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Cite as Nano-Micro Lett. (2019) 11:88 Received: 13 August 2019 Accepted: 26 September 2019 © The Author(s) 2019

https://doi.org/10.1007/s40820-019-0316-7

CNT/High Mass Loading M ­ nO2/Graphene‑Grafted Carbon Cloth Electrodes for High‑Energy Asymmetric Supercapacitors Lulu Lyu1, Kwang‑dong Seong1, Jong Min Kim1, Wang Zhang2, Xuanzhen Jin1, Dae Kyom Kim1, Youngmoo Jeon1, Jeongmin Kang1, Yuanzhe Piao1,3 * * Yuanzhe Piao, [email protected] Graduate School of Convergence Science and Technology, Seoul National University, Seoul 151‑742, Republic of Korea 2 School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, Jiangsu, People’s Republic of China 1

3



Advanced Institutes of Convergence Technology, Suwon 443‑270, Republic of Korea

HIGHLIGHTS • CNT/MnO2/graphene-grafted carbon cloth electrode is designed and achieves high ­MnO2 mass loading (9.1 mg cm−2). • The electrode with favorable electronic/ionic conductivity delivers a large areal capacitance and rate capability. • The assembled asymmetric supercapacitor yields a large energy density of 10.18 mWh cm−3.

ABSTRACT  Flexible supercapaci‑

e−

e−

tor electrodes with high mass load‑ ing are crucial for obtaining favorable

carbon cloth

challenging due to sluggish electron designed CNT/MnO2/graphene-grafted carbon cloth electrodes are prepared by

CNT/MnO2/GCC

e−

electrochemical performance but still and ion transport. Herein, rationally

e−

Graphene

MnO2

CNT

Electrolyte ions

High mass loading

V2O5/ECC 10.18 mWh cm−3

a “graft-deposit-coat” strategy. Due to the large surface area and good conductivity, graphene grafted on carbon cloth offers additional sur‑ face areas for the uniform deposition of ­MnO2 (9.1 mg cm−2) and facilitates charge transfer. Meanwhile, the nanostructured ­MnO2 provides

abundant electroactive sites and short ion transport distance, and CNT coated on M ­ nO2 acts as interconnected conductive “highways” to

accelerate the electron transport, significantly improving redox reaction kinetics. Benefiting from high mass loading of electroactive mate‑ rials, favorable conductivity, and a porous structure, the electrode achieves large areal capacitances without compromising rate capability. The assembled asymmetric supercapacitor demonstrates a wide working voltage (2.2 V) and high energy density of 10.18 mWh cm−3.

KEYWORDS  High mass loading; Flexible pseudocapacitor; Voltage window; Energy density

Vol.:(0123456789)

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Nano-Micro Lett.

1 Introduction Flexible supercapacitors are one of the promising energy storage devices for wearable electronics due to their quick charging/discharging rate, high power density, and long cycle life [1]. However, it is challenging to store a large amount of energy in a confined device area, and further improvement would be necessary for practical applications. According to the equation of E = 0.5 CV2, the energy density (E) can be improved either by increasing the capacitance (C) or widening cell voltage (V). Hence, the combination of two electr