bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating the Electrochemical Behaviour of Different Carbons in Non-Aqueous Solvents Using Step Potential Electrochemical Spectroscopy
Authors: Donne Scott W , Dupont Madeleine F , Roland Aude 
Published: February 2020

Supercapacitors are high-capacity electrochemical capacitors that bridge the gap between electrolytic capacitors and rechargeable batteries. They are a promising energy storage technology for addressing many of the problems associated with the transition to renewable energy technologies from fossil fuel based energy. Supercapacitors use electrostatic double-layer capacitance or electrochemical pseudocapacitance but in reality it’s often a combination of both. The common electrochemical methods used to characterize supercapacitor electrode materials are not able to separate the contribution from these different phenomena. However, using the step potential electrochemical spectroscopy (SPECS) method we will be able to develop a model of specific capacitance behaviour in link with the porosity and the morphology of the active material used for the synthesis of the electrode.
The SPECS experiment involves applying a small (±25 mV) potential step to the working electrode followed by a long equilibration time (300 s). This process is repeated over and entire charge-discharge cycle. By scanning at such a slow rate, the electrode has time to equilibrate at each potential, and the maximum charge storage capabilities of the electrode can be accessed. Each of the different charge storage processes occurring at the electrode has a unique time- dependent current response, and hence each potential step profile can be fitted to a model describing each of these processes. From this, values for series resistance (RS), double layer capacitance (CDL), diffusion limited capacitance (CD) and residual capacitance (CR) can be extracted. When the potential is stepped over an entire capacitor cycling range, contributions from each process can be determined at each point in the cycle.
In this work, nine different kinds of carbon structures were studied with the SPEC method and the results had shown how it was possible to link the carbon structure and the morphology with the storage behaviour. The morphology of these materials were very different and consequently the specific area and the diffusion of the electrolyte inside were impacted.
The effects of different non-aqueous electrolytes were also studied under the same conditions to understand how the performances are affected by the ion size variation in order to have a better idea of the storage mechanism at the interface.
High Energy-Density Hybrid Supercapacitors: Combining High-Voltage Window Ionic Liquids with MnO2-Nanomaterials
Authors: Lindberg Simon , Nitze Florian , Matic Aleksandar 
Published: February 2020

Hybrid supercapacitors, utilizing faradaic as well as electrochemical reactions for energy storage, have attracted considerable attention during the last years as the need for fast charging and reliable energy storage is ever increasing in today’s society. However, issues still remain that prevents utilizing the full potential of hybrid supercapacitors. The highest hurdle is that the energy density (gravimetric and volumetric) of hybrid supercapacitors is still too low compared to batteries[1]. Additionally, hybrid supercapacitors suffer from poor cycle lifetime, compared to traditional supercapacitors.
A promising approach to increase the energy density of hybrid supercapacitors is the use of electrolytes, which are stable in a larger potential window compared to aqueous electrolytes. This enables higher total operating voltages, which is especially important, since the energy density has a quadratic dependency on the voltage.
However, so far hybrid supercapacitors, using MnO2 or RuO2 as electrochemically active component, have mostly been designed using aqueous electrolytes[1], thereby missing the possibility to benefit from the higher operating voltage of non-aqueous electrolytes. In our work, we aim at increasing both the operating voltage and the capacitance of hybrid supercapacitors, which together would enable higher energy density.
We investigate how different solvents, mainly based on ionic liquids interact with carbon based electrodes containing MnO2 nanoparticles[2] as electrochemically active species. We reveal how different proton characteristics (protic and aprotic) of the ionic liquids influence the performance. For instance, we compare the performance of the protic ionic liquid 1-ethylimidazolium bis(trifluoromethanesulfonyl) (EI-TFSI) and the aprotic 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) (EMI-TFSI). To further investigate the role of protons and to increase their availability, we add different additives, such as water to the ionic liquid electrolytes. We discuss the fundamental mechanisms, i.e. the role of protons, the role of additional cations, and the influence of the voltage window on the performance of the system (capacitance, energy density, and stability).
Our study provides insight that can help to achieve a better understanding of the requirements on the electrolyte for hybrid supercapacitors. It shows that the MnO2 nanomaterial requires protons to work efficiently. Using protic electrolytes, such as water and EI-TFSI, a contribution from MnO2 can be observed, whereas there is no additional electrochemical contribution in the aprotic electrolyte. However, by adding water, and thereby available protons, to the aprotic ionic liquid we are able to increase the proton concentration and activity of the MnO2 material.

[1]Chem. Soc. Rev., 2015, 44, 7484—7539

[2]J. Phys. Chem. C 2011, 115, 5413–5421
Preparation of Sioc Li-Ion Capacitor By TEOS Based Sol-Gel Method with Different Silicones Precursors
Authors: Li Bochen , Funahashi Chikara , Saito Takeyasu , Okamoto Naoki , Ide Isamu , Onishi Yoshikazu , Nishikawa Masanobu 
Published: February 2020

Since the development of Li ion battery, carbonous materials e.g. graphite had been widely used in commercial lithium-ion batteries. However, the practical capacity of graphite reached an almost theoretical limit. Therefore, promising anode materials, such as Sn, Si etc. have been considered to replace the graphite though they are not stable during charge-discharge cycles. It was recently reported that amorphous SiOC anode performs high capacity and superior cycling durability. SiOC material has high chemical stability and mechanical strength. In this study, we used a TEOS based sol-gel method with different silicones precursorsto synthesize SiOC directly on the Cu foil as a simple and cheap way.
The silicones used in this study were PDMS(dimethylpolysiloxane), silanol- terminated PDMS, Cyclotetrasiloxane, polyether-modified silicone, alkyl-modified silicone and phenol-modified silicone. They were mixed respectively with TEOS (Tetraethyl orthosilicate), which was considered to perform a sol-gel reaction, and water in ethanol. The mole ratio of the TEOS/ silicone / H2O was 1:1:4, and the volume ratio of the mixture and ethanol was 1:1. 10 μl of HCl(37wt%) was added as catalyst before stirring. The sol solution was spin-coated onto the Cu foil. We evaluated these kinds of anode by battery charge-discharge test. Pore distribution and composition was measured by small angle X-ray scattering (SAXS) and X-ray photoelectron spectrometry, respectively.
Amorphous SiOC thin films with all precursors showed a high cycling durability. The SiOC film from PDMS sol solution which was heated to 50ºC for 30 minutes during stirring achieved a best specific discharge capacity of about 1050 mAh/g even after 100 cycles, others are distributed from 150-400mAh/g. The SAXS of this sample shows a stronger peak of micropores(pore size <6 nm)than other samples. As a contest, we repeated the experiment without TEOS, and it became pyrolysis of silicones. The anodes made during the contest experiment showed low cycling durability but higher average specific capacity.
The Role of Superficial Graphene in Electroforming Process
Authors: Ryo Hokyun , Bae Sukang , Kim Tae-Wook , Ha Jun-Seok , Lee Sang Hyun 
Published: February 2020

Electroforming is a specialized process in electrochemical fabrication of metal parts. Electroplating is typically concerned with coating a metallic layer to provide some functionality and/or protect the surface of article. On the other hands, the electroforming purposes on the metallic structures which are created on a cathode mandrel or template by electroplating process.[1] Precision manufacturing including three-dimensional structures and microstructures is possible by a high degree of control in electroforming. One of the most important steps in the electroforming process is the separation of a fabricated deposit from the template without deformation or damage, which strongly depends on the interfacial properties between the deposit and template.
Graphene composed of a layer of sp2-bonded carbon atoms has a high electrical conductivity and a low surface energy due to a lack of dangling bonds on the surface.[2] In this study, we demonstrated that graphene layer is a good superficial layer for electroforming process. Mono-layered or multi-layered graphene were synthesized on Cu or Ni foils using chemical vapor deposition (CVD). The graphene was fully covered the surface of metal foils which used templates for electroforming. During electrochemical deposition, the graphene completely prevented strong bonding between the metal ions in electrolyte and metal atoms on the foils. The adhesion between an electroplated metal and graphene is much less than that between graphene and the metal foil that was used for CVD. The difference in adhesive force enables effective delamination of the deposited metal. The surface morphology of the deposited metal layer was similar to the graphene/metal foil template. In addition, we also confirmed that the technique could be utilized to fabricate various microstructures as well as flexible electronics.
[1] J. A. MacGeough, M. C. Leu, K. P. Rajurkar, A. K. M. De Silva and Q. Liu, CIRP Ann.-Manuf. Technol., 2001, 50, 499–514.
[2] J. Rafiee, X. Mi, H. Gullapalli, A. V. Thomas, F. Yavari, Y. F. Shi, P. M. Ajayan and N. A. Koratkar, Nat. Mater., 2012, 11, 217–222.
Influences of Inert Particles on Corrosion Behavior of Carbon Steel Under Sodium Chloride Droplet
Authors: Wang Yanhua , Zhong Lian 
Published: February 2020

In ambient atmosphere, the surface of structural materials are usually covered by a layer of solid matter, containing soluble species and inert particles. The soluble species are highly hygroscopic and corrosive to steel, the inert particles can also affect corrosion by changing the mass transfer process. In this paper, the influence of inert particles on the droplet corrosion of carbon steel was studied by using the array electrode technique, potentiodynamic polarization technique and the electrochemical impedance spectroscopy. The current map exhibited the typical Evans distributions, with the anodes at the centre and the cathodes at the peripheral, which was not affected by the deposition of the inert particles. However, the spreadability of droplets increased with the increase of the amount of inert particles, which resulted in the expansion of corrosion activity area. In addition, the impedance spectra showed two capacitive loops with the deposition of inert particles, and the capacitive loop in the high frequencies was attributed to the blocking effect of the inert particles. The corrosion behavior of carbon steel was affected by these two aspects, the spreadability of droplets and the blocking effect of the inert particles. With the increase of the amount of particles, the average current value decreased firstly and then increased. There was a critical value in the deposition amount of the inert particles. When the amount was lower than the critical value, it could hinder corrosion. While, when the amount was higher than the critical value, it would accelerate corrosion owing to the expansion of droplets. The underlying mechanism was analyzed and a model was proposed.

Figure 1
The Contribution of Hydrogen to the Loss of Mechanical Properties of a 7046 Aluminium Alloy Pre-Exposed in a Chloride Media
Authors: Oger Loïc , Blanc Christine , Peguet Lionel , Odemer Gregory , Andrieu Eric 
Published: February 2020

Automotive industry is increasingly affected by standards requiring a major cut of polluting emissions. Rolled sheets of Cu-free 7000-series alloys offer a very attractive compromise between mechanical properties, corrosion resistance, forming and weight. With the continuing need for further down-gauging and light-weighting in transportation sector, as well as other applications, these alloys are being considered for large volume use. Nevertheless, their susceptibility to hydrogen embrittlement (HE) and to stress corrosion cracking (SCC) is a limiting factor. The present work concerns HE susceptibility of a 7046-T4 aluminium alloy exposed to a 0.6M NaCl solution. First results showed a strong decrease of the ultimate elongation for tensile samples after exposure to the chloride solution Surface observations revealed that the alloy was mildly affected by corrosion in this environment: pits initiated rapidly around intermetallic particles but only few pits propagated after several days of exposure. Cross-section of pre-corroded samples showed no intergranular corrosion and the maximal depth for the corrosion defects was about 100 nm which was not enough to lead to a noticeable loss of mechanical properties. Therefore, it was assumed that the decrease of the mechanical properties was related to the penetration of hydrogen inside the materials and the results gave proofs that hydrogen could enter and embrittle the 7046 aluminium alloy even without an applied stress during its exposure to the corrosive solution. Global hydrogen content measurements by melting method confirmed this assertion. Furthermore, comparison of the fracture surface of a healthy specimen and that of a sample pre-exposed to the NaCl solution showed that the ductile fracture mode observed for a healthy specimen was partially replaced by cleavage and brittle intergranular rupture when the sample was pre-corroded. Both fracture modes could be attributed to different hydrogen contents and different trapping sites in the microstructure. The hydrogen localized in the grain boundaries was believed to lead to intergranular decohesion, while the reticular and trapped hydrogen presumably induced cleavage rupture by exacerbating the localization of the plasticity. In addition, tensile tests were performed on samples pre-hydrogenated in a pH 2 sulfuric acid solution with a cathodic potential applied. The aim was to precisely control the hydrogen amount introduced in the samples. The depth and the nature of the fracture mode were then analyzed and related to the hydrogen amount. In parallel, pre-hydrogenated coupons were analyzed by SIMS in order to measure the maximal depth affected by hydrogen and to localize the trapping sites in the microstructure. The coupling of these two methods allowed to conclude about the role of the hydrogen generated by corrosion and to propose a mechanism to explain the embrittlement.
Possibility of Composite Cathodes with Sacrificial Salts
Authors: Okada Shigeto , Tsunoe Daisuke , Kitajou Ayuko , Hori Hironobu , Dimov Nikolay , Barpanda Prabeer 
Published: February 2020

Recently, Na3V2(PO4)2F3 [1] and alluaudite-type Na2Fe2(SO4)3 [2] have been reported as high voltage cathode materials for sodium-ion battery. Both of them, the rechargeable capacities are more than 100 mAh/g and the discharge voltages are almost 4 V against Na. So, the cathode performance of the Li counterparts against Li should be also interesting. Nevertheless, there is no report about the direct synthesis of Li3V2(PO4)2F3 and Li2Fe2(SO4)3. As for the alternatives, 3LiF-2VPO4 and Li2SO4-2FeSO4, which consist of the same compositions with Li3V2(PO4)2F3 and Li2Fe2(SO4)3
were synthesized by ball-milling method at room temperature.
The 3LiF-2VPO4/C and Li2SO4-2FeSO4/C were prepared by three-step mechanical ball-milling. First, the mixture of LiF (Wako) and VPO4 with the molar ratio of LiF:VPO4 = 3:2 was placed in the teflon-lined stainless container with T3-ZrO2 balls. As for Li2SO4-2FeSO4/C, the molar ratio of Li2SO4 and FeSO4 was 1:2. These mixtures were ball-milled using a planetary mill (Fritsch, Pulverisette7) with a rotation speed of 600 rpm for 6 h. Second, the obtained mixtures were ball-milled with 5 wt% acetylene black (AB, Denki Kagaku) with a rotation speed of 600 rpm for 3 h and then the resulting mixtures were ball-milled again with 20 wt% AB. All the procedures were carried out under argon atmosphere. The title compounds prepared by mechanical ball-milling were characterized by powder X-ray diffractometer (Cu-Kα, 50kV, 300mA) and Field emission electron microscope (FE-TEM, JEM-2100F). Electrode pellets were manually prepared by mixing 3LiF-2VPO4/C and Li2SO4-2FeSO4/C with 5% polytetrafluoroethylene (PTFE) and punched together with Teflon binder (Polyflon PTFE F-104, Daikin Industry) into disks (ca. 20 mg in weight and 10 mm in diameter). The electrochemical performance of the obtained composite cathodes were evaluated versus Li metal (Honjo Metal Co., Ltd.) in 2032 coin-type cells using nonaqueous electrolyte (1M LiPF6/EC : DMC = 1 : 1 in volume, Tomiyama Pure Chemical Industries) and polypropylene separators (Celgard 3501).
These materials showed an excellent reversible capacity corresponding to 2 Li reaction. The energy density of the obtained 3LiF-2VPO4
and Li2SO4-2FeSO4/C were 680 Wh/kg and 420 Wh/kg, respectively. In addition, the feasibility of these composite cathodes with sacrificial salts were also confirmed by the Li-ion type cell with graphite anode.
The initial discharge and charge efficiencies were more than 80% as shown in Fig. 1 and 2. They suggest that the cell reactions in the Li ion-type cells were actually attributed to the insertion and extraction of Li ions come from sacrificial salts such as LiF and Li2SO4.
References
[1] K. Chihara, A. Kitajou, I.D. Gocheva, S. Okada, and J. Yamaki, J. Power Sources, 227(2013) 80.
[2] P. Barpanda, G. Oyama, S. Nishimura, S. C. Chung, and A. Yamada, Nature Commun., 5, (2014) 4358.

Figure 1
On the Road Towards Ca-Based Batteries
Authors: Ponrouch Alexandre , Tchitchekova Deyana , Frontera Carles , Bardé Fanny , Palacin M Rosa 
Published: February 2020

The development of a rechargeable battery technology using light electropositive metal anodes would bring in a breakthrough in energy density, especially if it involves multivalent charge carriers. While effective electrolytes have been developed for magnesium which has enabled to achieve proof-of-concept for magnesium batteries, the electrodeposition of calcium was thought to be impossible and research restricted to non rechargeable systems. Calcium is an especially attractive alternative as it is the fifth most abundant element on earth crust and its standard reduction potential is only 170 mV above that of lithium, enabling significantly larger cell potential than that achievable with magnesium or aluminium.
The talk will revisit these aspects discussing the feasibility of reversible calcium plating/stripping using conventional alkylcarbonate electrolytes which impacts the prospects of developing a new calcium based rechargeable battery technology.
Stabilizing High-Voltage Layered Oxide Cathode Materials for Li/Na Ion Batteries
Authors: Yang Yong 
Published: February 2020

Li-ion battery systems have started to extend its roles from portable electronics, power tools to automobile applications such as hybrid and plug-in electric vehicles. However, it is necessary to enhance their electrochemical performance such as energy density and cycle life, for promoting their competition capability as vehicle power system. Obviously, electrode materials, especially positive electrode materials either working voltage or reversible capacity determine the energy density of the Li-ion batteries at mostly[1,2].
In the presentation, some new research progress of stabilizing high-voltage layered oxide cathode materials for Li/Na ion batteries in this group will be reported. Our strategies include two directions[3,4]: one is to improve the interface stability by using high voltage electrolyte additives or surface coating, another is to stabilize the lattice structure by using suitable element doping.
For example, when extending the working voltage of LiCoO2 from 4.2V to 4.4V or even more, we must develop some new electrolyte recipes to stabilize corresponding electrode/electrolyte interface at high voltage. Our recent results[5] show that a synergistic effects of suberonitrile-LiBOB binary additives in high-voltage cathode system, i.e. they could improve the cyclic performance of 4.5V LiCoO2 effectively. The corresponding working mechanism of the binary additives will be presented.
As to develop high energy density Na-ion battery, it is important to develop high-voltage cathode material. It is found that [6,7] the introduction of Zn2+ in the Na-Ni-Mn-O system can effectively overcome the drawback of voltage decay when charged to a higher cutoff voltage (>4.0 V), and significantly improve capacity retention compared to the unsubstituted material during cycling. In addition, a smoother charge/discharge profile can be observed between 3.0 and 4.0 V for Zn-substituted samples, demonstrating that Na+/vacancy ordering can be suppressed during sodium insertion/extraction. Na0.66Ni0.26Zn0.07Mn0.67O2 can deliver an initial capacity of 132 mAh g–1 at 12 mA g–1 with a high average voltage of 3.6 V and a capacity retention of 89% after 30 cycles. We have used a series of techniques such as in-situ XRD, in-situ XAS, ex-situ solid state NMR and HRTEM techniques to investigate the structural changes during cycling process and working mechanism of Zn2+ in the corresponding Na0.66Ni0.26Zn0.07Mn0.67O2 cathode materials.