The energy transition is one of the main challenges that society faces today. A game-changing shift towards a sustainable energy system is required to achieve carbon neutrality by 2050, a central objective of the European Green Pact in line with the EU's commitment to global climate action under the Paris Agreement¹. This provides an impulse for greater sustainability in the energy sector based on the incorporation of renewable energy sources. However, their intermittency is not adjustable with energy demand, so there is a need to find high-efficiency energy storage systems, such as batteries and supercapacitors, that can supply the current electricity grid at times when renewable energy production is insufficient. On the other hand, as currently more than 60% of the energy produced is lost in the form of heat, thermoelectric systems are a promising solution as they can generate electricity from waste heat (thanks to the Seebeck effect)². As a consequence, it is necessary the development of new sustainable, efficient and inexpensive materials for their implementation in this energy systems.

Metal chalcogenides emerge as potential materials for energy storage and conversion applications due to their rich redox activity, their relatively low thermal conductivity and wide variety of structures. Specifically, tin chalcogenides, SnQ (Q=S,Se), present a layered structure with a large interlayer space that facilitates the diffusion and intercalation of ions between the layers³, being interesting for use as electrodes in new generation batteries (K-ion batteries). Besides, thanks to its low thermal conductivity, these phases can also be used as thermoelectric materials. Currently, one of the challenges in this field is to achieve figure of merit (zT) values similar to those of SnSe reported by Li- Dong Zhao et al.: zT of 2.6 along the b-axis at 923 K in single-crystal form⁴.

In this work, pure SnS_1-xSe_x (x=0, 0.1, 0.2, 1) polycrystalline phases have been synthesised in only 1 minute of reaction time by microwave-assisted hydrothermal synthesis. This “fast chemistry” method allowed the generation of randomly distributed tin vacancies in the crystal structure, as demonstrated by synchrotron X-ray diffraction. This phenomenon influences the physical properties of the synthesised compounds by modifying the concentration and mobility of the charge carriers⁵.

In this communication we will discuss in more detail the synthesis procedure, as well as the structural and microstructural characterisation of the aforementioned phases. In addition, the electrochemical and thermoelectric properties of these materials for their use in K-ion batteries and thermoelectric devices will be presented.
 
(1)         Paris Agreement to the United Nations Framework Convention on Climate Change; ESDN Report: Viena, 2015; pp 16–1104.
(2)         Black, et al., ACS Appl Energy Mater 2018, 1 (11), 5986–5992.
(3)         Jung, Y.; et al. Inorg Chem Front 2016, 3 (4), 452–463.
(4)         Zhao, L. D.; et al. Nature 2014 508:7496 2014, 508 (7496), 373–377.
(5)         González-Barrios, M. M.; et al. Ceram Int 2022, 48 (9), 12331–12341.