Developing a p-Toluenesulfonic Acid Monohydrate-Assisted Electrodeposition Method To Synthesize an Additive-Free Polypyrrole Cathode for High-Rate Stability and High Gravimetric/Volumetric Capacity Li-Ion Batteries

For economic and environmental considerations, organic cathode materials are attracting more attention. Particularly, conducting polymers, such as polythiophene, polyphenylene, polypyrrole, etc., are excellent candidates for lithium-ion batteries with high conductivity, structural designability, and unique anion intercalation/deintercalation mechanism. In this work, an electrodeposition approach to synthesize dense and additive-free polypyrrole film electrodes with p-toluenesulfonic acid as a dopant for lithium-ion batteries was provided. For uniform directional growth layer by layer, a thin PPy film (432 nm) cathode delivered a much higher discharge capacity (188.1 mAh g–1 at 85 mA g–1) and capacity retention (87.0% after 300 cycles) than those of thick films (542 and 866 nm). Unlike the gravimetric capacities, different thicknesses of PPy films had similar volumetric capacity, which was around 40 times higher than that of PPy powder materials, providing a direction for the fabrication of large-capacity microbatteries. Surprisingly, the capacities of the batteries would be further increased after leaving alone for a long time, demonstrating advantages for the application of organic materials.