Key to advancing lithium-ion battery technology, and in particular fast charging capabilities, is our ability to follow and understand the dynamic processes occurring in operating materials under realistic conditions, in real time, and on the nano- to meso-scale. Currently, operando imaging of lithium-ion dynamics requires sophisticated synchrotron X-ray or electron microscopy techniques, which do not lend themselves to high-throughput material screening. This limits rapid and rational materials improvements. Here we introduce a simple lab-based, optical interferometric scattering microscope to resolve nanoscopic lithium-ion dynamics in battery materials and apply it to follow the repeated cycling of the archetypical cathode material Li$_\textit{x}$CoO$_2$. The method allows us to visualise directly the insulator-metal, solid solution and lithium ordering phase transitions in this material. We determine rates of lithium insertion and removal at the single-particle level and identify different mechanisms that occur on charge vs. discharge. Finally, we capture the dynamic formation of domain boundaries between different crystal orientations associated with the monoclinic lattice distortion at around Li$_{0.5}$CoO$_2$. The high throughput nature of our methodology allows many particles to be sampled across the entire electrode and, moving forward, will enable exploration of the role of dislocations, morphologies and cycling rate on battery degradation. The generality of our imaging concept means that it can be applied to study any battery electrode, and more broadly, systems where the transport of ions is associated with electronic or structural changes, including nanoionic films, ionic conducting polymers, photocatalytic materials and memristors.
Obtaining a complete picture of local processes still poses a significant challenge in battery research. Here we demonstrate an in-situ combination of multimodal neutron imaging with neutron diffraction for spatially resolved operando observations of the lithiation-delithiation of a graphite electrode in a Li-ion battery cell. Throughout the lithiation-delithiation process we image the Li distribution based on the local beam attenuation. Simultaneously, we observe the development of the lithiated graphite phases as a function of cycling time and electrode thickness and integral throughout its …
Operando Characterization of Volume Changes in Lithium-Ion Battery Electrodes during Cycling using Isotope Multilayers
Clausthal University of Technology（克莱斯特大学）；Clausthal Center for Materials Technology（克莱斯特材料技术中心）；Center for Neutron and Muon Sciences, Paul Scherer Institute（保罗谢勒研究所中子与缪子科学中心）
Operando spectro-ptychography reveals dynamical charge-storage and degradation pathways in redox-active electrodes
Stanford University（斯坦福大学）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；University of California, Los Angeles（加州大学洛杉矶分校）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；University of California, Berkeley（加州大学伯克利分校）
With the importance of Li-ion and emerging alternative batteries to our electric future, predicting new sustainable materials, electrolytes and complete cells that safely provide high performance, long life, energy dense capability is critically important. Understanding interface, microstructure of materials, the nature of electrolytes and factors that affect or limit long term performance are key to new battery chemistries, cell form factors and alternative materials. The electrochemical processes which cause these changes are also difficult to probe because of their metastability and lifetim…
Electrochemical energy systems rely on particulate porous electrodes to store or convert energies. While the three-dimensional porous structures were introduced to maximize the interfacial area for better overall performance of the system, spatiotemporal heterogeneities arose from materials thermodynamics localize the charge transfer processes onto a limited portion of the available interfaces. Here, we demonstrate a simple but precision method that can directly track and analyze the operando (i.e. local and reacting) interfaces at the mesoscale in a practical graphite porous electrode to obta…
Characterizing electrochemical energy conversion devices during operation is an important strategy for correlating device performance with the properties of cell materials under real operating conditions. While operando characterization has been used extensively for low temperature electrochemical cells, these techniques remain challenging for solid oxide electrochemical cells due to the high temperatures and reactive gas atmospheres these cells require. Operando X-ray diffraction measurements of solid oxide electrochemical cells could detect changes in the crystal structure of the cell materi…
Operando pair distribution function analysis of nanocrystalline functional materials: the case of $\mathrm{TiO_{2}}$-bronze nanocrystals in Li-ion battery electrodes
本文提出并应用一个 PDF 分析工具箱，对锂离子电池中 3 nm TiO₂-青铜纳米晶体的非原位与 operando 数据建模，识别原始及嵌锂相并刻画循环中的相演化。
Mapping reaction mechanism during overcharge of a LiNiO2/Graphite-silicon lithium-ion battery: a correlative operando approach by simultaneous gas analysis and synchrotron scattering techniques
Spatially inhomogeneous delithiation in LiNiO2 positive electrode: the effect of X-rays dose
Synchrotron SOLEIL（Soleil 同步辐射光源）；Technische Universität München（慕尼黑工业大学）；Centre National de la Recherche Scientifique, CNRS UR1（法国国家科学研究中心）；Réseau sur le Stockage Electrochimique de l’Energie (RS2E), CNRS FR3459（电化学储能研究网络）；Sorbonne Université, CNRS, Physicochimie des Electrolytes et Nanosystèmes Interfaciaux, CNRS UMR8234（索邦大学）
Unconventional ferroelectricity, robust at reduced nanoscale sizes, exhibited by hafnia-based thin-films presents tremendous opportunities in nanoelectronics. However, the exact nature of polarization switching remains controversial. Here, we investigate epitaxial Hf0.5Zr0.5O2 (HZO) capacitors, interfaced with oxygen conducting metals (La0.67Sr0.33MnO3, LSMO) as electrodes, using atomic resolution electron microscopy while in situ electrical biasing. By direct oxygen imaging, we observe reversible oxygen vacancy migration from the bottom to the top electrode through HZO and reveal associated r…
Understanding (de)lithiation heterogeneities in battery materials is key to ensuring optimal electrochemical performance and developing better energy storage devices. However, this remains challenging due to the complex three dimensional morphology of microscopic electrode particles, the involvement of both solid and liquid phase reactants, and range of relevant timescales (seconds to hours). Here, we overcome this problem and demonstrate the use of bench-top laser scanning confocal microscopy for simultaneous three-dimensional operando measurement of lithium ion dynamics in single particles, …
A novel non-destructive methodology for operando observation of ion intercalation and the state of charge on battery electrodes is presented based on spectroscopic ellipsometry (SE). The potentiality of this technique for performing time-resolved measurements of (de-)lithiation processes on electrode materials has been demonstrated using thin film spinel LiMn$_2$O$_4$ as a cathode for Li-ion batteries. The chemical diffusivity of Li+ ions in this material has been determined by the time evolution of the Li insertion into the film, and in the light of these results, it has been possible to rela…
Insights on the volume variation of LiCoxMn2-xO4 electrode upon cycling: a correlative operando XRD and XAS study
Sorbonne Université, CNRS, Physicochimie des Electrolytes et Nanosystèmes interfaciaux (PHENIX)（索邦大学，法国国家科学研究中心，电解质与界面纳米系统物理化学）；Sorbonne Université, CNRS, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP)（索邦大学，法国国家科学研究中心，巴黎凝聚态物质化学实验室）；Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459（电化学储能研究网络（RS2E），FR CNRS 3459）
Autonomous battery research: Principles of heuristic operando experimentation
ISIS Neutron & Muon Source, Rutherford Appleton Laboratory（ISIS中子与穆子源、拉瑟福德-苹果顿实验室）；The Faraday Institution（法拉第机构）；Diamond Light Source, Rutherford Appleton Laboratory（Diamond光源、拉瑟福德-苹果顿实验室）；University of Cambridge, The Old Schools, Trinity Ln（剑桥大学、旧校舍、三一街）；Imperial College London, Department of Mechanical Engineering（伦敦帝国理工学院、机械工程系）
Non-destructive determination of lithium distribution in a working battery is key for addressing both efficiency and safety issues. Although various techniques have been developed to map the lithium distribution in electrodes, these methods are mostly applicable to test cells. Here we propose the use of high-energy x-ray Compton scattering spectroscopy to measure the local lithium concentration in closed electrochemical cells. A combination of experimental measurements and parallel first-principles computations is used to show that the shape parameter S of the Compton profile is linearly propo…
Phosphorus is one of the most promising anodes for sodium ion batteries (SIBs). Little is known about the structural mechanism of Na/P cycling due to the fact that only one of the structures involved (Na3P) is crystalline. Using operando X-ray diffraction computed tomography (XRD-CT) analysed by Rietveld and pair distribution (PDF) methods combined with density functional theory (DFT) calculations we show that the sodiation and desodiation mechanisms of phosphorus are very different. Sodiation follows the thermodynamic path of lowest energy from P via NaP to Na3P while desodiation follows a ki…
Here, we correlate the nanoscale morphology and chemical composition of solid electrolyte interphases (SEI) with the electrochemical property of graphite-based composite electrodes. Using electrochemical strain microscopy (ESM) and X-ray photoelectron spectroscopy (XPS), changes of chemical composition and morphology (Li and F distribution) in SEI layers on the electrodes as a function of solid electrolyte contents are analyzed. As a result, we find a strong correlation between morphological variations on the electrode, Li and F distribution in SEI layer, and Coulomb efficiency. This correlati…
This report presents some of the key laboratory electrochemical battery testing methods that are used in fuel cell research. Methods such as voltammetry, chronoamperometry, chronopotentiometry, and electrochemical impedance spectroscopy are of major importance. All the electrochemical corrosion tests are performed through a tri-electrode polarization cell setup containing a reference electrode, a counter electrode, and the working electrode (metal sample of interest) in an electrolyte solution. All three electrodes are connected to a potentiostat. Corrosion of metal occurs through an oxidation…
The overpotential, dissociation rate, electrode potential distributions and current density are suggested in this study to analyze the Nickel Vanadium Redox Flow Battery (NVRFB). Due to its large capacity and ecofriendly properties, NVRFB may be a viable option in the present state of energy constraint and environmental pollution. Due to their low cost and high energy density, nickel-based flow batteries have gained popularity. This study demonstrates that the Ni2+/Ni+ and V5+/V4+ ions have a higher rate of dissociation at the membrane and a lower rate at the inlet, where the electrolyte flow …
Poor electrical conductivity and large volume expansion during repeated charge and discharge is what has characterized many battery electrode materials in current use. This has led to 2D materials, specifically multi-layered 2D systems, being considered as alternatives. Among these 2D multi-layered systems are the graphene-based van der Waals heterostructures with transition metal di-chalcogenides (TMDCs) as one of the layers. Thus in this study, graphene-Hafnium disulphide (Gr-HfS$_2$) system, has been investigated as a prototype Gr-TMDC system for application as battery electrode. Density fu…
Development of materials for electrochemical energy conversion requires a deep understanding of the factors governing chemical and physical rates at submicron length scales. Many workers have sought to develop chemically sensitive in situ or operando imaging techniques targeting these length scales. However, current methods focus on steady-state or stepwise response. To probe electrode processes both spatially and temporally, we have developed a frequency-resolved implementation of X-ray absorption imaging (FR-XAS) that can measure local electrochemical response in operando during a global sin…
Natural abundance of sodium and its similar behavior to lithium triggered recent extensive studies of cost-effective sodium-ion batteries (SIBs) for large-scale energy storage systems. A challenge is to develop electrode materials with a high electrode potential, specific capacity and a good rate capability. In this work we propose mixed eldfellite compounds \ce{Na_x(Fe_{1/2}M_{1/2})(SO4)2} (M = Mn, Co, Ni) as a new family of high electrode potential cathodes of SIBs and present their material properties predicted by first-principles calculations. The structural optimizations show that these m…
Metal fluoride and oxides can store multiple lithium-ions through conversion chemistry to enable high energy-density lithium-ion batteries. However, their practical applications have been hindered by an unusually large voltage hysteresis between charge and discharge voltage-profiles and the consequent low energy efficiency (< 80%). The physical origins of such hysteresis are rarely studied and poorly understood. Here we employ in situ X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM), density-functional-theory (DFT) calculations, and galvanostatic intermittent titrati…
Lithium titanium oxide Li$_4$Ti$_5$O$_{12}$ (LTO) is an intriguing anode material promising particularly long lived batteries, due to its remarkable phase stability during (dis)charging of the cell. However, its usage is limited by its low intrinsic electronic conductivity. Introducing oxygen vacancies can be one method to overcome this drawback, possibly by altering the charge carrier transport mechanism. We use Hubbard corrected density-functional theory (DFT+U) to show that polaronic states in combination with a possible hopping mechanism can play a crucial role in the experimentally observ…
A simulation model and design of Titanium Manganese Redox Flow Battery (TMRFB) is proposed to study the distribution of dissociation rate, overpotential, current density, and electrode potential. TMRFB is one of the most promising new energy storages because of its high capacity and eco-friendly characteristics in the current condition of energy scarcity and environmental pollution. Moreover, Mn-based flow batteries are gaining popularity due to their inexpensive cost and high energy density in lieu of all vanadium redox flow batteries which are expensive. This research shows that the surface …
A significant problem associated with batteries is the rapid reduction of charge-storage capacity with increasing charge/discharge rate. For example, improving this rate-performance is required for fast-charging of car batteries. Rate-performance is related to the timescales associated with charge or ionic motion in both electrode and electrolyte. However, no quantitative model exists which can be used to fit experimental data to give insights into the dominant rate-limiting processes in a given electrode-electrolyte system. Here we develop an equation which can be used to fit capacity versus …
A Physics-Regularized Neural Network and Kirchhoff Markov Random Field Framework for Inferring Internal Electrochemical States from Operando Spectromicroscopy
The University of Tokyo（东京大学）；Tohoku University（东北大学）；Kumamoto University（熊本大学）
Smoothed Boundary Method Framework for Electrochemical Simulation of Li-ion Battery Cathode with Complex Microstructure: Model, Formulation and Parameterization
Fracture of lithium-ion battery electrodes is found to contribute to capacity fade and reduce the lifespan of a battery. Traditional fracture models for batteries are restricted to consideration of a single, idealised particle; here, advanced X-ray computed tomography (CT) imaging, an electro-chemo-mechanical model and a phase field fracture framework are combined to predict the void-driven fracture in the electrode particles of a realistic battery electrode microstructure. The electrode is shown to exhibit a highly heterogeneous electrochemical and fracture response that depends on the partic…
Identifying overpotential components of electrochemical systems enables quantitative analysis of polarization contributions of kinetic processes under practical operating conditions. However, the inherently coupled kinetic processes lead to an enormous challenge in measuring individual overpotentials, particularly in composite electrodes of lithium-ion batteries. Herein, the full decomposition of electrode overpotential is realized by the collaboration of single-layer structured particle electrode (SLPE) constructions and time-resolved potential measurements, explicitly revealing the evolution…
Adding porosity to battery electrodes is believed to be universally useful for adding space to accommodate volumetric expansion, electrolyte access to all active materials, helping to mitigate poor C-rate performance for thicker electrodes and for allowing infilling with other materials. Ordered porous electrode, such as inverse opals that have macroporosity, have been a model system: binder and conductive additive free, interconnected electrically, defined porosity and pore size with thickness, good electrolyte wettability and surprisingly good electrode performance in half cells and Li-batte…
Recent years have seen a rapidly escalating demand for battery technologies capable of storing more energy, charging more quickly and having longer usable lifetimes, driven largely by increased electrification of transport and by grid-scale energy storage systems. This has led to the development of many promising new electrode materials for high-rate lithium ion batteries. In order to rationalise and improve upon material performance, it is crucial to understand the fundamental ion-intercalation and degradation mechanisms occurring during realistic battery operation, on the nano- to meso-scale…
Battery electrode surfaces are generally coated with electronically insulating solid films of thickness 1-50 nm. Both electrons and Li+ can move at the electrode-surface film interface in response to the voltage, which adds complexity to the "electric double layer" (EDL). We apply Density Functional Theory (DFT) to investigate how the applied voltage is manifested as changes in the EDL at atomic lengthscales, including charge separation and interfacial dipole moments. Illustrating examples include Li(3)PO(4), Li(2)CO(3), and Li(x)Mn(2)O(4) thin-films on Au(111) surfaces under ultrahigh vacuum …
The improvement of Li-ion battery performance requires development of models that capture the essential physics and chemistry in Li-ion battery electrode materials. In this paper a novel electrochemical phase-field model is presented that captures the thermodynamic and kinetic properties of lithium-insertion in TiO$_2$-anatase, a well-known and intensively studied Li-ion battery electrode material. Previous experimental work on lithiated anatase TiO$_2$ provided all parameters necessary for the phase-field simulations, giving the opportunity to gain fundamental insight in the lithiation of ana…
Benefited from the advantages on environmental benign, easy purification, and high thermal stability, the recently synthesized two-dimensional (2D) material MoN2 shows great potential for clean and renewable energy applications. Here, through first-principles calculations, we show that the monolayered MoN2 is promising to be a high capacity electrode material for metal ion batteries. Firstly, identified by phonon dispersion and exfoliation energy calculations, MoN2 monolayer is proved to be structurally stable and could be exfoliated from its bulk counterpart in experiments. Secondly, all the …
While it is well-known that electrode conductivity has a critical impact on rate-performance in battery electrodes, this relationship has been quantified only by computer simulations. Here we investigate the relationship between electrode conductivity and rate-performance in Lithium-Nickel-Manganese-Cobalt-Oxide (NMC) cathodes filled with various quantities of carbon black, single-walled carbon nanotubes and graphene. The electrode conductivity is always extremely anisotropic with the out-of-plane conductivity, which is most relevant to rate-performance, roughly 1000 smaller than the in-plane …
Based on first-principles calculations and symmetry analysis, we report that the three-dimensional (3D) nodal line (NL) semimetal phases can be realized in the lead dioxide family (\emph{$α$}-PbO$_2$ and \emph{$β$}-PbO$_2$) and its derivatives. The \emph{$β$}-PbO$_2$ features two orthogonal nodal rings around the Fermi level, protected by the mirror reflection symmetry. The effective model is developed and the related parameters are given by fitting with the HSE06 band structures. The NLs mainly come from the $p$ orbitals of the light element O and are rather robust against such tiny spin-orbi…
To study the electrochemical reaction on surfaces, phase interfaces, and crack surfaces in the lithium ion battery electrode particles, a phase-field model is developed, which describes fracture in large strains and anisotropic Cahn-Hilliard-Reaction. Thereby the concentration-dependency of the elastic properties and the anisotropy of diffusivity are also considered. The implementation in 3D is carried out by isogeometric finite element methods in order to treat the high order terms in a straightforward sense. The electrochemical reaction is modeled through a modified Butler-Volmer equation to…
Direct Evidence of Metal-Ligand Redox in Li-ion Battery Positive Electrodes
WMG, University of Warwick（华威大学WMG学院）；The Faraday Institution（法拉第研究所）；School of Science and Engineering, University of Dundee（邓迪大学科学与工程学院）；School of Metallurgy and Materials, University of Birmingham（伯明翰大学冶金与材料学院）；University College Dublin（都柏林大学学院）；Max Planck Institute for Solid State Research（马克斯·普朗克固体研究所）
