Effect of Cation Size on Solvation and Association with Superoxide Anion in Aprotic Solvents

Abstract

Influence of cation size on solvation strength, diffusion, and kinetics of the association reaction with anions O2− in aprotic solvents, such as acetonitrile and dimethyl sulfoxide, has been investigated by means of molecular dynamics simulations. The work is motivated by the need to understand the molecular nature of the solvent‐induced changes in capacity of Li‐air batteries. We have shown that the dependence of the solvation shell stability on the cation size has a maximum at a particular ion radius that corresponds to a solvent coordination number of 4. The shell stability maximum coincides with the diffusion coefficient minimum. The variation of the cation shell stability has a crucial impact on the kinetics of the cation‐O2− association. We have demonstrated that profound inhibition of the association reaction for Li+ in dimethyl sulfoxide is a result of the lock‐and‐key effect that cannot be described in the framework of Hard Soft Acid Base theory.

The effect of a mixture of an ionic liquid and organic solvent on oxygen reduction reaction kinetics

“…At the same time, the molecular dynamics (MD) method was shown to be a very effective tool for revealing particular mechanisms of the effects of solvent composition on the solvation processes on a molecular scale. With regard to solvation processes in the context of Li-O 2 batteries, MD was previously used to investigate the behaviour of ions both in bulk [26][27][28][29][30] and at interfaces. [31][32][33][34][35] In the current work, using molecular dynamics simulations, we study the effect of the Pyr 14 TFSI ionic liquid concentration in organic solvent DME on the structure and stability of solvation shells around a number of ions involved in the oxygen reduction reaction (Li + and O 2…”

“…At the same time, the molecular dynamics (MD) method was shown to be a very effective tool for revealing particular mechanisms of the effects of solvent composition on the solvation processes on a molecular scale. With regard to solvation processes in the context of Li–O 2 batteries, MD was previously used to investigate the behaviour of ions both in bulk 26–30 and at interfaces. 31–35…”

Coordination Numbers of Bivalent Ions in Organic Solvents

“…The formation of solvation shells around ions has a crucial effect on such processes. Ion solvation affects charge transfer [2,3], interaction with surfaces [4], and the kinetics of chemical interactions [5]. The properties of the solvation shells in solutions based on organic solvents are especially critical in the development of batteries [6][7][8][9][10][11].…”

“…Properties of lithium ions have mainly been considered in theoretical and experimental studies on organic solvents [5,15,16], due to the focus on developing materials for lithium ion batteries. In addition to lithium ion batteries, technologies based on bivalent ions are now being developed.…”

Mixture of an ionic liquid and organic solvent at graphene: interface structure and ORR mechanism

“…Modeling and experiments show that there may be a more complex dependence of the molecular structure of the solvent on its solvation properties. [26][27][28][29][30] The recently proposed strategy of using room-temperature ionic liquids (RTILs) as solvents in lithium-oxygen batteries has received much attention. 1 Their non-volatility and non-flammability, wide electrochemical window, and high stability make them good alternatives to conventional aprotic electrolytes.…”