Molecular Engineering Enabling High Initial Coulombic Efficiency and Rubost Solid Electrolyte Interphase for Hard...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Hard carbon (HC) is a promising anode for sodium-ion batteries (SIBs).
• However, unstable solid electrolyte interphase (SEI) formation and low initial Coulombic efficiency (ICE) hinder its commercialization.
• A novel strategy is urgently needed to overcome these limitations.

Purpose of the Study:

• To develop a molecular design strategy to enhance the performance of HC anodes in SIBs.
• To improve the stability of the SEI layer and increase the ICE of HC anodes.
• To demonstrate the practical application potential of the modified HC material.

Main Methods:

• Engineered disodium phthalate (DP) onto the surface of hard carbon (HC) to create DP-HC.
• Investigated the SEI layer characteristics on DP-HC, including thickness and stability in different electrolytes.
• Evaluated the electrochemical performance of DP-HC in SIBs, including ICE and cycling stability.
• Assembled and tested a Na3V2(PO4)3 (NVP)|DP-HC full cell.

Main Results:

• A stabilized and ultrathin (≈7.4 nm) SEI layer was formed on DP-HC, compatible with both ester and ether electrolytes.
• DP-HC exhibited a significantly improved ICE (>96.3%) compared to pure HC (60.8%) in NaPF6 in diglyme (G2) electrolyte.
• DP-HC demonstrated excellent cycling stability, maintaining performance for over 1600 cycles at 0.5 A g⁻¹.
• The NVP|DP-HC full cell achieved an exceptional ICE of 98.3% and stable cycling for 450 cycles.

Conclusions:

• The molecular design strategy of engineering DP onto HC effectively addresses SEI instability and low ICE in SIBs.
• DP-HC shows great promise as a high-performance anode material for practical SIB applications.
• This approach provides a valuable pathway for advancing HC commercialization in SIB technology.