Suppressed Voltage Decay by Local Structure Tuning for High-stability Sodium Layered Oxide Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• P2-type Fe/Mn-based layered oxides are promising cathode materials for sodium-ion batteries (SIBs) due to high capacity and cost.
• Jahn-Teller (J-T) effect in Fe⁴⁺ and Mn³⁺ causes lattice distortion, leading to voltage hysteresis, decay, and degradation in SIBs.

Purpose of the Study:

• To suppress Jahn-Teller distortions in Fe/Mn-based layered oxides for SIBs.
• To enhance the structural stability and electrochemical performance of cathode materials through trace element doping.

Main Methods:

• Introduction of trace amounts of scandium (Sc) into the transition-metal layers of P2-type oxides.
• Structural and electrochemical characterization of the Sc-doped material (Na₀.₆₇Fe₀.₄₉Mn₀.₅Sc₀.₀₁O₂).
• Analysis of local electronic structure and coordination environment modulation by Sc doping.

Main Results:

• Sc doping enhanced TM-O covalency and reduced ligand field symmetry, suppressing Fe⁴⁺ and Mn³⁺ J-T distortions.
• The Sc-doped material (NFMO-Sc) exhibited suppressed voltage hysteresis and decay.
• Remarkable long-cycling stability was achieved for the NFMO-Sc cathode.

Conclusions:

• Trace-element doping, specifically Sc, is an effective strategy to mitigate J-T distortion in layered oxide cathodes.
• Local structural tuning via trace elements significantly enhances voltage stability and cycling life in SIBs.
• This approach offers valuable insights for designing high-stability cathode materials for advanced sodium-ion batteries.