Surficial Degradation of Jet-Milled Li6PS5Cl under Mild Temperature Heat-Treatment

All-solid-state batteries using sulfide solid electrolytes are considered a promising next-generation energy storage system. Especially, argyrodite-type Li_{&lt;span style="font-size:10.8333px"&gt;6&lt;/span&gt;}PS_{&lt;span style="font-size:10.8333px"&gt;5&lt;/span&gt;}Cl (LPSCl) is in spotlight for their good ionic conductivity and malleability. In electrode level, achieving efficient Li⁺ pathway with the maximized active material proportion and electrode mass loading is crucial for the high energy density. Thus, solid electrolytes with a small particle size is highly sought for. Here, we demonstrated a spiral jet mill process for refining LPSCl particle size, reducing the mean particle size (<i>D</i>₅₀) of LPSCl 39.9 μm to 1.9 μm where the ionic conductivity was decreased from 2.0 mS cm⁻¹ to 0.23 mS cm⁻¹. The post-annealing in a mild temperature (<i>T</i> &lt; 250 ^oC) led to the even more decreased ionic conductivity. Although the ionic conductivity was recovered when <i>T</i> &gt; 300 ^oC, these high temperature heat-treatment resulted in severe particle agglomeration. Spectroscopic study suggested that the particle surfaces were damaged during the jet-mill process and the irreversible sulfur losses occurred during the mild temperature annealing.