Structural Evolution of Electrochemically Lithiated MoS2Nanosheets and the Role of Carbon Additive in Li-Ion Batteries.
Understanding the structure and phase changes associated with conversion-type materials is key to optimizing their electrochemical performance in Li-ion batteries. For example, molybdenum disulfide (MoS2) offers a capacity up to 3-fold higher (∼1 Ah/g) than the currently used graphite anodes, but they suffer from limited Coulombic efficiency and capacity fading. The lack of insights into the structural dynamics induced by electrochemical conversion of MoS2still hampers its implementation in high energy-density batteries. Here, by combiningab initiodensity-functional theory (DFT) simulation with electrochemical analysis, we found new sulfur-enriched intermediates that progressively insulate MoS2electrodes and cause instability from the first discharge cycle. Because of this, the choice of conductive additives is critical for the battery performance. We investigate the mechanistic role of carbon additive by comparing equal loading of standard Super P carbon powder and carbon nanotubes (CNTs). The latter offer a nearly 2-fold increase in capacity and a 45% reduction in resistance along with Coulombic efficiency of over 90%. These insights into the phase changes during MoS2conversion reactions and stabilization methods provide new solutions for implementing cost-effective metal sulfide electrodes, including Li-S systems in high energy-density batteries.
Institute for Manufacturing, Department of Engineering, University of Cambridge , 17 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
Chandramohan
C
George
Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge , J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Andrew J
AJ
Morris
Institute for Manufacturing, Department of Engineering, University of Cambridge , 17 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
Mohammad H
MH
Modarres
Institute for Manufacturing, Department of Engineering, University of Cambridge , 17 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
Michael
M
De Volder