Hierarchical Ni0.54Co0.46O2 nanowire and nanosheet arrays grown on carbon fiber cloth for high-performance supercapacitors
Introduction
Energy is one of the most important topics that attracting more and more attention of the whole world in the 21st century. To meet the urgent requirements of renewable and sustainable energy sources, there is a growing demand for developing cleaner and more efficient energy storage systems such as supercapacitors and lithium-ion batteries [1]. Supercapacitor is regarded as one of the most promising avenue to the future for its relatively higher power density, faster charge/discharge capability and longer cycling life [1], [2], [3].
However, the realization of that strategic conception depends on many aspects particularly a breakthrough in obtaining higher energy meanwhile keeping power delivery and cycling stability [4]. One promising approach is to introduce a battery-type faradaic electrode into hybrid electrochemical capacitors [2]. Transition metal oxides as battery-type materials used in capacitors explored relatively higher performance than EDLCs due to their rich redox reactions on the surfaces as well as in the bulk of the electrode [5], [6], [7], [8], [9], [10]. At present, a series of transition metal oxides electrode materials, such as MnO2 [11], [12], NiO [13], [14], [15] and Co3O4 [16], have been researched. However, the applications of these materials are mainly restricted by various aspects as low energy capacity and poor cycle life [17]. NiCo2O4 with spinel structure sparked worldwide interest as an attractive battery-type faradaic electrode for advanced capacitor devices for the presence of Ni2+/Ni3+ and Co2+/Co3+ redox couples in the spinel structure [18], [19], [20]. What is remarkable is that the addition of Co can largely reduce the specific capacity though effectively improve the cycling life and the conductivity of the NiCo oxides [21]. Significantly, according to some researches, the specific capacity is found to be relied on the molar ratio of Co/Ni, getting highest at Co/Ni molar ratio of close to 1 when forming the NaCl-type NiCoO2 [22], [23]. NiCoO2 has also been used in many other fields such as water oxidation [24] as well as Li-ion batteries [25] and both of them exhibit excellent performance confirming NiCoO2 has enormous potential in the application of electrochemical reactions.
In recent researches, there were two main nanostructures have raised a widely attention called nanorods/nanowires and nanosheets synthesized by hydro-/solvo-thermal method [26], [27]. There were some reports demonstrated that the electrochemical performances such as ion transfer rates and electrode/electrolyte interface properties are strongly influenced by the morphologies and microstructures of electrode materials [28]. In addition, it is well known that defects in materials can improve the performance of supercapacitors, because crystalline imperfection can provide additionally electrochemical active sites. Thus, it is very significate and prospective to study the difference between the different shapes of NiCoO2 with abundant lattice imperfection and its electrochemical properties, which were few researches on before.
Traditionally, when discrete particles are used as electrode materials for supercapacitors, electrodes have to be fabricated with a lot of insulating polymer binder and conductive agents, which can largely affect the capacity performance, portability, price and practicability of supercapacitors. Carbon fiber supported electroactive nanocomposites seems to be a promising plan, with the unprecedented superiority of excellent flexibility, lightweight as well as corrosion resistance. However, most of the as-prepared carbon fibers used for electrode materials are carbon nanotubes, graphene and commercial carbon fiber [29], [30], [31]. Given their complex preparation, cost and abundance, the bio-mass carbon derived from bio-base resources such as hemp [8], flax [11] and cotton [32] has attracted intense interest lately and is widely used in SCs. As far as we know, the previous study of NiCoO2 used as electrodes for supercapacitors had to be blended with binders and affect the performance seriously due to the lower conductivity than NiCo2O4, so it is urgent need to develop an effective binder-free method to achieve the best performance of NiCoO2 [32].
In this work, we successfully synthesized controllable morphology of hybrid nanostructures composed of Ni0.54Co0.46O2 nanowire and nanosheet arrays grown on bio-mass carbon fiber cloth (CFC) through a facile hydrothermal method. A large number of lattice defects and crystalline imperfection were obtained in both morphologies which could boost the chemical performance of supercapacitors effectively and thus form non-stoichiometry Ni0.54Co0.46O2, denoted as NCO-NWs/CFC and NCO-NSs/CFC, respectively. Urchin-like and flower-like Ni0.54Co0.46O2 were prepared by the same method without supporting on the CFC, denoted as NCO-NWs and NCO-NSs separately. As expected, two different nanostructures loaded on CFC directly as binder-free for SCs exhibit high Faradaic capacity. In comparison, NCO-NSs/CFC as a hybrid battery-type electrode exhibit a higher capacity (438.6 μAh cm−2 at a current density of 1 mA cm−2), better rate capability (387.0 μAh cm−2 at 50 mA cm−2) and capacity retention (∼70% after 10000 cycles at 10 mA cm−2) than NCO-NWs/CFC. Moreover, a symmetric supercapacitor device composed of as-prepared NCO-NSs/CFC electrodes has been successfully assembled. The excellent device delivers an outstanding energy density of 92.4 Wh kg−1 at a power density of 207.2 W kg−1.
Section snippets
Preparation of carbon fiber cloth (CFC) derived from cotton textile
Cotton textile cloth was purchased from a cloth market and cut into strips with the size of 6 × 40 cm2 without drying and other treatments before carbonization. The carbonization process was carried out by the temperature control program depicted in Fig. S1.
Synthesis of Ni0.54Co0.46O2 NWs/CFC, Ni0.54Co0.46O2 NSs/CFC, Ni0.54Co0.46O2 NWs and Ni0.54Co0.46O2 NSs
All the reagents used in the experiments were analytical grade and without further purification. In a typical experiment, carbon fiber cloth was cleaned in 5 M HCl aqueous solution, acetone, deionized (DI) water and absolute ethanol under
Structural characterization
XPS is implemented to determine the detailed oxidation state information and element composition on the surface of Ni0.54Co0.46O2 nanosheet arrays structure scraped from as-prepared NCO-NSs/CFC. Co, Ni, O, and C element can be observed obviously in the full spectrum (Fig. 1a) and the atomic ratio of Ni and Co is calculated to be 1.18: 1 which is consistent with the result of ICP test (1.16: 1). In Ni 2p spectra (Fig. 1b), the Ni 2p spectrum can be fitted as two spin-orbit doublets and two
Conclusions
In summary, two kinds of hierarchical nanostructure composed by Ni0.54Co0.46O2 nanosheet and nanowire arrays directly grown on cotton textile-derived carbon fiber cloth have been synthesized by a facile and high-efficiency hydrothermal method. We compared the electrochemical performance of the two morphologies and found that the NCO-NSs/CFC exhibits higher capacity (425.4 μAh cm−2 at the current density of 1 mA cm−2) as well as much better cycling stability (loss of ∼30% after 10000 cycles)
Acknowledgment
These authors are grateful to the financial supported from National Natural Science Foundation of China (NNSFC 21003077) and Tianjin Natural Science Foundation, China (No. 14JCZDJC32000) and MOE (IRT13R30).
References (54)
- et al.
Application of biomass-derived flexible carbon cloth coated with MnO2 nanosheets in supercapacitors
J. Power Sources
(2015) - et al.
Ultrathin NiO nanosheets anchored on a highly ordered nanostructured carbon as an enhanced anode material for lithium ion batteries
Nano Energy
(2015) - et al.
NiCoO2 nanowires grown on carbon fiber paper for highly efficient water oxidation
Electrochim. Acta
(2015) - et al.
Cycle versus voltage hold - which is the better stability test for electrochemical double layer capacitors?
J. Power Sources
(2013) - et al.
The facile synthesis of hierarchical NiCoO2 nanotubes comprised ultrathin nanosheets for supercapacitors
J. Power Sources
(2014) - et al.
Controllable synthesis of Co3O4/polyethyleneimine-carbon nanotubes nanocomposites for CO and NH3 gas sensing at room temperature
J. Alloys Compd.
(2015) - et al.
Nickel cobaltite as an emerging material for supercapacitors: an overview
Nano Energy
(2015) - et al.
The state of the oxygen at the surface of polycrystalline cobalt oxide
J. Electron Spectrosc.
(1995) - et al.
Characterization of the nickel cobaltite, NiCo2O4, prepared by several methods: an XRD, XANES, EXAFS, and XPS Study
J. Solid State Chem.
(2000) - et al.
Improved electrochemical performances of binder-free CoMoO4 nanoplate arrays@Ni foam electrode using redox additive electrolyte
J. Power Sources
(2016)
Flexible all-solid-state hierarchical NiCo2O4/porous graphene paper asymmetric supercapacitors with an exceptional combination of electrochemical properties
Nano Energy
Fabrication of natural polymer assisted mesoporous Co3O4/carbon composites for supercapacitors
Electrochim. Acta
Hierarchical porous nickel oxide and carbon as electrode materials for asymmetric supercapacitor
J. Power Sources
Green synthesis of graphene nanosheets/ZnO composites and electrochemical properties
J. Solid State Chem.
Advanced materials for energy storage
Adv. Mater.
Materials for electrochemical capacitors
Nat. Mater.
Materials science: electrochemical capacitors for energy management
Science
High rate capabilities of NiCo2O4-based hierarchical superstructures for rechargeable charge storage
J. Electrochem. Soc.
Electrochemical Supercapacitors: Scientific Fundamentals and Technology Applications
To be or not to be pseudocapacitive?
J. Electrochem. Soc.
MnO2-based nanostructures for high-performance supercapacitors
J. Mater. Chem. A
A flexible fiber-shaped supercapacitor utilizing hierarchical NiCo2O4@polypyrrole core–shell nanowires on hemp-derived carbon
J. Mater. Chem. A
A new type of porous graphite foams and their integrated composites with oxide/polymer core/shell nanowires for supercapacitors: structural design, fabrication, and full supercapacitor demonstrations
Nano Lett.
Electrochemical formation mechanism for the controlled synthesis of heterogeneous MnO2/Poly(3,4-ethylenedioxythiophene) nanowires
ACS Nano
Sandwich-structured nanohybrid paper based on controllable growth of nanostructured MnO2 on ionic liquid functionalized graphene paper as a flexible supercapacitor electrode
Nanoscale
Scalable synthesis of urchin- and flowerlike hierarchical NiO microspheres and their electrochemical property for lithium storage
ACS Appl. Mater. Interfaces
Nanoscale morphology dependent pseudocapacitance of NiO: influence of intercalating anions during synthesis
Nanoscale
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