Separators positive ribs

SEPARATOR STRUCTURE DESIGN AND FABRICATION 4.4.1 Positive Ribs... 

With the positive ribs facing the positive electrode, added oxidation protection is provided to the separator substrate or back-web thickness. In a typical automotive... 

A mixture of powdered poly(vinyl chloride), cyclohexanone as solvent, silica, and water is extruded and rolled in a calender into a profiled separator material. The solvent is extracted by hot water, which is evaporated in an oven, and a semiflexible, microporous sheet of very high porosity ( 70 percent) is formed [19]. Further developments up to the 75 percent porosity have been reported [85,86], but these materials suffer increasingly from brittleness. The high porosity results in excellent values for acid displacement and electrical resistance. For profiles, the usual vertical or diagonal ribs on the positive side, and as an option low ribs on the negative side, are available [86],... 

A long, hollow, cylindrical bowl is suspended by a flexible spindle and driven from the top as shown in Figure 13. Axial ribs in the bowl ensure full acceleration of the liquid during its short time in the bowl. Feed is jetted into the bottom of the bowl and clarified liquid overflows at the top, leaving deposited solids as compacted cake on the bowl wall. The clarifying performance of the bowl is reduced as the deposited cake decreases the effective outer radius of the bowl in accordance with equation 11. Consequently, cake capacity of the industrial model is limited to 0.1—10 L. For liquid—liquid separation, the interface position (eq. 26) is determined by selection of ring-dam diameter or by the length of a hollow nozzle-type screw dam. 

FIGURE 3.8 Coordinates for the hydrogen molecule. The nuclei are assumed stationary at fixed positions separated by the distance Rab- The distance of electron 1 from nuclei A and B is given by riA,riB the distance of electron 2 from nuclei A and B is given by r2A,i 2B, the distance between the electrons is given by 02. 

In contrast to most conventional separators for flooded batteries, separators for gel batteries have ribs positioned not only towards the positive plate, but also towards the negative plate in order to facilitate the gel-fllling process. For batteries with pasted positive plates, the separator is usually laminated with a glass fleece, which protects the positive plate against shedding, especially in cycle applications. Although this surface fleece stabilizes the active material, the present design of gel batteries cannot prevent completely the expansion of the positive material and the occurrence of PCL-2. The most important characteristics of separators used in gel batteries are listed in Table 7.2 (adapted from Ref. 12). 

In a flooded lead-acid battery, the sulfuric acid serves as both the electrolyte for conductance of the ions and it also promotes the electrochemical reaction. To achieve optimum performance from a battery, the amount of sulfuric acid should be stoichio-metrically balanced around the other reactants, namely, the positive and negative active material. The amount of electrolyte between electrodes is fixed by the 3D structure of the flooded lead-acid separator. Normally facing the positive electrode, there are ribs protruding off the planar surface of the substrate that serve to fix the distance between the electrodes and thus the volume available for the electrolyte [27]. Figures 4.9 and 4.10 illustrate some typical profiles. 

Traction batteries are assembled either with pasted and glass mat-wrapped positive electrodes, as is the case predominantly in the USA, or with tubular positive plates, which prevail in Europe. The former electrodes place no particular requirement on the separator profile vertical ribs on the positive side are standard. The construction with tubular positive electrodes preferably uses a diagonal (Figure 11.21) or sinusoidal (Figure 11.22) rib pattern. Insufficiently narrowly spaced supporting contact points between tube, rib, and separator backweb have... 

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