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Suppression of Electrochemically Driven Phase Transitions in Nanostructured MoS2 Pseudocapacitors Probed Using
John B Cook1, Terri C Lin1, Hyung-Seok Kim2
1Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California 90095 , United States.
Nanostructuring molybdenum disulfide (MoS2) nanocrystals suppresses phase transitions, enabling faster charge storage. This creates nearly ideal pseudocapacitors with enhanced kinetics compared to bulk materials.
Area of Science:
- Materials Science
- Electrochemistry
- Nanotechnology
Background:
- Pseudocapacitors offer faster charge storage kinetics than conventional batteries.
- Nanostructuring battery materials can induce pseudocapacitive behavior.
- Metallic 1T MoS2 nanocrystals previously showed enhanced charge storage over bulk MoS2.
Purpose of the Study:
- To investigate the mechanism behind the high capacitive response in metallic 1T MoS2 nanocrystals.
- To elucidate the role of nanostructuring in suppressing phase transitions during electrochemical cycling.
Main Methods:
- Operando X-ray diffraction studies during electrochemical cycling.
- Quantitative electrochemistry and galvanostatic charge-discharge analysis.
Main Results:
- Bulk MoS2 exhibits a first-order phase transition (1T to triclinic) during lithiation/delithiation, observed via distinct plateaus and new XRD peaks.
- MoS2 nanocrystal assemblies suppressed this phase transition, showing no plateaus or additional peaks in XRD.
- Nanostructuring leads to solid-solution-like behavior, attributed to suppressed nucleation in confined nanocrystal spaces.
Conclusions:
- Nanostructuring MoS2 suppresses the 1T-triclinic phase transition, a key factor limiting charge storage in bulk material.
- Suppression of phase transitions and shortened ion diffusion paths enable MoS2 nanocrystal assemblies to function as near-ideal pseudocapacitors.
- This work highlights nanostructuring as a strategy to enhance the electrochemical performance of MoS2 for energy storage applications.
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