| The inorganic garnet-type solid electrolyte has high temperature stability,a wide electrochemical window,and a high lithium ion conductivity.Compared with liquid electrolytes,its room temperature conductivity is lower but its assembled lithium-ion battery is safer and more reliable.Therefore,improving its room temperature conductivity and its solid-state battery performance is the future development trend of solid-state batteries.In this paper,Li6.3-2XCuxLa3Zr1.65W0.35O12(0?x?0.5)and Li5.6Cu0.35La3Zr1.65W0.35O12 were prepared by high-temperature solid-phase reaction method is a solid-state battery assembled with electrolyte,graphite,lithium iron phosphate,lithium manganate,nickel cobalt manganese(NMC532,NMC811)and lithium sheet.The preparation process of solid electrolyte doped Cu content,types of lithium salt,lithium salt content,pre-baking temperature,sintering temperature and buried powder and their stability in air were studied.AC impedance,X-ray diffraction,scanning electron microscopy,X-ray photoelectron spectroscopy,etc.were used to characterize the properties and structure of the prepared product.The cyclic performance of the solid-state battery was analyzed using a constant current charge and discharge test.The main conclusions are as follows:1)The preferred process conditions for preparing Li6.3-2xCuxLa3Zr1.65W0.35O12(0?x?0.5)are:x=0.35,Li2CO3 as a lithium salt with an excess of 10%,pre-fire temperature 900?,holding time 6 h,sintering temperature 1160?,holding time 12 h,buried powder 3 g the obtained solid electrolyte room temperature ion conductivity is 1.09×10-3 S cm-1,activation energy 0.26 eV,relative density is 96.89%,shrinkage rate is 8.15%.2)X-ray photoelectron spectroscopy analysis results show that the doping state of Cu in the prepared product is+2,and that of W doping is+6.X-ray diffraction analysis showed that the prepared Li5.6Cu0.35La3Zr1.65W0.35O12 sample had a pure cubic garnet structure with space group Ia3d.3)After Li5.6Cu0.35La3Zr1.65W0.35O12 was left in the air for three months,the conductivity dropped to 3.37×10-4 S cm-1,and Li2CO3 impurities were generated,but they did not transform into a tetragonal phase.4)The button batteries assembled using Li5.6Cu0.35La3Zr1.65W0.35O12 as the electrolyte all achieved cycling and did not change the lithium deintercalation method of graphite,lithium iron phosphate,spinel lithium manganate,and ternary materials.Among them,the discharge voltage platform of LFP|Li5.6Cu0.35La3Zr1.65W0.35O12|Li solid-state battery is 3.38 V,the first charge specific capacity is 160.8mA h g-1,the first discharge specific capacity is 147.6 mA h g-1,and the twenty-cycle discharge capacity is 148.5mA h g-1,the capacity retention rate after 20 cycle is 100.6%;the first Coulomb efficiency is 91.8%,and the 20th coulomb efficiency is 99.8%.NMC811|Li5.6Cu0.35La3Zr1.65W0.35O12|Li solid-state battery has a discharge voltage platform of 3.7 V,a first charge specific capacity of 229.1 mA h g-1,a first discharge specific capacity of 189.8 mA h g-1,and a 20th cycle discharge specific capacity of 174.0 mA h g-1,the capacity retention rate after 20 cycle is 91.7%;the first Coulomb efficiency is 82.9%,and the 20th cycle Coulomb efficiency is 99.7%.5)Innovations:No research has been reported on high-temperature solid-phase synthesis of Cu2+and W6+co-doped Li7La3Zr2O12 solid electrolytes and solid-state batteries. |
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