AUTHOR=Cheng Jin , Tao Haolan , Ma Ke , Yang Jie , Lian Cheng , Liu Honglai , Wu Jianzhong 

TITLE=A Theoretical Model for the Charging Dynamics of Associating Ionic Liquids

JOURNAL=Frontiers in Chemical Engineering

VOLUME=4

YEAR=2022

URL=https://www.frontiersin.org/journals/chemical-engineering/articles/10.3389/fceng.2022.852070

DOI=10.3389/fceng.2022.852070

ISSN=2673-2718

ABSTRACT=<p>Association between cations and anions plays an important role in the interfacial structure of room-temperature ionic liquids (ILs) and their electrochemical performance. Whereas great efforts have been devoted to investigating the association effect on the equilibrium properties of ILs, a molecular-level understanding of the charging dynamics is yet to be established. Here, we propose a theoretical procedure combining reaction kinetics and the modified Poisson-Nernst-Planck (MPNP) equations to study the influences of ionic association on the dynamics of electrical double layer (EDL) in response to an applied voltage. The ionic association introduces a new decay length <italic>λ</italic><sub><italic>S</italic></sub> and relaxation time scale <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>τ</mml:mi><mml:mrow><mml:mi>R</mml:mi><mml:mi>C</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mrow><mml:mrow><mml:msub><mml:mi>λ</mml:mi><mml:mi>S</mml:mi></mml:msub><mml:mi>L</mml:mi></mml:mrow><mml:mo>/</mml:mo><mml:mi>D</mml:mi></mml:mrow></mml:mrow></mml:math></inline-formula>, where <italic>L</italic> is the system size and <italic>D</italic> is ion diffusivity, that are distinctively different those corresponding to non-associative systems. Analytical expressions have been obtained to reveal the quantitative relations between the dynamic timescales and the association strength.</p>