Long-Range Cation Disorder Enhances Comprehensive Performance in Mn-Rich Layered Sodium Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Manganese-rich layered oxides (MRLOs) are cost-effective cathode materials for sodium-ion batteries (SIBs).
• Challenges include low energy density due to Mn redox potentials and structural destabilization from Jahn-Teller distortion around Mn3+.
• Complex cation ordering in MRLOs impedes sodium-ion (Na+) migration.

Purpose of the Study:

• To discover novel cation ordering structures in MRLOs.
• To mitigate Jahn-Teller distortion and enhance Na+ diffusion kinetics.
• To improve the electrochemical performance of SIB cathodes.

Main Methods:

• Regulating oxygen vacancy formation to disrupt cation ordering.
• Utilizing Maximum Entropy Method (MEM) analysis on neutron diffraction data.
• Investigating electrochemical performance in a half-cell configuration.

Main Results:

• Disruption of long-range cation ordering effectively mitigated cooperative Jahn-Teller distortion.
• Achieved 95.3% capacity retention over 1000 cycles at 8C.
• Optimized Na+ diffusion pathways and kinetics were visualized.
• Elevated Mn4+/Mn3+ redox potential led to a competitive energy density of 626 Wh kg-1 (1.5-4.5 V).

Conclusions:

• Disrupting long-range cation ordering is a feasible strategy for optimizing sodium-ion cathodes.
• This approach enhances structural stability and Na+ diffusion.
• Significant improvements in electrochemical performance, including energy density and cycle life, were demonstrated.