Structural and electrochemical behaviour of bilayer manganite LaSr2Mn2O6.96 cathode for all-solid-state fluoride ion batteries

In this study, we explore the potential of the RP-type bilayer manganite LaSr 2 Mn 2 O 6.96 as an intercalation-based cathode material for all-solid-state fluoride ion batteries (FIBs). Structural changes of LaSr 2 Mn 2 O 6.96 during fluoride intercalation and de-intercalation were analyzed via ex-situ X-ray diffraction, revealing that F − insertion induces the formation of three distinct tetragonal phases. To understand the complex behavior of these phases, we examined the changes in the Mn oxidation state and coordination environment using X-ray absorption spectroscopy and magnetic measurements. Under stack pressure (20 kN), electrochemical cycling of LaSr 2 Mn 2 O 6.96 in the potential range of 1 V to −1 V exhibited a continuous increase in specific capacity from capacity of ∼30 mAh g −1 to ∼ 68 mAh g −1 over 200 cycles, with ∼99% coulombic efficiency and no signs of capacity fading. This makes the bilayer manganite LaSr 2 Mn 2 O 6.96 a promising candidate for a cycling stable cathode for all-solid-state FIBs, especially under the application of stack pressure. This work demonstrates that the bilayer manganite LaSr 2 Mn 2 O 6.96 undergoes reversible structural and redox changes, enabling stable long-term cycling with high columbic efficiency in all solid-state fluoride ion batteries under stack pressure.