A battery separator comprising at least three of the following improvements, features, changes, modifications, enhancements, performance, characteristics, profiles, shapes, configurations, structures, parts, attributes, spacing, thicknesses, ratios, blends, mixtures, formulations, additives, agents, coatings, layers, laminates, mats, non-wovens, surfaces, inclusions, effects, embodiments, or examples:
- 5) Charge Acceptance/Power Delivery—features of or changes to the separator to help increase charge acceptance/power delivery:
- a. Low or Lower Electrical Resistance (ER)—minimization of separator ER, via the following methods:
- i. Lower Back-Web (BW) Thickness—reduce the BW thickness from typical values which range from 150 to 250 micron by lowering the BW thickness between 75 to 150 microns and then reinforcing the transversal stiffness with the use of negative cross ribs,
- ii. Increase Silica to Polymer Ratio—increase the loading of silica, relative to the polymer content, have a silica to polymer ratio from about 3.0/1.0 to 5.0/1.0,
- iii. Utilize High Oil Absorption (High Surface Area) Silica (Increase Porosity)—include a silica with a high surface area (e.g. >200 g/m2), which typically yields a high oil absorption, an amount of pore forming agent from about 70 to 80% by weight in the extrusion process,
- b. Minimize Gas Entrapment—reduce opportunity for gas entrapment:
- i. Laminate Structure and Modifications—modified laminate structure to reduce gas entrapment,
- 1. Treatment of the laminate with a chemical or plasma to modify surface energy to shed gas bubbles,
- 2. Perforation to allow bubbles an area to coagulate and escape the laminate matrix,
- 3. Addition of nucleating agents,
- 4. Changing the structure of the laminate during formation,
- 5. Addition of polymer fibers and/or shaped polymer fibers to the laminate structure,
- 6. Addition of wetting agents (or surfactants),
- 7. Change the orientation on the fiber structure of the laminate so gas bubbles are less likely to attach to the structure,
- 8. Minimize the thickness of the structure so that there are simply less sites for bubble adhesion,
- ii. Wetting Agent Selection—use a more hydrophobic wetting agent, use an ethoxylated fatty alcohol,
- iii. Separator Cross-Ribs (Negative and/or Positive)—have small negative cross ribs to assist in the nucleation or transport of gas bubbles or to allow the gas to escape from between the plates, or reducing the potential for gas entrapment,
- iv. Nucleation of Gas—have areas on the separator to act as nucleation sites for gas bubbles to quickly and efficiently grow to the point where they are released from the separator and travel out of the area between the plates,
- 1. Profile Shape (Roughness)—add nanostructures on the surface of the separator to increase gas nucleation, such nanostructures may take the form of pyramids, chevrons, or pillars, and may be formed by calendaring, laser ablation or controlled chemical oxidation,
- 2. Additives—have additives incorporated into the matrix of the separator (or on the surface) in order to provide areas on the surface where they change the surface structure or energy to encourage the nucleation of small gas bubbles generated to a critical volume, the additives may be carbon fibers, carbon nanotubes, or barium sulfate,
- 6) Hydration Shorts (Hinder, Delay, Reduce, Eliminate)—add sodium sulfate to the electrolyte to hinder hydration shorts, or
- a. Common Ion Effect—have sodium sulfate incorporated into the separator matrix and/or laminate materials (such as by impregnation),
- b. Heavy Metal Sequestration—sequester lead ions that are in solution by incorporating apatite, hydroxyapatite minerals, ground fish meal, zeolites, lignins, latex, or rubber-derivatives into the separator (or on the separator surface, in the laminate material, in the electrolyte, in the battery casing, and/or the like) to inhibit hydration short formation,
- c. Location of Additives—have additives in the matrix of the separator (preferably as a substitution filler for part of the silica), coated on the separator, coated on or contained in the laminate structure, coated onto the container of the battery case either before or after the injection molding process, or placed in porous bags or sachets in the electrolyte or laminate structure,
- d. Lower or Reduced Acid Displacement—via separator modifications including:
- i. Thin Backweb—lower the backweb (BW) thickness with added cross ribs (preferably negative cross ribs as discussed above), higher porosity, or less rib mass of the separator,
- ii. Serrated/Battlement Ribs—use serrated or battlement rib design to remove mass from the ribs,
- 7) Improve Cycle Life—by modifying the separator as follows:
- a. Laminate Structure—utilize a laminate to retain the positive active mass in the positive grid,
- i. Glass Mat—utilize glass mats having different fiber lengths and widths in the mats ranging in compressed thickness from 0.1 mm to 1.0 mm,
- ii. Synthetic Nonwovens—utilize nonwoven polymeric mats, polyester mats,
- iii. Hybrid—utilize a hybrid mat of glass fibers mixed with polymer fibers,
- b. Profile Selection—contribute to lower acid displacement by profile design selection, use a profile having tight rib spacing with shorter rib height, narrower ribs, or battlement ribs,
- c. Polyaspartic Acid—add polyaspartic acid directly to the matrix of the separator, or as coated on the separator, coated on or contained in the laminate structure, coated onto the container of the battery case either before or after the injection molding process, placed in porous bags or sachets in the electrolyte or laminate structure,
- d. Compression—use a compressible, flexible or resilient rib structure to enhance cycle life, such as an I-beam rib profile,
- 8) Acid Stratification—overcharge the battery to some degree promote the electrolysis of water, or
- a. Profile Selection—incorporate horizontal ribs across the surface of the separator,
- b. Laminate Structure—add a laminate structure attached to the polyethylene separator, align the fibers in a certain pattern across and through the material, add a laminate structure to both the positive and negative face of the polyethylene separator,
- c. Surface Area—increase the surface area of the separator structure, decrease the fiber diameter of the laminate structure, or increase the internal surface of the separator by the type or concentration of silica, adding porosity, having cross ribs,
- d. Acid Immobilization—immobilize the acid by having cross ribs which tend to hold the acid in place, adding a silica layer on the laminate and/or separator surface or adding silica in the laminate to “gel” the acid, or utilizing Daramic AJS technology,
- e. Polyethylene/Absorptive Glass Mat Hybrid—incorporate a flat PE separator membrane into or on one side of an AGM separator, and
- f. Other Laminate Hybrids—utilize other laminate systems, whether nonwovens or other glass mats in conjunction with a flat PE separator membrane to make an acceptable separator.