Understanding the (De)Sodiation Mechanisms in Na‐Based Batteries through Operando X‐Ray Methods (original) (raw)
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Progress in the field of Na-based batteries strongly relies on the development of new advanced materials. However, one of the main challenges of implementing new electrode materials is the understanding of their mechanisms (sodiation/desodiation) during electrochemical cycling. Operando studies provide extremely valuable insights into structural and chemical changes within different battery components during battery operation. The present review offers a critical summary of the operando X-ray based characterization techniques used to examine the structural and chemical transformations of the active materials in Na-ion, Na-air and Na-sulfur batteries during (de)sodiation. These methods provide structural and electronic information through diffraction, scattering, absorption and imaging or through a combination of these X-ray-based techniques. Challenges associated with cell design and data processing are also addressed herein. In addition, the present review provides a perspective on the future opportunities for these powerful techniques.
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X-ray absorption spectroscopy (XAS) as a local structural tool for the study of the electrochemical processes in battery materials is highlighted. Due to its elemental specificity and high penetration of the X-rays in the 4-35 keV range, XAS is particularly suited for this, allowing the study of battery materials using specifically developed in situ electrochemical cells. This energy is required to dislodge one core electron from transition metal or p-group atoms, which are commonly used as redox centers in positive and negative electrode materials. In such a simple picture, the ejected photoelectron is scattered by the surrounding atoms, producing characteristic traces in the X-ray absorption spectrum. Both positive and negative electrode materials (intercalation, alloy and conversion electrodes) can be studied. The chapter starts with an introduction of the context around battery studies, followed by a short explanation of the photoelectric effect at the basis of the X-ray absorption phenomenon and to specific features of XAS. A selection of XAS experiments conducted in the field of batteries will be then outlined, also emphasizing the effects due to nanoscale dimension of the material studied. Finally, a perspectives section will summarize the specific role that this spectroscopy has played in the battery community.
Advanced Energy Materials
is an assistant chemist at Argonne National Laboratory. His research focuses on both fundamental understanding by operando synchrotron X-ray techniques and materials development relating to electrochemical energy storage systems, including lithium-ion, sodiumion, lithium-sulfur and lithium-selenium batteries. Rachid Amine is an assistant chemist at Argonne National Laboratory (ANL) since 2013. He is also a Ph.D. candidate in Chemical Engineering Department at the University of Illinois at Chicago. His research efforts have focused on development of high energy materials and beyond lithium ion technologies.
Understanding Fundamentals and Reaction Mechanisms of Electrode Materials for Na-Ion Batteries
Small, 2018
Li and Na fall under Group I alkali metal in the periodic table and are assumed to have similar chemical properties. However, the performance of most electrode materials in both systems disregards a linear behavior, and they usually show reduced performance in the Na cells. [6] Nevertheless, the knowledge of the successful development of Li-ion batteries (LIBs) is beneficial for the development of NIBs as there is a large degree of similarity for the redox mechanisms in certain materials. The use of Na + as the charge carrier has several drawbacks compared with Li +. [7,8] These include: (1) Na has a larger molar mass (22.990 g mol −1) than Li (6.941 g mol −1). This makes the electrode materials containing Na heavier than their Li counterparts. (2) Na + /Na has a relatively higher reduction potential (−2.7 V vs SHE) compared with Li + /Li (E = −3.04 V vs SHE). This limits the potential of NIB anode to be higher than −2.7 V versus SHE to avoid the Na plating and the growth of Na dendrites. Thus, it is more difficult to develop NIBs with a voltage comparable or higher than LIBs. Nevertheless, −2.7 V versus SHE is still one of the lowest reduction potentials and thus NIBs yet can have a high voltage when coupled with a high-potential cathode. And (3) Na + has a larger radius (0.97 Å) than that of Li + (0.64). This may lead to a larger volume strain during sodiation and result in poor cycling performance. The larger radius of Na + may also cause its slow diffusion kinetics Development of efficient, affordable, and sustainable energy storage technologies has become an area of interest due to the worsening environmental issues and rising technological dependence on Li-ion batteries. Na-ion batteries (NIBs) have been receiving intensive research efforts during the last few years. Owing to their potentially low cost and relatively high energy density, NIBs are promising energy storage devices, especially for stationary applications. A fundamental understanding of electrode properties during electrochemical reactions is important for the development of low cost, high-energy density, and long shelf life NIBs. This Review aims to summarize and discuss reaction mechanisms of the major types of NIB electrode materials reported. By appreciating how the material works and the fundamental flaws it possesses, it is hoped that this Review will assist readers in coming up with innovative solutions for designing better materials for NIBs. Na-Ion Batteries The ORCID identification number(s) for the author(s) of this article can be found under
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The performances of Li-ion batteries depend on many factors amongst which the important ones are the electrode materials and their structural and electronic evolution upon cycling. For a better understanding of lithium reactivity mechanism of many materials the combination of X-Ray Powder Diffraction (XRPD) and Transmission Mössbauer Spectroscopy (TMS) providing both structural and electronic information during the electrochemical cycling has been carried out. Thanks to the design of a specific electrochemical cell, derived from a conventional Swagelock cell, such measurements have been realised in operando mode. Two examples illustrate the greatness of combining XRPD and TMS for the study of LiFe 0.75 Mn 0.25 PO 4 as positive electrode and TiSnSb as negative electrode. Different kinds of insertion or conversion reactions have been identified leading to a better optimization and design of performing electrodes.
In situ X-ray absorption spectroscopy—A probe of cathode materials for Li-ion cells
Fluid Phase Equilibria, 2006
In situ X-ray absorption spectroscopy is a powerful emerging technique that has the capability to observe the changes in ongoing electrochemical reactions. It is already well established in materials science, and it is becoming a significant tool for the electrochemical community. As with all X-ray absorption spectroscopies, extended X-ray absorption fine structure (EXAFS) has the advantage of being element specific. Interpretation of the spectra at different states of charge can provide very useful quantitative and qualitative information about the valence change of the constituent elements in the cathode material during the ongoing electrochemical reaction, the degree of distortion or changes in structure from the initial state of charge to the final state of charge and provide valuable information about the extent of degradation of the cathode material during continuous cycling. It can also provide valuable insight about how the nature of the electrochemical reactions changes when one of the transition metal constituents is removed or increased in content in the cathode material. It is often important to adjust the composition of the cathode material in order to achieve high specific capacity and long-term stability in Li-ion cells. This article details the development of the in situ XAS techniques to study electrochemical reactions using various X-ray absorption spectroscopies which are now possible with the advent of third generation synchrotron radiation sources and improved end stations. The strength of in situ EXAFS techniques is illustrated using examples of various interesting transition metal oxides. In this way, we aim to encourage chemists, chemical engineers and materials scientists to consider in situ X-ray absorption spectroscopy as an effective tool for developing an understanding the electronic structure of materials and the changes that it undergoes during electrochemical reactions. (A. Deb).
Update on Na-based battery materials. A growing research path
Energy & Environmental Science, 2013
This work presents an up-to-date information on Na-based battery materials. On the one hand, it explores the feasibility of two novel energy storage systems: Na-aqueous batteries and Na-O 2 technology. On the other hand, it summarises new advances on non-aqueous Na-ion systems. Although all of them can be placed under the umbrella of Na-based systems, aqueous and oxygen-based batteries are arising technologies with increasing significance in energy storage research, while non-aqueous sodium-ion technology has become one of the most important research lines in this field. These systems meet different requirements of energy storage: Na-aqueous batteries will have a determining role as a low cost and safer technology; Na-O 2 systems can be the key technology to overcome the need for high energy density storage devices; and non-aqueous Na-ion batteries have application in the field of stationary energy storage.
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Developing high-performance batteries relies on material breakthroughs. During the past few years, various in situ characterization tools have been developed and have become indispensible in studying and the eventual optimization of battery materials. However, soft X-ray spectroscopy, one of the most sensitive probes of electronic states, has been mainly limited to ex situ experiments for battery research. Here we achieve in situ and operando soft X-ray absorption spectroscopy of lithium-ion battery cathodes. Taking advantage of the elemental, chemical and surface sensitivities of soft X-rays, we discover distinct lithium-ion and electron dynamics in Li(Co 1/3 Ni 1/3 Mn 1/3 )O 2 and LiFePO 4 cathodes in polymer electrolytes. The contrast between the two systems and the relaxation effect in LiFePO 4 is attributed to a phase transformation mechanism, and the mesoscale morphology and charge conductivity of the electrodes. These discoveries demonstrate feasibility and power of in situ soft X-ray spectroscopy for studying integrated and dynamic effects in batteries.