EP1673822A2

EP1673822A2 - Ceramic separator for electrochemical cells with improved conductivity

Info

Publication number: EP1673822A2
Application number: EP04766544A
Authority: EP
Inventors: Volker Hennige; Christian Hying; Gerhard HÖRPEL
Original assignee: Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2003-10-14
Filing date: 2004-08-19
Publication date: 2006-06-28
Also published as: JP2007508670A; DE10347566A1; KR20070019952A; WO2005038946A2; WO2005038946A3; CN1868077A; US20080248381A1

Abstract

Disclosed is a separator for an electrochemical cell, comprising a flexible, broken support with a ceramic coating which is provided in said support and contains 75 to 99 ppm of oxide particles, selected among ZrO2, SiO2, and Al2O3 particles, and 1 to 25 ppm of zeolite particles. The inventive separators have a significantly improved ion conductivity after being filled with an electrolyte and are to be used especially as separators in lithium-ion batteries.

Description

Ceramic separator for electrochemical cells with improved conductivity

The present invention relates to a separator for an electrochemical cell, a method for producing such a separator and an electrochemical cell which comprises such a separator.

In this description, electrochemical cell or battery is to be understood to mean batteries and accumulators (secondary batteries) of all types, in particular alkali, such as e.g. Lithium, lithium ion, lithium polymer, and alkaline earth batteries and accumulators, including in the form of high-energy or high-performance systems.

Electrochemical cells comprise electrodes with opposite poles, which are separated from one another by a separator while maintaining ion conductivity.

Conventionally, a separator is a thin, porous, electrically insulating material with high ion permeability, good mechanical strength and long-term stability against those in the system, e.g. B. in the electrolyte of the electrochemical cell, chemicals and solvents used. It is intended to completely electronically isolate the cathode from the anode in electrochemical cells. He must also be permanently elastic and the movements in the system, for. B. in the electrode package when loading and unloading, follow.

The separator largely determines the life of the arrangement in which it is used, e.g. B. that of an electrochemical cell. The development of rechargeable electrochemical cells or batteries is therefore influenced by the development of suitable separator materials. General information about electrical separators and batteries can e.g. B. at J.O. Besenhard can be found in the "Handbook of Battery Materials" (NCH-Nerlag, Weinheim 1999).

High-energy batteries are used in various applications where it is important to have the largest possible amount of electrical energy available. This is the case for example with traction batteries but also with Νot power supply with batteries (Auxillary Power Systems). The energy density is often expressed in weight [Wh / kg] or in volume-related [Wh / L] sizes. Energy densities of 350 to 400 Wh / L and 150 to 200 Wh / kg are currently being achieved in high-energy batteries. The requested performance with such batteries is not so large, so that one can make compromises with regard to the internal resistance. This means that the conductivity of the electrolyte-filled separator, for example, does not have to be as great as that of high-performance batteries, so that other separator concepts are also possible.

For example, polymer electrolytes can be used in high-energy systems, which have a very low conductivity of 0.1 to 2 mS / cm. Such polymer electrolyte cells cannot be used as high-performance batteries.

Separator materials for use in high-performance battery systems must have the following properties:

They have to be as thin as possible to ensure a small specific space requirement and to keep the internal resistance low. To ensure these low internal resistances, it is important that the separator also has a large porosity. They must also be light in order to achieve a low specific weight. In addition, the wettability must be high, otherwise dead zones that are not wetted will arise.

In many, especially mobile applications, very large amounts of energy are required (e.g. in traction batteries). The batteries in these applications therefore store large amounts of energy when fully charged. The separator must be safe for this, since very large amounts of electrical energy are transported in these batteries. In the event of a malfunction of the battery, e.g. Overcharge or short circuit, or not released in an uncontrolled manner in an accident, as this would inevitably lead to the explosion of the cell with the appearance of fire.

Currently used separators consist mainly of porous organic polymer films or inorganic nonwovens such as. B. nonwovens made of glass or ceramic materials or ceramic papers. These are made by different companies. Important producers are: Celgard, Tonen, Übe, Asahi, Binzer, Mitsubishi, Daramic and others. The separators made of inorganic nonwovens or ceramic paper are mechanically very unstable and easily lead to short circuits, so that a long service life cannot be achieved.

A typical organic separator is e.g. B. made of polypropylene or a polypropylene / polyethylene / polypropylene composite. A major disadvantage of these organic polyolefin separators is their low thermal resistance of below 150 ° C. A short-lasting reaching of the melting point of these polymers leads to a large melting of the separator and to a short circuit in the electrochemical cell which uses such a separator. The use of such separators is therefore generally not safe. Because when higher temperatures are reached, in particular above 150 ° C or even 180 ° C, these separators are destroyed.

In order to overcome these disadvantages, there were first attempts to use inorganic composite materials as separators. In DE 198 38 800 Cl an electrical separator with a

Composite structure proposed, which comprises a flat, provided with a plurality of openings, flexible substrate with a coating thereon. The material of the

Substrate is selected from metals, alloys, plastics, glass and carbon fiber or a combination of such materials, and the coating is a continuous, porous, electrically non-conductive ceramic coating. The use of ceramic

Coating promises thermal and chemical resistance. The separators, the one

Carriers or a substrate made of electrically conductive material (as indicated in the example), however, have proven to be unsuitable for electrochemical cells, since the coating of the thickness described cannot be produced without defects over a large area. Short circuits are therefore very easy. In addition, metal meshes as thin as are required for very thin separators are not commercially available.

In previous work (DE 101 42 622) it could be shown that with a material which comprises a flat, flexible substrate provided with a plurality of openings with a coating on and in this substrate, the material of the substrate being selected from woven or non-woven, non-electrically conductive fibers of glass or ceramic or a combination of such materials and the coating a porous, is electrically insulating, ceramic coating, and wherein the resulting separator has a thickness of less than 100 microns and is bendable, a separator can be produced that has a sufficiently low resistance in connection with the electrolyte and nevertheless has a sufficiently large long-term resistance. Although the separator described in DE 101 42 622 has a very high conductivity, the separator described there still does not meet the requirements for a separator that can be used technically in terms of thickness and weight, as well as safety.

In DE 102 08 277, the weight and the thickness of the separator were reduced by using a polymer fleece, but the embodiments of a separator described there also do not yet meet all the requirements for a separator for a lithium high-energy battery, in particular because in this application Particular importance was attached to the largest possible pores in the separator. With the particles up to 5 μm in size described there, however, it is not possible to produce separators with a thickness of 10 to 40 μm, since only a few particles would lie one above the other. As a result, the separator would inevitably have a high density of defects and defects (e.g. holes, cracks, ...).

In the not yet published application DE 102 55 122, the pores of the ceramic coating with fine particles were selected from SiO ₂ , Al ₂ O ₃ , ZrO ₂ , SiC, Li ₂ CO ₃ , Li ₃ N, LiAlO to increase the service life of the separators ₂ , or Li _x Al _y Ti _z (PO ₄ ) ₃ equipped with 1 <x <2, 0 <y <1 and 1 <z <2. This measure has improved the long-term stability of such separators. However, there is still room for improvement with regard to the ion conductivity of ceramic or semi-ceramic separators.

The present invention was therefore based on the object of providing a separator for an electrochemical cell which has a further improved ion conductivity and is therefore particularly suitable, in particular, for high-performance lithium batteries.

Surprisingly, it was found that ceramic separators can be replaced by replacing at least some of the oxides usually used as ceramic particles, e.g.

Al ₂ O ₃ , SiO ₂ or ZrO _2, a significant increase in the conductivity of the separator impregnated with the electrolyte can be achieved by zeolite particles. Why the exchange At least some of the ceramic particles caused by zeolite particles lead to this increase. It has not yet been possible to clarify them without any doubt.

In DE 100 55 612 and WO 02/38259 membranes based on ceramic-coated carrier materials, such as e.g. Nonwovens or woven fabrics made of polyamides which had zeolites as separating layers. Separators are not described there. In the systems described there, the separation-active layer is also produced in a very complex manner by synthesizing the zeolites within the membrane.

The present invention therefore relates to a separator for electrochemical cells, in particular a battery separator, comprising a porous carrier which has woven or non-woven polymer fibers, with a porous inorganic, non-electrically conductive coating located on and in this carrier, composed of one another by an inorganic adhesive and particles bonded to the carrier with an average particle size of 0.5 to 10 μm, which is characterized in that the inorganic coating comprises 75 to 99 parts by mass of one or more oxide particles of the elements Al, Si and / or Zr with an average Has particle size of 0.5 to 10 microns and has from 1 to 25 parts by mass of particles with an average particle size of 0.5 to 10 microns at least one zeolite.

The present invention also relates to a method for producing a separator according to the invention, which is characterized in that a support which has woven or non-woven polymer fibers is provided with a ceramic coating, for which purpose a suspension is applied to and in the support and this is carried out by heating at least once on and in the carrier is solidified, the suspension having a sol and at least two fractions of particles, of which the first fraction oxide particles with an average particle size of 0.5 to 10 μm, selected from the oxides of the elements Al, Zr and / or Si and is present in a proportion of 75 to 99 parts by mass and of which the second fraction has zeolite particles with an average particle size of 0.5 to 10 μm and is present in a proportion of 1 to 25 parts by mass.

The present invention also relates to the use of a separator according to the invention as a separator in batteries and batteries, in particular Lithium-ion batteries which have a separator according to the invention.

The separators according to the invention have the advantage that separators equipped with zeolites in this way are distinguished by comparable porosities, pore sizes, Gurley numbers, etc. as the separators known from the prior art, but the MacMullin numbers are significant, by up to a factor of 2 , are elevated. A high McMullin number also means a high ion conductivity.

The separator according to the invention and a method for its production are described in the following, without the invention being restricted to these embodiments.

The separator for electrochemical cells according to the invention comprises a porous carrier which has woven or non-woven polymer fibers, with a porous inorganic, non-electrically conductive coating located on and in this carrier, made of particles with an average particle size bonded to one another and to the carrier by means of an inorganic adhesive from 0.5 to 10 μm, is characterized in that the inorganic coating has from 75 to 99 parts by mass, preferably from 80 to 90 parts by mass, of one or more oxide particles of the elements Al, Si and / or Zr with an average particle size of 0 , 5 to 10 microns and from 1 to 25 parts by mass, preferably 10 to 20 parts by mass of particles with an average particle size of 0.5 to 10 microns at least one zeolite. If the 25 parts by mass of zeolite particles are exceeded, the mechanical properties of the separators deteriorate, so that they can no longer be used sensibly in batteries.

The zeolite particles present in the separator can have the zeolites in the H ⁺ , Na ⁺ or Li ⁺ form. In principle, all known zeolites can be used as zeolites. Preferably the less hydrophobic types are present in the inorganic coating. Particles selected from the zeolites zeolite-A, zeolite-Y or zeolite-USY are preferably present in the separator according to the invention as zeolite particles. Table 1 below shows some material data for zeolites from Degussa AG (Wessalith P) and the Zeolyst (CBNxxxx). However, other zeolites known from the prior art can also be used. Table 1: Some zeolites with selected material data

Molar ratio The separators according to the invention preferably have supports which are flexible and preferably have a thickness of less than 50 μm. The flexibility of the carrier ensures that the separator according to the invention can also be flexible. Such flexible separators are more versatile, e.g. B. in so-called winding cells. The thickness of the carrier has a great influence on the properties of the separator, since on the one hand the flexibility but also the surface resistance of the separator impregnated with electrolyte depends on the thickness of the carrier.

The separator according to the invention therefore preferably has carriers which have a thickness of less than 30 μm, particularly preferably less than 20 μm. In order to be able to achieve a sufficiently high performance of the batteries, particularly in the case of lithium ion batteries, it has proven to be advantageous if the separator according to the invention has a carrier which preferably has a porosity of greater than 40%, preferably from 50 to 97%, particularly preferably from 60 to 90% and very particularly preferably from 70 to 90%. The porosity is defined as the volume of the carrier (100%) minus the volume of the fibers of the carrier, i.e. the proportion of the volume of the carrier that is not filled by material. The volume of the carrier can be calculated from the dimensions of the carrier. The volume of the fibers results from the measured weight of the fleece under consideration and the density of the fibers, in particular the polymer fibers. In a further embodiment of the invention, the carrier is a fleece with a pore size of 5 to 500 μm, preferably 10 to 200 μm.

The porous (openwork) support preferably has woven or non-woven polymer fibers. The carrier particularly preferably has a polymer fabric or nonwoven or is such a fabric or nonwoven. As the polymer fibers, the carrier preferably has non-electrically conductive fibers of polymers, which are preferably selected from polyacrylonitrile (PAN), polyamide, (PA), polyester, such as, for. B. polyethylene terephthalate (PET) and / or polyolefin (PO), such as. B. polypropylene (PP) or polyethylene (PE) or mixtures of such polyolefins. If the perforated support comprises polymer fibers, polymer fibers other than those mentioned above can also be used, provided that they both have the temperature stability required for the production of the separators and are stable under the operating conditions in an electrochemical cell, preferably a lithium battery. In a preferred embodiment, the separator according to the invention has polymer fibers which have a softening temperature of greater than 100 ° C. and a melting temperature of greater than 110 ° C. The carrier can comprise fibers and / or filaments with a diameter of 0.1 to 150 μm, preferably 1 to 20 μm, and / or threads with a diameter of 3 to 150 μm, preferably 10 to 70 μm. If the carrier has polymer fibers, these preferably have a diameter of 0.1 to 10 μm, particularly preferably 1 to 5 μm. Particularly preferred flexible nonwovens, in particular polymer nonwovens, have a basis weight of less than 20 g / m ² , preferably 5 to 15 g / m ² . In this way, a particularly small thickness and high flexibility of the carrier is guaranteed.

The separator according to the invention particularly preferably has a polymer fleece as carrier which has a thickness of less than 30 μm, preferably a thickness of 10 to 20 μm. A particularly homogeneous pore radius distribution in the nonwoven is particularly important for use in a separator according to the invention. A most homogeneous pore radius distribution in the nonwoven in conjunction with optimally coordinated oxide particles of a certain size leads to an optimized porosity of the separator according to the invention.

The inorganic adhesive in the separator according to the invention is preferably selected from oxides of the elements Al, Si and / or Zr. The inorganic adhesive can contain particles with a have an average particle size of less than 20 nm and have been produced via a particulate sol or have an inorganic network of the oxides which has been produced via a polymeric sol.

It can be advantageous if the separator according to the invention additionally has an inorganic, silicon-containing network, the silicon of the network being bound to the oxides of the inorganic coating via oxygen atoms and to the carrier having polymer fibers via an organic residue. Such a network is obtained if an adhesion promoter is used in the manufacture of the separator and this adhesion promoter is subjected to the thermal treatment customary in the manufacture.

The separator according to the invention preferably has and in the carrier a porous, electrically insulating, inorganic coating which has oxide particles of the elements Al, Si and / or Zr with an average particle size of preferably 1 to 4 μm. The separator according to the invention likewise preferably has zeolite particles with an average particle size of 1 to 5 μm. The particles are particularly preferably bonded to an oxide of the metals Zr or Si. The ceramic material of the separator according to the invention formed by the particles and the inorganic adhesive preferably has an average pore size in the range from 50 nm to 5 μm and preferably from 100 to 1000 nm.

The separators according to the invention can be bent without damage, preferably to any radius down to 100 m, preferably to a radius of 100 m to 50 mm and very particularly preferably to a radius of 50 mm to 2 mm. The separators according to the invention are also distinguished by the fact that they can have a tear strength of at least 1 N / cm, preferably of at least 3 N / cm and very particularly preferably of more than 6 N / cm. The high tensile strength and the good bendability of the separator according to the invention has the advantage that changes in the geometries of the electrodes which occur during charging and discharging of a battery can be carried out by the separator without the latter being damaged. The flexibility also has the advantage that this separator can be used to produce commercially standardized winding cells. In these cells, the electrode / separator layers are wound up in a spiral in standardized size and contacted. The separator according to the invention preferably has a porosity of 30 to 80%. The porosity relates to the attainable, i.e. open, pores. The porosity can be determined using the known method of mercury porosimetry or can be calculated from the volume and density of the feedstocks used if it is assumed that there are only open pores.

The separators according to the invention preferably have a thickness of less than 50 μm, preferably less than 40 μm, particularly preferably a thickness of 5 to 30 μm and very particularly preferably a thickness of 15 to 25 μm. The thickness of the separator has a great influence on the properties of the separator, because on the one hand the flexibility but also the surface resistance of the separator soaked with electrolyte depends on the thickness of the separator. The low thickness results in a particularly low electrical resistance of the separator when used with an electrolyte. The separator itself, of course, has a very high electrical resistance, since it must itself have insulating properties. In addition, thinner separators allow an increased packing density in a battery stack, so that a larger amount of energy can be stored in the same volume.

The separator of the present invention is outstandingly suitable for high-capacity and high-capacity electrochemical cells due to its configuration according to the invention

Energy density. In particular, the separator according to the invention is suitable for electrochemical cells which are based on the transfer of alkali and / or alkaline earth metal ions, such as e.g. Lithium metal and lithium ion batteries. Therefore, it is advantageous if this

Separators also show the protective measures specific to these applications, such as the interruption property and short-circuit property with a high short-circuit temperature. Interrupting property or "shut-down" is to be understood as a measure in which easily separable substances, such as, for example, thermoplastic plastics, can be incorporated into the separator for specific operating temperatures. If the operating temperature rises due to faults such as overloading, external or internal short circuits, such easily melting substances can melt and clog the pores of the separator. The ion flow through the separator is thus partially or completely blocked and a further rise in temperature is prevented. Short-circuit property or melt-down means that the separator melts completely at a short-circuit temperature. A contact and a short circuit can then occur between large areas of the electrodes of an electrochemical cell. For a safe operation of an electrochemical cell with a high capacity and energy density, the highest possible short-circuit temperature is desirable. The separator according to the invention has a significant advantage. This is because the ceramic material which adheres to the perforated carrier in the separator of the present invention has a melting point which is far above the safety-relevant temperature range for electrochemical cells. The separator of the present invention therefore has superior safety.

Polymer separators, for example, provide the security currently required for lithium batteries by preventing any current transport through the electrolyte above a certain temperature (the shutdown temperature, which is around 120 ° C). This happens because the pore structure of the separator collapses at this temperature and all pores are closed. Because no more ions can be transported, the dangerous reaction that can lead to the explosion comes to a standstill. If the cell is heated further due to external circumstances, the melt-down temperature is exceeded at approx. 150 to 180 ° C. From this temperature, the separator melts and contracts. At many points in the battery cell there is now a direct contact between the two electrodes and thus a large internal short circuit. This leads to an uncontrolled reaction, which often ends with an explosion of the cell, or the pressure that is created is often reduced by fire through a pressure relief valve (a rupture disc).

In the context of the present invention, the flexible, openwork carrier of the separator comprises polymer fibers. With this hybrid separator, which has inorganic components and polymeric carrier material, there is a shutdown when the high temperature causes the polymer structure of the carrier material to melt and penetrate into the pores of the inorganic material, thereby closing it. In contrast, there is no so-called meltdown (breakdown) in the separator according to the invention. The separator according to the invention thus fulfills the requirements for one of several Battery shutdowns required by battery manufacturers due to the shutdown in the battery cells. The inorganic particles ensure that there can never be a meltdown. This ensures that there are no operating states in which a large-scale short circuit can occur.

Even in the event of an internal short circuit, e.g. B. was caused by an accident, the separator according to the invention is very safe. Would z. Depending on the separator, the following happens, for example, when drilling a nail through a battery: The polymer separator would melt and contract at the point of penetration (a short-circuit current flows over the nail and heats it up). As a result, the short circuit point becomes larger and the reaction gets out of control. In the embodiment with the hybrid separator according to the invention, at most the polymeric substrate material melts, but not the inorganic separator material. The reaction inside the battery cell after such an accident is much more moderate. This battery is therefore significantly safer than one with a polymer separator. This is particularly important in the mobile area.

It can be advantageous if the separator has an additional non-inherent shutdown mechanism. This can e.g. B. can be realized in that a very thin wax or polymer particle layer of so-called shutdown particles, which melt at a desired shutdown temperature, is present on or in the separator. Particularly preferred materials from which the shutdown particles can consist are, for example, natural or artificial waxes, low-melting polymers, such as. B. polyolefins, wherein the material of the shutdown particles is selected so that the particles melt at the desired shutdown temperature and close the pores of the separator, so that a further ion flow is prevented.

The shutdown particles preferably have an average particle size (D _w ) which is greater than or equal to the average pore size (d _s ) of the pores of the porous inorganic layer of the separator. This is particularly advantageous because it prevents the pores of the separator layer from penetrating and closing, which would result in a reduction in the pore volume and thus in the conductivity of the separator and also in the performance of the battery. The thickness of the switch-off particle layer is only critical if the layer is too thick Resistance in the battery system would increase unnecessarily. In order to achieve a safe shutdown, the shutdown particle layer should have a thickness (z _w ) that is approximately equal to the average particle size of the shutdown particles (D _w ) up to 10 D _w , preferably from 2 D _w to D _w . A separator equipped in this way has a primary safety feature. In contrast to the purely organic separator materials, this separator cannot melt completely and therefore there can be no meltdown. These safety features are very important due to the very large amounts of energy for high-energy batteries and are therefore often required.

In a further variant of the separator according to the invention, the inorganic coating, which has oxide particles of the elements Al, Si and / or Zr with an average particle size of 0.5 to 10 μm and zeolite particles, has a porous shutdown layer made of one material , which melts at a predetermined temperature and closes the pores of the inorganic layer, the shutdown layer being formed by a porous sheet.

In principle, it is possible for the shutdown layer to be present on both sides of the separator. However, it has proven to be advantageous if the switch-off layer is only present on one side of the separator according to the invention. A single shutdown layer is sufficient to ensure safe shutdown when necessary.

The switch-off layer according to the invention on the inorganic layer can, for example, from natural or artificial waxes, (low-melting) polymers, such as. B. special polyolefins such. B. polyethylene or polypropylene, or polymer blends or mixtures, the material of the shutdown layer is selected so that the shutdown layer melts at the desired shutdown temperature and closes the pores of the separator, so that a further ion flow is prevented. Preferred materials for the switch-off layer are those materials which have a melting point of less than or equal to 180 ° C., preferably less than 130 ° C. The use of materials that cause the shutdown at relatively low temperatures can melt or ignite the materials surrounding the batteries, such as. B. Avoid housings or cables as much as possible. The separator according to the invention particularly preferably has a Switch-off layer made of polyethylene (wax).

The thickness of the switch-off layer is in principle arbitrary as long as it is ensured that a reduction in the ion flow and thus in the conductivity of the separator, which would result in a reduction in the performance of the battery, is prevented. The thickness of the shutdown layer is only critical insofar as a layer that is too thick would unnecessarily increase the resistance in the battery system. In order to achieve a safe shutdown, the shutdown layer should have a thickness of 1 to 20 μm, preferably 5 to 10 μm. It can be advantageous if the material of the switch-off layer and at least parts of the material of the carrier are identical. The porosity of the shutdown layer is 20 to 80% and preferably 40 to 60%.

The separators according to the invention are preferably produced by the method according to the invention for producing a separator, which is characterized in that a carrier which has woven or non-woven polymer fibers is provided with a ceramic coating, for which purpose a suspension is applied to and in the carrier and this is solidified by heating at least once on and in the carrier, the suspension having a sol and at least two fractions of particles, of which the first fraction oxide particles with an average particle size of 0.5 to 10 μm, selected from the oxides of the elements AI, Zr and / or Si and is present in a proportion of 75 to 99 parts by mass, preferably 85 to 90 parts by mass and of which the second fraction has zeolite particles with an average particle size of 0.5 to 10 μm and with a proportion of 1 to 25 parts by mass, preferably 10 to 15 parts by mass n is. During solidification, the sol forms the inorganic adhesive with which the particles are bonded to one another and to the carrier or the adhesion promoter (s) that may be present.

The production of separators or membranes is known in principle from WO 99/15262. The use of electrically conductive feed materials and flexible carriers, such as, for example, described there. As stainless steel, however, separators can be obtained which cannot be used or can only be used to a very limited extent for the production of the separators according to the invention. The use of separators according to the procedure described below have been found to be particularly advantageous.

The separators according to the invention are obtained by applying a suspension which contains inorganic, electrically non-conductive particles to a porous, non-electrically conductive support and then solidifying the suspension to form an inorganic coating on and in the porous support. The suspension can e.g. B. by printing, pressing, pressing, rolling, knife coating, spreading, dipping, spraying or pouring onto the carrier.

The carrier used preferably has a thickness of less than 30 μm, preferably less than 20 μm and particularly preferably a thickness of 10 to 20 μm. Particularly preferred carriers are those as described in the description of the separator according to the invention. The porous support used therefore preferably has woven or non-woven polymer fibers. A carrier is particularly preferably used which has a polymer fabric or nonwoven or is such a fabric or nonwoven. The carrier used preferably has polymer fibers which have a softening temperature of greater than 100 ° C. and a melting temperature of greater than 110 ° C. It can be advantageous if the polymer fibers have a diameter of 0.1 to 10 μm, preferably 1 to 5 μm. In the process according to the invention, it is particularly preferred to use a carrier which has fibers selected from polyacrylonitrile, polyester, polyamide and / or polyolefin.

The suspension used to produce the coating has at least particles of Al ₂ O ₃ , ZrO ₂ and / or SiO ₂ , at least one fraction of zeolite particles and at least one sol, the elements Al, Zr and / or Si, and is by Suspend the particles in at least one of these brines. The suspension takes place by intensive mixing of the components. The particles used preferably have an average particle size of 0.5 to 10 μm, preferably an average particle size of 1 to 4 μm. Aluminum oxide particles which preferably have an average particle size of 0.5 to 10 μm, preferably 1 to 4 μm, are particularly preferably used as metal oxide particles for producing the suspension. Aluminum oxide particles in the range of the preferred particle sizes are, for example, from the Martinswerke company under the names MZS 3 and MZS 1 and from the company AlCoA under the names CT3000 SG, CL3000 SG, CT1200 SG, CT800SG and HVA SG offered.

It has been found that the use of commercially available oxide particles may lead to unsatisfactory results, since there is often a very wide particle size distribution. It is therefore preferred to use metal oxide particles, which by a conventional method such. B. wind classifying and hydroclassification were classified. Fractions in which the coarse grain fraction, which makes up up to 10% of the total amount, have been separated off by wet sieving are preferably used as oxide particles. This disruptive coarse grain fraction, which can also not be comminuted or can only be comminuted with great difficulty by the processes typical of the preparation of the suspension, such as grinding (ball mill, attritor mill, mortar mill), dispersing (Ultra-Turrax, ultrasound), grinding or chopping. B. consist of aggregates, hard agglomerates, grinding ball abrasion. The aforementioned measures ensure that the inorganic porous layer has a very uniform pore size distribution. This is achieved in particular by using oxide particles which have a maximum particle size of preferably 1/3 to 1/5 and particularly preferably less than or equal to 1/10 of the thickness of the nonwoven used.

The following Table 2 gives an overview of how the choice of different aluminum oxides affects the porosity and the resulting pore size of the respective porous inorganic coating. To determine this data, the corresponding slurries (suspensions or dispersions) were produced and dried and solidified as pure moldings at 200 ° C.

Table 2: Typical data of ceramics depending on the type of powder used

The mean pore size and the porosity is to be understood as the mean pore size and the porosity which can be determined by the known method of mercury porosimetry, e.g. using a Porosimeter 4000 from Carlo Erba Instruments. Mercury porosimetry is based on the Washburn equation (EW Washburn, "Note on a Method of Determining the Distribution of Pore Sizes in a Porous Material", Proc. Natl. Acad. Sci., 1, 115-16 (1921) ).

In principle, particles of all known zeolites can be used as zeolite particles. The less hydrophobic types of zeolites are preferably used. To produce the separator according to the invention, preference is given to using those particles which are selected from the zeolites zeolite-A, zeolite-Y and zeolite-USY as zeolite particles. In Table 1 given above, some material data of these preferred types of zeolite are given. However, other zeolites known from the prior art can also be used. The zeolites are e.g. B. from Zeolyst under the name given in Table 1.

The zeolites can either be used in their typical delivery form, for example as Na ⁺ or ET form, or they can be converted into their Li ⁺ form. To this end, the zeolites are first converted into the Li form by repeatedly exchanging the alkali or alkaline earth ions in a Li salt solution. This can be done at room temperature or at the boiling point. The transfer of the zeolites into the corresponding forms can also take place after the separator has been completed. The zeolites either come from the manufacturer in the appropriate particle size or still have to be ground down to the desired size, ie to an average particle size of 0.5 to 10 μm. This can be done using known techniques (ball mill, attritor mill).

The mass fraction of the suspended components (particles) is preferably 1 to 250 times, particularly preferably 1 to 50 times the sol used. The sols are obtained by hydrolysing at least one (precursor) compound of the elements Zr, Al and / or Si. It may be advantageous to add the compound to be hydrolyzed to alcohol or an acid or a combination of these liquids before the hydrolysis. The compound to be hydrolyzed is preferably hydrolyzed at least one nitrate, a chloride, a carbonate or an alcoholate compound of the elements Zr, Al and / or Si. The hydrolysis is preferably carried out in the presence of water, steam, ice, alcohol or an acid or a combination of these compounds. The sols are preferably obtained by hydrolyzing a compound of the elements Al, Zr or Si with water or an acid diluted with water, the compounds preferably being dissolved in a nonaqueous, optionally also anhydrous solvent and 0.1 to 100 times Molar ratio of water are hydrolyzed.

In one embodiment variant of the production process for the separator according to the invention, particulate sols are produced by hydrolysis of the compounds to be hydrolyzed. These particulate sols are characterized by the fact that the compounds formed in the sol by hydrolysis are present in particulate form. The particulate sols can be prepared as described above or as described in WO 99/15262. These brines usually have a very high water content, which is preferably greater than 50% by weight. It may be advantageous to add the compound to be hydrolyzed to alcohol or an acid or a combination of these liquids before the hydrolysis. For the peptization, the hydrolyzed compound can be treated with at least one organic or inorganic acid, preferably with a 5 to 50% organic or inorganic acid, particularly preferably with a mineral acid selected from sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid and nitric acid or a mixture of these acids become. The particulate sols produced in this way can then be used for the production of suspensions, the production of suspensions for application to polymer fiber nonwovens pretreated with polymeric sol being preferred.

In a further embodiment variant of the production process for a separator which can be used according to the invention, polymeric sols are produced by hydrolysis of the compounds to be hydrolyzed. These polymeric sols are characterized in that the compounds formed in the sol by hydrolysis are polymeric (i.e. chain-like over a larger one) Networked space). The polymeric sols usually have less than 50% by weight, preferably very much less than 20% by weight, of water and / or aqueous acid. In order to arrive at the preferred proportion of water and / or aqueous acid, the hydrolysis is preferably carried out in such a way that the compound to be hydrolyzed with the 0.5 to 10-fold molar ratio and preferably with half the molar ratio of water, steam or ice, based on the hydrolyzable Group, the hydrolyzable compound, is hydrolyzed. Up to 10 times the amount of water can be used with very slow hydrolyzing compounds such as e.g. B. be used in tetraethoxysilane. Very rapidly hydrolyzing compounds such as zirconium tetraethylate can already form particulate sols under these conditions, which is why 0.5 times the amount of water is preferably used for the hydrolysis of such compounds. Hydrolysis with less than the preferred amount of water, water vapor, or ice also gives good results. However, falling below the preferred amount of half a molar ratio by more than 50% is possible but not very useful, since if this value is not reached the hydrolysis is no longer complete and coatings based on such brine are not very stable.

To produce this brine with the desired very low proportion of water and / or acid in the sol, it may be advantageous if the compound to be hydrolyzed is in an organic solvent, in particular ethanol, isopropanol, butanol, amyl alcohol, hexane, cyclohexane, ethyl acetate and or mixtures of these compounds is dissolved before the actual hydrolysis is carried out. A sol produced in this way can be used to produce the suspension according to the invention or as an adhesion promoter in a pretreatment step. A suspension which has a polymeric sol of a compound of silicon is particularly preferably used to produce the separator according to the invention.

Both the particulate sols and the polymeric sols can be used as sols in the process according to the invention for producing the suspension. In addition to the brines, which are available as just described, commercially available brines such as e.g. B. zirconium nitrate sol or silica sol can be used. The process for the production of separators which can preferably be used in the process according to the invention by applying and solidifying a suspension to a carrier per se is known from DE 101 42 622 and in Similar form known from WO 99/15262, but not all parameters or feedstocks can be transferred to the manufacture of the separator used in the process according to the invention. The process described in WO 99/15262, in this form, is in particular not transferable to polymeric nonwoven materials without compromises, since the very water-containing sol systems described there often do not allow continuous wetting of the usually hydrophobic polymeric nonwovens in depth, since the very water-containing ones Sol systems do not, or only poorly, wet most polymer nonwovens. It was found that even the smallest non-wetted areas in the nonwoven material can result in membranes or separators being obtained which have defects (such as holes or cracks) and are therefore unusable.

It has been found that a sol system or a suspension which has been adapted to the polymers in terms of wetting behavior completely impregnates the carrier materials, in particular the nonwoven materials, and thus flawless coatings are obtainable. The wetting behavior of the sol or suspension is therefore preferably adjusted in the method according to the invention. This adaptation is preferably carried out by the production of polymeric sols or suspensions from polymeric sols, which sols one or more alcohols, such as. B. methanol, ethanol or propanol or mixtures thereof. However, other solvent mixtures are also conceivable which can be added to the sol or the suspension in order to adapt them to the nonwoven used in terms of crosslinking behavior.

It was found that the fundamental change in the sol system and the resulting suspension leads to a significant improvement in the adhesive properties of the ceramic components on and in a polymeric nonwoven material. Such good adhesive strengths are normally not available with particulate sol systems. Therefore, nonwovens which have polymer fibers are preferably coated by means of suspensions which are based on polymeric sols or which have been provided with an adhesion promoter in a preceding step by treatment with a polymeric sol.

To improve the adhesion of the inorganic components to polymer fibers or nonwovens as a substrate, but also to improve the adhesion of one later if necessary applied switch-off layer, it can be advantageous to use the suspensions adhesion promoters such. B. organofunctional silanes, such as. B. the Degussa silanes GLYMO, MEMO, AMEO, VTEO or Silfin. The addition of adhesion promoters is preferred for suspensions based on polymeric brine. In particular, compounds selected from the octylsilanes, the vinylsilanes, the amine-functionalized silanes and / or the glycidyl-functionalized silanes, such as, for. B. the Dynasilane from Degussa can be used. Particularly preferred adhesion promoters for polyethylene (PE) and polypropylene (PP) are vinyl, methyl and octylsilanes, where the exclusive use of methylsilanes is not optimal, for polyamides and polyamines it is amine-functional silanes, for polyacrylates, polyacrylonitrile and polyesters it is glycidyl -functionalized silanes. Other adhesion promoters can also be used, but these have to be matched to the respective polymers. The adhesion promoters must be selected so that the solidification temperature is below the melting or softening point of the polymer used as the substrate and below its decomposition temperature. In particular, the silanes listed in Table 1 can be used as adhesion promoters. Suspensions according to the invention preferably have very much less than 25% by weight, preferably less than 10% by weight, of compounds which can act as adhesion promoters. An optimal proportion of adhesion promoter results from the coating of the fibers and / or particles with a monomolecular layer of the adhesion promoter. The amount of adhesion promoter required in grams can be obtained by multiplying the amount of oxides or fibers used (in g) by the specific surface area of the materials (in m ² g ^" ') and then dividing by the specific space requirement of the adhesion promoter (in m ² g ^" ') are obtained, the specific space requirement often being in the order of 300 to 400 m ² g ^{" 1} .

Table 3 below contains an exemplary selection of preferably used adhesion promoters based on organofunctional Si compounds for typical polymers used as nonwoven material. Table 3

With: AMEO = 3-aminopropyltriethoxysilane DAMO = 2-aminoethyl-3-aminopropyltrimethoxysilane GLYMO = 3-glycidyloxytrimethoxysilane MEMO = 3-methacryloxypropyltrimethoxysilane Silfin = vinylsilane + initiator + catalyst VTEO = vinyltriethoxysilane

VTMO = vinyltrimethoxysilane VTMOEO = vinyltris (2-methoxyethoxy) silane

The suspension present on and in the carrier by the application (the coating) can e.g. B. solidified by heating to 50 to 350 ° C. Since the maximum temperature is predetermined by the carrier material when using polymeric substrate materials, this must be adjusted accordingly so that the carrier material does not melt or soften. Depending on the variant of the method, the suspension present on and in the carrier is solidified by heating to 100 to 350 ° C. and very particularly preferably by heating to 200 to 280 ° C. It may be advantageous if the heating is carried out for 1 second to 60 minutes at a temperature of 150 to 350 ° C. The suspension is particularly preferably heated for solidification to a temperature of 110 to 300 ° C., very particularly preferably at a temperature of 150 to 280 ° C. and preferably for 0.5 to 10 min. The suspension is heated on a polymer fleece with fibers made of polyester, preferably for 0.5 to 10 minutes at a temperature of 200 to 220 ° C. The warming The suspension on a polymer fleece with fibers made of polyamide is preferably carried out for 0.5 to 10 minutes at a temperature of 170 to 200 ° C. The composite can be heated by means of heated air, hot air, infrared radiation or by other heating methods according to the prior art.

The process for the production of separators which can be used in the process according to the invention can, for. B. be carried out so that the carrier is unrolled from a roll, at a speed of 1 m / h to 2 m / s, preferably at a speed of 0.5 m / min. up to 20 m / min and very particularly preferably at a speed of 1 m / min to 5 m / min by at least one apparatus which brings the suspension onto and into the carrier, such as, for. B. a roller, and at least one other apparatus which allows the solidification of the suspension on and in the carrier by heating, such as. B. passes through an electrically heated oven and the separator thus produced is rolled up on a second roll. In this way it is possible to manufacture the separator in a continuous process. The pre-treatment steps can also be carried out in a continuous process while maintaining the parameters mentioned.

In contrast to processes in which no zeolite particles are used, in the present process it is necessary to provide drying that is long enough so that the zeolite present in the separator is water-free after the separator has been produced. This is achieved by longer residence times in the oven at the specified temperature (e.g. by using a correspondingly long oven) or by post-heating at a temperature of 40 to 100 ° C at a relative humidity (RH) of 0.1 to 5% RH. The separator is preferably stored water-free (<1% RH) after production, since it absorbs water from the atmosphere quite easily due to the proportion of zeolite, especially when using the more hydrophilic zeolites. Water absorption would preclude the possibility of using it in lithium-ion batteries.

The separators according to the invention can also be equipped with a shutdown layer. The separators produced according to the invention have, if not below

Using an adhesion promoter were often made on inorganic coatings that have a very hydrophilic character. To ensure good adhesion of the porous fabric To achieve the shutdown layer on hydrophilic porous inorganic layers, several variants are possible.

In an embodiment variant of the method according to the invention, it has proven to be advantageous to hydrophobicize the porous inorganic layer before the shutdown layer is applied. The production of hydrophobic membranes, which can serve as the starting material for the production of the separators according to the invention, is described, for example, in WO 99/62624. The porous inorganic layer is preferably treated by treatment with alkyl, aryl or fluoroalkylsilanes, as described, for. B. are sold under the name Dynasilan by Degussa, hydrophobized. It can z. B. the known methods of hydrophobization, which are used, inter alia, for textiles (D. Knittel; E. Schollmeyer; Melliand Textilber. (1998) 79 (5), 362-363), with a slight change in the recipes, also for porous permeable fabrics Composites, which, for. B. were prepared by the method described in PCT / EP98 / 05939, applied. For this purpose, a permeable composite material (membrane or separator) is treated with a solution which has at least one hydrophobic substance. It can be advantageous if the solution contains water, which has preferably been adjusted to a pH of 1 to 3 with an acid, preferably acetic acid or hydrochloric acid, and / or an alcohol, preferably ethanol. The proportion of acid-treated water or alcohol in the solvent can be from 0 to 100% by volume. The proportion of water in the solvent is preferably from 0 to 60% by volume and the proportion of alcohol from 40 to 100% by volume. To prepare the solution, 0.1 to 30% by weight, preferably 1 to 10% by weight, of a hydrophobic substance are added to the solvent. As hydrophobic substances such. B. the silanes listed above can be used. Surprisingly, good hydrophobization takes place not only with strongly hydrophobic compounds, such as, for example, with triethoxy (3,3,4,4,5,5,6,6,7,7,8,8-tridecafluorooctyl) silane, but also one Treatment with methyl, octyl or i-butyltriethoxysilane is completely sufficient to achieve the desired effect. The solutions are stirred at room temperature for uniform distribution of the hydrophobic substances in the solution and then applied to the porous inorganic layer and dried. Drying can be accelerated by treatment at temperatures from 50 to 350 ° C and preferably at 150 to 200 ° C. In a further embodiment variant of the method according to the invention, the porous inorganic layer can also be treated with other adhesion promoters before the shutdown layer is applied. The treatment with one of the adhesion promoters listed in Table 1 can then also be carried out as described above, ie the porous inorganic layer is treated with a polymeric sol which has a silane as an adhesion promoter. In particular, the treatment can be carried out in such a way that adhesion promoters are used in the manufacture of the separator as described above. The adhesion promoters are preferably selected from the series of hydrolyzed or non-hydrolyzed functionalized alkyl trialkoxysilanes. MEMO, AMEO and / or GLYMO are very particularly used as adhesion promoters.

Such a temperature treatment may also be necessary to activate the silanes as adhesion promoters so that they stick the switch-off layer to the ceramic separator.

In a preferred embodiment, MEMO is used as an adhesion promoter between the switch-off layer and the ceramic separator. When MEMO is used, it is activated by UV light at a preferred wavelength of 200-300 nm.

The switch-off layer can be, for example, a porous sheet or a layer of particles, the sheet or particles consisting of a material that melts at a certain temperature. The switch-off layer based on a porous fabric is preferably produced on the porous inorganic layer of the separator in that a fabric, knitted fabric, felt, fleece or a porous film is applied to the porous inorganic layer as the porous fabric. The shutdown layer can be applied by placing or laminating the porous fabric onto the porous inorganic layer. The lamination can be carried out at room temperature or at an elevated temperature which is below the melting temperature of the material of the fabric. The above-mentioned adhesion promoters can be used as laminating agents for laminating. The adhesion promoters can be selected from the known series of alkyl trialkoxysilanes. These adhesion promoters are preferably in the form of solutions or sols and are either first applied to polymer or separator and solidified there, or else the silanes are introduced directly before or during lamination, thus gluing polymer and ceramic. Suitable silanes are e.g. B. from Degussa as pure products or as aqueous solutions of the hydrolyzed silane under z. B. the name Dynasilan 2926, 2907 or 2781 available.

When laminating (with or without the use of a laminating agent) but also when placing the porous fabric, the switch-off layer can, after being applied to the porous inorganic layer, be heated to a temperature above the glass temperature once, so that the material melts without changing the actual shape of the porous fabric is achieved to be fixed on the porous inorganic layer.

Another possibility of fixing the switch-off layer on the porous inorganic layer of the separator can e.g. in that the switch-off layer is applied to the porous inorganic layer and is fixed by being wrapped in the manufacture of the battery.

All materials with a defined melting point can be used as the material for the switch-off layer. The material for the shutdown layer is selected according to the desired shutdown temperature. Since relatively low switch-off temperatures are desired for most batteries, it is advantageous to use as a switch-off layer those porous fabrics which are selected from polymers, polymer mixtures, natural and / or artificial waxes. These preferably have a melting temperature of less than or equal to 180 ° C., preferably less than 150 ° C. and very particularly preferably less than 130 ° C. Those made of polypropylene or polyethylene (wax) are particularly preferably used as shutdown layers. Possible suppliers for such polymeric fabrics are typical nonwoven suppliers such as Freudenberg or manufacturers of organic separators such as Celgard, DSM, Asahi or Übe. As stated above, it can be advantageous if the material from which the porous fabric is made is identical to at least part of the material of the carrier.

The application of the porous fabric and, if necessary, of adhesion promoters and a any heating can be carried out continuously or quasi continuously. If a flexible separator is used as the starting material, it can in turn be unwound from a roll, passed through a coating, drying and possibly heating apparatus and then rolled up again.

In another preferred embodiment of the method according to the invention, the separator according to the invention is equipped with a shutdown function by applying and fixing particles as shutdown particles which have a defined, desired melting temperature. If the separators according to the invention were produced without using an adhesion promoter, this has a ceramic coating, which often has a very hydrophilic character. In order to achieve good adhesion and even distribution of the shutdown particles in the shutdown layer even on hydrophilic porous inorganic layers, several variants are possible.

In an embodiment variant of the method according to the invention, it has proven to be advantageous to hydrophobicize the porous inorganic layer before the shutdown particles are applied. The production of hydrophobic membranes, which can serve as the starting material for the production of the separators according to the invention, is described, for example, in WO 99/62624. The porous inorganic layer is preferably rendered hydrophobic by treatment with alkyl-, aryl- or fluoroalkylsilanes, such as those sold by Degussa under the Dynasilan brand name. For example, the known methods of hydrophobization, which are used for textiles, among others (D. Knittel; E. Schollmeyer; Melliand Textilber. (1998) 79 (5), 362-363), with a slight change in the recipes, also for porous permeable composite materials, which have been produced, for example, by the process described in PCT / EP98 / 05939, are used. For this purpose, a permeable composite material (membrane or separator) is treated with a solution which has at least one hydrophobic substance. It can be advantageous if the solution contains water, which has preferably been adjusted to a pH of 1 to 3 with an acid, preferably acetic acid or hydrochloric acid, and / or an alcohol, preferably ethanol. The proportion of water treated with acid or of alcohol in the solvent can in each case be from 0 to 100% by volume. The proportion of water in the solvent is preferably from 0 to 60% by volume and the proportion of alcohol from 40 to 100 vol .-%. To prepare the solution, 0.1 to 30% by weight, preferably 1 to 10% by weight, of a hydrophobic substance are added to the solvent. The above-mentioned silanes can be used as hydrophobic substances. Surprisingly, good hydrophobization takes place not only with strongly hydrophobic compounds, such as, for example, with triethoxy (3,3,4,4,5, 5,6,6,7,7,8,8-tridecafluorooctyl) silane, but one Treatment with methyltriethoxysilane or i-butyltriethoxysilane is completely sufficient to achieve the desired effect. The solutions are stirred at room temperature for uniform distribution of the hydrophobic substances in the solution and then applied to the porous inorganic layer and dried. Drying can be accelerated by treatment at temperatures from 25 to 100 ° C.

In a further embodiment variant of the method according to the invention, the porous inorganic layer can also be treated with other adhesion promoters before the shutdown particles are applied. Treatment with one of the adhesion promoters listed in Table 1 can then also be carried out as described above, i.e. that the porous inorganic layer is treated with a polymeric sol which has a silane as an adhesion promoter. In particular, the treatment can be carried out in such a way that adhesion promoters are used in the manufacture of the separator as described above.

The layer of shutdown particles is preferably produced by applying a suspension of shutdown particles in a suspension medium selected from a sol, water or solvent, such as, for example, alcohol, hydrocarbons, ethers or ketones or a solvent mixture. In principle, the particle size of the shutdown particles present in the suspension is arbitrary. However, it is advantageous if shutdown particles with an average particle size (D _w ) greater than the average pore size of the pores of the porous inorganic layer (d _s ) are present in the suspension, since this ensures that the pores of the inorganic layer are used in the production of the invention Separators are not clogged by shutdown particles. The shutdown particles used preferably have an average particle size (D _w ) which is greater than the average pore diameter (d _s ) and less than 5 d _s , particularly preferably less than 2 d _s . Water is preferably used as the solvent for the dispersion. This watery Dispersions are adjusted to a polymer or wax content of 1 to 60, preferably from 5 to 50 and very particularly preferably from 20 to 40% by weight. When water is used as the solvent, preferred average particle sizes of 1 to 10 μm can be obtained in the dispersion very easily, as are very suitable for the separators according to the invention.

If a non-aqueous solvent is used to produce the wax or polymer dispersion, then average particle sizes of less than 1 μm can preferably be obtained in the dispersion. Mixtures of non-aqueous solvents with water can also be used.

If it is desired to use shutdown particles that have a particle size smaller than the pore size of the pores of the porous inorganic layer, it must be avoided that the particles penetrate into the pores of the porous inorganic layer. Reasons for using such particles can e.g. there are large price differences but also the availability of such particles. One way to prevent the cut-off particles from penetrating into the pores of the porous inorganic layer is to adjust the viscosity of the suspension so that, in the absence of external shear forces, the suspension does not penetrate into the pores of the inorganic layer. Such a high viscosity of the suspension can e.g. can be achieved by adding additives to the suspension that influence the flow behavior, e.g. Silicas (Aerosil, Degussa) can be added. When using auxiliary materials such as Aerosil 200 is often a proportion of 0.1 to 10% by weight, preferably 0.5 to 50% by weight, of silica, based on the suspension, already sufficient to achieve a sufficiently high viscosity of the suspension. The proportion of auxiliary substances can be determined by simple preliminary tests.

It can be advantageous if the suspension used has shut-off particles with adhesion promoters. Such a suspension having an adhesion promoter can be applied directly to a separator, even if it was not hydrophobicized before the application. Of course, a suspension having an adhesion promoter can also be applied to a hydrophobized separator or to a separator in the production of which an adhesion promoter was used. As an adhesion promoter in the shutdown particles Suspensions are preferably used silanes which have amino, vinyl or methacrylic side groups. Such silanes are available, for example, from Degussa as pure products or as aqueous solutions of the hydrolyzed silane under the name Dynasilan 2926, 2907 or 2781, for example. A maximum of 10% by weight of adhesion promoter has been found to be sufficient to ensure sufficient adhesion of the shutdown particles to the porous inorganic layer. Suspensions containing switch-off particles preferably contain adhesion promoters from 0.1 to 10% by weight, preferably from 1 to 7.5% by weight and very particularly preferably from 2.5 to 5% by weight, based on the suspension, of adhesion promoters ,

All particles that have a defined melting point can be used as shutdown particles. The material of the particles is selected according to the desired switch-off temperature. Since relatively low switch-off temperatures are desired for most batteries, it is advantageous to use switch-off particles which are selected from particles of polymers, polymer mixtures, natural and / or artificial waxes. Particles made of polypropylene or polyethylene wax are particularly preferably used as shutdown particles.

The suspension containing the shutdown particles can be applied to the porous inorganic layer by printing, pressing, pressing, rolling, knife coating, brushing, dipping, spraying or pouring. The switch-off layer is preferably obtained by drying the applied suspension at a temperature from room temperature to 100 ° C., preferably from 40 to 60 ° C. Drying must be carried out in such a way that the shutdown particles do not melt.

It can be advantageous if, after being applied to the porous ceramic coating, the particles are fixed by heating them at least once to a temperature above the glass temperature, so that the particles melt without changing the actual shape. In this way it can be achieved that the shutdown particles adhere particularly well to the porous, inorganic layer.

The application of the suspension with subsequent drying and a possible heating The glass transition temperature can be used continuously or quasi-continuously to produce the separator itself, in which the separator in turn is unwound from a roll, passed through a coating, drying and, if appropriate, heating apparatus and then rolled up again.

The separators according to the invention or the separators produced according to the invention can be used as a separator in batteries, in particular as a separator in lithium batteries, preferably lithium high-performance and high-energy batteries. Such lithium batteries can have lithium salts with large anions in carbonates as solvents as electrolytes. Suitable lithium salts are e.g. B. LiClO, LiBF, LiAsF ₆ or LiPF ₆ , with LiPF _{6 being} particularly preferred. Organic carbonates suitable as solvents are e.g. B. ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate or mixtures thereof.

The invention also relates to batteries, in particular lithium batteries, which have a separator according to the invention or produced according to the invention.

The present invention is described by the following examples without being limited thereto.

Examples

Comparative example: separator according to the prior art

30 g of a 5% strength by weight aqueous solution were initially added to 130 g of water and 15 g of ethanol

ENT solution, 10 g tetraethoxysilane, 2.5 g methyltriethoxysilane and 7.5 g Dynasilane GLYMO (Degussa AG). 125 g of the aluminum oxides Martoxid MZS-1 and Martoxid MZS-3 (Martinswerke) were then suspended in this sol, which was initially stirred for a few hours. This slip was homogenized for at least a further 24 h using a magnetic stirrer, the stirring vessel having to be covered so that it did not become one

Solvent loss came.

A 20 cm wide PET fleece (Freudenberg Vliesstoffe KG) with a thickness of approx. 20 μm and a basis weight of approx. 15 g / m ² was then in a continuous Roll-on process (belt speed approx. 30 m / h, T = 200 ° C) coated with the above slip. At the end, a separator with an average pore size of 450 nm was obtained.

Example 1 30 g of a 5% strength by weight aqueous HNO ₃ solution, 10 g of tetraethoxysilane, 2.5 g of methyltriethoxysilane and 7.5 g of Dynasilane GLYMO (Degussa AG) were first added to 195 g of water and 15 g of ethanol. 113 g of the aluminum oxides Martoxid MZS-1 and Martoxid MZS-3 (Martinswerke) and 25 g of zeolite CBV600 (Zeolyst) were then suspended in this sol, which was initially stirred for a few hours. This slip was homogenized for at least a further 24 h using a magnetic stirrer, the stirring vessel having to be covered so that there was no loss of solvent.

A 20 cm wide PET fleece (Freudenberg Vliesstoffe KG) with a thickness of approx. 20 μm and a weight per unit area of approx. 15 g / m ² was then rolled up in a continuous process (belt speed approx. 30 m / h, T = 220 ° C. ) coated with the above slip. At the end, a separator with an average pore size of 450 nm was obtained.

Example 2

30 g of a 5% strength by weight aqueous HNO ₃ solution, 10 g of tetraethoxysilane, 2.5 g of methyltriethoxysilane and 7.5 g of Dynasilane GLYMO (Degussa AG) were initially added to 195 g of water and 15 g of ethanol. 106 g of the aluminum oxides Martoxid MZS-1 and Martoxid MZS-3 (Martinswerke) and 38 g of zeolite CBV600 (Zeolyst) were then suspended in this sol, which was initially stirred for a few hours. This slip was homogenized for at least a further 24 h using a magnetic stirrer, the stirring vessel having to be covered so that there was no loss of solvent.

A 20 cm wide PET fleece (Freudenberg Vliesstoffe KG) with a thickness of approx. 20 μm and a weight per unit area of approx. 15 g / m ² was then rolled up in a continuous process (belt speed approx. 30 m / h, T = 220 ° C. ) coated with the above slip. In the end, a separator with an average pore size of 450 nm is obtained.

Example 3 30 g of a 5% strength by weight aqueous HNO ₃ solution, 10 g of tetraethoxysilane, 2.5 g of methyltriethoxysilane and 7.5 g of Dynasilane GLYMO (Degussa AG) were first added to 163 g of water and 15 g of ethanol. 113 g of the aluminum oxides Martoxid MZS-1 and Martoxid MZS-3 (Martinswerke) and 25 g of zeolite CBV712 (Zeolyst) were then suspended in this sol, which was initially stirred for a few hours. This slip was homogenized for at least a further 24 h using a magnetic stirrer, the stirring vessel having to be covered so that there was no loss of solvent.

A 20 cm wide PET fleece (Freudenberg Vliesstoffe KG) with a thickness of approx. 20 μm and a weight per unit area of approx. 15 g / m ² was then used in a continuous rolling process (belt speed approx. 30 mh, T = 220 ° C) Coated above slip. At the end, a separator with an average pore size of 450 nm was obtained.

Example 4

30 g of a 5% strength by weight aqueous HNO ₃ solution, 10 g of tetraethoxysilane, 2.5 g of methyltriethoxysilane and 7.5 g of Dynasilane GLYMO (Degussa AG) were initially added to 195 g of water and 15 g of ethanol. 113 g of the aluminum oxides Martoxid MZS-1 and Martoxid MZS-3 (Martinswerke) and 25 g of zeolite CBV3024 (Zeolyst) were then suspended in this sol, which was initially stirred for a few hours. This slip was homogenized for at least a further 24 h using a magnetic stirrer, the stirring vessel having to be covered so that there was no loss of solvent.

A 20 cm wide PET fleece (Freudenberg Vliesstoffe KG) with a thickness of approx. 20 μm and a weight per unit area of approx. 15 g / m ² was then rolled up in a continuous process (belt speed approx. 30 m / h, T = 220 ° C ) coated with the above slip. At the end, a separator with an average pore size of 450 nm was obtained. Example 5: Characterization of the separators

* The samples were previously dried anhydrous, a 0.01 molar solution of LiClO in propylene carbonate serves as the electrolyte

Determination of the MacMulIin number:

For this purpose, the conductivity LF1 of the pure electrolyte (a 0.01 molar solution of LiClO in propylene carbonate) was first determined with a conductometer (Metrohm) at 30 ° C. Then the separator was impregnated with electrolyte and the conductivity LF2 was also determined therefrom. The MacMullin number is the ratio of these two conductivities LF1 / LF2.

Determination of the BP:

The bubble point (BP) is the pressure in bar at which a gas bubble passes through a completely wetted membrane (separator). It is a measure of the size of the largest pore or defect in a membrane. The smaller the BP, the larger the largest pore or the largest defect (hole).

A membrane with a size of 30 mm diameter was cut to measure the bubble point. The cut membrane was stored in the wetting liquid (deionized water) for at least one day. The membrane prepared in this way was installed in an apparatus between a round sintered metal disc with a BP of approx. 0 bar (measurement without a membrane), which serves as support material, and a silicone rubber seal, the apparatus having an open-topped vessel, which had the same cross-section as the membrane and was filled with 2 cm with demineralized water, and below the membrane had a second vessel, which also had the same cross-section as the membrane, and which was equipped with an air inlet over which Compressed air could be introduced into the vessel via a pressure reducing valve. The membrane was installed under the sintered metal disc, so that the sintered metal disc formed the bottom of the upper vessel and the membrane closed off the lower vessel. The pressure in the lower vessel was then increased in 0.1 bar steps, with half a minute between each pressure increase. After each pressure increase, the water surface in the upper vessel was observed for about half a minute. When the first small gas bubbles appeared on the water surface, the pressure of the BP was reached and the measurement was stopped.

Determination of the Gurley number The Gurley number was determined in the same apparatus as the BP. When determining the Gurley number, however, the time t was determined, which requires a gas volume of 100 ml to flow through an area of 6.45 cm (at a pressure of 31 cm water column of the gas). The time t is the Gurley number.

As can be seen from the table, a significant increase in conductivity was found in all cases when using zeolites. It can be seen that when using CBV600 (according to Example 2) the conductivity can be increased by 65% compared to the comparative example without zeolite. The MacMullin number is reduced accordingly.

Claims

claims

1. Separator for electrochemical cells comprising a porous carrier, which has woven or non-woven polymer fibers, with a porous inorganic, non-electrically conductive coating located on and in this carrier from particles bonded to one another and to the carrier with an average particle size of by an inorganic adhesive 0.5 to 10 μm, characterized in that the inorganic coating has from 75 to 99 parts by mass of one or more oxide particles of the elements Al, Si and / or Zr with an average particle size of 0.5 to 10 μm and from 1 to Has 25 parts by mass of particles with an average particle size of 0.5 to 10 microns at least one zeolite.

2. Separator according to claim 1, characterized in that the zeolite particles have the zeolites in the Na ⁺ or Li ⁺ form.

3. Separator according to claim 1 or 2, characterized in that the carrier is flexible and has a thickness of less than 50 microns.

4. Separator according to claim 3, characterized in that the carrier is a polymer fleece.

5. Separator according to at least one of claims 1 to 4, characterized in that the polymer fibers of the carrier are selected from fibers of polyacrylonitrile, polyamide, polyester and / or polyolefin.

6. Separator according to at least one of claims 1 to 5, characterized in that the inorganic adhesives are selected from oxides of the elements AI, Si and / or Zr.

7. Separator according to at least one of claims 1 to 6, characterized in that the inorganic adhesive has particles with an average particle size of less than 20 nm and was produced via a particulate sol or has an inorganic network of oxides which is produced via a polymeric sol has been.

8. Separator according to at least one of claims 1 to 7, characterized in that an inorganic, silicon-containing network is additionally present, the silicon of the network via oxygen atoms to the oxides of the inorganic coating and via an organic residue to the carrier, the polymer fibers has, is bound.

9. Separator according to at least one of claims 1 to 8, characterized in that the zeolite particles are particles selected from the zeolites zeolite-A, zeolite-Y, zeolite-USY, ZSM-5 or ZSM-9.

10. A method for producing a separator according to at least one of claims 1 to 9, characterized in that a support having woven or non-woven polymer fibers is provided with a ceramic coating, for which a suspension is applied to and in the support and this through heating at least once on and in the carrier is solidified, the suspension having a sol and at least two fractions of particles, of which the first fraction oxide particles with an average particle size of 0.5 to 10 μm, selected from the oxides of the elements Al, Zr and / or Si and is present in a proportion of 75 to 99 parts by mass and of which the second fraction has zeolite particles with an average particle size of 0.5 to 10 μm and is present in a proportion of 1 to 25 parts by mass.

11. The method according to claim 10, characterized in that an additional adhesion promoter, which is selected from the organofunctional silanes, is additionally added to the suspension used before application to the carrier.

12. The method according to claim 11, characterized in that the coupling agent is selected from 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 3-glycidyloxytrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxy 2-silane methane and vinyltrimethoxy silane.

13. The method according to at least one of claims 10 to 12, characterized in that the suspension is brought onto and into the carrier by printing, extrusion, pressing, rolling, knife coating, spreading, dipping, spraying or pouring.

14. The method according to at least one of claims 10 to 13, characterized in that a polymer fleece is used as the carrier, the fibers selected from polyacrylonitrile, polyester, polyamide and / or polyolefin.

15. The method according to at least one of claims 10 to 14, characterized in that the suspension has at least one sol of a compound of the elements Al, Si, or Zr and is produced by suspending the particles in at least one of these sols.

16. The method according to claim 15, characterized in that the brine is obtained by hydrolysing a precursor compound of the elements AI, Zr or Si with water or an acid diluted with water.

17. The method according to claim 15, characterized in that the suspension comprises a polymeric sol of a compound of silicon.

18. The method according to claim 16 or 17, characterized in that the sols are obtained by hydrolyzing a compound of the elements Al, Zr or Si with water or an acid or a combination of these compounds, the compounds being present in solution in an anhydrous solvent and with 0.1 to 100 times the molar ratio of water are hydrolyzed.

19. The method according to at least one of claims 10 to 18, characterized in that the suspension present on and in the carrier is solidified by heating to 50 to 350 ° C.

20. The method according to claim 19, characterized in that the heating of the suspension on a polymer fleece with fibers made of polyester for 0.5 to 10 minutes at a temperature of 200 to 220 ° C.

21. The method according to claim 19, characterized in that the heating of the suspension on a polymer fleece with fibers made of polyamide for 0.5 to 10 minutes at a temperature of 130 to 180 ° C.

22. Use of a separator according to at least one of claims 1 to 9 as a separator in batteries.

23. Lithium battery, having a separator according to at least one of claims 1 to 9.