Anionic-Based Layered Oxide Cathodes with High Electrochemical Performance through Dual-Site Substitutions for...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layered oxide cathodes with anionic redox offer high energy density for sodium-ion batteries (SIBs).
• Instability and poor electrochemical stability hinder practical application of these SIB cathodes.

Purpose of the Study:

• To enhance the electrochemical performance of Mn-rich layered oxide cathodes for SIBs.
• To investigate the effect of Al and Zn dual-site substitution on cathode stability and energy density.

Main Methods:

• Synthesis and characterization of a novel Al and Zn co-substituted layered oxide cathode (Na_0.73Zn_0.03Li_0.25Mn_0.76Al_0.01O₂).
• Electrochemical testing, including discharge capacity, rate capability, and cycling stability.
• Full-cell assembly with hard carbon anode and advanced material characterization to understand performance improvements.

Main Results:

• The AlZn cathode achieved a high discharge capacity of 242 mAh g^-1 and excellent rate capability (162 mAh g^-1 at 1000 mA g^-1).
• The cathode demonstrated superior capacity retention (89.69% over 150 cycles).
• A full-cell SIB exhibited a high energy density of 317 Wh kg^-1 and 80.8% capacity retention after 250 cycles.

Conclusions:

• Al and Zn dual-site substitution effectively enhances the electrochemical stability and energy density of Mn-rich layered oxide cathodes.
• The synergistic effect of Al-O and O-Zn-O bonds mitigates phase transformation and cracking, leading to improved performance.
• This strategy offers a promising pathway for developing high-energy sodium-ion batteries.