Study On Modification Of PEO-based Solid Electrolyte

Lithium-ion batteries are one of the most promising energy storage devices due to their high energy density,excellent cycle stability and light weight.Lithium-ion batteries are widely used in various portable electronic devices and electric vehicles.At present,commercial lithium-ion batteries generally use liquid electrolytes,but their safety problems are a hidden danger and are well known to the world.Polymer solid electrolytes have obvious advantages in terms of safety,flexibility,and energy density.They are expected to alleviate battery safety problems and increase the specific energy of batteries.They are the most promising electrolyte materials.However,the low conductivity and mechanical properties of polymer electrolytes greatly limit their use in batteries.The addition of suitable inorganic fillers and organic plasticizers is the primary means of increasing the electrical conductivity and mechanical properties of polymer electrolytes.In order to solve the problems of polymer electrolyte materials,a modified electrolyte with appropriate amount of organic plasticizer,inorganic particles and lithium perchlorate was prepared by using polyoxyethylene?PEO?as the matrix,and its electrochemical performance was studied.Content:?1?This paper combines the common organic plasticizer tributyl phosphate?TBP?with PEO-based polymer electrolyte.By adjusting the TBP content and the lithium salt concentration,a polymer electrolyte composite membrane with good properties was prepared: high mechanical strength?9.6 MPa?,room temperature conductivity of 5×10-5S·cm-1,and electrochemical stability window more than 5 V,and the electrolytes of lithium ion transference number is 0.62,which was more than three times higher than the ion mobility?0.19?of the electrolyte to which no TBP was added.On this basis,the effect of TBP on the dissociation of lithium salt in the polymer was investigated.Li/polymer composite electrolyte/Li solid-state battery was assembled,and it was found that the electrolyte has excellent stability and cycle performance for the lithium electrode.?2?The ionic conductivity and mechanical properties of the inorganic particle-modified electrolyte are added.We compared the effects of different rare earthoxides on their electrical conductivity and screened the rare earth metal oxide Yb₂O₃ for modification.A translucent composite polymer electrolyte Yb₂O₃-PEO-Li Cl O4-TBP?YTCPE?was prepared by casting.When the mass fraction of Yb₂O₃ is 1 %,the ionic conductivity of YTCPE reaches a maximum value of 2.8 × 10-4 S·cm-1 at 30 °C.Excessive Yb₂O₃ not only forms agglomeration but hinders the migration of Li+,but also forms part of Yb₂O₃ particles as the core nucleus,which restricts the migration of some Li+ and reduces the conductivity.The Yb₂O₃ particles are uniformly dispersed in the PEO matrix.When subjected to external force,Yb₂O₃ can disperse and transfer the stress very well,avoiding molecular chain breakage and enhancing the toughness of the PEO-based electrolyte.When the Yb₂O₃ mass fraction is 1 %,the modulus of elasticity is 15.17 MPa,which is about 57 % higher than that of the electrolyte without Yb₂O₃.