Exploring The Ion Transport Physics In Several Solid Electrolytes Through Microstructural Characteristics

Inorganic solid electrolytes have attracted more attention due to the good performance in safety and electrochemical stability.However,the low ionic conductivity in available materials still limits the development of solid electrolytes.Therefore,it is of great urgency to develop new solid electrolytes with high ionic conductivity to meet the increasing market requirement.Since a lot of basic questions about conductors are structural in nature,the ion transport properties of a material are closely related to its structural atomic morphology.In this dissertation,the crystal structure characteristics and ion transport properties of solid electrolytes Li₃PS₄ and Li₁₀GeP₂S₁₂ were investigated by the joint usage of geometric analysis and bond valance.The main research results are summurised as follows:1.The crystal structure charactoristics ofγ-,β-,α-Li₃PS₄ and Li₁₀GeP₂S₁₂ were systematically investigated.Based on the unified basic coordinate vector framework,three crystal structures of Li₃PS₄ are systematically analysed and compared.We analyzed the structures by disintegrating them into several small configurations to investigate which permutation may have the better performance in transport properties.The crystal structure of Li₁₀GeP₂S₁₂ was investigated,and the characteristics of the anion packing were obtained.The structural analysis indicates that the host structure of Li₁₀GeP₂S₁₂,that is S anion sublattice,is similar to a body-centered cubic framwork.2.With the structure characteristics of Li₃PS₄,the influence of the arrangement of PS₄ tetrahedron on ion transport was investigated.The structural analysis indicates that the variations of the position of P-ions lead the rearrangement of the host PS₄tetrahedron,affecting the diffusion positions of Li-ions and further enabling high Li⁺conductivity inβ-Li₃PS₄.The calculation results show that Li-ions ofγ-,β-andα-Li₃PS₄ are easier to migrate in the PS₄ layer while ion transports between interlayer are more difficult,and the interstitial sites are involved during the diffusion process.3.With the structure characteristics of Li₁₀GeP₂S₁₂,the influence of anion arrengement on ion transport was investigated.It turned out that,for Li₁₀GeP₂S_12,the closer the host anion is arranged to BCC packing,the easier Li⁺is to achieve three-dimensional transport.Furthermore,in order to find other solid electrolytes having the same structure characteristics with Li₁₀GeP₂S₁₂,a procedure for structural matching was developed.The anion arrangement characteristics of lithium-containing sulfides and oxides were obtained,as well as some other typical solid electrolytes,and the calculated results were summarised.