Abstract We demonstrated high‐brightness large‐area, white organic light‐emitting diode (OLED) consisting of printing‐processed organic semiconductor layers. Meniscus printing process was applied to the substrate with 2 μm‐high stripe‐shape auxiliary electrodes. The OLED panel showed white emission all over the whole emitting area of 58 mm × 52 mm, high average luminance of 10,000 cd/m 2 , luminance uniformity of 40 %, and high luminous flux of 95 lm.
Lithium-ion batteries for automotive applications have required to enhance power density, low-temperature performance, life, energy density, and safety. All-solid-state batteries using lithium-ion conducting solid electrolytes have been much interest as candidates to respond to these demands. However, for practical applications, all-solid-state batteries have some problems to solve low charge-discharge performance under high rate and low temperature operations because of low ionic conductivities and large resistances of interface between the solid electrolyte and the active electrode material. We have focused on hybrid electrolytes consisting of lithium-ion conducting solid particles (LCSP) and a gel polymer electrolyte leading to a decrease of cell resistance, especially at low temperatures for LTO cells [1,2]. In this study, we have investigated effects of LCSP with liquid electrolytes in composite electrodes on electrochemical properties and electrode performance in order to develop high-power lithium-ion batteries using the solid electrolytes. NASICON-type Li-Al-Ti-P-O (LATP) particles with a particle size of submicron were used as LCSP. The composite electrodes consisted of LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) as cathode active material, carbon filler, polyvinylidene difluoride binder, and LATP particles, which were coated on aluminum foil as current corrector. Electrochemical measurements of the composite electrodes containing LCSP were performed using a three-electrode glass cell with a lithium metal foil counter electrode, a lithium metal chip reference electrode, a glass filter separator, and LiPF 6 -based liquid electrolytes. Figure 1 shows typical AC-impedance spectra of the composite electrodes with and without LATP particles at -20°C. The impedance spectra of both electrodes exhibited two depressed semicircles in the high- and low-frequency range, which can be interpreted as resulting from the passivating film formed on the NCM523 active material and the charge transfer process of lithium insertion, respectively. The ohmic resistances at 100 kHz such as the ionic resistance of electrolyte and the resistance of passivating film in the spectra showed no difference between the electrodes with and without LATP. On the other hand, it was noted that the charge transfer resistance of electrode with LATP was significantly smaller than that of electrode without one. Furthermore, the activation energy for the charge transfer of the electrodes with LATP is estimated into 55.7 kJ/mol, which is smaller than that of the electrode without LCSP as shown in Fig. 2. These results indicate that LCSP and liquid electrolytes in the electrodes plays an important role of reducing the charge transfer resistance rather than enhancing the lithium ion conductivity in the electrolytes. Therefore, we consider that LCSP in the electrode enhances to provide lithium ions in the liquid electrolyte to the surface of the active materials, leading to maintain high concentration of lithium ions at the surface of active material. The detail of the mechanism for reducing the charge transfer resistance by containing LCSP to the electrode will be discussed in this presentation. [1] K. Yoshima, Y. Harada and N. Takami, J. Power Sources , 302 ,283-290(2016). [2] N. Takami, K. Yoshima and Y. Harada, J. Electrochem. Soc. , 164 ,A6254(2017). Figure 1
Lithium ion batteries for automotive applications such as electric vehicles (EVs) have required to enhance power density, low temperature performance, energy density and safety. Recently, all-solid-state batteries using lithium-ion conducting solid electrolytes have been extensively studied to respond to these demands. However, all-solid-state batteries using solid electrolytes have some issues. Sulfide based solid electrolytes have low chemical stability and oxide electrolytes have large resistance at interfaces between active materials and solid electrolytes.We have developed hybrid electrolytes consisting of lithium-ion conducting solid particles and a gel polymer or liquid electrolyte [1]. The cell with hybrid electrolytes exhibited a low internal resistance, particularly at low temperatures. Moreover, we proposed the mechanism for reducing of the resistance because cyclic carbonates such as PC and PF 6 - anion on the surface of lithium-ion conducting solid particles enhance Li + transference number [2]. In this study, we have investigated the detail mechanism of reducing the resistance, and develop high-power lithium-ion batteries. We prepared 1Ah TiNb 2 O 7 /LiNi 0.5 Co 0.2 Mn 0.3 O 2 pouch cells with hybrid electrolytes to reveal the effective position of lithium-ion conducting solid electrolytes. Figure 1 shows schematic illustrations of the cross-section of the hybrid electrolytes cells. In cell-A, the solid electrolytes were coated on anode. In cell-B, the solid electrolytes layer are not in contact with active materials by inserting a separator. We compared cell-A and B with cell-C without the solid electrolytes layer. Li 1.2 Zr 1.9 Ca 0.1 (PO 4 ) 3 (LZCP) was used as a lithium-ion conducting solid electrolytes because of its wide potential window, high chemical stability and relatively low cost of raw materials. Figure 2 and 3(a) show discharge curves of cell-A, B and C at 25℃ and -30℃. The discharge curves of cell-A, B and C showed almost the same at 25℃. On the other hand, the discharge performance of cell-A and B was significantly superior to that of cell-C at -30℃. Comparing cell-A with cell-B, the time to reach 1.5V of cell-A was longer than that of cell-B. Furthermore, typical ac-impedance spectra of the hybrid cells at -30℃ are shown in Figure 3(b). The impedance spectrum exhibits a depressed semicircle. The semicircles of cell-A and B are smaller than that of cell-C. The semicircle of cell-A is smaller than that of cell-B. The semicircle can be interpreted as resulting from the interface resistance such as the charge-transfer process on the electrodes. The interface resistance at low temperature decreased by using the hybrid electrolyte even if the solid electrolytes don’t contact the electrode, however the solid electrolytes in contact with the electrode had the effect of reducing the interface resistance. Considering the above mentioned mechanism of the increasing of Li + transference number by hybrid electrolytes [2], it was indicated that the interface resistance decreased significantly by putting the solid electrolytes near the surface of the electrodes where the large concentration overpotential is caused during discharge at low temperature. The detail of this mechanism and the effect of reducing resistance by utilizing hybrid electrolytes will be discussed in this presentation. References [1] K. Yoshima, Y. Harada and N. Takami, J. Power Sources , 302 ,283-290(2016). [2] T. Kusama, K. Yoshima, T. Sugizaki, K. Hoshina, T. Sasakawa, Y. Harada, and N. Takami, Abstract No A02-0172, The Electrochemical Society Meeting Abstract MA2019-01, Dallas, TX, May 27 (2019) Figure 1
2,7-Difluo-carbazole and 2,4,5,7-tetrafluoro-carbazole were synthesized as new building blocks of wide-energy-gap host material for phosphorescent organic light-emitting diodes (PHOLEDs). These fluorinated positions in the carbazole ring were determined on the basis of density functional theory calculation results. Spectroscopic analyses supported the hypothesis that poly(N-vinyl-2,7-difluoro-carbazole) (2,7-F-PVK) with the fluorinated pendant group possessed a wide energy gap, leading to the exciton energy confinement on the blue phosphorescent dopant as well as nonsubstituted poly(N-vinyl-carbazole) (PVK). 2,7-F-PVK was used in solution-processed blue PHOLED to achieve 27 cd/A at 760 cd/m2, which is 1.8 times higher than that of nonsubstituted PVK. We assumed that the replacement of nonsubstituted PVK with 2,7-F-PVK improved the charge balance in the emission layer, while keeping the exciton confinement effect. The fluorination of the carbazole ring is a useful molecular design strategy for wide-energy-gap host material.
Lithium-ion batteries have been required to enhance power density, high and low temperature performance, energy density, and safety due to electrification of various mobilities. We have developed hybrid solid electrolytes consisting of lithium-ion conducting solid particles and a gel polymer or liquid electrolyte as candidate to respond to these demands [1]. Our previous study revealed that hybrid solid electrolytes in the cell reduce the internal resistance, particularly at low temperatures. Moreover, we proposed the mechanism of the resistance reduction, which the lithium ion transference number was increased by attracting the cyclic carbonates such as PC and PF 6 - anion on the surface of Lithium-ion conducting solid particles [2]. In this study, we have investigated the effect of hybrid electrolytes on the internal resistance of TiNb 2 O 7 (TNO)-based high-power lithium ion batteries. We prepared 1Ah TNO/LiNi 0.5 Co 0.3 Mn 0.2 O 2 (NCM) pouch cells with hybrid electrolytes consisting of lithium-ion conducting solid electrolyte wetted by PF 6 -based liquid electrolyte. The solid electrolyte layer was formed on cathode as shown in Fig.1. NASICON-type Li 1.2 Zr 1.9 Ca 0.1 (PO 4 ) 3 (LZCP) was used as a lithium-ion conducting solid electrolyte because of its wide potential window, high chemical stability, and relatively low cost of raw materials. We compared electrochemical properties of the LZCP-based hybrid electrolytes cell to that of the liquid electrolyte cell and the Al 2 O 3 (non-ion conductivity ceramic)-based hybrid electrolytes cell. The particle size and the film thickness of layer for Al 2 O 3 were comparable to those for LZCP. Figure 2 shows DC resistance (DCR) of the three types of cells at various state of charge (SOC) conditions for 10 sec charging at 25℃ and -20℃. The DCR of LZCP-based hybrid electrolyte cell is smaller than that of liquid electrolyte in the whole SOC range at 25℃. At low temperature, the difference of DCR of two cells becomes remarkable, and DCR of LZCP-based hybrid electrolyte cell is about 20% lower than that of liquid electrolyte cell at -20℃. On the other hand, the DCR of the Al 2 O 3 -based hybrid electrolyte cell was a little higher than that of liquid electrolyte cell in the all temperature range. Therefore, the solid electrolyte contributes to the reduction of internal resistance especially at low temperatures. Typical AC-impedance spectra of the cells with the three kinds of electrolytes at 25℃ and -20℃ are shown in Figure 3. The impedance spectra exhibit a depressed semicircle, which can be interpreted as resulting from the interface resistance such as the charge-transfer process on the electrodes. The semicircle of the hybrid electrolytes cell is significantly smaller than that of liquid electrolyte cell and Al 2 O 3 -based hybrid electrolyte cell especially at -20℃. It is considered that the concentration overpotential near the cathode mainly decreased due to the increase of lithium ion transference numbers by using solid electrolyte to promote the supply of lithium ion to the electrode surface. On the other hand, the LZCP-based hybrid electrolytes cell and the Al 2 O 3 -based hybrid electrolyte cell have a larger bulk resistance than that of the liquid electrolytes cell at 25℃. This bulk resistance is mainly ascribable to lithium ion conductive resistance in liquid electrolyte. The lithium ion conductive resistance increased because the porosity was decreased by inserting of solid electrolyte layer or Al 2 O 3 layer between electrodes. These results reveal that LZCP particles in the hybrid solid electrolyte reduces the charge transfer resistance between the electrolyte and active materials rather than the bulk ionic resistance in the electrolyte. The charge transfer resistance rapidly increases compared to the bulk ionic resistance with decreasing temperature. Therefore, it is considered that the DCR of LZCP-based hybrid electrolyte cell decreases especially at low temperatures. In this report, the detail of this hybrid electrolytes cell performance and the mechanism of resistance decreasing will be discussed. [1] K. Yoshima, Y. Harada and N. Takami, J. Power Sources , 302 ,283-290(2016). [2] T. Kusama, K. Yoshima, T. Sugizaki, K. Hoshina, T. Sasakawa, Y. Harada, and N. Takami, Abstract No A02-0172, The Electrochemical Society Meeting Abstract MA2019-01, Dallas, TX, May 27 (2019) Figure 1
Development of lithium-ion batteries for automotive applications such as electric vehicles (EVs) has been focused on enhancement of energy density, power, safety, and life. In particular, all-solid-state batteries have been extensively studied in order to respond to these demands. However, the solid electrolytes such as sulfide or oxide materials have important subjects for practical uses. Sulfide solid electrolytes have low chemical stability in air and low mechanical strength for thin separator. Oxide solid electrolytes have low ionic conductivity and large resistance at interfaces between active material and solid electrolyte. We proposed a thin hybrid electrolyte system instead of solid electrolytes [1] . The thin hybrid electrolyte consisting of lithium-ion conducting solid particles of a cubic garnet-type Li 7 La 3 Zr 2 O 12 (LLZ) and a gel polymer electrolyte exhibits smaller activation energy for ionic conductivity than a gel polymer electrolyte without LLZ. The fabricated cells using the hybrid electrolyte show high-rate charge-discharge performance [1, 2] . We have also investigated electrochemical properties of other hybrid electrolytes consisting of NASICON-type Li-Al-Ti-P-O (LATP) particles wetted with liquid electrolytes of LiPF 6 -PC/DEC. Figure 1 shows fast-charge performance of 1 Ah TiNb 2 O 7 /LiNi 0.5 Co 0.2 Mn 0.3 O 2 cells using the hybrid and the liquid electrolyte at 10 C rate. The charge performance of the cell using the hybrid electrolyte was significantly superior to that of the cell using the liquid electrolyte, which indicates the existence of LATP particles contributing to enhancement of migration of lithium ions in the hybrid electrolyte. Figure 2 shows high-rate discharge properties of the cells using the hybrid and the liquid electrolytes containing different LiPF 6 concentration. The voltage decline of the cells using the hybrid electrolytes were more gradual than that of the cell using the liquid electrolytes with LiPF 6 concentration of 0.5 M and 1 M. The difference between hybrid electrolytes and liquid electrolytes was clearly observed in the cell with LiPF 6 concentration of 0.5 M. In the case of a high LiPF 6 concentration of 2 M, the voltage decline of the cells using the hybrid and the liquid electrolytes showed almost no difference. Electrochemical kinetics on the discharge were more effectively enhanced by the existence of LATP particles wetted with the liquid electrolyte containing smaller amount of LiPF 6 . From these results, we considered that lithium-ionic conducting solid particles in hybrid electrolyte have effects to enhance lithium-ion conductivity by promoting lithium-ion migration on the surface of the solid particles and the amount of lithium-ions for charge transfer on the electrodes. However the detail of this mechanism for effects has not been cleared yet. In order to understand the phenomenon, it is determined that properties of lithium-ion conducting and electrochemical performances of hybrid electrolytes with different ratio of solid particles and liquid electrolyte and so on. In this presentation, we will discuss the role of lithium-ion conducting solid particles in hybrid electrolytes. References [1] K. Yoshima, Y. Harada and N. Takami, J. Power Sources , 302 ,283-290(2016). [2] N. Takami, K. Yoshima and Y. Harada, J. Electrochem. Soc. , 164 ,A6254(2017). Figure 1
We propose a new technique to fabricate a transmissive one‐side‐emission OLED panel with alignment‐free cathode patterning. This technique can reduce the non‐luminescent and non‐transparent area and result in the enlargement of luminescent area. The luminance of the fabricated panel was improved 1.28 times and high transmittance was kept.
Abstract We fabricated a transmissive one‐side‐emission organic light emitting diode (OLED) based on a stripe‐shaped cathode. The fabricated transmissive OLED whose panel size is 180 × 90 mm 2 showed high transmittance of 68% with the luminance ratio of the bright side to the dark side of 70.
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