Electric separator, method for making same and use thereof in high-power lithium cells

p0001An electrical separator is a separator which is used in batteries and other arrangements in which electrodes, for example, have to be separated from one another, while maintaining ionic conductivity.

p0002The separator is usually a thin, porous, insulating material with high ion permeability, good mechanical strength and long-term stability against the chemicals and solvents used in the system, eg, in the electrolyte of the battery. In batteries, it is to isolate the cathode completely from the anode electronically but to be permeable to the electrolyte. In addition, it must be permanently elastic and follow the movements in the system, eg in the electrode package during charging and discharging.

p0003The separator decisively determines the service life of the device in which it is used, for example that of battery cells. The development of rechargeable batteries is therefore characterized by the development of suitable separator materials.

p0004General information on electrical separators and batteries can be found, for example, at JO Besenhard in "Handbook of Battery Materials" (VCH-Verlag, Weinheim 1999).

p0005Presently used separators consist predominantly of porous organic polymer films or of inorganic nonwovens, such as, for example, nonwovens of glass or ceramic materials or also ceramic papers. These are manufactured by different companies. Important producers are here: Celgard, Tonen, Ube, Asahi, Binzer, Mitsubishi, Daramic and others. A typical organic separator consists, for example, of polypropylene or of a polypropylene / polyethylene / polypropylene composite.

p0006Disadvantages of these organic polyolefin separators are their relatively low thermal loadability of significantly below 150 ° C. and their low chemical stability in inorganic lithium battery cells. The polyolefins used are slowly attacked in the Li batteries during contact of the separator with the lithium or with the lithiated graphite. Therefore, in systems with a polymer electrolyte, a dense oxidation product layer is formed, which prevents further destruction of the separator in Li-ion batteries.

p0007There are initial attempts to use inorganic composites as separators. Thus, in<patcit id="pcit0001" dnum="DE19838800"><text>DE198 38800</text></patcit> Characterized in that the material of the substrate is selected from metals, alloys, plastics, glass and carbon fiber or a combination. (DE). WIPO Home services World Intellectual Property Organization Of such materials and the coating is a porous, electrically nonconductive ceramic coating which is continuous. However, the separators, which have a support of electrically conductive material (as indicated in the example), have proven to be unsuitable for lithium-ion cells, since the coating can not be produced in the above-described thickness in a flawless manner and therefore very easily Short circuits.

p0008In summary, it can be stated that at the present time there is no suitable separator material with which, in particular, wound, inorganic high-performance or high-energy batteries can also be produced cost-effectively.

p0009In previous work (<patcit id="pcit0002" dnum="DE10142622"><text>DE 101 42 622</text></patcit>), It was shown that this is feasible with a material comprising a planar, multi-apertured, flexible substrate having a coating on and within that substrate, the material of the substrate being selected from woven or nonwoven Electrically conductive fibers of glass or ceramic or a combination of such materials and the coating is a porous, electrically insulating ceramic coating, and wherein the resulting separator has a thickness of less than 100 μm and is bendable, a resistance sufficiently low in connection with the electrolyte And nevertheless has a sufficiently long-term stability. However, the resistance of these separators is still too high for a large number of applications, since a glass fabric is used as the carrier, which is too thick in the first place and, secondly, has too little porosity. It is also desirable to be able to use a simultaneously thermally and chemically stable separator. It was therefore the object of the present invention to provide a

p0010Separator which is thermally more stable than polymer separators known up to now.

p0011In the further optimization of the properties of the <patcit id="pcit0003" dnum="DE10142622"><text>DE 101 42 622</text></patcit> It has been found that separators with the abovementioned properties can be realized when polymeric substrate materials are used. This results in electrical separators which comprise a planar, multiple-apertured, flexible substrate with a coating disposed on and within this substrate, the material of the substrate being selected from nonwoven, non-electrically conductive fibers of polymers, and the coating Is a porous, electrically insulating, ceramic coating. The separator has a thickness of less than 80 μm, is bendable and exhibits a sufficiently low resistance in conjunction with an electrolyte and, in addition, has a sufficiently long-term stability. The chemical resistance to strong bases is obtained by using stable polymers such as, for example, polypropylene / polyethylene or polyacrylonitrile nonwoven and resistant ceramic materials such as ZrO₂ and TiO₂. Although the in the not yet published application<patcit id="pcit0004" dnum="DE10208277"><text>DE 102 08 277</text></patcit> Described separators are very well suited for the described tasks, we had to conclude that the separators described there are however not very well suited for the use in lithium high-performance batteries, because in these batteries large currents have to be delivered in a very short time at almost constant voltage . In the<patcit id="pcit0005" dnum="DE10208277"><text>DE 102 08 277</text></patcit> Described separators do not meet the performance requirements for such separators for high-capacity lithium batteries, presumably because they have too low a porosity and too much thickness, and thus still have a low ionic conductivity.

p0012It was therefore the object of the present invention to provide a separator which is suitable for use in lithium high-capacity batteries. In order to be able to use a separator for such a battery system, the separator must have a significantly improved porosity and a thickness which is as small as possible. It is therefore also an object of the present invention to provide a separator which has a higher porosity than known separators but at the same time a high mechanical And thermal stability with as small a thickness as possible.

p0013Surprisingly, it has been found that separators which have a nonwoven fabric with a thickness of less than 30 μm, a porosity of more than 50% and a largely homogeneous pore radius distribution in which at least 50% of the pores have pore radii of 75 to 150 μm, A porous inorganic coating on and in the nonwoven, which preferably has particles bonded with zirconium oxide or silicon oxide with a particle size of 0.5 to 7 μm, a high porosity, an ideal pore width and a small thickness while at the same time very good thermal, Mechanical and chemical stability and can therefore be used much better than separators in lithium high-performance batteries.

p0014The object of the present invention is therefore a separator comprising a flexible nonwoven comprising a porous inorganic coating situated on and in this nonwoven, the material of the nonwoven being selected from nonwoven, non-electrically conductive polymer fibers, which is characterized in that the nonwoven has a thickness Of less than 30 μm, a porosity of more than 50%, preferably 50 to 97%, and a pore radius distribution in which at least 50% of the pores have a pore radius of 75 to 150 μm.

p0015The present invention furthermore provides a process for the production of a separator according to the invention, which is characterized in that a flexible nonwoven having a thickness of less than 30 μm, a porosity of 50 to 97% and a pore radius distribution in which at least 50% Of the pores have a pore radius of 75 to 150 μm is provided with a coating in and on this substrate, the material of the nonwoven being selected from non-woven, non-electrically conductive polymer fibers.

p0016The present invention also relates to the use of a separator according to the invention as a separator in lithium high-performance batteries and corresponding lithium high-performance batteries which have a separator according to the invention.

p0017In general, it can be stated that the greater the pores in the separator, the lower the resistance of the electrolyte-impregnated separator is, with the porosity and tortosity remaining the same. In addition, the choice of suitable particles can influence the porosity of the separator, which leads in the same way to changed properties. A characteristic parameter of a separator frequently used in this context is the Gurley number. It is a measure of the gas permeability of the dry porous separator. As described by O. Besenhard in the Handbook of Battery Materials, the conductivity of a known system can be directly deduced from the Gurley number. In general, it can be said that a greater gas permeability (ie, smaller Gurley number) results in a higher conductivity of the wetted separator in the battery cell. The values ​​of the Gurley number of commercially available separators are 10 to 50 when the pore diameter is 0.1 μm, and 20 to 100 when the pore diameter is 0.05 μm. ( "<nplcit id="ncit0001" npl-type="s"><text>G. Venugiopal; J. of Power Sources 77 (1999) 34-41</text></nplcit>).

p0018However, it must always be noted that an exceptionally small value of the Gurley number can also indicate defects, ie large holes, in the separator. These defects can lead to an internal short circuit during operation of a battery. The battery can then discharge itself very quickly in a dangerous reaction. In this case, large electrical currents occur in such a way that a closed battery cell can even explode in the worst case. For this reason, the separator can contribute decisively to the safety or the lack of safety of a lithium high-power or high-voltage battery. Therefore, the separator is a crucial component in a battery which must be given great attention.

p0019Polymer separators provide, for example, the safety required for lithium batteries at present, by preventing any current transport through the electrolyte from a certain temperature (the shut-down temperature, which is around 120 ° C.). This is because at this temperature the pore structure of the separator collapses and all pores are closed. Because no ions can be transported, the hazardous reaction that can lead to the explosion comes to a standstill. If, however, the cell is further heated due to external circumstances, the break-down temperature is exceeded at about 150 to 180 ° C. From this temperature, the separator is melted, the latter being contracted. At many points in the battery cell there is now a direct contact between the two electrodes and thus a large inner short circuit. This leads to the uncontrolled reaction, which ends with an explosion of the cell, or the resulting pressure is relieved by an overpressure valve (a rupture disk) frequently under fire phenomena.

p0020In the case of the inventive hybrid, ie, inorganic component and polymeric separator, a shut-down occurs when the polymer structure of the carrier material melts due to the high temperature and penetrates into the pores of the inorganic material and thereby closes the latter. However, the so-called melt-down (collapse) does not occur with the separator according to the invention. The separator according to the invention thus fulfills the requirements for a safety shutdown required by different battery manufacturers through the shutdown in the battery cells. The inorganic particles ensure that there can never be a melt-down. This ensures that there are no operating conditions in which a large-area short-circuit can occur.

p0021If an additional shut-down mechanism (shut-off mechanism) is mandatory for the application, this can also be achieved by providing the surface and / or the pores of the ceramic or hybrid separator according to the invention with a substance which, Temperature limit closes the pores and prevents the further ion flow. This can be achieved, for example, by a polymer or a wax whose melting point is within this range.

p0022The separator according to the invention is also very secure in the case of an internal short-circuit caused, for example, by an accident. If, for example, a nail is being drilled through a battery, the following happens depending on the separator: The polymer separator would melt and contract at the penetration point (a short-circuit current flows over the nail and heats it). As a result, the short circuit is getting bigger and the reaction gets out of control. In the case of the hybrid separator according to the invention, at most the polymeric substrate material, but not the inorganic separator material, melts. Thus, the reaction inside the battery cell is much more moderate after such an accident. This battery is thus significantly safer than one with a polymer separator. This is especially important in the mobile field.

p0023In addition, the separator according to the invention has a distinct price advantage

p0024Separators based on glass or ceramic fabrics, as described, for example, in <patcit id="pcit0006" dnum="DE10142622"><text>DE 101 42 622</text></patcit> to be discribed. In addition to the significantly different material costs, this is due to the fact that the polymer substrate is much easier to handle than glass or ceramic cloth, which nevertheless has a certain brittleness and is destroyed in careless handling. The entire manufacturing process is therefore more complex and thus more cost-intensive.

p0025Due to the nature of the nonwoven used, which has a particularly suitable combination of thickness and porosity, separators can be produced which meet the requirements for separators in high-performance batteries, in particular lithium high-performance batteries. By the simultaneous use of oxide particles precisely matched in their particle size for producing the porous ceramic coating, a particularly high porosity of the finished separator is achieved, the pores being still sufficiently small to prevent the growth of lithium whiskers through the separator.

p0026In order to achieve an ideal pore size or porosity of the separator, it has proved to be particularly advantageous to classify the oxide particles used prior to the suspension by means of winds in order to be able to use as large as possible oxide particles, since a commercially available metal oxide particle often does not There is an inconsiderable proportion of particles which are significantly smaller than the average particle size. However, the presence of a large number of smaller particles leads to the pores being partly reduced or completely closed by these small particles. The ideal pore size or porosity of the separator can then not always be achieved.

p0027Hydroclassing in the form of wet sieving can also be carried out in order to separate particles which are too large. The coarse fraction with up to 5% by weight of the total powder quantity has, in the worst case, particles which are larger than the total thickness of the separator. No defect-free coatings can be carried out with these powders. Consequently, these must be separated in all cases. The maximum particle size is preferably 1/3 to 1/5 and particularly preferably less than or equal to 1/10 of the nonwoven thickness.

p0028Furthermore, the particle-containing suspensions (slip) can be separated by classifying centrifugation in such a way that only the ideal particle fraction is obtained, which also has a very narrow particle size distribution.

p0029Due to the high porosity associated with the low thickness of the separator, it is also possible to soak the separator completely or at least almost completely with the electrolyte so that no dead spaces can occur in individual regions of the separator and thus in certain windings or laminations of the battery cells , In which no electrolyte is present. This is achieved in particular by the fact that by maintaining the particle size of the oxide particles, the separators obtained are free or virtually free of closed pores into which the electrolyte can not penetrate.

p0030The separators according to the invention also have the advantage that the anions of the conducting salt partly accumulate on the inorganic surfaces of the separator material, which leads to an improvement in the dissociation and thus to improved ionic conductivity in the high-current range. A further, not insignificant advantage of the separator according to the invention is the very good wettability. Due to the hydrophilic ceramic coating, the wetting with electrolytes takes place very rapidly, which also leads to a slightly improved conductivity.

p0031The advantages of the separator according to the invention can be summarized for use in high-power lithium-ion batteries:<ul><li>◆ High porosity</li><li>◆ Ideal pore width</li><li>◆ Low thickness of the separator</li><li>◆ Low weight</li><li>◆ Very good wetting behavior</li><li>◆ Improved dissociation of the conductive salt</li></ul>

p0032The separator according to the invention and a process for its production are described below, without the invention being restricted to these embodiments.

p0033The separator according to the invention, comprising a flexible nonwoven with a porous inorganic coating situated on and in this nonwoven, wherein the material of the nonwoven is selected from nonwoven, non-electrically conductive polymer fibers, characterized in that the nonwoven has a thickness of less than 30 μm , A porosity of more than 50%, preferably from 50 to 97%, and a pore radius distribution in which at least 50% of the pores have a pore radius of 75 to 150 μm.

p0034The separator according to the invention particularly preferably has a nonwoven which has a thickness of 5 to 30 μm, preferably a thickness of 10 to 20 μm. Particularly important for use in a separator according to the invention is a homogeneously distributed pore radius distribution in the nonwoven as stated above. An even more homogeneous pore radius distribution in the nonwoven, in conjunction with optimally matched oxide particles of a certain size, leads to an optimized porosity of the separator according to the invention.

p0035Preferably, the nonwoven has a porosity of 60 to 90%, more preferably 70 to 90%. The porosity is defined as the volume of the nonwoven (100%) minus the volume of the fibers of the nonwoven, ie, the proportion of the volume of the nonwoven which is not filled by material. The volume of the nonwoven can be calculated from the dimensions of the nonwoven. The volume of the fibers results from the measured weight of the nonwoven web under consideration and the density of the polymer fibers. The great porosity of the substrate also makes possible a higher porosity of the hybrid separator according to the invention, which is why a higher uptake of electrolytes can be achieved with the separator according to the invention. Preferred nonwovens are nonwovens of polymer fibers.

p0036In order to obtain a separator with insulating properties, the latter preferably has, as polymer fibers for the nonwoven, non-electrically conductive fibers of polymers which are preferably selected from polyacrylonitrile (PAN), polyesters such as, for example, polyethylene terephthalate and / or polyolefin (PO ), Such as, for example, polypropylene (PP) or polyethylene (PE) or mixtures of such polyolefins. The polymer fibers of the webs preferably have a diameter of from 0.1 to 10 μm, particularly preferably from 1 to 4 μm. Particularly preferred flexible nonwovens have a weight per unit area of ​​less than 20 g / m², Preferably from 5 to 10 g / m² on.

p0037The separators according to the invention preferably have a thickness of less than 35 μm, preferably less than 25 μm, particularly preferably a thickness of 15 to 25 μm. The thickness of the substrate has a great influence on the properties of the separator because on the one hand the flexibility but also the surface resistance Of the electrolyte-impregnated separator is dependent on the thickness of the substrate. Due to the small thickness, a particularly low electrical resistance of the separator is achieved 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.

p0038The separator according to the invention has a porous, electrically insulating, ceramic coating on and in the nonwoven. The porous inorganic coating on and in the nonwoven web preferably has oxide particles of the elements Al, Si and / or Zr with an average particle size of 0.5 to 7 μm, preferably of 1 to 5 μm and most preferably 1.5 To 3 μm. Particularly preferably, the separator has a porous inorganic coating which is located on and in the nonwoven, the aluminum oxide particles having an average particle size of 0.5 to 7 μm, preferably of 1 to 5 μm and most preferably of 1.5 to 3 μm Bonded to an oxide of the elements Zr or Si. In order to achieve as high a porosity as possible, preferably more than 50% by weight and particularly preferably more than 80% by weight of all particles are within the above-mentioned limits of the average particle size. As already described above, the maximum particle size is preferably 1/3 to 1/5 and particularly preferably less than or equal to 1/10 of the thickness of the nonwoven used.

p0039The separator preferably has a porosity of from 30 to 80%, preferably from 40 to 75% and particularly preferably from 45 to 70%. The porosity refers to the open, ie open, pores. The porosity can be determined by means of the known method of mercury porosimetry or can be calculated from the volume and the density of the starting materials used if it is assumed that only open pores are present.

p0040The separators according to the invention are distinguished by the fact that they can have a tensile strength of at least 1 N / cm, preferably of at least 3 N / cm 3 and most preferably 3 N 10 / cm 3. The separators according to the invention can preferably be bent without damage down to every radius down to 100 m, preferably down to 50 mm and very particularly preferably down to 1 mm. The high tear strength and the good bendability of the separator according to the invention has the advantage that changes in the geometries of the electrodes occurring during the charging and discharging of a battery can be accompanied by the separator without the latter being damaged. Bendability also has the advantage that commercially standardized winding cells can be produced with this separator. In these cells, the electrode / separator layers are spirally wound up and contacted with each other in a standardized size.

p0041It may be advantageous if the separator has a non-inherent shut-down mechanism. This can be realized, for example, by providing a very thin wax or polymer particle layer on or in the separator, which melt at a desired shut-off temperature, so-called shut-off particles. Particularly preferred materials from which the shutdown particles may be are, for example, natural or artificial waxes or low-melting polymers, such as, for example, polyolefins, the material of the cut-off particles being selected such that the particles melt at the desired cut-off temperature and the pores of the separator So that a further ion flow is prevented.

p0042The shutdown particles preferably have an average particle size (i.e._w) Greater than or equal to the mean pore size (i.e._s) Of the pores of the porous inorganic layer of the separator. This is particularly advantageous because such penetration and sealing of the pores of the separator layer, 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, is prevented. The thickness of the cut-off particle layer is only critical insofar as the too thick layer would unnecessarily increase the resistance in the battery system. In order to achieve a safe shutdown, the cut-off particle layer should have a thickness (e.g._w) Which is approximately equal to the mean particle size of the shutdown particles (D_w) Up to 10 D_w, Preferably of 2 D_w to D_w By weight. A separator equipped in this way has a primary safety feature. However, in contrast to the purely organic separator materials, this separator can not completely melt and thus it can not come to meltdown. These safety features are very important due to the very high energy levels for high energy batteries and are therefore often required.

p0043The separator according to the invention is preferably obtainable by a process for the production of a separator which is characterized in that in and on a flexible nonwoven having a thickness of less than 30 μm, a porosity of more than 50%, preferably from 50 to 97% And a pore radius distribution in which at least 50% of the pores have a pore radius of 75 to 150 μm, a porous inorganic coating is applied by applying a suspension and at least once heating, in which the suspension is solidified on and in the nonwoven The suspension comprises metal oxide particles and at least one sol, and the material of the nonwoven is selected from non-woven, non-electrically conductive polymer fibers. The suspension preferably has metal oxide particles with an average particle diameter of 0.5 to 7 μm, preferably of 1 to 5 μm, and most preferably of 1.5 to 3 μm, of the metals Al, Zr and / or Si and at least one sol.

p0044The method itself is basically off <patcit id="pcit0007" dnum="WO9915262A"><text>WO 99/15262</text></patcit> But not all parameters or starting materials, in particular non-electrically conductive starting materials, can be used for the preparation of the separator according to the invention. In particular, the particles used for the preparation of the dispersion as well as the webs used as substrate differ significantly from the previously described feedstocks.

p0045The suspension can, for example, be applied to and into the nonwoven by pressing, pressing, pressing in, rolling up, spreading, spreading, dipping, spraying or pouring onto the nonwoven.

p0046The nonwoven used preferably has a thickness of less than 20 μm, preferably less than 15 μm and particularly preferably a thickness of 7.5 to 15 μm. Particularly preferred nonwovens are those used as described in the description of the separator according to the invention.

p0047The nonwoven used is preferably a nonwoven of polymer fibers or a nonwoven which at least has polymer fibers. The polymer fibers are preferably selected from polyacrylonitrile, polyesters, such as, for example, polyethylene terephthalate, and / or polyolefins. However, all other known polymer fibers can also be used, provided they have both the temperature stability required for the manufacture of the separators and are stable under the operating conditions in the lithium battery. The separator according to the invention preferably has polymer fibers which have a softening temperature of more than 100 ° C. and a melting temperature of more than 110 ° C. It can be advantageous if the polymer fibers have a diameter of 0.1 to 10 μm, preferably of 1 to 5 μm.

p0048The suspension used for the coating has at least one sol of the elements Al, Zr and / or Si and is prepared by suspending oxide particles in at least one of these sols. The sols can be obtained by hydrolyzing at least one compound with water or an acid or a combination of these compounds. It may be advantageous to add the compound to be hydrolyzed to alcohol or an acid or a combination of these liquids prior to hydrolysis. A nitrate, a chloride, a carbonate, an alcoholate of the elements Al, Zr and / or Si are preferably hydrolyzed as the compound to be hydrolyzed. The hydrolysis is preferably carried out in the presence of water, water vapor, ice or an acid, or a combination of these compounds.

p0049In an embodiment variant of the process according to the invention, particulate sols are prepared by hydrolysis of the compounds to be hydrolyzed. These particulate sols are distinguished by the fact that the compounds formed in the sol by hydrolysis are particulate. The particulate sols may be as described above or as described in<patcit id="pcit0008" dnum="WO9915262A"><text>WO 99/15262</text></patcit> Can be prepared. These brine 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 prior to hydrolysis. The hydrolyzed compound can be treated with at least one organic or inorganic acid, preferably with a 10-60% organic or inorganic acid, more preferably a mineral acid selected from sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid and nitric acid or a mixture of these acids will. The particulate sols prepared in this way can subsequently be used for the preparation of suspensions, the preparation of suspensions being preferred for application to polymer-based polymer fibers pretreated with polymeric sol.

p0050In a further embodiment variant of the process according to the invention, polymeric sols are prepared by hydrolysis of the compounds to be hydrolyzed. In this preferred embodiment variant of the process according to the invention, the sol has a proportion of water and / or acid of less than 50% by weight. These polymeric sols are distinguished by the fact that the compounds formed in the sol by hydrolysis are polymer (thus crosslinked in chain form over a larger 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 reach 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 is mixed with the 0.5 to 10-fold molar ratio and preferably with half the molar ratio of water, water vapor or ice, Hydrolyzable group, the hydrolyzable compound. Up to 10 times the amount of water can be used in the case of very slowly hydrolyzing compounds, for example tetraethoxysilane. Very rapidly hydrolyzing compounds, such as the zirconium tetraethylate, can already form particulate sols under these conditions, which is why the 0.5-fold 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 results in good results. Where a reduction of the preferred amount of half a molar ratio is more than 50% possible, but not very useful, since when this value is lower, the hydrolysis is no longer complete and coatings based on such brine are not very stable.

p0051For the preparation of sols with a desired very small proportion of water and / or acid in the sol, it can be advantageous if the compound to be hydrolyzed is dissolved in an organic solvent, in particular ethanol, isopropanol, butanol, amyl alcohol, hexane, cyclohexane, ethyl acetate and mixtures Of these compounds, before the actual hydrolysis is carried out. A sol prepared in this way can be used to prepare the suspension according to the invention.

p0052Both particulate brine (high water content, low solvent content) and polymeric brine (low water content, high solvent content) can be used as the sol in the process according to the invention for preparing the suspension. In addition to the sols which are obtainable as just described, it is also possible in principle to use commercially available sols, such as, for example, zirconium nitrate sol or silicasol. The process of preparing separators by applying and solidifying a suspension to a carrier is by itself isolated<patcit id="pcit0009" dnum="DE10142622"><text>DE 101 42 622</text></patcit> And in a similar form <patcit id="pcit0010" dnum="WO9915262A"><text>WO 99/15262</text></patcit> But not all parameters or ingredients can be transferred to the production of the membrane according to the invention. The process that takes place in<patcit id="pcit0011" dnum="WO9915262A"><text>WO 99/15262</text></patcit> Can not be transferred to polymeric nonwoven materials in this form, in particular, since the very water-containing sol systems described therein often do not permit thorough wetting of the usually hydrophobic polymer webs in the depth since the very water-containing sol systems do not or only poorly moisten most polymer webs . It has been found that even the smallest non-wetted areas in the nonwoven material can lead to the obtaining of membranes or separators which have defects and are thus unusable.

p0053Surprisingly, it has now been found that a sol system or a suspension, which has been adapted to the polymers in the wetting behavior, is completely impregnated with the nonwoven materials and thus defect-free coatings are obtainable. Preferably, the wetting behavior of the sol or the suspension is therefore adjusted in the process according to the invention. This adjustment is preferably carried out by the preparation of sols or suspensions, these sols comprising one or more alcohols such as, for example, methanol, ethanol or propanol or mixtures thereof, and / or aliphatic hydrocarbons. However, other solvent mixtures are also conceivable which can be added to the sol or the suspension in order to adapt these to the fleece used in the crosslinking behavior.

p0054The proportion by mass of the suspended component (metal oxide particles) on the suspension is preferably from 1 to 100 times, more preferably from 1 to 50 times and most preferably from 1 to 10 times the sol employed. Particularly preferably, aluminum oxide particles which preferably have a mean particle size of 0.5 to 7 μm are used as metal oxide particles for the preparation of the suspension. Aluminum oxide particles in the range of the preferred particle sizes are, for example, produced by the company Martinswerke under the names MDS 6; DN 206, MZS 3 and MZS 1 and from Alcoa with the designation CL3000 SG, CT800 SG and HVA SG.

p0055It has been found that the use of commercially available metal oxide particles can lead to unsatisfactory results, since a very large grain size distribution is frequently present. For this reason, metal oxide particles which have been classified by a conventional method such as, for example, winding, centrifuging and hydroclassing are preferably used. Preference is given to using, as metal oxide particles, fractions in which the coarse grain fraction, which accounts for up to 10% of the total quantity, was separated by wet sieving. This interfering coarse grain fraction, which can not be comminuted, or is only very difficult to crush, even by means of the methods typical of the slurry production (ball mill, attritor mill, mortar mill), dispersing (ultra-turrax, ultrasound) Eg consist of aggregates, hard agglomerates, grinding ball abrasion. The above-mentioned measures ensure that the inorganic porous layer has a very uniform pore size distribution. This is achieved in particular by using metal 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.

p0056The following Table 1 gives an overview of how the choice of the different aluminum oxides affects the porosity and the resulting pore size of the respective porous inorganic coating. To determine these data, the corresponding slurries (suspensions) were prepared and dried and solidified as a pure molded body at 200 ° C.<tables id="tabl0001" num="0001"><table frame="all"><title>Table 1: Typical data of ceramics depending on the type of powder used</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="62mm" /><colspec colnum="2" colname="col2" colwidth="24mm" /><colspec colnum="3" colname="col3" colwidth="37mm" /><thead><row><entry valign="top">Al₂O₃-Type</entry><entry valign="top">Porosity /%</entry><entry valign="top">Average Pore ​​size / nm</entry></row></thead><tbody><row><entry>AlCoA CL3000SG</entry><entry>51.0</entry><entry>755</entry></row><row><entry>AlCoA CT800SG</entry><entry>53.1</entry><entry>820</entry></row><row><entry>AlCoA HVA SG</entry><entry>53.3</entry><entry>865</entry></row><row><entry>AlCoA CL4400FG</entry><entry>44.8</entry><entry>1015</entry></row><row><entry>Martinsw. DN 206</entry><entry>42.9</entry><entry>1025</entry></row><row><entry>Martinsw. MDS 6</entry><entry>40.8</entry><entry>605</entry></row><row><entry>Martinsw. MZS 1 + Martinsw. MZS "3" = 1: 1</entry><entry>47%</entry><entry>445</entry></row><row><entry>Martinsw. MZS 3</entry><entry>48%</entry><entry>690</entry></row></tbody></tgroup></table></tables>

p0057In order to improve the adhesion of the inorganic components to polymer fibers as substrate, it may be advantageous to add adhesion promoters, for example organofunctional silanes, to the suspensions used. Suitable adhesion promoters are, in particular, compounds selected from the octylsilanes, the vinyl silanes, the amine-functionalized silanes and / or the glycidyl-functionalized silanes, such as, for example, the dynasilanes from Degussa. Particularly preferred adhesion promoters for polyethylene (PE) and polypropylene (PP) are vinyl, methyl and octylsilanes, wherein an exclusive use of methylsilanes is not optimal, for polyamides and polyamines are amine-functional silanes, for polyacrylates and polyesters, there are glycidyl functionalised Silanes and for polyacrylonitrile, it is also possible to use glycidyl-functionalized silanes. Other adhesion promoters can also be used, but these must be matched to the respective polymers. The adhesion promoters must be selected in such a way that the solidification temperature is below the melting or softening point of the polymer used as substrate and below its decomposition temperature. Suspensions according to the invention preferably comprise very much less than 25% by weight, preferably less than 10% by weight, of compounds which can act as adhesion promoters. An optimum proportion of adhesion promoter is obtained by coating the fibers and / or particles with a monomolecular layer of the adhesion promoter. The quantity of adhesion promoter in grams required for this purpose can be determined by multiplying the amount of the oxides used or the fibers (in g) with the specific surface area of ​​the materials (in m²G^-1) And then dividing by the specific space requirement of the adhesion promoters (in m² G^-1), Whereby the specific space requirement is often in the order of 300 to 400 m² G^-1 lies.

p0058The following Table 2 contains an exemplary overview of adhesion promoters based on organofunctional Si compounds for typical polymers used as nonwoven material. <tables id="tabl0002" num="0002"><table frame="all"><title>Table 2</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="55mm" /><colspec colnum="2" colname="col2" colwidth="57mm" /><colspec colnum="3" colname="col3" colwidth="55mm" /><thead><row><entry valign="top">polymer</entry><entry valign="top">Organ function type</entry><entry valign="top">Haflvermittler</entry></row></thead><tbody><row><entry morerows="1" rowsep="1">PAN</entry><entry>glycidyl</entry><entry>GLYMO</entry></row><row><entry>methacryl</entry><entry>MEMO</entry></row><row><entry>PA</entry><entry>Amino</entry><entry>AMEO, DAMO</entry></row><row><entry morerows="1" rowsep="1">PET</entry><entry>methacryl</entry><entry>MEMO</entry></row><row><entry>vinyl</entry><entry>VTMO, VTEO, VTMOEO</entry></row><row><entry morerows="2" rowsep="1">PE, PP</entry><entry>Amino</entry><entry>AMEO, AMMO</entry></row><row><entry>vinyl</entry><entry>VTMO, VTEO, Silfin</entry></row><row><entry>methacryl</entry><entry>MEMO</entry></row></tbody></tgroup><tgroup cols="3" rowsep="0"><colspec colnum="1" colname="col1" colwidth="55mm" /><colspec colnum="2" colname="col2" colwidth="57mm" /><colspec colnum="3" colname="col3" colwidth="55mm" /><tbody><row><entry namest="col1" nameend="col3" align="justify">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</entry></row></tbody></tgroup></table></tables>

p0059In a particular embodiment of the process according to the invention, the abovementioned adhesion promoters are applied to polymer fleece (substrate) in an upstream step. For this purpose, the adhesion promoters are dissolved in a suitable solvent, such as, for example, ethanol. This solution may also contain a small amount of water, preferably from 0.5 to 10 times the molar amount of the hydrolyzable group, and small amounts of an acid such as HCl or HNO₃, As a catalyst for the hydrolysis and condensation of the Si-OR groups. This solution is applied to the substrate by the known techniques, such as spraying, imprinting, pressing, pressing-on, spraying-on, pressing-on, pressing, spraying or pouring on, by means of a temperature treatment at 50 ° to a maximum of 350 ° C. on the substrate Substrate. Only after application of the adhesion promoter does the application and solidification of the suspension take place in this embodiment variant of the process according to the invention.

p0060By applying an adhesion promoter before the actual application of the suspension, the adhesion behavior of the substrates can be improved, in particular, against aqueous, particulate sols, which is why substrates thus pretreated in particular can be coated with suspensions based on commercially available sols such as, for example, zirconium nitrate sol or silica sol . However, this procedure of applying an adhesion promoter also means that the manufacturing process of the separator according to the invention must be extended by an intermediate or pretreatment step. However, this is also possible, however, more costly than the use of suitable sols to which adhesion promoters have been added, but also has the advantage that better results are also obtained when using suspensions based on commercially available sols.

p0061The coatings according to the invention are brought into and onto the nonwoven by solidifying the suspension in and on the nonwoven. According to the invention, the suspension present on and in the nonwoven can be solidified by heating to from 50 to 350 ° C. Since, when using polymeric substrate materials, the maximum temperature is predetermined by the nonwoven, it is to be adapted accordingly. Thus, depending on the embodiment of the process according to the invention, the suspension present on and in the nonwoven is solidified by heating to 100 to 350 ° C. and most preferably by heating to 110 to 280 ° C. It can vort be eilhaft when the heating is carried out for 1 second to 60 minutes at a temperature of 100 to 350 ° C. Particular preference is given to heating the suspension for solidification to a temperature of 110 to 300 ° C., very particularly preferably at a temperature of 110 to 280 ° C. and preferably for 0.5 to 10 min.

p0062The heating of the composite according to the invention can be carried out by means of heated air, hot air, infrared radiation or other heating methods according to the prior art.

p0063The process according to the invention can, for example, be carried out in such a way that the polymer nonwoven is unrolled from a roll as a substrate, at a rate of from 1 m / h to 2 m / s, preferably at a speed of 0.5 m / To at least one apparatus which brings the suspension onto and into the substrate, such as, for example, a roller, and at least one further apparatus. (DE). WIPO Home services World Intellectual Property Organization , Which allows the suspension to solidify on and in the support by heating, such as an electrically heated furnace, and the separator so produced is rolled up on a second roll. In this way, it is possible to produce the separator according to the invention by the continuous process. The pretreatment steps can also be carried out in a continuous process while retaining the above-mentioned parameters.

p0064It has proven to be particularly advantageous if the process is carried out in such a way that the nonwoven, in particular the polymer nonwoven, has a maximum stress in the longitudinal direction of 10 N / cm 3, preferably 3 N / cm, during the coating process or the coating processes. In this context, coating processes are understood to be all process steps in which a material is applied to and into the substrate and is solidified there by heat treatment, that is to say also the application of the adhesion promoter. Preferably, the substrate is tensioned during the coating processes with a maximum force of 0.01 N / cm. It may be particularly preferred if the substrate is guided untensioned in the longitudinal direction during the coating process or the coating processes.

p0065By controlling the tensile stress during the coating, it is possible to prevent a deformation (also elastic) of the carrier material from taking place. The ceramic coating can not follow the non-woven material due to a possible deformation (elongation) if the tensile stress is too high, which causes the coating to dissolve from the nonwoven material over the entire surface. The resulting product can then not be used as intended.

p0066If the separator according to the invention is to be equipped with an additional automatic shut-off mechanism, this can be done, for example, by the fact that, after solidification of the suspension applied to the substrate, a layer of particles melting at a desired temperature and closing the pores of the separator, So-called cut-off particles, is applied to the separator for producing a shut-off mechanism and fixed. The layer of shut-off particles can be produced, for example, by applying a suspension of wax particles having an average particle size greater than the mean pore size of the separator in a sol, water, solvent or solvent mixture.

p0067The suspension for the application of the particles preferably contains from 1 to 50% by weight, preferably from 5 to 40% by weight and very particularly preferably from 10 to 30% by weight, of separating particles, in particular wax particles, in the suspension.

p0068Since the inorganic coating of the separator often has a very hydrophilic character, it has been found to be advantageous if the coating of the separator was prepared using a silane in a polymeric sol as an adhesion promoter and thus was rendered hydrophobic. In order to achieve a good adhesion and uniform distribution of the shut-off particles in the shut-off layer also on hydrophilic porous inorganic separator layers, several variants are possible.

p0069In an embodiment variant of the process according to the invention, it has proved to be advantageous to hydrophobize the porous inorganic layer of the separator before the application of the shutdown particles. The production of hydrophobic membranes, which functions according to the same principle, is described, for example, in<patcit id="pcit0012" dnum="WO9962624A"><text>WO 99/62624</text></patcit> Described. Preferably, the porous inorganic coating is rendered hydrophobic by treatment with alkyl, aryl or fluoroalkylsilanes, as marketed, for example, under the name Markennamen Dynasilan by Degussa. It is possible, for example, to use the known methods of hydrophobing, which are used, inter alia, for textiles (<nplcit id="ncit0002" npl-type="s"><text>D. Knittel; E. Schollmeyer; Melliand Textilber. (1998) 79 (5), 362-363</text></nplcit>) "<i>,</i> With slight modification of the formulations, can also be used for the porous coatings of the separator. For this purpose, the coating or the separator is treated with a solution which has at least one hydrophobic substance. It may be advantageous if the solution comprises, as a solvent, 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 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 is from 40 to 100% by volume. To the solution, 0.1 to 30% by weight, preferably 1 to 10% by weight, of a hydrophobic substance are added to the solvent. Suitable hydrophobic substances are, for example, the silanes listed above. Surprisingly, good hydrophobization takes place not only with highly hydrophobic compounds, such as, for example, with triethoxy (3,3,4,4,5,5,6,6,7,7,8,8-tridecafluorooctyl) silane, but rather with one Treatment with methyltriethoxysilane or isobutyltriethoxysilane is completely sufficient to achieve the desired effect. For the even distribution of the hydrophobic substances in the solution, the solutions are stirred at room temperature and subsequently applied to the inorganic coating of the separator and dried. Drying can be accelerated by treatment at temperatures of 25 to 100 ° C.

p0070In a further embodiment variant of the method according to the invention, the porous inorganic coating can also be treated with other adhesion promoters before the application of the shut-off particles. The treatment with one of the abovementioned adhesion promoters can then likewise 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.

p0071The layer of cut-off particles is preferably produced by applying a suspension of cut-off particles in a suspension medium selected from a sol, water or solvent, such as alcohol, ether or ketones, or a solvent mixture onto the inorganic coating of the separator and subsequent drying. The particle size of the shut-off particles present in the suspension is, in principle, arbitrary. However, it is advantageous if shut-off particles with an average particle size (D._w) Is greater than or equal to, preferably greater than, the average pore size of the pores of the porous inorganic layer (i.e._s), Since this ensures that the pores of the inorganic layer are not blocked by cut-off particles during the production of the separator according to the invention. The shutdown particles used preferably have an average particle size (i.e._w) Larger than the average pore diameter (i.e._s) And less than 5 d_s, Particularly preferably less than 2 d_s By weight.

p0072If it is desired to use cut-off particles which have a particle size smaller than the pore size of the pores of the porous inorganic layer, the particles must be prevented from penetrating into the pores of the porous inorganic separator layer. Reasons for the use of such particles can be, for example, in large price differences but also in the availability of such particles. One way of preventing penetration of the shut-off particles into the pores of the porous inorganic layer is to adjust the viscosity of the suspension such that no penetration of the suspension into the pores of the inorganic layer of the separator occurs in the absence of external shear forces. Such a high viscosity of the suspension can be achieved, for example, by adding auxiliaries which influence the flow behavior, for example silicas (Aerosil, Degussa) to the suspension. When using auxiliaries such as, for example, Aerosil 200, a proportion of 0.1 to 10% by weight, preferably 0.5 to 50% by weight, of silica, based on the suspension, is often sufficient to achieve a sufficiently high viscosity Of the suspension. The proportion of auxiliaries can in each case be determined by simple preliminary tests.

p0073It may be advantageous if the suspending agent-comprising suspension comprises adhesion promoters. Such a suspensions-containing suspension can be applied directly to an inorganic layer of the separator, even if it has not been rendered hydrophobic before application. Of course, a suspensions-containing suspension can also be applied to a hydrophobic layer or to a separator layer, in the preparation of which an adhesion promoter was used. Silanes which have amino, vinyl or methacrylic side groups are preferably used as adhesion promoters in the suspension having shutoff particles. Such adhesion promoters are, for example, AMEO (3-aminopropyltriethoxysilane), MEMO (3-methacryloxypropyltrimethoxysilane), silfin (vinylsilane + initiator + catalyst), VTEO (vinyltriethoxysilane) or VTMO (vinyltrimethoxysilane). Such silanes are also available, for example from Degussa, in aqueous solution under the designation Dynasilan 2926, 2907 or 2781. A proportion of a maximum of 10% by weight of adhesion promoter has proven to be sufficient for ensuring a sufficiently high adhesion of the cut-off particles to the porous inorganic layer. Preference is given to suspensions comprising suspending agents, comprising 0.1 to 10% by weight, preferably from 1 to 7.5% by weight, and most preferably from 2.5 to 5% by weight, of adhesion promoters, based on the suspension .

p0074All particles which have a defined melting point can be used as shut-off particles. The material of the particles is selected according to the desired cut-off temperature. Since relatively low switch-off temperatures are desired for most batteries, it is advantageous to use such switch-off particles which are selected from particles of polymers, polymer mixtures, natural and / or artificial waxes. Particularly preferred are cut-off particles

p0075Particles made of polypropylene or polyethylene wax.

p0076The suspension comprising the shutdown particles can be applied to the porous inorganic layer of the separator by printing, pressing, pressing, rolling up, doctoring, spreading, dipping, spraying or pouring onto the porous inorganic layer. The shut-off layer is preferably obtained by drying the prepared suspension at a temperature of from room temperature to 100 ° C., preferably from 40 to 60 ° C.

p0077It may be advantageous if the shut-off particles are fixed after application to the porous inorganic layer by at least one-time heating to a temperature above the glass transition temperature so that melting of the particles is achieved without changing the actual shape. In this way it can be achieved that the shut-off particles adhere particularly well to the porous inorganic separator layer.

p0078The suspension comprising the shutdown particles, followed by drying, and a possible heating via the glass transition temperature, can be carried out continuously or quasi-continuously. If a flexible separator is used as starting material, this can in turn be unwound from a roll, passed through a coating, drying and optionally heating apparatus and then rolled up again.

p0079Hybrid separators according to the invention can be used as separators in batteries. When the separator according to the invention is used as a separator in batteries, the separator is usually placed soaked with the electrolyte between the anode and the cathode.

p0080The separator according to the invention is suitable for primary and secondary (rechargeable) lithium batteries, for nickel metal hydride, nickel-cadmium, silver-zinc and zinc-air batteries. Due to its particularly high porosity and the large pores, the separator according to the invention is particularly suitable for use in lithium high-capacity batteries.

p0081In addition to batteries which have a separator according to the invention, the present invention therefore relates, in particular, to lithium high-performance batteries which have a separator according to the invention.

p0082The separators according to the invention are also suitable for use in batteries which are to be charged quickly. Such high-performance batteries can be charged very quickly, but can also be discharged. The optimized properties of the separator with regard to thickness, pore radius, porosity and, as a result, the high ion conductivity of the separator impregnated with electrolyte, are particularly advantageous here. Due to the high temperature resistance of the separator according to the invention, a battery equipped with this separator is not so temperature-sensitive and can therefore tolerate the temperature rise due to the rapid charge without negative changes of the separator or without damage to the battery. Consequently, these batteries are much faster to recharge.

p0083This is a significant advantage in the use of such batteries in electric vehicles, since they are no longer required to be charged for several hours, but charging can be carried out within about one hour or less than an hour.

p0084The present invention is described by the following examples without being limited thereto.

Example 1 Preparation of an S450PET Separator

p0085160 g of ethanol are initially charged with 15 g of a 5% strength by weight aqueous HCl solution, 10 g of tetraethoxysilane, 2.5 g of methyltriethoxysilane and 7.5 g of Dynasilan GLYMO (manufacturer of all Dynasilanes: Degussa AG). In this sol, which was first stirred for several hours, 125 g of the aluminum oxides Martoxid MZS-1 and Martoxid MZS-3 (manufacturer of both aluminas: Martinswerke) are then suspended in each case. This slurry is homogenized for at least a further 24 h with a magnetic stirrer, the stirrer vessel having to be covered in order to prevent loss of solvent.

p0086A PET nonwoven fabric having a thickness of about 30 μm and a basis weight of about 20 g / m² Is coated with the above slurry in a continuous rolling-on process (belt speed approx. 8 m / h, T = 200 ° C.). In this rolling process, the slurry is rolled onto the nonwoven by means of a roller which moves in the opposite direction to the direction of the belt (movement direction of the nonwoven). The nonwoven then passes through a furnace having the stated temperature. In the subsequent experiments, the same method or arrangement is used for coating. A separator with an average pore width of 450 nm and a thickness of approximately 50 μm is obtained. The Gurley number is about 6.

p0087A massive molded body is produced in parallel with the above slurry and likewise dried at 200 ° C. and solidified. The porosity is about 47%, the average pore size is 450 nm.

Example 2: Preparation of an S750PET Separator

p0088To 130 g of water and 30 g of ethanol, 30 g of a 5% strength by weight aqueous HNO₃Solution, 10 g of tetraethoxysilane, 2.5 g of methyltriethoxysilane and 7.5 g of Dynasilan GLYMO (manufacturer of all Dynasilanes: Degussa AG). In this sol, which was first stirred for several hours, 260 g of CL3000 SG (manufacturer: AlCoA) are then suspended. This slurry is homogenized for at least a further 24 h with a magnetic stirrer, the stirrer vessel having to be covered in order to prevent loss of solvent. Before coating, this slurry is filtered through a 20 μm sieve in order to remove the coarse grain fraction.

p0089A PET nonwoven fabric having a thickness of about 15 μm and a basis weight of about 6 g / m² Is coated with the above slurry in a continuous rolling-on process (belt speed approx. 8 m / h, T = 200 ° C.). A separator with an average pore width of 755 nm and a thickness of 30 μm is obtained. The Gurley number is about 3.

p0090A massive shaped body is produced in parallel with the above slurry and likewise dried at 200 ° C. and solidified. The porosity is about 51%, the average pore size is 755 nm.

Example 3 Preparation of an S850PET Separator

p0091To 145 g of water and 15 g of ethanol are first added 30 g of a 5% by weight aqueous HNO₃Solution, 10 g of tetraethoxysilane, 2.5 g of methyltriethoxysilane and 7.5 g of Dynasilan GLYMO (manufacturer of all Dynasilanes: Degussa AG). In this sol, which was first stirred for several hours, 280 g of HVA SG (manufacturer: AlCoA) are then suspended. This slurry is homogenized for at least a further 24 h with a magnetic stirrer, the stirrer vessel having to be covered in order to prevent loss of solvent. Before coating, this slurry is filtered through a 15 μm sieve in order to remove the coarse grain fraction.

p0092A PET nonwoven fabric having a thickness of about 15 μm and a basis weight of about 6 g / m² Is coated with the above slurry in a continuous rolling-on process (belt speed approx. 8 m / h, T = 200 ° C.). A separator with an average pore width of 865 nm and a thickness of 30 μm is obtained. The Gurley number is about 2.

p0093A massive shaped body is produced in parallel with the above slurry and likewise dried at 200 ° C. and solidified. The porosity is about 53%, the average pore size is 865 nm.

EXAMPLE 4 Li-ion battery with a hybrid ceramic separator

p0094An S450PET separator prepared according to Example 1 is placed in a Li-ion cell consisting of a positive mass as LiCoO₂, A negative mass consisting of graphite and an electrolyte of LiPF₆ In ethylene carbonate / dimethyl carbonate, [LiCoO2 // S-450-PET, EC / DMC 1: 1, 1M LiPF₆ // graphite]. The charging and discharging behavior of this battery was checked. After approximately 250 cycles (charging / discharging with C / 5), the battery shows only a small drop in capacity by a few percentage points. Also, an increase in the charging voltage from 4.1 to 4.2 volts in the 200th charging cycle does not damage the battery.

p0095We use this battery but with C (approx. 3 mA / cm²) Are discharged, the entire capacity can not be discharged at these high currents. This is due to the still high internal resistance.

EXAMPLE 5 Li-ion battery with a hybrid ceramic separator

p0096An S850PET separator prepared according to Example 3 is immersed in a Li-ion cell consisting of a positive mass of LiCoO₂, A negative mass consisting of graphite and an electrolyte of LiPF₆ In ethylene carbonate / dimethyl carbonate, [LiCoO2 // S-450-PET, EC / DMC 1: 1, 1M LiPF₆ // graphite]. The charging and discharging behavior of this battery was checked. After approximately 250 cycles (charging / discharging with C / 5), the battery shows only a small drop in capacity by a few percentage points. Also, an increase in the charging voltage from 4.1 to 4.2 volts in the 200th charging cycle does not damage the battery.

p0097We use this battery with C (approx. 3 mA / cm²) Are discharged, practically the entire capacity of the battery can be discharged at these high currents. This is due to the higher porosity, the smaller thickness, the larger pore size, and the associated internal resistance, as compared to Example 4.

p0098This separator is therefore particularly suitable for a high-current battery.