Solution-Synthesized SnSe1-xSx: Dual-Functional Materials with Enhanced Electrochemical Storage and Thermoelectric Performance.

The exploration of materials with multifunctional properties, such as energy harvesting and storage, is crucial in integrated energy devices and technologies. Herein, through an organic-free "soft chemical" solution method, a series of dual-functional SnSe1-xSx (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) nanoparticles have been developed toward high-performance electrochemical energy storage and thermoelectric conversion. Among the synthesized S-substituted SnSe, SnSe0.5S0.5 exhibits the highest rate capacity (546.1 mA h g-1 at 2 A g-1) and the best reversible capacity (556.2 mA h g-1 at 0.1 A g-1 after 100 cycles), which are much enhanced compared to those of SnSe. Density functional theory calculation confirms that the composition regulation by S substitution can lower the diffusion barrier of Li+, boost the diffusion rate of Li+, and in turn enhance the electrochemical kinetics, thus increasing the Li+ storage performance. Meanwhile, partially replacing Se by S decreases the lattice thermal conductivity, leading to an improved peak zT of 0.64 at 773 K in SnSe0.9S0.1, which is enhanced compared to the value for SnSe obtained at the same temperature. This study develops a combined composition tuning-nanostructuring approach for optimizing the electrochemical and thermoelectric performance of dual-functional SnSe.