Two-Dimensional WS₂@Nitrogen-Doped Graphite for High-Performance Lithium Ion Batteries: Experiments and Molecular...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Two-dimensional tungsten disulfide (WS2) is a promising anode material for lithium-ion batteries (LIBs).
• WS2-based materials often face challenges with capacity retention and volume expansion during cycling.
• Graphite and nitrogen-doped graphite are explored as composite components to enhance WS2 performance.

Purpose of the Study:

• To synthesize and electrochemically evaluate WS2 nanosheets and WS2@(N-doped) graphite composites for LIB anodes.
• To elucidate the lithium storage mechanism in these materials using experimental and computational methods.
• To assess the structural stability and capacity retention of the developed composite materials.

Main Methods:

• Synthesis of WS2 nanosheets, WS2@graphite, and WS2@N-doped graphite composites.
• Comprehensive electrochemical characterization, including cycling performance and capacity measurements.
• First-principles calculations and ab initio NVT-NPT molecular dynamics simulations to study lithium storage mechanisms.

Main Results:

• WS2@N-doped graphite exhibited the highest reversible capacity (963 mA h g⁻¹), outperforming WS2 nanosheets (633 mA h g⁻¹) and WS2@graphite (780 mA h g⁻¹).
• Computational results closely matched experimental discharge curves, confirming the lithium storage mechanisms.
• Composites showed significantly reduced volume expansion (6% for WS2@graphite, 44% for WS2@N-graphite) compared to pure WS2 (150%).

Conclusions:

• WS2@(N-)graphite composites demonstrate excellent electrochemical performance and cycling stability for LIB anodes.
• The enhanced performance is attributed to favorable W-Li interactions with graphite and suppressed W metal cluster formation.
• WS2@(N-)graphite composites are promising candidates for high-performance, durable lithium-ion batteries due to their structural integrity.