Energy storage study of trimetallic Cu2MSnS4 (M: Fe, Co, Ni) nanomaterials prepared by sequential crystallization method

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Renewable energy sources are cornerstone for a sustainable future. It is however necessary to develop effective energy storage methods to tap the unpredictable energy sources. High surface area materials with a narrow pore size distribution, variable oxidation states and good electronic conductivity are considered to be the best materials for charge storage applications. Transition metal sulfides are currently investigated as electrode materials for energy storage devices. In this work, we have synthesized Cu2MSnS4 (M: Fe, Co, Ni) by one pot solid state sequential crystallization method using thiourea complexes of Cu, Ni, Co and Sn. The final sulfide products are characterized by PXRD, SEM-EDX, Raman, UV–vis–NIR, and HRTEM techniques. The electrochemical charge storage activity of these materials has been investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and impedance spectroscopy (EIS). The quaternary sulfides show promising charge storage behavior. Electrochemical analyses reveal that incorporation of Ni instead of Fe and Co in Cu2MSnS4 lattice can simultaneously improve the charge transfer and ion diffusion, thereby increasing the charge storage performance. Among Cu2FeSnS4, Cu2CoSnS4 and Cu2NiSnS4 samples, Cu2NiSnS4 and Cu2CoSnS4 show specific capacitance value of 1496 and 950 F g−1, respectively at a current density of 1 A g−1, and achieved specific capacities of 161 and 107 mA h g−1, respectively at the same current density. Both Cu2NiSnS4 and Cu2CoSnS4 also exhibit excellent cyclic stability, retaining respectively 77% and 72% capacitance after 4000 cycles. A symmetric supercapacitor based on Cu2NiSnS4 was assembled and it delivered specific capacity of 58.3 mA h g−1 at 1 A g−1 and a high energy density of 7.5 W h kg−1 at power density of 513.6 W kg−1. The redox properties of different metal ions present in the quaternary sulfide nanoparticles are mainly responsible for faradaic charge storage in these quaternary sulfide materials.