Research On Solid-state Batteries Based On Metal Lithium Anode

In recent years,lithium-ion battery is the most widely used electrical energy storage device that has been developed by leaps and bounds.However,the frequently reported battery fire incidents have caused people to worry about battery safety.On the other hand,the metal lithium anode has a relatively high theoretical specific capacity and a very low electrochemical potential,and is one of the ideal anode materials for lithium-ion batteries.Due to problems such as the formation of dead lithium and lithium dendrites in the lithium metal negative electrode during cycling,low-capacity layered graphite has to be used as the negative electrode in actual production applications.In order to solve the safety problem of lithium-ion batteries completely,the use of non-flammable solid electrolytes instead of combustible organic liquid electrolytes has become the research direction of the next generation of lithium-ion batteries.Garnet-type Li₇La₃Zr₂O₁₂ is a promising solid-state electrolyte for next-generation solidstate Li batteries.Typically,a metal ion doping in a stable cubic phase structure to improve ionic conductivity.Secondly,the high interface impedance between the electrolyte and metal lithium is also an important reason hindering the development of solid-state batteries.Poor solid-solid contacting relationship results in a non-uniform charge transfer exacerbated generating lithium dendrites.Therefore,build a stable electrode interface become the focus of current development of solid-state battery.In this thesis,a garnet-type Li₇La₃Zr₂O₁₂ solid electrolyte was prepared by the sol-gel method that the preparation process was explored and ion doping was carried out to improve the ion conductivity.The Li₇La₃Zr₂O₁₂ ceramic powder was prepared by the sol-gel method and calcined at700℃for 5 h to obtain Li₇La₃Zr₂O₁₂ with pure cubic garnet structure.The fine ionic conductivity of pellet has been sintered at 1100℃for 5 h.Excessive Li can inhibit the volatilization of lithium and the appropriate amount of lithium compensation is 5～15 wt%.The aging time of the sol does not change the composition of the phase.Al³⁺was used to dope Li sites to increase the concentration of lithium vacancies.The Li_6.7La₃Zr₂Al_0.1O₁₂ component has the highest ion conductivity,but it also hinders ion transport to a certain extent.Eu³⁺was used to dope La site and the ion conductivity is reduced,so the equivalent substitution of La position is not the ideal substitution method.W⁶⁺was used to dope Zr site,The Li_6.4La₃Zr_1.7W_0.3O₁₂ component has the highest ionic conductivity and the highest density,and its pellet has the highest degree of shrinkage in diameter.Assemble full battery with Li_6.7La₃Zr₂Al_0.1O₁₂ as solid electrolyte,the use of molten lithium can promote interface compatibility and the interface impedance is reduced from271000Ω·cm² to 3000Ω·cm².The solid-state full battery with Li Fe PO₄ as the cathode also has certain problems,the capacity decays faster at 0.1 C.When the current density increases to 0.5 C,the battery life is significantly shortened.