Impact of cation dopant on superstructure and anionic redox properties in Li-ion battery

Activating anionic redox (AR) activity in layered transition metal oxides has garnered significant attention due to their potential for additional capacitive contributions in Li ion batteries. However, the slow kinetics and poor stability of these materials have severely limited their practical applications. In this study, we synthesized (1-x) Li₂IrO₃·xLiNiO₂ (LINO) oxides via nickel (Ni) doping into lithium rich layered oxide Li₂IrO₃. The composition with 15 % Ni doping forms a honeycomb-ordered superstructure, resulting in enhanced capacity and cyclic stability. This improvement is attributed to the formation of the O1 phase, which undergoes reversible structural distortion and facilitates AR reactions. However, further increasing the Ni doping amount leads to Li/Ni mixing, preventing O1 phase formation and inhibiting AR activation at high potentials. Nevertheless, it is found that Ni doping cannot address the sluggish kinetics of AR due to its low charge transfer bandgap. This study offers valuable insights into designing high-performance lithium-ion battery cathodes that incorporate AR activity.