BaZrO3 nanorods are known to be effective pinning centers as c-axis-correlated pinning centers. Furthermore, BaZrO3 nanorods in REBa2Cu3Oy (RE: rare-earth element) films are formed by self-assembled stacking of BaZrO3 using a target mixture of a superconductor and BaZrO3 for pulsed-laser deposition, which is a very easy fabrication technique. The density of BaZrO3 nanorods in YBa2Cu3Oy (YBCO) films can be controlled by varying the BaZrO3 content in a target. The BaZrO3 addition has two functions for superconductivity; one is the improvement of pinning forces due to the addition of pinning centers and the other is Tc degradation. The optimum BaZrO3 addition for Jc improvement in magnetic fields is found to be around 3 wt% because of a trade-off between the two functions described above. Furthermore, the length of BaZrO3 nanorods is found to be controlled using two types of target: pure YBCO and a mixture of YBCO and BaZrO3. Varying the BaZrO3 nanorod length has an effect on the pinning mechanism. In particular, magnetic field angle dependences of Jc are varied from c-axis-correlated pinning to nearly random pinning by changing the nanorod length. The magnetic field at the crossover of the pinning mechanism seems to be adjusted by the BaZrO3 nanorod length.
The aerosol deposition method (ADM) is a technique to form dense films by impacting solid particles on a substrate. Dense ceramic films with thicknesses of over several¯m can be formed directly on substrates even at room temperature by the ADM. In this study, to improve the deposition efficiency of the ADM, the effect of the process for producing Al 2 O 3 particles on the deposition efficiency was investigated. Two types of commercially available ¡-Al 2 O 3 particles produced by sintering Al(OH) 3 (sintered particle) and chemical vapor deposition (CVD particle) were used. The average deposition efficiency of the sintered particles ranged from 0.067 to 0.088% and was much higher than that of the CVD particles, which ranged from 0.005 to 0.012%. When the sintered particles were used, the AD films grew about 30¯m. In contrast, when the CVD particles were used, the AD films didn't grow over several¯m. The morphologies of the AD films suggested that the deformed volume of the sintered particles was larger than that of the CVD particles. The specific fracture energy of each particle was estimated from a compression test. The average specific fracture energy of the sintered particles was 7.3 © 10 7 J/m 3 , which was about 32% of that of the CVD particles (2.3 © 10 8 J/m 3 ). Comparing this specific fracture energy with the specific kinetic energy, which was estimated to range from 4.4 © 10 7 to 1.8 © 10 8 J/m 3 , there is a possibility that the sintered particles showed higher deposition efficiency because they could deform by their kinetic energy and easily form activated surface promoting the bonding between the ceramic particles. We conclude that the specific fracture energy of the particle depends on the process for producing it and could be the crucial property to focus on to improve the deposition efficiency.
Introduction In conventional lithium ion battery (LIB), organic electrolyte exhibiting a high volatility and flammability is applied. Therefore, energy storage system with the LIB possesses a lot of auxiliary components for ensuring its safety, which do not directory contribute to electricity storage and lower its volumetric and gravitic energy density. Hence, the high safety of the LIB is the key to increase the volume energy density and the LIBs using several types of electrolytes such as a gel [1], a solid-state [2] and a quasi-solid-state [3] have been investigated. In particular, 100 Wh-class LIB using quasi-solid-state electrolyte (QSE) as a highly safe electrolyte demonstrated incombustibility in the nail-penetration test [3]. QSE is prepared by pseudo solidifying of solvate ionic liquid which consists of an equimolar mixture of lithium salt and tetraglyme(G4) at oxide particle surfaces. In this research, LIB manufacturing process using QSE that is highly compatible with conventional manufacturing processes was examined. Experiment Solvate ionic liquid, Li(G4)TFSA, was prepared by mixing an equimolar of lithium bis(trifluoromethanesulfonyl)amide, LiTFSA, and G4 [4]. Li(G4)TFSA, silica nano particle, and fluorine-based binder were mixed in a prescribed ratio. QSE sheet was prepared by coating and drying the mixture on the substrate. Li(G4)TFSA has a refractory characteristics. To prepare electrode containing Li(G4)TFSA, the electrode slurry including Li(G4)TFSA was coated and dried on the current collector foil. Li(Ni,Co,Mn)O2 pseudo-ternary oxide and graphite were used as the active material of the positive and negative electrode, respectively. The volatile mixed solution of propylene carbonate (PC) as low viscosity solvent [1] and vinylene carbonate (VC) for suppress the SEI formation was directly coated on the surface of the pressed electrode (coating method). In addition, QSE sheets and the electrode were stacked and heat-sealed by the four sides in order to suppress the volatilization of additive mixed solution (edge sealing structure). NMR analysis of the electrolyte components extracted by immersing in deuterated chloroform solvent after standing under manufacturing environment ( dew point : about -35℃) at various time ( for 0 to 24 hours) was carried out to examine the volatile behavior of PC and VC. Moreover, charge-discharge performance of LIB using QSE was evaluated by a model cell (diameter of electrode was less than 18 mm). Result and discussion In the previous research [5], the same charge-discharge performance as one of the conventional injection method was obtained by the coating method in which a small amount (5ml/cm2) of PC and VC mixed solution was directly coated on the electrode. It indicated that the injection process which had been a bottleneck in the LIB manufacturing process could be omitted. In order to apply the coating method to the mass production process, it is necessary to suppress concentration fluctuations of PC and VC by volatilization. In particular, the vapor pressure of VC is higher than the other electrolyte components. VC is an important component for SEI formation at the negative electrode interface. Concentration fluctuation of VC can be a factor for lowering LIB performance. Therefore, the edge sealing structure as shown in Figure 1 was prepared to seal the additive mixed solution. Figure 2 shows the relation between VC residual ratio and time. In the reference sample without applying the edge sealing structure, VC vapored quickly and the residual ratio decreased to about 60% after 30 minutes. On the other hands, VC residual ratio remained 93% even after 24 hours in the edge sealing structure, which proves the edge sealing can suppress VC volatilization significantly. Figure 3 shows the charge-discharge performance of LIB using QSE with the edge sealing structure. The charge-discharge performance of 24hours after coating the additive mixed solution did not deteriorate compared to the performance of immediately after coating. In this presentation, details of the manufacturing process using the coating method and the edge sealing structure will be discussed. References [1] S. Chereddy, Appl. Energy. Mater., 3, 279 (2020) [2] S. Ohta et al., J. Power Sources, 238, 53 (2013) [3] A. Unemoto et al., Electrochemistry, 87(1), 100 (2019). [4] K. Yoshida et al., J. Am. Chem. Soc., 133, 13121 (2011). [5] Y. Kaga et al., The 87th Electrochemical Society of Japan, 1G01 (2020). Figure 1
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