EP2483951A1

EP2483951A1 - Electrochemical energy store comprising a separator

Info

Publication number: EP2483951A1
Application number: EP10760899A
Authority: EP
Inventors: Annette Heusser-Nieweg; Peter Terstappen
Original assignee: Oxyphen AG
Current assignee: Oxyphen AG
Priority date: 2009-10-02
Filing date: 2010-09-28
Publication date: 2012-08-08
Also published as: CH701976A2; CN102598359A; WO2011038521A1; WO2011038521A8; US20120189917A1

Abstract

An electrochemical energy store comprising a separator (40, 40a, 40b) is described, wherein said electrochemical energy store has a positively charged electrode (20), a negatively charged electrode (30), an electrolyte, and a porous separator (40, 40a, 40b) which separates the positively charged electrode (20) and the negatively charged electrode (30) from each other. The separator (40, 4a, 40b) includes at least one microporous foil which is produced using ion irradiation, among other things. The separator (40, 40a, 40b) further includes ion ducts (43) extending at different angles from one another.

Description

TITLE

Electrochemical energy storage with separator

TECHNICAL FIELD The present invention relates to an electrochemical energy storage device having a positively charged electrode, a negatively charged electrode, and a porous separator. The porous formed separator serves to separate the positively charged electrode and the negatively charged electrode from each other. STATE OF THE ART

Various types of electrochemical energy storage are known from the prior art, which serve to provide power to electrically operated devices. Such energy stores are commonly referred to as batteries or accumulators (or rechargeable batteries). When discharging the battery, the chemical energy is converted into electrical energy by an electrochemical redox reaction. The latter can be used by a connected to the electrochemical energy storage electrical load in a variety of ways. Electrochemical energy stores can be generally divided into a first group of non-rechargeable primary batteries and a second group of rechargeable secondary batteries. Secondary batteries can be brought back into a state of charge after discharge, which largely corresponds to the original state of charge before discharge, so that a multiple conversion of chemical to electrical energy and back is possible.

Essential quality criteria of primary as well as secondary batteries are high energy density, good thermal stability and providing a constant voltage over the discharge period. Furthermore, preferred batteries do not have a so-called "memory effect", which means that they will not lose capacity even with multiple charge / discharge operations, and the raw materials used in the batteries should be sufficiently abundant in nature, which also makes these types of batteries are inexpensive to produce in the long term.

The mode of operation of batteries is based on an electrochemical redox reaction known to the person skilled in the art, wherein during the battery discharge at a positively charged electrode (cathode) reducing processes take place and at a negatively charged electrode (anode) oxidizing processes. Thus, there is an ion transport that takes place within an electrolyte, where the process of a rechargeable secondary battery can be reversed to recharge the battery. In order to separate the anode and the cathode spatially and electrically, a separator is inserted in the battery. This is wetted with the electrolyte and has the particular task of preventing electrical short circuits within the battery, but at the same time it must be permeable to ions in order to ensure the electrochemical reactions can.

The separator thus represents an important element which significantly influences the properties of the battery. The internal resistance, the charge capacity, the charge / discharge current and other electrical properties of the battery are largely determined by the separator. The separator should be mechanically stable and have good ion permeability. In addition to a high energy density, the requirements of batteries also include, in particular, a high power density in order to be able to provide a large amount of energy within a short time. However, the power density is influenced in particular by the permeability of the separator. The separator should therefore be designed so that it allows the largest possible amount of ions per unit time. Among other things, therefore, the thickness of the separator should be as small as possible. In addition, the separator should be well wettable, stable in the long term with respect to the chemicals and solutions found in the battery, and be insensitive to temperature variations such as may occur in batteries. The prior art mainly uses separators based on polyolefins. However, these have the disadvantage that they are sensitive to elevated temperatures and in particular to temperatures above 150 ° C. Thus, the melting temperature of polyolefins is relatively low, and such a separator formed has a low dimensional stability with respect to heating. This can cause short circuits within the battery, which in turn cause a rise in temperature. The battery is permanently damaged. Especially in the field of high-performance batteries or external short circuits occur, however, very strong internal heating can occur, which should be withstood by the separator so as not to irreversibly damage the battery.

EP 0 851 523 discloses a separator consisting of a polyethylene terephthalate (PET) nonwoven based film. The thermal stability of this film is significantly increased compared to the polyolefin-based separators. Other such purely PET-based separators are also described in US 2003/0190499 and US 2006/0019164. A disadvantage of such separators, however, affect the relatively large pores, which have an average diameter of 5 μιη to 15 μιη. The scattering of the pore diameter is also large, which can form short-circuit currents, especially in the range of larger pores. In addition, due to its fleece-like structure, the separator does not have well-defined ion channels but a spongy texture. As a result, the path of the ions from one side to the other of the separator film acting as a depth filter is substantially extended, and the pore size accordingly varies greatly both in the direction through the separator and over the surface of the separator. Another known problem of such separators is the so-called dendrite growth. In this case, starting from the electrodes, a type of increasing "dripstones" is formed, which under certain circumstances can pass through the separator and thus form an internal short circuit Separators which have a sponge-like structure are therefore particularly susceptible to this dendrite growth since, on the one hand, the Part of excessively large pores, which cause a large local current density, are already present, and on the other hand, the thin sponge structures are easily breakable. Other PET-based separators are disclosed in JP 2005/293891 and CN 2009/69179. In order to improve the properties of a lithium-ion battery and to reduce the pore size of the separator, EP 2 077 594 and US 2003/0190499 disclose separators in which a PET-based nonwoven with an organic polymer such as polyvinylidene fluoride (PVdF ) is coated. US 2006/0019164 describes a PET separator with a ceramic coating. Disadvantages, however, in particular affect the depth filter structure in these separators and, in the case of ceramics, also the brittleness and complicated production.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrochemical energy store which has a separator which overcomes the disadvantages mentioned above.

This object is achieved by an electrochemical energy store having the features of claim 1. Further embodiments are given in the dependent claims.

The present invention thus provides an electrochemical energy store with a separator, which has the following features:

a positively charged electrode;

a negatively charged electrode; and

an electrolyte.

The separator separates the positively charged electrode and the negatively charged electrode from each other and is porous. The separator also has at least one microporous film in which ion channels are formed, which are produced inter alia by means of irradiation of ions.

The ion channels are each at different angles to each other.

The electrochemical energy storage can be a primary battery or act a secondary battery. It may be any type of battery within these two groups, in which case in particular the positively charged electrode and the negatively charged electrode and the electrolyte are then formed from a corresponding material. In the group of primary batteries, for example, a lithium battery would be conceivable. For example, in the case of a secondary battery, the electrochemical energy storage device may include battery types such as a lead acid battery, a lead gel battery, a sodium sulfur battery, a nickel lithium battery, a lithium iron phosphate battery, a lithium titanate battery, or a lithium - Air battery. However, the electrochemical energy store is particularly preferably a lithium-ion battery in which the positively charged electrode has a lithium-containing metal oxide and the negatively charged electrode is suitable for receiving and emitting lithium ions.

The production of the microporous film by means of irradiation with ions is particularly advantageous because it makes it possible to form well-defined ion channels. The ion irradiation thus causes the formation of the ion channels. The microporous film can thus be prepared in addition to the irradiation of ions by further process steps, which are microscopically recognizable in the finished film, in particular by a subsequent chemical etching. By such etching, molecular chains which have been split by ion irradiation can be ablated to fully form pores. Further and alternative further treatment steps are possible. This irradiation of ions in combination with possible further process steps, such as the etching described, thus results in the formation of microscopically detectable ion channels. Unlike separators of the prior art which have the spongy structure of a depth filter, such a separator according to the invention allows passage of ions on a direct, resistance-free path. Such a separator can thus at the same time have a relatively small porosity and nevertheless very good ion permeability. He is therefore relatively stable mechanically. The good ion permeability of the separator significantly improves the electrical properties of the battery, and the mechanical stability of the separator in particular facilitates the production of the battery.

The separator may in particular comprise a single microporous film. Furthermore he can be formed from this alone.

The microporous film is preferably produced at least partially from polyethylene terephthalate (PET) and in particular exclusively from polyethylene terephthalate (PET). The separator thus has a resistance over a very wide temperature range. The melting point of such a PET separator is 220 ° C, and the separator can be operated in a range of -40 ° C to 180 ° C without changing its structure. This allows, for example, to operate the battery even at high power. In addition, PET is well wettable with an electrolyte and has good processing properties.

Preferably, the pores of the microporous film are each formed as substantially cylindrical ion channels. By "substantially", it is meant that the diameter of the ion channels may vary slightly along their length: the cylindrical shape of the ion channels may be tube-like or tubular, with different ion channels also being able to intersect, with a vast majority of the pores however, a clearly defined, tubular ionic channel can be seen which has at least a considerable length which is unbranched and is not cut by another ionic channel Such a pore structure is optimal since the cross-sectional area of the pores is very accurately determinable and the path for the ions through the separator is direct and without resistance.

In particular, the ion channels are each at different angles to each other. This means that the ion channels each extend in a random manner in mutually different spatial directions. Preferably, the ion channels are each not only along one dimension, but along two dimensions, each extending parallel to the film surface, at different angles to each other. The various ion channels are thus advantageously each skewed in space. The average pore diameter of the separator thus has a significantly smaller scattering, in particular with a high pore density. The probability of occurrence of parallel ion channels, which have partially overlapping cross-sectional areas and thereby together form a too wide pore, is considerably reduced. In particular, an embodiment in which the angle between the surface of the separator film and the ion channels is at least 45 ° in each case is advantageous. The length of the ion channels is limited by this. However, at least 50% of the ion channels preferably have an angle to the surface of the separator film of less than 70 °. This ensures that the angles of the ion channels to the surface of the film differ sufficiently from one ion channel to the next.

The ion channels can each have an opening on both sides of the separator, which widens outwards, microscopically recognizable. Preferably, the openings widen conically outwards, whereby a single ion channel can be described as double conical, and as a whole it has a kind of "hourglass shape." The entry of the ions into the ion channel is thereby facilitated, whereby both the properties of the ion channel Charging and unloading be favored.

On the one hand to achieve a good ion permeability with low internal resistance and on the other hand to ensure the mechanical stability of the separator, the separator preferably has a thickness of 12 μιη to 36 μηι on. In particular, a thickness of the separator of 20 μπι to 28 μιη, preferably of about 23 μηι, advantageous.

In order to improve the wettability of the separator with the electrolyte and thus facilitate the passage of ions through the separator, the separator may have a modification of the surface which improves the wettability with liquids. This can be a chemical or a physical modification. In particular, it may also be a coating of the surface with another material, which has improved properties in terms of wettability.

In a preferred embodiment, the porosity of the separator is less than 30%. The mechanical and chemical stability is improved. An embodiment in which the porosity of the separator is less than 20%, in particular even less than 15%, is even more advantageous.

The present invention also provides a separator for use in a to electrochemical energy storage, wherein the separator is configured as described above, in particular it is formed porous. Furthermore, according to the invention, the use of a microporous film as a separator for an electrochemical energy storage claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described below with reference to the drawings, which are given by way of illustration only and are not to be construed as limiting. In the drawings show:

1 is a perspective view of a cut-for illustration purposes, inventive battery according to a first embodiment.

Fig. 2 is a schematic representation of the polymer structure of a separator, such as the battery of Fig. 1, prior to ion irradiation;

Fig. 3 is a schematic representation of the polymer structure of a separator such as the battery of Fig. 1 after ion irradiation;

Fig. 4 is a schematic representation of the polymer structure of a separator such as the battery of Fig. 1 after ion irradiation and during the etching process;

Fig. 5 is a photomicrograph of the surface of a separator, like him

Battery of Figure 1;

6 is a microscopic Schnittaufhahme perpendicular to the surface of a

Separators, as it has the battery of Figure 1;

7 shows a micrograph of the surface of a separator according to the

Prior art;

8 is a microscopic Schnittaufhahme perpendicular to the surface of a

Separators according to the prior art;

Fig. 9 shows an apparatus for producing a separator, such as the battery of

Figure 1 has; such as

10 is an illustration of the ion bombardment of a foil in the device of FIG

FIG. 9. DESCRIPTION OF PREFERRED EMBODIMENTS

1 shows a preferred embodiment of an inventive electrochemical energy storage is shown in a perspective view. This electrochemical energy store described below is a secondary battery in the form of a lithium-ion battery. However, this embodiment represents only one possible example of an inventive electrochemical energy storage. Of course, the inventive separator can also be used in other electrochemical energy storage.

In this embodiment, the battery has a substantially cylindrical housing 10 with a circumferential side wall in which, as the most essential components of the battery, a positively charged electrode 20 and a negatively charged electrode 30 are arranged separated by porous separators 40a and 40b. In addition, an electrolyte is present in the housing 10, which is in chemical contact with the two electrodes 20, 30 and which surrounds the two separators 40a, 40b and thereby wets. The negative electrode 30 in this case has an active in the chemical reaction of the charging or discharging process material containing graphite. In the present embodiment, the positive electrode 20 contains in particular lithium metal oxides. The positive and the negatively charged electrodes 20 and 30 are each formed as a long, band-shaped microporous film 21 and 31, respectively. Likewise, the separators 40a and 40b are each formed as a whole in the present embodiment as a film. The battery has here two similar separators 40a and 40b. To produce the battery, said microporous films in the sequence of positive electrode 20 - separator 40a - negative electrode 30 - separator 40b are superimposed congruent and then wound around a pin 50 around (possibly several times), wherein the positive electrode 20 radially to the innermost to lie comes. The film 21 of the positive electrode 20 and the film 31 of the negative electrode 30 are thus separated from each other even in the wound state at each location by one of the two separators 40a and 40b. The structure of the separators 40a and 40b will be described in detail later. The terminal pin 50 is disposed centrally along the longitudinal axis of the housing 10 and connected to an electrode terminal 22 of the positively charged electrode 20 along a major portion of its length. This electrode terminal 22 is formed along the inner edge of the film 21 of the positive electrode 20 which is in the rolled-up state and extends parallel to the pin 50. It is arranged on the radially inward-facing side of the film 21. In this case, the electrode connection 22 is in particular designed such that it can be connected to the connection pin 50 and thereby produces an electrically conductive connection between the film 21 of the positive electrode 20 and the connection pin 50.

The connecting pin 50 in turn is connected via an electrically conductive connection with a positive pole 70, which is formed in this embodiment by a cover surface, which closes the cylindrical housing 10 to one side sealingly. For sealing a seal 110 is arranged, for example in the form of a sealing ring between the housing 10 and the outer edge of this top surface. The outwardly facing side of the cover surface, which forms the positive pole 70, is particularly suitable for applying a first contact of an electrical load (not shown), which can be configured in a variety of ways. An insulator 61 is attached to the side of the roller formed by the electrodes 20, 30 and the separators 40a, 40b, facing the pole 70. The insulator 61 prevents electrical contact of the negatively charged electrode 30 with the pin 50, the pole 70 or other electrically conductive and between the pole 70 and the negative electrode 30 disposed element. The insulator 61, which is made of an electrically insulating material, surrounds the connecting pin 50 and extends circumferentially from this radially outward to the side wall of the housing 10 back. As a result, it is ensured in the present exemplary embodiment that the pole 70 is electrically connected to the winding exclusively via the connecting pin 50 and that no battery-internal short circuit can occur between the pole 70 and the negative electrode 30.

In order to limit the temperature inside the battery, for example, in the case of an external short circuit upwards, can within the electrical connection between the pin 50 and the pole 70, a PTC thermistor 100 may be provided. The thermistor 100 is a temperature-dependent electrical resistance, which increases its resistance significantly with an increase of the current and thereby limits the current flow and thus the temperature upwards. The battery is thereby protected from an elevated temperature due to excessive current flow, thereby preventing irreversible damage to the battery.

In addition, a safety valve 90 can be formed in the region between the nested electrodes 20, 30 or separators 40a, 40b and the pole 70. This safety valve 90 allows an overpressure arising, for example, during a battery charge to escape to the outside from the interior of the battery.

The film 31 of the negative electrode 30 has in the present embodiment, an electrode terminal 32 which is mounted along the outside in the wound state, parallel to the pin 50 extending edge of the film 31. This electrode terminal 32 is formed on the radially outwardly facing side of the film 31 and has at its end remote from the pole 70 on a tab which extends from the radial outer side of the film 31 beyond the edge radially inwardly. The tab of the electrode terminal 32 is connected to a negative pole 80 which is formed by a terminal surface which closes the housing 10 on the opposite side of the positive pole 70. The outside of this end face is suitable for applying a second contact of an electrical load, not shown here. Between this terminal surface forming the negative pole 80 and the nested films 21, 31, 40a, 40b, there is mounted a second insulator 62 which electrically separates the negative pole 80 from the positive electrode 20. In the region of the tab of the electrode terminal 32, the second insulator 62 is arranged between this tab and the rolled-up films 21, 31, 40a, 40b. The connecting pin 50 does not penetrate the second insulator 62 in contrast to the first insulator 61.

The production of the separators 40a and 40b is described below. A separator 40 suitable for use as a separator 40a or 40b in a battery is porous trained and separated when used in a battery, the positively charged electrode 20 and the negatively charged electrode 30 from each other. He is in the present embodiment, in particular permeable to lithium ions. The starting material of the separator 40 consists of a uniform, homogeneous polyester and may consist of polycarbonate, polyamide or polyimide or, in particular, as in the present case, of polyethylene terephthalate (PET). As illustrated in Fig. 2, this starting material is constituted on a molecular level by a plurality of polymer chains 41, and depending on different areas, a crystalline one (corresponding to the area A in Fig. 2) to an amorphous one (area B in Figs 2) structure can form.

For producing the pores, the film-processed starting material of the separator 40 is exposed to ion irradiation for a certain time. This irradiation takes place essentially from a direction which is perpendicular to the film surface, as indicated in FIG. 2 with an arrow which indicates the direction of irradiation. The rear and front film surfaces are located in Figure 2 on the left or right side. Depending on the intensity and duration of this irradiation, a different pore density can be determined. Local variations in pore density are present, but relatively low. As a result of the irradiation, the polymer chains 41 in the respective regions where the ions pass through the film are destroyed or separated, as shown in FIG. In this case, in the case of an ion passage, in each case a path extending through the film is formed by destroyed polymer chains 41. This path, which is marked by two horizontal, solid lines in FIG. 3, has a diameter d (see FIG. 3) of approximately 5 nm to 7 nm.

The film according to this embodiment is subsequently immersed in a bath containing corrosive substances and pulled therethrough. The corrosive substances used are strongly alkaline solutions, such as potassium and caustic soda. In particular, the polymer chains separated by the ion irradiation are removed by the etching process, whereby a pore extending through the film is formed. As shown in FIG. 4, during the etching process, the etching liquid does not spread perpendicularly to the film surface along the side of the film Ion irradiation formed path, but also in all directions perpendicular thereto. The etching liquid forms an etching front as it propagates in the separator film. However, the velocity V _t at which this etching front propagates in the direction of the path formed by the ion bombardment is substantial, that is to say a multiple, greater than the velocity V _b at which the etching front propagates perpendicular to this path. The reason for this is that the disrupted polymer chains greatly facilitate the propagation of the etching front in the corresponding direction of the path formed by the ion irradiation. After a certain time, the etching front has passed through the film and the pores are formed. However, in order to obtain a broader, and precisely predetermined pore diameter, the film may remain longer in the bath with the etching liquid, whereby the pores widen according to the already mentioned speed V _b .

The manufacturing process can be completed by further steps such as neutralizing, rinsing and drying. For this purpose, the separator film is pulled through successive baths. The process may also be extended to include, for example, a step of modifying the surface in which the microporous film in which pores are already formed is changed so as to improve its wettability with liquids. This modification may be by chemical or physical means. Further manufacturing steps are possible.

The pores 43 of the separator 40, as shown in a microscopic view in FIGS. 5 and 6, have a substantially cylindrical shape and connect the upper side of the separator film with the lower side in a substantially straight path. Between the pores 43, a solid 42 is formed, which is impenetrable to ions. The pores 43 have a well-defined structure, and passage of an ion through the separator 40 is through one of the pores 43 in a straight, direct path that is free of resistances. The pores 43 thus represent actual ion channels, which are clearly visible microscopically in the separator.

As can be clearly seen in FIG. 6, the ion channels or pores 43 are in particular at an angle to each other, that is, at different angles to one another. A such oblique configuration of the ion channels is achieved in that the ions are deliberately deflected in the corresponding irradiation of the Separatorfolie in corresponding, different spatial directions relative to the surface of the film. One possible method for producing such oblique ion channels is described below with reference to FIGS. 9 and 10. Advantageously, however, the angle α (see FIG. 6) of an ion channel to the surface of the film is at least 45 ° in each case in all directions. Preferably, more than 50% of all ion channels have an angle of less than 70 ° to the film surface. The angle of the ion channels 43 to the film surface is determined in each case during the ion irradiation through the direction of the ion passage through the film. By virtue of the fact that the ion channels 43 each run obliquely to one another, it is ensured that the cross-sectional areas of two or more pores do not overlap, in particular in the case of a separator 40 having a high pore density, and a pore having an enlarged cross-sectional area is thereby formed. This would be possible if the ion channels were parallel to each other. Although it is possible that the obliquely running ion channels 43, for example, at the surface, as shown in Figure 5 repeatedly, or intersect on another level of the film, that is at one point have an at least partially overlapping cross-sectional area. Due to the oblique, random arrangement, the ion channels 43 run outside of this common intersection but then independently and in different directions. The decisive for an ion passage cross-sectional area is thus still given by the diameter of the individual ion channel and not determined by the common cross-sectional area at an intersection with another ion channel. By the respective different oblique course of the ion channels 43 so the cross-sectional area of the pores can be precisely defined, and the scattering of this cross-sectional area of pores over the entire separator 40 are kept considerably lower.

The ion channels 43 may be formed such that they are funnel-shaped in the region of their openings, with which they open outward at the two film surfaces, wherein they widen conically towards the outside. The ion channels can have such funnel-shaped openings on both sides of the foil, ie be double-conical and have a kind of "hourglass shape." The entry of an ion into an ion channel 43 is thereby facilitated The shape of an ion channel 43 is formed during the etching process, since the etching chemical takes a certain amount of time to penetrate into and form the ion channels. The etching chemical thus acts longer on the surface of the film or in the input region of the ion channels than in the interior of the ion channels. This causes the formation of outwardly conically widening openings of the ion channels, which is microscopically easily recognizable in particular with relatively thicker Separatorfolien.

The pores 43 advantageously have a diameter of 0.01 μπι to 10 μπι, wherein the separator 40 preferably has a pore density of 10E5 to 10E9 pores per cm ² .

In a concrete, preferred embodiment, the separator 40 is made of polyethylene terephthalate (PET) with its surface modified to have properties that improve wettability with liquids. The thickness of the separator 40 is 23 ± 2 μπι, and the pore diameter 0.2 ± 0.02 μπι. The density of the pores is 320 ± 40 * 10E6 pores per cm. As a characteristic with regard to its ion permeability, such a separator allows per cm an air flow of more than 2.5 liters per minute and per bar. The bursting pressure of the separator is more than 0.95 bar, and the separator has a temperature resistance of over 220 ° C.

The thus formed separator 40 has a porosity of about 12%. This value is very low compared to prior art separators based, for example, on polyolefins or coated PET nonwovens. Nevertheless, the ion permeability in the present separator is significantly improved as compared with the prior art separators, particularly with respect to the ions transmitted per unit time. This can be explained with the specific, straight and tubular pore structure of the separator 40 described, as shown in Figures 5 and 6, compared to the pore structure of conventional separators. Such a pore structure of a separator 40 'of the prior art is shown in Figure 7 in plan view and in Figure 8 in cross section. To produce the pores, the separator material, which here is based on polyolefins, is pulled apart in a stretching process, whereby a fibril-like sponge-like structure is formed. The solid 42 'thereby forms a multiplicity of islands which, as shown in FIG. 7, are connected to one another via a multiplicity of branches. In the interspaces, the pores 43 'are formed. However, these pores 43 'do not have a cylindrical, rectilinear structure but are formed by highly angular and random paths through the ramified structure of the separator solid 42'. A passageway for an ion from one to the other side of the separator 40 'is thus considerably extended, and the pore diameter is not clearly determined and has a correspondingly large scattering. In addition, the poorer wettability of the polyolefin-based material in comparison with PET has a negative effect on the properties of the separator.

Figure 9 shows schematically a possible device for producing obliquely inclined ion channels in a film. The device has an ion source 200 which emits ions. The ions are accelerated within a magnetic field, which is formed in the acceleration sections 220, 221, 222 and 223, along a longitudinal axis in the direction of a target, which is a film 260, in particular a PET film. The magnetic field strengths of the acceleration sections 220 to 223 may each be different and, in particular, continuously increase from the acceleration sections 220 to the acceleration sections 223. However, after passing through the acceleration sections 220 through 223, the energy of the ions must definitely be high enough to penetrate the target or sheet 260. Due to the length of the acceleration sections 220 to 223, it is ensured that the ions strike the target within a certain angular range. Such ion accelerators have long been known in the art.

Between the ion source 200 and the acceleration sections 220 to 223, a so-called wobble 210 is arranged, which serves to fan out the ion beam. The wobble 210 surrounds the ion beam and exposes it to a temporally variable electromagnetic field. A power supply 250 supplies the sweeper with an alternating voltage. As a result of the wobble 210 fanning out the ion beam, the ions do not strike the target in a punctiform manner but are scattered over a certain width or area. The film 260 to be irradiated is rolled up in the winding chamber 240 on one of the winding rolls 241 and, during the ion irradiation, is continuously wound from one winding roll 241 to the other winding roll 241 according to a proven process. In this case, the film 260 runs over a deflecting roller 242 arranged between the two winding rollers 241. The deflecting roller 242 is arranged exactly on the longitudinal axis of the ion beam. The film 260 thereby has a radius corresponding to the radius of the deflection roller 242 in the area where it is bombarded by the ion beam, which is shown in FIG. 10 (arrows represent the fanned-out ion beam). This, in particular, causes the ions to penetrate the film 260 at different angles and thereby form ion channels with different inclinations. The film is thus here deliberately arranged in such a way to the irradiation direction of the ions that it is penetrated by the ions in different spatial directions. Alternatively or additionally, of course, the ions can also be deflected relative to the film surface. In particular, a sweeper can be used for this purpose. In the present exemplary embodiment, the wobbler 210 is actually used to reinforce the effect illustrated in FIG. 10 in that the wobble 210 fans out the ion beam such that the individual ions travel at at slightly different angles relative to the longitudinal axis of the ion beam through the acceleration sections 220-. Move 223.

During the ion bombardment, the film 260 is advantageously guided several times, in particular at least twice, over the deflection roller 242 or is wound from one of the winding rollers 241 onto the other winding roller 241. The film 260 is thus exposed several times to the ion bombardment. Advantageously, the film 260 is exposed to the ion beam in such a way that the resulting ion channels not only extend obliquely with respect to one another along one dimension, but also have different inclinations to each other along two dimensions. The probability that parallel ion channels with partially overlapping cross-sectional areas occur can thereby be further reduced. In order to achieve this, the film 260 can be guided over the deflection roller 242, for example, for a renewed ion bombardment in a different orientation. However, the ions can also be deliberately deflected in mutually perpendicular spatial directions and thus fanned out in two dimensions. Various Possibilities are conceivable.

Of course, the invention is not limited to the above embodiment, and a variety of modifications are possible. In particular, the battery need not be a lithium-ion battery. It does not necessarily have to be a secondary battery. The electrochemical energy store could just as well be designed as a primary battery. The positive or negative electrode in such a case would be correspondingly made of another material known to those skilled in the art. Likewise, then the electrolyte would have a different chemical composition and then it would be correspondingly not involved in lithium ions, but other ions in the ion transport through the separator through. Of course, in such a case the separator would be adapted to the particular type of battery and in particular the properties of the ions to be transmitted. In addition, the battery may for example have a different design than the described cylindrical and be configured for example as a button cell, flat battery or as a block. Furthermore, the battery may have a separator having further surface coatings for improving its physical and / or chemical properties. A variety of other modifications is possible.

REFERENCE LIST Housing 80 Negative Pol

Positively charged electrode 90 safety valve

Electrode foil 100 thermistor

Electrode connector 110 Seal

Negatively charged electrode 200 ion source

Electrode foil 210 Wobbier

Electrode connection 220, 221, 222, 223

, 40 ', 40a, 40b Separator acceleration section

Polymer chain 230 irradiation chamber, 42 'solid 240 winding chamber

, 43 'Pore 241 bobbins

Pin 242 Guide roller

First isolator 250 power supply

Second insulator 260 foil

Positive pole

Claims

1. Electrochemical energy store with a separator (40, 40a, 40b), wherein the electrochemical energy store

a positively charged electrode (20),

a negatively charged electrode (30), and

an electrolyte,

wherein the separator (40, 40a, 40b) separates the positively charged electrode (20) and the negatively charged electrode (30) and is porous, and wherein the separator (40, 40a, 40b) comprises at least one microporous film which ion channels (43) are formed, which are produced inter alia by means of an irradiation of ions,

characterized in that

the ion channels (43) are each at different angles to each other.

2. Electrochemical energy storage according to claim 1, wherein the microporous

Foil is also made by etching.

3. Electrochemical energy storage according to one of claims 1 and 2, wherein the microporous film is at least partially made of polyethylene terephthalate (PET) and in particular exclusively made of polyethylene terephthalate (PET).

4. Electrochemical energy storage according to one of the preceding

Claims, wherein the pores (43) of the microporous film are each formed as substantially cylindrical ion channels.

5. Electrochemical energy store according to one of the preceding claims, wherein the ion channels (43) each have on both sides of the separator (40, 40 a, 40 b) towards an opening which widens outwardly.

6. Electrochemical energy store according to one of the preceding claims, wherein the separator (40, 40 a, 40 b) has a thickness of 12 μπι to 36 μπι.

7. Electrochemical energy store according to one of the preceding claims, wherein the separator (40, 40a, 40b) has a thickness of 20 μπι to 28 μπι.

8. Electrochemical energy store according to one of the preceding claims, wherein the separator (40, 40a, 40b) has a modification of the surface, which improves the wettability with liquids.

9. Electrochemical energy store according to one of the preceding claims, wherein the porosity of the separator (40, 40a, 40b) is less than 30%.

10. The electrochemical energy store according to claim 9, wherein the porosity of the separator (40, 40a, 40b) is less than 20%.

11. The electrochemical energy store according to claim 10, wherein the porosity of the separator (40, 40a, 40b) is less than 15%.

12. Electrochemical energy store, according to one of the preceding claims, wherein the positively charged electrode (20) comprises a lithium-containing metal oxide and the negatively charged electrode (30) is adapted to receive and deliver lithium ions.

13. Separator for use in an electrochemical energy store according to one of claims 1 to 12.

Use of a microporous film as a separator (40, 40a, 40b) for electrochemical energy storage according to one of claims 1 to 12.