The formation of LiOH and Li 2 CO 3 impurities on high Ni content LiNi 0.83 Co 0.15 Al 0.02 O 2 powders due to H 2 O and CO 2 absorption from the air can be reduced without structural degradation by washing in water. Although the as-synthesized sample had a moisture content of 570 ppm immediately after firing, this level increased rapidly to 1270 ppm in air with a relative humidity of 50%. However, its content was decreased to 210 ppm after washing twice in water, followed by heat-treatment at 700°C. It is believed that this improvement was due to the decreased level of Li 2 CO 3 and LiOH impurities on the particles. This was highlighted by the decreasing swelling of the Li-ion cell at 90°C, and the thickness of the cell containing the washed samples was decreased by 50% compared with the bare sample.Since the 1200 mAh Li-ion cell in a cylindrical 18650R size was developed in 1991, its capacity has been increasing by 7-10% each year, and a 2400 mAh Li-ion cell was commercialized in 2004. Despite the fact that the electrode materials used were graphite and LiCoO 2 , the capacity has increased by 100% compared with the capacity 12 years ago. The achievement of such a high capacity was made possible by the maximum utilization of the dead spaces within the cell, decreasing the amount of binder and conducting agents, and using LiCoO 2 with a high electrode density 3.7 g/cm 3 . However, increasing the capacity beyond 2400 mAh can only be made possible using new high capacity active materials, such as Si, Sn, or LiNi 1−x−y Co x Mn y O 2 with a 4.2 V cutoff. 1-5 One of the fundamental problems of the LiNi 1−x−y Co x Mn y O 2 , where 1 − x − y is Ͼ0.8 ͑high Ni content͒ is the rapid reaction with air resulting in the formation of Li 2 CO 3 and LiOH on the surface. 6-8 Zhuang et al. reported the presence of Li 2 CO 3 on the surface of LiNi 0.8 Co 0.15 Al 0.05 O 2 powder exposed to air, and the long-term exposure of the cathode produced a dense Li 2 CO 3 coating, approximately 10 nm in thickness, which severely reduces the capacity and increased the irreversible capacity, according to the following equation LiNi 0.8 Co 0.15 Al 0.05 O 2 + 4xO 2 + 2xCO 2 → Li 1−x Ni 0.8 Co 0.15 Al 0.05 O 2 + 2xLi 2 CO 3 . Moshtev et al. also reported the formation of LiOH on the LiNiO 2 as a result of oxygen evolution: LiNiO 2 + yH 2 O → Li 1−y NiO 2−y/2 + yLiOH. 8 In addition, the extraction of Li from Li 1.1 NiO 2 in water led to a rapid decrease in capacity, and the discharge capacity of the washed powder was reduced to 150 mAh/g from 181 mAh/g. 9 Recently, Yang et al. reported that surface-active oxygen O 2− from an impurity NiO phase that combined with CO 2 and H 2 O in air to form CO 3 2− and OH − , and suggested the following surface reaction mechanism: 2Li + + CO 3 2− /2 OH − → Li 2 CO 3 /2LiOH. 10 The presence of such impurities led to severe cell swelling during the formation process in the Li-ion cell manufacturing and at 90°C storage at the 4.2 V charged state. Therefore, this study investigated the effect of washing on an air-expo...
Although LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode material has a larger specific capacity than LiCoO 2 , their thermal instability has hindered their use in Li-ion cells. An AlPO 4 coating on the LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, however, noticeably diminished the violent exothermic reaction of the cathode material with the electrolyte, without sacrificing the specific capacity of the bare LiNi 0.8 Co 0.1 Mn 0.1 O 2 ͑188 mAh/g at 4.3 V charge cut off͒. The results were consistent with the thermal abuse tests using Li-ion cells; the AlPO 4 -coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode did not exhibit thermal runaway with smoke and explosion, in contrast to the cell containing the bare cathode. In addition, the AlPO 4 -coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode exhibited a superior cycle-life performance compared to the bare LiNi 0.8 Co 0.1 Mn 0.1 O 2 .
Despite the fact that the same coating concentration and annealing temperature are used for MPO 4 nanoparticle coatings ͑M = Al, Fe, Ce, and SrH͒ on a LiCoO 2 cathode, the extent of the coating coverage is influenced by the nanoparticle size or morphology. Nanoparticles ͑AlPO 4 or FePO 4 ͒ with a size smaller than 20 nm led to the complete encapsulation of LiCoO 2 , but those with sizes greater than 150 nm ͑CePO 4 ͒ or with whisker shapes ͑SrHPO 4 ͒ led to partial encapsulation. This difference affected the discharge capacity. The LiCoO 2 completely encapsulated with AlPO 4 or FePO 4 showed the highest discharge capacity of 230 mAh/g at 4.8 and 3 V at a rate of 0.1 C ͑=18 mA/g͒, which diminished with decreasing coating coverage in the order of Al ϳ Fe Ͻ SrH Ͻ Ce Ͻ bare cathode. However, the capacity retention during cycling increased in the order of Al Ͼ Ce Ͼ SrH Ͼ Fe Ͼ bare cathode. This is consistent with the capacity retention result obtained at 90°C storage for 4 h.In 1996, Bellcore patented an Al 2 O 3 , B 2 O 3 , and SiO 2 coating on spinel LiMn 2 O 4 to suppress Mn dissolution from LiMn 2 O 4 at elevated temperatures. 1 However, it was found that the irreversible capacity and capacity retention of the coated sample was inferior to the bare sample despite the lower Mn dissolution rate at 55°C storage. They reported the examples of B 2 O 3 -coated spinel at elevated temperature only, and there was no explanation for the decreasing capacity retention after the coating, compared with the bare cathode. Such deteriorated behavior of the coated cathode may be associated with the formation of a thick coating layer that impedes the Li diffusivity. To overcome these problems, LiCoO 2 , which has a strong resistance to HF, was coated on the LiMn 2 O 4 and showed improved capacity retention and lower irreversible capacity during cycling at 55°C. 2 On the other hand, LiMn 2 O 4 was coated on LiCoO 2 to improve the thermal stability of the delithated Li x CoO via the solgel method have been intensively investigated. 4-15 Among these coating materials, ZrO 2 coating exhibited the best capacity retention Ͼ4.5 V cycling, and hightemperature storage at 90°C. This finding was confirmed by Kim et al., and among the ZrO 2 , Al 2 O 3 , and SiO 2 coatings, the ZrO 2 coating on LiMn 2 O 4 had to the lowest capacity fading at 55°C cycling. 14 This improvement was due to the fact that ZrO 2 behaves as an effective HF scavenger. 14 Overall, these studies revealed that the physical morphology of the coating materials significantly influenced the electrochemical properties.Metal phosphates ͑M = metal ion͒ are of great interest for many applications, for example, as molecular sieves or size-selective catalysts, catalysts supports, or optical materials, and their application have varied depending on the pore size, particle size, and metal ions. [15][16][17][18][19][20][21][22] Dong et al. prepared mesoporous AlPO 4 by templating AlCl 3 and triethylphosphate with carbon spheres with a particle size of ϳ100 nm, which was removed by calcin...
A wheel drive mechanism is simple, stable, and efficient, but its mobility in unstructured terrain is seriously limited. Using a deformable wheel is one of the ways to increase the mobility of a wheel drive robot. By changing the radius of its wheels, the robot becomes able to pass over not only high steps but also narrow gaps. In this article, we propose a novel design for a variable-diameter wheel using an origami-based soft robotics design approach. By simply folding a patterned sheet into a wheel shape, a variable-diameter wheel was built without requiring lots of mechanical parts and a complex assembly process. The wheel's diameter can change from 30 to 68 mm, and it is light in weight at about 9.7 g. Although composed of soft materials (fabrics and films), the wheel can bear more than 400 times its weight. The robot was able to change the wheel's radius in response to terrain conditions, allowing it to pass over a 50-mm gap when the wheel is shrunk and a 50-mm step when the wheel is enlarged.
The present study was conducted to investigate whether dietary sanguinarine (Sangrovit ® , SGV) could affect growth performance, relative organ weigths, gut microbiota, serum cholesterol levels, and malondialdehyde contents of leg meat in broiler chickens. A total of 840 day-old male broiler chicks (Ross breed) was randomly placed on 28 floor pens with rice straw as a bedding and subjected to one of four experimental diets; corn-soybean meal based control diet, the control diet added with avilamycin at 10 ppm as growth promoter (AGP) and SGV at the level of 20 (SGV20) or 50 ppm (SGV50). The final body weight (BW), daily BW gain, and feed conversion ratio (FCR) were significantly improved (P<0.05) in broiler chickens fed either AGP, SGV20 or SGV50 compared with the control diet-fed chickens. Compared with the control group, relative jejunal weight was significantly lowered (P<0.05) in SGV20-fed chickens and relative jejunal or ileal length was significantly increased (P<0.05) in all SGV-fed chickens. Dietary SGV20, but not AGP, altered gut microbiota (especially increase in cecal lactic acid bacteria) compared with the control diet-fed chickens. Total cholesterol of broiler chickens fed on a diet containing SGV20 or SGV50 vs. the control diet was significantly reduced. Finally, the content of malondialdehyde in thigh meats as an indicator of lipid peroxidation was significantly lowered (P<0.05) by dietary SGV compared with that seen in the control chickens. In conclusion, our study clearly reveals that supplementation of SGV into the broilers' diet at 20 or 50 ppm improved growth performance and altered various biological and physiological parameters such as relative organ weights, serum cholesterol levels, gut microbiota, and meat qualities in broiler chickens.
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