The Preparation And Research Of PEO-LLZTO Solid-state Electrolyte And Solid-state Lithium Battery

PEO has the advantages of high flexibility and easy manufacture.Adding a certain amount of lithium salt,such as Li TFSI or Li Cl O₄,can improve the ionic conductivity of electrolyte.LLZTO inorganic solid electrolyte has high ionic conductivity and shear modulus,which can inhibit the growth of lithium dendrites.Li BOB is a coordination chelate,which can form a stable large?conjugated system with large molecular weight and stability.This structure weakens the interaction between anions and cations in Li BOB and reduces the crystallinity of PEO.In combination with these conditions,this paper carried out relevant research on PEO-LLZTO composite electrolyte:?1?In one of our studies,we synthesized flexible CPE membranes consisting of PEO matrix,lithium salt and LLZTO filler by simple solution casting method,and compared the effects of two lithium salts Li PF₆ and Li BOB on the properties of solid electrolyte.Solid-state lithium batteries were fabricated based on PEO/LLZTO/Li BOB?PLLB?and PEO/LLZTO/Li PF₆?PLLB?solid electrolytes for room temperature,respectively.The results show that Li Fe PO₄|PLLB|Li solid-state lithium battery has higher specific capacity and excellent cycle stability.For ionic conductivity,when the content of LLZTO is 40 wt.%at 20?,the ionic conductivity of PLLB electrolyte is the highest.The ionic electrochemical window of 5.2V.At the rates of 0.1C,0.2C,0.5C and 1.0C,the charging capacities of LFP|PLLB|Li lithium batteries are 165.9,150.1,137.9 and 107.2 m Ah g^-1 at room temperature,respectively.At 0.1C,the capacity retention rate was 84.6%after 100cycles.As an illustration,both theoretical calculation and experimental analysis confirm that PEO/LLZTO/Li BOB electrolyte membrane has good electrochemical stability as the electrolyte of solid-state lithium-ion batteries,and the batteries can provide high initial discharge capacity and good cyclic stability at room temperature,which indicates that PEO/LLZTO/Li BOB electrolyte membrane has good application prospects.?2?In our second work,we designed a novel asymmetric double-layer solid electrolyte structure with rigidity and flexibility.The electrolyte has the following characteristics:?a?the thin and dense bottom layer is a rigid barrier with high elastic modulus,which can effectively separate electrodes and electrolytes and prevent the penetration of lithium dendrites;?b?the upper flexible polymer layer supports the thinner dense layer;?c?the interface between the dense layer and the polymer layer is well integrated,with good mechanical integrity and continuous ion transport.Benefiting from the barrier of LLZTO layer to lithium dendrite penetration and the slight tension of lithium/polymer interface to inhibit dendrite nucleation,this excellent asymmetric solid electrolyte provides a flat plating/stripping voltage distribution and a stable dendrite-free lithium cycle?over 2000 hours?,thus significantly improving the cycle life and safety of lithium batteries.In addition,the ASE solid-state Li Fe PO₄|ASE|Li battery can provide a high initial discharge capacity of 155.1 m Ah g^-1 at 0.2C.It has a high capacity retention rate of 90.2%in at least 200 cycles without short circuit and ultra-high coulomb efficiency of 99.8%.This is due to the excellent lithium/electrolyte interface and the reduction of internal and interface resistance due to the unique asymmetric double-layer structure.In addition,with 4.3V Li Co O₂/Li batteries,all-solid-state lithium batteries have a specific capacity of more than 130 m Ah g^-1 and good cycle performance.This work will provide a clever solution for the construction of solid electrolyte with rigidity and flexibility for lithium metal batteries.