Confined Solvation Electrolyte for 4.3-V-Class High-Voltage Sodium-Ion Pouch Cells

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• P2-type layered transition metal oxides offer cost-effectiveness and air stability for sodium-ion batteries.
• High-voltage operation is crucial for increased energy density but faces challenges like sluggish ion desolvation and degradation.

Purpose of the Study:

• To develop a new electrolyte strategy for stable high-voltage operation of P2-type sodium-ion batteries.
• To improve the capacity, cycling stability, and temperature range of sodium-ion batteries.

Main Methods:

• Identification of 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide (Me2TFMSA) as a polar inducer in electrolytes.
• Development of a confining solvation electrolyte (CSE) by restructuring Na+ solvation sheaths.
• Electrochemical testing of P2-type Na0.6[Mg0.04Ca0.02Ti0.1Mn0.55Ni0.29]O2 (NaNMO) cathodes and hard carbon||NaNMO pouch cells.

Main Results:

• The CSE enables a 4.3 V cutoff voltage, achieving a 25.8% capacity gain for NaNMO cathodes.
• Parasitic reactions, transition-metal dissolution, and impedance growth are significantly suppressed.
• Ah-level pouch cells demonstrate 74.8% capacity retention after 800 cycles, outperforming conventional electrolytes.
• Stable performance is maintained across a wide temperature range (-30 to 45 °C).

Conclusions:

• Solvation confinement is a key strategy for enhancing interfacial stability in high-voltage sodium-ion batteries.
• The developed CSE significantly improves the practical performance of P2-type sodium-ion batteries.
• This work paves the way for advanced sodium-ion battery technologies operating at higher voltages and wider temperatures.