Hybrid scrim or pastepaper material for a plate-shaped battery electrode of a lead-acid battery, plate-shaped battery electrode with such scrim / pastry material, and lead-acid battery with such a battery electrode.

Abstract

The invention relates to a hybrid scrim / paste paper material for a plate-shaped battery electrode (2, 3) of a lead-acid battery, in particular for a positive plate-shaped battery electrode (2) of a lead-acid battery (1), wherein the scrim / paste paper material is designed as a nonwoven or woven mat and comprises: - fibers made of a first material which is chemically unstable, such that the fibers made of the first material dissolve at least substantially upon contact with an electrolyte of the lead-acid battery (1), in particular during the manufacture of the lead-acid battery (1); - fibers made of a second material which is chemically stable at least to the extent that the fibers made of the second material do not dissolve, or do not dissolve substantially, upon contact with the electrolyte of the lead-acid battery (1), in particular during the manufacture of the lead-acid battery (1);and - optionally a binding agent for the fibers from the second material;

Description

The present invention relates generally to lead-acid batteries and, more particularly, to a hybrid paper paste material for a plate-shaped battery electrode of a lead-acid battery.According to the prior art, in the production of lead storage batteries, after the grid has been pasted with a positive active material, the positive battery plates are matured and dried in batches or continuously in so-called ripening and drying chambers. The main ingredients in the form of lead oxide, water and lead sulfate are used to form 3-basic (3SrOPbSO 4) and / or 4-basic (4SrOPbSO 4) lead sulfates by ripening. The plates are placed predominantly in stacks on pallets without loosening. Rarely are they placed on pallets without loosening or, in the special case, double grids with outside lugs, are suspended loosely in racks.In order to prevent the detachment of the active material from the grid and also to ensure easy handling of the panels after the placement, in particular in the ripening and drying process and during the assembly of the battery cell, and in order to prevent the panels from adhering to one another to the greatest possible extent, it is known to apply a paste paper to the active material after the placement of the grids. In addition, the pasteboard material has the function of minimizing lead dust emissions during further processing, in particular assembly.On the other hand, the life of a lead-acid battery in cyclic use generally depends primarily on the life of the positive battery plates. Thus, in order to increase the life of a lead-acid battery, it is important to increase the life of the positive battery plates.This relates in particular to the mass sludge removal of the positive electrode plate. As a result of the volume expansion during the reaction of PbO 2 to PbSO 4 during a charging / discharging cycle, the positive active material releases from the positive electrode plate, particularly in the case of long-term loads, and thus loses electrical contact with the current collector. It is thus no longer available for obtaining electrical energy, so that the capacitance of the electrode initially decreases and the latter finally fails completely. The detached active material can also lead to micro short circuits at the negative electrode.Thus, in order to improve the life of a lead-acid battery in cyclic use, it is necessary to prevent structural changes of the positive active material due to charge and discharge, and particularly, to prevent the volume expansion of the positive active material in the reaction of PbO 2 to PbSO 4.In order to prevent the expansion of the positive active material, it is known to apply a nonwoven or woven material to the positive electrode plate after the paste has been applied. Specifically, the paste paper / scrim material is pressed into the surface of the active mass by nip rollers. The pressure rollers can additionally produce a surface structure, for example in the form of a corrugation or waffle structure on the plate surface. In the process step, where the paste paper / scrim material is applied, it is a continuous lead ribbon that is only then punched / divided into individual lead plates.The nonwoven or woven material is acid-resistant and does not dissolve, in particular, during a maturation process of the lead-acid battery, in particular during the production of the lead-acid battery, but also during further use of the lead-acid battery. These are in particular non-woven or woven mats which have glass fibres.However, the prior art solutions for improving the life of the positive battery electrode of a lead-acid battery have disadvantages. In particular, the use of nonwoven or woven mats increases the thickness and weight of the assembly. Moreover, it is not ensured that despite the provision of such a nonwoven or woven mat made of glass fiber, the positive active material of the battery electrode is retained during the entire service life.In particular, the surface of the positive electrode loses its (metallic) strength or its cohesion over the battery life under cyclic loading. The increasingly softer mass is held in the lattice by the scrim material, which does not dissolve or oxidize by the electrolyte.On the basis of this problem, the object of the invention is to provide a solution which is able to effectively prevent mass deposits of the positive electrodes even in the case of long-term loads on a lead-acid battery.This object is achieved according to the invention by a hybrid scrim or paste paper material as specified in independent patent claim 1. Advantageous further developments of the hybrid scrim or paste paper material according to the invention are specified in the dependent claims 2 to 20.Accordingly, the invention relates in particular to a hybrid scrim paper material for a plate-shaped battery electrode of a lead-acid battery, in particular for a positive plate-shaped battery electrode of a lead-acid battery, wherein the scrim paper material is designed as a nonwoven or woven mat and comprises fibers of a first material which is chemically unstable, so that the fibers of the first material at least substantially dissolve by contact with the electrolyte of the lead-acid battery, in particular during the production of the lead-acid battery.The scrim or paste paper material according to the invention comprises, in addition to the fibers made of the first, chemically non-resistant material, fibers made of a second material which is chemically resistant at least to such an extent that the fibers made of the second material do not dissolve or substantially do not dissolve due to contact with the electrolyte of the lead-acid battery, in particular during the production of the lead-acid battery, and preferably during the use of the lead-acid battery.In addition, a binder is optionally used, in particular for the fibers made of the second material.As a result of this composition of the scrim or pasteboard material, the fleece or fabric mat formed from the scrim or pasteboard material performs a dual function: due to the fibers made from the first material, the scrim or pasteboard material serves on the one hand as a "classic" pasteboard, which during the production of lead-acid battery during the maturation and drying process of the battery plates allows the pasteboard battery grids to be stacked and after maturation cannot adhere to one another or not significantly.However, as soon as the fibers from the first material come into contact with the electrolyte of generally about 38% sulfuric acid, they gradually dissolve, in particular are accelerated by oxidation.The fact that, as a result of the volume expansion during the reaction of PbO 2 to PbSO 4 the positive active material can nevertheless be prevented from becoming detached from the (positive) electrode plate, particularly under long-term loads, is present on the fibers made of the second material, which is chemically resistant to electrolyte and oxidation.The hybrid scrim or pasteboard material according to the invention, which is preferably designed in the form of a fleece or woven mat, thus functions as a supporting structure and imparts additional mechanical strength to the plate structure of the individual battery electrodes as a supporting structure.The fibers of the second material ensure uniform compression of the positive battery electrodes and, in particular, of the positive active material. The scrim paper material prevents the release of active material and at the same time serves during battery manufacture as a carrier for the wet lead oxide paste which is matured and dried after the paste has been patted in the ripening and drying process.By providing the fibers of the second, chemically resistant material, it is ensured that the fleece or fabric mat formed from the hybrid scrim or pasteboard material can become soaked with electrolyte while it is not chemically attacked, or not significantly attacked, by the electrolyte. Thus, the scrim or paste paper material according to the invention ensures that the positive active material is retained during the entire service life. It adheres to the positive active material of the positive electrode plates or is embedded in the surface structure without adhering to other substrates of the battery construction. This is decisive for a safe and effective performance of long-term batteries and of batteries which are cyclically loaded.According to preferred implementations of the hybrid scrim or paste paper material according to the invention, it is provided that the fibers made of the second material consist at least partially of a thermoplastic plastic material or comprise a thermoplastic plastic material.Studies have shown that fibers made of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyolefins and / or polybutylene terephthalate (PBT / PTMT) are particularly suitable for this purpose. Fibers made of polyethylene terephthalate (PET) are particularly preferred. It is furthermore preferred that all the fibers made of the second material are formed from a corresponding thermoplastic material.In this case, in particular, so-called core-shell fibers are also suitable, i.e. fibers formed from different thermoplastic materials. In particular, core-shell fibers are particularly suitable, which have a core made of PET material and a sheath made of PE material. Of course, however, other embodiments for such core-shell fibers are also possible.Although it is preferred that all the fibers formed from the second material consist of or are at least formed from a thermoplastic material, in particular from PET, it is also conceivable in principle for fibers made from another chemically resistant material to be provided, such as glass fibers, for example.With regard to the fibers made of the first, chemically unstable material, fibers are suitable which consist at least partially of cellulose or comprise cellulose.An optional binder is an acrylic group binder, in particular a binder based on a polyacrylic acid and / or polymethacrylic acid.Instead of such a binder, it is also possible to crosslink, in particular thermally crosslink, the fibers made of the second material.The scrim paper material of the present invention has many advantages.At least when the fibers have dissolved from the first material, the scrim paper material of the invention is a relatively lightweight material which nevertheless provides sufficient structural stability to the stack of plates in battery assemblies. The scrim paper material of the invention is as homogeneous as a paper but acid resistant. In addition, the scrim or paste paper material according to the invention has a reduced internal resistance due to the dissolving component.The scrim or paste paper material according to the invention contains, in particular, hardly any metals, pollutants or chemical contaminants, and is thus non-reactive. Also, no decomposition or carbon gassing occurs during the battery life.The scrim or paste paper material according to the invention optimizes the battery cycles without interfering with other substrates in the battery assembly, which is helpful in particular in the case of rapid discharge. In addition, due to the low internal resistance that can be achieved, a voltage drop at high currents and in particular at cold temperatures (<0 ° C.) can be reduced.In particular, it has been found that, due to the dissolution of the fibers from the first material in the scrim or paste paper material, pores form which react very well to the positive active material of the electrode, so that long-lived adhesion between the materials is ensured.According to preferred implementations of the scrim or pasteboard material according to the invention, it is provided that--in the case of thermal cross-linking of the fibers of the second material--the scrim or pasteboard material has about 20 to 70% by weight of fibers of the second material. If, on the other hand, a binder is used for crosslinking the fibers made of the second material, the proportion of fibers made of the second material is about 20 to 40% by weight, and preferably about 25 to 35% by weight, and even more preferably about 28 to 32% by weight.In this case, the scrim or paste paper material comprises in particular about 40 to 60% by weight of fibers of the first material, and preferably about 45 to 55% by weight of fibers of the first material, and even more preferably about 48 to 52% by weight of fibers of the first material.If a binder is used to crosslink the fibers of the second material, the scrim paper material should preferably comprise about 10 to 30 wt% binder, and preferably about 15 to 25 wt% binder, and more preferably about 18 to 22 wt% binder.In particular, this configuration can achieve that the scrim or paste paper material according to the invention has a relatively small thickness, so that the use of the scrim or paste paper material does not have any appreciable effect on the thickness (or weight) of the battery electrode.In particular, it is possible for the hybrid scrim or pasteboard material to have a thickness, determined according to ISO 534 (date: filing date), at a pressure of 100 kPa of only about 50 μm to 150 μm, and preferably of about 70 μm to about 110 μm, and even more preferably of about 85 μm to about 95 μm.At the same time, a surface-based mass, determined according to ISO 536 (status: filing date), of only 15 g / m 2 to about 30 g / m 2 and preferably of about 18 g / m 2 to about 28 g / m 2 and even more preferably of about 20 g / m 2 to about 25 g / m 2 can be achieved.Studies have shown that the hybrid scrim or paste paper material ensures optimized air permeability. In particular, an air permeability determined according to EN ISO 9237 (date: filing date) at a pressure of 2 mbar is about 1,800 I / m 2 / s to about 2,800 I / m 2 / s and preferably about 2,000 I / m 2 / s to about 2,500 I / m 2 / s.In the dry state, the scrim or pasteboard material according to the invention has a tensile strength or width-related breaking force of at least 0.8 N / mm, determined according to ISO 1924-2 (date: filing date). Thus, the active matter of the battery can be ensured throughout the life.In the wet state, i.e. after immersion in water, the hybrid scrim or pasteboard material has a tensile strength or breaking force, determined according to ISO 3781 (date: filing date), of at least 0.5 N / mm.Preferably, the fibers of the first material and the fibers of the second material are distributed homogeneously over the hybrid scrim or pasteboard material embodied as a nonwoven or woven mat.In order to ensure a certain elasticity of the fibers of the second material on the one hand, while at the same time ensuring that the active material structure of the battery, in particular the positive active material of the battery electrode, is retained during the entire service life, it is preferred that the fibers of the second material have an average outer diameter of from about 5 μm to about 150 μm and preferably from about 10 μm to about 100 μm.For the fibers made of the first material, it is also possible in particular to use tubular or hollow fibers, in particular made of cellulose or cellulose acetate, preferably having an outer diameter in a range between approximately 50 μm and approximately 150 μm and in particular in a range between approximately 60 μm and approximately 100 μm.With this measure, the pore formation in the scrim or paste paper material after the maturation and drying process can be improved, as a result of which particularly efficient adhesion of the scrim or paste paper material to the positive active material is guaranteed.Fibers of limited length, in particular short fibers, continuous fibers (filaments) and / or staple fibers, are suitable for the fibers of the first material and / or for the fibers of the second material.The scrim or paste paper material according to the invention can in particular have crimped fibers preferably with 2 to 50 crimped arches / cm, in particular with 10 to 20 crimped arches / cm. Depending on the crimp of the fibers of the first material or the fibers of the second material, the fiber density in the nonwoven or woven product can be adjusted accordingly.Alternatively or additionally, it is possible to set a specific surface area of the fibers, namely by selecting a corresponding cross-sectional shape of the fiber of the first and / or second material.In addition to a circular fiber cross section, it is in particular conceivable for the fibers of the first and / or second material to have a circular, trilobal, hexagonal, polygonal, star-shaped, quadrangular, X, K, C, or Y-shaped and / or irregularly shaped cross-sectional geometry.According to embodiments of the scrim or pasteboard material according to the invention, the fibers of the second material have a diameter between 500 nm and 500 μm and preferably a diameter between 100 nm and 500 μm.In particular, mean outer diameters of 500 nm to about 150 μm and preferably of about 5 μm to about 100 μm are suitable here. In particular, the fibers of the second material have an in particular average fineness strength on the smooth thread of 5 to 25 N / 5 cm.In particular for producing fleece or fabric mats which serve as scrim paper material for battery electrodes and in particular positive battery electrodes of a lead-acid battery, the scrim paper material can be consolidated, namely by converting a fleece into a fleece, in which a bond between the fibers is consolidated in particular from the second material.The bond of the fibers is preferably produced by frictional engagement or by a combination of frictional and positive engagement by means of a mechanical consolidation method.It is also conceivable here that the nonwoven product is consolidated, namely by converting a nonwoven into a nonwoven in which a bond between the fibers is consolidated, in particular from the second material, wherein the bond of the fibers is produced by means of a chemical consolidation method by material bonding by means of additives, in particular by means of the binder, or by means of thermal energy.Preferably, the scrim or paste paper material is produced by the wet process, i.e. as a flat web which is formed by dewatering of a fiber suspension on a wire base.The invention further relates to a plate-shaped battery electrode for a lead-acid battery, wherein the battery electrode has a battery electrode grid made of a lead alloy and a lead oxide paste applied at least partially or in regions to the battery electrode grid. According to the invention, the battery electrode further comprises a fleece or woven mat made of a hybrid scrim or pasteboard material of the type according to the invention described above.The invention furthermore relates to a lead-acid battery having a plurality of plate-shaped battery electrodes of the aforementioned type.The invention is described in more detail below with reference to the attached drawings.The following are shown: FIG. 1 is an exploded isometric view showing the general structure of an exemplary embodiment of the lead-acid battery according to the present invention; FIG. 2 shows schematically and in a partially cut-away plan view a plate-shaped battery electrode of the exemplary embodiment of the lead-acid battery according to the invention according to FIG. 1 ; wherein the plate-shaped battery electrode has a battery electrode grid made of a lead alloy and a lead oxide paste applied at least partially or in regions on the battery electrode grid; and FIG. 3 shows schematically and in a plan view the battery electrode grid of the plate-shaped battery electrode according to FIG. 2.The lead-acid battery 1 shown schematically and in an isometric exploded view in FIG. 1 has a plurality of cell elements which are contained in separate compartments of a housing 9 of the battery 1 with electrolyte. The lead-acid battery 1 is in particular a wet battery.The individual plate-shaped battery electrodes 2, 3 comprise electrically conductive electrode grids 4. a positive paste 5 is located on the electrode grid 4 of the positive battery electrode and a negative paste 6 is located on the electrode grid 4 of the negative battery electrode 3.A plurality of positive plates 2 and a plurality of negative plates 3 generally form at least a part of the electrochemical cell of the accumulator. Each set of plates or cell may include one or more positive plates 2 and one or more plates 3.As shown in FIG. 1, a plurality of plate sets may be electrically connected, for example, electrically connected in series, according to the capacity of the battery 1.The invention is not limited to the exemplary embodiment shown in the drawings, but rather results from a review of features disclosed herein.List of reference characters1 Lead-acid battery 1 / accumulator 2 Positive battery electrode 3 Negative battery electrode 4 Battery electrode grid 5 Positive active paste 6 Negative active paste 9 Case

Claims

Hybrid scrim / paste paper material for a plate-shaped battery electrode (2, 3) of a lead-acid battery, in particular for a positive plate-shaped battery electrode (2) of a lead-acid battery (1), wherein the scrim / paste paper material is designed as a nonwoven or woven mat and comprises: - fibers made of a first material which is chemically unstable, so that the fibers made of the first material at least substantially dissolve when contacting with an electrolyte of the lead-acid battery (1), in particular when manufacturing the lead-acid battery (1); fibers made of a second material which is chemically resistant at least to such an extent that the fibers made of the second material do not or substantially do not dissolve when contacting with the electrolyte of the lead-acid battery (1), in particular during the production of the lead-acid battery (1); and optionally a binder for the fibers made of the second material.Hybrid scrim / paste paper material according to claim 1, wherein the fibers of the second material consist at least partially of a thermoplastic plastic material or comprise a thermoplastic plastic material, wherein preferably the thermoplastic plastic material is polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyolefins and / or polybutylene terephthalate (PBT / PTMT).Hybrid scrim / paste paper material according to claim 2, wherein the fibers made of the second material are at least partially designed as core-shell fibers with a core made of a first thermoplastic plastic material and a sheath or jacket made of a second thermoplastic plastic material.Hybrid scrim / paste paper material according to one of claims 1 to 3, wherein the fibers made of the second material are at least partially designed as glass fibers or comprise glass fibers.The hybrid scrim / paste paper material of any one of claims 1 to 4, wherein the fibers of the first material are at least partially comprised of cellulose or comprise cellulose.Hybrid scrim / paste paper material according to any one of claims 1 to 5, wherein the binder is an acrylic group binder or comprises an acrylic group binder, wherein the binder is in particular a polyacrylic acid and / or polymethacrylic acid based binder.The hybrid scrim / paste paper material of any one of claims 1 to 5, wherein the hybrid scrim / paste paper material comprises: - about 20 to 70 wt% fibers of the second material, and preferably about 25 to 35 wt% fibers of the second material, and more preferably about 28 to 32 wt% fibers of the second material; - about 40 to 60 wt% fibers of the first material, and preferably about 45 to 55 wt% fibers of the first material, and more preferably about 48 to 52 wt% fibers of the first material; and - optionally about 10 to 30 wt% binder, and preferably about 15 to 25 wt% binder, and more preferably about 18 to 22 wt% binder.The hybrid scrim / pasteboard material of any one of claims 1 to 7, wherein the hybrid scrim / pasteboard material has a thickness at 100 kPa pressure determined according to ISO 534 (date: filing date) of from about 50 μm to 150 μm, and preferably from about 70 μm to about 110 μm, and more preferably from about 85 μm to about 95 μm.The hybrid scrim / pasteboard material of any one of claims 1 to 8, wherein the hybrid scrim / pasteboard material has a basis weight, as determined according to ISO 536 (Filing Date), of from about 15 g / m 2 to about 30 g / m 2 and preferably from about 18 g / m 2 to about 28 g / m 2 and more preferably from about 20 g / m 2 to about 25 g / m 2.The hybrid scrim / pasteboard material of any one of claims 1 to 9, wherein the hybrid scrim / pasteboard material has an air permeability, as determined according to EN ISO 9237 (date: filing date) at 2 mbar pressure, of from about 1,800 l / m 2 / s to about 2,800 l / m 2 / s, and preferably from about 2,000 l / m 2 / s to about 2,500 l / m 2 / s.Hybrid scrim / paste paper material according to one of claims 1 to 10, wherein the hybrid scrim / paste paper material has a tensile strength or width-related breaking force of at least 0.8 N / mm, determined according to ISO 1924-2 (date: filing date).Hybrid scrim / paste paper material according to any one of claims 1 to 11, wherein the hybrid scrim / paste paper material, after immersion in water, has a tensile strength or width-related breaking force of at least 0.5 N / mm, determined according to ISO 3781.Hybrid scrim / paste paper material according to one of claims 1 to 12, wherein the fibers of the first material and the fibers of the second material are distributed homogeneously over the hybrid scrim / paste paper material designed as a nonwoven or woven mat.The hybrid scrim / paste paper material of any one of claims 1 to 13, wherein the fibers of the second material have an average outside diameter of from about 500 nm to about 150 μm, and preferably from about 5 μm to about 100 μm.Hybrid scrim / paste paper material according to any of claims 1 to 14, wherein the fibers of the first material comprise tubular or hollow fibers, preferably with an outer diameter in a range between about 50 μm to about 150 μm and in particular in a range between about 60 μm to about 100 μm.Hybrid scrim / paste paper material according to one of claims 1 to 15, wherein the fibers made of the first material and / or the fibers made of the second material are designed as fibers of limited length, in particular short fibers, as continuous fibers (filaments) and / or as staple fibers.The hybrid scrim / paste paper material of any one of claims 1 to 16, wherein the fibers from the first material comprise crimped fibers preferably having 2 to 50 crimps / cm, more preferably having 10 to 20 crimps / cm; and / or wherein the fibers from the second material comprise crimped fibers preferably having 2 to 50 crimps / cm, more preferably having 10 to 20 crimps / cm.The hybrid scrim / pasteboard material of any one of claims 1 to 17, wherein the hybrid scrim / pasteboard material is a mechanically formed nonwoven mat, an aerodynamically formed nonwoven mat, a hydrodynamically formed nonwoven mat, or an electrostatically formed nonwoven mat.Hybrid scrim / paste paper material according to claim 18, wherein the nonwoven mat is strengthened by a conversion of a nonwoven into a nonwoven in which a bond between the fibers of the first material and / or of the second material is strengthened, wherein the bond of the fibers is produced by frictional engagement or by a combination of frictional and positive engagement by means of a mechanical strengthening method.Hybrid scrim / paste paper material according to claim 18, wherein the nonwoven mat is consolidated by converting a nonwoven fabric into a nonwoven fabric in which a bond between the fibers of the first and / or second material is consolidated, wherein the bond of the fibers is produced by means of a chemical consolidation method and / or by heat by material bonding.Plate-shaped battery electrode (2, 3) for a lead-acid battery (1), wherein the battery electrode (2, 3) comprises: - a battery electrode grid (4) made of a lead alloy; - a lead oxide paste (5, 6) applied at least partially or in regions to the battery electrode grid; and - a nonwoven or woven mat made of a hybrid scrim / paste paper material according to one of claims 1 to 20.A lead-acid battery (1) comprising a plurality of plate-shaped battery electrodes (2, 3) according to claim 21.

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