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- Na_2/3 Li_1/6 Co_1/6 Mn_2/3 O₂ 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.