Patterning Islandlike MnO₂ Arrays by Breath-Figure Templates for Flexible Transparent Supercapacitors

Abstract

Although plenty of active materials could be used as supercapacitor electrodes, only limited ones have been engineered to construct transparent supercapacitors. Specially, it is a great challenge to make opaque metal oxides, which often own high energy density, into transparent films. Here, we demonstrate a novel approach to fabricate transparent MnO films for flexible transparent supercapacitors. By utilizing breath-figure polymer films with ordered pores as template, arrays of MnO islands were electrochemically deposited, with high light transmission. The thickness and interspace distance of MnO island arrays could be adjusted by tuning deposition time so that the capacitance and transparency of the electrodes are changed accordingly. Such island array structure can effectively eliminate the internal stress existing in the composite film to avoid cracks during bending operation. The assembled transparent supercapacitor shows a transmittance of 44% at 550 nm and can yield a high capacitance of 4.73 mF/cm at a current density of 50 μA/cm, demonstrating high flexibility and stability.

Experimental and Theoretical Investigation of the Effect of Oxygen Vacancies on the Electronic Structure and Pseudocapacitance of MnO2

“…From the XPS full survey scan spectra (Figure S1 a, Supporting Information), the pure, ROV-2h and OOV-1h MnO 2 samples all clearly showed the presence of O, Mn and Cs ignals;t he Cs ignal was from the reference carbon.F or the Mn 2p spectra (Figure 3a and 3c), two major peaks at 641.4 and 653.1 eV (spin energy separation of 11.7 eV) were assigned to the Mn 2p 3/2 and Mn 2p 1/2 bindinge nergies, respectively,w hich were in good agreement with the characteristic MnO 2 . [43] The Mn 2p 3/2 spectrum was further deconvoluted into two pairs of peaks at 641.1 and 642.3 eV, whereas the Mn 2p 1/2 spectrum was deconvoluted into peaks at 652.5 and 653.7 eV;t he peaks at 641.1, 652.5 eV and 642.3, 653.7 eV were assigned to Mn 3 + and Mn 4 + ,r espectively. [25] The Mn 3s peak for ROV-2h and OOV-1h MnO 2 wass lightly broader than that of pure MnO 2 (Figure S1 b).…”

Metal Mesh as a Transparent Omnidirectional Strain Sensor

“…Porous honeycomb Ag mesh/PDMS films are obtained by the breath‐figure method and PVA transfer process. Briefly, porous polystyrene‐ b ‐poly (acrylic acid) (PS‐ b ‐PAA) film is first prepared on PET as a template by the breath‐figure method . Subsequently, a 15 nm silver film is deposited on the PS‐ b ‐PAA/PET template by vacuum thermal evaporation, forming a Ag mesh/PS‐ b ‐PAA/PET film.…”

“…Fabrication of Honeycomb Ag Film on Polymer Template : Honeycomb PS‐ b ‐PAA polymer template on PET substrate was fabricated by the breath‐figure approach as described in our previous work . Briefly, a PET film was immersed into PS‐ b ‐PAA/CS 2 solution and then pulled out with a constant speed of 200 cm min −1 in an 80% humid airflow.…”

Nano‐Engineered Materials for Transparent Supercapacitors

“…Active materials with ordered array structures are prepared by electrodeposition with the assistance of porous perforated mask, such as breath figure template and anodic aluminum oxide template . After removal of the template, empty space between active material arrays would significantly improve the transparency of supercapacitors.…”

“…Wang et al. electrodeposited MnO 2 into ordered arrays by breath figure template, and used the MnO 2 arrays as electrodes to assemble transparent supercapacitors, as shown in Figure a and 5b . Due to the existence of breath figure template, during the electrodeposition process, MnO 2 was grown into separated islands instead of a uniform film.…”