Electrolytes: From a Thorn Comes a Rose, and from a Rose, a Thorn

Abstract

In this article we take a stroll through the metaphorical rose garden, part of the flower garden, that is electrochemical storage systems. We take a closer look at batteries as the center‐pieces – the roses – and especially at the system component of batteries, the electrolyte and its development, throughout history. Just as a rose can only develop its unique beauty when taken good care of and provided with clean water and suitable nutrients, a battery cell cannot function without its electrolyte; the seemingly trivial component that has to juggle a multitude of requirements in order to make batteries truly bloom.

Specific Ion Effects in Different Media: Current Status and Future Challenges

“…In addition, specific ion effects are usually observed and studied for low salt concentrations . Hence, it is often overseen that specific ion effects are also evident in highly concentrated electrolyte solutions. ,, As an important example, recent studies have shown that aqueous lithium salt solutions at high concentrations form profoundly stable ion aggregate states with long-range ordering effects which beneficially modify the electrochemical stability of the medium. , In addition to water, comparable findings were also reported for other electrolyte solvents like adiponitrile or sulfoniles. , Thus, the formation of these states at high concentrations above 1 mol/L is of fundamental importance for technological applications, and recent results revealed that mainly anion-specific effects play a decisive role . The consideration of such high concentrations requires the combination of thermodynamic descriptions in terms of ion activities as well as further thermodynamic properties like nonideal behavior.…”

“…Such findings have broad consequences for various industrial and technological applications. ,,, Noteworthy, the concept of volcano plots does not distinguish between different ion pairing states including contact ion pairs (CIP), solvent-shared (1SP) or solvent-separated (2SP) arrangements as well as ion aggregate (AGG) conformations. , A schematic picture of the corresponding ion pairing states is presented in Figure . In contrast to the simplicity of these considerations, recent results showed that most ion pair combinations reveal fast dynamic rearrangements, such that the global stability of the individual states remains questionable. , In addition to the ionic species, also solvent and further cosolvent species as well as the corresponding concentrations affect the occurrence of ion pairing states. , On the basis of such assumptions, specifically the tailor-made design of electrolyte formulations for modern electrochemical storage devices with regard to improved charge transport is in the scope of current research. , In the remainder of this Perspective, we will present a more detailed rationale for such pairing effects which can be brought into relation with the empirical observations.…”

“…35,36 On the basis of such assumptions, specifically the tailor-made design of electrolyte formulations for modern electrochemical storage devices with regard to improved charge transport is in the scope of current research. 32,37 In the remainder of this Perspective, we will present a more detailed rationale for such pairing effects which can be brought into relation with the empirical observations. .…”

High‐Throughput Experimentation and Computational Freeway Lanes for Accelerated Battery Electrolyte and Interface Development Research

“…LR is based on a specification of Equation ( 1) via η = + y Xb (6) where X is the matrix where each of the M rows contains the p features (e.g., concentrations) per experiment. The vector b contains all the p regression coefficients, which one wants to estimate via the regression procedure.…”

“…[ 3 ] Although the role of the electrolyte is often considered trivial, its choice is actually crucial, and is based on criteria that can differ significantly dependent on application. [ 4–7 ] Due to the complexity of electrolyte formulation, determined by the physicochemical properties of its components, namely, inorganic fluorinated salts, organic solvents/cosolvents, and functional additives, the overall cell performance is inevitably accompanied by side reactions. The electrolyte is concomitantly unified to 3D interphases that originate from the high reactivity of the electrodes and the intrinsic instability of electrolyte components toward these electrodes.…”