| All-solid-state batteries have higher safety performance than conventional lithium-ion batteries. As an important part of the all-solid-state lithium-ion batteries, the solid electrolyte is an important aspect of their research. Glass and glass-ceramic electrolytes in the system of Li2S-P2S5 have high lithium ion conductivity and good electrochemical stability. The preparation process is also very simple. So the electrolytes have a very good application prospect.This paper took Li2 S and P2S5 as main raw materials, prepared Li2S-P2S5 glass and glass-ceramic electrolytes by a high-energy ballmilling and subsequent heat-treatment method. This paper focused on the impact of Li2S-P2S5 glass forming process, the heat treatment temperature, the ratio of raw material composition, heat treatment time, electrolyte sheet molding process and doping conditions for solid electrolytes.80Li2S-20P2S5(mol%) glassy electrolytes were prepared by a high-energy ballmilling method. Kept the ball-materials ratio and milling rate unchanged, we explored the impact of milling time on the formation of the glassy state. The results showed that glassy material could be fully formed after 25 h milling. The milling process had an important influence on the phase species and ionic conductivity of the glass-ceramic electrolytes. Mechanical chemical reaction has happend in the system of 80Li2S-20P2S5(mol%) by a high-energy ballmilling method. Eventually, 80Li2S-20P2S5(mol%) became a glassy sample. The glass network structure was mainly constituted by PS43- tetrahedral.The choice of heat treatment temperature had an important influence on crystal phase composition, microstructure and ionic conductivity of Li2S-P2S5 glass-ceramic electrolytes. For a certain samples, species of crystalline phase were different at different heat treatment temperature. The ionic conductivity of the glass-ceramic electrolytes was also different. The high conductivity crystalline phases were Li7P3S11, Thio-LISICON Ⅱ analogs and Thio-LISICON Ⅲ analogues in the Li2S-P2S5 glass-ceramic electrolytes. Their production would increase the ionic conductivity of the glass-ceramic electrolytes. Low ionic conductivity crystalline phases were Li4P2S6、Li3PS4 and Li7PS6. Their production would reduce the ionic conductivity of the glass-ceramic.We explored the influence of raw material composition ratio on Li2S-P2S5 system solid electrolytes. The results showed that, the ionic conductivity of Li2S-P2S5 glass electrolytes increased with the increasing of Li2 S. The crystalline crystalline phase of the glass-ceramic electrolytes were also different at different ratio of the electrolytes and generated at different temperatures. The temperature which Appeared the highest ionic conductivity of the electrolytes were also different.At a certain heat-treatment temperature 320℃, we studied the effect of heat treatment time on 80Li2S-20P2S5(mol%) glass-ceramic electrolytes. The results showed that with the heat treatment time prolonged, crystal particles grew and their boundary impedance increased.Li2S-P2S5 glass-ceramic electrolytes were prepared by different molding methods. The results showed that solid electrolytes prepared by hot-pressing sintered contacted more closely and had a higher ionic conductivity, compared to the methods of first heat-treatment then cold pressing or first cold pressing then heat-treatment.Finally, we studied the electrochemical stability and the stability for lithium electrode of Li2S-P2S5 solid electrolytes. The results showed that, Li2S-P2S5 electrolytes had good electrochemical stability and their electrochemical window were above 5V. Well, there were some small oxidation peaks in the anode region of 70Li2S-30P2S5 solid electrolytes. We presumed that it would be the oxidation process of S2-. The reaction could occur between the solid electrolytes and Li and a stable interface formed after some time. The stability of Li2S-P2S5 solid electrolytes and Li electrode remained to be further improved. |
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