Preparation And Performance Of The Solid Electrolyte

Secondary battery as an energy storage device is widely used in our daily life.First,traditional batteries cause pollution to the environment because of heavy metals.As people's environmental consciousness increase,so people put forward higher requirements on battery materials.Second,with the development of science and technology over the last decade,electronic products?such as laptops,mobile phones,etc?become more and more popular for convenience,which require higher capacity,smaller volume and more safety batteries.So it promotes the upgrade of batteries,from lead-acid battery and nickel-chromium battery to lithium battery and lithium ion battery,now solid polymer batteries are already used on the market.Compared with the polymer battery,the safety of the inorganic solid battery is higher,but it is undeveloped for its low ionic conductivity.Therefore,improving ionic conductivity of the solid electrolyte is the main task in the study of inorganic solid-state batteries.In this thesis,two kinds of Garnet-type cubic inorganic solid electrolyte as Li₅La₃Nb₂O₁₂ and Li₇La₃Zr₂O₁₂ were synthesized by molten-salt growth method.We found that the ionic conductivity of the inorganic electrolyte at room temperature is 2.52×10-8S/cm?3.25×10-7S/cm by ac impedance measurement.It is need to be improve.In the exploration experiment of doping modification with Al,we found that adding Al can improve the ionic conductivity of the Li₅La₃Nb₂O₁₂ and Li₇La₃Zr₂O₁₂ electrolyte.The test results show that the introduction of Al element has limited improvement in ion conduction performance.In the exploration experiment of doping modification with Ta,there was little impact on the ionic conductivity when adding Ta to Li₅La₃Nb₂O₁₂ electrolyte,and the ionic conductivity became lower when adding Ta to Li₇La₃Zr₂O₁₂ electrolyte.The preparation of the Garnet type electrolyte powders was formed by moulding and sintering with high temperature sintering and observed by SEM,when sintering the Garnet-type electrolyte powder made in this experiment in 1200? for 5 hours,the density of electrolyte wafer was lower.We synthesized one of the NASICON-type cubic as Na_1+xZr₂Si_xP_3-xO₁₂ which required a lower sintering temperature with the sol-gel method.We chose two kinds crystals,Na_2.5Zr₂Si_1.5P_1.5O₁₂?x=1.5?and Na3Zr2Si2PO12?x=2?.The prepared powder sintered at 1000? for 5 hours,the ionic conductivity of both NASICON-type electrolyte were 1.34× 10-6S/cm and 4.67×10-6S/cm.They are improved compared to Garnet-type electrolyte.It illustrated that the two Garnet-type electrolytes,Li₅La₃Nb₂O₁₂ and Li₇La₃Zr₂O₁₂,synthesized by molten-salt growth method require a higher sintering temperature or a longer sintering time.