DE102021212431B3 - Separator layer and electrode arrangement for a battery cell - Google Patents

Abstract

Separator layer (1) for a battery cell (2), the separator layer (1) comprising a first side surface (3), a second side surface (4) arranged opposite and a substrate (5) in between for the passage of ions, the first side surface ( 3) is formed by a first layer (6) and the second side surface (4) by a second layer (7), each having an adhesive effect, so that the electrodes (8, 9) of a battery cell (2) through the separator layer ( 1) are adhesively bondable to each other; the first layer (6) and the second layer (7) being different from each other. An electrode arrangement (15) for a battery cell (2) is also specified.

Description

The invention relates to a separator layer and an electrode arrangement for a battery cell.

Batteries, in particular lithium-ion batteries, are increasingly being used to drive motor vehicles. In particular, z. B. a motor vehicle has an electric machine for driving the motor vehicle, wherein the electric machine can be driven by the electrical energy stored in the battery cell. Batteries are typically assembled from battery cells, with each battery cell having a stack of anode, cathode and separator sheets. At least part of the anode and cathode layers are designed as current collectors for diverting the current provided by the battery cell to a consumer arranged outside the battery cell. Battery cells with liquid or solid electrolytes (solid-state battery) are known.

The present separator layer is used in particular in a battery cell with a liquid electrolyte or in a solid-state battery cell, which therefore only comprises solid components (all-solid-state battery cell or solid-state battery cell, semi-solid electrolytes included, e.g. polymers, i.e. also a solid electrolytes) used.

A battery cell comprises in particular a housing, which is designed in particular to be gas-tight, and arranged therein at least one stack of electrode foils or layers arranged one on top of the other. The housing can be designed as a dimensionally stable housing (e.g. prismatic cell or round cell) or at least partially made of an elastically deformable film material (pouch cell). A combination of both housing types is also possible.

In the manufacture of an electrode of a battery cell, what is known as a carrier material, in particular a strip-shaped carrier material, e.g. B. a carrier film, at least partially coated on one side or both sides with an active material. The current conductors (conductor lugs) formed on the electrode are formed in particular by uncoated areas of the carrier material. The carrier material includes z. B. copper, a copper alloy, aluminum or an aluminum alloy.

Separator layers are used as ion conductors between different electrodes, ie between anodes and cathodes. It is known that separator layers can have coatings with an adhesive effect, ie so-called adhesion coatings, on both side surfaces oriented towards the different electrodes. The adhesive effect enables the individual layers, ie the electrode layers and the separator layers, to be fixed to one another.

Adhesion coatings on separator layers are used to either improve/accelerate the production process and/or improve the properties of lithium-ion cells (e.g. safety, durability, etc.). Due to the different nature of the anode and the cathode, adhesion of the separator to the respective electrodes may differ, so that e.g. B. the adhesion to an electrode is too strong and the internal resistance may increase, or the adhesion is too weak and a gap may form, which can have a negative effect on the life of the cell.

1. a) Anpassung der Beschichtungsart der Adhäsionsbeschichtung (Gravure Coating, d. h. eher vollflächig gegenüber Spray coating, d. h. eher inselartig);
2. b) Auswahl des, eine adhäsive Wirkung aufweisenden Materials, z. B. PMMA (Polymethylmethacrylat), PVdF (Polyvinylidenfluorid) oder PVdF-HFP-Co-Polymer (PVdF-Hexafluoropropylen-Co-Polymer); inklusive Anpassung der Molmasse;
3. c) Anpassung der Laminationsparameter (z. B. Druck, Temperatur, Zeit) der Laminationsvorrichtung, also der Parameter, mit denen die Haftung der Adhäsionsbeschichtung prozessual beeinflusst wird; und
4. d) Dicke der Adhäsionsbeschichtung.

It is known to apply the same adhesion coating to both side surfaces of the separator layer. Attempts are made to find a kind of balance between the adhesion and the two electrodes. This can be done using the following exemplary measures:

1. a) Adaptation of the type of coating of the adhesion coating (gravure coating, ie rather full-surface compared to spray coating, ie rather island-like);
2. b) Selection of the material having an adhesive effect, e.g. B. PMMA (polymethyl methacrylate), PVdF (polyvinylidene fluoride) or PVdF-HFP copolymer (PVdF-hexafluoropropylene copolymer); including adjustment of the molar mass;
3. c) adjustment of the lamination parameters (e.g. pressure, temperature, time) of the laminating device, ie the parameters with which the adhesion of the adhesion coating is influenced by the process; and
4. d) Thickness of the adhesion coating.

It is also known to design a (side surface of a) separator layer differently towards the cathode than towards the anode. For example, ceramic layers can be provided, which are arranged towards the cathode in lithium-ion battery cells. However, the adhesive coatings are always the same. This means that a compromise between adhesion to the anode and adhesion to the cathode has to be made.

From the EP 3 024 063 A1 a separator for a lithium-ion battery is known. The separator comprises a porous substrate coated on both sides with an organic and/or inorganic layer. The organic layer includes organic particles that have a lower melting point than the substrate, so that if the battery cell is heated to an unacceptable level, the organic layer melts and penetrates the pores of the substrate. This can possibly prevent a thermal runaway of the battery cell. The inorganic layer is intended to prevent thermally induced shrinkage of the separator, so that a short circuit caused by contacting the electrodes is avoided. The binder material used in each case is the same for all layers.

The U.S. 2015/0050544 A1 is directed to a rechargeable lithium battery cell.

The EP 3 696 880 A1 discloses a separator material.

The object of the present invention is to at least partially solve the problems cited with reference to the prior art. In particular, a separator layer and electrode arrangement are to be proposed in which a layer provided between the separator layer and the electrode is designed with an adhesive effect in a targeted manner with regard to the respectively adjacent electrode.

A separator layer having the features according to patent claim 1 and an electrode arrangement having the features according to patent claim 8 contribute to the solution of these tasks. Advantageous developments are the subject matter of the dependent patent claims. The features listed individually in the patent claims can be combined with one another in a technologically meaningful manner and can be supplemented by explanatory facts from the description and/or details from the figures, with further embodiment variants of the invention being shown.

A separator layer for a battery cell is proposed, wherein the separator layer comprises a first side face and a second side face arranged opposite, and a substrate between them for the passage of ions. The first side surface is formed by a first layer and the second side surface by a second layer, each of these layers having an adhesive effect so that the electrodes of a battery cell can be adhesively connected to one another through the separator layer. The first layer and the second layer are designed differently from one another, in particular (exclusively) with regard to their adhesive properties.

The term layer used here serves in particular to describe the spatial shape. The respective layer thus forms the respective side surface. The layer can be designed or applied in the manner of a coating. In particular, the layer has a substantially constant thickness. The layer can e.g. B. be applied by spray coating (ie thermal spraying).

The passage of ions is ensured in particular by the separator layer, i. H. through the substrate and the described layers.

The adhesive effect serves in particular to connect the electrodes to one another through the separator layer, so that they are fixed in relation to one another in terms of their position.

• • Art eines die adhäsive Wirkung aufweisenden Materials (z. B. PVdF, Acrylat oder PVdF-HFP);
• • Mischungsverhältnis von unterschiedlichen Materialien;
• • Molmasse;
• • Kristallitgröße (also die Größe der kristallinen Teile eines Werkstoffes bzw. Materials oder eines polykristallinen Gefüges);
• • Anteil von PVdF (Polyvinylidenfluorid) oder von HFP (Hexafluoropropylen bzw. Fluorpolymer) in einem PVdF-HFP Co-Polymer der Adhäsionsbeschichtung;
• • Morphologie und Haftungseigenschaft, z. B. eingestellt durch eine unterschiedliche Verarbeitung bzw. Prozessierung des Materials, z. B. weil das Material wasser- oder lösungsmittelbasiert ist;
• • Dicke, in einer Normalenrichtung zur Seitenfläche;
• • Anteil einer Bedeckung der jeweiligen Seitenfläche, also z. B. vollflächige Bedeckung der jeweiligen Seitenfläche oder nur inselartig oder punktuell.

In particular, the first layer and the second layer differ from one another at least with regard to one of the following properties:

• • Type of material exhibiting the adhesive effect (e.g. PVdF, acrylate or PVdF-HFP);
• • mixing ratio of different materials;
• • Molar mass;
• • Crystallite size (ie the size of the crystalline parts of a material or a polycrystalline structure);
• • Percentage of PVdF (polyvinylidene fluoride) or HFP (hexafluoropropylene or fluoropolymer) in a PVdF-HFP copolymer of the adhesion coating;
• • Morphology and adhesion properties, e.g. B. set by a different processing or processing of the material, z. B. because the material is water or solvent based;
• • Thickness, in a direction normal to the face;
• • Percentage of coverage of the respective side surface, ie z. B. full-surface coverage of the respective side surface or only isolated or selectively.

• • PVdF;
• • Acrylat;
• • PVdF-HFP.

In particular, the material that has the adhesive effect includes at least one of the following materials:

• • PVDF;
• • acrylate;
• • PVdF HFP.

In particular, at least the first layer or the second layer, preferably both layers, has a thickness of 0.05 to 5 μm [microns], in particular 0.1 to 3 μm, in a direction normal to the side surface.

In particular, the separator layer has a ceramic layer between the substrate and at least the first layer or the second layer. In particular, the ceramic layer is made of Al ₂ O ₃ or boehmite or a mixture thereof or has at least these components. The ceramic layer can (additionally) have SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaSO ₄ , CaCO ₃ or BN.

In particular, at least the ceramic layer has a thickness of 0.05 to 7 μm, preferably 0.1 to 5 μm, in a direction normal to the side surface.

According to the invention, the separator layer has an aramid layer between the substrate and the first layer or the second layer. In particular, the aramid layer is arranged between the substrate and the cathode, or between the substrate and the first layer in the direction towards the cathode. In particular, the separator layer then has no further ceramic layers.

In particular, at least the first layer or the second layer, preferably both layers, has ceramic particles. In particular, z. For example, only the first layer has ceramic particles if only a ceramic layer is arranged between the substrate and the second layer, and vice versa.

In particular, the ceramic particles in the first and/or second layer are designed differently than the ceramic particles in the ceramic layer, e.g. B. with regard to the material, the size of the particles, the concentration of the particles in the respective layer, the particle morphology (i.e. the structure and/or the shape of the particles), the hardness, the density or the BET surface.

In particular, asymmetrical, ie different, adhesion coatings on the separator layer are proposed. Specifically, this means in particular that the adhesion layer (first layer) on one side surface of the separator layer can differ from the adhesion layer (second layer) on the other side surface. As a result of the modification of the respective layer, ie the first layer and/or the second layer, the different character of the anode and the cathode can be taken into account.

A preferred configuration includes, for example, that the substrate of the separator layer is based on one or more polyolefin(s) and has a monolayer or multilayer structure. In particular, the substrate is additionally coated on one side with a ceramic or a ceramic layer, e.g. B. Al ₂ O ₃ or boehmite or a mixture thereof coated. The ceramic or ceramic layer can (additionally) have SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaSO ₄ , CaCO ₃ or BN

If the separator layer has only one (single) layer with ceramic particles or only one (single) ceramic layer, the costs are lower because of only one ceramic coating. In addition, the separator layer is thinner with the same substrate thickness, so that the volumetric energy density of the battery cell is increased. Furthermore, the separator sheet is lighter, so that the gravimetric energy density is increased. Furthermore, the entry of water into the battery cell through the separator is reduced due to the lower number of ceramic particles.

If there are no ceramic particles in the first layer and/or second layer, costs can be saved and a lighter battery cell can be provided, since fewer ceramic particles are used overall.

In particular, the ceramic layer has a thickness of 0.1 to 5 μm [microns].

In particular, an adhesion coating or first or second layer is applied to the ceramic layer, which in particular has a thickness of 0.1 to 3 μm [micrometers].

In a lithium-ion battery cell, the ceramic layer is preferably arranged aligned in the direction of the cathode. The adhesion coating or first or second layer consists on one side of the separator layer of a non-fluorinated polymer, such as. B. acrylate, preferably PMMA. The adhesion coating or first or second layer consists of a fluorinated polymer, e.g. B. from PVdF or PVdF-HFP or a mixture thereof.

In particular, the PVdF-HFP layer is either thicker than the acrylate layer or the PVdF-HFP layer has a larger surface area coverage than the acrylate layer (or both).

In a lithium-ion battery cell, the acrylate layer of the separator is preferably arranged on the side surface of the separator layer pointing towards the anode.

In particular, acrylate on the side surface of the separator layer oriented toward the anode is preferred to fluorine-based adhesive materials, since PVdF can be decomposed at the low potentials of the anode. In addition, adhesive layers based on acrylate be processed thinner, which is advantageous for the thickness of the separator layer and thus the volumetric and gravimetric energy density of the battery cell. In particular, fluorinated polymers are used on the side surface oriented towards the cathode as materials with an adhesive effect because they have high oxidative stability.

An electrode arrangement for a battery cell is also proposed, at least comprising a cathode, an anode and the described separator layer arranged between them.

In particular, in the electrode arrangement, the separator layer comprises a first side surface and a second side surface arranged opposite, and a substrate between them for the passage of ions. The first side surface is formed by a first layer and the second side surface by a second layer, each of these layers having an adhesive effect, so that the electrodes of a battery cell are adhesively connected to one another by the separator layer. The first layer and the second layer are designed differently from one another, in particular (exclusively) with regard to their adhesive properties. The first layer and the second layer are arranged in particular on the separator layer and are adhesively connected to the electrodes by an activation process (e.g. roller presses in combination with a temperature input or heating press) after the individual electrode layers have been applied to the separator layers. Alternatively, the first layers and the second layers can be arranged at least partially on the electrodes, so that the substrate or the further layers of the separator layers are only adhesively connected to the separator layers via the first or second layer after the application of the individual electrode layers and separator layers .

In particular, the first layer is arranged towards the cathode and the second layer towards the anode. In particular, the substrate has at least one polyolefin or a plurality of polyolefins. The substrate is designed in particular as a monolayer (that is to say with a homogeneous distribution of components) or as a multilayer (that is to say consisting of a plurality of differently designed layers).

In particular, the separator layer has a ceramic layer between the substrate and the first layer, the first layer containing at least one fluorinated polymer (e.g. PVdF or PVdF-HFP or a mixture thereof) and the second layer containing exclusively non-fluorinated polymers (e.g B. acrylate and / or PMMA).

The separator layer or electrode arrangement is intended in particular for use in a lithium-ion battery cell.

In particular, the electrodes comprise a carrier material, e.g. B. a copper or aluminum foil. The carrier material used consists in particular of 3 to 15 μm thick copper for the anode and 3 to 15 μm [microns] thick aluminum for the cathode. The carrier material is at least partially coated with an active material on at least one of the largest side surfaces of the electrode, possibly also on the largest side surfaces lying opposite one another.

A battery cell is also proposed, at least comprising a battery cell housing and at least the described electrode arrangement arranged therein.

The battery cell is in particular a pouch cell (with a deformable battery cell housing consisting of a pouch film) or a prismatic cell (with a dimensionally stable battery cell housing). A pouch film is a well-known deformable housing part that is used as a battery cell housing for so-called pouch cells. It is a composite material, e.g. B. comprising at least one plastic and aluminum.

The battery cell is in particular a lithium-ion battery cell. However, the battery cell can also be a sodium battery cell or another battery cell.

A battery cell is an electricity storage device that B. is used in a motor vehicle for storing electrical energy. In particular, z. B. a motor vehicle has an electric machine for driving the motor vehicle (a traction drive), wherein the electric machine can be driven by the electrical energy stored in the battery cell.

A motor vehicle is also proposed, at least comprising a traction drive and a battery with at least one of the battery cells described, wherein the traction drive can be supplied with energy by the at least one battery cell.

The explanations regarding the separator layer can be transferred in particular to the electrode arrangement, the battery cell and/or the motor vehicle and vice versa.

The use of indefinite articles ('a', 'an', 'an' and 'an') particularly in the claims and those reflecting them Description, is to be understood as such and not as a numeral. Correspondingly introduced terms or components are to be understood in such a way that they are present at least once and in particular can also be present several times.

As a precaution, it should be noted that the numerals used here (“first”, “second”, ...) primarily (only) serve to distinguish between several similar objects, sizes or processes, i.e. in particular no dependency and/or sequence of these objects, sizes or make processes mandatory for each other. Should a dependency and/or order be necessary, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described embodiment. If a component can occur several times (“at least one”), the description of one of these components can apply equally to all or part of the majority of these components, but this is not mandatory.

• 1: eine erste Ausführungsvariante einer Separatorlage, in einer Seitenansicht im Schnitt;
• 2: eine zweite Ausführungsvariante einer Separatorlage, in einer Seitenansicht im Schnitt;
• 3: eine Elektrodenanordnung einer Batteriezelle mit der Separatorlage nach 1, in einer Seitenansicht im Schnitt;
• 4: eine dritte Ausführungsvariante einer Separatorlage, in einer Seitenansicht im Schnitt; und
• 5: eine vierte Ausführungsvariante einer Separatorlage, in einer Seitenansicht im Schnitt.

The invention and the technical environment are explained in more detail below with reference to the attached figures. It should be pointed out that the invention should not be limited by the exemplary embodiments given. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description. In particular, it should be pointed out that the figures and in particular the proportions shown are only schematic. Show it:

• 1 : a first embodiment variant of a separator layer, in a side view in section;
• 2 : a second embodiment variant of a separator layer, in a side view in section;
• 3 : according to an electrode arrangement of a battery cell with the separator layer 1 , in a side view in section;
• 4 : a third embodiment variant of a separator layer, in a side view in section; and
• 5 : a fourth embodiment variant of a separator layer, in a side view in section.

1 shows a first embodiment variant of a separator layer 1, in a side view in section. The separator layer 1 comprises a first side surface 3 and a second side surface 4 arranged opposite, and a substrate 5 in between for the passage of ions. The first side surface 3 is formed by a first layer 6 and the second side surface 4 by a second layer 7, each of these layers 6, 7 having an adhesive effect, so that the electrodes 8, 9 of a battery cell 2 (see 3 ) can be adhesively connected to one another by the separator layer 1 . The first layer 6 and the second layer 7 are designed differently from one another.

The first embodiment includes that the substrate 5 is additionally coated on one side with a ceramic or a ceramic layer 12, e.g. B. Al ₂ O ₃ or boehmite or a mixture thereof coated. The ceramic layer 12 can (additionally) have SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaSO ₄ , CaCO ₃ or BN. The ceramic layer 12 has a thickness 11 in the normal direction 10 to the side surface 3, 4.

An adhesion coating or the first layer 6 is applied to the ceramic layer 12 and in turn has a thickness 11 . The ceramic layer 12 is aligned in the direction of the cathode 8 . Alternatively, the ceramic layer 12 arranged between the substrate 5 and the first layer 6 is designed as an aramid layer 13 .

The adhesion coating or second layer 7 consists on the second side surface 4 of the separator layer 1 from a non-fluorinated polymer, such as. B. acrylate, preferably PMMA. The adhesion coating or first layer 6 consists of a fluorinated polymer, e.g. B. from PVdF or PVdF-HFP or a mixture thereof.

In a lithium-ion battery cell, the acrylate layer of the separator layer 1, that is to say the second layer 7, is arranged on the second side surface 4 of the separator layer 1 pointing towards the anode 9.

2 shows a second embodiment variant of a separator layer 1, in a side view in section. To the remarks 1 is referenced.

In contrast to the first embodiment variant, the substrate 5 is coated with a ceramic layer 12 on both sides.

3 shows an electrode arrangement 15 of a battery cell 2 with the separator layer 1 1 , in a side view in section. To the remarks 1 and 2 is referred to.

The electrode arrangement 15 comprises a cathode 8 (not shown here), an anode 9 and, arranged between them, the separator layer 5 according to the first embodiment variant.

The anode 9 comprises a carrier material 17. The carrier material 17 is on a largest side surface of the anode 9 is partially coated with an active material 16. The uncoated part of the carrier material 17 forms the conductor 18. The active material 16 of the anode 9 is coated with a ceramic layer 12. The second layer 7 formed on the second side face 4 is connected to the ceramic layer 12 of the anode 9 .

4 shows a third embodiment variant of a separator layer 1, in a side view in section. To the remarks 1 and 2 is referenced.

In contrast to the first variant, the second layer 7 has ceramic particles 14 .

5 shows a fourth embodiment variant of a separator layer 1, in a side view in section. To the remarks 4 is referenced.

In contrast to the third embodiment variant, the first layer 6 also has ceramic particles 14, so that no ceramic layer 12 is provided.

Reference List

1

separator layer

2

battery cell

3

first face

4

second side face

5

substrate

6

first layer

7

second layer

8th

cathode (electrode)

9

anode (electrode)

10

normal direction

11

thickness

12

ceramic layer

13

Aramid layer

14

(ceramic) particles

15

electrode arrangement

16

active material

17

carrier material

18

arrester

Claims (9)

Separator layer (1) for a battery cell (2), the separator layer (1) comprising a first side surface (3), a second side surface (4) arranged opposite and a substrate (5) in between for the passage of ions, the first side surface ( 3) is formed by a first layer (6) and the second side surface (4) by a second layer (7), each having an adhesive effect, so that the electrodes (8, 9) of a battery cell (2) through the separator layer ( 1) are adhesively bondable to each other; the first layer (6) and the second layer (7) being different from each other; wherein the separator layer (1) has an aramid layer (13) between the substrate (5) and the first layer (6) or the second layer (7). Separator layer (1) after Claim 1 , wherein the first layer (6) and the second layer (7) differ from one another at least with regard to one of the following properties: • type of material having the adhesive effect; • mixing ratio of different materials; • Molar mass; • crystallite size; • Percentage of PVdF (polyvinylidene fluoride) or HFP (fluoropolymer) in a PVdF-HFP co-polymer of the adhesion coating; • morphology and adhesion property; • Thickness, in a direction normal to the face; • Percentage of coverage of the respective side surface. Separator layer (1) according to one of the preceding claims, wherein the material comprising the adhesive effect comprises at least one of the following materials: • PVDF; • acrylate; • PVdF HFP. Separator layer (1) according to one of the preceding claims, wherein at least the first layer (6) or the second layer (7) has a thickness (11) of 0.05 to 5 µm in a direction normal (10) to the side surface (3, 4). having. Separator layer (1) according to one of the preceding claims, wherein the separator layer (1) has a ceramic layer (12) between the substrate (5) and at least the first layer (6) or the second layer (7). Separator layer (1) after Claim 5 , wherein at least the ceramic layer (12) has a thickness (11) of 0.05 to 7 µm in a normal direction (10) to the side surface (3, 4). Separator layer (1) according to any one of the preceding claims, wherein at least the first Layer (6) or the second layer (7) has ceramic particles (14). Electrode arrangement (15) for a battery cell (2), at least comprising a cathode (8) and an anode (9) as electrodes (8, 9) and arranged between them a separator layer (1) according to one of the preceding claims. Electrode arrangement (15) after patent claim 8 , wherein the first layer (6) towards the cathode (8) and the second layer (7) towards the anode (9) are arranged; wherein the substrate (5) has at least one polyolefin and the separator layer (1) has a ceramic layer (12) between the substrate (5) and the first layer (6); wherein the first layer (6) comprises at least one fluorinated polymer and the second layer (7) exclusively comprises non-fluorinated polymers.

Images