In situ X-ray diffraction is today a standard tool in the study of different electrochemical processes including charge and discharge of Li-ion batteries. Many subtle structural details like lithium ion ordering and the formation of superstructures are however difficult to unravel with X-ray diffraction, due to the relatively low scattering power of lithium. Additional information from neutron diffraction would certainly be very valuable. Despite this need, there are only a few examples of in situ neutron diffraction experiments on Li-ion batteries in the literature. Either a special in situ cell is constructed or the diffraction experiment is performed on a commercial battery. Common for the purpose built in situ cells is the difficulty to achieve a stable long time electrochemical cycling. This is amongst other things due to the fare from optimised diffusion path for lithium in the electrolyte and the difficulty to avoid water contamination in the sensitive electrochemical processes. The huge incoherent scattering from hydrogen containing components is usually detrimental to the results when commercial batteries are used in the diffraction experiments.

As a part of the ongoing upgrade of the POLARIS diffractometer at the ISIS facility in England we try to develop an in situ electrochemical cell for neutron diffraction. Inspired by the success of pouch cell transmission in situ set ups for X-ray diffraction we aim for a sample construction very similar to an ordinary mobile phone battery. The combination of a high intensity of the primary beam and the large solid angle covered by the detector banks makes this diffractometer ideal also for time resolved in situ experiments. By careful choice of materials in the cell and the use of deuterated solvents in the electrolyte we will drastically reduce the incoherent background and increase the signal to noise level. Preliminary results from this work will be presented.

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1. Time resolved in situ studies of Li-ion batteries
2. The kinetics of lithium insertion in tin-based alloys studied by time-resolved synchrotron based in situ X-ray diffraction