α–α Coupling-Dominated PPy Film with a Well-Conjugated Structure for Superlong Cycle Life Supercapacitors

As the electrode of a supercapacitor, polypyrrole (PPy) inevitably suffers from structural rupture during repeated doping/dedoping processes and releases low practical capacitance due to the large amount of aggregation or cross-linking in PPy chains. The coupling mode (α–α, α–β, or β–β coupling) of pyrroles is critical to the conjugated structure, the conductivity, and cycling stability of PPy. Here, we prepared an α–α coupling-dominated PPy film via simple frozen interfacial polymerization. The PPy film with a nanostructure exposes more electrochemical active sites for the electrode, which can enhance the practical capacitance. The high proportion of the α–α coupling mode results in a high degree of large π-conjugation and a planar structure that can effectively improve the reversible ion transport efficiency and promote uniform stress distribution during the charge and discharge process. The assembled symmetric water-based supercapacitor delivers a high specific capacitance of 267.1 F g–1 at 1 A g–1 and 266.7 F g–1 at 5 A g–1 and exhibits an outstanding cycling performance of above 200 F g–1 even after 60,000 cycles.