Asymmetric Multi‐Site Ion Exchange in Porous Carbon Electrodes

ABSTRACT Ion transport in porous carbon electrodes underpins the performance of electrochemical energy storage and separation technologies, yet exchange dynamics within heterogeneous pore networks remain difficult to quantify. Here, we present a rigorous analytical framework for extracting quantitative ion‐exchange kinetics from two‐dimensional exchange spectroscopy (2D EXSY) NMR, explicitly accounting for asymmetric ion populations, relaxation effects, and microscopic reversibility. By describing exchange using a lognormal rate distribution, the framework captures intrinsic dynamic heterogeneity and overcomes limitations of conventional discrete‐site models. Applied to aqueous LiTFSI electrolytes confined in mesoporous CMK‐3 and hierarchically structured ST‐CMK‐3 carbons, the method resolves ion‐exchange processes spanning fast near‐surface exchange to slow in‐pore diffusion in two‐ and three‐site systems. We report, to the best of our knowledge, the first observation of three‐site ion exchange in porous electrodes, revealing direction‐dependent ion mobility and enhanced effective diffusion at interconnected micro–mesopore boundaries. These findings establish direct, quantitative links between pore architecture and ion‐transport efficiency. Importantly, the extracted exchange‐rate distributions reflect underlying pore network topology and transport heterogeneity rather than discrete exchange processes. This framework provides a generalizable route to identifying rate‐limiting pathways and guiding the design of porous carbons for high‐rate supercapacitors, capacitive deionization, and gas‐storage applications.