Preparation And Electrochemical Performance Of Composite Solid-state Electrolyte Based On LATP

With the rapid development of digital products and the new energy automobile industry,people's requirements for lithium secondary batteries have gradually increased.Solid-state lithium batteries are attracting more attention owing to its high energy density and safety.As the core material of solid-state lithium batteries,designing and preparing solid-state electrolytes with high lithium-ion conductivity,low interface impedance,and excellent stability has been emerging as a research hotspot in LIB domain.Based on NASICON-style solid-state electrolyte Li1.3Al0.3Ti1.7(PO4)3(LATP),The influence of different factors on its lithium-ion conductivity was investigated and the interface modification was performed.Then cathode-supported composite solid-state electrolyte membrane was prepared with polyethylene oxide(PEO)as the polymer matrix and LATP as the inorganic filler,meanwhile its electrochemical performance was studied.The specific research results are as follows:(1)Starting from the preparation process of the LATP powder,using easy-to-scale solid-phase ball-milling method to prepare and control LATP powder,the effects of secondary ball-milling process,lithium salt doping amount,sintering temperature and time on the lithium-ion conductivity of LATP ceramic pellet were studied in detail.The results show that the secondary ball-milling process is beneficial to further reduce the particle size of LATP particles and improve the uniformity,which significantly improves the LATP lithium-ion conductivity.When the lithium salt was excess 20%,the ceramic pellet obtained pure phase and the highest lithium-ion conductivity.It was found that the grain boundary of LATP ceramic pellet obtained at 850? and 2 h was clear,with pure phase and fewer voids,the lithium-ion conductivity reached 2.91×10-4 S/cm.The composite solid-state electrolyte with sandwich structure was obtained by modifying the LATP ceramic pellet with PVCA-PEO double-sided polymer layer.After assembly into symmetrical Li battery,the test showed that the polarization voltage was stable at 0.054 V after cycling for 6000 min at 50? and a current density of 0.05 mA/cm2.LiFePO4/PVCA-LATP-PEO/Li battery at the current rate of 0.3 C achieves discharge capacity of 129 mAh/g and the capacity retention rate of 97.3%after 50 cycles at 50?.(2)Cathode-supported composite solid-state electrolyte membrane was prepared by solution cast method and PEO as the polymer matrix,LATP as the inorganic filler.Microscopic characterization and electrochemical tests show that the inorganic filler LATP significantly inhibits the crystallinity of PEO,which is beneficial to improve the lithium-ion conductivity of the electrolyte membrane.When doped with 15 wt.%LATP powder,the LATP filler is evenly and densely dispersed in the electrolyte membrane,and the electrochemical stability window is raised to 4.8 V,The lithium-ion conductivity of electrolyte membrane reached 7.50×10-6 S/cm and 3.46×10-4 S/cm respectively at 20? and 60?.The symmetrical Li battery was stably cycled at current density of 0.2 mA/cm2 for 400 h at 60?,and the polarization voltage was 0.05 V.The initial impedance of solid-state lithium battery assembled with cathode-supported solid-state electrolyte membrane is 69 ? at 60?,which is only about 1/2 of conventional solid-state lithium battery.LiFePO4-PEO-LATP/Li cell with capacities around 137.5 mAh/g after 120 cycles at 60? and 0.5 C,and the capacity retention rate was 93.66%,meanwhile shows good rate performance.