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LIBs. In this context, Na-ion batteries (NIBs), because of the similar working principle and natural copiousness of sodium resources compared to LIBs, have attracted considerable attention and are recognized as cost-effective alternatives, especially for a large-scale energy storage system. [3,4] Among various cathode materials, Na x TMO 2 compounds (TM = transition metals such as Ni, Co, Mn, Fe, and Cr) have been early explored in the 1980s and have attracted enormous attention as promising candidates due to their superior discharge capacities and uncomplicated synthesis process. [5] According to the number of oxygen stacking sequences and the sites of the Na + environment (prismatic or octahedral), the layered oxides can be classified into P2, O3, P3, O2, and so on, [6] among which the former two oxides are the most concerned. [7] Although the P2-type cathodes have higher Na-ion conductivity and relatively better structural stability because of their wide planar tetrahedral center as Na + transport channel and low migration energy barrier, their capacity is somewhat low. [8][9][10][11] In comparison, the O3-type Na x TMO 2 with a relatively high sodium concentration (x > 0.8) yields a relatively higher capacity, while the migration of Na + needs to overcome a large energy barrier. [12] This is mainly caused by the obstructed diffusion pathway of Na + during insertion/extraction, which first passes through the tetrahedral site and then enters the two adjacent octahedral sites, resulting in complicated phase transitions. [13] As reported before, the O3-type layered Ni-rich NaNi x Co y Mn 1−x−y O 2 (x ≥ 0.6) cathodes for NIBs can enable relatively high capacity, but undergo likewise rapid capacity decay after long-term cycles, which is largely ascribed to the structural instability arised from multi-phase transitions. [14] With the mounting of Ni content, the O3-type cathodes achieve an ever-increasing capacity but compromise the structural stability and cycling retention meanwhile. [15] Beyond this, the O3-type Ni-rich cathodes are confronted with internal stress-induced mechanical damages (i.e., intergranular cracks) after deep cycles, which are triggered by the unceasing accumulation of lattice strain stemmingThe 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 ...

High voltage can cost‐effectively boost energy density of Ni‐rich cathodes based Li‐ion batteries (LIBs), but compromises their mechanical, electrochemical and thermal‐driven stability. Herein, a collaborative strategy (i.e., small single‐crystal design and hetero‐atom doping) is devised to construct a chemomechanically reliable small single‐crystal Mo‐doped LiNi0.6Co0.2Mn0.2O2 (SS‐MN6) operating stably under high voltage (≥4.5 V vs. Li/Li+). The substantially reduced particle size combined with Mo6+ doping absorbs accumulated localized stress to eradicate cracks formation, subdues the surface side reactions and lattice oxygen missing meanwhile, and improves thermal tolerance at highly delithiated state. Consequently, the SS‐MN6 based pouch cells are endowed with striking deep cycling stability and wide‐temperature‐tolerance capability. The contribution here provides a promising way to construct advanced cathodes with superb chemomechanical stability for next‐generation LIBs.

High voltage can cost‐effectively boost energy density of Ni‐rich cathodes based Li‐ion batteries (LIBs), but compromises their mechanical, electrochemical and thermal‐driven stability. Herein, a collaborative strategy (i.e., small single‐crystal design and hetero‐atom doping) is devised to construct a chemomechanically reliable small single‐crystal Mo‐doped LiNi0.6Co0.2Mn0.2O2 (SS‐MN6) operating stably under high voltage (≥4.5 V vs. Li/Li+). The substantially reduced particle size combined with Mo6+ doping absorbs accumulated localized stress to eradicate cracks formation, subdues the surface side reactions and lattice oxygen missing meanwhile, and improves thermal tolerance at highly delithiated state. Consequently, the SS‐MN6 based pouch cells are endowed with striking deep cycling stability and wide‐temperature‐tolerance capability. The contribution here provides a promising way to construct advanced cathodes with superb chemomechanical stability for next‐generation LIBs.