Pore-Scale Textural Changes upon Ion Adsorption in Voltage-Polarized Nanoporous Carbon Electrodes

This study investigates the dynamic behavior of aqueous electrolytes in porous carbon electrodes under voltage, with a focus on the impact of electrode flexibility on the pore texture. Utilizing a constant-voltage approach with a reactive interaction potential, we examine the heterogeneous charge distribution on carbon atoms within the electrode, revealing the role of chemical defects. Comparisons between flexible- and frozen-electrode models highlight the significant influence of flexibility on ion-adsorption intake and dynamics. The total ion docking for <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mi>Cs</a:mi></a:math><d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:msup><d:mi/><d:mo>+</d:mo></d:msup></d:math> and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><g:mi>Cl</g:mi></g:math><j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><j:msup><j:mi/><j:mo>−</j:mo></j:msup></j:math> is overestimated by a factor of 2–3 in the frozen approximation, depending on the voltage. Furthermore, we explore ion-induced swelling and modifications in pore-size distribution for <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><m:mi>Li</m:mi></m:math><p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><p:msup><p:mi/><p:mo>+</p:mo></p:msup></p:math>, <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><s:mi>Na</s:mi></s:math><v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><v:msup><v:mi/><v:mo>+</v:mo></v:msup></v:math>, <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><y:mrow><y:mrow><y:mi mathvariant="normal">K</y:mi></y:mrow></y:mrow></y:math><cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><cb:msup><cb:mi/><cb:mo>+</cb:mo></cb:msup></cb:math>, and <fb:math xmlns:fb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><fb:mi>Cs</fb:mi></fb:math><ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><ib:msup><ib:mi/><ib:mo>+</ib:mo></ib:msup></ib:math> ions, revealing that different alkali ions induce different degrees of swelling leading to nanoscale plasticity. This permanent deformation induces aging and underlines the importance of the flexibility. The study provides valuable insights into the intricate interplay between ion interactions and porous carbon flexibility.