Synergistic Charge Compensation Process in P2-Type Layered Oxides Enables High-Reversibility Sodium-Ion Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• P2-type layered oxides are promising cathode materials for sodium-ion batteries (SIBs) due to their high capacity and voltage.
• Challenges include the Jahn-Teller effect from Mn3+ and structural degradation from oxygen evolution and cation displacement at high voltages.

Purpose of the Study:

• To investigate the synergistic effects of Cu/Ti co-substitution in P2-type cathodes for enhanced structural reversibility and electrochemical performance in SIBs.
• To elucidate the charge compensation mechanisms and stabilization strategies offered by dual cationic substitution.

Main Methods:

• Co-substitution of Cu and Ti into P2-type layered oxide structures.
• Electrochemical testing including cycling performance and capacity retention.
• Analysis of structural stability and redox mechanisms under varying potentials.

Main Results:

• Cu/Ti co-substitution establishes synergistic charge compensation, improving structural reversibility across the full voltage range.
• Ti-O bonding suppresses oxygen evolution at high voltages; Cu redox elevates voltage and stabilizes Ni valence.
• Optimized Na0.7Ni0.2Mn0.6Cu0.15Ti0.05O2 (TC-NNMO) cathode shows 151.88 mAh g-1 capacity, retaining 80.29% after 200 cycles.

Conclusions:

• Dual cationic substitution effectively regulates charge compensation, enhancing the stability and cyclability of P2-type cathodes.
• This multi-ion cooperative strategy provides a new paradigm for designing high-performance layered oxide cathodes for sodium-ion batteries.