Battery cell having a housing and an electrode wound incorporated in
By adjusting the ratio and density of active material to inactive material and tensile stress in the electrode winding body, the problem of high mechanical stress in the battery cell is solved, and the stability and life of the battery are improved.
Patent Information
- Application Number
- CN202380038784.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-05-25
- Filing Date
- 2023-05-02
- Publication Date
- 2024-12-17
AI Technical Summary
There are high mechanical stresses in existing battery cells that affect their stability and life, especially in high-voltage accumulator applications.
The proportion and density distribution of active materials to inactive materials are designed in the electrode winding body, especially in the second region, and the tensile stress and mass load are adjusted to reduce electrode expansion and mechanical stress.
It effectively reduces the mechanical stress in the battery cell and improves the stability and life of the battery, especially in high-voltage accumulator applications.
Smart Images
Figure CN119156726A_ABST
Abstract
Description
[0001] The invention relates to a battery cell having a housing and an electrode winding body inserted into the housing.
[0002] The object of the present invention is to reduce the mechanical stresses in a battery cell.
[0003] This object is achieved by the features of the independent claim. Advantageous embodiments of the invention are defined in the dependent claims.
[0004] The present invention is characterized by a battery cell having a housing and an electrode winding body housed in the housing, the electrode winding body including a first electrode layer, a first separator, a second electrode layer, and a second separator. In addition, the electrode winding body includes a first region and a second region.
[0005] A battery cell is here and hereinafter, for example, a rechargeable battery. Thus, a battery cell is, for example, an individual rechargeable electrical energy storage element.
[0006] The battery cells are in particular battery cells of a high-voltage energy storage system of a vehicle.
[0007] An electrode coil generally refers to a wound layer sequence with at least one electrode layer. For example, such an electrode coil has a cylindrical shape and can also be referred to as a “jelly roll”.
[0008] The electrode layer extends, for example, along a main extension plane. The transverse direction is oriented parallel to the main extension plane, while the vertical direction is perpendicular to the main extension plane. The electrode layer also includes, for example, a main extension direction, which may also be referred to as a longitudinal direction ("longitudinally oriented") hereinafter.
[0009] The electrode layer has a length and a width in the transverse direction. The length of the electrode layer extends parallel to the main extension direction, while the width of the electrode layer extends transversely (in particular perpendicularly) to the main extension direction. The length is, for example, at least five times greater than the width, in particular at least ten times greater. For example, the electrode layer has a width of at least 40 mm and at most 300 mm, in particular 80 mm.
[0010] For use in an electrode coil, for example, a plurality of electrode layers and separator layers are stacked in a vertical direction to form a layer sequence.
[0011] The electrode layers consist of or are formed, for example, from active electrode materials.Here and hereinafter, the term "anode" shall refer to the negative electrode of a battery cell, while the term "cathode" shall refer to the positive electrode of a battery cell.
[0012] In particular, the electrode layer consists of or is formed with an active anode material. In this case, the electrode layer refers to the anode layer of the battery cell.
[0013] The anode layer, for example, has an anode active material, which, for example, includes a material selected from the group consisting of carbonaceous materials, silicon, silicon suboxides, silicon alloys, titanium, titanium oxides, and mixtures thereof. In particular, the anode active material is selected from the group consisting of synthetic graphite, natural graphite, graphene, medium carbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composites, silicon, surface-coated silicon, silicon suboxides, silicon alloys, titanium, titanium oxides, lithium, and mixtures thereof.
[0014] The anode layer is applied to the anode current collector. For example, the anode current collector has a thickness of at least 3 μm to a maximum of 500 μm. Materials that do not cause chemical changes in the battery cell and have conductivity can be used as the anode current collector without restriction. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, surface-treated materials made of copper or stainless steel and carbon, nickel, titanium, silver, aluminum-cadmium alloys and / or similar materials can be used. By forming embossing on one or both main surfaces of the anode current collector, the adhesion of the anode active material can be improved. The anode current collector is in the form of, for example, a film, a sheet, a foil, a mesh, a porous material, a foamed material, a nonwoven material or the like.
[0015] The first electrode layer is particularly referred to as the anode layer.
[0016] Alternatively, the electrode layer may consist of or be formed with an active cathode material. In this case, the electrode layer refers to the cathode layer of the battery cell.
[0017] The cathode layer comprises, for example, a cathode active material. The cathode active material may comprise a plurality (a large number) of particles incorporated into an electrode binder. The cathode active material may comprise a layered oxide, such as lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LCO) or lithium nickel cobalt oxide (LNCO). The layered oxide may in particular be an over-lithiated layered oxide (OLO). Other suitable cathode active materials are compounds having a spinel structure, such as lithium manganese oxide (LMO) or lithium manganese nickel oxide (LMNO), or compounds having an olivine structure, such as lithium iron phosphate (LFP, LiFePO4) or lithium manganese iron phosphate (LMFP).
[0018] The cathode layer is applied to the cathode current collector. For example, the cathode current collector has a thickness of at least 3 μm to a maximum of 500 μm. Materials that do not cause chemical changes in the battery cell and have high electrical conductivity can be used as the cathode current collector without restriction. For example, stainless steel, aluminum, nickel, titanium, encapsulated carbon, surface-treated materials made of aluminum or stainless steel and carbon, nickel, titanium, silver or similar materials can be used. As with the anode current collector, in the cathode current collector, the adhesion of the cathode active material can also be improved by forming embossing on one or both main surfaces of the cathode current collector. The cathode current collector is in the form of, for example, a film, a sheet, a foil, a mesh, a porous material, a foamed material, a nonwoven material or the like.
[0019] The second electrode layer is particularly referred to as a cathode layer.
[0020] The first and / or second separator layer is, for example, made of or formed from an electrically insulating or non-conductive material. The first and / or second separator layer has a material that is permeable to lithium ions but not to electrons. A polymer can be used as the first and / or second separator layer, in particular a polymer selected from the following group: polyester (in particular polyethylene terephthalate), polyolefin (in particular polyethylene and / or polypropylene), polyacrylonitrile, polyvinylidene fluoride, polyethylene hexafluoropropylene, polyetherimide, polyimide, aramid, polyether, polyetherketone, synthetic spider silk (Spinnenseide) or a mixture thereof. The first and / or second separator layer can optionally be additionally coated with a ceramic material and an adhesive, for example based on Al2O3.
[0021] For example, an insulating thin layer with high ion permeability and mechanical strength can be used as the first separator and / or the second separator. The pore diameter of the first separator and / or the second separator is, for example, at least 0.01 μm and at most 10 μm. The thickness of the first separator and / or the second separator is at least 5 μm and at most 300 μm. For the first separator and / or the second separator, for example, olefin-based polymers such as chemical-resistant and hydrophobic polypropylene, sheets or non-woven fabrics made of glass fiber, polyethylene, etc. can be used. When a solid electrolyte, such as a polymer, is used as an electrolyte, the solid electrolyte can also act as the first separator and / or the second separator. For example, a polyethylene film, a polypropylene film, or a multilayer film obtained by combining these films, or a polymer film for a polymer electrolyte or a gel-type polymer electrolyte, such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride hexafluoropropylene copolymer, can be used.
[0022] In an advantageous embodiment of the present invention, the ratio of active material to inactive material of the first electrode layer is greater in the first region than in the second region. In addition, the active material may include expanded active material. Alternatively or additionally, the ratio of expanded active material to remaining active material is greater in the first region than in the second region. Alternatively or additionally, the density of the active material is greater in the first region than in the second region.
[0023] The expanded active material includes, in particular, silicon, silicon suboxides, silicon alloys, titanium, titanium oxide and mixtures thereof.
[0024] Active materials are chemically active substances that are responsible for storing energy in a battery. Inactive materials include, for example, binding agents that act as a binder and hold the active substances together, additives for the active substances, such as conductive additives to increase the electrical conductivity. Inactive materials also include, for example, dispersants or thickeners.
[0025] By means of the above-mentioned measures, the mechanical stress in the second region can be reduced compared to the first region, thereby reducing the mechanical stress in the battery cell.
[0026] In an advantageous embodiment of the invention, the ratio of active material to inactive material in the first region is between 93% and 98%, and the ratio of active material to inactive material in the second region is between 91% and 96%.
[0027] Thus, due to the lower ratio of active material to inactive material in the second region, electrode expansion in the second region can be reduced in an advantageous manner compared to the first region. By reducing electrode expansion, mechanical stresses within the battery cell are advantageously reduced.
[0028] In an advantageous embodiment of the invention, the ratio of expanded active material to remaining active material in the first region is between 5% and 30% and in the second region is between 0% and 10%.
[0029] Thus, due to the lower ratio of expanded active material to remaining active material in the second region, electrode expansion in the second region can be reduced in comparison with the first region in an advantageous manner. By reducing electrode expansion, mechanical stresses within the battery cell are advantageously reduced.
[0030] In an advantageous embodiment of the invention, the density of the active material in the second region is lower than in the first region, preferably at most 10% lower than in the first region.
[0031] Thus, due to the lower density of the active material in the second region, electrode expansion in the second region can be reduced in an advantageous manner compared to the first region. By reducing the electrode expansion, mechanical stresses within the battery cell are advantageously reduced.
[0032] In an advantageous embodiment of the invention, the electrode winding is wound with a stronger tensile stress in the first region than in the second region. The mechanical stresses can be distributed in an advantageous manner within the electrode winding by means of the changed tensile stress.
[0033] In an advantageous embodiment of the present invention, the tensile stress of the electrode winding in the second region is lower than in the first region, preferably at most 20% lower than in the first region. The lower tensile stress of the electrode winding in the second region advantageously reduces the mechanical stress caused by electrode expansion in the second region.
[0034] In an advantageous embodiment of the invention, the first electrode layer has a greater mass loading in the first region than in the second region. Due to the different mass loadings of the first and second regions, mechanical stresses can be distributed within the electrode winding in an advantageous manner.
[0035] In an advantageous embodiment of the present invention, the first electrode layer has a greater mass loading in the first region than in the second region, preferably at most 10% greater than in the first region. The smaller mass loading of the first electrode layer in the second region advantageously reduces mechanical stresses caused by electrode expansion in the second region.
[0036] In an advantageous embodiment of the present invention, the first region has two sub-regions, and the second region is arranged between the two sub-regions of the first region.
[0037] By arranging the second region between the two subregions of the first region, the second region is also located between the two subregions of the first region in a wound form. Therefore, the first region is located in the center of the electrode winding body and in the outer electrode layer in a wound form. Therefore, the second region is located in the inner electrode layer of the electrode winding body in between.
[0038] Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying schematic drawings.
[0039] In the figure:
[0040] Figure 1 The electrode winding is shown together with the housing of the battery cell;
[0041] Figure 2 shows the pressure distribution within the electrode winding;
[0042] Figure 3The assembly of an electrode winding as a layer sequence and its division into individual subregions are shown;
[0043] Figure 4 shows different winding states of the electrode winding;
[0044] Elements having the same structure or function are denoted by the same reference symbols in all the figures.
[0045] Figure 1 The assembly of electrode winding 2 is shown as a layer sequence and its division into individual subregions.
[0046] Therefore, in Figure 1 , a positive electrode layer KAT (also referred to as cathode layer KAT), a separator layer SEP and a negative electrode layer AN (also referred to as anode layer AN) are shown. These layers are arranged one above the other in the order shown. The cathode layer KAT is applied to a cathode current collector KAT_SK. The anode layer AN is applied to an anode current collector AN_SK. The separator layer SEP insulates the cathode layer KAT and the anode layer AN from each other.
[0047] The anode layer AN may also be referred to as a first electrode layer. The cathode layer KAT may also be referred to as a second electrode layer. The separator SEP may also be referred to as a first separator. Additionally, a second separator may be provided outside the cathode layer KAT (not shown), which also insulates the anode layer AN and the cathode layer KAT from each other in a wound state. Figure 1 It is further shown that the layer sequence is divided into a first region B1 and a second region B2. The first region B1 is further divided into two sub-regions B1a and B1b. The second region B2 is arranged between the two sub-regions B1a and B1b.
[0048] The layer sequence is provided with reference points x1, x2 and x3. Figure 2 and 3 These reference points are described in detail in , wherein the reference point x1 is located in the first sub-region B1a, the reference point x2 is located in the second region B2 and the reference point x3 is located in the second sub-region B1b.
[0049] Figure 2 The electrode winding 2 is shown together with the housing 3 of the battery cell 1. Figure 1 The layer sequence in is wound up in the longitudinal direction x about the longitudinal axis A into a cylindrical electrode winding.
[0050] exist Figure 3 2 shows a cross section of an electrode winding 2. In this cross section, the coordinate axes along the x direction are given for orientation. Reference points x1, x2 and x3 indicate Figure 1 The position of the layer sequence in the electrode winding. Figure 3 The characteristic curve of the mechanical stress along the coordinate axis in the x direction is shown in FIG.
[0051] The battery cell 1, in particular in the anode, may contain an expanding active material, such as silicon, silicon suboxide, silicon alloy, titanium, titanium oxide or a mixture thereof or a portion thereof. Mechanical stresses are generated inside the electrode winding 2 due to the expanding active material. Due to the structural form of the battery cell 1, there is space for expansion at the center of the cylindrical battery cell (for example, at the reference point x1) and at the inner edge of the housing 3 of the battery (for example, at the reference point x3), so that the mechanical stress in this area (first area) is small. There is no space for expansion between the electrode layers, for example, at the reference point x2, so that the mechanical stress in this area (second area) increases.
[0052] In order to reduce the mechanical stresses within the battery cell 1 , the expansion of the active material in the second region B2 is reduced. An exemplary measure relates to the anode of the battery cell.
[0053] To reduce the expansion, for example, the ratio of active material to inactive material is reduced in the second region B2 compared to the first region B1 .
[0054] For example, the anode is composed of 96% by weight of active material and 4% by weight of inactive material in the first region B1 , while the anode is composed of 93% by weight of active material and 7% by weight of inactive material in the second region B2 .
[0055] In order to further reduce the expansion of the active material in the second region, for example, the ratio of the active material expanded in the second region B2 to the remaining active material is reduced compared to the first region B1.
[0056] For example, in the first region B1, an anode with 96% by weight of active material consists of a mixture of 30% silicon and 70% carbon. In the second region B2, the ratio of expanded active material (silicon) to the remaining active material (carbon) is reduced by a mixture of 10% silicon and 90% carbon.
[0057] The expanded active material may also be silicon suboxide, silicon alloy, titanium or titanium oxide, or a combination of the above substances.
[0058] In order to further reduce the expansion of the active material in region 2, for example, an active material with a lower density is applied in the second region B2 compared to the first region B1. The density in the second region B2 is, for example, 10% lower than the density in the first region B1.
[0059] In order to further reduce the expansion of the active material in the second region B2, for example, the active material with a smaller mass loading is applied in the second region B2. The mass loading of the active material in the first region B1 is, for example, 10% higher than in the second region B2.
[0060] Figure 4 1 and 2 show different winding states of the electrode winding body 2. In the first winding state Z1, Figure 1 In the second winding state Z2 , the second region B2 of the layer sequence is wound into an electrode winding, and in the third winding state Z3 , the subregion B1b of the layer sequence is wound into an electrode winding.
[0061] In order to reduce the mechanical stress in the second region B2 of the electrode winding, the electrode winding is wound in the second region B2 with a smaller tensile stress than in the first region B1 (ie, in the two subregions B1 a and B1 b ).
[0062] For example, the tensile stress in the second region B2 is 20% smaller than that in the first region B1. Reference numerals list
[0063] 1 battery unit
[0064] 2-electrode winding
[0065] 3 Shell
[0066] A vertical axis
[0067] AN Anode
[0068] AN_SK anode current collector
[0069] B1 Area 1
[0070] B1a Sub-region of the first region
[0071] B1b Sub-region of the second region
[0072] B2 Second Area
[0073] KAT cathode
[0074] KAT_SK cathode current collector
[0075] SEP Isolator
[0076] x1, x2, x3 reference points
[0077] x, y, z reference coordinate system
[0078] Z1, Z2, Z3 winding status
Claims
1. A battery cell (1), comprising a housing (3) and an electrode winding (2) inserted into the housing (3), - the electrode winding (2) comprises a first electrode layer, a first isolation layer, a second electrode layer and a second isolation layer, - the electrode winding body (2) comprises a first region (B1) and a second region (B2), in, - the ratio of active material to inactive material of the first electrode layer is greater in the first region (B1) than in the second region (B2), and / or - the active material includes expanded active material and the ratio of the expanded active material to the remaining active material is greater in the first region (B1) than in the second region (B2), and / or - The density of the active material is greater in the first region (B1) than in the second region (B2).
2. The battery cell (1) according to claim 1, wherein: The ratio of active material to inactive material in the first region ( B1 ) is between 93% and 98%, while the ratio of active material to inactive material in the second region ( B2 ) is between 91% and 96%.
3. The battery cell (1) according to claim 1 or 2, wherein: The ratio of the expanded active material to the remaining active material is between 5% and 30% in the first region ( B1 ), and between 0% and 10% in the second region ( B2 ).
4. The battery cell (1) according to one of the preceding claims, wherein: The density of the active material is smaller in the second region ( B2 ) than in the first region ( B1 ).
5. The battery cell (1) according to one of the preceding claims, wherein: The first electrode layer has a greater mass loading in the first region ( B1 ) than in the second region ( B2 ).
6. The battery cell (1) according to claim 5, wherein: The mass loading of the first electrode layer in the first region ( B1 ) is 0 to 10% higher than the mass loading of the first electrode layer in the second region ( B2 ).
7. The battery cell (1) according to one of the preceding claims, wherein: The tensile stress of the electrode wound body (2) is smaller in the second region (B2) than in the first region (B1).
8. The battery cell (1) according to claim 7, wherein: The electrode winding (2) is wound with a stronger tensile stress in the first region (B1) than in the second region (B2).
9. The battery cell (1) according to one of the preceding claims, wherein: The first region (B1) has two sub-regions (B1a, B1b) and the second region (B2) is arranged between the two sub-regions (B1a, B1b).