Research On Cathode Design And Performance For Rechargeable Molten Salt Fe-air Battery

Rechargeable molten salt Fe-air batteries are expected to become the new generation energy storage battery because of its high energy density,low cost,high safety,environmentally friendly and many other characteristics.This paper proposed a new structured fin air cathode,which improved the service life of the air cathode by declining the operating temperature,adding BaCO₃ to the electrolyte,and optimizing the method of electrolyte formation.The charge-discharge cycle performance of the new structured air cathode was investigated by XRD,FE-SEM,EDS and electrochemical analysis test.The results of the research showed that the fins of the air cathode provided a high surface area as well as an open fin configuration which avoids air electrode flooding,and oxygen can access easily the reaction zone.The plate of the air electrode connected with the molten electrolyte interface while the fins are fully wetted with the molten salt electrolyte to form a very thin molten salt film,leading to a triple phase?gas-liquid-solid?interfacial boundary construct on the fins.The results of the CV test showed that the fin cathode has good activity of ORR oxygen reduction,facilitating to improve ORR dynamics.It was indicated by XRD and FE-SEM that Ni is oxidized in situ to well dispersed nickel oxide and Li doped nickel oxide inside the cell during cycling.The battery cycled stably at 500?C for 80 cycles with an average charging potential of ¹.20 V and average discharge potential of ¹.04 V.The highest coulombic efficiency reaches 93.4% to a 0.7 V discharge cutoff.Decrease in operating temperature should alleviate corrosion of the air cathode to some extent,but caused polarization of the charge-discharge,that is,charge voltage increased,and current efficiency decreased.The corrosion of the air cathode was reduced by adding a certain amount of BaCO₃ to electrolyte.The LiCl in KCl-LiCl-LiOH system was replaced with Li₂SO₄ and Li_0.87Na_0.63K_0.50CO₃ respectively.It was shown that LiCl in molten KCl-LiCl-LiOH electolyte should be critical factor of Ni air electrode corrosion.The nickel air electrode showed low corrosion rate in KCl-Li₂SO₄-LiOH,but kinetics of the air electrode reactions was impaired.It is suggested that molten KCl-LiNa KCO3-LiOH is one of the best candidate electrolytes for the iron molten air batteries with nickel air electrode,taking into account factors such as high stability of the electrode and the excelent cycling performance.The KCl-LiNa KCO3-LiOH battery cycled stably for 850 cycles with the highest coulombic efficiency of 98.6% and the highest voltage efficiency of 85.9%,which laid a solid foundation for the research of rechargeable molten salt Fe-air batteries.