Molecular Engineering of Polyaniline with Ultrathin Polydopamine and Monolayer Graphene for All-Solid-State Flexible Microsupercapacitors

The use of conductive polyaniline (PANI) in energy storage has been extensively explored during the past several decades. Despite the significant progress, there is still a need for effective and simple methods to tune the structure and electrochemical performance of PANI at the molecular level, which are beyond conventional methods of mixing PANI with other materials. Here, we report a new approach for molecular engineering of PANI with ultrathin polydopamine and continuous monolayer graphene using a reactive layer-by-layer (LbL) deposition approach. Microsupercapacitors (MSCs) were fabricated based on the combination of reactive LbL deposition and lithography patterning. We discovered that the introduction of an ultrathin polydopamine layer between PANI layers leads to significant changes to the molecular structure, intermolecular spacing, and morphology of PANI. Those changes result in substantial improvements in the capacitance, stability, and flexibility of the hybrid MSCs. Furthermore, the use of continuous monolayer graphene as an atomically thin substrate for in situ polymerization of aniline leads to ultrathin PANI film with reduced charge-transfer resistance and improved electrochemical properties and stability. This work provides valuable insight into the structure and property control of conducting polymers, as well as the fabrication of soft and flexible energy storage devices.