Preparation Of Li₇La₃Zr₂O₁₂ Solid Electrolyte And Determination Of Its Related Metal Ion Content

The organic liquid electrolyte of traditional lithium-ion battery is prone to combution,explosion and leakage.But the inorganic solid electrolyte can make up for the above deficiencies.Among them,the garnet-type solid electrolyte has a wide electrochemical window and high security advantages.Therefore,it becomes a hot research.Li7La3Zr2O12（LLZO）garnet-type solid electrolyte with a good development prospects has a high ionic conductivity and density.In this paper,LLZO is prepared by solid-phase ball milling.In order to find out the optimum preparation conditions,the influence of the lithium source,sintering system and the molding pressure before sintering on LLZO is studied.On the basis of this,the influence of Ca²⁺ doping content and sintering system on its properties is studied.In addition,lanthanum and zirconium content of LLZO directly affect the solid electrolyte skeleton structure and Li⁺ transport channel,which affects the ion conductivity.Therefore,it is important to determine the metal ion content in LLZO.In this paper,in the coexisting solution of metal ions simulating LLZO,the content of each metal ion is measured by visible spectrophotometry for the first time.The method is simple,low cost and free separation.Experiment results show that:（1）The best LLZO ceramic sheet is prepared by 4MPa molding pressure and sintering at1000℃ for 15 h,and LiOH·H₂O is regared as the lithium source.The ionic conductivity is7.92×10^-7 S·cm^-1 and the activation energy is 0.30 eV.（2）After introducing Ca²⁺,Li_7+xLa_3-xCa_xZr₂O₁₂ ceramic sheet with good performance is obtained by sintering at 1000℃ for 6h.When x is 0.1,the ionic conductivity is 5.23 ×10^-7S·cm^-1 and the activation energy is 0.35 eV.（3）The Zr⁴⁺ content in mixed solution of Li⁺,La³⁺ and Zr⁴⁺ is determined byspectrophotometry with 2mol/L hydrochloric acid as solvent.The working curve equation for Zr⁴⁺ is A=0.10114c-0.00117,with a collelation coefficient 0.9992.The relationship of concentration and absorption for Zr⁴⁺ is linear in the range of 0.4².4 μg/mL and the recovery rate is between 98% and 101%.（4）The La³⁺ content in mixed solution of Li⁺,La³⁺ and Zr⁴⁺ is determined by spectrophotometry,and the mixture with volume ratio of H₂O₂:H₂O=1: 9 is regared as solvent.The working curve equation for La³⁺ is A=0.3969c+0.03954,with a collelation coefficient0.9991.The relationship of concentration and absorption for La³⁺ is linear in the range of0.2¹.6 μg/mL and the recovery rate is between 100% and 101%.（5）The Li⁺ content in mixed solution of Li⁺,La³⁺ and Zr⁴⁺ is determined by spectrophotometry with acetone and KOH as the solvent.The working curve equation for Li⁺is A=0.2169c+0.54498,with a collelation coefficient 0.9992.The relationship of concentration and absorption for Li⁺ is linear in the range of 0.2⁰.6 μg/mL and the recovery rate is between 98% and 102%.