Spirally rolled cells

It should be noted that the rechargeable cells discussed later have the same construction and differ only in separator type, electrode composition and cathode / anode balance. For comparison, Fig. 3 shows the design of an AA-size lithium cell. The construction with a spirally rolled electrode increases the power output. 

Example of autowaves of first-order roll-cells of Marangoni instability (left pictures) and of BZR (right pictures), a) concentric rings, b) spirals, according to Linde and co-workers... 

Cylindrical Cells using Spirally Rolled Construction... 

Figure 22. Cycle performance of spirally rolled RAM cells (0.03 % Hg).

Principally two versions of spirally rolled RAM cells can be produced fully charged and nearly discharged cells. The Mn02 cathode can either be partly or completely prereduced in a batch process [48] and the zinc anode may consist mainly of zinc oxide. This special version is easier to manufacture and the shelf life in the nearly discharged state is probably unlimited. But initial charging is required for a 100 % discharge capacity of the first cycle. 

In an attempt to increase the specific electrode area of the reactor, electrodes, spacers, and separators are wound in a spiral form (Fig. 5.10) in the Swiss Roll cell. Electrolyte flows axially in the narrow channels between electrodes and separator. In this compact design, the main problem is the need for flexible foil electrodes, spacers, and separators and the cost and difficulty of replacing damaged components. Nevertheless, the design has been used for relatively small-scale organic applications. " ... 

Spirally Wound Cell A cylindrical cell which uses an electrode structure made by winding the electrodes and separators into a cylindrical jelly-roll construction. (See Fig. 28.2 and Fig. 14.8). 

Two contrasting examples of porous three-dimensional electrodes are shown in Fig. 2.35. The Swiss-roll cell (Fig. 2.35(a)) consists of an electrode-separator or spacer-electrode sandwich spirally wound, usually with axial flow through the mesh electrodes. The mass transport is promoted by textured electrodes and/or plastic mesh turbulence promoters which also serve as membrane-electrode spacers. The interelectrode gap is small (0.2-2 mm), providing a low cell voltage... 

Before myelination the axon lies in an invagination of the Schwann cell (Fig. 4-10A). The plasmalemma of the cell then surrounds the axon and joins to form a double membrane structure that communicates with the cell surface. This structure, called the mesaxon, then elongates around the axon in a spiral fashion (Fig. 4-10). Thus, formation of myelin topologically resembles rolling up a sleeping bag the mesaxon winds about the axon, and the cytoplasmic surfaces condense into a compact myelin sheath and form the major dense line. The two external surfaces form the myelin intraperiod line. 

Both the lithium sulfur dioxide (Li-SO and lithium thionyl chloride (Li-SOCy cells may be classified as liquid cathode systems. In these systems, S02 and SOCl2 function as solvents for the electrolyte, and as the active materials at the cathode to provide voltage and ampere capacity. As liquids, these solvents permeate the porous carbon cathode material. Lithium metal serves as the anode, and a polymer-bonded porous carbon is the cathode current collector in both systems. Both cells use a Teflon-bonded acetylene black cathode structure with metallic lithium as the anode. The Li-S02 is used in a spirally wound, jelly-roll construction to increase the surface area and improve... 

Self-assembly of phospholipids, such as phosphatidylcholine, a nutritional supplement, in the presence of calcium creates 50-500 nm large, continuous, solid, lipid bilayer sheets rolled into a spiral structure termed nanocochleates.f These can be made to envelope a lipid-soluble drug, such as amphotericin B, to exclude water and protect against pH, oxidation, light, enzymatic attack, hydrolysis, and extremes in temperature. The nanocochleates will convert to liposomes at a pH greater than 6.5 in a calcium deficient environment as is found in the cell (typically less than 1-2... 

For many years, cells with electrolyte gelled by the addition of sodium siUcate or sulphuric acid adsorbed onto a felted glass fibre mat or thick paper have been manufactured such cells avoid the hazards of acid spillage and were sold mainly for aircraft or motorbikes. Now cylindrical lead/acid cells, typical capacity 2 A h and without free electrolyte, are produced to compete with small Ni/Cd and primary cells for the consumer market. These cells are spirally wound (as a Swiss roll) with electrodes of thin, pure lead sheet perforated to increase the amount of pasted active material adhering to the metal and an adsorbent glass fibre paper separator, packed into a metal can. 

Spiral devices can be fabricated in flexible PMMA using roU-to-roll processing and can be used for sorting different cell types. The cascading of spiral systems to sort more than 4—5 cell... 

Hollow fiber modules are sometimes used to culture animal cells that are confined to the shell side of the module the separately oxygenated nutrient solution flows inside the fibers and perfuses the cells on the shell side. In the spiral membrane reactor (Fig. 17), the membrane that contains the immobilized enzyme is rolled into a spiral and confined within a shell. The feed or reactant solution flows in at one end and the product is removed from the opposite end of the cylindrical shell. 

The situation is reminiscent of Rayleigh-Benard convection in isotropic fluids where stable roll attractors apparently compete with complex patterns, spiral defect turbulence [115-117], It has been shown very recently that if anisotropy is introduced into this system by inclining the convection cell, a normal roll pattern with dislocation defect turbulence occurs, which looks quite similar to patterns observed in EHC [118]. 

Cathodes are made from a paste of the cathodic active material with binders and electronically conductive additives, which are rolled onto metallic foils or exmets from nickel or aluminium. These cathodes are used as flat electrodes or in spirally wound form. The bobbin form realizes the same design in principle, but the layers of the active materials are much thicker, which in turn reduces the typical load to be applied to these bobbin cells. For fluid depolarizers the cathodic conductor often carries a mixture of carbon black with Teflon binder, which is impregnated with catalytically active substances. 

To maximize their high-rate performance and compensate for the lower conductivity of the organic electrolytes, designs are used for these lithium cells to increase electrode area, such as a larger-diameter coin cell instead of button cells, multiple parallel electrodes, or the spirally wound jelly-roll construction for the cylindrical cells. 

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