Conductive Ni3(HITP)2 MOFs thin films for flexible transparent supercapacitors with high rate capability

The flexible transparent supercapacitors have been considered as one of the key energy-storage components to power the smart portable electronic devices. However, it is still a challenge to explore flexible transparent capacitive electrodes with high rate capability. Herein, conductive Ni3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) thin films are adopted as capacitive electrodes in flexible transparent supercapacitors. The Ni3(HITP)2 electrode possesses the excellent optoelectronic property with optical transmittance (T) of 78.4% and sheet resistance (Rs) of 51.3 Ω sq-1, remarkable areal capacitance (CA) of 1.63 mF cm-2 and highest scan rate up to 5000 mV s-1. The asymmetric Ni3(HITP)2//PEDOT:PSS supercapacitor (T = 61%) yields a high CA of 1.06 mF cm-2 at 3 μA cm-2, which maintains 77.4% as the current density increases by 50 folds. The remarkable rate capability is ascribed to the collaborative advantages of low diffusion resistance and high ion accessibility, resulting from the intrinsic conductivity, short oriented pores and large specific areas of Ni3(HITP)2 films.