Achieving Stable Cycling Performance in a P2-Type Layered Oxide Cathode through a Synergic Li/Zn Doping for Sodium-Ion Batteries.

Abstract

It has been suggested that sodium layered transition metal oxides could potentially serve as excellent cathodes for sodium-ion batteries (SIBs) because of their appropriate operating potentials and high capacities. However, the growing reliance on energy requirements has necessitated a higher energy density of SIBs. It has been demonstrated that activating oxygen-related activities for SIBs is a viable method to improve energy density. Herein, we suggest applying the synergy of Li and Zn codoping to activate the anionic redox reactions (ARRs) and improve their reversibility in Na0.75Ni0.3Mn0.7O2. The dual ion doping alleviates the phase transition and inhibits the Na+/vacancy arrangements, consequently improving the rate capacity and cyclic stability. The Na0.75Li0.15Ni0.1Zn0.05Mn0.7O2 delivers a discharge capacity of 134 mA h g-1 and no significant capacity loss at 100 mA g-1 between 2 and 4.5 V after 200 cycles. More importantly, the density functional theory (DFT) calculation proves that the codoping strategy triggers more ARRs compared to single-element doping, thereby providing enhanced capacity. The codoping induced oxygen redox strategies will create a new path for rational design of cathodes to enhance the energy density for SIBs.