DE102020109571A1 - Compression stable battery separator - Google Patents

Abstract

The invention relates to a battery separator with a, preferably open-pore, substrate, in particular a nonwoven material in accordance with DIN EN ISO 9092 (2018-02) as the base body, the base body having a coating containing filler particles in a proportion of 80% by weight to 98% by weight. % and binder in a proportion of 2% by weight to 10% by weight, each based on the coating weight, the filler particles having a particle size distribution with ad50 according to ISO 21501-3 of 0.05 µm to 10 µm and a particle size distribution range ( (d90-d10) / d50) from 0.05 to 3.5.

Description

Technical area

The invention relates to a battery separator which contains filler particles and binder, a method for its production and its use as a substrate for coating with a lamination binder and as an electrical insulation material in an electrochemical cell. The invention also relates to an electrode-separator unit which contains the battery separator and an electrochemical cell which contains the electrode-separator unit according to the invention.

State of the art

In electrochemical cells, the positively and negatively charged electrodes are mechanically separated from one another by a non-electrically conductive layer, the battery separator, in order to avoid an internal short circuit. Due to the porous structure, a separator enables the transport of ionic charges as a basic requirement for the current consumption of electricity during battery operation.

The basic requirements for battery separators are chemical and electrochemical stability with respect to the active electrode materials and the battery electrolyte. At the structural level, a high porosity is required to accommodate the electrolyte in order to ensure high ionic conductivity. At the same time, the pore size and the structure of the channels must effectively suppress the growth of metal dendrites in order to avoid a short circuit, as described in Journal Power Sources 2007, 164, 351-364.

A disadvantage of common battery separators is that they often drastically lose their porosity when subjected to pressure loads, as described in Journal of Power Sources 196 (2011) 8147-8153, and the conductivity of the separator thus deteriorates.

Particularly high pressure loads on the separator occur with electrode pairings with a high volume change during the charging / discharging process, e.g. with silicon-containing anodes and when the separator is laminated to a battery electrode.

EP3357114A4 describes a silicon-carbon composite anode, consisting of 40 wt.% to 80 wt.% silicon particles and their use in a Li-ion battery. This publication does not describe how the separator can compensate for the increase in volume of the electrodes, in particular the anodes, during the cycling processes.

A laminated separator is described in EP2750216B1 . The battery separator consists of a micro-porous, multi-layer polymer film and has good thermal stability up to 135 ° C, low surface shrinkage in the xy plane (<20% to 130 ° C) and good adhesion to the electrode. However, this separator loses its porosity due to the use of a polyolefinic membrane in the lamination process.

The in EP2924781A1 and EP3244475A1 described separators based on polyolefin.

Maintaining the set porosity, even under pressure and temperature loads, is of great advantage, since this is the only way to ensure a low ion transport resistance over the long term. This is what is known as compression stability. In particular, there must be a high level of compression stability with respect to the compression forces acting on the separator during the battery cell production process and during operation.

The invention is therefore based on the object of providing a separator which enables the porosity set in it to be set to a defined extent even under high pressure and temperature loads.

Presentation of the invention

This object is achieved by a battery separator with a, preferably open-pore substrate, preferably a fiber-based substrate, in particular a nonwoven according to DIN EN ISO 9092 (2018-02) as a base body, the base body having a coating which contains filler particles in a proportion of 80% by weight to 98% by weight and binder in a proportion of 2% by weight to 20% by weight, each based on the coating weight, wherein the filler particles have a particle size distribution with ad50 ISO 21501-3 (2019-11) of 0.05 µm to 10 µm and a particle size distribution range (SPAN) ((d90-d10) / d50) of 0.1 to 3.5.

According to the invention, it has surprisingly been found that said battery separator can maintain its set porosity even under pressure and temperature loads.

In this way, a low ionic conductivity can be ensured. In addition, the specific particle size distribution range in the battery separator according to the invention enables a defined compressibility to be set.

Without committing to a specific mechanism, it is assumed that this is made possible by the fact that, in the interaction of the particles and their defined size distribution, cavities are built up between the particles (interstitial volumes), which are caused by particle-particle contact and in the case of fiber-containing base bodies such as nonwovens Particle-fiber contact and fiber-fiber contact are connected to one another, and they do not collapse completely under the temperature and pressure loads that are common when using battery separators. For example, the battery separator according to the invention is stable up to temperatures of 150 ° C., more preferably up to 170 ° C., particularly preferably 200 ° C., and / or at pressures of up to 0.3 MPa, preferably up to 2.5 MPa, even more preferably up to 5.0 MPa, very particularly preferably up to 15 MPa, and / or pressing forces of up to 500 N, preferably up to 1500 N, particularly preferably up to 4000 N.

According to the invention, the term gusset volume is geometrically differentiated from the pore volume in that the gusset volume forms concave surfaces at its boundary to the filler particles contained in the battery separator, while a pore volume forms convex surfaces at the interface, in each case seen from the reference system of the free volume.

Electrolyte can be permanently located in these interstitial volumes, which, due to the interconnected interstitial volumes, leads to a high continuous ionic conductivity over the entire thickness (Z-direction) of the battery separator and promotes a low internal resistance of the cell.

Another advantage of the battery separator according to the invention is that it contains a high proportion of filler particles relative to the binder proportion. Due to the high degree of filling with filler particles, these can form an endless, coherent particle structure which surrounds the substrate. This in turn has an advantageous effect on the temperature and pressure stability of the gusset volume. In particular, the high proportion of filler particles enables volume elements to form in the battery separator, which in their z-direction essentially only consist of filler particles and the gusset volumes formed thereby. As a result, high pressures can be absorbed by the filler particles on one side of the battery separator and transferred directly to the other side without the geometry of the battery separator being adversely affected or the porosity collapsing completely.

Conversely, an endless, coherent wedge volume filled with electrolyte can form, which is protected from deformation and closure by the temperature and pressure stability of the filler particles and ensures constant ionic conduction between anode and cathode.

According to the invention, the base body has a coating. According to the invention, this is to be understood as meaning that the coating can be present over a large area on the base body. As an alternative or in addition, the coating can also have penetrated at least partially into the pores of the base body in the manner of a filling. The coating is particularly preferably in the form of a continuous filling. The coating can be present on one or both sides of the base body.

In a preferred embodiment of the invention, 10% by volume to 65% by volume, even more preferably 15% by volume to 60% by volume and in particular 30% by volume to 50% by volume of the battery separator according to the invention form volume elements which in their z-direction consist essentially only of filler particles. This increases the compression stability of the battery separator according to the invention. The proportion of these volume elements in the battery separator can be determined using radiometric measuring methods.

According to the invention, the battery separator has an open-pored substrate. An open-pore substrate is to be understood as meaning a substrate that has pores that are at least partially accessible from the substrate surface having. According to the invention, more than 50% of the pores are preferably accessible from the substrate surface.

In particular, the pores of the open-pored substrate should be able to take up filler particles and / or enable the in-situ deposition of filler.

According to the invention, the filler particles have a particle size distribution with ad50 value (measured according to ISO 21501-3 (2019-11)) of 0.05 µm to 10 µm, more preferably 0.05 µm to 2 µm, even more preferably 0.1 µm to 2 µm, more preferably from 0.1 µm to 1.0 µm, even more preferably from 0.2 µm to 1.0 µm, in particular from 0.3 µm to 0.5 µm. In practical tests it has been found that with these particle size distributions there are particularly pores with a small mean pore size, measured according to DIN ISO 4003: 1990, of preferably from 0.01 µm to 1.5 µm, even more preferably from 0.1 µm to 0, 7 µm, in particular from 0.3 µm to 0.5 µm. The aforementioned particle size distributions and pore diameters are particularly advantageous in order to prevent dendrite growth in Li-ion batteries and at the same time to ensure a high ionic capacity.

According to the invention, the filler particles have a particle size distribution range ((d90-d10) / d50) from 0.05 to 3.5, preferably from 0.1 to 3.5, preferably from 0.1 to 3.0, even more preferably from 0.2 to 3.0, more preferably from 0.2 to 2.5, even more preferably from 1.0 to 2.5, even more preferably from 1.2 to 2.5, especially from 1.2 to 2.0. In practical tests it has been found that with these particle size distribution ranges, particularly high interstitial volumes with a narrow pore size distribution are formed. The battery separator according to the invention advantageously has a pore size distribution with an average pore size, measured according to DIN ISO 4003: 1990, of 0.25 μm to 0.5 μm.

The setting of certain particle size distribution ranges can be realized in different ways, e.g. by sieving for powders or filtering for dispersions.

In practical tests it was found that with the particle sizes and particle size distribution ranges according to the invention, a particularly compression-stable battery separator with a high interstice volume is formed. In a preferred embodiment of the invention, the battery separator has a gusset volume, as defined in the section “Standards and measurement methods”, of more than 25% by volume, for example from 25% by volume to 75% by volume, even more preferably from 40% by volume to 70% by volume and in particular from 45% by volume to 65% by volume. The advantage of a high interstice volume is a high electrolyte uptake by the battery separator, which in turn correlates with a high ionic conductivity of the battery separator soaked with electrolyte. Without committing to a specific mechanism, it is assumed that the advantageous effects of setting a high interstitial volume result from the fact that with the particle size distribution ranges according to the invention, smaller particles can settle less in the interparticle spaces formed by larger particles and these spaces thus take up an unusually large amount of electrolyte can. The interparticle spaces can be determined with porosity measurements (air permeability according to Gurley). Gurley's air permeability correlates with the isobaric air flow through the separator and thus provides information about the porosity of the separator and, consequently, about its interstitial volume.

Another advantage of a high gusset volume is that solvents such as water can easily escape when the battery separator dries. This is particularly relevant for laminated products, e.g. an electrode / battery separator / electrode laminate. The conduction effect of the battery separator compared to the solvents is advantageous here. Since the flat diffusion path in the z-direction through the impermeable conductor materials is not available in these laminates, the flat laminated battery separator can absorb the solvent residues from the electrodes in the laminate and, via its gusset volumes, lead it away particularly quickly to the laminate edges, from where the solvent residues from the Laminate can escape.

According to the invention, the battery separator has an open-pore substrate, preferably an open-pore fiber-based substrate, as the base body. In the following, unless stated otherwise, reference is made to the substrate per se, ie in the uncoated state. The use of a nonwoven is particularly preferred. The use of papers, woven fabrics, knitted fabrics and / or crocheted fabrics is also conceivable. The use of foams, membranes, foils, in particular stretched foils, perforated foils, track-etched foils, mechanically or laser-perforated foils, and micro-lithographed foils is also conceivable. The advantage of using a nonwoven is that it is easy to achieve low weights per unit area and low thicknesses. In addition, an isotropic fiber distribution can be achieved. This is advantageous because the fiber-fiber gusset volumes are reduced as well be distributed isotropically and so the ionic conductivity can consequently also occur isotropically due to electrolyte storage. This ensures a homogeneous migration of Li ions in the end product.

The non-woven fabric is preferably a wet-laid non-woven fabric. This is advantageous because the wet laying process enables extremely low weights per unit area and thicknesses to be achieved with high homogeneity and mechanical stability at the same time.

The thickness of the open-pored substrate, in particular the nonwoven fabric, can be reduced even further by calendering. Accordingly, a calendered nonwoven, in particular a calendered wet nonwoven, is particularly preferred according to the invention. In a preferred embodiment, the thickness of the open-pore substrate is from 2 μm to 50 μm, more preferably from 3 μm to 30 μm, in particular from 5 μm to 15 μm, measured in accordance with EN 29073-2. A small thickness is advantageous because it favors a high volumetric energy density of the battery.

The weight per unit area of the open-pore substrate, preferably the fiber-based substrate, in particular the nonwoven, measured according to EN 29073-T1, is preferably from 2 g / m ² to 30 g / m ² , more preferably from 4 g / m ² to 20 g / m 2 ² , more preferably from 4 g / m ² to 15 g / m ² and in particular from 4 g / m ² to 10 g / m ² . A low weight per unit area of the open-pored substrate is advantageous because it favors a high gravimetric energy density of the battery.

The porosity of the open-pore substrate, preferably the fiber-based substrate, in particular the nonwoven fabric, is preferably from 40% by volume to 90% by volume, more preferably from 50% by volume to 80% by volume, in particular from 55% by volume to 70% by volume. %. As mentioned above, the porosity relates to the substrate itself, i.e. in the uncoated state. The advantage of high porosity is that large volumes are available for coating with filler particles. This in turn increases the compression stability. In a preferred embodiment of the invention, the open-pore substrate has a pore volume in which from 20% by volume to 75% by volume, more preferably from 25% by volume to 65% by volume and in particular from 30% by volume to 60% by volume. % belong to z-through pores. As mentioned above, the pore volume relates to the substrate itself, i.e. in the uncoated state.

The open-pore substrate preferably has z-through pores. Z-through pores are to be understood as meaning pores which have no interruptions through substrate material in the z-direction. This can be determined, for example, using image analysis methods. This is advantageous because volume elements can thereby form in the battery separator, which in their z-direction consist essentially only of filler particles, which increases the compression stability.

The fiber-based substrate, in particular in its embodiment as a wet nonwoven fabric, can have staple fibers and / or short-cut fibers. According to the invention, staple fibers, in contrast to filaments which have a theoretically unlimited length, are fibers with a limited length of preferably 1 mm to 80 mm, more preferably 3 mm to 30 mm. According to the invention, short-cut fibers are to be understood as meaning fibers with a length of preferably 1 mm to 12 mm, even more preferably 3 mm to 6 mm. The mean titer of the fibers of the fiber-based substrate can vary depending on the desired structure of the substrate. The use of fibers with an average titer of 0.02 dtex to 3.3 dtex, preferably 0.04 dtex to 1.7 dtex, preferably 0.06 dtex to 1.0 dtex, has proven to be particularly favorable.

The fibers can be designed in the most varied of shapes, for example as flat, hollow, round, oval, trilobal, multilobal, bico, and / or island-in-the-sea fibers. According to the invention, the cross-section of the fibers is preferably round or oval, since in this way a wedge volume is inevitably formed at the points of contact of the fiber-fiber and fiber-particle surfaces in any geometric orientation to one another.

According to the invention, the fibers can contain a wide variety of fiber polymers, preferably polyacrylonitrile, polyvinyl alcohol, viscose, cellulose, polyamides, polyimides, in particular polyamide 6 and polyamide 6.6, polyesters, in particular polyethylene terephthalate and / or polybutylene terephthalate, copolyesters, polyolefins, in particular polyethylene and / or polypropylene, and / or mixtures thereof. Preference is given to polyesters, in particular polyethylene terephthalate and / or polybutylene terephthalate and / or polyolefins, in particular polyethylene and / or polypropylene. The advantage of using polyesters is that they have high mechanical strength.

The fiber-based substrate advantageously has matrix fibers, that is to say fibers that are essentially unfused in the substrate. The matrix fibers preferably have a melting point of over 160.degree. C., more preferably over 200.degree. C., in particular over 250.degree. C. and / or a decomposition point of over 250.degree. C., in particular over 350.degree. These improve the structural stability of the fiber-based substrate under pressure and / or temperature loading and lead to a low area shrinkage, preferably up to 200.degree.

The proportion of matrix fibers in the fiber-based substrate is advantageously from 5 to 70% by weight, preferably from 5 to 50% by weight, in particular from 5 to 35% by weight, based on the total weight of the fiber-based substrate. This is advantageous because in this area a very high geometric stability with respect to the loads mentioned and a very high structural homogeneity is achieved.

Practical tests have shown that the at least partial use of matrix fibers with an average titer of less than 1 dtex, preferably from 0.02 dtex to 1 dtex, has an advantageous effect on the size and structure of the pore sizes and inner surface as well as on the density of the nonwoven .

The fiber-based substrate also preferably has binding fibers, i.e. fibers which are at least fused in the substrate. The fibers commonly used for this purpose can be used as binding fibers, provided that they can be at least partially thermally softened and / or fused. Binding fibers can be uniform fibers or also multi-component fibers. Binding fibers particularly suitable according to the invention are fibers in which the binding component has a melting point which is below the melting point of the matrix fibers to be bound, preferably below 250 ° C, more preferably from 70 to 235 ° C, even more preferably from 125 to 225 ° C , particularly preferably from 150 to 225 ° C. Suitable fibers are in particular thermoplastic polyesters and / or copolyesters, in particular polybutylene terephthalate (PBTP), polyolefins, in particular polypropylene, polyamides, polyvinyl alcohol, and their copolymers and mixtures.

In a preferred embodiment, the difference between the melting or decomposition point of the matrix fiber on the one hand and the melting point of the binding fibers on the other hand is at least 30.degree. C., for example from 30.degree. C. to 60.degree.

Binding fibers particularly suitable according to the invention are multicomponent fibers, preferably bicomponent fibers, in particular core / sheath fibers. Core / sheath fibers contain at least two fiber polymers with different softening and / or melting temperatures. The core / sheath fibers preferably consist of these two fiber polymers. The component that has the lower softening and / or melting temperature is to be found on the fiber surface (cladding) and the component that has the higher softening and / or melting temperature is to be found in the core. In the case of core / sheath fibers, the binding function can be performed by the materials which are arranged on the surface of the fibers. A wide variety of materials can be used for the jacket. According to the invention, preferred materials for the jacket are polybutylene terephthalate (PBT), polyamide (PA), polyethylene (PE), copolyamides and / or copolyesters. A wide variety of materials can also be used for the core. According to the invention, preferred materials for the core are polyesters (PES), in particular polyethylene terephthalate (PET) and / or polyethylene naphthalate (PEN) and / or polyolefins (PO).

The use of core-sheath binding fibers is preferred according to the invention, since in this way a particularly homogeneous distribution of the binding agent component in the nonwoven can be achieved.

The use of core-sheath binding fibers is particularly advantageous. In these fibers, the sheath has a lower melting point than the core. Core-sheath binding fibers with a sheath which has a melting point of below 240 ° C., preferably from 200 ° C. to 225 ° C., and a core with a melting point and / or decomposition point of over 240 ° C., preferably 250 ° C., are preferred up to 270 ° C. The advantage of a comparatively high melting point is that the battery separator according to the invention can be dried at higher temperatures.

Also preferred are core-sheath binding fibers with a sheath that has a melting point of below 160 ° C., preferably from 100 ° C. to 150 ° C., and a core with a melting point of above 160 ° C., preferably from 160 ° C. to 170 ° C ° C.

The use of undrawn binding fibers is also advantageous.

In practical tests, nonwovens with very good properties could be obtained with PET-PBT bicomponent fibers and / or PET-CoPES bicomponent fibers. Good results could also be achieved with fibers from the class of polyolefins, such as, in particular, polyethylene-polypropylene bicomponent fibers. PEN-PET bicomponent fibers are also suitable.

However, the use of monocomponent binding fibers is also conceivable, provided that these can be at least partially thermally softened. The choice of monocomponent binding fibers depends on the matrix fiber used. For example, polyamide 6 binding fibers are suitable for binding polyamide 66 matrix fibers and copolyester, PBT or undrawn binding fibers for binding polyethylene terephthalate fibers. The use of undrawn binding fibers is particularly preferred, since they can be used to produce particularly thin nonwovens.

The mean titer of the binding fibers can vary depending on the desired structure of the nonwoven fabric. The use of binding fibers with an average titer of 0.2 to 2.2 dtex, preferably 0.5 to 1.3 dtex, has proven to be favorable. The advantage of comparatively thick binding fibers is that when they are compressed in the Z direction, the binding fibers absorb the major part of the mechanical forces and thereby relieve the matrix fibers of the pressure load and the matrix fibers are not pressed into the gusset volumes as a result. This applies in particular to the matrix fibers with a smaller titer than the binding fibers.

The binding fibers can be connected to one another and / or to the matrix fibers of the nonwoven fabric by thermofusion. Solidification by means of hot air flowing through in an oven has proven to be particularly suitable.

The proportion of binding fibers in the fiber-based substrate is advantageously from 95% by weight to 50% by weight, preferably from 95% by weight to 65% by weight, in particular from 95% by weight to 65% by weight. based on the total weight of the fiber-based substrate. This is advantageous because a very high mechanical strength of the entire fiber substrate is achieved in this area, which has a positive effect on the compression stability.

In an advantageous embodiment, the fiber-based substrate has nanofibers. These have a diameter of less than 1 µm and are advantageous because they increase the homogeneity of the fiber-based substrate. In addition, compared to fibers of higher titers, they have a larger fiber surface area per weight, which leads to a higher proportion of fiber-fiber and fiber-particle gusset volumes for a comparable proportion of the substrate. The proportion of nanofibers in the fiber-based substrate is advantageously from 0.1% by weight to 20% by weight, more preferably from 0.1% by weight to 10% by weight, based on the total weight of the fiber-based substrate. This is advantageous because, particularly in the aforementioned areas, a high degree of homogeneity, high mechanical stability and high geometric stability against pressure and temperature loads can be achieved with a high additional interstice volume compared to fibers with a higher denier.

The use of partially crystalline and / or crystalline fibers is particularly advantageous. The crystalline areas in the fibers usually have a higher compression modulus than amorphous fibers, which favors a high compression stability of the fiber-based substrate.

In one embodiment of the invention, the fiber-based substrate is bound with a fiber binder. Preferred fiber binders are crosslinked fiber binders. These can be produced, for example, from crosslinking polymer solutions and dispersions. Crosslinked acrylate-based fiber binders are particularly preferred. The proportion of the fiber binder in the fiber-based substrate is advantageously from 5% by weight to 50% by weight, more preferably from 10% by weight to 40% by weight, in particular from 15% by weight to 35% by weight, based on the total weight of the fiber-based substrate.

According to the invention, the battery separator contains filler particles. In contrast to binder particles, filler particles are to be understood as meaning particles which, in isolated form, at least among themselves, i.e. without a binder, have no or only insignificant adhesive forces.

The filler particles can be present in and / or on one or both surfaces of the substrate. They are advantageously distributed homogeneously in the xy and / or z directions. This configuration enables short circuits and dendrite growth to be prevented in a particularly effective manner. Furthermore, the As a result, battery separators according to the invention have a particularly uniform compression stability. This in turn has a positive effect on the cycle stability of the battery.

It is advantageous if all of the pores of the open-pored substrate are homogeneously filled with the filler particles. The particles preferably have a particle size distribution in which the d50 value, more preferably the d90 value, of the filler particles is smaller than the mean pore sizes of the substrate.

The filler particles can be organic, inorganic particles or mixtures thereof. Preferred organic particles are selected from the group consisting of polypropylene, polyvinylpyrrolidone, polyester, polyamide, polytetrafluoroethylene, polyvinylidene difluoride, perfluoro-ethylene-propylene, polystyrene, polyacrylate, polyimide and copolymers of the aforementioned polymers and mixtures thereof. Particularly preferred organic particles are selected from the group consisting of polypropylene, polyvinylpyrrolidone and mixtures thereof.

Metal oxides, metal hydroxides and silicates, for example, are suitable as inorganic filler particles. Preferred inorganic particles are selected from the group consisting of aluminum oxide, aluminum oxide hydroxide, silicon oxide, aluminosilicates, zeolites, zirconium oxide, titanium dioxide, magnesium oxide, phosphates, fluorides and mixtures thereof. Particularly preferred inorganic particles are aluminum oxide, aluminum oxide hydroxide, silicon oxide, zirconium oxide and mixtures thereof. Very particularly preferred inorganic particles are aluminum oxide, aluminum oxide hydroxide and zirconium oxide, since these are particularly corrosion-resistant in common battery electrolytes. Chemically doped particles of the above materials are also suitable.

The filler particles are preferably Na or Li ions, conductive organic and inorganic materials. The filler particles are preferably at least partially ion-conductive, so that they can make a partial contribution to the overall conductivity of the separator. Hard filler particles which do not reduce the compression stability of the separator are particularly preferred here. These are in particular Garnet, Nasicon, Lisicon materials and Perovskite. Mechanically soft materials such as sulfidic glass ceramics are not suitable. This would reduce the compression stability.

According to the invention, the filler particles are preferably present in a proportion of 80% by weight to 98% by weight, even more preferably 90% by weight to 98% by weight, in particular 92% by weight to 97% by weight, based on the total weight of the coating . It has been found that with these proportions a particularly high compression stability can be achieved. More preferably, the filler particles are present in a proportion of 50% by weight to 90% by weight, even more preferably 60% by weight to 85%, in particular 65% by weight to 80% by weight, based on the total weight of the battery separator according to the invention.

In a preferred embodiment of the invention, the Mohs hardness of the filler particles is from 2 Mohs to 10 Mohs, more preferably from 5 Mohs to 10 Mohs and in particular from 7 Mohs to 9 Mohs.

The high Mohs hardness of the filler particles increases the compression stability of the battery separator according to the invention. According to the invention, the coating contains binder in a proportion of 2% by weight to 10% by weight, more preferably 2% by weight to 8% by weight, in particular 3% by weight to 7% by weight, based on the total weight of the coating on.

The advantage of using a binder in a proportion of less than 10% by weight is that it allows a high interstice volume to develop.

In a preferred embodiment, the binder is in particulate form. The binder particles preferably have a particle size distribution with a d50 value of the binder particles (measured according to ISO 21501-3) of 0.01 µm to 7 µm, more preferably 0.02 µm to 2 µm, in particular 0.05 µm to 1 µm on.

With the aforementioned values, the mean particle size of the binder particles is in the same order of magnitude as that of the filler particles. As a result, filler and binder particles have a similar size, so that a differentiation from a geometrical point of view in the formation of the interstitial volume is not possible or only with difficulty. Since the binder particles can namely preferably occupy the same grid positions as the filler particles, penetration of the binder particles into the interstice volume between the filler particles can be reduced. In addition, the binder particles integrated in the lattice structure are due to Due to their inherently higher flexibility, they can take up compression loads in a targeted manner and thereby enable an adjustable compressibility of the battery separator according to the invention. Adjustable compressibility is particularly advantageous in combination with strongly breathing electrodes, since these are subject to strong changes in volume during charging / discharging processes. Due to the adjustable compressibility, the battery separator according to the invention can at least partially compensate for changes in volume of the electrodes during the formation and cycling of the battery. This can reduce the mechanical stress in the battery during construction and use.

The binder is preferably an organic binder. Preferred binders are selected from the group consisting of polyvinylidene difluoride and its copolymers, polyolefins, for example polyethylene, polyacrylate, for example perfluoropolyacrylate, polymethacrylate, polystyrene butadiene, acrylonitrile butadiene copolymers and mixtures thereof.

Preferred organic binders are selected from the group consisting of polypropylene, polyethylene, polystyrene butadiene, polypropylene, polyethylene, polyvinylidene difluoride and mixtures thereof.

In the case of binder particles, the binder is preferably chemically crosslinked. This is advantageous because the binder therefore has a lower tendency to film and thus negatively affects the interstice volume to a lesser extent in the event of temperature or pressure loads.

In a further embodiment, the binder is a binder that was applied in the form of a solution, dispersion and / or emulsion. This is advantageous because the binder in this form can be processed particularly well with the filler particles to form a homogeneous coating paste, which promotes homogeneity in the end product.

In a further embodiment of the invention, the binder is present as a mixture of binder particles and binder, which was applied in the form of a solution, dispersion and / or emulsion. The proportion of binder particles, based on the total weight of the binder, is preferably in the range from 40% by weight to 95% by weight, even more preferably from 60% by weight to 90% by weight and in particular from 60% by weight to 80% by weight . % before. Furthermore, the proportion of binder that was applied in the form of a solution, dispersion and / or emulsion, based on the total weight of the binder, is preferably in the range from 5% by weight to 60% by weight, even more preferably from 10% by weight to 40% by weight and in particular from 20% by weight to 40% by weight.

Preferred binders, which can be applied in the form of a solution, dispersion and / or emulsion, are selected from the group consisting of carboxymethyl cellulose, polyvinyl alcohol, polycarboxylate, polyacrylic acid, polyvinylpyrrolidone and mixtures and copolymers thereof. Preferred copolymers are selected from the group of copolymers made from polyvinyl alcohol, polycarboxylate, polyacrylic acid, polyethylene oxides, polyethylene glycol and polyvinylpyrrolidone.

The battery separator preferably has a thickness, according to DIN EN 29073 - T2, of 3 μm to 70 μm, more preferably 5 μm to 30 μm, in particular 8 μm to 25 μm. Thicknesses of over 10 μm are preferred, since the advantages of an adjustable compressibility can be used particularly well here.

The battery separator preferably has a weight, according to DIN EN 29073 - T1, from 3 g / m ² to 50 g / m ² , preferably from 5 g / m ² to 35 g / m ² , even more preferably from 6 g / m ² to 35 g / m ² and in particular from 7 g / m ² to 35 g / m ² .

The battery separator preferably has mean pore sizes, measured in accordance with ASTM F 316, of 0.05 μm to 2 μm, preferably from 0.01 μm to 1 μm, even more preferably from 0.15 μm to 0.75 μm.

Preferably, the battery separator has an elongation measured in the machine direction DIN EN 29073-3 (1992-08) , from 5% to 50%, more preferably from 6% to 30%, in particular from 8% to 20%. A slight expansion of the battery separator is advantageous because it is more dimensionally stable and thus better preserves its interstice volume during processing steps.

The battery separator preferably has a maximum tensile force measured in the machine direction DIN EN 29073-3 (1992-08) , from 10 N / 5 cm to 60 N / 5 cm, more preferably from 10 N / 5 cm to 50 N / 5 cm, in particular from 14 N / 5 cm to 45 N / 5 cm.

The battery separator preferably has an air permeability according to Gurley, measured according to ISO 5636-3, of 20 seconds to 350 seconds, more preferably from 30 seconds to 300 seconds, in particular from 50 seconds to 200 seconds.

Gurley's air permeability correlates with the isobaric air flow through the separator and thus provides information about the porosity of the separator and, consequently, about its interstitial volume.

With a square area, the battery separator preferably has an area shrinkage up to 200 ° C. of 0 area% to 10 area%, preferably from 0 area% to 2 area%, even more preferably from 0.1 area% to 1 area%. A low area shrinkage is advantageous because it offers safety advantages and the battery separator can also be processed, e.g. laminated and / or dried, at higher temperatures.

In a preferred embodiment, the battery separator has the filler particles in a proportion of 50% by weight to 90% by weight, more preferably 60% by weight to 85% by weight, in particular 65% by weight to 80% by weight, and the binder in a proportion of 1% by weight to 10% by weight, more preferably 1.2% by weight to 8% by weight, in particular 1.3% by weight to 3% by weight, based in each case on the total weight of the battery separator.

Another subject matter of the present invention comprises a further battery separator which contains filler particles in a proportion of 50% by weight to 90% by weight, more preferably 60% by weight to 85% by weight, in particular 65% by weight to 80% by weight. %, and binder in a proportion of 1% by weight to 10% by weight, more preferably from 1.2% by weight to 8% by weight, in particular from 1.3% by weight to 3% by weight, in each case based on the total weight of the battery separator, the filler particles having a particle size distribution with a d50 according to ISO 21501-3 of 0.05 µm to 10 µm and a particle size distribution range ((d90-d10) / d50) of 0.1 to 3.5.

The features described in relation to the battery separator according to the invention, in particular the preferred embodiments, can be applied mutatis mutandis to the further battery separator according to the invention.

The advantage of the further battery separator according to the invention is that it contains a high proportion of filler particles in relation to the total weight of the battery separator. This means that the proportion of substrate and binder is comparatively low. This in turn has an advantageous effect on the temperature and pressure stability of the gusset volume.

Another object of the present invention comprises the use of the battery separator according to the invention as a substrate for coating with a lamination binder.

In a preferred embodiment of the invention, the battery separator has a lamination binder on one or both surfaces, preferably selected from the group consisting of polyvinylidene difluoride, polyacrylate, perfluoro-ethylene-propylene, carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene glycol, polyethylene oxide and mixtures and copolymers thereof. Preferred copolymers are copolymers of polyvinylidene difluoride. Preferably the lamination binder is thermoplastic. In this case, the thermoplastic lamination binder preferably has a melting point which is lower than the melting and / or decomposition point of the filler particles and / or, preferably and, of the fiber-based substrate. The lamination binder can also have filler particles, advantageously of the same type as in the coating.

In a preferred embodiment, the area coverage of the battery separator surface with lamination binder is from 0.01 area% to 50 area%, preferably from 5 area% to 35 area%, in particular from 10 area% to 35 area%. The surface coverage can be carried out by means of optical computer-aided evaluation of microscopic images.

The battery separator preferably has the lamination binder with a weight per unit area of 0.1 g / m ² to 5 g / m ² , preferably 0.1 g / m ² to 4 g / m ² , particularly preferably 0.2 g / m ² to 3 g / m ^2, particularly preferably from 0.2 g / m ² to 2 g / m ² and in particular from 0.5 g / m ² to 2 g / m ² . A rather small proportion of lamination binder is advantageous, since with these amounts under normal lamination conditions it does not penetrate into the interstice volume and does not cover the surface of the battery separator over the entire area. Both are advantageous because the ion conductivity of the battery separator is less impaired.

The lamination binder can be applied to the battery separator by various application methods, preferably coating methods, such as in particular knife coating, roller application, engraving coating, application from a slot nozzle. Electro-spinning, spraying, application using electrostatic application methods and / or powdering are also suitable. A drying step can follow after application.

The battery separator provided with the lamination binder can be connected flatly with electrodes. For this purpose, in the first step, a composite of one or more battery separators provided with the lamination binder and one or more electrodes can be produced. The battery separators and electrodes are preferably arranged alternately. Simultaneously with or subsequent to the formation of the composite, the lamination of the composite can take place via activation of the lamination binder, for example by means of pressure, temperature and / or solvents.

In practical tests it has been shown that the battery separator according to the invention is particularly well suited for the loads occurring during lamination due to its high pressure and temperature stability.

The battery separator provided with the lamination binder is suitable for the production of electrode-separator laminates.

Another subject matter of the present invention comprises an electrode-separator unit comprising a battery separator according to the invention and one or more battery electrodes. A battery electrode is understood to be an electrode that has a collector as a conductor for the electrical current and at least one active material as a store for electrical charge.

In a preferred embodiment, the battery separator and one or more battery electrodes are connected to one another by means of a lamination tie. In one embodiment, the lamination binder has been introduced into the electrode-separator unit on the electrode side and, in another embodiment, on the battery separator side.

Preferred battery electrodes include lithium nickel manganese cobalt oxide (NMC), lithium cobalt oxide (LCO), lithium metal phosphates such as, in particular, lithium iron phosphate (LFP), Li manganese oxide spinel (LMS), lithium nickel cobalt aluminum oxide (NCA), lithium and manganese-rich oxides (LMNO) ) and mixtures thereof as active materials. The aforementioned materials are particularly suitable for lamination with the battery separator and are particularly suitable as cathode material.

Preferred battery electrodes include graphite (C), lithium metal (Li), lithium titanium oxide (LTO), silicon (Si) and silicon / carbon composites (Si / C), tin (Sn), zinc (Zn) and mixtures thereof as active materials. The aforementioned materials are also particularly suitable for lamination with the battery separator and are particularly suitable as anode material.

All of the aforementioned electrode materials can also be combined with the battery separator according to the invention without the use of a lamination binder and form an electrochemical cell. The use of the battery separator according to the invention in connection with silicon (Si) and silicon / carbon composite (Si / C) electrodes is particularly advantageous, since these have a large change in volume during a charging / discharging process, which in turn exerts a high pressure on the Exercises battery separator.

Another object of the present invention comprises the use of the battery separator according to the invention as an electrical insulation material in an electrochemical cell.

Suitable electrochemical cells are, for example, Li and / or Na ion batteries, Prussian blue analog electrochemical cells and Li ion capacitors.

Another object of the present invention comprises an electrochemical cell comprising the electrode-separator unit according to the invention and an electrolyte. The electrolyte can contain one or more organic or aqueous, preferably organic solvents, one or more conductive salts and one or more electrolyte additives. Liquid or gel-like electrolytes can be used. The use of the battery separator according to the invention is particularly advantageous when filling the electrochemical cell with the electrolyte, since the large and dimensionally stable gusset volume increases rapidly and enables even distribution of the electrolyte in the electrode-separator unit. This can significantly reduce the production time of the electrochemical cell.

In a preferred embodiment, the electrochemical cell is designed as a rapidly chargeable cell. A cell capable of rapid charging is to be understood as meaning a cell which can be charged at charging rates (C rate) of from 2 to 20 ° C., preferably from 3 ° to 10 ° C., in particular from 4 ° to 8 ° C. Since the cell temperature can increase significantly when they are charged quickly, the battery separator according to the invention is particularly suitable for use in such cells which can be charged quickly due to its thermal stability.

Another advantage of using the battery separator according to the invention for the production of an electrochemical cell is its high temperature stability, which enables quick and easy drying and thus a high process speed. This is particularly advantageous for integrated drying in the cell production process, since water residues can be removed quickly and reliably at high temperatures, e.g. at 170 ° C.

Norms and Methods

Measurement methods:

With regard to the measurement methods, in the present description, unless otherwise stated, reference is made to the version valid on 1.3.2020 or, if no valid version is available at that time, to the most recently valid version.

Weight per unit area:

Based on test specification EN 29073 - T1, 3 100 mm x 100 mm samples are punched out, the samples are weighed and the measured value is multiplied by 100 to determine the basis weights.

Thickness:

The thicknesses are measured in accordance with test specification EN 29073 - T2. The measuring area is ^{2 cm 2} , the measuring pressure is 1000 cN / cm 2.

Particle sizes and distribution:

Execution according to standard ISO 21501-2: 2019-11, without ultrasound treatment. Evaluation of the measured light scattering using the Mie theory.

Porosity:

Hierbei entspricht die δ_Rohdichte der mittels Flächengewicht und Dicke berechneten Dichte des Separators.The porosities (P) in% are calculated according to the following formula: $$\text{P.}=\left(1-\left({\mathrm{\delta }}_{\text{Bulk density}}/{\mathrm{\delta }}_{\text{Density}}\right)\right)*100.$$

Here, the δ _{bulk density} corresponds to the density of the separator calculated using the basis weight and thickness.

The δ _{true density} corresponds to the mean density δ _{mean of} the materials used according to their weight proportion in the separator, assuming 0% porosity. The mean density can be calculated from the relative weight of the coating substrate, the relative weight of the coating layer and the coating composition.

Gusset volume:

The gusset volume is determined according to ASTM D7854-16.

Pore size:

The pore size of the substrate, such as the mean pore size, is measured according to the invention in accordance with ASTM F 316.

Gurley air permeability:

The air permeability is determined according to ISO 5636-3.

Shrinkage:

To determine the area shrinkage, 100 mm × 100 mm samples are punched out and stored for one hour at 150 ° or 200 ° C. in a laboratory dryer from Mathis. The area shrinkage of the samples is then determined.

Tensile strength:

The maximum tensile force (HZK) of the materials is determined in accordance with EN 29073 T3.

Melting point:

Melting points and glass points are after DIN 53765 (1994-03) certainly.

C rate:

The "C-rate" is a term used to specifically describe the charging and discharging process of a battery, regardless of its capacity in Ah and the flowing currents in amperes. A discharge rate of “1C” means that the battery will be completely discharged within one hour. A discharge rate of "2C" corresponds to a discharge within half an hour; the discharge rate of "10C" corresponds to a discharge within six minutes.

Examples

The invention is explained in more detail below with the aid of several examples.

Example 1 - Manufacture of several inventive battery separators and comparative battery separators

Coating solution 1 (B1):

5 parts of a particulate binder dispersion (solids content = 25%), 10 parts of dissolved binder (20% solids content) and 38 parts of deionized water added with stirring. The solution was stirred for 2 hours and tested for stability for at least 24 hours. The viscosity of the solution obtained was 80 mPa * s.

Coating solution 2 (B2):

4.3 parts of a particulate binder dispersion (solids content = 25%) and 12.3 parts of dissolved binder were added to 148.5 parts of a 65% strength aluminum oxide dispersion (AI203) (d50 = 0.45 μm, SPAN = 1.62) (20% solids content) and 38 parts of deionized water were added with stirring. The solution was stirred for 2 hours and tested for stability for at least 24 hours. The viscosity of the solution obtained was 50 mPa * s.

Comparative coating solution 1 (VB1):

15 parts of a particulate binder dispersion (solids content = 50%), 10 parts of dissolved binder (10% solids content) and 38 parts of deionized water added with stirring. The solution was stirred for 2 hours and tested for stability for at least 24 hours. The viscosity of the solution obtained was 61 mPa * s,

Comparative coating solution 2 (VB2):

20 parts of a particulate binder dispersion (solids content = 50%), 6.5 parts of dissolved binder (20%) were added to 136 parts of a 65% strength aluminum oxide dispersion (AI203) (d50 = 0.58 µm, SPAN = 3.8) Solids content) and 47 parts of deionized water were added with stirring. The solution was stirred for 2 hours and tested for stability for at least 24 hours. The viscosity of the solution obtained was 140 mPa * s,

Example 1A

An 80 cm wide, wet-laid PET nonwoven (thickness: 17 μm, weight per unit area: 8 g / m 2) was continuously coated with coating solution 1 by means of a roller coating process and dried at a temperature gradient of 125 ° C. to 165 ° C.

A coated nonwoven fabric with a weight per unit area of 33 g / m 2 and a thickness of 22 μm was obtained. The mean pore size (MFP) of the coated nonwoven was 0.35 μm. The Gurley value (100 ml) was 98 seconds.

Example 1B

An 80 cm wide, wet-laid PET nonwoven (thickness: 15 μm, weight per unit area: 6 g / m 2) was continuously coated with coating solution 1 by means of a roller coating process and dried at a gradient from 125 ° C. to 160 ° C.

A coated nonwoven fabric with a weight per unit area of 27 g / m 2 and a thickness of 19 μm was obtained. The mean pore size (MFP) of the coated nonwoven was 0.4 μm. The Gurley value was 75 seconds (100 ml).

Example 2A

An 80 cm wide, wet-laid PET nonwoven (thickness: 15 μm, weight per unit area: 8 g / m 2) was continuously coated with coating solution 2 by means of a roller coating process and dried at a gradient of 125 ° C. to 165 ° C.

A coated nonwoven fabric with a weight per unit area of 33 g / m 2 and a thickness of 23 μm was obtained. The mean pore size (MFP) of the coated nonwoven was 0.4 μm. The Gurley value was 90 seconds (100 ml).

Example 2B

An 80 cm wide, wet-laid PET nonwoven (thickness: 17 μm, weight per unit area: 9 g / m 2) was continuously coated with coating solution 2 by means of a roller coating process and dried at a gradient of 125 ° C. to 165 ° C.

A coated nonwoven fabric with a weight per unit area of 35 g / m 2 and a thickness of 26 μm was obtained. The mean pore size (MFP) of the coated nonwoven was 0.33 μm. The Gurley value was 100 seconds (100 ml).

Example 3A Laminatable Battery Separator.

An 80 cm wide battery separator (Example 1A) was continuously coated with a 10% PVDF dispersion by means of a roller coating process and dried at 135.degree.

A coated battery separator with a basis weight of 35 g / m 2 and a thickness of 23 μm was obtained. The mean pore size (MFP) of the coated nonwoven was 0.35 μm. The Gurley value was 110 seconds (100 ml).

Comparative example 1 (CE1A)

An 80 cm wide, wet-laid PET nonwoven (thickness: 19 μm, weight per unit area: 10 g / m 2) was continuously coated with comparative coating solution VB1 by means of a roller coating process and continuously dried with a gradient of 125 ° C. to 165 ° C.

A coated nonwoven fabric with a weight per unit area of 34 g / m 2 and a thickness of 26 μm was obtained. The Gurley value was 360 seconds (100 ml).

Comparative example 2 (CE2A)

An 80 cm wide, wet-laid PET nonwoven (thickness: 19 μm, weight per unit area: 10 g / m 2) was continuously coated with comparative coating solution VB2 by means of a roller coating process and continuously dried with a gradient of 125 ° C. to 165 ° C.

A coated nonwoven fabric with a weight per unit area of 32 g / m 2 and a thickness of 29 μm was obtained. The Gurley value was 652 seconds (100 ml).

Example 2 - Measurement of Relevant Physical Properties

Table 1. Summary of the results of the separator manufacture. Surname SPAN Particle size (d50) [µm] Thickness [µm] Weight [g / m ² ] Gurley [sec / 100 ml] Pore size [µm] HZK in md [N / 5cm] Strain [%] Example 1A 1.5 0.45 22nd 33 98 0.35 26th 12th Example 1B 1.5 0.45 19th 27 75 0.4 19th 10 Example 2A 1.62 0.45 23 33 90 0.4 28 11 Example 2B 1.62 0.45 26th 35 100 0.33 39 14th Example 3A 1.5 0.45 23 35 110 0.35 30th 12th VB1A 7.8 0.5 26th 34 360 0.2 37 14th VB2A 3.8 0.58 29 32 652 0.16 40 12th

It can be seen from Table 1 that Examples 1A to 3A according to the invention have pore size distributions in the range from 0.25 μm to 0.5 μm and weights per unit area which are in some cases higher than those of the comparative examples, with a simultaneously lower thickness and lower Gurley Values. This shows that the coating solutions with SPAN values of 0.1 and up to 3.5, compared with the comparison coating solutions with larger SPAN values, result in an advantageous interstice volume for the porosity and thus the ion conductivity.

Example 3 - Cell Characterization

Various electrochemical cells are produced from the battery separators produced in Example 1.

Unless otherwise specified, all work is carried out in a glove box. The separators are dried in vacuo at 150 ° C. for 24 hours. The electrodes are dried in vacuo at 80 ° C. for 24 hours. NMC 111 (Al arrester) is used as the cathode and graphite (Cu arrester) as the anode. The capacity of the cathode is approx. 72 mAh. The electrolyte is LP50 (800 µL).

Unlaminated cells:

Using the battery separators 1A, 2A, 1B, 2B, VB1A, VB2A, 3-layer structures, each consisting of anode, separator and anode, are produced. These are welded into pouch films, one side being left open. Open cells are obtained. 800 µL of electrolyte is slowly added to the composite electrode-separator and the fourth side of the cells is sealed. After 24 hours, the cells are opened at one point, a vacuum is drawn and the cells are then closed again.

Laminated cell (from 3A).

Anode, separator and cathode are laminated together at 160 ° C and a pressure of 3 bar. The laminate is then transferred to a glove box and dried at 120 ° C. for 24 hours. The rest of the procedure corresponds to that previously described under "Unlaminated cells".

Formation of cells:

• • Laden(CC) mit 0,1C bis 4,2 Volt
• • Pause: 2 min
• • Laden (CV) bei 4,2 V bis I < 0,02C
• • Pause: 2 min
• • Entladen mit 0,1 C bis 3.0V Wiederholen des Ladezyklus

Charging cycle:

• • Charge (CC) with 0.1C to 4.2 volts
• • Break: 2 min
• • Charging (CV) at 4.2 V to I <0.02C
• • Break: 2 min
• • Discharge with 0.1 C to 3.0V Repeat the charging cycle

Cell tests:

Life tests of the cells:

The formed cells are charged and discharged in CCCV mode with 1C (3V / 4.2V).

The results of the life tests are in 1 shown. It is found that the cells manufactured with the battery separators according to the invention, and in particular the cells with 1A, 2A and 1B, have a higher cycle stability and a longer service life than the comparative examples.

It is particularly noteworthy that the cell manufactured with the battery separator 3A according to the invention shows such a good service life because it was laminated onto the electrodes with pressure.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 3357114 A4 [0006]
• EP 2750216 B1 [0007]
• EP 2924781 A1 [0008]
• EP 3244475 A1 [0008]

Non-patent literature cited

• DIN EN ISO 9092 (2018-02) [0011]
• ISO 21501-3 (2019-11) [0011]
• DIN EN 29073-3 (1992-08) [0076, 0077]
• DIN 53765 (1994-03) [0114]

Claims (21)

Battery separator with a, preferably open-pore, substrate, in particular a nonwoven fabric in accordance with DIN EN ISO 9092 (2018-02) as the base body, the base body having a coating containing filler particles in a proportion of 80% by weight to 98% by weight and binder in a proportion of 2% by weight to 10% by weight, based in each case on the coating weight, characterized in that the filler particles have a particle size distribution with a d50 according to ISO 21501-3 of 0.05 µm to 10 µm and a particle size distribution range (( d90-d10) / d50) from 0.05 to 3.5. Battery separator after Claim 1 , characterized in that the filler particles have a particle size distribution with a d50 value (measured according to ISO 21501-3) of 0.05 µm to 2 µm, more preferably from 0.1 µm to 1 µm, in particular from 0.3 µm to 0, 5 µm. Battery separator after Claim 1 or 2 , characterized in that the filler particles have a particle size distribution range ((d90-d10) / d50) from 0.1 to 3.5, preferably from 0.1 to 3.0, even more preferably from 0.2 to 3.0, even more preferably from 0.2 to 2.5, more preferably from 1.0 to 2.5, even more preferably from 1.2 to 2.5, in particular from 1.2 to 2.0. Battery separator according to one or more of the preceding claims, characterized in that the battery separator has volume elements which in their z-direction consist essentially only of filler particles and the gusset volumes formed therefrom. Battery separator according to one or more of the preceding claims, characterized in that the battery separator has a pore size distribution with an average pore size, measured according to DIN ISO 4003: 1990, of 0.01 µm to 1.5 µm, preferably 0.1 µm to 0, 5 µm and in particular from 0.25 µm to 0.5 µm. Battery separator according to one or more of the preceding claims, characterized in that the battery separator has a gusset volume of 25% by volume to 75% by volume, more preferably from 40% by volume to 70% by volume and in particular from 45% by volume to 65% by volume .% having. Battery separator according to one or more of the preceding claims, characterized in that the substrate is an open-pore substrate, preferably paper, woven, knitted and / or crocheted fabrics, a foam, a membrane, a film, in particular a stretched film, perforated film, track-etched film, mechanically or laser-perforated film, micro-lithographed film, particularly preferably an open-pore fiber-based substrate, even more preferably a nonwoven, in particular a wet-laid nonwoven. Battery separator after Claim 7 , characterized in that the fibers of the fiber-based substrate contain polyester. Battery separator after Claim 7 or 8th , characterized in that the fibers of the fiber-based substrate have an average titer of 0.06 dtex to 3.3 dtex, preferably 0.06 dtex to 1.7 dtex, preferably 0.06 dtex to 1.0 dtex. Battery separator according to one or more of the preceding claims, characterized in that the filler particles are inorganic particles, in particular selected from the group consisting of aluminum oxide, aluminum oxide hydroxide, silicon oxide, aluminosilicates, zeolites, zirconium oxide, titanium dioxide, magnesium oxide and mixtures thereof. Battery separator according to one or more of the preceding claims, characterized in that the Mohs hardness of the filler particles is 2 Mohs to 10 Mohs, more preferably 5 Mohs to 10 Mohs and in particular 7 Mohs to 9 Mohs. Battery separator according to one or more of the preceding claims, characterized in that the filler particles in a proportion of 80% by weight to 98% by weight, more preferably 90% by weight to 98% by weight, in particular from 92% by weight to 97% by weight % By weight based on the total weight of the coating. Battery separator according to one or more of the preceding claims, characterized in that the coating contains the binder in a proportion of 2% by weight to 20% by weight, more preferably of 2% by weight to 8% by weight, in particular from 3% by weight to 7% by weight, based on the total weight of the coating. Battery separator according to one or more of the preceding claims, characterized in that the binder is present as a mixture of binder particles and binder which was applied in the form of a solution or dispersion. Battery separator according to one or more of the preceding claims, characterized by a thickness, according to DIN EN 29073 - T2, from 3 µm to 70 µm, more preferably from 5 µm to 30 µm, in particular from 8 µm to 25 µm. Battery separator according to one or more of the preceding claims, characterized by a temperature stability of up to 150 ° C, more preferably up to 170 ° C, particularly preferably up to 200 ° C, and / or a pressure stability of up to 0.3 MPa , preferably of up to 2.5 MPa, even more preferably of up to 5.0 MPa, very particularly preferably of up to 15 MPa, and / or pressing force stability of up to 500 N, preferably of up to 1500 N, particularly preferably of up to 4000 N. Electrode separator unit comprising a battery separator according to one or more of the preceding claims, and one or more battery electrodes. Electrode separator unit Claim 17 , characterized in that the battery separator and one or more battery electrodes are connected to one another by means of a lamination tie. Use of a battery separator according to one or more of the Claims 1 until 16 as electrical insulation material in an electrochemical cell. Use of a battery separator according to one or more of the preceding claims as a substrate for coating with a lamination binder. Electrochemical cell comprising an electrode-separator unit according to Claim 17 or 18th and an electrolyte, preferably a liquid or gel-like electrolyte.

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