Multi-Scale Correlative Tomography of a Li-Ion Battery Composite Cathode

Advances in Focused Ion Beam Tomography for Three-Dimensional Characterization in Materials Science

Over the years, FIB-SEM tomography has become an extremely important technique for the three-dimensional reconstruction of microscopic structures with nanometric resolution. This paper describes in detail the steps required to perform this analysis, from the experimental setup to the data analysis and final reconstruction. To demonstrate the versatility of the technique, a comprehensive list of applications is also summarized, ranging from batteries to shale rocks and even some types of soft materials. Moreover, the continuous technological development, such as the introduction of the latest models of plasma and cryo-FIB, can open the way towards the analysis with this technique of a large class of soft materials, while the introduction of new machine learning and deep learning systems will not only improve the resolution and the quality of the final data, but also expand the degree of automation and efficiency in the dataset handling. These future developments, combined with a technique that is already reliable and widely used in various fields of research, are certain to become a routine tool in electron microscopy and material characterization.

Controlling Binder Adhesion to Impact Electrode Mesostructures and Transport

The complex three-phase composition of lithium-ion battery electrodes, containing an ion-conducting pore phase, a nanoporous electron-conducting carbon binder domain (CBD) phase, and an active material (AM) phase, provides several avenues of mesostructural engineering to enhance battery performance. We demonstrate a promising strategy for engineering electrode mesostructures by controlling the strength of adhesion between the AM and CBD phases. Using high-fidelity, physics-based colloidal and granular dynamics simulations, we predict that this strategy can provide significant control over electrochemical transport-relevant properties such as ionic conductivity, electronic conductivity, and available AM-electrolyte interface area. Importantly, the proposed strategy could be experimentally realized through surface functionalization of the AM and CBD phases and would be compatible with traditional electrode manufacturing methods.

Multiscale Tomographic Analysis for Micron-Sized Particulate Samples

The three-dimensional characterization of distributed particle properties in the micro- and nanometer range is essential to describe and understand highly specific separation processes in terms of selectivity and yield. Both performance measures play a decisive role in the development and improvement of modern functional materials. In this study, we mixed spherical glass particles (0.4–5.8 μm diameter) with glass fibers (diameter 10 μm, length 18–660 μm) to investigate a borderline case of maximum difference in the aspect ratio and a significant difference in the characteristic length to characterize the system over several size scales. We immobilized the particles within a wax matrix and created sample volumes suitable for computed tomographic (CT) measurements at two different magnification scales (X-ray micro- and nano-CT). Fiber diameter and length could be described well on the basis of the low-resolution micro-CT measurements on the entire sample volume. In contrast, the spherical particle system could only be described with sufficient accuracy by combining micro-CT with high-resolution nano-CT measurements on subvolumes of reduced sample size. We modeled the joint (bivariate) distribution of fiber length and diameter with a parametric copula as a basic example, which is equally suitable for more complex distributions of irregularly shaped particles. This enables us to capture the multidimensional correlation structure of particle systems with statistically representative quantities.

Quantitative spatially resolved post-mortem analysis of lithium distribution and transition metal depositions on cycled electrodes via a laser ablation-inductively coupled plasma-optical emission spectrometry method

Diminishing the loss of performance of lithium ion batteries (LIBs) is a challenge that is yet to be fulfilled. Understanding of deterioration processes and mechanisms (i.e., so-called aging) requires analytically accurate examination of aged cells. Changes in the distribution of lithium or transition metals in the LIB cells can influence their cycle and calendar life significantly. As electrochemically treated cells and especially their electrodes do not age homogeneously and the local electrochemistry (e.g. deposition patterns) is strongly dependent on surface properties, bulk analysis is not a satisfactory investigation method. Therefore, a surface sensitive method, namely laser ablation-inductively coupled plasma-optical emission spectrometry (LA-ICP-OES) is presented. LIB cells with lithium metal oxide LiNi_1/3Co_1/3Mn_1/3O₂ (NCM111) as cathode material and graphite as anode material are investigated using a 213 nm Nd:YAG laser.

An LA-ICP-OES method was developed and applied to investigate the transition metal dissolution in lithium batteries as well as lithium deposition e.g. in case of short circuits.

Three-Dimensional Microstructure of ε-Fe2O3 Crystals in Ancient Chinese Sauce Glaze Porcelain Revealed by Focused Ion Beam Scanning Electron Microscopy

Ancient Chinese sauce glaze porcelain has recently received growing attention for the discovery of epsilon iron oxide (ε-Fe₂O₃) crystals in glaze. In this work, we first confirm the presence of ε-Fe₂O₃ microcrystals, in large quantiteis, in sauce glaze porcelain fired at the Qilizhen kiln in Jiangxi province during the Southern Song dynasty. We then employed focused ion beam scanning electron microscopy (FIB-SEM) to investigate the three-dimensional microstructure of ε-Fe₂O₃ microcrystals, which revealed three well-separated layers (labeled, respectively, as LY1, LY2, and LY3 from the glaze surface to inside) under the glaze surface. Specifically, LY1 consists of well-defined dendritic fractal structure with high ordered branches at micrometers scale, LY2 has spherical or irregular-shaped particles at nanometers scale, while LY3 consists of dendrites with four, six, or eight primary branches ranging from several nanometers to around 1 μm. Given these findings, we proposed a process for the possible growth of ε-Fe₂O₃ microcrystals in ancient Chinese sauce glaze.

Quantitative synchrotron X-ray tomography of the material-tissue interface in rat cortex implanted with neural probes

Neural probes provide many options for neuroscientific research and medical purposes. However, these implantable micro devices are not functionally stable over time due to host-probe interactions. Thus, reliable high-resolution characterization methods are required to understand local tissue changes upon implantation. In this work, synchrotron X-ray tomography is employed for the first time to image the interface between brain tissue and an implanted neural probe, showing that this 3D imaging method is capable of resolving probe and surrounding tissue at a resolution of about 1 micrometer. Unstained tissue provides sufficient contrast to identify electrode sites on the probe, cells, and blood vessels within tomograms. Exemplarily, we show that it is possible to quantify characteristics of the interaction region between probe and tissue, like the blood supply system. Our first-time study demonstrates a way for simultaneous 3D investigation of brain tissue with implanted probe, providing information beyond what was hitherto possible.

3D high resolution imaging for microelectronics: A multi-technique survey on copper pillars

In microelectronics, recently developed 3D integration offers the possibility to stack the dice or wafers vertically instead of putting their different parts next to one another, in order to save space. As this method becomes of greater interest, the need for 3D imaging techniques becomes higher. We here report a study about different 3D characterization techniques applied to copper pillars, which are used to stack different dice together. Destructive techniques such as FIB/SEM, FIB/FIB, and PFIB/PFIB slice and view protocols have been assessed, as well as non-destructive ones, such as laboratory-based and synchrotron-based computed tomographies. A comparison of those techniques in the specific case of copper pillars is given, taking into account the constraints linked to the microelectronics industry, mainly concerning resolution and sample throughput. Laboratory-based imaging techniques are shown to be relevant in the case of punctual analyses, while synchrotron based tomographies offer highly resolved volumes for larger batches of samples.

Quantification and modeling of mechanical degradation in lithium-ion batteries based on nanoscale imaging

Capacity fade in lithium-ion battery electrodes can result from a degradation mechanism in which the carbon black-binder network detaches from the active material. Here we present two approaches to visualize and quantify this detachment and use the experimental results to develop and validate a model that considers how the active particle size, the viscoelastic parameters of the composite electrode, the adhesion between the active particle and the carbon black-binder domain, and the solid electrolyte interphase growth rate impact detachment and capacity fade. Using carbon-silicon composite electrodes as a model system, we demonstrate X-ray nano-tomography and backscatter scanning electron microscopy with sufficient resolution and contrast to segment the pore space, active particles, and carbon black-binder domain and quantify delamination as a function of cycle number. The validated model is further used to discuss how detachment and capacity fade in high-capacity materials can be minimized through materials engineering.

Three-Dimensional Reconstruction and Analysis of All-Solid Li-Ion Battery Electrode Using Synchrotron Transmission X-ray Microscopy Tomography

A synchrotron transmission X-ray microscopy tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source was employed to obtain three-dimensional morphological data of all-solid Li-ion battery electrodes. The three-phase electrode was fabricated from a 47:47:6 (wt %) mixture of Li(Ni_1/3Mn_1/3Co_1/3)O₂ as active material, Li_1.3Ti_1.7Al_0.3(PO₄)₃ as Li-ion conductor, and Super-P carbon as electron conductor. The geometric analysis show that particle-based all-solid Li-ion battery has serious contact interface problem which significantly impact the Li-ion transport and intercalation reaction in the electrode, leading to low capacity, poor rate capability and cycle life.

Carbon Nanotube Web with Carboxylated Polythiophene "Assist" for High-Performance Battery Electrodes

A carbon nanotube (CNT) web electrode comprising magnetite spheres and few-walled carbon nanotubes (FWNTs) linked by the carboxylated conjugated polymer, poly[3-(potassium-4-butanoate) thiophene] (PPBT), was designed to demonstrate benefits derived from the rational consideration of electron/ion transport coupled with the surface chemistry of the electrode materials components. To maximize transport properties, the approach introduces monodispersed spherical Fe₃O₄ (sFe₃O₄) for uniform Li⁺ diffusion and a FWNT web electrode frame that affords characteristics of long-ranged electronic pathways and porous networks. The sFe₃O₄ particles were used as a model high-capacity energy active material, owing to their well-defined chemistry with surface hydroxyl (-OH) functionalities that provide for facile detection of molecular interactions. PPBT, having a π-conjugated backbone and alkyl side chains substituted with carboxylate moieties, interacted with the FWNT π-electron-rich and hydroxylated sFe₃O₄ surfaces, which enabled the formation of effective electrical bridges between the respective components, contributing to efficient electron transport and electrode stability. To further induce interactions between PPBT and the metal hydroxide surface, polyethylene glycol was coated onto the sFe₃O₄ particles, allowing for facile materials dispersion and connectivity. Additionally, the introduction of carbon particles into the web electrode minimized sFe₃O₄ aggregation and afforded more porous FWNT networks. As a consequence, the design of composite electrodes with rigorous consideration of specific molecular interactions induced by the surface chemistries favorably influenced electrochemical kinetics and electrode resistance, which afforded high-performance electrodes for battery applications.