Using In-Situ Laboratory and Synchrotron-Based X-ray Diffraction for Lithium-Ion Batteries Characterization: A Review on Recent Developments

Beam Effects in Synchrotron Radiation Operando Characterization of Battery Materials: X-Ray Diffraction and Absorption Study of LiNi0.33Mn0.33Co0.33O2 and LiFePO4 Electrodes

Operando synchrotron radiation-based techniques are a precious tool in battery research, as they enable the detection of metastable intermediates and ensure characterization under realistic cycling conditions. However, they do not come exempt of risks. The interaction between synchrotron radiation and samples, particularly within an active electrochemical cell, can induce relevant effects at the irradiated spot, potentially jeopardizing the experiment's reliability and biasing data interpretation. With the aim of contributing to this ongoing debate, a systematic investigation into these phenomena was carried out by conducting a root cause analysis of beam-induced effects during the operando characterization of two of the most commonly employed positive electrode materials in commercial Li-ion batteries: LiNi0.33Mn0.33Co0.33O2 and LiFePO4. The study spans across diverse experimental conditions involving different cell types and absorption and scattering techniques and seeks to correlate beam effects with factors such as radiation energy, photon flux, exposure time, and other parameters associated with radiation dosage. Finally, it provides a comprehensive set of guidelines and recommendations for assessing and mitigating beam-induced effects that may affect the outcome of battery operando experiments.

Structure regulation and synchrotron radiation investigation of cathode materials for aqueous Zn-ion batteries

In view of the advantages of low cost, environmental sustainability, and high safety, aqueous Zn-ion batteries (AZIBs) are widely expected to hold significant promise and increasingly infiltrate various applications in the near future. The development of AZIBs closely relates to the properties of cathode materials, which depend on their structures and corresponding dynamic evolution processes. Synchrotron radiation light sources, with their rich advanced experimental methods, serve as a comprehensive characterization platform capable of elucidating the intricate microstructure of cathode materials for AZIBs. In this review, we initially examine available cathode materials and discuss effective strategies for structural regulation to boost the storage capability of Zn2+. We then explore the synchrotron radiation techniques for investigating the microstructure of the designed materials, particularly through in situ synchrotron radiation techniques that can track the dynamic evolution process of the structures. Finally, the summary and future prospects for the further development of cathode materials of AZIBs and advanced synchrotron radiation techniques are discussed.

Phase Engineering and Synchrotron-Based Study on Two-Dimensional Energy Nanomaterials

In recent years, there has been significant interest in the development of two-dimensional (2D) nanomaterials with unique physicochemical properties for various energy applications. These properties are often derived from the phase structures established through a range of physical and chemical design strategies. A concrete analysis of the phase structures and real reaction mechanisms of 2D energy nanomaterials requires advanced characterization methods that offer valuable information as much as possible. Here, we present a comprehensive review on the phase engineering of typical 2D nanomaterials with the focus of synchrotron radiation characterizations. In particular, the intrinsic defects, atomic doping, intercalation, and heterogeneous interfaces on 2D nanomaterials are introduced, together with their applications in energy-related fields. Among them, synchrotron-based multiple spectroscopic techniques are emphasized to reveal their intrinsic phases and structures. More importantly, various in situ methods are employed to provide deep insights into their structural evolutions under working conditions or reaction processes of 2D energy nanomaterials. Finally, conclusions and research perspectives on the future outlook for the further development of 2D energy nanomaterials and synchrotron radiation light sources and integrated techniques are discussed.

Ex Situ Characterization of 1T/2H MoS2 and Their Carbon Composites for Energy Applications, a Review

The growing interest in the development of next-generation net zero energy systems has led to the expansion of molybdenum disulfide (MoS₂) research in this area. This activity has resulted in a wide range of manufacturing/synthesis methods, controllable morphologies, diverse carbonaceous composite structures, a multitude of applicable characterization techniques, and multiple energy applications for MoS₂. To assess the literature trends, 37,347 MoS₂ research articles from Web of Science were text scanned to classify articles according to energy application research and characterization techniques employed. Within the review, characterization techniques are grouped under the following categories: morphology, crystal structure, composition, and chemistry. The most common characterization techniques identified through text scanning are recommended as the base fingerprint for MoS₂ samples. These include: scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Similarly, XPS and Raman spectroscopy are suggested for 2H or 1T MoS₂ phase confirmation. We provide guidance on the collection and presentation of MoS₂ characterization data. This includes how to effectively combine multiple characterization techniques, considering the sample area probed by each technique and their statistical significance, and the benefit of using reference samples. For ease of access for future experimental comparison, key numeric MoS₂ characterization values are tabulated and major literature discrepancies or currently debated characterization disputes are highlighted.

Synchrotron radiation based operando characterization of battery materials

Synchrotron radiation based techniques are powerful tools for battery research and allow probing a wide range of length scales, with different depth sensitivities and spatial/temporal resolutions. Operando experiments enable characterization during functioning of the cell and are thus a precious tool to elucidate the reaction mechanisms taking place. In this perspective, the current state of the art for the most relevant techniques (scattering, spectroscopy, and imaging) is discussed together with the bottlenecks to address, either specific for application in the battery field or more generic. The former includes the improvement of cell designs, multi-modal characterization and development of protocols for automated or at least semi-automated data analysis to quickly process the huge amount of data resulting from operando experiments. Given the recent evolution in these areas, accelerated progress is expected in the years to come, which should in turn foster battery performance improvements.

In situ characterisation for nanoscale structure-performance studies in electrocatalysis

Recently, electrocatalytic reactions involving oxygen, nitrogen, water, and carbon dioxide have been developed to substitute conventional chemical processes, with the aim of producing clean energy, fuels and chemicals. A deepened understanding of catalyst structures, active sites and reaction mechanisms plays a critical role in improving the performance of these reactions. To this end, in situ/operando characterisations can be used to visualise the dynamic evolution of nanoscale materials and reaction intermediates under electrolysis conditions, thus enhancing our understanding of heterogeneous electrocatalytic reactions. In this review, we summarise the state-of-the-art in situ characterisation techniques used in electrocatalysis. We categorise them into three sections based on different working principles: microscopy, spectroscopy, and other characterisation techniques. The capacities and limits of the in situ characterisation techniques are discussed in each section to highlight the present-day horizons and guide further advances in the field, primarily aiming at the users of these techniques. Finally, we look at challenges and possible strategies for further development of in situ techniques.

Synchrotron radiation based X-ray techniques for analysis of cathodes in Li rechargeable batteries

Li-ion rechargeable batteries are promising systems for large-scale energy storage solutions. Understanding the electrochemical process in the cathodes of these batteries using suitable techniques is one of the crucial steps for developing them as next-generation energy storage devices. Due to the broad energy range, synchrotron X-ray techniques provide a better option for characterizing the cathodes compared to the conventional laboratory-scale characterization instruments. This work gives an overview of various synchrotron radiation techniques for analyzing cathodes of Li-rechargeable batteries by depicting instrumental details of X-ray diffraction, X-ray absorption spectroscopy, X-ray imaging, and X-ray near-edge fine structure-imaging. Analysis and simulation procedures to get appropriate information of structural order, local electronic/atomic structure, chemical phase mapping and pores in cathodes are discussed by taking examples of various cathode materials. Applications of these synchrotron techniques are also explored to investigate oxidation state, metal-oxygen hybridization, quantitative local atomic structure, Ni oxidation phase and pore distribution in Ni-rich layered oxide cathodes.

Spatially Resolved Operando Synchrotron-Based X-Ray Diffraction Measurements of Ni-Rich Cathodes for Li-Ion Batteries

Understanding the performance of commercially relevant cathode materials for lithium-ion (Li-ion) batteries is vital to realize the potential of high-capacity materials for automotive applications. Of particular interest is the spatial variation of crystallographic behavior across (what can be) highly inhomogeneous electrodes. In this work, a high-resolution X-ray diffraction technique was used to obtain operando transmission measurements of Li-ion pouch cells to measure the spatial variances in the cell during electrochemical cycling. Through spatially resolved investigations of the crystallographic structures, the distribution of states of charge has been elucidated. A larger portion of the charging is accounted for by the central parts, with the edges and corners delithiating to a lesser extent for a given average electrode voltage. The cells were cycled to different upper cutoff voltages (4.2 and 4.3 V vs. graphite) and C-rates (0.5, 1, and 3C) to study the effect on the structure of the NMC811 cathode. By combining this rapid data collection method with a detailed Rietveld refinement of degraded NMC811, the spatial dependence of the degradation caused by long-term cycling (900 cycles) has also been shown. The variance shown in the pristine measurements is exaggerated in the aged cells with the edges and corners offering an even lower percentage of the charge. Measurements collected at the very edge of the cell have also highlighted the importance of electrode alignment, with a misalignment of less than 0.5 mm leading to significantly reduced electrochemical activity in that area.

Beamline K11 DIAD: a new instrument for dual imaging and diffraction at Diamond Light Source

The Dual Imaging and Diffraction (DIAD) beamline at Diamond Light Source is a new dual-beam instrument for full-field imaging/tomography and powder diffraction. This instrument provides the user community with the capability to dynamically image 2D and 3D complex structures and perform phase identification and/or strain mapping using micro-diffraction. The aim is to enable in situ and in operando experiments that require spatially correlated results from both techniques, by providing measurements from the same specimen location quasi-simultaneously. Using an unusual optical layout, DIAD has two independent beams originating from one source that operate in the medium energy range (7-38 keV) and are combined at one sample position. Here, either radiography or tomography can be performed using monochromatic or pink beam, with a 1.4 mm × 1.2 mm field of view and a feature resolution of 1.2 µm. Micro-diffraction is possible with a variable beam size between 13 µm × 4 µm and 50 µm × 50 µm. One key functionality of the beamline is image-guided diffraction, a setup in which the micro-diffraction beam can be scanned over the complete area of the imaging field-of-view. This moving beam setup enables the collection of location-specific information about the phase composition and/or strains at any given position within the image/tomography field of view. The dual beam design allows fast switching between imaging and diffraction mode without the need of complicated and time-consuming mode switches. Real-time selection of areas of interest for diffraction measurements as well as the simultaneous collection of both imaging and diffraction data of (irreversible) in situ and in operando experiments are possible.

Study of Rechargeable Batteries Using Advanced Spectroscopic and Computational Techniques

Improving the efficiency and longevity of energy storage systems based on Li- and Na-ion rechargeable batteries presents a major challenge. The main problems are essentially capacity loss and limited cyclability. These effects are due to a hierarchy of factors spanning various length and time scales, interconnected in a complex manner. As a consequence, and in spite of several decades of research, a proper understanding of the ageing process has remained somewhat elusive. In recent years, however, combinations of advanced spectroscopy techniques and first-principles simulations have been applied with success to tackle this problem. In this Special Issue, we are pleased to present a selection of articles that, by precisely applying these methods, unravel key aspects of the reduction–oxidation reaction and intercalation processes. Furthermore, the approaches presented provide improvements to standard diagnostic and characterisation techniques, enabling the detection of possible Li-ion flow bottlenecks causing the degradation of capacity and cyclability.