Highly Ordered, Ultralong Mn‐Based Nanowire Films with Low Contact Resistance as Freestanding Electrodes for Flexible Supercapacitors with Enhanced Performance

Nanowires (NWs) have attracted considerable scientific interest in fabricating high performance electronic and optical devices. Especially, highly ordered nanowires could exhibit unique properties such as good intrinsic electrical conductivity and fast electrons transportation. In this work, freestanding films from ultralong manganese dioxide/polyaniline (MNW/PANI) coaxial NWs (~200μm) with highly ordered structure have been fabricated at oil/water interface and then used as flexible electrodes. The ultralong MNW/PANI coaxial NWs with highly ordered orientation provide longer and continuous electron transportation pathway in the electrode compared to disordered NWs, which could greatly reduce the inter-junction resistance between NWs in a film to achieve high capacitance. The electrodes based on ordered NWs show much lower contact resistance (10.8 Ω cm-2) compared with the randomly oriented ones (96.5 Ω cm-2). The thin film supercapacitors (TFSCs) based on well-ordered MNW/PANI NWs possess mechanical flexibility, high specific capacitances 64.54 mF cm-2 (corresponds to 121.77 F g-1 at mass loading density 0.53 mg cm-2), high energy/powder density (44.80 mWh cm-3, 580 mW cm-3) as well as good cycle stability with high capacitance retention (98%) after 2000 cycles.