The Study On Li_6.4La₃Zr_1.4Ta_0.6O₁₂ Solid Electrolyte And The Interface Of Its Composite Positive Electrode

Recently,the solid electrolytes with non-flammable have attracted plenty of attention.The main reasons include:(1)Lithium metal can be used as a negative electrode to achieve high energy density;(2)The high shear modulus of solid electrolytes can suppress lithium dendrites to solve safety problem.For example,the low ionic conductivity of the solid electrolyte and the uneven owing to different processes.In addition,what limits the further development of the solid battery is that the high interface impedance.Inorganic oxide electrolytes are expected to become potential candidates owing to excellent thermal stability and chemical compatibility for solid-state lithium-ion batteries.Unfortunately,the Li6.4La3Zr1.4Ta0.6O12(LLZTO)ion conductivity prepared in the experiment is much lower than the theoretical value,because the ion conductivity is related to many factors,such as grain size,density and sintering process.Based on the above facts,our work aims to design oxide solid electrolyte LLZTO with different surface microstructures and internal tortuosity to study the effect of size effect on density,ionic conductivity and lithium dendrites.Specifically,we prepared oxide solid electrolytes by nano-scale,micro-scale and micro-nano mixed particles,combined with Nano-CT technology and electrochemical analysis technology.The experiment found that the large particles in the micro-nano mixed electrolyte are suppressed to a certain extent The abnormal growth of small particles effectively fills the gaps between large particles,the porosity of the electrolyte surface is reduced from 15% to 3% of the single particle size,and the ion conductivity is from 2.96× 10-5 S·cm-1 increased to 7.11× 10-5 S·cm-1,the corresponding critical current density increased from 75 ?A·cm-2 to 100 ?A·cm-2,which means that the ability to suppress lithium dendrites has increased.This design and conclusion may provide a simple and effective experimental idea for improving the ionic conductivity of solid electrolytes.The "point-to-point" contact between the solid electrolyte and the surface of the active material controls the interface ion diffusion and seriously affects the battery performance of the all-solid-state lithium ion battery.Here,we have designed a new microstructure of "open source lithium-saving" to simulate the ion transport mechanism when a fast ion conductor is introduced into the "secondary particles".Through synchrotron radiation three-dimensional reconstruction technology,combined with electrochemical data and TXM-XANES technology,fast ion conductor LLZTO is distributed inside(LFP@LLZTO)and outside(LFP+LLZTO)of "secondary particle" Li Fe PO4(LFP).The experiment found that after 30 cycles,the polarization voltage of LFP@LLZTO is less than half of LFP+LLZTO,indicating that the internal resistance of LFP@LLZTO is small.In addition,the discharge specific capacity of LFP+LLZTO is almost 0 m Ah·g-1 after 80 cycles,while LFP@LLZTO maintains a discharge specific capacity of 100 m Ah·g-1 after 200 cycles,and has excellent electrochemical stability.This design idea of introducing fast ion conductors during the in-situ synthesis of the secondary particles of the positive electrode will help to improve the electrochemical performance of the solid-state battery.