Preparation And Electrochemical Properties Of Polymer-Based Li₇La₃Zr₂O₁₂ Solid-State Electrolyte

Solid-state electrolytes are an important part of the solid-state lithium batteries with high power and energy density,long cycling life and desirable safety.Recently,the development of inorganic/polymer composite electrolytes provide a promising strategy in obtaining high performance solid electrolytes because of the combined virtues of both the inorganic and polymer electrolytes.These advantages are of great significance for the development of all-solid-state batteries.The garnet-type inorganic solid electrolytes have the advantages of high ionic conductivity and good stability,showing potential applications in lithium batteries.In this work,the there-dimensional?3D?porous garnet-type Li_6.28La₃Zr₂Al_0.24O₁₂?LLZAO?was used as a filler to enhance the electrochemical performances of PEO based electrolytes.The structure and performance of the obtained samples were characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?,thermogravimetric analysis?TGA?,electrochemical impedance spectroscopy?EIS?,linear sweep voltammetry?LSV?and charge-discharge test,etc.Some interesting results are listed as follows:?1?The 3D porous LLZAO ceramic network membrane was prepared by using clearnroom wiper as the template.The 3D LLZAO-PEO/LiClO₄ composite solid electrolytes was then obtained through immersing the ceramic membrane of LLZAO to the PEO/LiClO₄solution.The effect of different heat-treated temperatures on the crystal phase and morphology of LLZAO was investigated.The results implied that a good cubic 3D LLZAO network structure can be synthesized via heat treatment at 850 ^oC for 2 h.LLZAO-PEO/LiClO₄ composite electrolytes containing 27.8 wt%LLZAO exhibited the highest ionic conductivity of 2.25×10^-5 S·cm^-1 at 30 ^oC,which is 30.7 times higher than that of pure PEO/LiClO₄ electrolyte,indicating that the 3D LLZAO porous structure can effectively form continuous fast ion transport pathways and inhibit the crystallization of PEO.In addition,the all-solid-state Li|27.8 wt%LLZAO-PEO/LiClO₄|LiFePO₄?LFP?battery exhibited a high initial discharge specific capacity of 143.8 mAh·g^-1 and an outstanding cycling stability of 94.8%retention after 100 cycles.?2?The PEO/LiClO₄/Mxene?Ti₃C₂?composite electrolyte was prepared through modifying the PEO/LiClO₄ electrolytes with an appropriate amount of two-dimensional?2D?Ti₃C₂.Experimental results indicated that the PEO/LiClO₄ system with 5 wt%Ti₃C₂exhibited the highest ionic conductivity of 6.2×10^-5 S·cm^-1 at 30 ^oC,which is 80.3 times higher than that of pure PEO/LiClO₄ electrolyte,and 2.8 times higher than that of 27.8 wt%LLZAO-PEO/LiClO₄ composite electrolyte.The assembled all-solid-state LFP/Li battery based on the PEO/LiClO₄/5 wt%Ti₃C₂ electrolyte showed a high initial discharge specific capacity of 143.7 mAh·g^-1.The cycling stability of LFP/Li battery retained 89.4%of its original capacity after 100 cycles.Furthermore,the LLZAO-PEO/LiClO₄/5 wt%Ti₃C₂composite electrolyte was fabricated by immersing the ceramic membrane of LLZAO to the PEO/LiClO₄/5 wt%Ti₃C₂ solution.As a result,the 13.1 wt%LLZAO-PEO/LiClO₄/5 wt%Ti₃C₂ composite electrolyte showed the highest ionic conductivity of 3.21×10^-5 S·cm^-1 at30 ^oC,which is 1.4 times higher than that of 27.8 wt%LLZAO-PEO/LiClO₄ electrolyte.The all-solid-state LFP/Li battery based on the 13.1 wt%LLZAO-PEO/LiClO₄/5 wt%Ti₃C₂composite electrolyte showed an excellent initial discharge specific capacity of 150.0mAh·g^-1,which is superior to that of the PEO/LiClO₄/5 wt%Ti₃C₂ electrolyte based all-solid-state battery.An excellent cyclic stability with a high retention of 89.5%after 100cycles was simultaneously achieved.