Formation and Evolution of the Solid Electrolyte Interphase on Silicon Electrodes from Fluorine-Free Electrolytes.

With the increasing attention to energy storage solutions, a growing emphasis has been placed on environmentally compatible electrolytes tailored for lithium-ion batteries. This study investigates the surface behavior of Si wafers as model systems cycled with a fluorine-free electrolyte based on lithium bis(oxalato)borate (LiBOB), with and without the additive vinylene carbonate (VC). By utilizing operando X-ray reflectivity (XRR) and ex situ X-ray photoelectron spectroscopy (XPS), the intricate processes involved in solid electrolyte interphase (SEI) formation is elucidated, SiO/Si (de)lithiation, and the impact of the VC additive.

Transference Numbers and Ion Coordination Strength for Mg, Na, and K in Solid Polymer Electrolytes.

In solid polymer electrolytes, the transference number ( ) is fundamental for performance as it defines the transport efficiency of the electrochemically active species. For systems "beyond Li", a lack of suitable methods to determine the is limiting the understanding of the ion transport in such systems. In this study, a method based on electrophoretic NMR (eNMR) and electrochemical impedance spectroscopy (EIS) is used to determine the for Na, K, and Mg in poly(ε-caprolactone) (PCL), comparing this to previous results in poly(ethylene oxide).

Boron Surface Treatment of LiLaZrO Enabling Solid Composite Electrolytes for Li-Metal Battery Applications.

Despite being promoted as a superior Li-ion conductor, lithium lanthanum zirconium oxide (LLZO) still suffers from a number of shortcomings when employed as an active ceramic filler in composite polymer-ceramic solid electrolytes for rechargeable all-solid-state lithium metal batteries. One of the main limitations is the detrimental presence of LiCO on the surface of LLZO particles, restricting Li-ion transport at the polymer-ceramic interfaces. In this work, a facile way to improve this interface is presented, by purposely engineering the LLZO particle surfaces for a better compatibility with a PEO:LiTFSI solid polymer electrolyte matrix.

Initial SEI formation in LiBOB-, LiDFOB- and LiBF-containing PEO electrolytes.

A limiting factor for solid polymer electrolyte (SPE)-based Li-batteries is the functionality of the electrolyte decomposition layer that is spontaneously formed at the Li metal anode. A deeper understanding of this layer will facilitate its improvement. This study investigates three SPEs - polyethylene oxide:lithium tetrafluoroborate (PEO:LiBF), polyethylene oxide:lithium bis(oxalate)borate (PEO:LiBOB), and polyethylene oxide:lithium difluoro(oxalato)borate (PEO:LiDFOB) - using a combination of electrochemical impedance spectroscopy (EIS), galvanostatic cycling, Li deposition photoelectron spectroscopy (PES), and molecular dynamics (AIMD) simulations.

Seeing the Unseen: Mg, Na, and K Transference Numbers in Post-Li Battery Electrolytes by Electrophoretic Nuclear Magnetic Resonance.

The growing demand for energy storage devices worldwide combined with limited resources for lithium attracts interest in other alkali or alkaline earth metals. In addition to conductivity, the cation transference number is a decisive parameter to rank the electrolyte performance. However, the existing experimental methods for its determination suffer from various intrinsic problems.

Correction: Quantifying the ion coordination strength in polymer electrolytes.

Correction for 'Quantifying the ion coordination strength in polymer electrolytes' by Rassmus Andersson , , 2022, , 16343-16352, https://doi.org/10.1039/D2CP01904C.

Ion Transport in Polymer Electrolytes: Building New Bridges between Experiment and Molecular Simulation.

ConspectusPolymer electrolytes constitute a promising type of material for solid-state batteries. However, one of the bottlenecks for their practical implementation lies in the transport properties, often including restricted Li self-diffusion and conductivity and low cationic transference numbers. This calls for a molecular understanding of ion transport in polymer electrolytes in which molecular dynamics (MD) simulation can provide both new physical insights and quantitative predictions.

Efficiency Roll-Off in Light-Emitting Electrochemical Cells.

Understanding "efficiency roll-off" (i.e., the drop in emission efficiency with increasing current) is critical if efficient and bright emissive technologies are to be rationally designed.

Do non-coordinating polymers function as host materials for solid polymer electrolytes? The case of PVdF-HFP.

In the search for novel solid polymer electrolytes (SPEs), primarily targeting battery applications, a range of different polymers is currently being explored. In this context, the non-coordinating poly(vinylidene fluoride--hexafluoropropylene) (PVdF-HFP) polymer is a frequently utilized system. Considering that PVdF-HFP should be a poor solvent for cation salts, it is counterintuitive that this is a functional host material for SPEs.

A method for modelling polymer electrolyte decomposition during the Li-nucleation process in Li-metal batteries.

Elucidating the complex degradation pathways and formed decomposition products of the electrolytes in Li-metal batteries remains challenging. So far, computational studies have been dominated by studying the reactions at inert Li-metal surfaces. In contrast, this study combines DFT and AIMD calculations to explore the Li-nucleation process for studying interfacial reactions during Li-plating by introducing Li-atoms close to the metal surface.

Carbonyl-Containing Solid Polymer Electrolyte Host Materials: Conduction and Coordination in Polyketone, Polyester, and Polycarbonate Systems.

Research on solid polymer electrolytes (SPEs) is now moving beyond the realm of polyethers that have dominated the field for several decades. A promising alternative group of candidates for SPE host materials is carbonyl-containing polymers. In this work, SPE properties of three different types of carbonyl-coordinating polymers are compared: polycarbonates, polyesters, and polyketones.

Improving the Electrochemical Stability of a Polyester-Polycarbonate Solid Polymer Electrolyte by Zwitterionic Additives.

Rechargeable batteries with solid polymer electrolytes (SPEs), Li-metal anodes, and high-voltage cathodes like LiNi Mn Co O (NMC) are promising next-generation high-energy-density storage solutions. However, these types of cells typically experience rapid failure during galvanostatic cycling, visible as an incoherent voltage noise during charging. Herein, two imidazolium-based zwitterions, with varied sulfonate-bearing chain length, are added to a poly(ε-caprolactone--trimethylene carbonate):LiTFSI electrolyte as cycling-enhancing additives to study their effect on the electrochemical stability of the electrolyte and the cycling performance of half-cells with NMC cathodes.

Correction: Quantifying the ion coordination strength in polymer electrolytes.

Correction for 'Quantifying the ion coordination strength in polymer electrolytes' by Rassmus Andersson , , 2022, https://doi.org/10.1039/d2cp01904c.

Quantifying the ion coordination strength in polymer electrolytes.

In the progress of implementing solid polymer electrolytes (SPEs) into batteries, fundamental understanding of the processes occurring within and in the vicinity of the SPE are required. An important but so far relatively unexplored parameter influencing the ion transport properties is the ion coordination strength. Our understanding of the coordination chemistry and its role for the ion transport is partly hampered by the scarcity of suitable methods to measure this phenomenon.

Dissecting the Solid Polymer Electrolyte-Electrode Interface in the Vicinity of Electrochemical Stability Limits.

Proper understanding of solid polymer electrolyte-electrode interfacial layer formation and its implications on cell performance is a vital step toward realizing practical solid-state lithium-ion batteries. At the same time, probing these solid-solid interfaces is extremely challenging as they are buried within the electrochemical system, thereby efficiently evading exposure to surface-sensitive spectroscopic methods. Still, the probing of interfacial degradation layers is essential to render an accurate picture of the behavior of these materials in the vicinity of their electrochemical stability limits and to complement the incomplete picture gained from electrochemical assessments.

Controlling the Emission Zone by Additives for Improved Light-Emitting Electrochemical Cells.

The position of the emission zone (EZ) in the active material of a light-emitting electrochemical cell (LEC) has a profound influence on its performance because of microcavity effects and doping- and electrode-induced quenching. Previous attempts of EZ control have focused on the two principal constituents in the active material-the organic semiconductor (OSC) and the mobile ions-but this study demonstrates that it is possible to effectively control the EZ position through the inclusion of an appropriate additive into the active material. More specifically, it is shown that a mere modification of the end group on an added neutral compound, which also functions as an ion transporter, results in a shifted EZ from close to the anode to the center of the active material, which translates into a 60% improvement of the power efficiency.

The role of coordination strength in solid polymer electrolytes: compositional dependence of transference numbers in the poly(ε-caprolactone)-poly(trimethylene carbonate) system.

Both polyesters and polycarbonates have been proposed as alternatives to polyethers as host materials for future polymer electrolytes for solid-state lithium-ion batteries. While being comparatively similar functional groups, the electron density on the coordinating carbonyl oxygen is different, thereby rendering different coordinating strength towards lithium ions. In this study, the transport properties of poly(ε-caprolactone) and poly(trimethylene carbonate) as well as random copolymers of systematically varied composition of the two have been investigated, in order to better elucidate the role of the coordination strength.

Overcoming the Obstacle of Polymer-Polymer Resistances in Double Layer Solid Polymer Electrolytes.

Double-layer solid polymer electrolytes (DLSPEs) comprising one layer that is stable toward lithium metal and one which is stable against a high-voltage cathode are commonly suggested as a promising strategy to achieve high-energy-density lithium batteries. Through in-depth EIS analysis, it is here concluded that the polymer-polymer interface is the primary contributor to electrolyte resistance in such DLSPEs consisting of polyether-, polyester-, or polycarbonate-bad SPEs. In comparison to the bulk ionic resistance, the polymer-polymer interface resistance is approximately 10-fold higher.

Elimination of Fluorination: The Influence of Fluorine-Free Electrolytes on the Performance of LiNiMnCoO/Silicon-Graphite Li-Ion Battery Cells.

In the quest for environmentally friendly and safe batteries, moving from fluorinated electrolytes that are toxic and release corrosive compounds, such as HF, is a necessary step. Here, the effects of electrolyte fluorination are investigated for full cells combining silicon-graphite composite electrodes with LiNiMnCoO (NMC111) cathodes, a viable cell chemistry for a range of potential battery applications, by means of electrochemical testing and postmortem surface analysis. A fluorine-free electrolyte based on lithium bis(oxalato)borate (LiBOB) and vinylene carbonate (VC) is able to provide higher discharge capacity (147 mAh g ) and longer cycle life at C/10 (84.

Restricted Ion Transport by Plasticizing Side Chains in Polycarbonate-Based Solid Electrolytes.

Increasing the ionic conductivity has for decades been an overriding goal in the development of solid polymer electrolytes. According to fundamental theories on ion transport mechanisms in polymers, the ionic conductivity is strongly correlated to free volume and segmental mobility of the polymer for the conventional transport processes. Therefore, incorporating plasticizing side chains onto the main chain of the polymer host often appears as a clear-cut strategy to improve the ionic conductivity of the system through lowering of the glass transition temperature ( ).

Temperature effects on the ionic conductivity in concentrated alkaline electrolyte solutions.

Alkaline electrolyte solutions are important components in rechargeable batteries and alkaline fuel cells. As the ionic conductivity is thought to be a limiting factor in the performance of these devices, which are often operated at elevated temperatures, its temperature dependence is of significant interest. Here we use NaOH as a prototypical example of alkaline electrolytes, and for this system we have carried out reactive molecular dynamics simulations with an experimentally verified high-dimensional neural network potential derived from density-functional theory calculations.

Oligomer Electrolytes for Light-Emitting Electrochemical Cells: Influence of the End Groups on Ion Coordination, Ion Binding, and Turn-on Kinetics.

The electrolyte is an essential constituent of the light-emitting electrochemical cell (LEC), since its operating mechanism is dependent on the redistribution of mobile ions in the active layer. Recent developments of new ion transporters have yielded high-performance devices, but knowledge about the interactions between the ionic species and the ion transporters and the influence of these interactions on the LEC performance is lacking. We therefore present a combined computational and experimental effort that demonstrates that the selection of the end group in a star-branched oligomeric ion transporter based on trimethylolpropane ethoxylate has a paramount influence on the ionic interactions in the electrolyte and thereby also on the performance of the corresponding LECs.

Publisher Correction: The Weak Microcavity as an Enabler for Bright and Fault-tolerant Light-emitting Electrochemical Cells.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Ion-Conductive and Thermal Properties of a Synergistic Poly(ethylene carbonate)/Poly(trimethylene carbonate) Blend Electrolyte.

Electrolytes comprising poly(ethylene carbonate) (PEC)/poly(trimethylene carbonate) (PTM C) with lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) are prepared by a simple solvent casting method. Although PEC and PTMC have similar chemical structures, they are immiscible and two glass transitions are present in the differential scanning calorimetry (DSC) measurements. Interestingly, these two polymers change to miscible blends with the addition of LiTFSI, and the ionic conductivity increases with increasing lithium salt concentration.

The Weak Microcavity as an Enabler for Bright and Fault-tolerant Light-emitting Electrochemical Cells.

The light-emitting electrochemical cell (LEC) is functional at substantial active-layer thickness, and is as such heralded for being fit for low-cost and fault-tolerant solution-based fabrication. We report here that this statement should be moderated, and that in order to obtain a strong luminous output, it is fundamentally important to fabricate LEC devices with a designed thickness of the active layer. By systematic experimentation and simulation, we demonstrate that weak optical microcavity effects are prominent in a common LEC system, and that the luminance and efficiency, as well as the emission color and the angular intensity, vary in a periodic manner with the active-layer thickness.