Ecofriendly and low-cost high-entropy sulfides with high thermal stability and ZT > 1 via entropy engineering and anion compensation

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The thermoelectric performance and thermal stability of high-entropy sulfides (Cu 7 Mg 2 Sn 2 ZnGeS 13 , Cu 5 MgSnZnSiS 9 , and Cu 7 Mg 2 Sn 2 ZnSiS 13 ) were studied and compared with copper-based monosulfides (Cu 2 S) and binary sulfides (Cu 12 Sb 4 S 13 ). High-entropy sulfides exhibit superior thermal stability, characterized by higher decomposition onset temperatures and minimal weight loss, maintaining their structural stability up to 750 ℃. Cu 7 Mg 2 Sn 2 ZnSiS 13 demonstrates a peak ZT of 0.52 at 500 ℃. Further optimization through sulfur compensation (Cu 7 Mg 2 Sn 2 ZnSiS 13.5 ) results in a 200 % improvement of the peak ZT value to 1.12 at 550 ℃, which is comparable to other pristine copper-based sulfides, while being more eco-friendly and cost-effective. Entropy engineering provides a new way to improve the inherent thermal and structural stability of sulfides and can also optimize their thermoelectric performance using non-toxic and earth abundant cation elements.