The properties of highly compressible electrochemical capacitors based on polypyrrole/melamine sponge-carbon fibers

With development of personal electronic devices, special energy storage devices such as compressible electrochemical capacitors (CECs) are becoming important. Here, we use artificial melamine sponge (aMS) as matrix, carbon fibers (CFs) as wires to stitch aMS to prepare compressible substrates (aMS-CFs). Polypyrrole (PPy) is then deposited on the aMS-CFs via gas-phase polymerization to get the compressible electrodes of PPy/aMS-CFs. The preparation conditions are optimized and the obtained samples are characterized in detail, the optimized PPy/aMS-CFs possesses a specific capacitance of 239.0 F g−1 based on the PPy. The testing results show that the assembled symmetric CECs (PPy/aMS-CFs//PPy/aMS-CFs) exhibit excellent electrochemical performance under different compressive strains, and change their capacitive properties with the change of the pressure. Compared with the normal condition, the capacitance of the optimized CEC increases significantly at higher scan rates but it is almost unchanged at 2 mV s−1 when the compression level reach 60%. Meanwhile, even after 1000 cycles of repeated compression with 60% compression rate, the CEC can still maintain good cyclic stability (84.4% capacitance retention after 10000 cycles). This kind of CEC may have potential application prospect in the field of personal electronics.