Engineering a superionic conductor surface enables fast Na⁺ transport kinetics for high-stable layered oxide cathode

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable sodium-ion batteries face challenges with layered oxide cathodes due to unstable interfaces and side reactions, limiting fast charging and long-term cycling.
• Degradation of the cathode/electrolyte interphase leads to structural instability and capacity fade, particularly at high operating potentials.

Purpose of the Study:

• To develop a surface modification strategy for O3-type layered NaNi1/3Fe1/3Mn1/3O2 (NFM) cathodes to improve stability during fast charging and cycling.
• To investigate the use of a superionic conductor, Na3V2(PO4)3 (NVP), as a bonding agent to stabilize the NFM cathode interface.

Main Methods:

• A surface coating strategy was employed, bonding NVP onto the NFM cathode material.
• Electrochemical performance was evaluated, including rate capability, initial coulombic efficiency, and cyclic stability up to high cutoff voltages.
• The interfacial properties and structural integrity of the modified cathode were analyzed.

Main Results:

• The NVP coating effectively suppressed electrolyte corrosion and near-surface deconstruction of the NFM cathode.
• The composite NFM@NVP electrode exhibited enhanced phase change reversibility and reduced transition metal dissolution.
• The NFM@NVP cathode demonstrated a high initial coulombic efficiency (95.5% at 0.1 C), excellent rate capability (100 mAh g-1 at 20 C), and remarkable cyclic stability (80% capacity retention after 500 cycles at 2 C).

Conclusions:

• The NVP bonding surface strategy is a facile and universal approach to enhance the interphase stability of layered oxide cathodes for sodium-ion batteries.
• This method significantly improves the electrochemical performance, enabling fast-charging and long-term cycling for sustainable energy storage applications.