Sodium Nickel Iron Manganese Oxide BN-O3A O3 Type Sodium Ion Battery Positive Electrode Material

Overview​​

​​O3-type NaNiFeMnO₂ (BN-O3A)​​ is a layered transition metal oxide cathode material for sodium-ion batteries, with the general formula NaNiₓFeᵧMn₁₋ₓ₋ᵧO₂. It is characterized by its high theoretical capacity (~140 mAh/g at 0.1C), cost-effectiveness (abundant Fe/Mn resources), and structural stability. The "O3" denotes a trigonal prismatic coordination of Na⁺ ions, enabling high Na⁺ content but suffering from irreversible phase transitions during cycling.

​Key Features​​

1. ​​Composition & Structure​​:

   • Typical stoichiometry includes NaNi₁/₃Fe₁/₃Mn₁/₃O₂ (111-type) or variants like NaNi₀.₄Fe₀.₂Mn₀.₄O₂.
   • Transition metals (Ni, Fe, Mn) synergize: ​​Ni​​ boosts capacity, ​​Mn​​ stabilizes structure, and ​​Fe​​ balances cost/performance.

2. ​​Challenges​​:

   • ​​Irreversible phase transitions​​ (>4.0V) lead to structural degradation.
   • ​​Air sensitivity​​: Reacts with moisture, forming electrochemically inactive NaOH/Na₂CO₃.
   • ​​Jahn-Teller distortion​​ from Mn³⁺ and Ni⁴⁺-electrolyte side reactions.

3. ​​Performance Optimization​​:

   • ​​Doping​​ (e.g., Ti, Mg, Cu): Stabilizes structure, suppresses phase transitions, and enhances Na⁺ diffusion.
   • ​​Surface coating​​ (e.g., Al₂O₃, NaTi₂(PO₄)₃): Mitigates electrolyte corrosion and improves cyclability.
   • ​​Morphology control​​: Spherical secondary particles (4–10 μm) with nano-sized primary grains enhance kinetics.

​​Applications & Prospects​​

BN-O3A is a promising candidate for ​​large-scale energy storage​​ (e.g., grid storage, EVs) due to its low cost and compatibility with existing Li-ion battery manufacturing. Recent advances in ​​high-entropy doping​​ and ​​P/O hybrid phases​​ aim to further improve energy density (>420 Wh/kg) and cycle life (>500 cycles at 1C)

Specifications​