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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]

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]

An effective route to enhance the volume ratio of active materials in a lithium‐ion battery (LIB) or sodium‐ion battery (NaB) consists in increasing the electrode thickness, that is, active mass loading, as it reduces the volume and weight fractions of the separator and current collectors in the cell. This approach also serves to reduce the battery cost, chiefly associated with the expensive polymeric separator. However, following the standard industrial coating process, the mechanically stable electrode can hardly exceed an active mass loading of about 30 mg cm−2, corresponding to a nominal areal capacity around 6 mAh cm−2 due to the binder migration during the drying step. Herein, a straightforward manufacturing process based on a filtration technique is developed. It enables the design of LIB electrodes with a nominal areal capacity up to 20 mAh cm−2. A pierced and serrated current collector allows at the same time both filtration and mechanical interlocking of the electrode layer. Cells assembled with such ultra‐thick filtered electrodes exhibit very promising performances, thereby promoting the design of high‐energy and low‐cost LIBs and NaBs by a fast fabrication process. [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: 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]

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]

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]