Design And Study Of Lepidolite Solid Electrolyte

As a new type of secondary battery,solid state battery has higher energy density and excellent safety performance.However,solid electrolyte,as the core component of solid state battery,is faced with the problem that ionic conductivity,electrochemical stability and safety performance cannot be taken into account.Therefore,the study of ion conduction mechanism of solid electrolyte and the design and optimization of performance of solid electrolyte have become the key to the development of solid state battery.Based on the solid electrolyte additive lepidolite,the ion conduction mechanism of solid electrolyte was studied and the performance of solid electrolyte were optimized by combining molecular simulation and experiment.Specific research contents are as follows:（1）we established the structure model of lepidolite,analyzed the energy band structure and surface electrostatic potential of lepidolite,and simulated the conduction path of lithium ions in lepidolite through molecular dynamics.The results showed that the larger negative potential areas on the surface of lepidolite could provide binding sites for lithium ions and promote the conduction of lithium ions.（2）Based on the results of molecular simulation,we put forward a kind of method to improve the ion conductivity of polyethylene oxide（PEO）composite electrolyte with lepidolite:utilizing the characteristic that lepidolite would be horizontal arrangement after drying in polymer（PEO）solution,composite solid electrolyte containing vertically arranged lepidolite were obtained by means of"lamination,cold pressing and slicing"method.Compared with the horizontal arrangement,the ionic conductivity of the composite electrolyte with vertically arranged lepidolite was increased by 3～4 times,and it also showed good mechanical properties.The solid-state electrolyte was further utilized for the assembly of a lithium metal battery,which exhibited higher capacity(130 m Ah g^-1)and maintained capacity of 121.6 m Ah g^-1 after 100 cycles.（3）Although the above method can effectively improve the ionic conductivity of PEO composite electrolyte,it is still unable to meet the working conditions of solid electrolyte at room temperature.Therefore,we prepared plasticized polytetrafluoroethylene（PVDF）solid electrolyte containing lepidolite,and compared the ionic conductivity and voltage window of the composite electrolyte with different plasticizer contents.The results showed that the composite electrolyte containing 13.63%plasticizer has relatively ideal ionic conductivity and electrochemical stability.Then,we studied the mechanism of ion conduction through theoretical calculations and experiments:lithium ions could migrate between polymer segments in the form of complex cluster ions.The solid state battery using this solid state electrolyte has good electrochemical performance at room temperature.