Polypyrrole–MnO₂-Coated Textile-Based Flexible-Stretchable Supercapacitor with High Electrochemical and Mechanical Reliability

Abstract

Carbon-nanotube (CNT)-based textile supercapacitors with MnO2 nanoparticles have excellent power and energy densities, but MnO2 nanoparticles can be delaminated during charge-discharge cycles, which results in significant degradation in capacitance. In this study, polypyrrole conductive polymer was coated on top of MnO2 nanoparticles that are deposited on CNT textile supercapacitor to prevent delamination of MnO2 nanoparticles. An increase of 38% in electrochemical energy capacity to 461 F/g was observed, while cyclic reliability also improved, as 93.8% of energy capacity was retained over 10 000 cycles. Energy density and power density were measured to be 31.1 Wh/kg and 22.1 kW/kg, respectively. An in situ electrochemical-mechanical study revealed that polypyrrole-MnO2-coated CNT textile supercapacitor can retain 98.5% of its initial energy capacity upon application of 21% tensile strain and showed no observable energy storage capacity change upon application of 13% bending strain. After imposing cyclic bending of 750 000 cycles, the capacitance was retained to 96.3%. Therefore, the results from this study confirmed for the first time that the polypyrrole-MnO2-coated CNT textile can reliably operate with high energy and power densities with in situ application of both tensile and bending strains.

α-Fe2O3-Based Core-Shell-Nanorod–Structured Positiveand Negative Electrodes for a High-Performance α-Fe2O3/C//α-Fe2O3/MnOxAsymmetric Supercapacitor

“…7c, α 44 and also some carbon/graphene based SSCs, 45,46 and are comparable to that reported for VO x //VN-ASCs, i.e., 0.61 mWh/cm 3 , 0.5 mA/cm 2 . 39 The highest volumetric-power-density values for the present ASCs are almost similar, i.e., ∼155 mW/cm 3 at the load current of 7 mA, whereas the gravimetric power density is found to be higher for α- densities of the assembled ASCs are also compared with those reported in the literature 9,10,12,41,[47][48][49][50][51] and are shown in the Fig. 7c, which also suggest superior performance for the supercapacitors reported in this study.…”

Mechanical Analyses and Structural Design Requirements for Flexible Energy Storage Devices

“…[62] This setup was first used to evaluate bending testing of flexible display through synchronous data acquisition of electrical resistance at different bending radii, and is currently being extended to bending testing of flexible energy storage devices. [63,64] However, the bending shape is not exactly a perfect cylinder, and the bending deformation and stress are non-uniform at different positions of curved surface. Bending radius in the collapsing radius geometry are often overestimated, and the reliable radii obtained by the mandrel method www.advancedsciencenews.com with a given radius is around 20% smaller than half distance between two plates as obtained by numeral measurements based on optical fibers.…”

“…Yun et al proposed a modified method similar to the nominal collapsing radius method to ensure that the entire portion of their polypyrrole/MnO 2 supercapacitors can be tested by lateral movement of the lower plate. [63] The gap between two parallel plates was regarded as the double bending radius, and the center portion of the flexible textile can be bent and straightened repeatedly by lateral motion of the lower plate as shown in Figure 6c. As mentioned previously, collapsing radius geometry overestimates the bending radius, and deliberate mechanical theories should be considered to match the bending deformation and strain distribution.…”

“…[63] In the case of black-phosphorus (BP) nanoflakebased flexible all-solid-state SCs, the researchers compared the mechanical properties of two films with thicknesses of approximately 2 and 5 µm in alternate bending and flat states by monitoring their CV curves and capacitance. The thinner film can be bent up to more than 5000 times without any sign of failure, whereas the thicker film fails after bending for only 500 times.…”

Recent advances and challenges of stretchable supercapacitors based on carbon materials

“…After loading of PPy, the specific capacitance on coated fabric increased to 125.1 F g −1 with 60% elongation. Yun et al [104] have further reported PPy-MnO 2 -coated CNT textile SC (Fig. 6b), which can reliably operate with high energy (31.1 W h kg −1 ) and power densities (22.1 kW kg −1 ) with in situ application of both tensile and bending strains.…”