A novel aqueous K 2 CO 3 electrolyte enables high-performance of FeS anodes in Ni-Fe batteries at both room and elevated temperatures

Abstract

Fe-based electrodes in conventional KOH electrolytes are prone to chemical corrosion and surface passivation, which cause progressive deterioration of active substances and a rapid decline in cycling stability. Herein, we propose a novel aqueous K2CO3 electrolyte that enables FeS to exhibit excellent electrochemical performance at both room and elevated temperatures when used as an anode material in Ni-Fe batteries. The FeS electrode in a 5.8M K2CO3 electrolyte delivers specific capacities of 590.0 mAh g⁻ 1 at 25 °C and 591.3 mAh g⁻ 1 at 80 °C at a current density of 300 mA g⁻ 1 , and retains capacity retention rates of 99.47 % and 99.88 % after 300 cycles, respectively. Even at a high current density of 1 A g⁻ 1 , the FeS electrode exhibits reversible capacity as high as 540.4 and 564.7 mAh g⁻ 1 at 25 and 80 °C, respectively.Ni-Fe batteries have long garnered extensive attention in the energy storage domain owing to their outstanding advantages, such as high safety, low cost and environmental friendliness [1- 3] . Current research on Ni-Fe batteries primarily focuses on the modification of Fe-based anode materials [4][5][6][7][8][9][10][11] . For instance, Zhang et al. [7] utilized a one-step chemical vapor deposition process to obtain Fe@C hybrid configurations. When employed as anode materials of Ni-Fe batteries, these configurations demonstrated a high delivered capacity of 405.2 mAh g⁻ 1 at a current density of 1 A g⁻ 1 . Li et al. [10] developed a threedimensional spindle-like α-Fe2O3 architecture via a solvothermal method followed by post-annealing. When assembled with CoP@Ni(OH)2 cathode, the device achieved a maximum areal capacity of 0.203 mAh cm⁻ 2 and a volumetric energy density of 81.0 mWh cm⁻ 3 .