A Customized Strategy Realizes Stable Cycle of Large‐Capacity and High‐Voltage Layered Cathode for Sodium‐Ion Batteries

High-voltage P2-Na_0.67Ni_0.33Mn_0.67O₂ layered oxide cathode exhibits significant potential for sodium-ion batteries, owing to the elevated operating voltage and theoretical energy density beyond lithium iron phosphate, but the large-volume phase transition is the devil. Currently, this type cathode still suffers from stability-capacity trade-off dilemma. Herein, a concept of customized strategy via multiple rock-forming elements trace doping is presented to address the mentioned issue. The customized Mg-Al-Ti trace doped cathode maintains a notable capacity of 140.3 mAh g^-1 with an energy density approaching 500 Wh kg^-1, and shows good cycle stability, retaining 89.0 % of its capacity after 50 cycles at 0.1 C. Additionally, the full cell, paired with a hard carbon anode, achieves an advanced energy density of 303.3 Wh kg^-1. The multiple characterizations reveal the failure mechanism of contrast sample involving severe intragranular cracks coupled with layer to rock salt transformation, which reduces active substance and increases charge transfer resistance. The doped sample with increased sliding energy barrier well suppresses this phenomenon. Impressively, the customized strategy can be extended to Mg-Fe-Ti system. This research provides a novel concept for the design of high energy sodium-ion cathode.