Widening the working voltage of lithium-ion batteries is considered as an effective strategy to improve their energy density. However, the decomposition of conventional aprotic electrolytes at high voltage greatly impedes the success until the presence of high concentration electrolytes (HCEs) and the resultant localized HCEs (LHCEs). The unique solvated structure of HCEs/LHCEs endows the involved solvent with enhanced endurance toward high voltage while the LHCEs can simultaneously possess the decent viscosity for sufficient wettability to porous electrodes and separator. Nowadays, most LHCEs use LiFSI/LiTFSI as the salts and β-hydrofluoroethers as the counter solvents due to their good compatibility, yet the LHCE formula of cheap LiPF6 and high antioxidant α-hydrofluoroethers is seldom investigated. Here, we report a unique formula with 3 mol L−1 LiPF6 in mixed carbonate solvents and a counter solvent α-substituted fluorine compound (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether). Compared to a conventional electrolyte, this formula enables dramatic improvement in the cycling performance of LiCoO2//graphite cells from approximately 150 cycles to 1000 cycles within the range of 2.9 to 4.5 V at 0.5 C. This work provides a new choice and scope to design functional LHCEs for high voltage systems.
Abstract. The problem of pedestrian across the street during the red light is always a focus of China's urban traffic management and difficult. This phenomenon has been improved after years of renovation in some developed cities such as Beijing. However, in some middle-sized and small cities, the problem of pedestrian across the street during the red light is still serious. Pedestrians as vulnerable groups of the traffic participants, more likely hurt by motor vehicle. The problem of pedestrian across the street during the red light is not only a violation of traffic regulations and seriously affect traffic order, increasing the possibility of accidents at the same time. Pedestrian traffic is the weaknesses of urban traffic system, it's meaningful to study on characteristics of pedestrian crossing. We used survival analysis for modeling the process of pedestrian's waiting. According to the survey data of the waiting time which the pedestrians across the street in Shijingshan, we acquire a survival curve of waiting time in three groups of old people, middle-aged people and young people. The result shows that the pedestrians on the roadside waiting to cross the street is 34s, and recommend that the maximum red time in Shijingshan is less than 50s. Reasonable control can improve compliance rates, and reducing the risk of violation.
TAPO-5 membranes were synthesized through a tertiary growth method. Its perfection significantly depends on the adopted seed and itself poly-crystalline structure. Amorphous seed synthesized at a low crystallization temperature (393 K), obviously favors producing the perfective TAPO-5 membrane. TAPO-5 crystal seed, however, induces the growth of its membrane with a larger extent of cracks (i.e., grain boundary defect), destructing itself perfection. Those diverse results are associated with the disparate seeds layers deposited by a spreading-wetting method, and consistently demonstrated by SEM, XRD, and single gas (He) permeation test. A typical feature of the amorphous TAPO-5 seed layer is its dispersive distribution pattern in the macro holes of support. A continuous layer, however, is observed for the TAPO-5 crystal seed layer. The amorphous seed is explained as a prior seed for the perfective TAPO-5 membrane.
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