Forced ion flux by multi-redox molecule to break diffusion limit and boost electrode process

For any electrode process, the active species reaching the reaction sites of the electrode surface will ultimately become a controlling step, and this depends on the diffusion layer and its thickness. The diffusion layer, however, is not readily modified other than by introducing vigorous stirring. In lithium-ion-based energy storage, the supply of lithium ion to the reaction sites is certainly a rate-limiting step. Herein, we report an unusual type of “forced convection” by introducing a functionalized molecule in the electrode to break the traditional diffusion limit resulting in an alternative mode of mass transfer. The functionalized molecule, methylene blue phosphotungstate (MB-PW12), is designed with multiple redox properties that can “adsorb” and “release” lithium ion during its redox processes. By implanting the MB-PW12 in sulfur cathode matrix, forced lithium-ion flux can be realized, and this also favors polysulfides adsorption and catalysis, thus boosting the sulfur conversion reactions.