Pyridine-Functionalized Naphthalene Diimide-Based Cross-Linked Polymer for Efficient Supercapacitor Applications

In the electrochemical energy storage system, redox-activeorganicpolymers have great attraction due to their eco-friendly, easily availableraw materials, variation of design architecture with tailoring theirmolecular structure, and excellent redox-active functional groups.In this paper, we designed a novel pyridine-functionalized naphthalenediimide cross-linked polymer as an electrode material. The synthesizednaphthalene diimide appended the pyridine cross-linked polymer withthree-dimensional network structures, showing an outstanding electrochemicalperformance in SC applications. The monomer NDI-PY-AC is synthesizedby using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NDA) andPY-AC by a simple imidization-condensation reaction. Furthermore,the PNDI-PY-AC polymer was synthesized via radicalpolymerization using AIBN as an initiator. The cross-linked PNDI-PY-ACpolymer was confirmed using solid-state C-13 NMR and Fouriertransform infrared (FT-IR) spectroscopic techniques. The PNDI-PY-ACpolymer morphology of the material was examined by field emissionscanning electron microscopy (FE-SEM) and transmission electron microscopy(TEM) images. The specific surface area and porosity of the polymerwere confirmed by the Brunauer-Emmett-Teller (BET) method.The cross-linked-type morphology of the polymer resolved the solubilityissue of the electrode material in the electrolyte. The practicalapplicability of PNDI-PY-AC is evaluated using symmetric two-electrodeSwagelok cell assembly. The PNDI-PY-AC/GF electrode acts as a cathodeand anode in the solid-state synchronous condenser (SSC) device, whichshows a specific capacitance (C (sp)) of202.85 F g(-1) at 0.5 A g(-1) currentdensity. The SSC device shows a high energy density of 49.69 Wh kg(-1) with a power density of 1259.99 W kg(-1) at a discharge current density of 0.5 A g(-1). Weobserved that the PNDI-PY-AC/GF electrode exhibited an original capacitanceretention of 92.86% after 5000 GCD cycles at 2 A g(-1) current density.