Carbon-Encapsulated Copper Sulfide Leading to Enhanced Thermoelectric Properties

Copper sulfide has been regarded as a promising thermoelectric material with relatively high performance and abundant resource. Large-scale synthesis and low-cost production of high-performance thermoelectric materials are keys to widespread application of thermoelectric technology. Here, Cu2-xS particles encapsulated in a thin carbon shell (19.7 g per batch) are fabricated by a scalable wet chemical method. They have a crystal phase transition from orthorhombic to tetragonal during high-temperature annealing and sintering. After phase transition, this composite (Cu2-xS@C) has a high electrical conductivity that is over 50% higher than that of pure Cu2-xS sample, originating from an increase in carrier concentration. With a low lattice thermal conductivity of 0.22 W m-1 K-1, a maximum thermoelectric figure of merit (ZT) of 1.04 at 773 K is achieved due to the new interface formation and superionic phase of Cu2-xS@C, which is the excellent thermoelectric performance in pure-phase copper sulfide via chemica...