X-ray absorption fine structure imaging of inhomogeneous electrode reaction in LiFePO4 lithium-ion battery cathode

Katayama, Misaki; Sumiwaka, Koichi; Miyahara, Ryota; Yamashige, Hisao; Arai, Hajime; Uchimoto, Yoshiharu; Ohta, Toshiaki; Inada, Yuji; Ogumi, Zempachi

doi:10.1016/j.jpowsour.2014.03.066

Cited by 59 publications

(61 citation statements)

References 49 publications

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“…Katayama et al identified local inhomogeneity 4 in the SOC of a LiFePO 4 -based composite electrode at a length scale of tens of microns, likely because of differences in the local electronic conductivity of the composite, and a similar phenomenon was found by Paxton et al using EDXRD 5 In the first camp, we highlight several experiments exploring qualitative trends in the RCD using synchrotron-based XAFS, XAS, or energy dispersive XRD (EDXRD) measurements of the SOC.…”

Section: Introductionsupporting

confidence: 66%

The reaction current distribution in battery electrode materials revealed by XPS-based state-of-charge mapping

Pearse

Gillette

Lee

et al. 2016

Phys. Chem. Chem. Phys.

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Morphologically complex electrochemical systems such as composite or nanostructured lithium ion battery electrodes exhibit spatially inhomogeneous internal current distributions, particularly when driven at high total currents, due to resistances in the electrodes and electrolyte, distributions of diffusion path lengths, and nonlinear current-voltage characteristics. Measuring and controlling these distributions is interesting from both an engineering standpoint, as nonhomogenous currents lead to lower utilization of electrode material, as well as from a fundamental standpoint, as comparisons between theory and experiment are relatively scarce. Here we describe a new approach using a deliberately simple model battery electrode to examine the current distribution in a electrode material limited by poor electronic conductivity. We utilize quantitative spatially resolved X-ray photoelectron spectroscopy to measure the spatial distribution of the state-of-charge of a V2O5 model electrode as a proxy measure for the current distribution on electrodes discharged at varying current densities. We show that the current at the electrode-electrolyte interface falls off with distance from the current collector, and that the current distribution is a strong function of total current. We compare the observed distributions with a simple analytical model which reproduces the dependence of the distribution on total current, but fails to predict the correct length scale. A more complete numerical simulation suggests that dynamic changes in the electronic conductivity of the V2O5 concurrent with lithium insertion may contribute to the differences between theory and experiment. Our observations should help inform design criteria for future electrode architectures.

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Section: Introductionsupporting

confidence: 66%

The reaction current distribution in battery electrode materials revealed by XPS-based state-of-charge mapping

Pearse

Gillette

Lee

et al. 2016

Phys. Chem. Chem. Phys.

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“…As a highly elementspecific spectroscopy, XANES allows us to detect fine structural and chemical information changes, which is particularly effective to track the nanoscale interfacial phase transformation details. Significantly different than a conventional XANES chemical mapping study 26,27 , each pixel of the sample image in our experiment produces the XANES spectrum without scanning the sample. This full-field TXM-XANES imaging produces 2 k by 2 k (for example, a 2K Â 2K detector) XANES spectra to provide a full chemical map while at the same time keeping both time resolution(second) and spatial resolution (nanometer).…”

Section: Resultsmentioning

confidence: 99%

In operando tracking phase transformation evolution of lithium iron phosphate with hard X-ray microscopy

2014

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The delithiation reaction in lithium ion batteries is often accompanied by an electrochemically driven phase transformation process. Tracking the phase transformation process at nanoscale resolution during battery operation provides invaluable information for tailoring the kinetic barrier to optimize the physical and electrochemical properties of battery materials. Here, using hard X-ray microscopy-which offers nanoscale resolution and deep penetration of the material, and takes advantage of the elemental and chemical sensitivity-we develop an in operando approach to track the dynamic phase transformation process in olivine-type lithium iron phosphate at two size scales: a multiple-particle scale to reveal a rate-dependent intercalation pathway through the entire electrode and a single-particle scale to disclose the intraparticle two-phase coexistence mechanism. These findings uncover the underlying twophase mechanism on the intraparticle scale and the inhomogeneous charge distribution on the multiple-particle scale. This in operando approach opens up unique opportunities for advancing high-performance energy materials.

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“…Being a light element, lithium is difficult to detect with X-rays, for which reason most photon techniques typically use the change in oxidation state of the heavier ions to observe lithium intercalation (Nonaka et al, 2006;Katayama et al, 2014) or changes in interatomic spacing upon lithium insertion or extraction (Ganapathy et al, 2014;Zhang et al, 2014). Neutrons probe atom cores and therefore favor detection of the lighter elements compared to X-rays (Itkis et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Operando Neutron Depth Profiling to Determine the Spatial Distribution of Li in Li-ion Batteries

Verhallen

Wagemaker

2018

Front. Energy Res.

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Neutron Depth Profiling (NDP) allows determination of the spatial distribution of specific isotopes, via neutron capture reactions. In a capture reaction charged particles with fixed kinetic energy are formed, where their energy loss through the material of interest can be used to provide the depth of the original isotope. As lithium-6 has a relatively large probability for such a capture reaction, it can be used by battery scientists to study the lithium concentration in the electrodes even during battery operation. The selective measurement of the 6 Li isotope makes it a direct and sensitive technique, whereas the penetrative character of the neutrons allows practical battery pouch cells to be studied. Using NDP lithium diffusion and reaction rates can be studied operando as a function of depth, opening a large range of opportunities including the study of alloying reactions, metal plating, and (de) intercalation in insertion hosts. In the study of high rate cycling of intercalation materials the relatively low Li density challenges counting statistics while the limited change in electrode density due to the Li-ion insertion and extraction allows straightforward determination of the Li density as a function of electrode depth. If an electrode can be (dis)charged reversibly, data can be acquired and accumulated over multiple cycles to increase the time resolution. For Li metal plating and alloying reactions, the large lithium density allows good time resolution, however the large change of the electrode composition and density makes extracting the Li-density as a function of depth more challenging. Here an effective method is presented, using calibration measurements of the individual components, based on which the ratio of the components as a function of depth can be determined as well as the total Li-density. The same principles can be applied to insertion host materials, where the differences in density due to electrolyte infiltration yield the electrode porosity as a function of depth. This is of particular importance for battery electrodes where porosity has a direct influence on the energy density and charge transport.

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X-ray absorption fine structure imaging of inhomogeneous electrode reaction in LiFePO4 lithium-ion battery cathode

Cited by 59 publications

References 49 publications

The reaction current distribution in battery electrode materials revealed by XPS-based state-of-charge mapping

The reaction current distribution in battery electrode materials revealed by XPS-based state-of-charge mapping

In operando tracking phase transformation evolution of lithium iron phosphate with hard X-ray microscopy

Operando Neutron Depth Profiling to Determine the Spatial Distribution of Li in Li-ion Batteries

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