Influence of extensive disorder on the first order phase transformation and its implications on the rate capability and cycling stability of MoS2 nanosheets in intercalation regime

• Published in: Journal of power sources 2020-03, Vol.453, p.227867, Article 227867
• Main Authors: Budumuru, Akshay Kumar, Sudakar, C.
• Format: Article
• Language: English
• Subjects: Activation; Cycling stability; Defect-rich MoS2; High-rate capability; MoS2 nanosheets
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2020.227867

Continuous capacity loss or gain in electrodes during extended cycling is very intriguing. We investigate influence of nanosheet thickness and defects on charge storage properties of MoS2 nanosheets in intercalation regime. Strong correlation with irreversible lithium intake during first cycle is observed. Defect-rich nanosheets (MoS2−5L; with an average 5-layer thickness) show sloping potential indicating single-phase lithium intercalation during first lithiation, with unprecedentedly large Li+-intake (x~1.9) of which only half is extractable. Defect-suppressed nanosheets (MoS2−15L; 15 layers thick) exhibit flat potential characteristics of a first-order phase transformation with Li+-intake of x~1.22 and a capacity loss x~0.3. MoS2−15L nanosheets have larger charge storage at high current rates. MoS2−5L nanosheets show an increase in charge storage fraction upon cycling at high current rates. Similar results are seen for crystallites of intermediate layer thickness. EIS studies suggest reorganization of excess lithium in electrodes during high current cycling. Irreversible lithium trapped in the MoS2−5L nanosheets during the first cycle is contemplated to shuttle around activating the electrode and enhancing the charge storage properties. Optimum performance with large charge storage and extended cycling stability at high C-rates are seen in MoS2 nanosheets with a mix of certain degree of disorder and crystallinity. [Display omitted] •First order transformation is absent in MoS2 nanosheet with extensive disorder.•Extensive disorder in MoS2 nanosheets results in huge lithium intake x ~1.9.•Only half of the initial intake is reversible in disordered MoS2 nanosheets.•Larger crystallites of MoS2 nanosheets have high rate capability.•Lithium trapped in the defects activates the MoS2 nanosheets.