Perovskite Type Li_3/8Sr_7/16Ta_3/4Zr_1/4O< Sub>3 Preparation Of Solid Electrolyte And Its Application In Diaphragm

Conventional lithium batteries with liquid electrolytes have potential safety hazards such as leakage,combustion and explosion under extreme conditions.All-solid-state batteries based on oxide ceramic electrolytes have become the hotspot of current research.A perovskite-type Li_3/8Sr_7/16Ta_3/4Zr_1/4O₃?LSTZ?electrolyte with good mechanical property and stability is one of the solid state electrolyte candidate materials for the next generation lithium battery.However,the ionic conductivity and density of LSTZ electrolytes prepared by conventional sintering are still limited,and there are few studies on the application of perovskite LSTZ.In this thesis,LSTZ solid electrolyte was selected as the main research subject.The specific studies are as follows.?1?The influence of particle size and polyvinyl-butyral?PVB?amount of LSTZ precursor powder in crystal structure,cross-sectional morphology,ionic conductivity and diameter shrinkage rate of the obtained LSTZ were investigated.Refine grains size is beneficial to increase the ionic conductivity and density of the samples for manually ground precursor powder.The higher surface energy precursor powder and shrinkage rates samples were obtained after planetary ball milling.But the ionic conductivity deceased slightly caused the introduction of impurity phase.The amount and size of pores in LSTZ samples increased with increase of PVB amount.Ionic conductivity and density increase first and then decrease.?2?High relative density and ionic conductivity LSTZ electrolyte was synthesized via hot-pressing?HP?sintering.The optimum hot press sintering process was determined by changing the sintering temperature and holding time.LSTZ pellet prepared at 1300 ^oC for 1 h by hot-pressing showed fewer pores,better grain contact,higher compressive strength and Li⁺conductivity than the pellets prepared by conventional sintering?CS?.The all-solid-state LiFePO₄/Li battery with LSTZ electrolyte showed a high coulombic efficiency,a small over-potential,and a long cycle life at 50 ^oC.Carbon was permeated into LSTZ samples during the hot-pressing process.The calcination treatment at 900 ^oC for 6 h can effectively remove the C element and reduce the electronic conductivity of the samples.But the Li⁺conductivity decreased slightly with the generation of unpurity phase after carbon removal.?3?The stability of LSTZ electrolyte in water and atmosphere was studied.The LSTZ/PP composite separator was prepared by water-coating method after dopamine?DOP?modification on the polypropylene?PP?separator and flotation LSTZ powder.The LSTZ/PP composite separator displays good thermal stability and strong hydrophilicity??=33^o?.Not only is the adhesion strong but the bond is firm between the LSTZ solid electrolyte coating layer and the PP separator substrate.So,the LSTZ/PP composite separator had a favorable mechanical stability.Meanwhile,the LSTZ/PP composite separator exhibits superior electrochemical performance compared to PP separator.The LSTZ coating layer can effectively inhibit the growth of lithium dendrites on the surface of the lithium metal anode,reduce the impedance and polarization of Li-Li and Li-Cu batteries,and improve the rate and cycle performance of LiFePO₄-Li battery.