Two-Dimensional WS2@Nitrogen-Doped Graphite for High-Performance Lithium Ion Batteries: Experiments and Molecular Dynamics Simulations
- Two-Dimensional WS2@Nitrogen-Doped Graphite for High-Performance Lithium Ion Batteries: Experiments and Molecular Dynamics Simulations
- 조원일; Tekalign Terfa Debela; 임영록; 서희원; 권익선; 곽인혜; 박정희; 강홍석
- tungsten disulfide; nanosheets; lithium ion battery; N-doped graphite; molecular dynamic simulation
- Issue Date
- ACS Applied Materials & Interfaces
- VOL 10-37936
- As promising candidates for anode materials in lithium ion batteries (LIB), two-dimensional tungsten disulfide (WS2) and WS2@(N-doped) graphite composites were synthesized, and their electrochemical properties were comprehensibly studied in conjunction with calculations. The WS2 nanosheets, WS2@graphite, and WS2@N-doped graphite (N-graphite) exhibit outstanding cycling performance with capacities of 633, 780, and 963 mA h g– 1, respectively. To understand their lithium storage mechanism, first-principles calculations involving a series of ab initio NVT– NPT molecular dynamics simulations were conducted. The calculated discharge curves for amorphous phase are well matched with the experimental ones, and the capacities reach 620, 743, and 915 mA h g– 1 for WS2, WS2@graphite, and WS2@N-graphite, respectively. The large capacities of the two composites can be attributed to the tendency of W and Li atoms to interact with graphite, suppressing the formation of W metal clusters. In the case of WS2@N-graphite, vigorous amorphization of the N-graphite enhances the interaction of W and Li atoms with the fragmented N-graphite in such a way that unfavorable Li– W repulsion is avoided at very early stage of lithiation. As a result, the volume expansion in WS2@graphite and WS2@N-graphite is calculated to be remarkably small (only 6 and 44%, respectively, versus 150% for WS2). Therefore WS2@(N-)graphite composites are expected to be almost free of mechanical pulverization after repeated cycles, which makes them promising and excellent candidates for high-performance LIBs.
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