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

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.
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.
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

Item	Unit	Specification	Value	Reference Standard	Test Equipment Model
Na	wt%	20.6 ± 0.3	20.7	GB/T 27598-2011	Agilent 5800
Ni	wt%	17.6 ± 0.3	17.6	GB/T 27598-2011	-
Fe	wt%	16.7 ± 0.3	16.7	-	-
Mn	wt%	16.5 ± 0.3	16.5	-	-
D10	μm	7.0 ± 0.5	7.9	GB/T 19077-2016	-
D50	μm	9.2 ± 0.5	9.7	GB/T 19077-2016	Beckman Coulter LS 13320
D90	μm	11.5 ± 0.5	11.8	GB/T 5162-202X	-
Tap density	g/cm³	≥1.9	2.0	-	Tap Density Testing Instrument
SSA (BET)	m²/g	≤2.0	0.5	GB/T 19587-2004	-
2TFPD	g/cm³	-	-	GB/T 24533-2019	MYCRO Carver 4350
0.1C Capacity	mAh/g	135 ± 2	136	Evaluate method in half cell	-
1C Capacity	mAh/g	130 ± 2	132	Electrolyte: 1M NaPF6 in esters solvent	-
Efficiency	-	-	-	Voltage window: 2.0-4.0V	-
50th Retention (1C)	%	-	90	-	-
NaOH	wt%	0.3	0.3	-	METTLER TOLEDO G20

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