Research On Preparation Of High Desnity Solid Electrolyte Li_1.3Al_0.3Ti_1.7?PO₄?₃ And The Stability In Simulated Seawater Solution

Electrical power plays a pivotal role in the exploiting of ocean,lithium-seawater battery is a feasible design as undersea-battery.Inorganic solid electrolyte,which can isolate sea water and conduct ions,is the most important component of the battery,and a lot of works have been carried out in inorganic solid electrolyte.Benefiting from its good stability and high conductivity at room temperature,LATP(Li_1.3Al_0.3Ti_1.7?PO₄?₃)with NASICON structural type is a practical choice to serve as inorganic solid electrolyte.In this dissertation,high compactness LATP electrolyte film was fabricated,the properties and structural changes of LATP electrolyte film immersing in solutions have been carefully researched.In the dissertation,LTPA precursor powder was prepared by sol-gel method with lithium nitrate,aluminum nitrate,ammonium di-hydrogen phosphate and titanium isopropoxide as raw materials.Also,freeze drying was utilized to acquire LATP precursor powder with high phase purity and uniform particle size?with a diameter about 300 nm?.Furthermore,LATP biscuit film with large area and low thickness was prepared by pouring method,and roll-in process was utilized to increase the homogeneity in thickness of pristine film.Adding flux to the LATP is an effective step to improve the properties of the film in.The addition of Na₅P₃O₁₀0 flux can increase relative density of the LATP electrolyte film,which reaches to 98.65%.And adding Li₃PO₄ flux to the system is advantageous to the total ion conductivity,which rises to 1.05×10^-33 S·cm^-1.Following the sintering schedule,which increases temperature to 570?with 1?/min and keeps for 12h and followed by increasing temperature to 800?with 10?/min and keeps for 6h,LATP electrolyte film can acquire a high property.With the high property LATP electrolyte film,immersion experiment was carried out by immersing LATP electrolyte film in sodion solution and alkaline solution according to sea water environment,the properties and structural changes were researched during the experiment.According to the results,properties for LATP electrolyte film were decreased during immersion experiment in both two solutions.After immersing LATP electrolyte film in the NaCl solution,Li-ion was found in the solution and the concentration was increased with immersion time,simultaneously,concentration of sodion was dipped.The XRD test shows that film structure shifted to NaTi₂?PO₄?₃ crystalline phase gradually after immersed in the sodion solution.Sodion in the solution could replace Li-ion in the LATP crystal lattice thus destroy the film.And the phenomenon becomes obvious when solution concentration or immersion time increases.Also,the film starts to break up when solution concentration is higher than 0.05mol/L.When immersing in alkaline solutions,film density and ion concentration in solutions show different variation tendency in solutions with pH<12 and pH?12.However,bulk phase conductivity shows negligible changes and crystal boundary conductivity shows a increases-decreases-increases tendency when pH increases.