Understanding Battery Interfaces by Combined Characterization and Simulation Approaches: Challenges and Perspectives

Driven by the continuous search for improving performances, understanding the phenomena at the electrode/electrolyte interfaces has become an overriding factor for the success of sustainable and efficient battery technologies for mobile and stationary applications. Toward this goal, rapid advances have been made regarding simulations/modeling techniques and characterization approaches, including high-throughput electrochemical measurements coupled with spectroscopies. Focusing on Li-ion batteries, current developments are analyzed in the field as well as future challenges in order to gain a full description of interfacial processes across multiple length/timescales; from charge transfer to migration/diffusion properties and interphases formation, up to and including their stability over the entire battery lifetime. For such complex and interrelated phenomena, developing a unified workflow intimately combining the ensemble of these techniques will be critical to unlocking their full investigative potential. For this paradigm shift in battery design to become reality, it necessitates the implementation of research standards and protocols, underlining the importance of a concerted approach across the community. With this in mind, major collaborative initiatives gathering complementary strengths and skills will be fundamental if societal and environmental imperatives in this domain are to be met

A Roadmap for Transforming Research to Invent the Batteries of the Future Designed within the European Large Scale Research Initiative BATTERY 2030+

This roadmap presents the transformational research ideas proposed by “BATTERY 2030+,” the European large-scale research initiative for future battery chemistries. A “chemistry-neutral” roadmap to advance battery research, particularly at low technology readiness levels, is outlined, with a time horizon of more than ten years. The roadmap is centered around six themes: 1) accelerated materials discovery platform, 2) battery interface genome, with the integration of smart functionalities such as 3) sensing and 4) self-healing processes. Beyond chemistry related aspects also include crosscutting research regarding 5) manufacturability and 6) recyclability. This roadmap should be seen as an enabling complement to the global battery roadmaps which focus on expected ultrahigh battery performance, especially for the future of transport. Batteries are used in many applications and are considered to be one technology necessary to reach the climate goals. Currently the market is dominated by lithium-ion batteries, which perform well, but despite new generations coming in the near future, they will soon approach their performance limits. Without major breakthroughs, battery performance and production requirements will not be sufficient to enable the building of a climate-neutral society. Through this “chemistry neutral” approach a generic toolbox transforming the way batteries are developed, designed and manufactured, will be created

Nanoporous polymer foams derived from high molecular PS-b-P4VP(PDP)(x) for template-directed synthesis approaches

Due to their ability to self-assemble into a variety of periodic nanostructures, block copolymers already play an important role in designing diverse functional materials. A refined way to rationally tailor the morphology of a block copolymer system is the incorporation of varying amounts of an amphiphile e.g. 3-pentadecylphenol (PDP). In order to identify self-assembled structures suitable for the design of various functional materials, different supramolecular complexes of polystyrene-block-poly(4-vinylpyridine)(PDP)(x) (PS-b-P4VP(PDP)(x)) were prepared and mophologically characterized by small-angle X-ray scattering and scanning electron microscopy techniques. Thereby, the focus was set on the cylindrical-to-lamellar region with a minor P4VP(PDP)(x) block. For the first time, the lamellar-in-gyroid morphology was obtained directly by an annealing process. After amphiphile removal, apart from the nanoporous gyroid polymer foam, exceptionally long-range ordered polymer networks with cylindrical pores were obtained. The manifold possible applications of the self-assembled polymer morphologies were exemplarily validated by a template-directed formation of a bicontinuous nickel network via electroless plating

Cyclic voltammetry study of (5-ethoxycarbonylmethylidene-4-oxothiazolidin-2-ylidene)-N-phenylethanamide

As a continuation of our ongoing project on electrochemical properties of push-pull 5-substituted 2-alkylidene-4-oxothiazolidines (1a) differing in substituent R at C5-position and electron withdrawing group (EWG), we nave investigated the electrochemical behaviour of (5-etoxycarbonylmethylidene-4-oxothiazolidin-2-ylidene)-N-phenylethanamide 1a (R: =CHCO2Et; EWG: CONHPh), consisting as a (2E,5Z)/(2Z,5Z) mixture, by cyclic voltammetry in polar as well as non-polar solvent (0.1 M TBAHFP in DMSO and CHCl3, respectively). Cyclic voltammetry at stationary electrode was employed to characterize the electron transfer steps. Based on electrochemical criteria and correlation with the DigiSim simulations, an ECE mechanism, involving two electrochemical steps and one isomerisation step, was suggested

Toward adequate control of internal interfaces utilizing nitrile-based electrolytes

Methods to control internal interfaces in lithium ion batteries often require sophisticated procedures to deposit coating layers or introduceinterphases, which are typically difficult to apply. This particularly holds for protection from parasitic reactions at the current collector,which reflects an internal interface for the electrode composite material and the electrolyte. In this work, electrolyte formulationsbased on aliphatic cyclic nitriles, cyclopentane-1-carbonitrile and cyclohexane-1-carbonitrile, are introduced that allow for successful suppressionof aluminum dissolution and control of internal interfaces under application-relevant conditions. Such nitrile-based electrolytesshow higher intrinsic oxidative and thermal stabilities as well as similar capacity retentions in lithium nickel–manganese–cobalt oxideLiNi3/5Mn1/5Co1/5O2 (NMC622)||graphite based full cells compared to the state-of-the-art organic carbonate-based electrolytes, even whenbis(trifluoro-methane)sulfonimide lithium salt is utilized. Moreover, the importance of relative permittivity, degree of ion dissociation, andviscosity of the applied electrolyte formulations for the protection of current collector interfaces is emphasized

High Voltage LiNi0.5Mn1.5O4/Li4Ti5O12 Lithium Ion Cells at Elevated Temperatures: Carbonate- versus Ionic Liquid-Based Electrolytes

Thanks to its high operating voltage, the LiNi0.5Mn1.5O4 (LNMO) spinel represents a promising next-generation cathode material candidate for Lithium ion batteries. However, LNMO-based full-cells with organic carbonate solvent electrolytes suffer from severe capacity fading issues, associated with electrolyte decomposition and concurrent degradative reactions at the electrode/electrolyte interface, especially at elevated temperatures. As promising alternatives, two selected LiTFSI/pyrrolidinium bis(trifluoromethane-sulfonyl)imide room temperature ionic liquid (RTIL) based electrolytes with inherent thermal stability were investigated in this work. Linear sweep voltammetry (LSV) profiles of the investigated LiTFSI/RTIL electrolytes display much higher oxidative stability compared to the state-of-the-art LiPF6/organic carbonate based electrolyte at elevated temperatures. Cycling performance of the LNMO/Li4Ti5O12 (LTO) full-cells with LiTFSI/RTIL electrolytes reveals remarkable improvements with respect to capacity retention and Coulombic efficiency. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns indicate maintained pristine morphology and structure of LNMO particles after 50 cycles at 0.5C. The investigated LiTFSI/RTIL based electrolytes outperform the LiPF6/organic carbonate-based electrolyte in terms of cycling performance in LNMO/LTO full-cells at elevated temperatures

Lifetime limit of tris(trimethylsilyl) phosphite as electrolyte additive for high voltage lithium ion batteries

The tris(trimethylsilyl) phosphite (TMSPi) is considered as an ideal electrolyte additive for lithium ion batteries. In this work, its positive effect as well as its failure mechanism in a LiPF6 containing electrolyte was studied by means of selected electrochemical, structural and analytical techniques. The LiNi0.5Co0.2Mn0.3O2/graphite cells with TMSPi as electrolyte additive were cycled between 2.8 and 4.6 V. Thanks to the compact cathode electrolyte interphase formed by the oxidative decomposition of TMSPi in a freshly prepared TMSPi containing electrolyte, both the discharge capacity and the cycling stability of cells were enhanced. However, our results also show that TMSPi actually reacts with LiPF6 at room temperature. TMSPi is consumed by this spontaneous reaction after aging for certain time. In addition, a part of the fluorophosphates, generated from the hydrolysis of LiPF6, is bonded to one or two TMS groups, causing a decrease in the fluorophosphate content in the CEI film. Consequently, the cycling stability of the lithium ion cells with aged TMSPi containing electrolyte deteriorates. The obtained results offer important insights into the practical application of TMSPi, which means that TMSPi can only be used as an effective additive in a freshly prepared LiPF6 containing electrolyte

Understanding Battery Interfaces by Combined Characterization and Simulation Approaches: Challenges and Perspectives

International audienceDriven by the continuous search for improving performances, understanding the phenomena at the electrode/electrolyte interfaces has become an overriding factor for the success of sustainable and efficient battery technologies for mobile and stationary applications. Toward this goal, rapid advances have been made regarding simulations/modeling techniques and characterization approaches, including high-throughput electrochemical measurements coupled with spectroscopies. Focusing on Li-ion batteries, current developments are analyzed in the field as well as future challenges in order to gain a full description of interfacial processes across multiple length/timescales; from charge transfer to migration/diffusion properties and interphases formation, up to and including their stability over the entire battery lifetime. For such complex and interrelated phenomena, developing a unified workflow intimately combining the ensemble of these techniques will be critical to unlocking their full investigative potential. For this paradigm shift in battery design to become reality, it necessitates the implementation of research standards and protocols, underlining the importance of a concerted approach across the community. With this in mind, major collaborative initiatives gathering complementary strengths and skills will be fundamental if societal and environmental imperatives in this domain are to be met. \textcopyright 2021 The Authors. Advanced Energy Materials published by Wiley-VCH Gmb

Understanding transport mechanisms in ionic liquid/carbonate solvent electrolyte blends

To unravel mechanistic details of the ion transport in liquid electrolytes, blends of the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr14TFSI), ethylene carbonate (EC) and dimethyl carbonate (DMC) with the conducting salts lithium hexafluorophosphate (LiPF6) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were investigated as a function of the IL concentration. Electrochemical impedance, Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR) and Raman spectroscopy supported by Molecular Dynamics (MD) simulations allowed the structural and dynamic correlations of the ion motions to be probed. Remarkably, we identified that though the individual correlations among different ion types exhibit a clear concentration dependence, their net effect is nearly constant throughout the entire concentration range, resulting in approximately equal transport and transference numbers, despite a monitored cross-over from carbonate-based lithium coordination to a TFSI-based ion coordination. In addition, though dynamical ion correlation could be found, the absolute values of the ionic conductivity are essentially determined by the overall viscosity of the electrolyte. The IL/carbonate blends with a Pyr14TFSI fraction of ∼10 wt% are found to be promising electrolyte solvents, with ionic conductivities and lithium ion transference numbers comparable to those of standard carbonate-based electrolytes while the thermal and electrochemical stabilities are considerably improved. In contrast, the choice of the conducting salt only marginally affects the transport properties