| Garnet type solid state electrolyte Li7La3Zr2O12?LLZO?is a promising new generation solid state electrolyte for it has a high Li-ion electrical conductivity and excellent electrode reacting stability.In the LLZO solid state electrolyte field,it remains challenging to enhance the total Li-ion electrical conductivity and chemical stability of LLZO solid state electrolyte.This work investigated the effects of elements doping,powder preparation method and sintering process on Li-ion electrical conductivity of LLZO solid state electrolyte,we employed X-ray Diffraction technology,scanning electron microscope,energy dispersive spectrometer and electrochemical impedance spectroscopy etc a series of characterizing methods to discussed the reason of LLZO solid state electrolyte performance changing.LLZO powder were synthesized by solid state method and LLZO solid state electrolyte as the base samples were prepared by pressureless sintering.The Ga doping LLZO powder were synthesized by solid state method and Sol-Gel method respectively,then obtained Ga-LLZO samples by pressureless sintering at 1100°C 12h and 950°C 48 h.As the Ga element mole doping content increased from 0.15 to 0.45,the average grain sizes of samples increased from 14?m to 19?m,the total Li-ion conductivity of samples decreased from 1.54×10-5S?cm-11 to 9.31×10-6S?cm-1.when the Ga element mole doping content was 0.15,synthesized by Sol-Gel sample that possessed the highest Li-ion electrical conductivity 1.67×10-55 S?cm-1.Ga?Ba co-doping LLZO powder were synthesized by solid state method,the electrolyte samples were prepared by pressureless sintering and spark plasma sintering?SPS?.Discussed the effects of elements co-doping and sintering methods on total Li-ion conductivity of LLZO solid state electrolyte.When the Ga and Ba elements mole doping contents were both 0.15,the Li-ion conductivity of Ga?Ba co-doping LLZO solid state electrolyte synthesized by pressureless sintering was2.11×10-44 S?cm-11 that was higher Ga doping LLZO solid state electrolyte's,and lower than Ga?Ba co-doping LLZO solid state electrolyte synthesized by SPS was 2.35×10-4S?cm-1.As the Ba element mole doping content increasing from 0.05 to 0.35,the grains of the Ga?Ba co-doping LLZO solid state electrolyte contacted more tightness,grain average sizes declined firstly then rose again,the grain average sizes was lowest when the Ba mole doping content was 0.15.By the mean time,the grain fusion occurred that was grains contacted very compacted and grain boundary were vague.The Ba element as the sintering agent that could influence performance of the grain growth,and promote tighter grains bonding.In the same time,Ga element could stabilized cubic phase for LLZO and enhance Li-ion mobility,by the mean time,Ga element doping could cut down the Li content in the LLZO.Ba2+has a bigger ionic radius that could enlarge the bottleneck size of Li-ion transport path,and Ba doping could also supply the Li mole content lost in LLZO for Ga elements doping.Ga?Ba elements co-doping could improve the Li-ion conductivity of LLZO effectively. |
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