Long-Term Cycling Stability of Porphyrin Electrode for Li/Na Charge Storage at High Temperature.

Bipolar redox organic compounds have been considered as potential next-generation electrode materials due to their sustainability, low cost and tunable structure. However, their development is still limited by the poor cycling stability and low energy density ascribed to high dissolution during cycling and the low conductivity of organic molecules. Herein, porphyrin-based bipolar organics of [5,10,15,20-tetrathienylporphinato] M II (M=2 H, Cu (CuTTP)) are proposed as new stable organic electrodes. Enhanced cycling stability is obtained by a temperature-induced in situ polymerization strategy of porphyrin molecules. The resulting polymer exhibits excellent cycling stability up to 10 00 cycles even at a high current density (1000 mA g -1 ) in organic lithium-/sodium-based charge storage devices at 50 °C. In a symmetrical cell using CuTTP as both cathode and anode material a discharge capacity of 72 mAh g -1 is achieved after 600 cycles at 1000 mA g -1 . This strategy would offer a new approach to developing stable energy storage bipolar materials in organic-based devices at high temperature.