The Preparation And Application Of Cu, Sm（Cr） Doped Li₇La₃Zr₂O₁₂ Solid Electrolyte

Garnet-type Li7La3Zr2O12 solid electrolyte have attracted considerable attentions based on good air stability and high ionic conductivity at room temperature,it can solve the safety problems caused by liquid electrolytes and become one of the most widely studied solid electrolytes.In this study,Cu,Sm(Cr)doped Li7La32r2O12 solid electrolytes were prepared by high temperature solid-state method.The effects of element doping content,lithium salt type,lithium salt content,presintering temperature and sintering temperature on the preparation of solid electrolytes were investigated.X-ray diffraction(XRD),Scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and AC impedance(EIS)were used for characterization,respectively.The prepared solid electrolytes were assembled to form a solid-state lithium-ion battery with graphite negative electrode and lithium ion phosphate cathode,respectively.The main results are as follows:1)The preparation of Li6.3+xCu0.35La3Zr2-xSmxO12(0<x<0.22)solid electrolyte.When x=0.1,presintering temperature of 900℃,sintering temperature of 1160℃.The ionic conductivity of the prepared Li6.4Cu0.35La32r1.9Sm0.1O12 at room temperature is 1.51×10-3 S·cm-1,the relative density and shrinkage are 96.4%and 9.5%,activation energy is 0.23 eV.The XRD analysis results shows that Li6.4Cuo.35La32r1.9Sm0.1O12 is the cubic phase,the SEM results show that the grains are compact with no grain boundaries,and the XPS analysis results shows that the doping state of Cu and Sm in Li6.4Cu0.35La32r1.9Smo.1O12 is+2 and+3,respectively.After Li6.4Cu0.35La3Zn.9Sm0.1O12 was placed in air for one month,the conductivity decreased to 3.85×10-4 S·cm-1,and three months later,the conductivity decreased to 1.54×10-4S·cm-1.2)The discharge specific capacity of C|Li6.4Cu0.35La32r1.9Sm0.1O12|Li solid-state batteries for the first time is 540.3 mAh·g-1,the first coulomb efficiency is 92.68%,the discharge specific capacity of 30 th cycles is 327.8 mAh·g-1,the coulomb efficiency is 98.58%.The discharge specific capacity of LFP|Li6.4Cu0.35La32r1.9Sm0.1O12|Li solid-state batteries for the first time is 155.5 mAh·g-1,the first coulomb efficiency is 86.68%,and the discharge specific capacity of 30 th cycles is 136.1 mAh·g-1,the coulomb efficiency is 100.44%.3)The preparation of Li6.3+yCu0.35La3Zr2-yCryO12(0≤y≤0.30)solid electrolyte.When y=0.1,Li2CO3 is lithium salt(excess 10 wt%),presintering temperature of 900,sintering temperature of 1160℃.The ionic conductivity of the prepared Li6.4Cu0.35La32r1.9Cr0.1O12 at room temperature is 1.31×10-3 S·cm-1,the relative density and shrinkage are 94.8%and 7.7%,activation energy is 0.25 eV.The XRD analysis results shows that Li6.4Cu0.35La3Zr1.9Cr0.1O12 is the cubic phase,the SEM results show that the grains are compact with no grain boundaries,and the XPS analysis results shows that the doping state of Cu and Cr in Li6.4Cu0.35La3Zr1.9Cr0.1O12 is+2 and+3,respectively.After Li6.4Cu0.35La32r1.9Cr0.1O12 was placed in air for one month,the conductivity decreased to 5.11×10-4 S·cm-1,and three months later,the conductivity decreased to 3.16×10-4 S·cm-1.4)The discharge specific capacity of C|Li6.4Cu0.35La3Zr1.9Cr0.1O12|Li solid-state batteries for the first time is 455.5 mAh·g-1,the first coulomb efficiency is 85.8%,and the discharge specific capacity of 30 cycles is 347.1 mAh·g-1,the coulomb efficiency is 98.88%.The discharge specific capacity of LFP|Li6.4Cu0.35La32r1.9Cr0.1O12|Li for the first time is 153.9 mAh·g-1,the coulomb efficiency is 97.77%,and the discharge specific capacity of 30 cycles is 141.6 mAh·g-1,the coulomb efficiency is 96.68%,the battery still has good charge and discharge ability after 100 cycles.