Date on Master's Thesis/Doctoral Dissertation

12-2018

Document Type

Master's Thesis

Degree Name

M.S.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, MS

Committee Chair

Wang, Hui

Committee Member

Quesada, Peter

Committee Member

Sathitsuksanoh, Noppadon

Author's Keywords

solid electrolyte; Li6PS5Cl; liquid synthesis

Abstract

Recently, much attention has been devoted to the development of solid electrolytes to be used in all-solid-state-batteries. One group of promising solid electrolyte (SE) materials are lithium argyrodites, a class of superconductors which are noted for their high ionic conductivities. In particular, halogen doping has been shown to increase both conductivity and stability. The majority of research has focused on material synthesis through solid state reactions, but a novel liquid synthesis method for the preparation of Cl-doped Li7PS6 solid electrolyte provides the advantages of a homogenous product and a rapid, economic synthesis. Here this thesis focuses on the liquid synthesis process in two parts: (1) examine the effect of Cl content on the structure and conductivity of Li5+xPS6 xClx solid electrolytes (1≤x≤3); (2) investigate the effects of the reaction process parameters (mixing time, mechanical agitation, temperature) on the structure and conductive properties of Li6PS5Cl. The results show that Li7PS4Cl2 (with 2 mols of chloride) achieved the highest ionic conductivity of at room temperature, as well as excellent stability with lithium metal up to 5 V. Beyond 2 mols of doped chloride the performance gets rapidly worse. The results also indicate that longer vi mixing time up to 5 hours yields a higher conductivity of 5 , but does not obviously affect the phase purity and grain size. Mechanical agitation also does not appear to affect the phase or conductivity, however, a high sintering temperature results in a negative effect on the electrochemical performance. These results provide insight and understanding into this new liquid synthesis process which will play a huge factor in the future of solid-state-battery technology.

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