Regulating Cation Interactions for Zero‐Strain and High‐Voltage P2‐type Na2/3Li1/6Co1/6Mn2/3O2 Layered Oxide Cathodes of Sodium‐Ion Batteries

Deep sodium extraction/insertion of sodium cathodes usually causes undesired Jahn–Teller distortion and phase transition, both of which will reduce structural stability and lead to poor long‐cycle reliability. Here we report a zero‐strain P2‐ Na2/3Li1/6Co1/6Mn2/3O2 cathode, in which the lithium/cobalt substitution contributes to reinforcing the host structure by reducing the Mn3+/Mn4+ redox, mitigating the Jahn–Teller distortion, and minimizing the lattice change. 94.5 % of Na+ in the unit structure can be reversibly cycled with a charge cut‐off voltage of 4.5 V (vs. Na+/Na). Impressively, a solid‐solution reaction without phase transitions is realized upon deep sodium (de)intercalation, which poses a minimal volume deviation of 0.53 %. It attains a high discharge capacity of 178 mAh g−1, a high energy density of 534 Wh kg−1, and excellent capacity retention of 95.8 % at 1 C after 250 cycles. An integrated strategy combining the cation redox regulation and cation interaction regulation was reported to address the Jahn–Teller distortion and phase transition issues existing in layered cathodes. Impressively, our proposed cathode realized excellent cycling stability with an extremely low strain change of 0.53 %, even under deep sodium extraction/insertion operation conditions.