ZnFe2O4@carbon core-shell nanoparticles encapsulated in reduced

life (98.3% of capacity retention after 700 cycles at 1 A g-1). ... approach to balance the high energy and high power.1-3 Generally, Li-HSC consists ...
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ZnFe2O4@carbon core-shell nanoparticles encapsulated in reduced graphene oxide for high-performance Li-ion hybrid supercapacitors Chongyang Yang, Minqiang Sun, Long Zhang, Peiying Liu, Peng Wang, and Hongbin Lu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b20305 • Publication Date (Web): 02 Apr 2019 Downloaded from http://pubs.acs.org on April 2, 2019

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ACS Applied Materials & Interfaces

ZnFe2O4@carbon core-shell nanoparticles encapsulated in reduced graphene oxide for high-performance Li-ion hybrid supercapacitors Chongyang Yang,†,‡ Minqiang Sun,† Long Zhang,† Peiying Liu,† Peng Wang,† Hongbin Lu*,†

†State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Collaborative Innovation Center of Polymers and Polymer Composites, Fudan University, 2005 Songhu Road, Shanghai 200438, China ‡National Engineering Research Center for Supercapacitor for Vechicles, Shanghai Aowei Technology Development Co., Ltd., Shanghai 201203, China

Abstract: Li-ion hybrid supercapacitors (Li-HSCs) are attracting extensive attention because of the high energy/power densities. However, the performance of most Li-HSCs suffers from the limitation from sluggish kinetics of battery-type anodes. Herein, we demonstrate that with dual protection of carbon and graphene, the three-dimensional, strongly coupled ZnFe2O4@C/RGO composite anode provides an effective solution to this issue. The covalent C-O-M linkage between ZnFe2O4 nanoparticles and C/RGO promotes the charge transfer and enhances structural stability. Two kinds of carbon-based buffering layers are able to well accommodate the volume change during charging/discharging, endowing the composite anode with high rate performance (692 mAh g-1 at 5 A g-1) and outstanding cycle life (98.3% of capacity retention after 700 cycles at 1 A g-1). The resulting ZnFe2O4@C/RGO// activated carbon (AC) Li-HSC shows an ultrahigh energy density of 174 Wh kg-1, excellent power density of 51.4 kW kg-1 (at 109 Wh kg-1) and cycle life (80.5% retention of capacity after 10000 cycles at 5 A g-1).

KEYWORDS: ZnFe2O4, carbon shell, graphene, anode, Li-ion hybrid supercapacitor 1

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1. Introduction Nowadays, energy-storage devices with both high energy/power densities and long cycle life are urgently desired owing to the ever-increasing portable electronics, smart electric grids and electric vehicles (EVs). By integrating the advantages of Li-ion batteries (LIBs) and supercapacitors (SCs), Li-ion hybrid supercapacitors (Li-HSCs) have become an effective approach to balance the high energy and high power.1-3 Generally, Li-HSC consists of a battery-type anode that affords high capacity and a capacitor-type cathode that achieves fast charge-discharge,

implying

that

two

different

energy

storage

mechanisms

work

simultaneously in this hybrid system.4-6 Despite considerable effort in recent years,7-11 the high energy densities (50-200 Wh kg-1) achieved in the majority of the reported results are usually sacrificing power densities (