Dynamic Ag+-intercalation with AgSnSe2 nano-precipitates in Cl-doped polycrystalline SnSe2 toward ultra-high thermoelectric performance

摘要

Recently, thermoelectric lead-free selenides have attracted great attention due to their earth-abundant, low-cost and environment-friendly characteristics. Here we report a new strategy to simultaneously enhance the electronic transport properties and reduce the thermal conductivity of polycrystalline SnSe2. By combining weak van der Waals bonding with the mobile behavior of Ag+ ions, the carrier concentration is optimized over a wide temperature range, which can be attributed to the dynamic Ag+-intercalation into the van der Waals gap from the Ag+ ion reservoir AgSnSe2. On account of additional electrical bridges between interlayers contributed by the intercalated Ag+ ions and weak anisotropy, an exciting high power factor of up to approximate to 7.46 W cm(-1) K-2 at 789 K is achieved along the pressing direction. In addition, the thermal conductivity is simultaneously reduced to approximate to 0.57 W m(-1) K-1 at 789 K, owing to numerous line defects, phase interfaces, twin boundaries, dislocations and intercalated atomic layers generated after Ag introduction, as well as the anharmonic vibration of Ag+ ions. As a result, a record peak ZT of approximate to 1.03 at 789 K is realized along the pressing direction, which is approximate to 1.6 times larger than the highest reported value (0.63) of polycrystalline SnSe2 and even comparable to that of p-type polycrystalline SnSe. This study opens a new way to achieve ultra-high thermoelectric performance, especially in layered materials.