Injecting Excess Na into a P2-Type Layered Oxide Cathode to Achieve Presodiation in a Na-Ion Full Cell

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Initial sodium (Na) loss in cathodes limits specific capacity in Na-ion full cells, particularly for Na-deficient P2-type materials.
• Compensating for this irreversible Na loss is crucial for improving energy density and performance.

Purpose of the Study:

• To develop and evaluate a presodiation strategy for P2-type cathodes to overcome initial Na loss.
• To enhance the specific capacity and energy density of Na-ion full cells.

Main Methods:

• Electrochemical presodiation was used to inject 0.32 excess active Na into P2-type Na_0.67Li_0.1Fe_0.37Mn_0.53O₂ (NLFMO) cathodes.
• The structural changes and electrochemical performance of the presodiated NLFMO cathode in a hard carbon (HC)||NLFMO full cell were investigated.

Main Results:

• Presodiation converted the NLFMO structure from P2 to P'2 without impacting subsequent cycling stability.
• The presodiated HC||NLFMO_preNa full cell achieved a specific capacity of 125 mAh/g, significantly higher than the 61 mAh/g of the non-presodiated cell.
• The presodiation strategy demonstrated potential for scalability through alternative engineering approaches like Na-metal contact.

Conclusions:

• The proposed presodiation strategy effectively compensates for initial Na loss in Na-ion full cells.
• This approach offers a viable method to increase the specific capacity and energy density of Na-ion batteries, especially those using Na-deficient cathodes.