Patent Application
20160372727
The present technology relates to batteries and processes relating to batteries. More specifically, the present technology relates to processes and assemblies for improving uniformity in lead-acid batteries.
Lead-acid batteries are an inexpensive, reliable, and rechargeable storage medium for electric power. One area of continuing research is the materials used inside the battery. Most of them are exposed to the highly corrosive sulfuric acid that is used as the electrolyte in many lead-acid battery designs. The materials used in the positive and negative electrode assemblies, as well as the separator, are expected to maintain their structural integrity for years in this corrosive environment. They are also expected to be inexpensive and lightweight to keep the production costs down and energy-to-weight ratio up.
Uniformity within the battery assembly can have drastic effects on the performance and life cycle of a battery. Physical differences between components within the battery can cause performance effects that may produce weaknesses in components, and can eventually lead to defects and failure of the battery.
Thus, there is a need for improved systems and methods that can be used to produce more uniform battery components and batteries. These and other needs are addressed by the present technology.
Exemplary methods, processes, and assemblies are described relating to batteries. Methods of producing a battery may include positioning a first cell half including a first electrode within a battery casing. The first cell half may include a first electrode material and a first nonwoven material about or coupled with the first electrode. The method may also include positioning a second cell half including a second electrode within the battery casing proximate to and in contact with the first cell half. The second cell half may include a second electrode material and a second nonwoven material about or coupled with the second electrode.
The first nonwoven material may include two nonwoven sections located on opposing sides of the first electrode in embodiments, and in one embodiment the first nonwoven material and the second nonwoven material may be a similar material and may be of the same thickness. The method may specifically not include positioning a discrete separator between the first cell half and the second cell half in embodiments. Additionally, the first electrode material and the second electrode material may include a lead material or a lead oxide material. The nonwoven material may include glass microfibers characterized by a nominal diameter less than 5 μm, and the thickness of the nonwoven material or bi-functional mats may be between about 10 mils and about 150 mils under 10 kPa pressure.
In disclosed embodiments, the first nonwoven material and second nonwoven material or bi-functional mats may each effectively include or be configured to operate as both a battery pasting paper and at least a portion of a battery separator, where the materials each include a continuous material from a first surface of the nonwoven in contact with the respective electrode to an exterior surface opposite the first surface. The method may also include saturating the first cell half and second cell half with an electrolyte material, and the battery produced may include an absorbed glass mat lead-acid battery.
The present technology also includes processes of manufacturing batteries that may include disposing an electrode grid on a first section of nonwoven material, and applying an active material on the electrode grid. The processes may also include disposing a second section of nonwoven material on the active material to form a composite, and may include compressing the composite to incorporate the active material within the first and second sections of nonwoven material. The first and second sections of nonwoven material may be in embodiments two separate nonwoven mats, and may also be two portions of a single mat, which may be extended about the grid and active material like an envelope. The active material may be incorporated into each of the nonwoven materials to a similar depth less than the full thickness of the nonwoven materials in embodiments as well. An electrode plate may be formed from the composite, and then the plate may be incorporated into a battery.
In embodiments the process may not include an operation of flash drying the composite before the electrode plate is formed. The active material may be incorporated to a depth of less than half the thickness of each of the nonwoven sections of material in embodiments, each section of nonwoven material may include a continuous material including glass fibers. Each section of nonwoven material may also be characterized by a thickness of greater than 20 mils in embodiments and may be of a variety of dimensions useful in a battery.
The present technology also includes lead-acid batteries that may include a first electrode, a second electrode, and two bi-functional mats. A first surface of each bi-functional mat may be in contact with the first or second electrode, and a second surface opposite the first surface of each bi-functional mat may be in contact with the other bi-functional mat. The batteries may also include an active material incorporated within each bi-functional mat and in contact with the first or second electrode. In embodiments the active material may not fully extend through either bi-functional mat to contact the other bi-functional mat, and each bi-functional mat may include a nonwoven glass fiber mat. In disclosed embodiments, each bi-functional mat may be characterized by a thickness greater than about 10 mils.
Such technology may provide numerous benefits over conventional systems and techniques. For example, production costs may be reduced because certain process steps including flash drying may be avoided. An additional advantage is that improved uniformity of the internal components can create a more consistent operation and may thereby extend the life of the battery. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.
A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.
Certain figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be as such.
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.
The present technology includes assemblies, structures, and methods related to improving uniformity of components used in batteries. Absorbent glass mat (AGM) lead-acid batteries are a popular type of lead-acid battery because they can be much safer than flooded batteries, and are essentially maintenance free. While typical flooded lead-acid batteries may need additional water to be added to the cells due to evaporation, AGM batteries operate in a closed system in which the glass mat in the cell is saturated with electrolyte, e.g. sulfuric acid, and allows reduction/elimination of evaporation due to a closed system. These batteries can also be advantageous because the saturated mat can prevent the electrolyte from stratifying during discharge, which can cause increased erosion of the associated electrode areas through focused current flow.
Because AGM batteries are typically sealed after they are produced, and due to the corrosive materials used in the batteries, components within the battery cannot easily be replaced when they fail. Component failure can occur for any number of reasons including by defects produced by disuniformity of components. When components within a battery are not uniform, electrolyte flow and distribution may not be even, and this can cause a host of problems within a battery. For example, uneven electrolyte flow can cause uneven currents to flow through the battery and across the electrodes. Uneven currents can cause uneven use of the electrode surfaces, which can produce crystallization on the active material from overuse.
Crystals formed on the active material may produce shapes including needles that can penetrate a cell separator, for example, which can cause battery shorting. Additionally, resistance differences across a mat surface or between dissimilar materials may produce areas characterized by lower resistance. An area of lower resistance can produce higher currents and higher temperatures within the battery, which can further weaken materials. Accordingly, inconsistencies in materials used in AGM batteries can produce less uniform operation, which can eventually lead to battery failure.
One type of disuniformity includes differences between pasting papers and separators. Such an issue can be explained with reference to
To prevent short-circuiting of the cell, such as by shedding of the active material, a separator 120 is typically placed between the two electrodes 106, 116 to prevent physical contact between the electrodes, while allowing ionic transport to occur across it. A variety of properties of the separator may be adjusted to optimize battery performance, including, for example, thickness, porosity, pore size, resistivity, tensile strength, and weight, among many others.
Moreover, the active material is often coupled with the grid via a pasting paper that helps to maintain the active material associated evenly with the electrode, and limit, for example, sagging within the battery. Such a production is also described below with reference to
For example, the pasting paper used in such batteries is often relatively thin, such as from about 4-9 mils (0.004 to 0.009 inches). The separator, on the other hand, may be much thicker, such as from 40-90 mils, or roughly five to ten times as thick as the pasting paper. Accordingly, even when the two components are made based on similar standards, such as porosity greater than 90% or a particular density, for example, there is a high likelihood if not an assurance of at least minute differences between the two components based simply on the much different thicknesses. Also, fibers with different size distribution or glass chemistry may be used for making the pasting paper and/or separator, or the separator and pasting paper may be supplied by different suppliers, using different raw materials and processes, which may further exacerbate these issues. These physical differences, including, for example, density, pore size, and distribution, will still cause differences in electrolyte distribution across the cell, which may still produce uneven currents on the electrodes, eventually producing issues such as those previously described. The present technology overcomes the even minute physical differences between the pasting paper and separator by combining the two into a single bi-functional mat associated with each electrode. This bi-functional component is explained in more detail below with regard to
Similarly, negative electrode 212 may include a negative active material 214, which may include lead, which may be pasted, applied, coupled with, or associated with negative electrode grid 216. When the two electrodes 202, 212 are coupled and operated as a battery cell, an electrolyte (not shown) may allow a chemical reaction to occur at each electrode to generate energy for use from the battery. In conventional battery designs, in order to prevent short-circuiting of the cell, a separator material 220 is included between the two electrodes to prevent physical contact between the electrodes. However, as discussed above, such a separator material may affect the electrolyte flow, and uniformity of convection between the electrodes, which may affect the current and wear of the electrodes.
Additionally, as noted above, in order to prevent the active material from sagging, or flowing within the cell, additional reinforcements may be provided against the electrode grid to maintain a uniform contact and distribution of the active material 204, 214. For example, a mat of non-reactive material may be saturated with or include the active material and be coupled with the electrode grids. As mentioned previously, the mat is often termed “pasting paper,” regardless of the actual composition, which may include a variety of materials. The present technology, however, avoids the inconsistencies between the pasting paper and the separator by combining the two materials into a single mat design on at least one side of each electrode.
As illustrated in the Figure, bi-functional mat 220B extends from electrode grid 206 past active material 204 on that side of the grid, and up to location 221 where it joins mat 220A of negative electrode 212. Bi-functional mat 220A similarly extends from negative electrode grid 216 past active material 214 to point 221 where it meets mat 220B. Additionally, based on the pore diameter, the amount of penetration of active material may be minimal or virtually not occur. In this case, for example, bi-functional mat 220A extends up to active material 214 about grid 212, without penetration or with minimal penetration into the material of the bi-functional mat. As such, the cell may include at least two bi-functional mats, with a first surface of each mat being in contact with the first or second electrode or electrode grid, and a second surface opposite the first surface of each mat being in contact with the other bi-functional mat. On the other sides of the two electrodes may be a similar bi-functional mat, or a mat of a different thickness including a reduced thickness from the bi-functional mats. Hence, disclosed embodiments include bi-functional mats incorporated in the cell between the two electrodes, with alternative material on the outside of each electrode, as well as bi-functional mats on each side of each electrode.
As will be described further below with respect to
The bi-functional mats may include a variety of material designs, but may be of a continuous design from the electrode surface to which it is contacted across the entire mat, which may extend to a mid-point or central location of the cell between the two electrodes. It is to be understood that characteristics described may be average characteristics across the mat. Although a certain range of variation may be included within each bi-functional mat, the mats may include a continuous configuration of materials across the thickness of the mat. Mats 220A, 220B may be identical in formulation and characteristics, and may maintain such characteristics across the entire surface of each mat. For example, the mats may be of constant density, porosity, pore size, composition, and any of a number of other physical characteristics. In this way, the mats may promote a fully uniform electrolyte flow and distribution in contrast to conventional cells. As previously noted, even conventional cells in which the pasting paper and separator are designed with similar processes and designed to have similar characteristics, because of the significant difference in thickness between the paper and separator, there would still be minute but appreciable differences between the two mats. In the present design, however, there may be identical characteristics across the entirety of the bi-functional mat because the mat is a uniform design constructed as a single piece of material. This may promote uniform electrolyte flow, and therefore uniform current distribution and operation across the cell, which may provide uniform wear and associated improved life and/or operation of the battery.
Because each bi-functional mat 220A, 220B, which includes the active material, effectively includes a portion of the separator as well, the mats may be of a greater thickness than conventional pasting paper. As opposed to being of a thickness less than about 10 mils, the described bi-functional mats may include the thickness of the pasting paper and up to half or more of the thickness of the separator. Accordingly, the bi-functional mats may be characterized by a thickness greater than about 10 mils in disclosed embodiments, and may include a thickness greater than or about 15 mils, 20 mils, 30 mils, 40 mils, 50 mils, etc. or more, and may also include a thickness less than or about 150 mils, 130 mils, 115 mils, 100 mils, 90 mils, 80 mils, etc. or less.
The bi-functional mats may include a variety of materials, and in disclosed embodiments may include glass fibers, and may for example be nonwoven mats including glass fibers. The mat may be of a variety of thicknesses as discussed above, typically greater than or at least about 10-20 mils based on the fibers used and various characteristics of the incorporated material. The mat thickness may also be a function of the pressure under which it is formed or held within a battery, such as under a compressive force of, for example, 10 kPa. The area weight of the glass mat in the separator 220 generally ranges from 100 and 400 g/m2, such as, for example, 150 and 300 g/m2. The binder content (LOI) may be in a range of values to provide additional effects on the mat thickness, for example. In embodiments, the binder content may be below about 0.5% up to about 5% or greater, or any value in between. Additionally, the binder content may be less than or about 5% up to 35% or higher, as well as values in between.
The bi-functional mat used in the cells may be sufficiently electrically insulating to prevent significant electron conductance between the positive and negative electrode assemblies 202 and 212. Electrical resistivity on the order of about 1 MΩ per square or more is usually sufficient. While the bi-functional mats 220 are electrically insulating, it should also be conductive to the ions in the electrolyte, such as SO42− ions that may form the complementary ionic current to the electric current traveling between the positive and negative electrode assemblies 202 and 212. The bi-functional glass mat used may be porous to permit this ionic migration, and can have a porosity of 50% to 99%, and in embodiments are characterized by a porosity of greater than 90%. Additionally, the bi-functional mat may have an absorption height of at least 5 cm, at least 10 cm, or more after exposure to 40 wt. % sulfuric acid for 10 minutes conducted according to the ISO 8787 standard. In exemplary bi-functional mats 220, the average pore diameter of the ion channels formed in the separator 220 can range from 5 μm or less to 100 μm or more. Additionally, the bi-functional mat may include or be characterized by any material characteristic of standard AGM separators. This includes, but is not limited to compressibility, electrical resistivity, pore characteristics, surface area, tensile elongation and strength, porosity, etc. By maintaining some or certain characteristics similar to more conventional separators, the present bi-functional mats may be used in a wide variety of battery applications and designs.
In some examples, the glass-fiber mats may be blended with non-glass fibers, such as fibers made from organic polymers and fibers made from graphite, among others. Exemplary organic polymer fibers may include polyolefin fibers and polyester fibers, among others including other synthetic fibers. Specific examples include polyethylene terephthalate (PET) fibers, polybutylene terephthalate (PBT) fibers, polyethylene (PE) fibers, polypropylene (PP) fibers, and poly(p-phenylene sulfide) (PPS) fibers, among others. Fibers made from these materials have comparable electrical conductivity to glass fibers. Additionally, the bi-functional mats may include additives and additional materials to affect particular characteristics of design.
Battery design may include a number of electrode plates per cell, and may include a number or plurality of cells in the entire battery casing. Depending on the location of the electrode plate or cell, each mat utilized per electrode plate may be bi-functional mats. For example, interior plates in a battery may not require additional reinforcement means such as mats or separators. Accordingly, for such interior plates all mats surrounding the electrodes may include bi-functional mats of the present technology. For example, reviewing
Reinforcement mat 230, or additional bi-functional mat 230, may or may not be impregnated or saturated with the negative active material 214 so that the reinforcement mat 230 is partially or fully disposed within the active material 214 layer. Impregnation or saturation of the active material within the reinforcement mat means that the active material penetrates at least partially into the mat. For example, reinforcement mat 230 may be fully impregnated with the negative active material 214 so that reinforcement mat 230 is fully buried within the negative active material 214, i.e., fully buried within the lead paste. Fully burying the reinforcement mat 230 within the negative active material 214 means that the mat is entirely disposed within the negative active material 214.
In examples, each of the reinforcement mats 230, 240, which may be bi-functional mats in embodiments or in specific locations in the cell as explained above, as well as bi-functional mats 220A, 220B may be disposed within the active material 204, 214 up to about a depth “X” of about 20 mils from an outer surface of the electrodes 202, 212. In other examples, the bi-functional mats 220A, 220B, 230, 240 may rest atop the active material 204, 214 so that the mat is impregnated with very little active material or virtually none at all. Accordingly, in disclosed embodiments, the active material may be incorporated from a depth of 0 (or no incorporation) up to the full depth of the mat, or any range in between.
Referring now to
The resulting electrode assembly 450 may subsequently be cut or slit to length via a plate cutter (not shown). As described previously, the active material 430 may be applied to the grid 410 and/or top and bottom of reinforcement mats formed from rolls 440 and 420, so that the active material impregnates or saturates the mats to a desired degree. By controlling certain of the paste characteristics including density, flow characteristics, etc., the degree to which the paste is incorporated or impregnated into the bi-functional mat can be controlled.
The mixing, adding, and/or drying or curing operations performed by manufacturing system 400 may be continuous processes instead of batch or semi-batch processes. When run as continuous processes, the manufacturing system 400 may be run continuously, for a faster throughput and more cost effective operation. As explained previously, for an end plate within a battery, only a single bi-functional mat may be used, and either roll 420 or 440 may include a reinforcement mat that is utilized to add additional structural integrity to the battery cells on the side of the plate that is proximate the battery casing.
In conventional battery designs, one or more of the nonwoven materials may include a pasting paper that is to be fully saturated with the active material. Because bleeding of the active material occurs, a flash drying operation is often performed so that the slit plates do not stick to one another to form a block when stacked after cutting. However, by utilizing the bi-functional mat or the present technology that does not impregnate the active material through the entire thickness of the mat, the flash drying operation may be avoided or completely removed from the process. Accordingly, a faster and more cost effective process for making the electrode assemblies may be afforded by the present technology.
Referring now to
The method may also include positioning a second cell half including a second electrode within the battery at operation 504. The second cell half may be positioned within the battery casing proximate to and in contact with the first cell half. As illustrated in an exemplary configuration in
The nonwoven materials or bi-functional mats may include similar materials, and may be identical, substantially similar, or relatively similar to one another. For example, the nonwoven materials may be of the same thickness, density, porosity, pore size, etc. among other physical characteristics. Because the two cell halves include the bi-functional mats, the method may specifically not include positioning a discrete separator between the first cell half and the second cell half. Conventional battery designs include placing a separator in between the first electrode plate and the second electrode plate in order to prevent material contact between the electrodes. However, the present designs effectively divide the separator between the two bi-functional mats, and thus obviate the need for a discrete separator. In this way, the present technology can produce batteries more efficiently by reducing the number of discrete parts included in each battery, which can reduce costs and increase overall manufacturing speed.
Within the cell halves, the first electrode material and the second electrode material may include a lead material or a lead oxide material. The nonwoven materials may include glass microfibers or any of the compositions previously described, and microfibers used may be characterized by a nominal diameter less than 5 μm. The thickness of either or both nonwoven materials or bi-functional mats may be between about 10 mils and about 150 mils under 10 kPa pressure. As previously described, the bi-functional mats, or the first nonwoven and second nonwoven materials may each effectively include the material used for both the battery pasting paper and at least a portion of the battery separator. However, unlike the separate components of conventional designs, in the present technology the mats each may be a continuous material across the bi-functional mat and include an average uniform composition, within a certain range for each characteristic of the mat, for the bi-functional mat material from a first surface of the nonwoven or bi-functional mat in contact with the respective electrode to an exterior surface opposite the first surface of each mat.
Method 500 may also include saturating at least a portion of the first cell half and the second cell half with an electrolyte material at optional operation 506, also known as “acid filling,” which may be performed under pressure. The electrolyte may be any material known or developed and capable of functioning in a lead-acid-style battery. The electrolyte may include sulfuric acid, for example, and may be in various forms including a liquid or gel. Further operations may be performed including electrically coupling multiple cells together, reinforcing, packaging, and sealing the battery at optional operation 508. The cells may be incorporated in a variety of ways, and in one non-limiting example, multiple plate sets, with each set including a positive and a negative plate, may be utilized to form a cell. Moreover, multiple cells may be included and electrically coupled within a casing to form a battery. The battery produced may be any type of battery that may benefit from the bi-functional mat of the present technology, and may include an absorbed glass mat, lead-acid battery in embodiments.
The composite may be compressed at operation 608 to produce a particular density or configuration of the composite, as well as to incorporate the active material into each of the nonwoven materials to a similar depth less than the full thickness of the nonwoven materials. An electrode plate may be formed from the composite at operation 610, which may include cutting a length of composite material to the dimension utilized for the battery. In a continuous operation, for example, plates may be cut from the composite as they travel down a manufacturing line. The plate may then be incorporated within a battery at operation 612 as part of a process to form the battery. Incorporation of the plates may include interior plates that include bi-functional mats on either side of the electrode assembly as well as end plates that may include at least one reinforcement mat on at least one side of the electrode to be proximate the battery casing.
Additional plates may be included such as previously described, and may be included as component halves of a cell that does not require a separator to be disposed between the electrode plate sections. The method may not include a flash drying operation before the electrode plate is formed because bleed through of the active material may be prevented based on active material being incorporated to a depth less than the total thickness of the bi-functional mat. For example, the active material may be incorporated to a depth of less than half the thickness of one or each of the nonwoven sections of material in embodiments. In additional embodiments, drying, curing, or other operations may be included for a variety of purposes.
One or each section of nonwoven material may include a continuous material including glass fibers such as previously described, and one or each section of the nonwoven material or bi-functional mat may be characterized by a thickness of greater than about 20 mils. In embodiments the thickness may be within any of the ranges previously described throughout the application. These processes and configurations may have several advantages over conventional designs including improved and more uniform current flow through the cell due to uniformity of the material in the bi-functional mats. Additionally, a variety of process steps may be obviated by the present technology in that flash drying and inclusion of discrete separators may not be used in batteries according to the present technology.
In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.
Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology.
Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.
As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “an electrode” includes a plurality of such electrodes, and reference to “the layer” includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth.
Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.
