High Voltage, Long Cycling Organic Cathodes Rendered by In Situ Electrochemical Oxidation Polymerization

Abstract

Organic electrode materials have attracted considerable attention for electrochemical energy storage due to their abundance of elements, tunable molecular structure, and sustainability. However, the application of organic batteries is plagued by their high solubility and low discharge potential, resulting in poor cycle life and low energy density. Here, ([5,15‐bis(4‐diphenylaminophenyl) porphyrin] Cu(II) (CuDTNP) and [5,10,15,20‐tetrakis(4‐diphenylaminophenyl)porphyrin] Cu(II) (CuFTNP)) as cathodes for organic‐lithium batteries are presented. A highly stable cathode (CuFTNP) with high potential (3.82 V) is achieved by introducing triphenylamine groups in the meso‐position of the porphyrin complex due to the self‐polymerization behavior and anion storage during the electrochemical reaction. Benefiting from triphenylamine groups, higher diffusion coefficients (3.93 × 10−9 cm2 s−1) is achieved, ascribed to the enhanced conjugated structure. As a result, a power density of 34.2 kW kg−1, and excellent cycling stability up to 40 000 cycles are achieved. This cathode can also be extended in organic‐sodium batteries with good cycling stability (600 cycles) and high potential (3.60 V). The charge storage mechanism and polymerization behavior are evidenced by in situ FTIR and in situ Raman characterization. This study will provide inspiration for the development of next‐generation organic cathodes with high potential, high power density, and long‐cycle life through molecular design.