Preparation And Performance Of LLTO Nano-array And Composite Polymer Electrolyte For Lithium Ion Battery

All-solid-state lithium batteries are superior to traditional lithium-ion batteries not only in safety but also in performance.Some new inorganic ceramic electrolytes have lithium ion conductivity that can even reach the level of liquid electrolytes at room temperature,but they still have the problem of large interface impedance and poor contact with electrodes.Although the ionic conductivity of the PEO-based polymer electrolyte is low at room temperature,it has higher interface stability with the electrodes.Organic-inorganic composite electrolytes combine their advantages:good interface contact and high ionic conductivity.Many efforts have been made to optimize the nanostructure of organic-inorganic composite electrolytes.Related research shows that when the inorganic filler in the composite electrolyte is fibrously filled on the polymer substrate and the direction is perpendicular to the battery poles,the composite electrolyte has an optimal composite structure at this time,under the condition of same mass percentage of inorganic filler.However,no related structure has been successfully prepared yet.In this paper,a vertically aligned Li_0.5La_0.5Ti O₃?LLTO?nanoarray material was synthesized using polycarbonate?Polycarbonate,PC?as a template,and electrospinning LLTO nanofibers and particles LLTO were prepared.By composing with PEO?Polyethylene oxide?-Li TFSI matrix and PVDF?polyvinylidene fluoride?-Li Cl O₄ matrix,the self-supporting flexible composite electrolytes with excellent performance were prepared.?1?The LLTO ceramic nanofiber array material was successfully prepared by the sol-gel-template method for the first time.The effect of the preparation process on the microscopic array morphology was explored by adjusting the pore size of the PC templates and the heat treatment process.The structural characteristics of the samples were characterized by XRD,SEM,TEM and other detection methods.X-ray diffraction analysis?XRD?shows that the LLTO nanofiber array material is a tetragonal perovskite structure LLTO with good crystallinity.Scanning electron microscope?SEM?and transmission electron microscope?TEM?analysis results show that the prepared sample is LLTO solid nanofiber array material.These nanofibers are substantially perpendicular to the substrate,and the angle between the partially inclined nanofibers and the vertical direction is less than 30°.The fiber diameter of the nanofiber array is mainly related to the hole diameter of the template.The LLTO nanoarray prepared with a template with a pore diameter of 0.22?m has a fiber diameter of about 170 nm,and at this time,the nanofibers are neatly arranged,uniform in size,and have the best morphology.?2?The LLTO nanofiber array was compounded with PEO and PVDF polymers,respectively,to prepare LLTO nanofiber composite PEO polymer electrolyte and LLTO nanofiber composite PVDF polymer electrolyte.Meanwhile,electrospinning LLTO composite PEO polymer Electrolyte,granular LLTO composite PEO polymer electrolyte and pure PEO polymer electrolyte were aslo prepared.When the PC template with a pore diameter of 0.22?m is used to prepare the LLTO nanofiber array,the lithium-ion conductivity of the organic-inorganic composite electrolyte is 5.63×10^-5 S cm^-1.Compared with the pure PEO polymer electrolyte(2.82×10^-6 S cm^-1)and granular LLTO composite PEO polymer electrolyte(1.32×10^-5 S cm^-1),the ionic conductivity at room temperature achieved 20 times and 4.3 times respectively,and the improvement effect was obvious.In addition,the oxidation decomposition voltage of this new organic-inorganic composite electrolyte can reach 5.5 V?vs.Li⁺/Li?.The analysis by XRD image and polarized light microscope confirmed that the crystallinity of the PEO matrix in the composite electrolyte was significantly lower than that of the pure PEO polymer electrolyte.Previously,there has been no work to prepare fast ion conductor long-fiber materials.Compared with granular LLTO composite PEO polymer electrolytes,organic-inorganic composite electrolytes with vertical LLTO nanofiber structure have brought significant electrochemical performance improvements and this has brought some new ideas to the related research of organic-inorganic composite electrolytes.