explained,which is helpful for further research on chemical prelithiation at molecular structure level.