Isidora Cekic-Laskovic

Synergistic Effect of Blended Components in Nonaqueous Electrolytes for Lithium Ion Batteries

Application of different electrolyte components as blends in nonaqueous electrolyte formulations represents a viable approach towards improving the overall performance and reliability of a lithium ion battery cell. By combining the advantages of different electrolyte constituents, cell chemistry can be optimized and tailored for a specific purpose. In this paper, the current progress on possibilities, advantages, as well as limitations of blended nonaqueous electrolyte formulations, including solvent, salt and additive blends is reviewed and discussed. Emphasis is set on the physicochemical, electrochemical, and safety aspects. In addition, the aim of this review is to provide perspective and possible strategy for further and future development of blended nonaqueous electrolytes with long life, high energy density, high power, and adequate safety at competitive manufacturing costs. The provided overview and perspective on blended nonaqueous electrolyte formulations should encourage researchers to proceed with further and deeper investigations in this promising field of advanced batteries.

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.

Alternative Single-Solvent Electrolytes Based on Cyanoesters for Safer Lithium-Ion Batteries.

To identify alternative single-solvent-based electrolytes for application in lithium-ion batteries (LIBs), adequate computational methods were applied to screen specified physicochemical and electrochemical properties of new cyanoester-based compounds. Out of 2747 possible target compounds, two promising candidates and two structurally equivalent components were chosen. A constructive selection process including evaluation of basic physicochemical properties as well assessing the compatibility towards graphitic anodes was initiated to identify the most promising candidates. With addition of a film-forming additive in a low concentration, the most promising candidate showed an adequate long-term cycling stability with LiNi1/3 Mn1/3 Co1/3 O2 [NMC(111)] in a full-cell setup using graphite as anode material. The main advantages of the new electrolyte formulation are related to its good thermal behavior, especially with regard to safety in combination with satisfying electrochemical performance.

Interfaces and Materials in Lithium Ion Batteries: Challenges for Theoretical Electrochemistry

Energy storage is considered a key technology for successful realization of renewable energies and electrification of the powertrain. This review discusses the lithium ion battery as the leading electrochemical storage technology, focusing on its main components, namely electrode(s) as active and electrolyte as inactive materials. State-of-the-art (SOTA) cathode and anode materials are reviewed, emphasizing viable approaches towards advancement of the overall performance and reliability of lithium ion batteries; however, existing challenges are not neglected. Liquid aprotic electrolytes for lithium ion batteries comprise a lithium ion conducting salt, a mixture of solvents and various additives. Due to its complexity and its role in a given cell chemistry, electrolyte, besides the cathode materials, is identified as most susceptible, as well as the most promising, component for further improvement of lithium ion batteries. The working principle of the most important commercial electrolyte additives is also discussed. With regard to new applications and new cell chemistries, e.g., operation at high temperature and high voltage, further improvements of both active and inactive materials are inevitable. In this regard, theoretical support by means of modeling, calculation and simulation approaches can be very helpful to ex ante pre-select and identify the aforementioned components suitable for a given cell chemistry as well as to understand degradation phenomena at the electrolyte/electrode interface. This overview highlights the advantages and limitations of SOTA lithium battery systems, aiming to encourage researchers to carry forward and strengthen the research towards advanced lithium ion batteries, tailored for specific applications.

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.