ELECTRODE AND SECONDARY BATTERY CELL WITH SUCH AN ELECTRODE

Description

[0001] The invention relates to an electrode for a secondary battery cell, wherein the electrode has an electrode base body with a collector section and a contact section. Furthermore, the invention relates to a secondary battery cell having such an electrode and an electrically powered motor vehicle whose traction battery has such a secondary battery cell.

[0002] An electrically powered motor vehicle typically has a traction battery (high-voltage battery, HV battery) that supplies energy to an electric motor to drive the motor vehicle. An electrically powered motor vehicle is understood to mean, in particular, an electric vehicle that stores the energy required for propulsion solely in the traction battery (BEV, battery electric vehicle), an electric vehicle with a range extender (REEV, range extended electric vehicle), a hybrid vehicle (HEV, hybrid electric vehicle), a plug-in hybrid vehicle (PHEV, plug-in hybrid electric vehicle), and / or a fuel cell vehicle (FCEV, fuel cell electric vehicle), which temporarily stores the electrical energy generated by a fuel cell in the traction battery.

[0003] Such a traction battery comprises a number of secondary battery cells, referred to as battery cells for short, which are combined, for example, in battery modules (cell modules). The battery cells and, if applicable, the battery modules are connected in series and / or parallel to one another, so that the traction battery can provide a sufficiently high current and a sufficiently high voltage for an electric motor intended to drive the motor vehicle. Typically, the traction battery is designed as a lithium-ion battery, and its secondary battery cells are designed as lithium-ion battery cells.

[0004] Each of the battery cells comprises at least one anode and at least one cathode. These electrodes are each formed by a carrier foil, which is typically a metal foil, with the carrier foil being coated with an active material in a so-called collector section. Furthermore, the carrier foil comprises an uncoated contact section, referred to as a conductor tab, by means of which the electrode can be electrically connected to a cell conductor (tab).

[0005] To maximize user convenience, it is desirable that the charging process of the traction battery or its battery cells be completed as quickly as possible. During charging, the current flows through the discharge tabs into the collector section. The maximum achievable charging speed (charging rate) of the charging process must be limited due to heat generation and / or the ohmic resistance of the battery cells, particularly the discharge tab and the collector section, to avoid damage to the traction battery and its battery cells.

[0006] US 2011 / 177385 A1 discloses a current collector with a core region. The core region contains at least one electrically conductive third material. The current collector also has a first surface region comprising at least one first material. The current collector also has a second surface region comprising at least one second material. The electrical conductivity of the first surface region is lower than that of the second surface region.

[0007] US 2019 / 288352 A1 describes a battery comprising a housing defining an electrochemical zone. The battery further comprises at least one electrode comprising a conductive substrate, the substrate comprising a first region in the electrochemical zone and a second region protruding from the electrochemical zone.

[0008] The invention is based on the object of providing a particularly suitable electrode for a secondary battery cell, for example, for a lithium-ion battery cell. In particular, this electrode should enable the fastest possible charging process. Furthermore, such a secondary battery cell and an electrically powered motor vehicle should be provided, the traction battery of which comprises at least one such secondary battery cell.

[0009] With regard to the electrode, the object is achieved according to the invention by the features of claim 1. With regard to the secondary battery cell, the object is achieved according to the invention by the features of claim 9, and with regard to the electrically powered motor vehicle by the features of claim 10. Advantageous embodiments and further developments are the subject of the subclaims. The statements made in connection with the electrode also apply mutatis mutandis to the secondary battery cell and the electrically powered motor vehicle, and vice versa.

[0010] For this purpose, the electrode has an electrode base body, which in turn has a collector section and a contact section. The collector section serves as a current collector. The contact section is provided and configured to make electrical contact with a cell conductor, also referred to as a tab, of a battery cell having the electrode, wherein electrical current can be conducted to or from the electrode using the cell conductor. In some battery cell designs, for example in a cylindrical or prismatic battery cell, it is provided that the contact section is electrically contacted with a housing part of the battery cell having the electrode. In this case, the contact section is provided and configured to make electrical contact with the housing part.

[0011] The electrode base body is preferably foil-like, and in particular sheet- or strip-like. For example, the electrode base body is formed from one or more foils. In this case, the electrode base body is also referred to as carrier foil(s). Alternatively or additionally, the contact section and / or the collector section are each formed from a preferably woven or spun mesh, from a porous structure. Additionally or alternatively, the contact section and / or the collector section are provided with recesses or, for example, punched holes.

[0012] The collector section is either formed as a single piece (monolithic), i.e., connected to the contact section, or alternatively, the collector section and the contact section are separate components of the electrode base body, which are joined together and expediently electrically connected. The contact section is expediently arranged at the edge of the collector section and / or protrudes laterally beyond the collector section in an area spanned by the collector section.

[0013] The collector section and the contact section have different electrical conductivities and / or different thermal conductivities. In other words, the thermal conductivity of the collector section is different from the thermal conductivity of the contact section, and / or the electrical conductivity of the collector section is different from the thermal conductivity of the contact section. In particular, the magnitude of the electrical conductivity and / or the magnitude of the thermal conductivity of the contact section is unequal to the magnitude of the electrical conductivity or thermal conductivity of the collector section.

[0014] Particularly compared to electrodes whose electrode base body is formed from a single, coherent foil, the electrical and / or thermal conductivity of the contact section and the collector section can be selected and expediently selected and designed in a particularly advantageous manner using the electrode according to the invention according to different requirements for the electrical and / or thermal conductivities of these sections. Thus, locally different requirements can be better met. For example, the electrical and thermal conductivity of the contact section is greater than the electrical and thermal conductivity of the collector section, so that heat dissipation via the contact sections is improved and / or a higher charging or discharging current can be realized.

[0015] The electrode is suitably intended for a secondary battery cell, for example for a lithium-ion battery cell.

[0016] To allow for different configurations of the collector section and the contact section with respect to their electrical and / or thermal conductivity, the collector section and the contact section have different thicknesses. In other words, the spatial extent of the contact section perpendicular to a plane spanned by the electrode base body differs, i.e., is larger or smaller, than the spatial extent of the collector section in this direction. The electrode base body is formed as a single metal foil, with the contact section being rolled under lower pressure than the collector section during its production.

[0017] Alternatively, according to an expedient embodiment, the collector section and the contact section are formed from different materials for the different configurations of the collector section and the contact section with regard to their electrical and / or thermal conductivity. In particular, the contact section is formed from a first material and the collector section from a second material, wherein the first material and the second material are different, and wherein the electrical and / or thermal conductivity of the first material is different from the electrical and / or thermal conductivity of the second material.

[0018] According to a practical embodiment, the collector section is formed from a polymer film coated with a metal. Alternatively, the collector section is formed from a carbon film coated with the metal. The contact section is formed, for example, from a metal foil. Advantageously, the weight of a metal-coated polymer or carbon film is less than that of a metal foil of the same size. As a result, the weight of the entire electrode is also reduced, and the gravimetric energy density of a battery cell comprising the electrode is increased.

[0019] Additionally or alternatively, the collector section and the contact section differ in other physical properties, for example, their surface structure, roughness, and / or porosity. Advantageously, different surface structures enable the surface structure of the collector section to be provided and configured for comparatively reliable adhesion of the active material coating, while the surface structure of the contact section is provided and configured for comparatively reliable electrical and / or mechanical contact with the tab or with the housing.

[0020] According to an expedient embodiment, the collector section is coated with an active material. Preferably, the collector section is coated with the active material on both sides. If the electrode is provided as an anode, a copper foil, for example, forms the collector section, with graphite, graphene, lithium titanate (LTO), or so-called hard carbon, soft carbon, and / or carbon nanotubes being used as the (anode) active material. Alternatively, the collector section is provided with silicon, with a silicon-based anode material, with lithium as the active material. Alternatively or additionally, the anode is provided with another material known from the prior art as an active material for an anode.If the electrode is intended as a cathode, an aluminum foil, for example, forms the collector section, wherein the active material can be a lithium nickel cobalt aluminum oxide (NCA), a lithium iron phosphate (LFP), a lithium nickel manganese cobalt oxide (NMC), sulfur, a sulfur compound, lithium manganese oxide (LMO), lithium manganese nickel oxide (LMNO), lithium cobalt oxide (LCO), LiFeSO 4 F, LiTiS 2 or another material known from the prior art as an active material for a cathode. The layer with active material expediently further comprises a binder and a conductive agent and / or further conductive additives, such as conductive carbon black, graphene, carbon nanotubes or carbon nanofibers.

[0021] Alternatively, particularly if the electrode is intended for use in a solid-state battery cell, the electrode section is not coated with active material. The lithium is then deposited directly onto the collector section during operation of the solid-state battery cell. For example, the collector section has a surface structure that promotes such deposition. For example, the surface structure serves to enlarge the surface area of ​​the collector section.

[0022] According to an advantageous development, the collector section has a first region and a second region, wherein the first region and the second region differ in terms of their electrical and / or thermal conductivity. The two regions are expediently arranged next to one another in the plane spanned by the collector section. The two regions have, for example, different thicknesses, i.e. spatial extents in a direction perpendicular to the plane spanned by the collector section, and / or different materials. For example, the first region surrounds the second region in a frame-like manner or is arranged circumferentially on the second region. In this way, it is possible to further adjust or adapt the thermal and electrical conductivity properties of the collector section.For example, the first region has a higher thermal and electrical conductivity than the second region, with the first region adjacent to the contact section, thus achieving comparatively good heat dissipation from the electrode. For example, the first region is formed from a metal foil coated with active material, with the metal foil being thinner in the second region.

[0023] According to an advantageous embodiment, the electrode base body has a plurality of contact sections, i.e., more than one contact section. In other words, the electrode base body has the contact section and further contact sections. In particular, the contact sections are arranged on a common edge or side of the collector section. The contact sections are, for example, identical in design. Alternatively, however, the contact sections can differ from one another in terms of their electrical and / or thermal conductivities. For this purpose, they have, for example, different thicknesses and / or are made of different materials.

[0024] Particularly if the electrode is intended for forming an electrode coil, it has a strip shape, i.e., an elongated form. The contact sections are then preferably arranged at equal or uneven spacing from one another along the (relatively long) longitudinal side of the collector section. Due to the use of multiple contact sections on one edge of the collector section, the overall resistance of the electrode is advantageously reduced.

[0025] Alternatively, according to an advantageous embodiment, the contact section extends along the entire width or along the entire length of the collector section. Compared to electrodes in which the contact section extends only along a comparatively small part of the length or width, the average path of an electron from the collector section to the contact section, and thus also the electrical resistance of the electrode, is reduced.

[0026] A further aspect of the invention relates to a (secondary) battery cell having an electrode in one of the variants described above. The battery cell is designed, for example, as a lithium-ion battery cell and can be designed as a pouch cell, a round cell, or a prismatic cell.

[0027] Preferably, each of the electrodes of the battery cell, i.e., all of its anodes and all of its cathodes, is designed in one of the variants described above. In particular, each of the electrodes of the battery cell has a collector section and a contact section, wherein the collector section and the contact section have different electrical conductivities and / or different thermal conductivities.

[0028] Furthermore, the electrode base bodies of the cathodes can be different from one another. Additionally or alternatively, the electrode base bodies of the anodes can be different from one another. For example, the battery cell has conventional electrodes in addition to the electrode(s) in one of the variants described above.

[0029] Another aspect of the invention relates to an electrically powered motor vehicle with a traction battery. This battery has at least one (secondary) battery cell in one of the variants described above.

[0030] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. In the drawings: Fig. 1 schematically shows an electrically driven motor vehicle whose traction battery (battery system) has a number of battery modules, wherein the battery modules in turn comprise a number of secondary battery cells designed as lithium-ion battery cells, Fig. 2a schematically shows a first variant of the electrode of one of the battery cells in plan view, wherein the electrode has an electrode base body with a contact section and with a collector section coated with active material, Fig. 2b schematically shows a side view of the electrode according to the Fig. 2a , wherein the contact section has a greater thickness than the collector section, Fig. 2c schematically shows a side view of the electrode according to an alternative embodiment of the first variant, wherein the contact section has a smaller thickness than the collector section, Fig. 3a schematically shows a side view of a second variant of the electrode, wherein the collector section is formed by a polymer or carbon foil provided with a metal layer, Fig. 3b schematically shows a plan view of an alternative embodiment of the second variant of the electrode, in which the collector section has a first region formed by a metal foil and a second region formed by a polymer or carbon foil provided with a metal layer, Fig. 3c schematically shows a cross section of the electrode of the alternative embodiment of the second variant with the Fig. 3b shown sectional plane IIIc, Fig. 4 schematically shows in plan view a third variant of the electrode, in which the contact section extends along the entire width of the collector section, and Fig. 5 schematically shows in plan view a fourth variant of the electrode, wherein the electrode is band-shaped and wherein the electrode has a plurality of contact sections on its long side.

[0031] Corresponding parts and sizes are always provided with the same reference symbols in all figures.

[0032] In Fig. 1 A motor vehicle 2 with a traction battery 4 is shown. The traction battery 4 has a number of battery modules 6, also referred to as cell modules, whereby for the purpose of better clarity, only two of the battery modules 6 are shown.

[0033] Each of the battery modules 6 in turn has a number of secondary battery cells 8 designed as lithium-ion battery cells, of which five are shown per battery module 6. The battery cells 8 are in the Fig. 1 For example, they are designed as pouch cells, with the battery cells 8 being electrically interconnected by means of their cell conductors 10. In particular, the battery cells 8 of each battery module 6 are interconnected in series and / or parallel to one another in a manner not shown in detail by means of their cell conductors 10. Furthermore, the battery modules 6 are interconnected in series and / or parallel to one another in a manner not shown in detail and are electrically connected to battery terminals 12 for a consumer.

[0034] A load is connected to the battery terminals 12 of the traction battery 4. This load is configured here as an inverter 14 of a drive train of the motor vehicle 2 and an electric motor 16 connected to the inverter. The inverter 14 converts the direct current or the direct voltage provided by the traction battery 4 into an alternating current or an alternating voltage suitable for operating the electric motor 16. In summary, the traction battery provides electrical energy for driving the motor vehicle 2.

[0035] In alternatives not further shown, the battery cells 8 are designed as round cells or as prismatic cells.

[0036] In the Fig. 2a A first variant of an electrode 18 of one of the battery cells 8 is shown. The electrode 18 comprises a foil-like electrode base body 20, which is formed by a collector section 22 as a current collector and by a contact section 24. The contact section 24 serves to electrically contact the electrode 18 with the cell conductor 10 within the battery cell 8, wherein the cell conductor 10 is led to the outside of the battery cell in order to be connected there.

[0037] In this first variant, the electrode base body 20 is formed as a (single) metal foil. Thus, the contact section 24 and the collector section 22 are formed monolithically, i.e., contiguously. The electrode 18 further comprises active material with which the collector section 22 is coated on both sides. This coating of active material is designated by the reference numeral 26.

[0038] The electrode base body 20 spans a plane, with the main directions of extension being designated B (for the width direction) and H (for the height direction) in the adjacent direction diagram. The direction perpendicular to this plane is designated by the reference symbol D (for the thickness direction). These directions apply analogously to the designs of the Figuren 2b bis 4 .

[0039] As in the Fig. 2b As can be seen, the collector section 22 has a thickness d Kol and the contact section has a thickness d Kon, wherein the thickness d Kon of the contact section 24 is greater than the thickness d Kol of the collector section 22. In other words, the spatial extent of the contact section 24 in the direction D is greater than the spatial extent of the collector section 22 in this direction.

[0040] In the Fig. 2c An alternative embodiment of the electrode of the first variant is shown. This alternative embodiment differs from the first variant only in that the thickness d Kol of the collector section 22 is greater than the thickness d Kon of the contact section 24.

[0041] In variants of the electrodes 18 not shown in detail according to the Figuren 2a bis 2c The collector section 22 is not provided with active material. During operation of the battery cell, the lithium is deposited on the surface of the collector section 22.

[0042] In summary, the contact section 24 and the collector section 22 according to the first variant and according to the alternative embodiment of the first variant have different thicknesses and thus different thermal and electrical conductivities.

[0043] In the Fig. 3a A second variant of the electrode 18 is shown. In the second variant, the collector section 22 and the contact section 24 are joined together. They are therefore not monolithically connected to one another. The contact section 24 is arranged on the edge, here on an edge of the collector section 22 extending in direction B. The contact section 24 is preferably formed as a metal foil as the first material M1. The collector section is formed by means of a polymer or carbon foil 28 as the second material M2. This is provided with a metal layer 30. The metal layer 30 is electrically connected to the contact section 24. In summary, the material M1 of the contact section 24 is different from the material M2 of the collector section 22.

[0044] According to an alternative not further illustrated, the collector section 24 and the contact section 24 are formed from foils of different materials, in particular from different metal foils, wherein the collector section 24 and the contact section 24 are joined together. For example, the collector section 24 is coated with active material.

[0045] In the Figuren 3b and 3can alternative embodiment of the second variant of the electrode 18 is shown. Here, the collector section 22 has two regions 32 and 34. The first region 32 is formed from a metal foil and is electrically connected to the contact section 24. For example, the first region 32 and the contact section are formed as one piece, in other words monolithic. The second region 34 of the collector section 22 is formed from a polymer or carbon foil 28, which is provided with a metal layer 30 on both sides. For example, the first region 32 surrounds the second region 34 in a frame-like manner. Alternatively, the first region 32 is designed in the shape of a band, which extends between the second region 34 and the contact section 24 along the edge of the collector section 22 facing the contact section 24.

[0046] In summary, the first region 32 and the second region 34 are thus different in terms of their electrical and / or thermal conductivity.

[0047] In the Fig. 4 A third variant of the electrode 18 is shown. In this case, the contact section 24 extends along the entire width of the collector section 22, i.e. along the complete extent of the collector section 22 in direction B. In this case, the collector section 22 points in a manner analogous to the representations to the Figuren 2a bis 2c a different thickness d Kol than the contact section 24, and / or the contact section 24 is analogous to the representations of the Figuren 3a bis 3c made of a different material than the collector section 22.

[0048] In the Fig. 5A further, fourth variant of the electrode 18 is shown. This is band-shaped. The electrode thus spans a plane, with the main extension directions of the electrode 18 forming the longitudinal direction L and the vertical direction H. Furthermore, the extension of the electrode 18 in the longitudinal direction L is comparatively large compared to the extension in the vertical direction H. Such a band-shaped electrode 18 is intended, for example, for the formation of an electrode coil (jelly roll) or a flat coil, which are typically used in round cells or prismatic cells.

[0049] The electrode base body 20 has the collector section 22 and a plurality of contact sections 24. These are arranged here, for example, on a common longitudinal side 36 of the collector section 22 extending in the longitudinal direction L. For example, the contact sections are configured identically to one another. However, it is also possible for the contact sections to have different thicknesses and / or different longitudinal extensions and / or to be formed from different materials. The collector section is formed, for example, from a metal foil provided with active material or from a polymer or carbon foil provided with a metal layer.

[0050] At most, at least one of the contact sections 24 has a different thickness d Kon than the collector section 22 and / or is formed from a different material than the collector section 22.

[0051] In summary, in all variants and configurations presented above, the electrical conductivity σ Kol of the collector section 22 and / or the thermal conductivity λ Kol of the collector section 22 is different from the electrical conductivity σ Kon of the contact section 24 or from the thermal conductivity λ Kon of the contact section. In other words: σ Kol ≠ σ Kon , and / or λ Kol ≠ λ Kol .

[0052] In this way, it is advantageously possible for the electrical conductivities and / or the thermal conductivities of the collector section 22 and the contact section 24 to be adapted independently of one another to a respective requirement of the battery cell or its electrodes, in particular to different requirements of the collector section 22 and the contact section 24 with regard to their thermal and / or electrical conductivities.

[0053] The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived therefrom by those skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the exemplary embodiments can also be combined with one another in other ways without departing from the subject matter of the invention. List of reference symbols

[0054] 2Electrically powered motor vehicle 4Traction battery 6Battery module 8Lithium-ion battery cell 10Cell arrester 12Battery connection 14Inverter 16Electric motor 18Electrode 20Electrode base body 22Collector section 24Contact section 26Active material coating 28Polymer or carbon film 30Metal layer 32First area of ​​the collector section 34Second area of ​​the collector section 36Long side BWidth direction DThickness direction HVertical direction LLongitudinal direction d Kol Thickness of the collector section d Kon Thickness of the contact section

Claims

1. Electrode (18) for a secondary battery cell (8) having an, in particular foil-like, electrode main body (20), - wherein the electrode main body (20) comprises a collector portion (22) as a current collector and a contact portion (24) for making electrical contact with a cell tab (ZA), and - wherein the collector portion (22) and the contact portion (24) have different electrical conductivities and / or different thermal conductivities, characterized in that - the electrode main body (20) is formed from a metal foil, wherein the collector portion (22) and the contact portion (24) of the electrode main body (20) have different thicknesses (dKol, dKon), or - the collector portion (22) is formed of a first material and the contact portion (24) is formed of a second material different to the first material.

2. Electrode (18) according to Claim 1, characterized in that the collector portion (22) is coated with active material.

3. Electrode (18) according to Claim 1 or 2, characterized in that the collector portion (22) is formed from a polymer film or a carbon foil, wherein the polymer film or the carbon foil is coated with a metal.

4. Electrode (18) according to one of Claims 1 to 3, characterized in that the collector portion (22) has a first region (32) and a second region (34), wherein the first region (32) and the second region (34) are different in terms of their electrical and / or thermal conductivity.

5. Electrode (18) according to one of Claims 1 to 4, characterized in that the electrode main body (20) has multiple contact portions (24).

6. Electrode (18) according to one of Claims 1 to 5, characterized in that the contact portion (24) extends along the entire width of the collector portion (22).

7. Secondary battery cell (8), in particular lithium-ion battery cell, having an electrode (18) according to one of Claims 1 to 6.

8. Electrically driven motor vehicle (2) having a traction battery (4) which has a secondary battery cell (8) designed according to Claim 7.