Dual-Conduction Polymer Electrolyte and Stable Interphase Engineering for Room-/Subzero-Temperature, Long-Cycling...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state sodium batteries (ASSSBs) offer high energy density and safety but face challenges with low ionic conductivity and interfacial instability, especially at low temperatures.
• Poly(ethylene oxide) (PEO) is a common electrolyte but requires improvements for practical ASSSB applications.

Purpose of the Study:

• To develop a dual-strategy, liquid-free solid-state electrolyte for high-performance ASSSBs.
• To enhance ionic conductivity and interfacial stability at room and sub-zero temperatures.
• To establish an electrolyte-interface collaborative design for wide-temperature operation.

Main Methods:

• A dual-strategy solid-state electrolyte was designed using succinonitrile as a plasticizer with PEO.
• Sodium difluoro(oxalate)borate was used to form an in situ stable solid electrolyte interphase (SEI) on the sodium metal anode.
• Electrochemical performance was evaluated using symmetric Na||Na and full Na3V2(PO4)3||Na cells.

Main Results:

• The novel electrolyte achieved an ionic conductivity of 2.75 × 10^-4 S cm^-1 at room temperature.
• Na@NaF||Na@NaF symmetric cells demonstrated over 1,500 hours of stable cycling.
• Full cells retained 91.2% capacity after 1,000 cycles, and delivered 88.2 mAh g^-1 at -5 °C.

Conclusions:

• The developed electrolyte effectively addresses PEO limitations, enabling high ionic conductivity and stable interfaces.
• The electrolyte-electrolyte and electrolyte-anode interface synergy is crucial for high-performance ASSSBs.
• This work presents a viable pathway for high-performance, wide-temperature ASSSBs.