Using High-Entropy Configuration Strategy to Design Na-Ion Layered Oxide Cathodes with Superior Electrochemical Performance and Thermal Stability

Na-ion layered oxide cathodes (Na_xTMO₂, TM = transition metal ion(s)), as an analogue of lithium layered oxide cathodes (such as LiCoO₂, LiNi_xCo_yMn_1-x-yO₂), have received growing attention with the development of Na-ion batteries. However, due to the larger Na⁺ radius and stronger Na⁺-Na⁺ electrostatic repulsion in NaO₂ slabs, some undesired phase transitions are observed in Na_xTMO₂. Herein, we report a high-entropy configuration strategy for Na_xTMO₂ cathode materials, in which multicomponent TMO₂ slabs with enlarged interlayer spacing help strengthen the whole skeleton structure of layered oxides through mitigating Jahn-Teller distortion, Na⁺/vacancy ordering, and lattice parameter changes. The strengthened skeleton structure with a modulated particle morphology dramatically improves the Na⁺ transport kinetics and suppresses intragranular fatigue cracks and TM dissolution, thus leading to highly improved performances. Furthermore, the elaborate high-entropy TMO₂ slabs enhance the TM-O bonding energy to restrain oxygen release and thermal runaway, benefiting for the improvement of thermal safety.