Tailoring crystallization protocols to boost ionic conductivity in Li7P3S11 solid electrolytes via controlled two-step thermal processing

Li₇P₃S₁₁ is considered one of the most promising sulfide-based solid electrolytes for all-solid-state lithium batteries (ASSLBs) however, its complex crystallization dynamics present challenges in achieving maximum ionic conductivity. In this work, a comprehensive thermal and kinetic study elucidates the crystallization behavior of amorphous Li 7 P 3 S 11, focusing on how controlled nucleation and growth dynamics governs its structure–property relationships. Non-isothermal differential scanning calorimetry (DSC) combined with Kissinger, Ozawa, Matusita, and local activation energy models reveals crystallization activation barriers (E a ≈ 230–280 kJ.mol −1 ), highlighting a thermally activated, multi-stage transformation mechanism. A two-step heat treatment protocol, consisting of nucleation at 180 °C for 30 min followed by crystallization at 250 °C, substantially improves structural coherence and microstructural homogeneity. This kinetic tailoring leads to superior electrochemical performance, with room-temperature ionic conductivity reaching 1.98 mS·cm −1 and a Li + diffusion activation energy barrier of 0.25 eV. Structural and morphological analyses performed using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) confirm that controlled nucleation promotes uniform crystallite formation. These findings demonstrate that nucleation engineering is an effective strategy for enhancing crystallization pathways and unlocking the full potential of Li 7 P 3 S 11 and related glass–ceramic electrolytes in next-generation ASSLBs.