Nonconjugated Redox-Active Polymer Mediators for Rapid Electrocatalytic Charging of Lithium Metal Oxides

For rapid charging of lithium-ion batteries, a series of novel electrode-active materials have been studied. However, those materials suffered from replacing conventional metal oxides, such as LiCoO2 and LiFePO4, because of the strict performance criteria for commercialization. As an alternative approach, we propose the hybridization of the conventional inorganic active materials with organic redox-active polymers which are characterized by fast electrode kinetics. A new robust organic-radical-substituted polyether was synthesized to yield one of the highest charge transportabilities of nonconjugated polymers with a charge diffusion coefficient of 10–7 cm2/s. The hybrid electrode of LiFePO4 and a small amount of the polymer was able to be charged within several minutes by virtue of the electrocatalytic oxidation of the metal oxide with the radical polymer. In addition, several 4 V class organic redox-active polymers were synthesized for the hybrid with LiCoO2. After hybridization, the LiCoO2 electrodes could also be charged within several minutes with the reduced overvoltages.