In-situ neutron diffraction study of the MoS2 anode using a custom-built Li-ion battery

This work presents the first in-situ neutron diffraction study of the MoS2 electrode, undertaken in a custom-built Li-ion battery during discharge. A review of custom-designed cells for in-situ neutron diffraction experiments is presented along with our optimised cell, which we use to show real-time information corresponding to Li-insertion into MoS2via disappearance of the (103) reflection and increase in the d-spacing of the (002) reflection. The changes in the diffraction patterns begin at the 1.1 V plateau and are complete during the 0.5 V plateau. Sequential Rietveld-refinement indicates the presence of an intermediate lithiated phase (LixMoS2) between MoS2 and LiMoS2. We observe the disappearance of all reflections for the MoS2, corresponding to the loss of long-range order, during the 0.5 V plateau and no new diffraction peaks appear with further electrochemical cycling. This result is indicative of a transformation from long-range ordered MoS2 to short-range ordered LiMoS2, a result that we confirm using ex-situ synchrotron X-ray and neutron diffraction.

Research Highlights
► Design and validation of a battery appropriate for in-situ neutron diffraction studies.
► Review of custom-designed cells available in the literature.
► Real-time evolution of the MoS2 to LiMoS2 transformation during the 1.1 and 0.5 V plateau.
► Disappearance of all reflections associated with MoS2-type compounds during the 0.5 V plateau.
► A new intermediate phase, LixMoS2, is found.