Electrolyte Engineering with Tamed Electrode Interphases for High-Voltage Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are crucial for grid-scale energy storage but suffer from unstable electrolyte/electrode interphases, particularly the cathode electrolyte interphase (CEI).
• High-voltage operation in SIBs leads to electrolyte decomposition, transition metal dissolution, and rapid capacity fade, limiting their practical application.

Purpose of the Study:

• To develop a balanced molecular design principle for SIB electrolytes.
• To create an ultra-thin, homogeneous, and robust CEI layer for enhanced cycling stability.
• To enable high-voltage and wide-temperature operation of SIBs.

Main Methods:

• Formulation of a novel electrolyte by coupling succinonitrile with moderately solvating carbonates.
• Investigation of the electrolyte's effect on CEI formation and stability at high voltage.
• Electrochemical testing of Na3V2O2(PO4)2F (NVOPF) cathodes and full cells.

Main Results:

• The proposed electrolyte demonstrated limited anodic decomposition and suppressed CEI component dissolution.
• NVOPF cathodes exhibited >90% capacity retention over 3000 cycles at 4.3 V.
• Full cells achieved stable cycling over 500 cycles with 99.6% average Coulombic efficiency and wide-temperature adaptability (-25 to 60 °C).

Conclusions:

• The developed electrolyte design principle successfully enables the formation of a stable CEI layer.
• This advancement significantly improves the long-term cycling performance and operational stability of high-voltage SIBs.
• The findings provide fundamental insights into electrolyte design for SIBs under demanding conditions.