Unblocking Oxygen Charge Compensation for Stabilized High‐Voltage Structure in P2‐Type Sodium‐Ion Cathode

Abstract

Abstract Layered transition‐metal (TM) oxides are ideal hosts for Li+ charge carriers largely due to the occurrence of oxygen charge compensation that stabilizes the layered structure at high voltage. Hence, enabling charge compensation in sodium layered oxides is a fascinating task for extending the cycle life of sodium‐ion batteries. Herein a Ti/Mg co‐doping strategy for a model P2‐Na2/3Ni1/3Mn2/3O2 cathode material is put forward to activate charge compensation through highly hybridized O2pTM3d covalent bonds. In this way, the interlayer OO electrostatic repulsion is weakened upon deeply charging, which strongly affects the systematic total energy that transforms the striking P2–O2 interlayer contraction into a moderate solid‐solution‐type evolution. Accordingly, the cycling stability of the codoped cathode material is improved superiorly over the pristine sample. This study starts a perspective way of optimizing the sodium layered cathodes by rational structural design coupling electrochemical reactions, which can be extended to widespread battery researches.

Keywords

• high‐voltage structural stability
• in situ synchrotron characterizations
• layered transition‐metal oxide cathodes
• oxygen charge compensation
• sodium‐ion battery