Highly durable and sustainable copper-iron-tin-sulphide (Cu₂FeSnS₄) anode for Li-ion batteries: effect of operating...

Operating temperatures considerably influence the energy storage mechanism of the anode of Li-ion batteries (LiBs). This effect must be comprehensively studied to facilitate the effective integration of LiBs in practical applications and battery management. In this study, we fabricated a novel anode material, i.e., copper-iron-tin-sulphide (Cu₂FeSnS₄, CFTS), and investigated the corresponding LiB performance at operating temperatures ranging from 10 °C to 55 °C. The CFTS anode exhibited a discharge capacity of 283.1 mA h g^-1 at room temperature (25 °C), which stabilized to 174.0 mA h g^-1 in repeated cycles tested at a current density of 0.1 A g^-1. The discharge capacity at higher operating temperatures, such as 40 °C and 55 °C, is found to be 209.3 and 230.0 mA h g^-1 respectively. In contrast, the discharge capacity decreased to 36.2 mA h g^-1 when the temperature decreased to 10 °C. Electrothermal impedance spectroscopy was performed to determine the rate of chemical reactions, mobility of active species, and change in internal resistance at different operating temperatures. In terms of the cycle life, CFTS exhibited outstanding cycling stability for more than 500 charge/discharge cycles, with a 146% capacity retention and more than 80% coulombic efficiency. The electrochemical investigation revealed that the charge storage in the CFTS anode is attributable to capacitive-type and diffusion-controlled mechanisms.