Mitigating Jahn-Teller Effect in Layered Cathode Material Via Interstitial Doping for High-Performance Sodium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layered transition metal oxides are key cathode materials for sodium-ion batteries (SIBs) due to high energy density.
• Poor structural stability limits the practical application of these SIB cathodes.
• Interstitial site doping is explored as a strategy to enhance material properties.

Purpose of the Study:

• To improve the structural stability and electrochemical performance of Na_0.67 Fe_0.5 Mn_0.5 O₂ for SIBs.
• To investigate the effect of B³⁺ doping at interstitial tetrahedral sites.
• To elucidate the mechanism behind the performance enhancement.

Main Methods:

• Synthesis of B³⁺-doped Na_0.67 Fe_0.5 Mn_0.5 O₂ (Na_0.67 Fe_0.5 Mn_0.5 B_0.04 O₂).
• Electrochemical characterization including cycling and rate performance tests.
• Structural analysis using neutron powder diffraction, in situ X-ray diffraction, and X-ray absorption spectroscopy.

Main Results:

• Na_0.67 Fe_0.5 Mn_0.5 B_0.04 O₂ demonstrated excellent cycling stability with 88.8% capacity retention after 100 cycles at 1 C.
• Prominent rate performance was achieved, attributed to enhanced Na⁺ diffusion kinetics.
• B³⁺ doping mitigated Jahn-Teller distortion and P2-P2' phase transformation, stabilizing transition metal layers and suppressing dissolution.

Conclusions:

• Interstitial B³⁺ doping effectively enhances the structural integrity and electrochemical properties of P2-type layered oxides.
• The study provides insights into the mechanism of interstitial doping for improving SIB cathode materials.
• This doping approach offers a universal strategy for optimizing manganese-based sodium cathode materials.