JP2002523880A - Lead-acid separator and cells and batteries using such a separator - Google Patents

Abstract

(57) Abstract: There is provided a separator used in the production of sealed lead-acid battery cells and batteries, which can enhance the performance of such cells and batteries. SOLUTION: The performance of the sealed lead-acid battery cell and the battery in terms of service life is as follows: the load cell pressure in at least two months is at least about 6.0; The enhancement is achieved by using a separator having preselected properties that include a size of 15 μm or less and an average pore size of about 2.8 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to lead-acid battery cells and batteries, and more particularly to separators used in the manufacture of such cells and batteries.

[0002]

[Prior art]

In various applications, often referred to as "industrial battery" applications, conventional flooded electrolyte lead-acid cells and batteries or sealed lead-acid cells and batteries are used. Sealed lead-acid battery cells and batteries are often VRLA
("Valve-regulated lead-ac
id) "cells and batteries. In stationary battery applications, lead-acid cells and batteries provide standby power in the event of a power outage. In such applications, such cells and batteries are typically kept fully charged and ready for use by floating charging at a constant, preset voltage. I have. Stationary batteries can be used for standby or operating power in a variety of applications including, for example, telecommunications, utilities, emergency lighting in commercial buildings, standby power for cable television systems, and power outages for computer backup power. Used for

[0003] Other applications in which lead-acid cells and batteries are used include cells in the range of first to third grade trucks, various autonomous vehicles, mining vehicles, and railway locomotive vehicles. Various power applications are included in which an array of provides power. The performance requirements for powered vehicles are significantly different from the performance requirements for stationary power sources. In stationary power applications, the discharge depth during use is relatively shallow,
The number of discharges is small. This is because many batteries are floatingly charged. In contrast, power applications require a continuous, relatively deep discharge over a period of time. Indeed, a general requirement for first to third grade trucks is that the cell or battery assembly must be able to deliver power at 80% discharge depth in eight hour increments, and such performance must be met. 1
300 cycles per year are required, which means that they have a useful service life of 4 or 5 years under these conditions.

[0004] Due to the drastic changes in requirements for many of these applications, the manufacture of lead-acid battery cells and batteries presents tremendous challenges and has created significant barriers. For this reason, most custom designs satisfy specific applications.

As a result, lead-acid battery cell / battery manufacturers have had to develop a series of cells and battery groups in an attempt to meet various electrical performance criteria. Such criteria varied, and in some cases required the connection of large cells in parallel, in series, or a combination of parallel and series to provide a satisfactory power / energy source.

Further, in some cases, space requirements are very strict, and dimensional requirements are strictly defined. Many types of steel trays and the like are used to accommodate the necessary cells.

To obtain a series of cells and battery groups, grids of various sizes are needed to meet the capacity and other electrical performance requirements for individual cells for a particular application It is said. One method used for VRLA cells is to maintain the essentially constant width but individual height and number of plates used in a particular cell to meet the requirements of capacity and other electrical performance. To provide a different set of grids. While this is a valid solution, it does not take the steps that must be taken, as discussed above.

The internal configuration of such a VRLA cell can be varied in various ways. Generally, such cells are disclosed in U.S. Pat.
No. 62,861. Thus, as is well known, such cells use highly absorbent separators, with the necessary electrolyte absorbed into the separators and plates. Such cells are typically sealed from the atmosphere by a valve designed to regulate the internal pressure within the cell, providing a condition called an effective "oxygen recombination cycle" (hence the "sealing" The terms "performed" and "valve-regulated" and "recombination" are used).

[0009] Recombination battery separator materials (sometimes referred to as "RBSMs (Reco
mbinant battery separator materials)
) Were conventionally made of highly absorbent glass fiber mats.
This type of separator has adequate absorption to hold the desired amount of electrolyte and has pores that can facilitate the oxygen recombination cycle. A variety of suitable glass fiber mats are commercially available and are used in VRLA cells and batteries.

[0010] Despite the widespread use of such glass fiber mats, many efforts have been made to develop other recombination battery separator materials that are believed to satisfy various purposes. US Patent No. 4,9, issued to Badger
08,282 describes many different attempts in the prior art to provide satisfactory separator materials for recombination cells and batteries. Nevertheless, the badger passes through these voids when saturated with electrolyte, leaving unfilled voids, and the separator cannot hold enough electrolyte to fill all the voids. It is stated that separators in which gas is transferred from one plate to another have not heretofore been proposed (see the second column, lines 20-26).

More specifically, Badger discloses a separator comprising two types of fibers in its entirety. The first fiber set has a separator absorbency of 90% or more for the electrolyte, and the second fiber set has a different absorbency for the electrolyte of 80% or less. First
And the second fiber is disclosed as being present in a proportion such that the overall separator absorbency is between 75% and 95%. In particular, a separator made of a mixture of two different grades of glass fiber, one grade of chopped glass strands and a particular grade of polyethylene fiber is disclosed.

Another prior art attempt to provide an RBSM is US Pat. No. 4,216,280 to Kono et al. U.S. Pat. No. 4,216,280 discloses a separator comprising glass fibers entangled in sheet form without the use of a binder and having first and second glass fiber portions. The first part is
The second portion is made of glass fiber having a fiber diameter of 1 μm or less, and the second portion uses a glass fiber having a fiber diameter of 5 μm or more and an average fiber length of at least 5 mm. It is stated that such separators retain electrolytes to a high degree, have good mechanical strength, and have good shape recovery properties.

[0013] Yet another prior art attempt to provide an RBSM is US Patent No. 4,367,271 to Hasegawa et al. Thus, US Pat. No. 4,367,
No. 271, "Prior Art" describes one prior art proposal which includes glass fibers mixed with a synthetic resin which serves as a binder, but another type proposed proposes that glass fibers be made of synthetic resin. Mixing with a monofilament fiber is included. Hasegawa et al. State that such prior art methods are inadequate due to a significant reduction in liquid absorbency and little improvement in mechanical strength. U.S. Pat. No. 4,367,271 states that it provides a separator with high liquid absorption, high strength and easy handling. According to U.S. Pat. No. 4,367,271, such a separator material is composed of about 10% by weight or less of fibril-shaped synthetic fibers having a "freeness" of 350 cc or less. It is manufactured by a process using a glass fiber having a specific area of 1 m ² / g or more.

[0014] Despite this prior art effort in this field, separator materials are still available that can solve the major problems that arise during the service life of VRLA cells and batteries, especially when the required service life is relatively long. is needed. Firstly, as mentioned above, the first solution in this field is a grid of constant width, but the height of the grid and the number of plates provide capacitance and other electrical performance requirements. To provide a series of cells and batteries that use a changing grid. In this type of cell, and in many cells that are relatively high in height, especially in industrial cells designed to have a relatively long service life, for example, on the order of 10 or 20 years, the "dryout ( dry out) "has become a major problem. Such "dryout" can occur due to loss of electrolyte, uneven cell saturation, RBSM exfoliation, or a combination thereof. Reasons for "dryout" include the lack of adequate elasticity of the RBSM and / or a difference in the degree of saturation from cell top to cell bottom. In addition, the stratification of the electrolyte causes various problems, such as sulfation of the cathode plate and uneven use of the plate from top to bottom.

[0015] Another problem that may be associated with cell dryout is that the cell loses its properly compressed state. More specifically, as is well known, providing a VRLA with satisfactory electrical performance requires close contact between the cell plate and the separator. Such contact is typically achieved by maintaining the separator in the cell at 20% (based on uncompressed thickness) or in an attempt to maintain satisfactory contact over the life of the cell. Provided by further compression.

Thus, as can be envisioned, and despite many prior attempts to provide improved RBSMs, there is a wide range of such materials for obtaining a satisfactory solution. It turns out that the understanding of how to combine the requirements is basically lacking. This is especially true for RBSMs with an expected service life of 10 years or more. Therefore, there is clearly a need for both an understanding of how to evaluate the relative efficiency of RBSM candidates and providing such materials that can improve the performance for the expected service life of VRLA cells and batteries. It has been.

[0017]

[Problems to be solved by the invention]

Accordingly, it is an object of the present invention to provide such cells and batteries that use a separator that can enhance the electrical performance of the sealed lead-acid battery cells and batteries.

[0018] Another and more important objective is to provide a separator for large VRLA cells and batteries that can increase the resistance to electrolyte stratification over its useful life.

Another object of the present invention is to provide such cells and batteries having separators with preselected separator resiliency to improve the service life performance of the sealed lead-acid battery cells and batteries. To provide.

It is another object of the present invention to provide such a sealed lead-acid battery cell and battery separator having enhanced mechanical strength to facilitate cell and battery assembly.

Yet another object of the present invention is to provide a test method useful in selecting a suitable separator material for VRLA cells and batteries.

[0022] Other objects and advantages of the invention will become apparent as the following description proceeds. Although the present invention will be described primarily with reference to use in a sealed lead-acid battery cell, it should be understood that the present invention may advantageously be used in any other application where a separator of the disclosed type is useful. is there.

[0023]

SUMMARY OF THE INVENTION The present invention generally relates to the use of separators having preselected properties and compositions to enhance the service life of sealed lead-acid storage cells and batteries. Expected based on the discovery that can be. More specifically, it has been found that combining certain properties in a certain manner provides a separator material that provides VRLA cells and batteries with improved performance for expected service life. Thus, an excellent separator material is obtained when such a material combines preselected porosity, pore size and basis weight with preselected resiliency, saturation and stratification properties. I know that.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows an exemplary lead-acid battery cell according to the present invention. The cell 1 has a container or housing 12 containing a plurality of anode plates 14 and cathode plates 16, respectively. As shown, the cell includes a plurality of anode and cathode plates. Of course, the cell can use as many plates as needed to provide the desired capacity and other electrical performance characteristics for a particular application.

According to the present invention, the plates 14, 16 are separated by an absorber separator 18 having preselected properties as discussed below. In a preferred embodiment, the separator extends slightly beyond the electrodes to prevent the cells from accidentally shorting. In addition, the separator is folded around the plates and placed between the plates by using a U-shaped fold 20, as shown in FIG.

The plates 14, 16 preferably fit snugly within the container 12.
That is, the electrodes and separator must remain assembled even if the container is inverted. Indeed, as is well known, the cell configuration ensures that the plate and separator are properly compressed and in good contact. This is to improve the electrical performance of the cell. Preferably, as shown in FIG. 1, the separator and the plate are compressed so that they are in intimate contact with each other. Suitably, the thickness of the separator in the cell is typically at least about 20% to 25% of the uncompressed thickness.
By setting it to about%, it can be compressed appropriately. The plates are connected to each other by conductive straps 22 and to external terminals 24, 26 by conventional means.

The thickness of the plate will vary depending on the intended use of the cell. One example of a useful range is from about 0.050 inch to about 0.300 inch (about 1.27 mm to about 7.62 mm) or more.

Preferably, the container is typically sealed from the environment of use to provide a known and efficient oxygen recombination cycle. The container used must be able to withstand the pressure of the gas released during charging of the cell. The pressure inside the container is
For example, 3.447 kPa to 68.947 kPa (0.5 psig to 10 ps)
ig) gauge pressure level is reached. Discharge ventilation is provided by a low pressure self-resealing relief valve, such as valve 28. An example of such a valve is described in U.S. Pat. No. 4,401,730.

The container 12 also contains an electrolyte. Preferably, the electrolyte is absorbed in a separator of the anodic and cathodic active materials. The electrolyte is typically sulfuric acid, having a specific gravity in the range of about 1.270 to about 1.340, by way of example, or having a higher specific gravity deemed appropriate for the particular application.

The size of the plates can be varied depending on the electrical requirements of the performance required for the cell. For example, the size of the anode plate is typically sized from 58 amp-hours (AH) to 98 AH, 108 AH, 188 AH, and more.

In an exemplary embodiment, the height of the cell may be greater than 28 inches (71.12 cm). Indeed, the separator that the cell requires for many applications is about 1.016 mm to about 3.429 mm (about 0.04 inch to about 0.135 inch) thick and 71.12 cm ( 28 inches), and in some cases more.

It will be appreciated that the use of the preselected separator of the present invention allows the internal configuration of the sealed lead-acid battery and battery to be varied as desired. Various types of sealed lead-acid battery cells and batteries are well known and in use.

According to the present invention, it has been found that certain properties and performance of the separator need to be pre-selected in order to provide high performance during the desired service life. The terms "pre-select" and "pre-select" are used when the specified properties of the separator are determined prior to assembly of the sealed cell and battery, and the separator material used in the cell is such a property. Is known to have Such knowledge can be obtained by testing by the manufacturer or user of the separator. Further, it will be appreciated that once the reproducibility of the process parameters has been ascertained, it is not necessary to retest the desired preselected properties.

One feature of the present invention is to provide a test technique that properly evaluates the elasticity of an RBSM so that performance can be enhanced over a service life with preselected elasticity. . More specifically, a load cell test was developed that continuously measures the decrease in elasticity over time and predicts the RBSM's ability to maintain compression within the cell over its useful life.

The load cell test used in the present invention measures the amount of pressure exerted on a load cell by a separator sample (appropriate electrolyte has been absorbed by the test sample at 95% saturation and initially compressed by 20%). measure. Create a graph of measured pressure against time. After a lapse of a predetermined time, the applied pressure becomes constant.

According to the present invention, useful separator materials have a load cell pressure at two months of at least about 6.0, preferably at least about 6.5 or 7.0, and sometimes higher, at least about 8. 0.

A test sample is prepared by cutting 3 inches × 3 inches (7.62 cm × 7.62 cm). The actual thickness of the test sample is determined at any of three points using a TMI gauge to measure the thickness of the recombination mat and the BCI test procedure (BCI Method 3-006-9). The sample is then weighed in milligrams (
W _sep ).

[0038] The amount of 1.31 sulfuric acid to achieve 95% saturation is determined as follows. (1) Determine the true density D _hp of the test sample using the helium pycnometer method. (2) Determine basis weight bw using recombination mat using BCI procedure (Method A)
). (3) Determine the density D _a of the material in the compressed state (ie, applied to the battery) by dividing the grammage by the sample thickness in the 20% compressed state. (4) A value (K) of 100% separation in a state of being compressed by 20% is obtained as follows.

[0039]

(Equation 1)

Here, D _acid is the specific gravity of the acid. (5) is then determined as follows amount W ₁ of acid to achieve saturation of 95%.

W ₁ = W _sep × K × 0.95 Then, the amount of acid W ₁ was added to the separator sample, and the sample was 0.0762 mm (0 mm).
. 003 inch) polyethylene film or bag, heat-sealing the edges together so that no excess air enters the sample and there is no void space. Any polyethylene film or bag can be used, but has a sufficiently low water vapor permeability
It is preferred to use a film or bag that reduces the electrolyte lost during the months of testing to less than 0.20% of the total weight of the electrolyte.

To test the prepared sample, place the sample in the center of the aluminum base plate of the fixture. A fixture (15.24 cm × 15.24 cm × 1) was placed on the test sample.
. Place a 27 cm (6 inch × 6 inch × 0.5 inch) polycarbonate slab). Next, load cells (LCAA-100 with LBC-014 button)
, Omega) on the top plate and balance the buttons on the top plate. The base of the load cell was then machined to 80% of the sample thickness for the sample, the spacer having 0.1016 mm (0.004 inch) for the thickness of the polycarbonate and the top plate of the fixture were in contact. Tighten up to

The data collected is a continuous plot of the pressure detected by the load cell button over time. The two month test time is the time selected to evaluate the sample,
If deemed appropriate, it may be shortened.

According to another feature of the invention, the properties of the separator used are such that the variance for at least one of the saturation properties and the stratification properties, preferably both, is less than 10%, more preferably about 10%. Must be preselected to be less than 2%.
Maintaining these properties is necessary for any VRLA cell or battery designed to function upright during use and requires a tall cell, ie, 2
Of particular importance for cells that require a separator having a height greater than 5.4 cm (10 inches).

To test for saturation and bedding properties, a 7.62 cm × 27.94 cm (3 inch × 11 inch) rectangle is cut out. The thickness of the selected coupon and the weight of the sample in milligrams are determined as done for the load cell sample. Similarly, use the protocol described for the load test, as was done with the load cell samples, and determine the number of grams of 1.31 sulfuric acid that needs to be added to achieve 95% saturation.

Next, after the required amount of electrolyte was added to the sample, the sample was re-encapsulated in a 0.0762 mm (0.003 inch) polyethylene film and heat sealed at the edges, as described above for the load cell sample. I do. The samples thus encapsulated are then stacked and placed in a saturation-stratification test fixture. The test fixture was 15.24 cm x 60
. Includes a 6 inch x 24 inch x 0.5 inch (about 96 cm x 1.27 cm) polycarbonate slab. One slab had 3.5 inches of silver / grooves laser cut every 2.54 cm (1 inch). The slab has holes for retaining mechanisms, ie nuts and bolts, 3/8 inch.
Are provided at equal intervals. The separator is aligned with the bottom slit of the slab provided with the slit. In particular, machined spacers have been added to the bolts as described above for the sample thickness. The other slab is then placed on the separator sample using guide bolts. The upper side of the fixture is then tightened to the spacer using a nut.

The setup is left for two months. After the standing time, the separator sample is cut into 2.54 cm x 7.62 cm (1 inch x 3 inch) pieces using the slits of the fixture as a guide. Each piece on the plastic is numbered sequentially.
Each piece is then weighed without damaging the numbered plastic sheath.
Each sample is then checked for specific gravity using a Reichert-Jung refractometer and the sample is placed in a beaker (250 ml beaker) with the corresponding number.
Based on this data, the relationship between the specific gravity of the acid and the cell height is determined, which determines the stratification.

To determine the respective degree of saturation, each plastic piece is wiped dry and weighed. By subtracting the weight of the plastic from the separator / sheath piece 2.54 cm × 7.62 cm (1 inches × 3 inches) can determine the wet weight W _w of the sample.
The specimen is then rinsed with deionized water using a simple permeation method. Then the pH of the bath
And about 4-5 times until the pH is above 4.5 (or the pH of the deionized water used). After infiltration, place sample in oven, remove from beaker,
Place on the marked aluminum weighing dish. The oven is maintained at 120 ° C. for 24 hours with no convection. The sample is then removed from the oven and placed in a desiccator until cooled. Then weighed sample in milligrams, to provide a dry sample weight W _d. If sample detachment occurs, this must be added to the dry weight.

The weight W _a of the acid of each sample is determined by subtracting the dry weight W _d of the separator sample from the wet weight W _w of the separator sample.

The quantity A in grams of acid is then calculated based on how much the separator sample holds when the saturation is 100%. This calculation uses the K determined as previously described, then, multiplied by the dry weight W _d of the separator samples.

A = K × W _d This calculation is performed for each separator piece.

[0052] Then, the actual acid W _a which is held in the sample divided by 100% saturated allowed weight A,
Calculate the saturation level of each separator piece by multiplying by 100.

Saturation% = W _a / A × 100 From this data, the saturation% with respect to the cell height can be determined. Although the sample height of the separator samples described in the test is 27.94 cm (11 inches), it should be understood that the sample height can be increased to the height required for a particular VRLA cell or battery. . In such a case, the saturation characteristics and the bedding characteristics
Preferably, it should be within the range described above.

In general, in this test procedure described above, there is no difference in specific gravity from top to bottom of the material. This same procedure is used for the separator material from the cell under test for proof and observe the changes in saturation as well as specific gravity.

One pre-selected set of separator properties of the separator properties is pore size properties. More specifically, according to the present invention, the average pore size is between about 1.0 μm and 2.2.
It changes in μm. Further, the maximum distribution pore size is preferably about 1.0 μm to 2.5 μm.
It changes in μm. The average pore size and maximum distribution pore size are determined using an automatic capillary flow porometer (Porous Material Model CFP1100AEX).
Suitable parameters are as follows: Pulse width = 1 second, maximum pressure = 68.9
47 kPa (10 PSI) and maximum flow = 20000 cc / m. The pore size distribution is determined by the commercially available P using the relationship of both dry and dry gas flow rates.
Calculated from pressure-pore size relationship by MI software. It has further been found that it is preferred to use a separator having a maximum pore size of 15 μm or less, more preferably about 14 μm or less, and even more preferably about 10 μm or less.

The pore size distribution can be used in predicting the RBSM's ability to prevent saturation differences from occurring. When the average pore size is 2.8 μm or more, even if the separator height is only 12.7 cm or 15.24 cm (5 inches or 6 inches), the difference in saturation tends to occur. Thus, it has been found that separators having such preferred average pore size and maximum pore size distribution characteristics improve in-use performance. Such improved performance is particularly evident for cells that have a relatively high aspect and are now being used in an upright position. However, such separators can be used even when they are used in a pancake shape, that is, in a state where the sides are positioned facing each other. Thus, these properties are believed to assist in providing a sufficient oxygen recombination cycle.

For many applications, the normalized basis weight (RBSM includes polymer fibers as discussed below) is at least preferably 150 g / m ² / mm or more, and from about 170 g / m ² / mm to 200 g / m ² / mm. Such a basis weight can be determined by the BCI technique mentioned above.

As will be appreciated, the higher the normalized basis weight, the more material is required. Therefore, the price of the separator increases. However, from the viewpoint of obtaining more preferable load cell characteristics, when a material having a relatively high basis weight is used,
It has been found that the load cell properties are enhanced as compared to materials having a lower normalized basis weight.

With regard to the porosity of the separator according to the present invention, it is necessary that the porosity be adequate to provide an appropriately sized electrolyte reservoir. Thus, porosity is a matter of design, and it is therefore preferred to use a separator having a porosity of at least about 90% or 91%, with a maximum of about 93%.

In view of providing a separator having the desired combination of preselected properties described hereinabove, the plastic fibers may be provided in an amount from about 5% to up to about 30%, based on the total weight of the separator. It has been found desirable to provide a glass fiber mat that preferably contains no more than about 12%. Such separators can be manufactured by well-known conventional processes by simply incorporating selected relative amounts and types of fibers into the slurry from which the separator is made. Indeed, the incorporation of selected levels of plastic fibers will provide a separator that is more consistent and reproducible in properties as compared to fibers containing only glass.

[0061] The plastic fiber used in the separator of the present invention is preferably a polyester fiber, and more preferably a polyethylene terephthalate fiber. Suitable amounts of such polyester fibers range from about 5% to about 12% based on the total weight of the separator. As a variation on the preferred polyester fiber, any other acid stable polymer can be used. Suitable fibers include polyolefins such as polyethylene and polypropylene. The addition of such polymer fibers increases the RBSM's elasticity as determined by improved load bearing. However, if the content of polymer fibers is too high (50% or more), the load bearing capacity will be reduced.

RBSM materials made from glass / polymer matrix have excellent load bearing / elasticity. However, these materials are hydrophobic, and hydrophobicity directly correlates with the percentage of polymer content. Due to their hydrophobicity, these materials can alleviate saturation problems by controlling the average pore size to 1.5 μm or less, where it is difficult to maintain the same saturation level well from top to bottom of the cell. But this is not the solution. If desired, such polymer fibers contained within the RBSM matrix may be treated by any known means to modify the surface of the polyester fiber to include aprotic polar groups such as SO2 and SiO2 and other aprotic polar groups. Convert to base. Such well-known surface treatments include transesterification, chemical vapor deposition, grafting, and / or chemical laser treatment. Any means that can modify the fiber surface to increase wettability to the sulfuric acid electrolyte can be used. Increasing the level of fine fibers in the glass / polymer material helps to increase the material's resistance to saturation and stratification issues.

As will be appreciated, the need for such surface treatments will depend on the service life requirements of the cell and the total content of plastic fibers. When saturating the cell after assembly and during formation to levels above about 90%, some hydrophobicity of the separator is desirable to assist the initial recombination cycle. This is especially important in floating applications. Separators that use only about 5% polyester do not require any treatment. The pancake cell design does not require any surface treatment of the plastic fiber, regardless of the content of the plastic fiber.

As is well known, many of the RBSMs currently in use consist of coarse and fine glass fibers mixed to make the surface area of such RBSMs on the order of about 1.2 m ² / g. Including combinations. For some applications, it is appropriate to increase the proportion of fine fibers up to 100%. Increasing the level of such fine fibers will maintain the cells evenly saturated from top to bottom and provide the preselected pore size requirements necessary to prevent stratification. To assist. This is important for electric vehicle (EV) and bicycle applications. 100
The average pore diameter of the% fine fiber RBSM is typically 1.5 μm or less. These materials generally have sufficient springback properties. However, the cost of these materials is three to four times that of standard grade RBSM.

According to another feature of the present invention, the performance of the separator of the present invention can be enhanced by adding a suitable level of silica. Such additions can be made either during or after formation of the separator. Preferably, the added S
iO2 levels range from about 5 to about 30 based on the weight of the RBSM.
The addition of SiO2 provides a "crosslinked" matrix, i.e., a "glue" effect between the glass and plastic fibers. Furthermore, SiO2
The ions preferentially dissolve the SiO2 into the glass fiber over time and under various temperature conditions. This preserves the strength and integrity of the glass fiber. However, it has been found that the inclusion of such silica not only increases the acid wettability, but also maintains the elasticity of the separator during use, whatever the mechanism. Furthermore, it has been found that the inclusion of silica enhances the ability of such separators to maintain saturation and prevents the electrolyte from stratifying from top to bottom of the cell. If desired, fillers other than silica can be used, in particular such fillers enhance wettability and / or maintain saturation and / or inhibit stratification and / or result. Fillers other than silica can be used to increase the elasticity of the separator. Of course, any such filler is V
It should not be significantly detrimental to the desired performance of the RLA cell.

Further, to improve the integrity and strength of the separator, the fibers in the separator can be combined into a coherent matrix using a coupling agent. Suitable coupling agents must be stable in the cell environment and must not be detrimental to cell performance.

Furthermore, especially in applications with a long service life, the RBS in the cell environment should be such that long term performance degradation due to separator degradation is prevented or at least minimized.
The stability and integrity of M are important. In such a cellular environment, over a long service life, glass fibers are superior to polymer fibers in terms of stability and integrity.

Thus, according to one aspect of the invention, a multilayer bifunctional separator is used.
For this purpose, a glass separator layer is positioned adjacent to the anode, a glass / polymer composite separator layer having the desired preselected properties is positioned adjacent to the glass fiber layer, and the desired porosity, elasticity , And saturation and bedding properties,
Protects polymer / additive from oxidative degradation.

The thickness of each of the layers can be varied as desired to meet the necessary properties deemed appropriate. In this regard, as an example, it is generally desirable that the composite separator layer occupy most of the thickness, up to about 70% of the total thickness.

Indeed, while such bifunctional separators provide the desired advantages, the separators used in VRLA cells can, if desired, include multiple layers of glass / polymer separators with preselected properties. Including. In addition, spatial features other than those described above can be used across the interface adjacent to the separator and anode, where the stability of the separator is most closely tested.

Thus, it can be seen that there is provided a new and improved separator that achieves the objects set forth above. Indeed, the present invention provides criteria and test methods, which are believed to allow the performance of the separator to be first predicted. Various additional modifications of the embodiments specifically illustrated and described herein will be apparent to those skilled in the art, especially in light of the teachings of the present invention. The present invention should not be construed as limited to the particular forms shown and described, but is described in the claims.

[Brief description of the drawings]

FIG. 1 is a perspective view of a lead storage battery cell of the present invention, with a portion of a cell housing removed to show internal components.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lead storage battery cell 12 Housing 14 Anode plate 16 Cathode plate 18 Separator 20 U-shaped folded body

──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 1110 Centre Point Curve, Mendota Heights, Minnesota 55118, United States of America F-term (Reference) HH05

Claims (17)

[Claims] 1. At least one cell having a positive electrode plate and a negative electrode plate, and an absorber separator between the positive electrode plate and the negative electrode plate,
The valve-regulated lead acid battery cell or battery wherein the separator is preselected to have a load cell pressure in at least two months of at least about 6.0. 2. The load cell pressure of claim 1, wherein the load cell pressure is at least about 6.5.
A cell or a battery according to claim 1. 3. The load cell pressure of claim 2, wherein said load cell pressure is at least about 7.0.
A cell or a battery according to claim 1. 4. The load cell of claim 3, wherein the load cell pressure is at least about 8.0.
A cell or a battery according to claim 1. 5. At least one cell having a positive electrode plate and a negative electrode plate, and an absorber separator between the positive electrode plate and the negative electrode plate,
A valve-adjustable lead-acid battery cell or battery wherein the separator is preselected to have a change in at least one of saturation and stratification properties of about 10% or less. 6. The cell or battery of claim 5, wherein the change in both the saturation properties and the stratification properties is about 10% or less. 7. The cell or battery of claim 5, wherein the change is less than about 5%. 8. The cell or battery of claim 7, wherein the change in both the saturation properties and the stratification properties is less than about 5%. 9. The cell or battery of claim 5, wherein said change is less than about 2%. 10. The cell or battery of claim 9, wherein the change in both the saturation properties and the stratification properties is about 2% or less. 11. A cathode plate, a cathode plate, and at least one cell having an absorber separator between the cathode plate and the cathode plate, wherein the separator has a maximum pore size of about 15 μm or less, and an average pore size. Wherein the porosity is less than or equal to about 2.8 and the porosity is at least about 90%. 12. The cell or battery according to claim 11, wherein the maximum pore size is about 14 μm or less. 13. The cell or battery according to claim 12, wherein the maximum pore size is about 10 μm or less. 14. A method for predetermining the suitability of an absorber separator material for a valve-adjustable lead-acid battery cell or battery, wherein the proposed absorber is selected and the proposed absorber is tested in the following manner. Testing at least one of the following protocols: (1) load cell pressure, (2) saturation and stratification properties, and (3) maximum and minimum pore size, and the proposed absorber is selected and pre-selected. Determining whether the proposed criterion is met, and then not using the proposed absorber in the cell or battery that does not meet the preselected criterion. 15. The test protocol and the pre-selected criteria used in the load cell test, wherein the load cell pressure in two months is at least about 6.
15. The method of claim 14, wherein said is zero. 16. The test protocol used is a saturation property and a stratification property, and the pre-selected criterion is that a change in at least one of these properties is less than about 10%. The method of claim 14, wherein 17. The test protocol used is a maximum pore size and an average pore size, wherein the pre-selected criterion is that the maximum pore size is about 15 μm or less;
15. The method of claim 14, wherein the average pore size is no more than about 2.8.