A Multifunctional Surface Modifier Capable of Stabilizing and Accelerating Hard Carbon Anode Kinetics via Pore...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Hard carbon (HC) is a key anode material for sodium-ion batteries.
• Existing HC anodes face challenges like low Coulombic efficiency and poor fast-charge rates due to pore-induced electrolyte decomposition and slow Na+ kinetics.
• Current strategies often focus narrowly on surface reactions or electrolyte stability.

Purpose of the Study:

• To investigate the pore-sealing effect of an artificial solid-electrolyte interphase (SEI) using methyl blue (MB) as a surface modifier for HC anodes.
• To elucidate how MB modification impacts Na+ reaction kinetics from the surface to the bulk of the HC anode.
• To enhance the electrochemical performance of sodium-ion batteries.

Main Methods:

• Modification of commercial hard carbon (Type-2) with methyl blue (MB).
• Electrochemical performance testing (Coulombic efficiency, rate capability, cycling life).
• Theoretical calculations and empirical experiments to analyze Na+ reaction kinetics (desolvation, adsorption, transport, charge transfer).

Main Results:

• The MB modification layer effectively seals surface pores of HC, suppressing electrolyte decomposition.
• MB accelerates surface-to-bulk Na+ reaction kinetics, including desolvation, adsorption, SEI transport, and charge transfer.
• MB-modified HC demonstrates significantly improved Coulombic efficiency, superior rate capability, and extended cycling life compared to unmodified HC.

Conclusions:

• Methyl blue acts as an effective pore-sealing agent for HC anodes via an artificial SEI.
• MB modification enhances both surface and bulk Na+ kinetics, leading to improved battery performance.
• This approach offers a promising strategy for developing high-performance sodium-ion batteries.