Preparation And Properties Of Li_1.25Al_0.25Zr_1.75（PO₄）₃-PEO Composite Solid-state Electrolyte

In recent years,all solid-state batteries have received extensive research and attention due to their advantages such as high theoretical capacity,wide voltage range,and high safety.Polyethylene oxide（PEO）has a high degree of EO molecular chain flexibility and high dielectric constant,making it an ideal solid electrolyte material.However,the high crystallinity,low ionic conductivity(10^-6-10^-7S/cm),and low electrochemical window of PEO at room temperature severely limit its application.Therefore,this study combines Li_1.25Al_0.25Zr_1.75（PO₄）₃（LAZP）with PEO to construct a composite solid electrolyte,improving the ion conductivity,electrochemical window,and charge discharge cycle stability of the electrolyte.Firstly,this study optimized the positive electrode by adjusting the ratio of super P to Li Fe PO4.It was found that when the mass ratio of Li Fe PO₄to Super P was 7:1,the positive electrode had the best electrochemical performance.In addition,the appropriate addition of PEO based electrolytes and multi walled carbon nanotubes further enhanced the ion and electron conductivity inside the positive electrode,and the ion diffusion coefficient increased by nearly four times(5.05×10^-14cm²/s),with a discharge specific capacity of 152 m Ah/g at 2C magnification,which is twice that of the positive electrode without PEO based electrolyte.Secondly,this study prepared a solid electrolyte thin film composed of LAZP nanoparticles and PEO,and investigated the performance of composite electrolyte materials with different mass ratios of LAZP to PEO.Among them,LAZP has the best electrochemical performance when it accounts for 20wt%with a lithium ion migration number of 0.44,this composite electrolyte has lower interface impedance and polarization compared to pure PEO electrolyte,and a higher electrochemical window（4.6 V）.The all solid-state battery assembled with modified composite positive electrodes has a discharge specific capacity of 152 m Ah/g at a 2C rate at60℃.After 200 cycles at a 1C rate,the capacity retention rate remains 93.5%.Finally,the 3D ceramic skeleton Li_1.25Al_0.25Zr_1.75（PO₄）₃-PEO composite electrolyte was prepared using sponge template method and impregnation method.It has good interface stability and electrochemical performance,and the modified composite positive electrode assembly of the all solid-state battery still has a capacity retention rate of 95%after 1000 cycles at a rate of 0.5C.After 1300 cycles at 1C magnification,the capacity retention rate remains at 93%.