Preparation Of PEO-based Composite Solid-state Electrolyte And Its Performance Study Of All-solid-state Lithium Metal Batteries

As a new energy storage device,lithium-ion battery has outstanding advantages such as high energy conversion efficiency,free and controllable output power,no memory effect and environmental friendliness.Since Sony launched its first commercial rechargeable lithium-ion battery in 1991,lithium-ion batteries have already penetrated into various fields of economy and society,such as smart phones,UAVs,electric toothbrushes,new energy electric vehicles and power grid energy storage.At present,lithium-ion batteries use liquid organic electrolyte,which has safety risks such as liquid leakage,flammability and explosion.In the face of"mileage anxiety"and the challenge of power grid peak shaving and energy storage,its energy density is slightly insufficient.Solid state battery has the advantages of higher energy density,higher power density and longer cycle life.It has intrinsic material safety.It is the best way to solve the safety problem and energy density of lithium battery.PEO based solid electrolyte has good film-forming property,easy processing,wide application range and great development prospect.However,at room temperature,PEO has high crystallinity,low lithium ion conductivity and small lithium ion migration number,which can not be put into use.In view of the existing defects,combined with the theory and relevant research status,this paper uses the casting method to prepare PEO based polymer solid electrolyte.On this basis,the overall design is carried out from the composition and structure,and the polymer solid electrolyte is modified to obtain PEO based composite solid electrolyte.Physical characterization and electrochemical test were used to comprehensively explore the performance of the composite solid electrolyte.Finally,the composite solid electrolyte and metal lithium negative electrode were assembled into an all solid lithium metal battery for charge discharge cycle test.The specific experimental research contents,results and conclusions are as follows:(1)a new metal organic framework material MOFs was prepared by coprecipitation method.It was used as inert filler to composite with PEO,and the PEO based solid electrolyte of MOFs composite was prepared by tape casting method.The effects of different MOFs on the physical properties and lithium ion conductivity of the composite solid electrolyte were discussed.It was determined that when the content of MOFs was 20%,PEO based composite solid electrolyte had the lowest crystallinity and the highest conductivity,and its performance in stable electrochemical window and all solid state battery was significantly higher than that of unmodified pure PEO polymer electrolyte.(2)A garnet Li_6.4La₃Zr_1.6Ta_0.4O₁₂(LLZTO)inorganic solid electrolyte doped with Ta was synthesized by high temperature solid state sintering was compounded with PEO as an active filler.The results show that when 10wt%active filler is added,the electrochemical window of PEO based composite solid electrolyte reaches 4.9V,the ion migration number is 0.45 and the ion conductivity reaches 1.76×10^-5 S/cm at room temperature.Under the test condition of 60?,the ionic conductivity reaches 4.05×10^-4 S/cm.Finally,CPE10 and commercial Li Fe PO₄cathode are assembled into an all solid-state battery for charge discharge cycle test.The test results show that the all solid-state battery shows high specific capacity and high cycle stability under different current densities.(3)On the basis of the experiments in the first two chapters,taking non-woven fabric as the reinforced substrate,MOFs were grown in situ,ionic liquid was poured,and PEO solution containing llzto was further poured to obtain a composite solid electrolyte with 3D structure.The results of physical characterization show that the composite solid electrolyte has lower crystallinity and greater mechanical tensile strength.The electrochemical test results show that the lithium ion conductivity of the composite solid electrolyte with 3D structure at room temperature is 6.66×10^-5S/cm,the lithium ion migration number reaches 0.55,and has a wide electrochemical stability window of 5V.Finally,the composite solid-state electrolyte is assembled into an all solid-state lithium metal battery for charge and discharge test.The test results show that the composite solid-state electrolyte with 3D structure can adapt to lithium iron phosphate and high nickel ternary ncm811 cathode,showing excellent rate performance and cycle stability.