Core-Shell: Resolving the Dilemma of Hard Carbon Anodes by Sealing Nanoporous Particles With Semi-Permeable Coatings

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Non-graphitic hard carbon anodes are crucial for high-capacity energy storage.
• Common anodes suffer from significant irreversible capacity losses during initial cycles.
• Integrating electrolyte solvent-sieving with storage capacity in a single material is challenging.

Purpose of the Study:

• To develop a core-shell strategy for non-graphitic hard carbon anodes.
• To overcome the trade-off between high capacity and irreversible first-cycle losses.
• To create a heterogeneous structure that mimics graphite's dual functionality.

Main Methods:

• Fabrication of core-shell structures using porous activated carbon cores and gas-phase deposited non-graphitic carbon shells.
• Gas sorption porosimetry (N2, CO2) and diethyl carbonate (DEC) sorption analysis to characterize porosity and shell permeability.
• Electrochemical testing to evaluate storage capacity and first-cycle reversibility.

Main Results:

• The core-shell structure successfully preserves core porosity while creating a semi-permeable shell.
• Diethyl carbonate sorption analysis proves effective in correlating liquid-solid interface interactions with first-cycle losses.
• The designed anodes achieve a high reversible capacity of 400 ± 24 mAh g⁻¹ with 82 ± 2% first-cycle reversibility.

Conclusions:

• The core-shell strategy effectively integrates storage capacity and electrolyte regulation in non-graphitic carbons.
• Reduced diethyl carbonate uptake in functional core-shell particles leads to enhanced performance.
• These anodes demonstrate state-of-the-art performance, compensating for sodium's larger size and showing commercial viability.