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Volumetric changes associated with solvent/electrolyte exchange in electronic conducting polymers (ECPs) play an important role in the mechanical stability of the polymers, as these changes are a critical factor in ECP-based energy storage devices. Thus, the present work explores the hindering of such volumetric deformations for polypyrrole films doped with dodecylbenzenesulphonate (PPy(DBS)) by employing highly concentrated aqueous electrolytes (or water-in-salt electrolytes, WiSEs), and their effects over the corresponding electrochemical capacitor cell energy retention. Electrochemical quartz crystal microbalance with dissipation monitoring measurements for thin PPy(DBS) films in the WiSEs revealed negligible dissipation changes (ΔDn ≈ 0), in contrast with those in dilute aqueous electrolyte (ΔDn ≠ 0), indicating inexpressive structural deformation of PPy(DBS) in the WiSE. This phenomenon is observed for thick freestanding PPy(DBS) films, which presented a maximum bending angle decay from ∼56° (diluted aqueous electrolyte) to 3.5° when working in the WiSE, thus proving the hindering of film bending. The observed trends are reflected in the PPy(DBS) cell energy retention, where the use of a WiSE decreased cell energy fading by 30% after 600 cycles, in comparison with cells based on diluted electrolytes.

Electrochemical capacitors show high power density but suffer from low energy density. The use of pseudocapacitive material can increase the cell capacitance and therefore increase the device energy density. In this work, we show that using microtubular conducting polymers, as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), alongside activated carbon (AC) in asymmetrical devices, and highly concentrated aqueous electrolyte (or water-in-salt electrolyte, WiSE), is possible to maintain the polymers electroactivity at the negative polarization and take advantage of the electrolyte electrochemical stability. The polymers electrochemical behaviours were compared in WiSE and aqueous acidic solution, which hinted that the polymers charge compensation are different in the different electrolytes. PPy-AC and PEDOT-AC cells can reach 2.6 and 2.8 V, respectively, and electrodes mass balance greatly depends on the polymers open circuit potential before and after cycling

In the second part of the review on electrochemical energy storage, the devolvement of batteries is explored. First, fundamental aspects of battery operation will be given, then, different materials and chemistry of rechargeable batteries will be explored, including each component of the cell. In negative electrodes, metallic, intercalation and transformation materials will be addressed. Examples are Li or Na metal batteries, graphite and other carbonaceous materials (such as graphene) for intercalation of metal-ions and transition metal oxides and silicon for transformation. In the positive electrode section, materials for intercalation and transformation will be reviewed. The state-of-the-art on intercalation as lithium cobalt oxide and nickel containing oxides will be approached for intercalation materials, whereas sulfur and metal-air will also be explored for transformation. Alongside, the role of electrolyte will be discussed concerning performance and safety, with examples for the next generation devices. Finally, a general future perspective will address both electrochemical capacitors and batteries.

The Nobel Prize in Chemistry 2019 recognized the importance of Li-ion batteries and the revolution they allowed to happen during the past three decades. They are part of a broader class of electrochemical energy storage devices, which are employed where electrical energy is needed on demand and so, the electrochemical energy is converted into electrical energy as required by the application. This opens a variety of possibilities on the utilization of energy storage devices, beyond the well-known mobile applications, assisting on the decarbonization of energy production and distribution. In this series of reviews in two parts, two main types of energy storage devices will be explored: electrochemical capacitors (part I) and rechargeable batteries (part II). More specifically, we will discuss about the materials used in each type of device, their main role in the energy storage process, their advantages and drawbacks and, especially, strategies to improve their performance. In the present part, electrochemical capacitors will be addressed. Their fundamental difference to batteries is explained considering the process at the electrode/electrolyte surface and the impact in performance. Materials used in electrochemical capacitors, including double layer capacitors and pseudocapacitive materials will be reviewed, highlighting the importance of electrolytes. As an important part of these strategies, synthetic routes for the production of nanoparticles will also be approached (part I).

Joint sample tests have been carried out as a qualification test for ITER Toroidal Field (TF) coils. The joint sample comprises two short TF conductors that have “twin-box” joint terminals at both ends. The lower joint is a testing part that is a full size joint of the TF coils. Hall probes are attached on the lower joint box at around the center of the external field coil of the test facility. The magnetic field induced by shielding currents in the joint can be estimated from the difference between the measured magnetic field strength and the magnetic field generated by the external field coil. The magnetic field by the shielding currents during shut-off of the external field coil from -1.0 T is evaluated for six samples. The decay time constants of the shielding currents are gradually elongated with decrease of the shielding currents in all the samples. In comparison with simulation results, it is considered that the main shielding current flows in superconducting cables in the two conductors with crossing the jointed plane and that the joint resistance is decreased at low total current.

A superconducting magnet for the Fixed Field Alternating Gradient (FFAG) accelerator has been proposed. The static magnetic field is required to be proportional to the k-th power of the orbit radius where k is the geometrical field index of the accelerator. A left/right asymmetric coil with elliptical aperture is utilized to maximize the horizontal aperture with a compact design. The saddle shaped coil configuration is designed to fulfil the design requirement in terms of integral magnetic field along an arc orbit. In a beam tracking simulation, a particle was circulated and accelerated with the magnetic field generated by the designed coil. A prototype superconducting coil with a cylindrical bore was developed and the field quality was evaluated at warm field measurement

A superconducting magnet for a Fixed Field Alternating Gradient (FFAG) accelerator is proposed. The static magnetic field is required to be proportional to the k-th power of the orbit radius where k is the geometrical field index of the accelerator. The left/right asymmetric coil with elliptical aperture is introduced to maximize the horizontal aperture with a compact magnet design. The 3D coil configuration is designed to meet the requirement in terms of integral magnetic field. The 3D magnetic field is evaluated and the field integral along the beam trajectory satisfies the beam optics requirement of the FFAG accelerator.

The required magnetic field for the fixed field alternating gradient (FFAG) accelerator is proportional to the k-th power of the orbit radius where k is the field index of the accelerator. Although the field is constant in time, the design of the magnets is more difficult than that of the conventional synchrotron due to the intrinsically nonlinear field. There are several ways to design the FFAG magnet. The "iron pole shape" makes the field by changing the pole gap size along the radius, which is the most conventional and suitable for the compact FFAG. Another way is a "pole face winding" where the field is produced by distributing the coil current along the radius. Although it is a challenging design, a large and high field FFAG is feasible. The third one is a "multipole combination" in which the magnetic field is generated by combining the multipole components of the fields. This could be applied to superconducting magnets. The FFAG has the potential for various applications, and the magnet design of the FFAG should be selected properly for each application.

Thermal stability of a conduction-cooled Bi-2223/Ag pancake coil has been investigated by means of a time dependent numerical analysis. The coil is cooled by a cryocooler through a cooling plate. This study focused on the temperature profile in the coil and the thermal runaway current. It is suggested from the present analysis that not only enlarging the attached area of the cooling plate to the coil but also dispersing the cooling plate is an effective way to improve the thermal stability of a conduction-cooled HTS coil.

We have measured contact resistance between superconducting strands that was a parameter of coupling losses in cable-in-conduit conductors. Assuming some kinds of twist pitches of sub-cables in the multi-stranded cables, we measured the contact resistance under the condition of the intersecting strands. Since not only the resistance but also mechanical properties of the strands (applied force to the strands and deformation of the strands due to the force) were measured, the contact area could be precisely estimated, and then the surface resistance was also evaluated. The experimental results showed that the surface resistance hardly depended on the twist pitches of the sub-cables at both liquid nitrogen and liquid helium temperatures. The results become fundamental data to estimate the coupling losses caused by current loops including more than one sub-cable with long-time constants of current decay.

A superconducting magnet for a Fixed Field Alternating Gradient (FFAG) accelerator has been proposed. The required magnetic field is static and proportional to the k-th power of the orbit radius where k is the geometrical field index of the accelerator. In 2D, the required magnetic field can be generated with the optimized cross section of the coil. The cross section of the coils is a left-right asymmetry to simplify the cross section and ellipse to downsize the magnet. Local and integral 3D fields along the beam trajectory are evaluated with using new type of 3D coil configuration.

The grain boundary character distributions in cast, recrystallized and strain annealed Ni3Al alloys with a composition of Ni23Al were examined to clarify the relation between ductility and the grain boundary character distributions in Ni3Al. The percentages of CSL boundaries in cast, recrystallized and strain annealed Ni3Al alloys are 26.8, 43.1 and 58.4%, respectively, of the total number of boundaries examined. The sum of the percentages for LAB (Low Angle Boundary) and Σ3 boundary in cast, recrystallized and strain annealed Ni3Al alloys is 4.46, 10.8 and 29.2% respectively. This indicates that strain annealing is effective in enhancing the frequency of occurrence of CSL boundaries, especially LAB and Σ3 boundary, in Ni3Al. The strain annealed Ni3Al alloy having a much higher frequency of CSL boundaries is found to exhibit elongation to fracture of more than 45%. This significant increase in elongation of the strain annealed Ni3Al alloys is attributed to the presence of relatively low energy LAB and Σ3 boundaries.

Polyaniline film was synthesized electrochemically with HBF4 as an electrolyte. A potential was changed step by step to measure ESR spectra. At low doping levels ESR line shape was found to be a single Lorentzian. At higher doping levels, however, it was composed of double Lorentzians; narrow line and broad one. An integral intensity of the broad line becomes larger than that of the sharp one at the higher potentials. Temperature dependence of spin susceptibility suggested that the sharp line behaves as a Curie spin and the broad one does as a Pauli one, which is consistent with low frequency ESR result on the chemically prepared emeraldine salt with BF4−. The sharp line can be interpreted as a polaron created in an initial stage of the electrochemical doping. Presumable origin of the broad line was discussed.

Helical coils of the Large Helical Device (LHD) are large scale superconducting magnets for heliotron plasma experiments. The helical coils had been cooled by saturated helium at 4.4 K, 120 kPa until 2005. An upgrade of the cooling system was carried out in 2006 in order to improve the cryogenic stability of the helical coils and then it has been possible to supply the coils with subcooled helium at 3.2 K, 120 kPa. A designed mass flow of the supplied subcooled helium is 50 g/s. The subcooled helium is generated at a heat exchanger in a saturated helium bath. A series of two centrifugal cold compressors with gas foil bearing is utilized to lower the helium pressure in the bath. The supplied helium temperature is regulated by rotational speed of the cold compressors and power of a heater in the bath. The mass flow of the supplied helium is also controlled manually by a supply valve and its surplus is evaporated by ten heaters at the outlet above the coils. In the present study, the performance of the cooli...

Superconducting combined function magnets will be utilized for the 50 GeV, 750 kW proton beam line for the J-PARC neutrino experiment. The magnet is designed to provide a dipole field of 2.6 T combined with a quadrupole field of 19 T/m in a coil aperture of 173.4 mm at a nominal current of 7345 A. Two full-scale prototype magnets to verify the magnet performance were successfully developed. The first prototype experienced no training quench during the excitation test and good field quality was confirmed.