Multi‐Level Modifications Enabling Chemomechanically Stable Ni‐Rich O3‐Layered Cathode toward Wide‐Temperature‐Tolerance Quasi‐Solid‐State Na‐Ion Batteries

Abstract The O3‐type Ni‐rich NaNi x Co y Mn 1− x − y O 2 ( x ≥ 0.6) oxides are regarded as one of the most promising cathodes for high‐capacity Na‐ion batteries (NIBs), however, they still suffer from severe structural/morphological degradation induced by complicated phase transitions, as well as sluggish de‐/sodiation kinetics. For this, a multi‐level structural/compositional modification strategy, including “core–shell” design, bulk heteroatom doping, and surface coating, is purposefully explored to construct an advanced NaNi 0.6 Co 0.2 Mn 0.2 O 2 cathode (denoted as T‐CSN6@A). The Ni‐rich core guarantees the high capacity, and the Mn‐rich surface region coupled with bulk Ti doping and surface Al 2 O 3 coating reinforces the structural stability. This well‐designed architecture not only effectively inhibits the bulk and sur‐/interface structural fractures caused by repeated lattice volume variations upon cycling, but also dramatically boosts the de‐/sodiated kinetics, thus resulting in high chemomechanical stability and improved electronic/ionic transport for efficient sodium storage. When utilized as a competitive cathode, the T‐CSN6@A‐based quasi‐solid‐state NIBs are endowed with remarkable wide‐temperature‐tolerance Na‐storage behaviors within practicable working temperatures from −20 to 50 °C, along with an attractive material‐level energy density of ≈255 Wh Kg −1 at 25 °C. The feasible modification here provides a new avenue for advanced O3‐type Ni‐rich cathodes toward large‐scale industrialization of next‐generation NIBs.