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An Asymmetric Supercapacitor with Both Ultra-High Gravimetric and Volumetric Energy Density Based on 3D Ni(OH)2/ MnO2@Carbon Nanotube and Activated Polyaniline-Derived Carbon Juanjuan Shen, Xiaocheng Li, Liu Wan, Kun Liang, Beng Kang Tay, Ling-Bin Kong, and Xingbin Yan ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b12370 • Publication Date (Web): 12 Dec 2016 Downloaded from http://pubs.acs.org on December 12, 2016
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ACS Applied Materials & Interfaces
An Asymmetric Supercapacitor with Both Ultra-High Gravimetric and Volumetric Energy Density Based on 3D Ni(OH)2/MnO2@Carbon Nanotube and Activated Polyaniline-Derived Carbon Juanjuan Shen,
†,§,#
Xiaocheng Li,*,
§, †,
‡
Liu Wan,§ Kun Liang, Beng Kang Tay,
‡
Lingbin Kong, † and Xingbin Yan§
†
State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metal,
Lanzhou University of Technology, Lanzhou 730050, P. R. China §
Laboratory of Clean Energy Chemistry and Materials, Lanzhou Institute of Chemical
Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China #
University of Chinese Academy of Science, Beijing, 100080, P. R. China
‡
School of Electrical & Electronic Engineering, Nanyang Technological University,
50 Nanyang Avenue, Singapore 639798
KEYWORDS: asymmetric supercapacitor, energy density, high mass loading, nickel hydroxide/manganese dioxide composite, activated polyaniline-derived carbon
ABSTRACT: Development of the supercapacitor device with both high gravimetric and volumetric energy density is one of the most important requisite for their practical application in energy storage/conversion systems. Currently, improvement of the 1
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gravimetric/volumetric energy density of supercapacitor is restricted by the insufficient utilization of positive materials at high loading density and the inferior capacitive behavior of negative electrodes. To solve these problems, we elaborately designed and prepared a 3D core-shell structured Ni(OH)2/MnO2@carbon nanotube (CNT) composite via a facile solvothermal process by using the thermal chemical vapor deposition grown-CNTs as support. Owing to the superiorities of core-shell architecture in improving the service efficiency of pseudocapacitive materials at high loading density, the prepared Ni(OH)2/MnO2@CNT electrode demonstrated a high capacitance value of 2648 F g-1 (1 A g-1) at a high loading density of 6.52 mg cm-2. Coupled with high performance activated polyaniline-derived carbon (APDC, 400 F g-1 at 1 A g-1), the assembled Ni(OH)2/MnO2@CNT//APDC asymmetric device delivered both high gravimetric and volumetric energy density (126.4 Wh kg-1 and 10.9 mWh cm-3, respectively), together with superb rate performance and cycling lifetime. Moreover, we demonstrate an effective approach for building high performance supercapacitor with high gravimetric/volumetric energy density.
1. INTRODUCTION Development of energy storage systems with high gravimetric and volumetric energy/power density is one of the major components of the renewable energy projects built by the government of the countries all over the world. Supercapacitors have attracted tremendous attention due to their low cost, high power density, and long cycling life characteristics.1-4 Traditionally, carbonaceous materials are extensively used as the predominant component of supercapacitor devices. However, due to the 2
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low capacitive performance, it is great difficult for carbon-based symmetric supercapacitor devices to meet the rigorous requirements of external power load for gravimetric/volumetric energy density.5-8 It has been established that the improvement of the energy density (E) of a supercapacitive device can be realized by maximizing the capacitance value (C) or operating window (U) of the device, as decided by the formula E = CU 2 2 .9,10 In aqueous electrolyte, since the operation voltage of asymmetric
supercapacitor
(ASC)
device
is
restricted
by
the
decomposition voltage of water, the sole strategy for improving the energy density of the aqueous electrolyte-based ASC is to raise the capacitance value of the device (Ccell), which depends on that of positive (C+) and negative electrode(C-), according to the formula 1 C cell = 1 C + + 1 C − . Therefore, it is urgent demand to design and construct positive electrodes with high gravimetric/volumetric capacitance and matching negative materials. For positive electrodes, it has been accepted that pseudocapacitive materials exhibit higher specific capacitance than traditional carbonaceous materials.6,11 Typical pseudocapacitive materials include RuO2,3 MnO2,12 NiO,13 Ni(OH)2,14,15 Co3O4,16 Fe2O3,17 and their binary components, such as NiCo layered double hydroxide (LDH),18 NiAl LDH,19 NiZn LDH,20 NiCo2O4,21 and Ni(OH)2/NiO.22 Among them, the electrochemical performance of binary metal oxide/hydroxides is far superior to that of individual ones because of the synergic effect between two components.23,24 Inspired by the achievements in binary metal oxide/hydroxide, Ni(OH)2/MnO2 composite has recently received considerable interest due to their rich reserves and environmentally 3
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benign nature. Theoretically, the doping of Ni atom with d-electrons in MnO2 can greatly enhance the electrochemical behavior of MnO2 by increasing conductivity, active site density and roughness.24 On the other hand, the doping of Mn ions in interlamellar space of turbostratic α-Ni(OH)2 can stabilize its crystal structure in alkaline solution.25 In addition, owing to the co-contribution of Ni2+/Ni3+ and MnO2/MnOOK couples, Ni(OH)2/MnO2 binary system offers richer redox reactions than either of the single ones, similar as that in Ni-Co LDH.18,26,27 Therefore, it is reasonable to deduce that Ni(OH)2/MnO2 composite would possess more excellent electrochemical performance than that of Ni(OH)2 and MnO2. Unfortunately, till now, only limited information is available for preparation of high performance Ni(OH)2/MnO2 composite. Besides the ingredient, the mass loading of electroactive material on current collector also has a huge effect on its supercapacitive performance. Generally, the electroactive materials can deliver excellent supercapacitive performance at low mass loading level (
