1 nm-Level Solid Electrolyte Interphase on Coal-Based Hard Carbon Enables Superior Sodium Storage

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• The solid electrolyte interphase (SEI) is critical for battery performance, influencing ion transport and storage.
• Precise control over SEI thickness is a significant challenge in battery development.

Purpose of the Study:

• To develop a synergistic strategy for precise SEI thickness control on coal-based hard carbon.
• To investigate the impact of tailored surface chemistry and microstructure on SEI formation and battery performance.

Main Methods:

• Constructed a 1nm-level SEI using phosphate-directed etching in a confined microenvironment.
• Modified coal-based hard carbon surface chemistry and microstructure.
• Analyzed SEI composition and structure, including surface oxygen content and pore volume.

Main Results:

• Reduced surface oxygen content from 6.80 to 1.73 at.% and increased pore volume fourfold.
• Formed a 1nm-level SEI with an organic outer layer and an inner layer rich in Na2O and Na2CO3.
• Achieved superior initial coulombic efficiency (92.18%), reversible capacity (363 mAh g-1), and rate capability (231.2 mAh g-1 at 3 A g-1).

Conclusions:

• The developed strategy enables precise SEI thickness control, crucial for advanced battery anodes.
• The tailored coal-based hard carbon demonstrates exceptional performance in sodium-ion batteries.
• This approach offers a promising pathway for designing high-performance batteries across various chemistries.