Carbon Excess C₃N: A Potential Candidate as Li-Ion Battery Material

Area of Science:

• Materials Science
• Electrochemistry
• Computational Materials Science

Background:

• Carbon nitride (C3N) has shown promise as a lithium-ion battery anode material.
• Experimental studies reported high capacities but significant capacity fade in C3N.
• The exact composition and its effect on electrochemical performance were unclear.

Purpose of the Study:

• To investigate the Li-ion intercalation mechanism in C3N using first-principle simulations.
• To understand the reasons for capacity loss observed in experimental studies.
• To identify an optimized C3N composition for high-performance lithium-ion batteries.

Main Methods:

• First-principle simulations were employed to study lithium ion intercalation.
• Theoretical capacities were calculated for pure C3N, N-excess C2.67N, and C-excess C3.33N.
• Electrochemical properties including voltage, capacity, and conductivity were evaluated.

Main Results:

• Pure C3N exhibits a low theoretical capacity (133.94 mAh·g−1).
• Nitrogen-excess C2.67N shows a high theoretical capacity (837.06 mAh·g−1) but suffers from irreversible Li-ion trapping, explaining experimental capacity loss.
• Carbon-excess C3.33N demonstrates a high reversible capacity (840.35 mAh·g−1), low operating voltage (0.12 V), fast charge/discharge rates, and good conductivity.

Conclusions:

• The experimental high capacity in Xu et al.'s work is attributed to N-excess C2.67N, not pure C3N.
• Irreversible Li-ion trapping in N-excess C3N is the cause of capacity fade.
• Carbon-excess C3.33N is proposed as a superior lithium-ion battery anode material due to its stability and excellent electrochemical performance.