Enabling Moisture Stability and Enhanced Cycling via Zn-Doping in High-Entropy Configuration O3-Type Sodium Ion Battery Cathodes

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High Resolution Image Download MS PowerPoint Slide High-entropy layered oxides (HELOs) with the formula Na 0.94 Ca 0.03 Fe 0.2 Mn 0.3 Cu 0.08 Ni 0.26 Ti 0.16 −x Zn x O 2 (0 ≤ x ≤ 0.08) were synthesized via a scalable all-dry method using earth-abundant elements. Incorporating Zn 2+ into the metal slabs was found to effectively mitigate the Jahn–Teller distortion associated with high-spin Mn 3+ ( t 2g 3 e g 1 ), strengthen structural integrity, and result in a depth-dependent valence profile in which higher Mn and Ni oxidation states are enriched at the surface, resulting in excellent stability towards air exposure and direct water immersion. In full coin cells paired with hard carbon, the x = 0.05 composition delivers an exceptional energy density of 272.4 Wh kg −1 at 0.1 C (based on the combined masses of the active cathode and anode) and retains 62.4% of its initial capacity after 400 cycles at 0.5 C. These findings provide valuable insights into designing Co/Li-free, air-stable HELOs for durable and economical sodium-ion battery cathodes.

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