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

Abstract 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‐ Na 2/3 Li 1/6 Co 1/6 Mn 2/3 O 2 cathode, in which the lithium/cobalt substitution contributes to reinforcing the host structure by reducing the Mn 3+ /Mn 4+ 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.