Unlocking Interlayer Confinement Enables All-Slope Hard Carbon with Ultrafast and Highly Reversible Sodium Storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Hard carbon anodes in sodium-ion batteries face capacity decay issues due to interlayer confinement hindering sodium-ion diffusion.
• Existing methods to improve rate performance can lead to excessive SEI formation and lower initial Coulombic efficiency (ICE).

Purpose of the Study:

• To develop a strategy mitigating interlayer confinement and enabling rapid, reversible sodium storage kinetics in hard carbon anodes.
• To enhance the initial Coulombic efficiency (ICE) and overall cycling stability of sodium-ion battery anodes.

Main Methods:

• Amino N-guided through-pore engineering strategy.
• Facile gas-phase-assisted pyrolysis process.
• Simultaneous conversion of nitrogen configurations and in situ construction of vertically aligned through-pores.

Main Results:

• Achieved conversion of irreversible nitrogen to reversible pyridinic N sites and created through-pores.
• Formed a thin, gradient SEI layer with subsurface fluorides, reducing sodium loss.
• Obtained an ultrahigh ICE of 94.9%, high reversible capacity (400.3 mAh g⁻¹), and exceptional rate performance (208 mAh g⁻¹ at 50 A g⁻¹).
• Demonstrated outstanding cycling stability with 92.5% capacity retention after 9000 cycles.

Conclusions:

• Amino-mediated pore and defect management is crucial for synchronizing interfacial stability and ion transport kinetics.
• The developed strategy offers a viable design for high-power sodium-ion batteries.
• This approach effectively addresses capacity decay and enhances performance in hard carbon anodes.