Design of a stable and voidless surface region by intensive subsurface zirconium doping for a high performance nickel-rich cathode in sodium-ion batteries

The subsurface Zr doping induced by diffusion in NaNi 0.8 Mn 0.2 O 2 is used for the Na-ion battery cathode. A uniform subsurface Zr-rich region aided by polyacrylic acid facilitates the primary particle growth of the cathode.