Monolithic Interphase Enables Fast Kinetics for High-Performance Sodium-Ion Batteries at Subzero Temperature

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) show promise but face challenges in low-temperature performance due to sluggish kinetics and unstable interphases.
• Existing electrolytes struggle to maintain efficiency and stability in subzero conditions, limiting SIB applications.

Purpose of the Study:

• To develop a low-concentration electrolyte for SIBs that enhances electrochemical performance at low temperatures.
• To investigate the formation and properties of the electrode/electrolyte interphase at subzero temperatures.

Main Methods:

• Formulation of a 0.5M NaPF6 electrolyte in diethylene glycol dimethyl ether.
• Electrochemical testing of SIBs (Na0.7Li0.03Mg0.03Ni0.27Mn0.6Ti0.07O2//Na and hard carbon//Na) at low temperatures.
• Analysis of the cathode/electrolyte interphase using advanced characterization techniques.

Main Results:

• The proposed electrolyte forms a thin, amorphous, and homogeneous cathode/electrolyte interphase rich in organic components.
• This interphase facilitates Na+ migration and blocks detrimental side reactions, improving structural stability.
• SIBs demonstrated high capacity retention (90.8% after 900 cycles at 1C) and a capacity over 310 mAh g-1 at -30°C.

Conclusions:

• The developed low-concentration electrolyte significantly improves the low-temperature performance of SIBs.
• The engineered interphase is key to achieving long-term cycling stability and excellent rate capability in subzero environments.
• This work paves the way for practical SIB applications in cold climates.