Preparation Of Lithium Garnet Solid-state Electrolytes And Their Application In All-solid-state Battery

Lithium ion battery is one of the most important electrochemical energy storage devices,which has the advantages of high energy density and long lifetime.However,lithium ion battery generally suffers from safety problems including leakage,corrosion and combustion due to the use of liquid electrolyte.All-solid-state lithium battery,using solid electrolyte instead of liquid electrolyte,could solve this issue totally for the traditional rechargeable lithium ion battery,hence has attracted more and more attention in recent years.At present,solid electrolyte materials with high ionic conductivities at room temperature and the preparation of ceramic electrolyte plate have become the research hotspot in this area.Cubic Li₇La₃Zr₂O₁₂（LLZO）,with high ionic conductivity,low interface resistance,excellent stability and electrochemical properties,has considered to be one of the most promising solid electrolytes applied in secondary lithium ion batteries.In this thesis,the processing conditions for pure cubic phase LLZO were investigated and optimized.The influence of forming and sintering methods on the properties of solid electrolyte membrane was explored.And conduction mechanism was studied with various characterization methods.The LLZO all-solid-state lithium batteries have been prepared through screen printing and sinter method,and the electrochemical properties have been investigated.The main points in this thesis are as follows:（1）Ball milling time has significant influence on the mixing degree of materials and the size of the particles.The optimum preparation condition is determined as ball milling for 8 h,and sintering at 1225 ^oC for 24 h.（2）The thickness of solid electrolyte plate is significantly affected by the preparation method.Samples prepared by hot pressing have dense microstructure,but too thick,while screen printing method is suitable for the preparation of thinner sample.Burying sintering process can improve the phase purity of solid electrolyte plates,avoid the evaporation of lithium,improve the heating uniformity of electrolyte plates,avoid cracking of solid electrolyte plates,and improve the stability of solid electrolyte plate while in preparation.Solid electrolyte plates prepared by the combination of screen printing and burying sintering have ideal thickness,with pure LLZO phase and dense microstructure.Their ion conductivities could meet the practical requirements.Furthermore,the plates are pure ionic conductors and have good chemical stability.（3）LLZO solid electrolyte is stable with lithium anode,and the battery containing LLZO solid electrolyte possesses superior cycling performance than traditional lithium ion battery using liquid electrolyte.Thus,this electrolyte material has great application potential in all-solid-state lithium battery.