A Cylindrical Cell for Operando Neutron Diffraction of Li-Ion Battery Electrode Materials

Abstract

Neutron diffraction is a powerful technique to localize and quantify lithium in battery electrode materials. However, obtaining high-quality operando neutron diffraction data is challenging because it requires achieving good electrochemical performance while cycling a large amount of active material to ensure optimal signal-to-noise ratio. We have developed a cylindrical cell specifically suited for operando neutron diffraction studies, and used it to investigate the structural changes in the Ni-rich LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode material during cycling between 2.5 and 4.3 V vs. Li + /Li. The cell demonstrates reliable electrochemical performance, even after long-term cycling, and the important crystal structure parameters of the active material, including Li occupancy, could be successfully refined with the Rietveld method using neutron diffraction data collected in operando after appropriate background subtraction.

Understanding Rechargeable Battery Function Using In Operando Neutron Powder Diffraction

“…The thickness, mechanical strength, and electrochemical performance of the separator need to be considered in such substitutions. Although PP/PE separators have a high H atomic density, the total amount in a battery may be less than when using PVDF as the higher mechanical strength of PP/PE enables them to remain functional when thin …”

“…The preparation of evenly spaced electrodes is challenging, notably for larger format batteries. For cylindrical cells, hand winding may result in inhomogeneous contacts and separator tearing, as well as low wrap density, and mechanical preparation is recommended. Stacking of flat layers in prismatic cells is relatively easy by hand, although time‐consuming in a glove box.…”

“…Custom‐designed cell types for in operando NPD measurements can be summarized as the flat‐plate design with a single electrode/separator/electrode layer, the prismatic design with several stacked layers,4b,16a–c,e,45,49,61a,b,d,e the cylindrical type containing rolled layers,8,16d,23,25,29,43,50,51,56,58,61c,62,64 and the confined electrode type where the beam predominantly illustrates the electrode of interest ( Figure ).…”

“…c) Cylindrical rolled layer. Reproduced with permission under the terms of the Creative Commons Attribution License . Copyright 2018, The Authors.…”

“…Cylindrical Rolled Layer Cell : The cylindrical rolled layer cell contains an electrode and separator roll inserted into a cylindrical can, such as in the commercial 18650 cell, where the relatively large amount of active materials yields intense data despite the hydrogen in the electrolyte and separators . Custom cells have been made using cans composed of aluminum, quartz, nickel‐plated steel,62a and vanadium 61c,62b–e. Cylindrical rolled layer cells require long homogeneous electrodes, which may need mechanical preparation, and wrapping the stack in the laboratory setting can be challenging.…”