Electropolymerization of 1,5-diaminonaphthalene in water-in-reline electrolyte as supercapacitor electrode material

Developing novel conducting polymers as electrode materials with improved charge storage capacity and cycling stability is important for energy storage devices. Here, 1,5-diaminonaphthalene is for the first time electropolymerized from a water-in-reline (reline: a deep eutectic solvent composed of choline chloride and urea with a molar ratio 0.5) solution with perchloric acid at 323 K. The morphology of the poly(1,5-diaminonaphthalene) deposited on carbon cloth (PDAN/CC) changes from granular to dense with extended electropolymerization duration. The electrochemical charge storage performance of the PDAN/CC is investigated, and the PDAN/CC-10 exhibits the specific capacity of 57.89 mAh g−1 at the current density of 1 A g−1 using the three-electrode test in 1 M H2SO4. Ex-situ characterizations reveal the mechanism of charge storage of PDAN/CC, where the charge is stored by the amino/imino redox processes, together with (de)intercalation of the electrolyte anion. A solid-state supercapacitor using two PDAN/CC-10 and polyvinylalcohol (PVA)-H2SO4 gel is constructed, and its specific energy reaches 5.2 Wh kg−1 at the power density of 312.6 W kg−1 (0.5 A g−1). After 3000 repetitive charge-discharge cycles at 5 A g−1, 64.1 % of the initial specific capacity is maintained, which is probably caused by the degradation and dissolution of PDAN along with the repetitive charging and discharging.