Improving battery materials calls for nondestructive techniques capable of delivering high-resolution microstructural information in real time. In this context, X-ray phase contrast nano-tomography is a technique of choice as it enables multiscale 3D characterization. In this study, we propose a feedback loop-integrated workflow for X-ray nano-tomography, based on systematic evaluation of six state-of-the-art battery anode and cathode materials to benchmark key procedures ensuring reliable, reproducible, quality-assessed characterization and subsequent 3D morphological quantification, thus avoiding potential bias in the scientific conclusions. As a result for this phase contrast technique, the sample size and energy used appear as key factors for the final resolution, which enhances imaging capabilities for separating the different material phases of the electrode microstructures. But, it is crucial to adapt these parameters to the materials in order to mitigate errors in the morphological parameter estimation. Moreover, an empirical law based on the heterogeneity and the average particle size distribution has been established to calculate the minimum representative elementary volume to be imaged, showing that volumes of 102 × 102 × 102 μm3 (50 nm voxel size) are sufficiently representative for the six microstructures studied. Ultimately, guidelines have been established for in situ/operando X-ray nano-tomography measurements, with a proposed/validated in-house setup and cell design that preserve both the image resolution and electrochemistry. A detailed evaluation of the X-ray beam interaction is also presented, exploring the relationship between the dose received by the electrolyte and material and the reliable monitoring of electrochemistry and tomography.

The simple addition of a Zn(II) precursor to a preoptimized poly(carboxylic acid) binder solution enhances the electrochemical performance and cycle life of silicon-based electrodes. The binder/cation couple forms a cross-linked coordinated binder that plays a key role in enhancing the mechanical and chemical stability of the electrode microstructure. The impact of the addition of the Zn precursor on the microstructural evolution of the electrode during cycling is investigated at different scales (from cell/electrode to silicon particle scale) using complementary operando, in situ, and ex situ X-ray tomography techniques. Comparative analyses conducted on the reference and with Zn electrode formulations using operando and in situ X-ray micro-tomography allow for monitoring of the electrode morphological deformations along with the crack pattern formation and evolution during cycling. The benefits of the precursor addition include enhancing the mechanical stability of the electrode through a strengthened microstructure more apt to maintaining its integrity, as well as a better anchoring to the current collector leading to decreased electrical disconnections and capacity fade. Moreover, complementary ex situ X-ray nano-tomography measurements highlight the benefits of the precursor addition in terms of chemical stability with mitigated solid electrolyte interface (SEI) formation over the electrode cycling. The benefits of a simple, yet efficient, method to boost the mechanical and chemical stability of Si-based electrode microstructure through the addition of a Zn(II) precursor to a carboxylic binder is demonstrated thanks to a cross-correlated multiscale workflow based on operando/in situ and ex situ X-ray tomography analyses. image

Non-destructive 3D imaging techniques, such as X-ray nano-holo-tomography, enable the visualization of battery electrodes. Segmenting electrodes into distinct phases is crucial for a comprehensive analysis, yet the process of precise annotation is very labor-intensive. To address this challenge, deep learning methods have been leveraged for automation. However, acquiring a sufficiently large dataset for training deep neural networks that are widely usable remains impractical. A model that is applicable within a dataset but requires very limited human effort to build and use is a viable direction. We propose an active learning framework operating in a semi-supervised setting that minimizes the annotations required by identifying informative training samples at the pixel level. Our approach achieves accuracy comparable to models trained on complete datasets, while utilizing a mere 4% of the data. We demonstrate the effectiveness of our method through a quantitative analysis involving lithium nickel oxide (LNO) electrodes and a user study focusing on graphite electrodes. Our results underscore the potential of active learning to streamline data analysis through efficient model training.

A crucial step in the production of battery grade natural graphite for lithium-ion batteries is the spheroidization process. However, the spheroidization yield is typically only about 50%. The by-product consists of graphite fines that are not suitable for use in lithium-ion batteries due to their small particle size (<10 mu m), therefore, graphite fines are discarded or sold at a loss. In this work, we report a method for graphite fines re-agglomeration and petroleum pitch coating that allows for revalorization and recycling of waste graphite from the spheroidization process. Re-agglomeration of graphite fines was achieved by spray drying technique using carboxymethyl cellulose as binder and citric acid as cross-linking agent to improve the mechanical strength of the agglomerate. The as-obtained particles were subjected to heat treatment in presence of petroleum pitch for simultaneous binder and pitch decomposition to obtain pitch-coated particles. Resulting agglomerate particles showed a median size comparable to a commercial battery grade natural graphite reference and proved structurally sound to withstand the electrode calendering process. Pitch-coated agglomerate particles exhibited lower surface area and improved stability in comparison with non-coated graphite agglomerate. The electrochemical performance of the coated material was comparable to a commercial graphite reference, particularly in terms of cumulative irreversible capacity. Analysis by X-ray nano-computed tomography provided further insight into morphological properties and dimensional changes after calendering and upon galvanostatic cycling. Overall, the material obtained through this method shows great potential for re-introduction in the production chain of battery grade natural graphite for lithium-ion batteries.

Li-ion battery cathode active materials obtained from different sources or preparation methods often exhibit broadly divergent performance and stability despite no obvious differences in morphology, purity, and crystallinity. We show how state-of-the-art, commercial, nominally single crystalline LiNi0.6Mn0.2Co0.2O2 (NMC-622) particles possess extensive internal nanostructure even in the pristine state. Scanning X-ray diffraction microscopy reveals the presence of interlayer strain gradients, and crystal bending is attributed to oxygen vacancies. Phase contrast X-ray nano-tomography reveals two different kinds of particles, welded/aggregated, and single crystal like, and emphasizes the intra- and interparticle heterogeneities from the nano- to the microscale. It also detects within the imaging resolution (100 nm) substantial quantities of nanovoids hidden inside the bulk of two-thirds of the overall studied particles (around 3000), with an average value of 12.5%v per particle and a mean size of 148 nm. The powerful combination of both techniques helps prescreening and quantifying the defective nature of cathode material and thus anticipating their performance in electrode assembly/battery testing.

Li-O2 batteries (LOB) performance degradation ultimately occurs through the accumulation of discharge products and irreversible clogging of the porous electrode during the cycling. Electrode binder degradation in the presence of reduced oxygen species can result in additional coating of the conductive surface, exacerbating capacity fading. Herein, a facile method to fabricate free-standing is established, binder-free electrodes for LOBs in which multi-wall carbon nanotubes form cross-linked networks exhibiting high porosity, conductivity, and flexibility. These electrodes demonstrate high reproducibility upon cycling in LOBs. After cell death, efficient and inexpensive methods to wash away the accumulated discharge products are demonstrated, as reconditioning method. The second life usage of these electrodes is validated, without noticeable loss of performance. These findings aim to assist in the development of greener high energy density batteries while reducing manufacturing and recycling costs.

Understanding the degradation pathways of electrode materials is a key to develop more reliable Li-ion technologies along with an increased energy density and power rate. This study aims to demonstrate the benefits of the combined use of X-ray based characterization techniques and electrochemical assessment for thorough multi-scale analysis to elucidate the aging mechanisms of a Li4Ti5O12/AC//LiMn2O4/AC parallel hybrid lithium-ion supercapacitor. Analyses performed on samples extracted from full stack representative of industrial battery application, show that irreversible modifications are observed at all length scales on both electrodes. At the negative, the disaggregation and corrosion of the LTO active material, as well as AC particle cracking and electrode film delamination have been observed. In the meantime, drastic cracking of the AC and LMO active material along with important micro-strain increase at the crystallite level for LMO as well as Mn3+ dissolution are reported at the positive. The formation of a cathode electrolyte interface (CEI) is also reported. These structural and chemical changes have been identified as precursors to important polarization increase, Li inventory loss and furthermore capacity fading leading thus to device failure.

The recent rapid increase of the demand of higher energy density along with higher power density lithium-ion batteries (LiBs) requires the development of advanced cathode/anode materials with higher capacity. These challenges can be addressed providing that powerful characterization tools are able to probe the degradation phenomena occurring at multiple scale. In this context, the TEESMAT platform aims to widen the access to a large panel of characterization techniques among different partners across Europe for solving industrial problematics in energy related field. Among these, X-ray tomography has been used as non-invasive 3D investigation tool that spread along a wide range of applications in order to probe at different length scale their microstructure. Moreover, phase contrast imaging has brought to light a practical way to enhance visibility between weak absorbing materials and/or small details of differing refractive index within structure, and thus accessing a sharpen overview of the 3D morphology of complex material, which is of particular interest in the frame of energy-related materials. This presentation will focus on various industrial case studies such as NMC-based and LFP-based all solid-state batteries, hybrid Li-ion supercapacitor and current collector manufacturing. The results presented are part of the TEESMAT project, which received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 814106.

Journal Article Synchrotron Holotomography on Silicon-Based Anode Materials for Improved Lithium Ion Batteries Get access Fereshteh Falah Chamasemani, Fereshteh Falah Chamasemani Materials Center Leoben Forschung GmbH, Leoben, Styria, Austria Corresponding author: fereshteh.falah@mcl.at Search for other works by this author on: Oxford Academic Google Scholar Michael Häusler, Michael Häusler Materials Center Leoben Forschung GmbH, Leoben, Styria, Austria Search for other works by this author on: Oxford Academic Google Scholar Thomas Vorauer, Thomas Vorauer Materials Center Leoben Forschung GmbH, Leoben, Styria, Austria Search for other works by this author on: Oxford Academic Google Scholar Guilhem Paradol, Guilhem Paradol IRIG-SyMMES/CEA, Grenoble, Auvergne-Rhône-Alpes, France Search for other works by this author on: Oxford Academic Google Scholar Alice Robba, Alice Robba IRIG-SyMMES/CEA, Grenoble, Auvergne-Rhône-Alpes, France Search for other works by this author on: Oxford Academic Google Scholar Victor Vanpeene, Victor Vanpeene European Synchrotron Radiation Facility, Grenoble, Auvergne-Rhône-Alpes, France Search for other works by this author on: Oxford Academic Google Scholar Bernd Fuchsbichler, Bernd Fuchsbichler VARTA Innovation GmbH, Graz, Styria, Austria Search for other works by this author on: Oxford Academic Google Scholar Claire Villevieille, Claire Villevieille Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP, LEPMI, Grenoble, France Search for other works by this author on: Oxford Academic Google Scholar Sandrine Lyonnard, Sandrine Lyonnard IRIG-SyMMES/CEA, Grenoble, Auvergne-Rhône-Alpes, France Search for other works by this author on: Oxford Academic Google Scholar Roland Brunner Roland Brunner Materials Center Leoben Forschung GmbH, Leoben, Styria, Austria Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 200–202, https://doi.org/10.1017/S1431927622001672 Published: 01 August 2022

Abstract The conception of cheaper and greener electrode materials is critical for lithium (Li)‐ion battery manufacturers. In this study, a by‐product of the carbothermic reduction of SiO2 to Si, containing 65 wt% Si, 31 wt% SiC, and 4 wt% C, is evaluated as raw material for the production of high‐capacity anodes for Li‐ion batteries. After 20 h of high‐energy ball milling, C is fully converted to SiC and a micrometric powder (D50 ∼1 μm) is obtained in which submicrometric SiC inclusions are embedded in a nanocrystalline/amorphous Si matrix. This material is able to maintain a capacity >1000 mAh g−1 (>3 mAh cm−2) over 100 cycles. No crystalline Li15Si4 phase is formed upon cycling as shown from the differential dQ/dV curves. The good mechanical resiliency of the electrode is evidenced by monitoring its morphological changes from sequential focused ion beam scanning electron microscopy analyses. However, a progressive and irreversible increase in the electrode mass and thickness is observed over cycling (reaching 125% and 60% after 200 cycles, respectively), which is mainly attributed to the accumulation of solid electrolyte interphase products in the electrode.

The past decade faced with rapid development of electric vehicles, portable electronic devices and green energy production, in which lithium-ion batteries (LiBs) technology plays a key role. In this context, extensive research has been made for increasing their energy density along with power density. This challenge requires pushing forward the resolution limits to probe degradation phenomena occurring at the active material level for a deeper understanding of the batter failure mechanism. In this context, X-ray techniques have been intensively used to probe in details the morphological/chemical evolution along cycling of various battery materials. For instance, X-ray computed tomography brings valuable 3D information for material structural analysis at scale ranging from the micrometre to the nanometre. High flux and high coherent X-ray nano-beams provided by the synchrotron sources, combined with the fast acquisition obtained thanks to the new generation of cMOS detectors, make it possible to carry out in situ and operando measurements at the nano-scale to 3D monitor dynamic phenomena. These developments present a real interest for the energy storage applications. This presentation will focus on the hard X-ray nano-tomography set-up developed at the ID16B beamline of the ESRF and its applications toward operando measurements applied to different case studies related to energy materials. This will be discussed as well in regards to the benefits and limitations brought by the extremely brilliant X-ray source EBS developed at the ESRF.

The conception of cheaper and greener electrode materials is critical for Li-ion battery manufacturers. In this study, it is shown that a by-product of the carbothermic reduction of SiO2 to Si, containing Si, SiC and C materials, can be valorized as a low-cost and high-capacity anode material for Li-ion batteries after an appropriate high-energy ball milling treatment. The latter results in the production of a micrometric powder (D50 ~1 mm) in which submicrometric SiC inclusions are embedded in a nanocrystalline/amorphous Si matrix. Such a microstructure prevents the deleterious formation of c-Li15Si4 phase, which is well known to accentuate particle cracking. As a result, the electrode is able to maintain a capacity >1000 mAh g-1 (>3 mAh cm-2) over 100 cycles. Moreover, calendering has no negative impact on the electrode performance. However, a significant and irreversible increase of the electrode mass and thickness was observed over cycling, which is mainly attributed to the accumulation of SEI products. In order to have deeper insights into the microstructural evolution of the electrode during cycling, a focused ion beam (FIB) milled microcavity (45×20×50 µm3) was created in the center of the pristine electrode. This cavity was observed by SEM at different cycling periods of a single electrode (Fig. 1a). This investigation method allows following the same electrode along different steps of its cycling, nearly as for an in-situ method. Additionally, backscattered-electron (BSE) imaging was performed on broad ion beam (BIB) polished cross-section of the electrode after different periods of cycling (Fig. 1b). The morphological change is characterized at the electrode and particle scales by monitoring the thickness, mass, porosity and macrocracking of the electrode, SEI layer thickness and particle morphology. On the basis of these investigations, a more comprehensive view of the degradation phenomena of the electrode is established. Figure 1

In the present work, an alternative to the standard ex-situ and destructive focused ion beam scanning electron microscopy (FIB/SEM) analysis procedure is demonstrated for monitoring the morphological degradation of a single Si/graphite (1/1 mass ratio) blended electrode for Li-ion batteries. For this purpose, a FIB milled microcavity is created in the pristine electrode, which is observed in FIB- polished cross section by SEM at different cycling periods (pristine, 1st, 9th and 50th cycles). This allows studying the same cycled electrode as for an in-situ method. Its cycling-induced morphological change is characterized at the electrode and particle scales by monitoring the evolution of the electrode thickness, mass and porosity, the Si particle morphology, Si interparticle distance, surface fraction and twisting of the graphite flakes. This is correlated to the evolution of the electrode discharge capacity and impedance. As a result, a more comprehensive view of the degradation phenomena of the Si/graphite blended electrode is established.

Visualization and quantification of the morphological changes of Si-based electrodes occurring upon cycling are essential for better understanding their degradation mechanism and for optimizing their formulation. In this context, in-situ and ex-situ X-ray computed tomography (XRCT) analyses are here performed on Si-based electrodes for different cycling steps and at different scales (i.e. from the composite electrode level down to the Si particle one). Three different cell configurations and four different X-ray sources (one laboratory and three synchrotrons) have been used and their impact on the image resolution/quality and the segmentation of the different solid, electrolyte and gas phases of the composite electrodes is highlighted. From these complementary XRCT analyses with a voxel size ranging from 0.8 to 0.05 mu m, key morphological features have been studied such as (i) the volume expansion/contraction of the electrode, (ii) the dynamics of the electrode macrocracking, (iii) the initial solid electrolyte interphase (SEI) layer growth and related formation of gas and consumption of electrolyte, which strongly depend on the presence of fluoroethylene carbonate in the electrolyte, (iv) the evolution of the electrode porosity and macrocrack volume fraction/connectivity/width after prolonged cycling.

The rapid degradation of the environment and unsustainable use of our resources are arguably the two major threats to humanity. Biodiversity, which is an essential prerequisite for resilient ecosys...

Silicon is attractive as negative electrode material for Li-ion batteries (LIBs) to increase their energy density [1]. The main challenge is to deal with the large silicon volume expansion induced by its lithiation, which damages the mechanical integrity of the electrode, and produces an unstable solid electrolyte interphase (SEI). Recently, we have discovered a post-processing treatment, called maturation, which very significantly improves the mechanical and electrochemical stabilities of silicon-based electrodes made with polycarboxylic acid binders [2-4]. It consists of storing the electrode in a humid atmosphere for a few days before drying and cell assembly. We found that during maturation, the atmospheric-induced corrosion of the current collector releases oxidized copper species that migrate into the electrode to physically crosslink the binder phase, substantially modifying its resiliency to the silicon volume variation as shown by various in situ and operando characterizations. The pre-addition of a small amount of copper or zinc salt in the electrode slurry allows to reach similar improvement of electrochemical performance than maturation [5]. This reveals that there is great potential to explore coordination chemistry to design new, more efficient binders through the medium strength and dynamic nature of coordination bonds [6]. Acknowledgments The authors thank the Natural Sciences and Engineering Research Council of Canada (NSERC) (grant RGPIN-2016-04524) and Transition Énergétique Québec (TEQ) (grant Techno-0040-0001) for financial support of this work. References [1] M.N. Obrovac, Si-alloy negative electrodes for Li-ion batteries. Current Opinion in Electrochemistr, 2018, 9, 8–17. [2] Z. Karkar et al., How silicon electrodes can be calendered without altering their mechanical strength and cycle life J. Power Sources, 2017, 371, 136-147. [3] C. Real Hernandez et al., A Facile and Very Effective Method to Enhance the Mechanical Strength and the Cyclability of Si-Based Electrodes for Li-Ion Batteries, Adv. Energy Mater, 2017, 1701787. [4] V. Vanpenne et al., Adv. Energy Mater, Dynamics of the morphological degradation of Si-based anodes for Li-ion batteries characterized by in-situ synchrotron X-ray tomography, Adv. Energy Mater. 9, 2019, 1803947 [5] D. Mazouzi et al., CMC-citric acid Cu(II) cross-linked binder approach to improve the electrochemical performance of Si-based electrodes Electrochimica Acta, 2019, 304, 495-504. [6] T. Devic, B. Lestriez, L. Roué, Silicon Electrodes for Li-Ion Batteries. Addressing the Challenges through Coordination Chemistry, ACS Energy Letters, ACS Energy Lett., 2019, 4, 550−557.

The evolution of the three-dimensional (3D) morphology of a Si-based electrode upon cycling (1st discharge, 1st charge and 2nd discharge) is studied by in-situ synchrotron X-ray tomography. The Si-based electrode is constituted of silicon/carbon black/carboxymethylcellulose (Si/CB/CMC) embedded in a commercial carbon fiber paper, acting as a flexible 3D current collector. Its initial areal discharge capacity is 4.9 mAh cm(-2). A reconstructed volume of 293 x 293 x 137 mu m(3) is analyzed with a resolution of similar to 0.3 mu m. Three phases are identified: (i) the solid phase (C fibers + Si + CB + CMC), (ii) the electrolyte phase (pores filled with electrolyte) and (iii) the gas phase (electrolyte-free pores). Their respective volume fraction, size distribution and connectivity, and also the dimensional changes of the electrode along the three axes are quantified during cycling. At the beginning of the 1st discharge (lithiation), the formation of gas channels attributed to the reductive electrolyte decomposition is observed. During the 1st charge, large cracks are formed through the electrode, which reclose during the subsequent discharge. The electrode expansion contraction due to the Si volume change is partially irreversible, occurs mainly in the transverse direction and is much larger in the bottom part of the electrode. (C) 2017 Elsevier B.V. All rights reserved.

In the context of increasing energy density of lithium‐ion batteries, silicon is of high interest with his high theoretical gravimetric capacity, ten times higher than the commonly used carbon. However the use of silicon is faced to huge hurdles such as poor life time of those electrodes and not sufficient sustainability versus high current density (commonly used in EVs and HEVs). The poor cycle life of Si‐based electrodes is mainly due to their large volume variation upon cycling, inducing electrical disconnections and instability of the solid electrolyte interface (SEI). The study of the morphological variation of Si‐based electrodes upon cycling is thus highly relevant to evaluate their degradation and to optimize their formulation and architecture. However, this is challenging considering their complex three‐dimensional structure and their major evolution with cycling. Furthermore, samples are fragile and reactive and therefore difficult to prepare for bulk observations. In this context, X‐ray tomography appears as an effective non‐destructive and 3D observation tool. In this communication, in‐situ synchrotron X‐ray tomography analyses are performed on Si‐based electrodes prepared from a pH3 buffered slurry of ball‐milled Si powder + carbon black + carboxymethylcellulose (CMC) (80/12/8) loaded into a carbon paper (AvCarb EP40) by impregnation, in order to get a clear view of the 3D architecture of the electrode with cycling. From the initial state, represented in Fig. 1, to fully lithiated and then fully delithiated state, X‐ray scans were performed each thirty minutes to continuously follow the morphological evolution of the electrode structure. After an appropriate image reconstruction and segmentation procedure, phase identification has been achieved. Moreover the separation of a void porosity and an electrolyte phase was possible and the quantifying of the pore size distribution evolution with cycling, as shown in Fig. 2. Also key morphological parameters of these Si‐based electrodes and their evolution with cycling are determined, such as the electrode thickness and volume fraction of the pores as shown in Fig. 3. Those results may greatly enlighten the understanding of degradation phenomena in the Si‐based electrodes and help develop new composite electrodes formulation for sustainable applications.