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Broadband dielectric spectroscopy (BDS) is used to measure complex permittivity and conductivity of conducting materials for lithium batteries at frequencies from a few Hz to several GHz with network and impedance analysers. Under the influence of an electric field, there will be charge density fluctuations in the conductor mainly due to electronic transfer. These fluctuations result in dielectric relaxations for frequencies below 100 GHz. The materials are compacted powders in which each element (particles, agglomerates of particles) can have different sizes and morphologies. In the present review, studies are reported on the influence of surface states in LiNiO 2 (ageing and degradation in air) and LiFePO 4 (carbon coating thin layer), and on a composite electrode based on the lithium trivanadate (Li 1.1 V 3 O 8 ) active material. The results have shown that the BDS technique is very sensitive to the different scales of materials architectures involved in electronic transport, from interatomic distances to macroscopic sizes. [ABSTRACT FROM AUTHOR]

Abstract: The different functions of polymer binders on the processing of the electrode, the electrical (electronic and ionic) and mechanical properties of the electrode, and as a consequence on the electrochemical performance are discussed. The role of the polymer binder on the solid–electrolyte interface (SEI) layer and the cyclability of the graphite- and silicon-based negative electrodes is also addressed. All these properties critically depend on the very thin layer formed by the polymer at the surface of the active and conductive particles. That is where research efforts have to focus on, now, for further optimization of electrodes through tailoring of the binder combination. [Copyright &y& Elsevier]

Abstract: We studied the effect of the dispersion and/or morphology within the positive composite electrode on the lithium battery performance. Model electrodes have been prepared in which the surrounding of the same AM (Li1.1V3O8) is changed by playing with plasticization of the polymeric binder (B) (PMMA) by ethylene carbonate (EC) and propylene carbonate (PC). We have also varied the concentration, and the nature of the solvent used for the electrode elaboration (THF and CHCl3). The cycled capacity varies between 100 and 250mAh/g (C/5 rate, 3.3–2V) depending on these parameters. The performance was shown to depend on the quality of AM, B, and carbon black (CB) dispersion within the electrode. The quality of the AM dispersion depends on the solvent concentration that affects the mixture viscosity. Formation of AM agglomerates results from high viscosity, while gradient concentrations appear due to sedimentation in low viscosity suspensions. Optimal distribution and subsequent electrode performance result from optimal solvent concentration. Better CB dispersion was obtained in the case of favourable interactions between the solvent and the polymer. This resulted in a higher electronic conductivity, a higher porosity, and improved electrochemical performance. Finally, the addition of EC–PC also favours the CB dispersion and further increases the cycling capacity. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Mastering electrodes' formulations is a complex and tedious task, because for each composition of electroactive material(s) it is necessary to adjust the inactive additives nature and content to optimize battery performance. In this direction, the amount of binder is proposed to be adjusted to the surface developed by all of the powders involved in the composition of the electrode, i.e., the electroactive materials and electronic conductive additives. This concept, introduces here as binder‐to‐powders coverage ratio, relies upon the micromechanical models developed in the field of polymer‐based composite materials. The validity of this new electrode formulation parameter is shown here for two different SiOx/Graphite blends, which differ in the type of graphite, and for blends of two different binders, polyacrylic acid and styrene−butadiene rubber. At the optimal coverage ratio, a satisfactory capacity retention is obtained in full cell with an ethylene carbonate free and fluoroethylene carbonate rich electrolyte. [ABSTRACT FROM AUTHOR]

The physical crosslinking of polymeric binders through coordination chemistry significantly improves the electrochemical performance of silicon‐based negative electrodes. Scanning electron microscopy coupled with energy dispersive X‐ray spectroscopy is used to probe the nanoscale morphology of such electrodes. This technique reveals the homogeneous coordination of carboxylated binder with Zn cations and its layering on the silicon surface. The solid electrolyte interphase (SEI) formed after the first cycle is denser with Zn‐coordinated binder and preferentially observed on binder‐depleted zones. The superiority of coordinated binders can be attributed to their capacity to better stabilize the electrode and the SEI layer due to improved mechanical properties. This results in a lower SEI impedance, a higher first cycle coulombic efficiency, and a 40% improvement of capacity retention after 50 cycles for highly loaded electrodes of over 6 mAh cm–2. [ABSTRACT FROM AUTHOR]

The polymer binder is a key constituent of silicon‐based electrode formulation for lithium‐ion batteries. However, its extremely difficult visualization in fresh electrodes becomes completely impossible in cycled electrodes. Here, the combination of scanning transmission electron microscopy—valence electron energy‐loss spectroscopy with the use of a specific electrolyte solvent composition (a mixture of dimethyl carbonate and fluoroethylene carbonate, without ethylene carbonate) allows the visualization, for the first time, of the binder in silicon‐based electrodes, even cycled up to 100 cycles. Such an observation is possible as the only solid degradation product of this electrolyte is LiF, as confirmed by quantitative 7Li and 19F magic angle spinning nuclear magnetic resonance. The electrodes, based on a blend of silicon and graphite, have a very high surface capacity, 6.5 mAh cm−2, which makes them meaningful for electric vehicle applications. The performance is appreciable, in particular the first cycle efficiency approaching that of commercial graphite electrodes, as well as the capacity retention in full cell, versus LiNi0.5Mn0.3Co0.2O2, 60% after 100 cycles. This work also illustrates the ultimate state of destructuration of silicon after long cycling, which invites new ways of thinking about the design of this material. [ABSTRACT FROM AUTHOR]

Abstract: The local composition of negative silicon electrodes is studied by ex situ electron energy-loss spectroscopy along the first delithiation in a lithium battery. By measuring dozens of sample areas for over a dozen compositions, the local and overall inhomogeneities in these practical electrodes are evaluated. The statistical treatment of the data highlights the existence of larger inhomogeneities at the beginning of the delithiation as well as at a 100nm scale. It is also shown that, even if incremental capacity curves are different, the compositional changes during delithiation are identical for nano- and micro-Si. Namely, an initial Li15Si4 phase is replaced by a Li2±0.3Si amorphous phase in a biphasic process, the latter compound being further delithiated to amorphous silicon in single phase process. Results also show that the electrochemical irreversibility associated with the liquid electrolyte reduction/degradation is generated during the lithiation process, not the delithiation process. [Copyright &y& Elsevier]

Abstract: It is well known that the mechanical properties of lithium‐ion battery electrodes impact their electrochemical performance. This is especially critical for Si‐based negative electrodes, which suffer from large volume changes of the active mass upon cycling. Here, this study presents a postprocessing treatment (called maturation) that improves the mechanical and electrochemical stabilities of silicon‐based anodes made with an acidic aqueous binder. It consists of storing the electrode in a humid atmosphere for a few days before drying and cell assembly. This results in a beneficial in situ reactive modification of the interfaces within the electrode. First, the binder tends to concentrate at the silicon interparticle contacts. As a result, the cohesion of the composite film is strengthened. Second, the corrosion of the copper current collector, inducing the formation of copper carboxylate bonds, improves the adhesion of the composite film. The great improvement of the mechanical stability of the matured electrode is confirmed by in‐operando optical microscopy showing the absence of film delamination. The result is a significant electrochemical performance gain, up to a factor 10, compared to a not‐matured electrode. This maturation procedure can be applied to other types of electrodes for improving their electrochemical performance and also their handling during cell manufacturing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tannic acid can be used as a binder in Li-ion silicon electrodes. • Tannic acid can be used as an electronic conductor precursor in electrodes. • Tannic acid transforms in situ into a conducting and likely polymeric species. State of-the-art Si electrodes for Li-ion batteries typically require the addition of an advanced polymeric binder and a conductive carbon additive to the active material in order to circumvolve the issues associated with silicon, namely its poor conductivity in the oxidized state, and its high volume variation upon lithiation which give rise to several failure mechanisms. Here, we demonstrate that both additives can be replaced by a cheap, naturally available, polyphenol, tannic acid (TA). We show that Si/TA electrodes (80/20 wt%), even with a high loading (∼2 mg _Si cm−2), can retain a specific capacity above 2000 mAh g−1 after 50 cycles. This unexpected result appears to result from the irreversible reduction of TA during the first cycle, into a conducting, likely polymeric, species. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are electrochemical storage devices using the electrochemical activity of the lithium ion in relation to intercalation compounds owing to mass transport phenomena through diffusion. Diffusion of the lithium ion in the electrode pores has been poorly understood due to the lack of experimental techniques for measuring its self-diffusion coefficient in porous media. Magic-Angle Spinning, Pulsed Field Gradient, Stimulated-Echo Nuclear Magnetic Resonance (MAS-PFG-STE NMR) was used here for the first time to measure the self-diffusion coefficients of the electrolyte species in the LP30 battery electrolyte (i.e. a 1 M solution of LiPF 6 dissolved in 1:1 Ethylene Carbonate - Dimethyl Carbonate) in model composites. These composite electrodes were made of alumina, carbon black and PVdF-HFP. Alumina's magnetic susceptibility is close to the measured magnetic susceptibility of the LP30 electrolyte thereby limiting undesirable internal field gradients. Interestingly, the self-diffusion coefficient of lithium ions decreases with increasing carbon content. FIB-SEM was used to describe the 3D geometry of the samples. The comparison between the reduction of self-diffusion coefficients as measured by PFG-NMR and as geometrically derived from FIB/SEM tortuosity values highlights the contribution of specific interactions at the material/electrolyte interface on the lithium transport properties. [ABSTRACT FROM AUTHOR]

In this work, exhaustive characterizations of 3D geometries of LiNi1/3Mn1/3Co1/3O2 (NMC), LiFePO4 (LFP), and NMC/LFP blended electrodes are undertaken for rational interpretation of their measured electrical properties and electrochemical performance. X-ray tomography and focused ion beam in combination with scanning electron microscopy tomography are used for a multiscale analysis of electrodes 3D geometries. Their multiscale electrical properties are measured by using broadband dielectric spectroscopy. Finally, discharge rate performance are measured and analyzed by simple, yet efficient methods. It allows us to discriminate between electronic and ionic wirings as the performance limiting factors, depending on the discharge rate. This approach is a unique exhaustive analysis of the experimental relationships between the electrochemical behavior, the transport properties within the electrode, and its 3D geometry. [ABSTRACT FROM AUTHOR]

The discovery of conducting lithium-doped polyaniline with reversible redox chemistry allows simultaneous unprecedented capacity and stability in a non-aqueous Li battery. This compound (lithium emeraldinate) was synthesized by lithium-proton exchange on the emeraldine base in an anhydrous lithium-based electrolyte. A combination of UV/Vis-NIR spectroelectrochemistry, XPS, FTIR, and EQCM characterization allowed a unified description of the chemical and electrochemical behavior, showing facile charge delocalization of the doped states and the reversibility of the redox processes in this form of polyaniline. From a practical point of view, lithium emeraldinate behaves as a high-capacity organic active material (230 mAh g−1) that enables preparation of relatively thick composite electrodes with a low amount of carbon additives and high energy density (460 Wh kg−1). Concomitantly, at 1 C rate, 400 cycles were achieved without significant capacity loss, while the coulombic efficiency is greater than 99 %. [ABSTRACT FROM AUTHOR]

The discovery of conducting lithium-doped polyaniline with reversible redox chemistry allows simultaneous unprecedented capacity and stability in a non-aqueous Li battery. This compound (lithium emeraldinate) was synthesized by lithium-proton exchange on the emeraldine base in an anhydrous lithium-based electrolyte. A combination of UV/Vis-NIR spectroelectrochemistry, XPS, FTIR, and EQCM characterization allowed a unified description of the chemical and electrochemical behavior, showing facile charge delocalization of the doped states and the reversibility of the redox processes in this form of polyaniline. From a practical point of view, lithium emeraldinate behaves as a high-capacity organic active material (230 mAh g−1) that enables preparation of relatively thick composite electrodes with a low amount of carbon additives and high energy density (460 Wh kg−1). Concomitantly, at 1 C rate, 400 cycles were achieved without significant capacity loss, while the coulombic efficiency is greater than 99 %. [ABSTRACT FROM AUTHOR]

This work aims at better understanding the interactions existing between the liquid electrolyte and the solid composite electrode in a Li-ion battery. We substituted the common active material (e.g. LiNi 1/3 Mn 1/3 Co 1/3 O 2 or LiFePO 4) by an insulating (inactive) γ-Al 2 O 3 compound in order to detect and evidence the interaction between the carbon black electronic additive and the liquid electrolyte. Our study presents the characterization of charge (electrons and ions) transport at different scales by combining a high-frequency analysis performed by broadband dielectric spectroscopy (BDS, up to 1010 Hz), along with a low-frequency analysis performed by electrochemical impedance spectroscopy (EIS, down to 10−3 Hz). Two carbon black materials with two different specific surface areas (80 m2.g−1 and 65 m2.g−1, respectively) were studied. The electronic percolation threshold and the kinetics of impregnation of the hierarchical composite electrode by the liquid electrolyte have been determined with respect to the carbon black content. The significant influence of the adsorbtion of ions at the carbon black surface on the electrons transport is particularly highlighted and explained. [ABSTRACT FROM AUTHOR]

A suspension of Li4Ti5O12 and of Ketjen black in a solution of 1 M lithium bis(trifluoromethanesulfonyl)imide in propylene carbonate is studied as the anolyte for semisolid redox flow batteries. The rheological behavior and electronic conductivity are studied both at rest and under shear flow. The electrochemical behavior is evaluated at rest as a function of the charge/discharge rates and of the thickness of the suspension in the electrochemical cell. The highly beneficial influence of the addition of a non-ionic surfactant in the composition of the suspension is demonstrated. All practical properties are improved with respect to semisolid redox flow applications. The viscosity decreases, the electronic conductivity increases and is less affected by the shear flow, and the electrochemical performance is improved. Moreover, the suspension shows much better stability, so its performance is preserved over time. [ABSTRACT FROM AUTHOR]

In an attempt to optimize a suspension electrode for redox flow batteries, this work demonstrates the effect of solid content and additive material on the electrical and rheological behavior of an anolyte made up of lithium titanium oxide (Li 4 Ti 5 O 12 (LTO), as active material), carbon black (Ketjen black (KB), as a conductive material) suspended in organic medium (1 M lithium bis(trifluoromethane)sulfonimide; LiTFSI in propylene carbonate). The rheo-electrical properties of the anolyte are very sensitive to the Li 4 Ti 5 O 12 content. The 20 wt% LTO is the maximum loading the percolated KB network can sustain without significant loss of the electronic conductivity and flowability of the electrode. Interestingly, this critical concentration increases to 25 wt% by addition of trace amount of conductive carbon nanofibers (CNFs) which electronically wire the conductive pathways and even reduce viscosity of the suspension electrode. Under shear flow, the suspension electrodes show three-regime flow curves with intermediate shear-thickening regions in accordance with minima in the conductivity. These minima are sharper at higher KB content, but nearly disappear in suspension electrodes with CNFs additive implying its role in wiring the ruptured conductive pathways under flow. [ABSTRACT FROM AUTHOR]

This work reveals the great potential of in situ dielectric spectroscopy for deciphering the motion of ions and electrons on different scales in lithium-ion battery electrodes. One of the main bottlenecks limiting composite electrode kinetics and energy density, is a critical lack of fundamental understanding with respect to the electronic and the ionic transport within the electrode architecture. The latter is a granular material made up of clusters of particles, in which the particles are separated by boundaries that limit the electronic transport. The ionic transport is also severely restricted due to its tortuous porosity. Here, in situ dielectric spectroscopy is used to study the lithium-ion battery LiNi1/3Co1/3Mn1/3O2 composite electrodes. Short- and long-range motions of ions are evident in the low-frequency region. At higher frequencies, the influence of the adsorbed electrolyte ions on the electronic transfer at the micrometer scale is shown. [ABSTRACT FROM AUTHOR]

Abstract: High-energy ball milling is used to recycle Si wafers to produce Si powders for negative electrodes of Li-ion batteries. The resulting Si powder consists in micrometric Si agglomerates made of cold-welded submicrometric nanocrystalline Si particles. Silicon-based composite electrodes prepared with ball-milled Si wafer can achieve more than 900 cycles with a capacity of 1200 mAh g−1 of Si (880 mAh g−1 of electrode) and a coulombic efficiency higher than 99%. This excellent electrochemical performance lies in the use of nanostructured Si produced by ball milling, the electrode formulation in a pH 3 buffer solution with CMC as binder and the use of FEC/VC additives in the electrolyte. This work opens the way to an economically attractive recycling of Si wastes. [Copyright &y& Elsevier]

Cu foam is evaluated as a replacement for metal foil current collectors to create 3D composite electrodes with the objective to produce Si-based anodes with high loadings. The electrodes are prepared by casting the slurry into the porosity of the foam. With such a design, the loading and the surface capacity can reach values as high as 10 mg cm−2 and 10 mAh cm−2. Compared to the common 2D design, the 3D copper framework shows a great advantage in the cycle life (more than 400 cycles at a Si loading of 10 mg cm−2 with commercial micrometric particles) and power performance. The thinness of the composite coating on the foam walls favors a better preservation of the electronic wiring upon cycling and fast lithium ion diffusion. A higher coulombic efficiency in half cells with lithium metal as the counter electrode is achieved by using carbon nanofibers (CNF) rather than carbon black (CB). The possibility to reach, in practice, higher surface capacity could allow a significant increase in both the volumetric and gravimetric energy densities by 23% and 19%, respectively, for the Cu foam-silicon//LiFePO4 stack compared to the graphite/LiFePO4 stack of traditional design. [ABSTRACT FROM AUTHOR]

Solid and flexible ionogel‐based membranes are obtained by a simple one‐step process. Tuning the composition of the silica–polymer hybrid membranes allows the attainment of highly specific properties. The high ionic conductivities of the solid membranes are in the range of those of the ionic liquid electrolytes on which they are based. Good mechanical properties and high transparency from 250 to 1000 nm are also observed. The membranes are successfully applied within entirely solid lithium batteries. [ABSTRACT FROM AUTHOR]

Abstract: Lithium/sulfur batteries in Lithium Metal Polymer (LMP) technology suffer from poor reversibility and important capacity fade. In this paper we studied structural evolutions of Li/S cells with PEO-based (poly(ethylene oxide)) dry polymer electrolyte, by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Discharge occurs along with dissolution of the active material into soluble polysulfides in PEO. Diffusion of the sulfide species results in important volume changes of both the electrode and the electrolyte. This eventually leads to collapse of the electrode upon a few cycles, which contributes to the poor cyclability of the battery. In order to prevent this phenomenon, the mechanical strength of the cathode was enhanced by adding poly(vinylidene fluoride) (PVDF) in its composition. However, although PVDF helps maintaining the electrode's structure, it could not completely solve the cyclability issue. [Copyright &y& Elsevier]

Cell ageing mechanism, fluoroethylene carbonate, Li-ion batteries, polyacrylic binders, silicon/graphite anodes From the Direct Observation of a PAA-Based Binder Using STEM-VEELS to the Ageing Mechanism of Silicon/Graphite Anode with High Areal Capacity Cycled in an FEC-Rich and EC-Free Electrolyte (Adv. Keywords: cell ageing mechanism; fluoroethylene carbonate; Li-ion batteries; polyacrylic binders; silicon/graphite anodes EN cell ageing mechanism fluoroethylene carbonate Li-ion batteries polyacrylic binders silicon/graphite anodes 1 1 1 03/28/22 20220324 NES 220324 B Polyacrylic Binders b In article number 2103348, Bernard Lestriez and co-workers use the combination of STEM-VEELS with the use of a specific electrolyte solvent composition to visualize, for the first time, the binder (polyacrilic acid, in blue) in silicon-based electrodes, even after up to 100 cycles. [Extracted from the article]

Abstract: An electrochemically roughened copper foil was evaluated as a current collector for micrometric Si powder (ball-milled) based electrodes prepared by the conventional slurry-coating method. The formation of a bunch of copper nanowires on the current collector provides a rough surface, which enhances the adhesion of the Si composite electrode as confirmed from scratch tests. This produces a major decrease of the irreversible capacity associated with the electrical disconnection of the Si particles with cycling, which results in a great improvement of the electrode cycle life. With such a roughened Cu current collector, the micrometric Si-based electrode is able to maintain a discharge capacity of 1200mAhg−1 for at least 1000 cycles. [Copyright &y& Elsevier]

Reduced graphene oxide (rGO) is used as a conductive additive for nanosilicon-based lithium battery anodes with the high active-mass loading typically required for industrial applications. In contrast to conventional Si electrodes that use acetylene black (AcB) as an additive, the rGO system shows pronounced improvement of electrochemical performance, irrespective of the cycling conditions. With capacity limitation, the rGO system results in improved coulombic efficiency (99.9%) and longer cycle life than conventional electrodes. Upon cycling without capacity limitation, much higher discharge capacity is maintained (2000 mAh g−1 after 100 cycles for 2.5 mg of Si cm−2). Used in conjunction with the bridging carboxymethyl cellulose binder, the crumpled and resilient rGO allows highly reversible functioning of the electrode in which the Si particles repeatedly inflate and deflate upon alloying and dealloying with lithium. [ABSTRACT FROM AUTHOR]

Abstract: To improve the performance of the positive electrode in batteries, it is important to thoroughly characterize these materials during battery cycling, beyond just electrochemical characterization. Among the very few techniques available for operando studies, X-ray Absorption Spectroscopy (XAS) appears very powerful, with high spatial and time resolutions provided by synchrotron radiation. Moreover XAS is well known for its capabilities in charge transfer and structure determinations, both being the major changes induced by electrochemical cycling of electrode materials. By an appropriate combination of three XAS beamlines using a specially designed electrochemical cell, we have studied composite positive electrodes made with LiFePO4 as the active material. We directly observed the heterogeneity of the electrode during operation, some parts being delayed and others advanced, compared to the mean charge state of the electrode. A mapping of this heterogeneity was made at different length scales. [Copyright &y& Elsevier]

Abstract: A simple analysis of the polarization resistance of the electrodes as function of the loading mass for various cycling rates allows identifying the fading mechanism on cycling of NiSb2, a typical conversion material: pulverization of active mass and further degradation of the electronic wiring at high rate and agglomeration of the active mass at low rate. Such rate-control of the degradation mechanism might reflect a thermodynamic instability of interfaces in the lithiated compound, which would however be in kinetic competition with the Lithium de-insertion. The analysis of the electrode polarization resistance fingerprint to rapidly identify the failure mechanism in a composite electrode can be generalized to other active materials. [Copyright &y& Elsevier]

Abstract: Aqueous processing would reduce the costs and toxicity associated with the making of the composite electrode. In the present study, carboxymethyl cellulose is used as a binder for 5V cathode material LiNi0.4Mn1.6O4. Compared with electrodes using polyvinylidene difluoride binder, CMC-based LiNi0.4Mn1.6O4 electrodes display a better discharge capacity at all rates. At 0.2C, the discharge capacity is close to the theoretical capacity (146mAhg−1) and the self-discharge is 10% lower. Polyvinylidene difluoride can be efficiently replaced by carboxymethyl cellulose for LiNi0.4Mn1.6O4 in terms of electrochemical performance and brings the advantage of an environment friendly and low cost electrode processing. [Copyright &y& Elsevier]

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. [Display omitted] • An investigation technique based on sequential FIB/SEM analysis is demonstrated. • Cycling-induced morphological change of a single Si/Gr electrode is studied. • Morphological changes are correlated with EIS measurements. • The methodology can be extended to other battery systems. [ABSTRACT FROM AUTHOR]

In this study, water-processed LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathodes (NMC532) are investigated. Notably, corrosion of aluminum current collector occurring in aqueous processing owing to alkalinity of NMC slurry is avoided through addition of phosphoric acid which buffers the slurry pH, or by using a carbon-coated collector. The impact of small amounts of phosphoric acid on the electrochemical performance is evaluated in half-cells, and the best formulations are selected to perform further ageing tests in pouch cells. In particular, post mortem analyses such as electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy are conducted on the cathodes after long-term cycling in Li-ion cells to fully understand the enhanced cycling stability observed with H 3 PO 4 -containing water-based cathode. These analyses allow to conclude on the influence of the binder, the current collector, and the aqueous immersion of the NMC532 powder. Image 1 • Water-based NMC532 electrodes exhibited higher capacity retention than NMP-based. • Carbon coating on collector successfully mitigates Al corrosion. • Addition of 0.5 wt% H3PO4 in aqueous slurry improves cycling stability. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are the state-of-the-art electrochemical energy storage technology for mobile electronic devices and electric vehicles. Accordingly, they have attracted a continuously increasing interest in academia and industry, which has led to a steady improvement in energy and power density, while the costs have decreased at even faster pace. Important questions, though, are, to which extent and how (fast) the performance can be further improved, and how the envisioned goal of truly sustainable energy storage can be realized. Herein, we combine a comprehensive review of important findings and developments in this field that have enabled their tremendous success with an overview of very recent trends concerning the active materials for the negative and positive electrode as well as the electrolyte. Moreover, we critically discuss current and anticipated electrode fabrication processes, as well as an essential prerequisite for "greener" batteries – the recycling. In each of these chapters, we eventually summarize important remaining challenges and propose potential directions for further improvement. Finally, we conclude this article with a brief summary of the performance metrics of commercial lithium-ion cells and a few thoughts towards the future development of this technology including several key performance indicators for the mid-term to long-term future. Image 1 • Comprehensive review of commercially used Li-ion active materials and electrolytes. • Overview of relevant electrode preparation and recycling technologies. • Critical discussion of the state of the art and remaining challenges. • Indication of future research directions towards further improved Li-ion batteries. • Proposal of key performance indicators for the mid- & long-term future development. [ABSTRACT FROM AUTHOR]

The alloying reaction of silicon with lithium in negative electrodes for lithium‐ion batteries causes brutal morphological changes that severely degrade their cyclability. In this study, the dynamics of their expansion and contraction, of their cracking in the bulk and of their debonding at the interface with the current collector are visualized by in situ synchrotron X‐ray computed tomography and quantified from appropriate 3D imaging analyses. Two electrodes made with same silicon material having reasonable particle size distribution from an applied point of view are compared: one fabricated according to a standard process and the other one prepared with a maturation step, which consists in storing the electrode in a humid atmosphere for a few days before drying and cell assembly. All morphological degradations are significantly restrained for the matured electrode, confirming the great efficiency of this maturation step to produce a more ductile and resilient electrode architecture, which is at the origin of the major improvement in their cyclability. [ABSTRACT FROM AUTHOR]

A better understanding of the charge transport (ions and electrons) kinetics limitations through the electrode is required to improve the Li‐ion battery's energy and power density in view of electrical cars deployment. In article number 1602239, Bernard Lestriez and co‐workers connect for the first time the parameters describing the microstructure of electrodes with both measurements of their transport properties and their electrochemical performance. [ABSTRACT FROM AUTHOR]