Study On Lithium Titanium Aluminum Phosphatebased Soild-state Electrolyte

In recent years,with the demand for energy increasing,lithium-ion batteries have been widely used in human life.Therefore,there are more and more requirements for the performance of lithium batteries,especially in the aspect of safety.In recent years,all-solid-state batteries with solid-state electrolyte（SSE）have been rapidly developed due to their safety and high energy density.As an important part of all-solid-state batteries,the solid electrolytes with high ionic conductivity,good safety,high stability,and high mechanical strength have received widespread attention.Lithium titanium aluminum phosphate（LATP）has the characteristics of simple synthesis method and low cost,which is very prominent among various solid electrolytes.However,the ionic conductivity of LATP is relatively low(0.1 m S cm^-1),and LATP tends to be reduced by the lithium metal.So,the modification of LATP electrolyte is necessary.This thesis mainly aims to address the above-mentioned issues of LATP by modification and doping.The specific contents are as follows:（1）The ionic conductivities of most SSE are still not high enough for practical applications.A high-performance quasi-solid-state electrolyte composed of electrospinning LATP-PVDF-HFP nanofiber matrix and in-situ formed gel was studied.The prepared quasi-solid gel electrolyte shows a 3D porous network with significantly improved ionic conductivity up to 3.394 m S cm^-1.Meanwhile,the quasi-solid-state electrolyte exhibits a wider electrochemical window than that of the gel electrolyte,due to the synergistic effect between 3D network fiber and in-situ formed gel.The Li|CGE|Li Fe PO₄battery with this quasi-solid gel electrolyte shows good rate performance and cycle stability,and the discharge capacity reaches 146.6 m A h g^-1 at 2C.The capacity retention can still reach 97%at 0.5C after 300 cycles.This work provides a promising strategy for designing high-performance lithium metal batteries.（2）Li_1.3Al_0.3Ti_1.7（PO₄）₃（LATP）electrolyte shows poor contact with electrodes,serious side reactions with lithium metal and low ionic conductivity,which limit its practical application.To solve these problems chlorine（Cl）was doped into LATP.The prepared LATP-0.4Cl electrolyte shows a high ionic conductivity of 0.423 m S cm^-1.Neutron powder diffraction（NPD）results reavel that the change of Li⁺coordination environment after Cl doping has an effect on the ion diffusion path in the bulk LATP.The fabricated Li symmetric battery with the Cl-doped LATP exhibits long-term compatibility and electrochemical stability against lithium metal anode.The enhanced performance may be attributed to the in situ formed stable solid electrolyte interphase（SEI）layer.Meanwhile,comparing to LATP electrolyte,the Li|Li Fe PO₄（LFP）full battery with Cl doped LATP as electrolyte has an improved rate performance and cycling performance.This work demonstrates that Cl doping may be an effective approach for improving the performance of LATP electrolyte.