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.