Modulation of electron/ion transport in electrodes through the appropriate mesoscale electrode structural design is essential to achieving effective utilization of nanoscale electroactive materials. Herein, nanosheet MoS2+x/carbon [one-dimensional (1D) carbon nanotube (CNT) or two-dimensional (2D) graphene nanoplatelet (GNP)] heterostructures are prepared via a simple, one-step hydrothermal method, resulting in high-loading (16.2-21.0 mg/cm2) binder-free three-dimensional (3D) porous electrodes. In lithium-based batteries, an anionic S22--S2-redox system is demonstrated based on combined structural characterization using X-ray photoelectron spectroscopy, Raman spectroscopy, and in situ synchrotron-based X-ray absorption spectroscopy to elucidate the electrochemical behavior of the Mo and S centers. MoS2+x-GNP electrodes delivered 177 mAh/g (2.9 mAh/cm2) in the first cycle and 78 mAh/g (1.3 mAh/cm2) after 100 cycles at a current of 3.2 mA/cm2, representing high capacities despite such a high material loading for a sulfur-equivalent system, with 44% capacity retention and good rate capability. Conversely, the MoS2+x-CNT heterostructure displayed lower capacity and more capacity fade at all rates, attributed to aggregation of the active and carbonaceous materials in these electrodes and poor access to MoS2+xedge sites, as visualized via 3D Raman mapping and electron microscopy. The significantly improved capacity retention of the MoS2+x-GNP system is attributed to the (i) morphology because the arrangement of the 2D MoS2+xnanosheets on the GNP substrate allows for edge sites with excess sulfur to be exposed, (ii) increased stability of the structure during cycling, and (iii) homogeneous dispersion of the active and carbonaceous materials, resulting in good electrical contact.
|Number of pages||16|
|Journal||ACS Applied Nano Materials|
|Publication status||Published - 2022 Apr 22|
Bibliographical noteFunding Information:
This work was supported as part of the Center for Mesoscale Transport Properties, an Energy Frontier Research Center supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, via Grant DE-SC0012673. This research used beamlines 7-BM and 8-BM of the NSLS-II, a U.S. DOE, Office of Science, User Facility operated for the U.S. DOE, Office of Science, by Brookhaven National Laboratory under Contract DE-SC0012704. The XPS measurements used resources of the Center for Functional Nanomaterials, which is a U.S. DOE, Office of Science, Facility at Brookhaven National Laboratory under Contract DE-SC0012704. We also acknowledge the Advanced Energy Research and Technology Center for access to the ThINC facility for the electron microscopy measurements. D.M.L. acknowledges support through the National Science Foundation Graduate Research Fellowship under Grant 1839287. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. M.R.D. acknowledges support from the Graduate Assistance in Areas of National Need (GAANN) Fellowship sponsored by the U.S. Department of Education. E.S.T. acknowledges the William and Jane Knapp Chair in Energy and the Environment.
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All Science Journal Classification (ASJC) codes
- Materials Science(all)