Abstract
In situ electrochemical cycling combined with total scattering measurements can provide valuable structural information on crystalline, semi-crystalline and amorphous phases present during (dis)charging of batteries. In situ measurements are particularly challenging for total scattering experiments due to the requirement for low, constant and reproducible backgrounds. Poor cell design can introduce artefacts into the total scattering data or cause inhomogeneous electrochemical cycling, leading to poor data quality or misleading results. This work presents a new cell design optimized to provide good electrochemical performance while performing bulk multi-scale characterizations based on total scattering and pair distribution function methods, and with potential for techniques such as X-ray Raman spectroscopy. As an example, the structural changes of a nanostructured high-capacity cathode with a disordered rock-salt structure and composition Li4Mn2O5 are demonstrated. The results show that there is no contribution to the recorded signal from other cell components, and a very low and consistent contribution from the cell background.
Highlights
The global increasing demand for sustainable energy delivers a formidable challenge to develop new electrode materials for rechargeable batteries with ever-increasing energy densities, longer cycle durability and minimal environmental impact, which operate safely and at low cost
Duringcharging of the cell, charged cations are transferred between the electrode materials, whose structures accommodate a large number of defects coupled to changes in the oxidation state of transition metals or anions which can lead to phase separation or amorphization (Grey & Tarascon, 2016)
Most readily available in situ cells are not optimized for pair distribution function (PDF) experiments, limiting the systems investigated to those with sufficient scattering to obtain useable PDF data
Summary
The global increasing demand for sustainable energy delivers a formidable challenge to develop new electrode materials for rechargeable batteries with ever-increasing energy densities, longer cycle durability and minimal environmental impact, which operate safely and at low cost. Kapton windows have been replaced by rigid and conductive low-Z elements, like glassy carbon or beryllium, in other cell designs (Leriche et al, 2010; Sottmann et al, 2016; Borkiewicz et al, 2012; Hartung et al, 2015), offering an improved seal, stack pressure and conductivity for in situ XAS and Bragg diffraction experiments These multipurpose electrochemical cells, AMPIX (Borkiewicz et al, 2012) or Bruker (Leriche et al, 2010), are based on more standard coin and Swagelok cells, respectively. The new DRIX cell consists of thin-walled fused quartz tubes and low-Z rods acting as current collectors Such design minimizes the parasitic scattering and absorption from the cell, and allows the collection of high-quality total scattering and PDF data, even on weakly scattering or amorphous phases, in only a few minutes. We demonstrate the ability to efficiently probe multiple battery cells during a single experiment with excellent data quality comparable with ex situ data acquisitons
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