bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Performance Pseudocapacitors Based on Multicomponent Transition Metal Oxides By Local Distortion of Oxygen Octahedra
Authors: Lee Hyeon Jeong , Lee Ji Hoon , Choi Jang Wook 
Published: February 2020

As pseudo-capacitors store the charge based on the dual (‘faradaic’ and ‘capacitive’) modes, they have the advantages of both ultracapacitors and rechargeable batteries.[1] One of the main directions in pseudo-capacitor research in the past decade has been the integration of nanostructured metal oxides, hydroxides, and chalcogenides with conductive carbon nanomaterials,[2] such as graphene and carbon nanotubes. Nanostructures bring the benefits of high rate capability as well as long cycle life related to the improved mechanical stability of active phases, as nanomaterials are better at releasing the strains. The nanostructure effect of metal oxides was verified for a variety of morphologies with diverse transition metals.[3]Nonetheless, a majority of studies have focused solely on the nanostructure effects, and the impact of the TM choice or mixing of multiple TMs on the electrochemical performance has not been examined in depth.
Here, we have systematically investigated the impact of multiple TMs, particularly those commonly adopted as pseudo-capacitor active materials: Ni, Co, and Mn. Interestingly, when the three TMs are mixed in equal amounts, the specific capacitance rises far beyond those of their individual cases, indicating a synergistic effect from the TM mixing. A combined experimental and theoretical analysis reveals that the enhanced performance originates from permanent local distortions of [NiO6] octahedra in the presence of aliovalent cations (Co3+ and Mn4+) and transition metal vacancies (V
M), among which V
M has the largest effect on distorting the nearest neighboring [NiO6] octahedra. The degenerate eg
level in Ni2+, the primary redox center for capacitance acquisition, is split via this permanent distortion, thus enabling the energetically more facile redox swing of Ni2+/3+by alleviating the structural variation from a Jahn-Teller effect.
This study introduces a new opportunity to improve the electrochemical performance of pseudo-capacitors through the mixing of multiple TM cations. The solid solution mixing of multiple TMs pre-distorts the framework and consequently mitigates Jahn–Teller-type structural variation during the redox reaction, resulting in the significantly wider redox swing of Ni and the larger pseudo-capacitance of the solid solutions. The findings of this study demonstrate the importance of structure-property relation in designing and improving key active materials in emerging energy storage systems.

References

[1] Simon, P., Gogotsi, Y., Nat. Mater.
2008,
7, 845-854.
[2] Yu, G., Hu, L., Liu, N., Wang, H., Vosgueritchian, M., Yang, Y., Cui, Y., Bao, Z., Nano Lett.
2011,
11, 4438-4442
[3] Lu, Q., Chen, J. G. G., Xiao, J. Q., Angew. Chem. Int. Ed.
2013,
52, 1882-1889
Flexible and Weaveable Wire-Shaped Capacitor with Ultra-High Energy Density
Authors: Cheng Jianli , Wang Bin 
Published: February 2020

Wearable electronics and microelectronics have been shown to be highly desired in the current and further life. To power these wearable electronic systems, flexible energy storage devices are needed. Comparing with the conventional planar device architectures, one-dimensional fiber micro-supercapacitors (FSCs) with the merits of lightweight, tiny volume, high flexibility and weavability which can be directly used as wearable components are more attractive. However, compared with batteries or traditional capacitors, FSCs show much lower-energy density and suffer from extra challenges in mechanical performance. According to the equation (E = 0.5CU2), energy is proportional to capacitance. So it is crucial to explore high capacitance fibers with good mechanical properties for FSCs.
Electric-double layer capacitors (EDLCs) store energy through the charge separation at the electrode/electrolyte interface. In our study, we try to increase the capacitance and energy density of EDLCs by increasing the fiber interfacial area. We adopt a simple pipe mold method to fabricate hollow RGO/PEDOT composite fibers and hollow pure RGO fibers (labeled as HCFs and HPFs) with excellent flexibility and conductivity. Furthermore, the hollow fibers show a dramatic charge-storage ability. The symmetric solid-state FSCs composed of two HCFs reveal a high specific areal capacitance of 304.5 mF cm-2 at 0.08 mA cm-2, corresponding to an ultra-high energy density of 6.8 µWh cm-2 at a power density of 16.6 µW cm-2. To the best of our knowledge, it is the highest record for FSCs to date.
In this presentation, we will discuss the fiber formation mechanism, charge storage mechanism and we will display the flexible wire-shaped energy device constructed by the one-dimensional fiber micro-supercapacitors.
(Invited) The Development of Pseudocapacitance in Oxide Materials
Authors: Dunn Bruce 
Published: February 2020

Battery materials exhibit high energy density by utilizing reversible redox reactions, but their slow ionic diffusion leads to long charging times. Electrochemical double layer capacitors (ELDCs) offer some advantages over batteries, including fast charging times (<1 minute) and long lifetimes (<500,000 cycles). However, ELDCs do not involve redox reactions and as a result they have lower energy densities compared to batteries. For this reason, there is widespread interest in pseudocapacitance, a faradaic process involving surface or near-surface redox reactions, that can lead to high energy density at high charge-discharge rates. In recent work, we have suggested that pseudocapacitive materials can be classified as extrinsic or intrinsic; in the latter case, pseudocapacitive behavior is dependent on particle size, as fundamental changes in redox reactions may occur in finite sized systems. This paper will review our work on identifying Li+ conducting materials which exhibit pseudocapacitive behavior. Our research on Li+ insertion in Nb2O5 has established a basis for intercalation pseudocapacitance in which the rate of charge storage is determined by surface-like kinetics rather than semi-infinite diffusion as occurs with battery materials. Another key feature with this mechanism is that the structure does not undergo a phase transformation upon Li+ insertion. However, even with materials that exhibit phase transitions, such as MoO2, pseudocapacitive properties may be observed provided that the materials are reduced to nanoscale dimensions. In this case pseudocapacitive characteristics arise because phase transitions which occur in the corresponding bulk material are effectively suppressed. Our research with nanoscale MoO2 shows that pseudocapacitive properties are developed and that the material operates at high charge-discharge rates with only a small decrease in the level of charge storage. In contrast, micron-sized particles exhibit a significant decrease in charge storage at high charge-discharge rates. These results underscore our improved understanding of the electrochemical and structural characteristics that lead to materials that exhibit both high energy density and high power density.
Ba0.5Sr0.5CoxFe1-XO3-d As High Volumetric Capacitance Pseudocapacitive Electrode Materials
Authors: Lannelongue Pierre , Brousse Thierry , Crosnier Olivier , Favier Frederic 
Published: February 2020

The design and fabrication of high volumetric energy density supercapacitors lead to high density pseudocapacitive materials to be considered as electrode material. After our previous, and still on-going, work on FeWO4 [1], Ba0.5Sr0.5CoxFe1-xO3-
δ phases, with 0.75<x<0.85, so-called BSCF, are currently under investigation. Our motivation towards these materials are (i) on the sub-stoechiometry in oxygen suggesting a flexible balance of either Fe and Co redox centers as well as (ii) on their attractive intrinsic electronic conductivity. These phases have been prepared by various synthetic methods, including Pechini and flash combustion syntheses, at various temperatures ranging from 850 to 950 °C. Despite the eventual presence of small amount of CoO and BaO impurities (depending on the synthesis type and temperature), resulting materials show the same perovskite structural arrangement and similar morphological characteristics.
The electrochemical performances have been evaluated by cyclic voltamperometry at room temperature, at various scan rates from 5 to 200 mV.s-1 and in various aqueous electrolytes: KOH 0.5 M, H2SO4 0.5 M, K2SO4 0.5 M, Na2SO4 0.5 M, Li2SO4 0.5 M, and LiNO3 0.5, 1.0 and 5 M. The potential window was shown to vary depending on the electrolyte nature but, most of the time, prepared BSCFs showed promising pseudocapacitive behaviors as electrode material. A specific capacitance of 64 F.g-1 was measured at 5 mV.s-1 in LiNO3 5M for the electrode based on the material prepared by flash combustion at 850°C. This value corresponds to a volumetric capacitance of 377 F.cm-3. The electrode also exhibited fair capacitance retention over 2000 cycles.
The electrochemical performances were shown to vary depending on the Co/Fe ratio and are discussed toward the involved charge storage mechanism.

Reference

[1] N. Goubard-Bretesché, O. Crosnier, C. Payen, F. Favier, T. Brousse, Electrochem. Com. 57, 61–64, 2015
Understanding Pseudocapacitive Charge Storage in Transition Metal Oxides from Fundamental Interfacial Processes to 3D Electrode Design
Authors: Long Jeffrey W. , Sassin Megan B. , Chervin Christopher N. , Parker Joseph F. , Wallace Jean Marie , Rolison Debra R. 
Published: February 2020

Transition-metal oxides that exhibit “pseudocapacitance” are promising alternatives to high-surface-area carbons as charge-storing materials in next-generation electrochemical capacitors (ECs). Hydrous ruthenium oxides remain the state-of-the-art for pseudocapacitive materials due to their fortuitous combination of high electronic and ionic conductivity. Lower-cost alternatives are being vigorously pursued, yet the low electronic conductivity of most other metal oxides of interest (e.g., MnOx) necessitates that they be thoughtfully incorporated with a conductive carbon support. We have developed an electrode design in which pseudocapacitive oxides, such as MnOx and FeOx, are applied as nanoscale coatings onto ultraporous carbon nanofoam substrates that define the macroscale-to-nanoscale structure of the resulting electrode architecture [1,2]. In addition to their practical advantages for device fabrication, these nanofoam paper-based materials have also provided a designer platform with which to investigate the interplay of pore structure and electrochemical performance [3] and for in situ analysis of the mechanisms responsible for pseudocapacitance [4].
In the background of these studies, we have accumulated evidence that the physicochemical nature of the carbon–metal oxide interface can have a significant impact on electrochemical performance. While continuing to develop and transition our 3D electrode architectures, we are refocusing our research efforts on investigating fundamental charge-transfer properties at nanoscale carbon–metal oxide interfaces. Shifting from the characterization complexities of the nanofoam-based architectures, we use planar pyrolytic-carbon substrates to mimic the surface properties of 3D carbon, but in forms that are more readily characterized by conventional surface spectroscopy and scanning-probe microcopy techniques. We apply nanoscale pseuodocapacitive oxides to these planar carbon films using redox-deposition protocols previously demonstrated at 3D carbons [5], and explore how the physical, chemical, and electronic structure of the resulting carbon–metal oxide interface impacts electrochemical properties. Lessons learned from these model interfaces are readily translated to improved performance in practical 3D electrode architectures.
1. Fischer, A.E.; Saunders, M.P.; Pettigrew, K.A.; Rolison, D.R.; Long, J.W. J. Electrochem. Soc. 2008, 155, A246.

2. Sassin, M.B.; Mansour, A.N.; Pettigrew, K.A.; Rolison, D.R.; Long, J.W. ACS Nano
2009, 4, 4505.

3. Sassin, M.B.; Hoag, C.P.; Willis, B.T.; Kucko, N.W.; Rolison, D.R.; Long, J.W. Nanoscale, 2013, 5, 1649.

4. Beasley, C.A.; Sassin, M.B.; Long, J.W. J. Electrochem. Soc.
2015, 162, A5060.

5. Sassin, M.B. Chervin, C.N.; Rolison, D.R.; Long, J.W. Acc. Chem. Res.
2013, 46, 1062.
Ionic Liquid Mxene-Based Pseudocapacitors
Authors: Alhabeb Mohamed , Van Aken Katherine L , Anasori Babak , Gogotsi Yury 
Published: February 2020

Pseudocapacitors are types of electrochemical capacitors in which energy is stored via surface redox reactions rather than ion adsorption mechanisms as in electric double layer capacitors. Among two dimensional (2D) materials, MXenes are a newly discovered family of transitional metal carbides and/or carbonitrides with ≈ 20 synthesized members and over 30 members predicted to exist, making it not only the fastest growing but potentially the largest family ever known 2D materials[1-3]. In contrast to other well known 2D materials, the unique combination of a metal carbide and surface termination groups of MXenes make them exceptionally hydrophilic and highly conductive. Titanium carbide MXene (Ti3C2), in particular, has shown outstanding capacitive performance in aqueous electrolytes due to its superior metallic conductivity[4, 5].
Here, we pre-intercalated Ti3C2 binder free electrodes with ionic liquids (ILs) to enhance the interlayer spacing of the electrode material, which shows excellent capacitive performance up to 200 F/g and energy density of 100 W.h/kg. We also report on using two of the newly discovered molybdenum and chromium containing MXenes, Mo2TiC2, and Cr2TiC2 free-standing films as pseudocapacitor electrodes in ILs electrolytes. The use of ILs enables us to increase the operating voltage window of MXene based electrodes and results in high energy density in comparison to aqueous electrolytes. This study opens new window for MXene based electrodes in applications that requires high energy density.

References:

1. Naguib, M., et al., Two
‐
Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2. Advanced Materials, 2011. 23(37): p. 4248-4253.
2. Anasori, B., et al., Two-Dimensional, Ordered, Double Transition Metals Carbides (MXenes). ACS Nano, 2015.
3. Naguib, M. and Y. Gogotsi, Synthesis of two-dimensional materials by selective extraction. Acc Chem Res, 2015. 48(1): p. 128-35.
4. Lukatskaya, M.R., et al., Cation intercalation and high volumetric capacitance of two-dimensional titanium carbide. Science, 2013. 341(6153): p. 1502-5.
5. Ghidiu, M., et al., Conductive two-dimensional titanium carbide/clay/'with high volumetric capacitance. Nature, 2014. 516(7529): p. 78-81.
Activation of Petroleum Pitch for Production of Porous Carbons with High Electric Double Layer Capacitance
Authors: Wu Pin-i , Teng Hsisheng 
Published: February 2020

Petroleum pitch can be an alternative of coal tar pitch as the precursor of activated carbon because of their lower contents of detrimental impurities and less pollution to the environment when compared with coal tar pitch. High-porosity carbon derived from activation of mesophase pitch with KOH has been successfully used as the electrode materials for electric double layer capacitors (EDLCs).1 Formation of mesophase structure through thermal treatment coordinates the pitch molecules and eventually reinforces the structure of porous carbons obtained from activation. The present study devises a temperature-programmed heating strategy to convert petroleum pitch to mesophase that has a framework advantageous for producing porous carbons suitable for EDLCs. The porous carbon is synthesized by KOH activation and has a Brunauer-Emmett-Teller surface area exceeding 3000 m2/g, When assembled in a symmetric two-electrode cell, the carbon delivers capacitance values of 170 and 102 F g-1 at current densities of 0.5 and 100 A g-1, respectively, in 1 M tetraethylammonium tetrafluoroborate/acetonitrile electrolyte. The energy density of the cell based on the total carbon mass reaches 23 Wh kg-
1 at a power density of 40 kW kg-
1. The results of the present study demonstrate the feasibility of using petroleum pitch as the precursor for porous carbon production and the significance of mesophase pitch structure for regulating the structure of pores suitable for charge storage.

References

1. H.C. Huang, C.J. Chung, C.T. Hsieh, P.L. Kuo, H. Teng, Nano Energy 21 (2016), 90

Acknowledgments: This research was supported by the Ministry of Science and Technology, Taiwan (104-2221-E-006-231-MY3, 104-2221-E-006-234-MY3, 105-3113-E-006-005, and 104-3113-E-006-011-CC2), and by the Ministry of Education, Taiwan, The Aim for the Top University Project to the National Cheng Kung University.
Fabrication and Enhanced Electrochemical Properties of Bi3.64Mo0.36O6.55 Nanoparticles with a High Bi Content for Pseudocapacitor Electrodes
Authors: Liu Xiaoheng , Zhu Dan , Wang Weiwei 
Published: February 2020

The faradaic pseudocapacitors are emerging as an attractive energy-storage solution with much higher specific capacitance and energy density due to their reversible multielectron redox faradaic reactions.Herein, we reported that the monodisperse Bi3.64Mo0.36O6.55 nanoparticles could be used as a novel pseudocapacitor electrodes material. This nanoparticles could be successfully prepared by a facile hydrothermal method using sodium molybdate (Na2MoO4·2H2O) and bismuth nitrate (Bi(NO3)3·5H2O) as the Mo and Bi sources, respectively. The technologies of X-ray powder diﬀraction (XRD), X-ray photoelectron spectroscopy (XPS), ﬁeld emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electronic diﬀraction (SAED) were used to characterize the structure and morphology of Bi3.64Mo0.36O6.55 nanoparticles. The results show that the dimensions of the as-prepared Bi3.64Mo0.36O6.55 nanoparticles are 100-150 nm. The pseudocapacitive properties of products were investigated at the redox potential of -1.0-0 V vs. Hg/HgO in a 1 M aqueous KOH solution by cyclic voltammetry (CV), chronopotentiometry (CP) and AC impendence. The higher specific capacitance could be obtained as about 998 F/g compared with that of Bi2MoO6 (350 F/g) at 1 A/g, which is possibly ascribed to the nanoparticle structure and the exceeded Bi content of Bi3.64Mo0.36O6.55 nanoparticles. Furthermore, the Bi3.64Mo0.36O6.55 nanoparticles electrode exhibits a good cycle stability with more than 95% after 1000 cycles. These results demonstrated that the obtained high performance Bi3.64Mo0.36O6.55 nanoparticles could be a promising electrode material for pseudocapacitor.
A Combined Theoretical-Experimental Study of Energy Storage Behavior of Reduced Graphene Oxide/Manganese Oxide Supercapacitor
Authors: Lee Chan-Woo , Byun Segi , Yoo Jung-Joon 
Published: February 2020

Miniaturized electrochemical capacitors, such as micro-supercapacitors, have emerged as a new class of micro-power sources. However, they have limited uses in micro-energy storage because of their low volumetric energy densities. Here, compact structured Birnessite (MnO2)/reduced graphene oxide (RGO) hybrid films (Fig.1) consisting of multi-valent Mn ions were prepared via a two-step fabrication process involving a simple chemical redox reaction and post-thermal annealing to form a multi-layer structured film. With this versatile method, GO sheets can act as either a growth template for the highly capacitive MnO2 nanosheets or as a mechanical support for the production of compact hybrid films. Enhanced electrochemical characterization of the MnO2/RGO hybrid film revealed a remarkable ultrahigh volumetric capacitance (493 F/cm3 at 10 mV/s), ultrahigh energy and power density (13.3 mWh/cm3 at 2.5 A/cm3 and 22.6 W/cm3 at 58 A/cm3, respectively) and a semi-permanent cycle life (97% capacitance retention) in an aqueous electrolyte system.
We also elucidated operating mechanisms of MnO2/RGO capacitor using state-of-the-art density-functional theory calculations with MnO2 nanoparticle/RGO sheet models. Various materials properties of MnO2/RGO systems including stoichiometric deviation, defect energetics, electron transfer, and kinetic behavior of cations and their contributions to their capacitance have been explored in atomic level.

Figure 1
Nanotubes Via Vacuum-Supported Suction-System
Authors: Rastedt Maren , Hoogestraat Dirk 
Published: February 2020

Carbon nanotubes are versatile applicable. They can be used within measurement instrumentations (as tips for scanning tunneling microscopy), displays (as component for flat and luminous field emission screens) and for the enhancement of synthetic materials (improvement of their mechanical behavior). Furthermore, there are transistors and accumulators made out of carbon nanotubes (CNT).
Due to the versatility and the achievements of CNTs, it is also interesting to manufacture nanotubes and -fibers out of different materials. Martin Steinhart et al. succeeded to fabricate nanotubes and nanofibers out of various polymer materials by template wetting [1-3].
The template wetting is affected by the basic principles of surface coating/wetting and capillarity. The wetting emerges when low-energy liquids like polymer solutions or melts interact with porous substrates with high surface energies like aluminum oxide membranes (AAO) or macro-porous silicon.
After wetting of the membrane walls, the nanotubes or –fibers need to cure before removing the template with sodium hydroxide (when using AAO) or acid.
With help of the template wetting method, it is also possible to manufacture nanofibers and –tubes out of classical bulk-heterojunction solar cell materials (PCBM: Pheny-C61-butyric acid methyl ester and P3HT: Poly(3-hexylthiophene-2,5-diyl)). Therefore a device has been developed, which should be introduced in this paper (Figure 1a)).
With this element (Vacuum-supported Suction-System, VSS) [4], it is also possible to synthesize Core-Shell-nanotubes, it can be used with educt melts as well as educt solutions. Assemblies of well-defined, uniform and almost defect free nanotubes can be synthesized by this method. The VSS facilitates a simple fabrication of nanotubes filled with nanoparticles. Also PCBM/P3HT-Core-Shell-nanotubes are synthesized in this way (Figure 1 b) & c)) and are prepared and optimized for the application within Bulk-Heterojunction solar cells.

Figure 1:
a) Layout of vacuum-supported suction-system, VSS [4], b & c) TEM-images of Core (PCBM, red)-Shell-(P3HT, white)-nanotubes [4]

References:

1. M. Steinhart, J.H. Wendorff, A. Greiner, R.B. Wehrspohn, K. Nielsch, J. Schilling, J. Choi, U. Gösele, Science, 296 (2002).
2. M. Steinhart, J.H. Wendorff, R.B. Wehrspohn, ChemPhysChem, 4 (2003).
3. M. Steinhart et al., Angewandte Chemie International Edition, 43, 1334-1344 (2004)
4. M. Rastedt, „Design und Optimierung organischer Nanoröhrchen (für die potentielle Anwendung in kostengünstigen organischen Photovoltaik-Bauteilen)“, PhD Thesis, University of Oldenburg (2013)

Figure 1