The Metallocene Battery: Ultrafast Electron Transfer Self Exchange Rate Accompanied by a Harmonic Height Breathing

The first all‐metallocene rechargeable battery consisting of poly‐cobaltocenium/‐ and poly‐ferrocene/reduced graphene oxide composites as anode and cathode was prepared. The intrinsically fast ET self‐exchange rate of metallocenes was successfully combined with an efficient ion‐percolation achieved by molecular self‐assembly. The resulting battery materials show ideal Nernstian behavior, is thickness scalable up to >1.2 C cm(−2), and exhibit high coulombic efficiency at ultrafast rates (200 A g(−1)). Using aqueous LiClO(4), the charge is carried exclusively by the anion. The ClO(4) (−) intercalation is accompanied by a reciprocal height change of the active layers. Principally, volume changes in organic battery materials during charging/discharging are not desirable and represent a major safety issue. However, here, the individual height changes—due to ion breathing—are reciprocal and thus prohibiting any internal pressure build‐up in the closed‐cell, leading to excellent cycling stability.