A much higher cell voltage of ca. 2.5 V than that of the typical Li-S battery was successfully achieved by combining the 5 V-class, spinel-type LiNi0.5Mn1.5O4 (LNMO) as a cathode and the ...rubber-derived sulfur composite as an anode. The cycling performance of the cell was improved by the PVDF coating only the cathode and coating both the cathode and anode, in which the discharge capacity retention increased from ca. 45 % to ca. 60 %. On the other hand, there was no difference in the cycling performance between the cell with the PVDF coating only the anode and the cell without the PVDF coating both the cathode and anode. There was no difference between the cycling performance of the half-cell of the LNMO cathode with the PVDF coating and without the PVDF coating, indicating that the PVDF coating on the cathode side does not prevent degradation of the electrolyte solution on the cathode surface. These results suggest that the PVDF coatings of the cathode surface play an important role as a protective layer in preventing the direct contact and side reaction between the polysulfides and cathode surface, thus leading to improvement of the cycling performance.
A rubber-derived sulfur composite cathode material for the Li-S battery/Li-ion battery was synthesized by the vulcanization process of butadiene rubber as a polymer source and a large amount of ...sulfur. In this study, the higher vulcanization temperature of 450 °C and a larger amount of sulfur (rubber : sulfur = 1 : 10, mass/mass) than the mass production process of the rubber were applied. The rubber-derived sulfur composite has a large amount of sulfur, ca. 58 wt% and a stable cycling ability with a capacity of 400 mAh g−1 at 30 °C. The cells consisting of the rubber-derived sulfur composite as the cathode and SiO as the anode displayed a great potential as for the next-generation LIBs because of its both electrodes containing no transition metals, outstanding electrochemical properties and safety performance. The cell showed a superior high and low temperature performance from −20–80 °C for over 100 cycles and a good rate performance in which the capacity of ca. 600 mAh g−1 was obtained at the 5 C-rate at 60 °C. In addition, there were no thermal runaway and no evolution of hydrogen sulfide in the nail penetration test.
We attempted to develop a disassembly- and reassembly-free Li pre-doping technique using perforated electrodes in order to develop Li-ion batteries containing a rubber-derived sulfur composite ...cathode. The Li pre-doping of the anodes was performed using perforated electrodes by external shorting between the anodes and Li metal electrodes provided on both end parts of the stacked electrodes within the cell, in which the degree of the Li pre-doping could be determined by the open circuit voltage measurement between the anodes and Li metal electrodes. The Li pre-doping of the graphite anodes in the cell composed of rubber-derived sulfur composite cathodes and graphite anodes was successfully conducted using this technique without disassembly and reassembly of the cell. After the Li pre-doping treatment, a stable charge-discharge was achieved between the rubber-derived sulfur composite cathodes and Li pre-doped graphite anodes. The Li pre-doping technique using the perforated electrodes was demonstrated to be applied even for practical 5 Ah cell. Furthermore, the Li pre-doping of the SiO anodes could be achieved in the cell composed of the perforated rubber-derived sulfur composite cathodes and SiO anodes, in which the cell showed a stable cycling performance and excellent charge-discharge rate performance.
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•The Li pre-doping technique using perforated electrodes was developed.•The cells using the sulfur composite cathode and graphite or SiO anode were prepared.•The Li pre-doping was performed by external shorting between the anodes and Li metal.•The Li pre-doping of graphite anodes was demonstrated in a 5 Ah cell.•The Li pre-doping of the SiO anodes was successfully conducted.
A much higher cell voltage of ca. 2.5 V than that of the typical Li-S battery was successfully achieved by combining the 5 V-class, spinel-type LiNi0.5Mn1.5O4 (LNMO) as a cathode and the ...rubber-derived sulfur composite as an anode. The cycling performance of the cell was improved by the PVDF coating only the cathode and coating both the cathode and anode, in which the discharge capacity retention increased from ca. 45 % to ca. 60 %. On the other hand, there was no difference in the cycling performance between the cell with the PVDF coating only the anode and the cell without the PVDF coating both the cathode and anode. There was no difference between the cycling performance of the half-cell of the LNMO cathode with the PVDF coating and without the PVDF coating, indicating that the PVDF coating on the cathode side does not prevent degradation of the electrolyte solution on the cathode surface. These results suggest that the PVDF coatings of the cathode surface play an important role as a protective layer in preventing the direct contact and side reaction between the polysulfides and cathode surface, thus leading to improvement of the cycling performance.
This paper reports the world-first system-level demonstration of dynamic wavelength allocation (DWA) on a wavelength-tunable (λ-tunable) wavelength division multiplexing/time division ...multiplexing-passive optical network (WDM/TDM-PON). To achieve DWA, a DWA calculation is necessary that determines new optical network unit assignments to the optical line terminal ports according to the bandwidth demand. In addition, a wavelength-tuning (λ-tuning) sequence that induces no data-frame loss, i.e., a hitless λ-tuning sequence, is essential. First, we propose a bidirectional hitless λ-tuning sequence and investigate its feasibility using media access control boards that we developed for symmetric 40-Gbit/s λ-tunable WDM/TDM-PONs, which are also the world's first. Then, with a DWA calculation according to the downstream traffic loads, we show automatic dynamic load-balancing operation.
We decommissioned the Nishina Memorial Cyclotron Center that was mainly used for PET/PIXE study until 2019. The main body of the cyclotron and peripheral equipment were separated as radioactive ...waste. For the concrete in the accelerator room building, radioactivity analysis of concrete core samples using a Ge detector, dose measurement of concrete surface using a CsI scintillation survey meter with a lead shield, and activation calculation using PHITS code were performed. The PHITS calculation with detailed modeling well reproduced the measurement result. The activated part was evaluated to have a depth of 21 to 41 cm, and the scraped concrete was treated as radioactive waste. All the work took 22 months. A practical procedure is proposed for the estimation of activated part of the concrete.
This paper presents the world's first field trial of a 40-km reach and over 512-split symmetric-rate 40-Gbit/s λ-tunable time and wavelength division multiplexing passive optical network (TWDM-PON) ...that utilizes our newly developed high-speed λ-tunable optical network unit transceivers and automatic gain controlled semiconductor optical amplifier-based PON extender for repeater and central office use. The upstream signals for C-band and downstream signals for L+-band in our developed λ-tunable TWDM-PON comply with the wavelength plan of ITU-T G.989 series. In a field trial, we successfully demonstrate error free λ-tunable transmission for the 40-km reach and 1024-split (maximum number) symmetric-rate 40-Gbit/s λ-tunable TWDM-PON over installed standard single-mode fiber links, and advanced network functions such as dynamic load balancing, incremental system upgrade, optical subscriber unit protection, and OLT equipment power saving are also confirmed.
This paper presents the world s first field trial of a 40-km reach and over 512-split symmetric-rate 40-Gbit/s -tunable time and wavelength division multiplexing passive optical network (TWDM-PON) ...that utilizes our newly developed high-speed -tunable optical network unit transceivers and automatic gain controlled semiconductor optical amplifier-based PON extender for repeater and central office use. The upstream signals for C-band and downstream signals for L -band in our developed -tunable TWDM-PON comply with the wavelength plan of ITU-T G.989 series. In a field trial, we successfully demonstrate error free -tunable transmission for the 40-km reach and 1024-split (maximum number) symmetric-rate 40-Gbit/s -tunable TWDM-PON over installed standard single-mode fiber links, and advanced network functions such as dynamic load balancing, incremental system upgrade, optical subscriber unit protection, and OLT equipment power saving are also confirmed.
This paper clarifies the scalability of the hitless wavelength-tuning (λ-tuning) sequence for dynamic wavelength allocation (DWA) on a λ-tunable ...wavelength-division-multiplexing/time-division-multiplexing passive optical network (WDM/TDM-PON). The λ-tuning that induces no data-frame loss, i.e., hitless λ-tuning, is essential in DWA. We derive requirements to prevent two types of upstream data-frame loss that the λ-tuning causes. To clarify the scalability of the hitless λ-tuning sequence against system parameters, we theoretically analyze the maximum input data rate to the optical network units (ONUs) to achieve λ-tuning without upstream data-frame loss while varying values for buffer size and λ-tuning time of the transceivers in ONUs and the DWA cycle. Then, using media access control boards that we developed for symmetric 40 Gbit/s λ-tunable WDM/TDM-PONs, we demonstrate hitless λ-tuning and confirm the validity of the theoretical analysis.
