Electrode winding and energy store comprising the electrode winding

Abstract

The invention relates to an electrode winding having a winding core, comprising - a wound inner current collector layer, wherein an inner electrode layer is arranged on the inner current collector layer, - a wound outer current collector layer, wherein an outer electrode layer is arranged on the outer current collector layer, - wherein the inner electrode layer and the outer electrode layer are arranged adjacent to one another and a separator layer is arranged between the inner and the outer electrode layer, - wherein the inner current collector layer and the outer current collector layer extend radially outwards from the winding core and the inner electrode layer is arranged closer to the winding core than the outer electrode layer, - wherein the inner current collector layer has an inner load with a mass of inner electrode layer per unit area of inner current collector layer and the outer current collector layer has an outer load with a mass of outer electrode layer per unit area of outer current collector layer, wherein the inner load decreases from the winding core outwards or the outer load increases from the winding core outwards. With this type of electrode winding, the surface capacitances of the inner electrode layer and the outer electrode layer can be adapted to each other.

Description

[0001] Electrode winding and energy storage comprising the electrode winding

[0002] The present invention relates to an electrode coil and an energy storage device comprising the electrode coil.

[0003] Energy storage devices, such as lithium-ion batteries, require a high surface capacitance on the anode and cathode to achieve high storage capacity. Both the anode and the cathode of energy storage devices usually have a current collector foil to which the respective electrochemically active electrode materials are applied. To achieve high storage capacity, a high surface capacitance, a large mass of electrode material must be applied per unit area of ​​the current collector foil. Furthermore, the surface capacitances of the anode material and the cathode material must be matched to one another. Otherwise, metal can be deposited on the anode if its surface capacitance is too low compared to the cathode. Particularly in lithium-ion batteries, lithium plating can depose, which contributes to the aging of lithium-ion batteries.On the other hand, a high surface capacity of the anode compared to the cathode leads to high costs and a high weight of the energy storage device.

[0004] It is an object of the present invention to provide an electrode coil that is improved with respect to the above-mentioned disadvantages. A further object of the present invention is to provide an energy storage device comprising the electrode coil that is improved with respect to the above-mentioned disadvantages.

[0005] One aspect of the invention relates to an electrode coil having a coil core. The electrode coil comprises a coiled inner current collector layer, with an inner electrode layer disposed on the inner current collector layer. The electrode coil further comprises a coiled outer current collector layer, with an outer electrode layer disposed on the outer current collector layer. The inner electrode layer and the outer electrode layer in the electrode coil are disposed adjacent to one another, with a separator layer disposed between the inner and outer electrode layers. The inner current collector layer and the outer current collector layer extend radially outward from the coil core. The inner electrode layer is disposed closer to the coil core than the outer electrode layer.The inner current collector layer has an internal loading with a mass of inner electrode layer per unit area of ​​inner current collector layer. The outer current collector layer has an external loading with a mass of outer electrode layer per unit area of ​​outer current collector layer. In the electrode winding, either the internal loading decreases from the winding core outwards, or the external loading increases from the winding core outwards.

[0006] Due to the changing internal or external loading, the surface capacitances of the inner or outer electrode layers can change from the winding core outward, adapting to the curvature of the current collector layers and the electrode layers applied to them in the electrode winding. This allows the surface capacitances of the inner and outer electrode layers to be adapted to each other.

[0007] Due to the curvature of the wound inner current collector layer and the wound outer current collector layer, and the corresponding curvature of the electrode layers applied to the current collector layers, the arc length of the wound current collector layers and the electrode layers applied thereon changes from the winding core outwards. This leads to a change in the areal capacitances of the wound inner and outer electrode layers, extending from the winding core outwards. The changing internal loading of the inner electrode layer or the changing external loading of the outer electrode layer provided according to the invention can reduce or compensate for the change in the areal capacitances in the electrode winding due to the different arc lengths.This allows the surface capacitances of the opposing inner electrode layer and the outer electrode layer to be adapted to the curvature of the layers in the electrode coil.

[0008] The internal loading as well as the external loading can be expressed, for example, in the unit mg of internal or external electrode material per unit area of ​​the current collector layer, for example cm 2 , must be specified (g / cm 2 ).

[0009] Either the inner or outer electrode layer can be an anode layer, with the other electrode layer then being a cathode layer. Preferably, the inner electrode layer is an anode layer and the outer electrode layer is a cathode layer.

[0010] If the internal loading decreases from the winding core outwards or the external loading increases from the winding core outwards, the loading of the opposite current collector layer with the corresponding electrode layer applied there preferably does not change. This means that if the internal loading of the inner current collector layer with the inner electrode layer decreases from the winding core outwards, the external loading of the outer current collector layer with the outer electrode layer does not change from the winding core outwards. Conversely, if the external loading of the outer current collector layer with the outer electrode layer increases from the winding core outwards, the internal loading of the inner current collector layer with the inner electrode layer does not change from the winding core outwards.

[0011] This makes it particularly easy to adjust the loading of only one current collector layer with the corresponding electrode layer, while the loading of the other current collector layer with the corresponding electrode layer does not need to be changed. This makes it particularly easy to produce an electrode coil with an adjusted loading.

[0012] The internal loading can be reduced or the external loading can be increased in order to keep the ratio N / P of the anode surface capacitance N to the cathode surface capacitance P, starting from the winding core outwards, within a reference range of the N / P ratio. This makes it particularly easy to provide an electrode winding which has a constant N / P ratio of the anode surface capacitance N to the cathode surface capacitance P within a reference range. In particular, the reference range of the N / P ratio can be in a range from 1.0 to 1.2, preferably in a range from 1.04 to 1.15, in particular in a range from 1.084 to 1.120.

[0013] The N / P ratio can be defined as (area weight of the anode x proportion of the electrochemically active material in the anode layer x specific discharge capacity of the electrochemically active material of the anode) / (area weight of the cathode x proportion of the electrochemically active material in the cathode layer x specific discharge capacity of the electrochemically active material of the cathode). The proportion of the electrochemically active material in either the anode layer or the cathode layer is given by the percentage of the electrochemically active material in the respective total electrode layer. In addition to the electrochemically active material, the electrode layer can also comprise binders and at least one electrically conductive additive. The area weight of either the anode or the cathode can preferably be expressed in the unit mg / cm 2The specific discharge capacity of the electrochemically active material, specified, for example, in the unit mAh / g, is specific to each electrochemically active material and can be determined, for example, by measuring the specific capacity of an electrochemically active material in charge and discharge cycles. For example, the specific discharge capacity of the electrochemically active cathode material NCM111 Li(NiO.33Coo.33Mno.33)O2) is 145 mAh / g.

[0014] In an angular range as a section of the electrode coil, the average length of the inner current collector layer and the outer current collector layer and the corresponding electrode layer located thereon can be calculated as the arc length in the angular range. The specific areal capacitances N and P of the anode electrode material and the cathode electrode material can then be obtained, and the N / P ratio can be calculated according to the above formula. If the calculated N / P ratio lies outside the reference range, it can be brought back within the reference range either by increasing the electrochemically active material of the inner electrode layer or by decreasing the electrochemically active material of the outer electrode layer.

[0015] Either the internal loading can have a maximum value of the internal loading on the inner current collector layer near the winding core, or the external loading can have a minimum value of the external loading on the outer current collector layer near the winding core. Such a maximum value or minimum value of the external loading is particularly well suited to compensate for the strong curvature of the inner electrode layer and the outer electrode layer near the winding core and the associated large differences in the arc length of the inner electrode layer and the outer electrode layer.

[0016] A change in the internal loading can become smaller as the distance from the winding core increases, starting from the winding core towards the outside. A change in the external loading can become smaller as the distance from the winding core increases, starting from the winding core towards the outside. The change in the loading can relate in particular to the change in the loading with electrode material on adjacent surface units of the respective current collector layer. For example, the change, in particular a decrease, in the internal loading starting from the winding core can decrease as the distance from the winding core between adjacent surface units of the inner current collector layer increases. Furthermore, a change, in particular an increase in the external loading starting from the winding core can also decrease as the distance from the winding core between adjacent surface units of the outer current collector layer increases.

[0017] The internal loading with the inner electrode layer on the inner current collector layer can converge from the winding core outward toward a minimum limit of the internal loading. Alternatively, the external loading with the outer electrode layer on the outer current collector layer can converge from the winding core outward toward a maximum limit of the external loading.

[0018] As the distance from the winding core increases, the difference in arc length between an adjacent inner and outer electrode layer decreases. This reduces the need to compensate for the differences in arc length between the adjacent inner and outer electrode layers by changing the inner or outer loading.

[0019] The inner electrode layer can have a constant composition from the winding core outwards. In particular, the thickness of the inner electrode layer on the inner current collector layer can then decrease from the winding core outwards with increasing distance from the winding core. With a constant composition of the inner electrode layer, this corresponds to a reduction in the loading of the inner current collector layer with the inner electrode layer.

[0020] The outer electrode layer can have a constant composition from the winding core outward. In particular, the thickness of the outer electrode layer on the outer current collector layer can then increase from the winding core outward with increasing distance from the winding core. With a constant composition of the outer electrode layer, this corresponds to an increase in the loading of the outer current collector layer with the outer electrode layer.

[0021] In one embodiment of the present invention, the internal loading of the inner current collector layer with the inner electrode layer can decrease from the winding core outwards, wherein the external loading of the outer current collector layer with the outer electrode layer remains the same from the winding core outwards. In another embodiment of the present invention, the external loading of the outer current collector layer with the outer electrode layer can increase from the winding core outwards, wherein the internal loading of the inner current collector layer with the inner electrode layer remains the same from the winding core outwards. In such electrode windings, only either the internal loading or the external loading can be adjusted, wherein the other loading can remain the same from the winding core outwards.This simplifies the production of the electrode windings, but still allows the internal or external loading to be adapted to the respective arc lengths of the adjacent inner and outer electrode layers. The internal loading can decrease continuously or gradually from the winding core outwards. With a gradually decreasing internal loading, the internal loading can have a constant first internal loading for a first partial area of ​​the surface of the inner current collector layer and, for example, for a second partial area of ​​the surface of the inner current collector layer that is adjacent to the first partial area, a constant second internal loading that is different from the first internal loading.If the second partial area of ​​the surface of the inner current collector layer is further away from the winding core than the first partial area, the second internal loading on the second partial area may be smaller than the first internal loading.

[0022] The external loading can increase continuously or in steps, starting from the winding core outwards. With a stepwise increase in the external loading, the external loading can remain the same in a first and a second sub-region of the surface of the outer current collector layer, wherein the second sub-region is adjacent to the first sub-region and has a different external loading compared to the first sub-region. In particular, the second sub-region of the surface of the outer current collector layer can have a higher external loading than the first sub-region if the second sub-region is farther away from the winding core than the first sub-region.

[0023] Preferably, the inner electrode layer is an anode layer, and the outer electrode layer is a cathode layer. Further preferably, the external loading of the cathode current collector layer with the cathode layer is varied, while the loading of the anode current collector layer with the anode layer remains the same. Since, in particular, the external loading of the cathode current collector layer with the cathode layer is reduced, changing the external loading results in an electrode coil with an improved N / P ratio while simultaneously being lighter and therefore cost-effective.

[0024] In a further embodiment of an electrode coil, the inner current collector layer has a first inner main surface and an opposite second inner main surface. The inner electrode layer is arranged as a first inner electrode layer on the first inner main surface, and a second inner electrode layer is arranged on the second inner main surface. The outer current collector layer has a first outer main surface and an opposite second outer main surface. The outer electrode layer is arranged as a first outer electrode layer on the first outer main surface, with a second outer electrode layer being arranged on the second outer main surface. The first inner electrode layer and the first outer electrode layer are arranged adjacent to one another and separated from one another by a separator layer.The second inner electrode layer is arranged closer to the winding core than the first inner electrode layer. In such an electrode winding, either the first inner loading with a mass of first inner electrode layer on a first surface of the first inner main surface of the inner current collector layer can be greater than a second inner loading with a mass of second inner electrode layer on a second surface of the second inner main surface, wherein the first surface is opposite the second surface. Alternatively, in such an electrode winding, a first outer loading with a mass of first outer electrode layer on a first surface of the first outer main surface of the outer current collector layer can be smaller than a second outer loading with a mass of second outer electrode layer on a second surface of the second outer main surface, wherein the first surface is opposite the second surface.

[0025] In such an electrode coil, both main surfaces of the inner current collector layer and the outer current collector layer are covered with inner electrode layers and outer electrode layers, respectively. This increases the overall capacity and energy density of an energy storage device with such an electrode coil. The overall capacity of a layer arrangement comprising the inner current collector layer with the first and second inner electrode layers arranged thereon, or the overall capacity of a layer arrangement comprising an outer current collector layer with a first and second outer electrode layer arranged thereon, remains the same for the first surface and the opposite second surface, although the loadings of the opposite electrode layers differ.

[0026] The size of the areas of the first surface and the second opposite surface can be the same for both the inner current collector layer and the outer current collector layer.

[0027] For example, the first internal load, starting from the winding core outwards, may decrease with increasing distance from the winding core and the second internal load, starting from the winding core outwards, may increase with increasing distance from the winding core.

[0028] In another embodiment, the first external loading on the first main surface of the outer current collector layer can increase outward from the winding core, and the second external loading on the second main surface of the outer current collector layer can decrease outward from the winding core. Preferably, the first and second outer electrode layers are cathode layers, and the first external loading with the first outer cathode layer increases outward from the winding core, and the second external loading with the second outer cathode layer decreases outward from the winding core.

[0029] Furthermore, the sum of the first internal loading on the first surface and the second internal loading on the second surface opposite the first surface can remain the same from the winding core outwards.

[0030] Likewise, the sum of the first external loading on the first surface of the outer current collector layer and the second external loading on the second surface of the outer current collector layer opposite the first surface can remain the same from the winding core outwards.

[0031] This makes it possible to provide current collector layers with electrode layers arranged thereon, which, starting from the winding core outwards, have the same total surface capacitance on opposite surfaces of the current collector layer, despite the change in either the first internal loading and the second internal loading or despite the change in the first external loading and the second external loading.

[0032] The inner electrode layer, the optional second inner electrode layer, the outer electrode layer and the optional second outer electrode layer may comprise a binder, an electrochemically active material and an electrically conductive additive.

[0033] Electrochemically active material can be designed to absorb and release metal ions, in particular lithium ions or sodium ions, during operation of the energy storage device.

[0034] Either the inner electrode layer and the optionally present second inner electrode layer or the outer electrode layer and the optionally present second outer electrode layer can be an anode of a lithium-ion battery. In this case, the electrochemically active material can be selected from a group consisting of: carbonaceous materials, silicon, nano-silicon, silicon composites, silicon suboxides, silicon alloys, lithium, lithium alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, niobium pentoxide, titanium dioxide, titanates, lithium titanate (Li^2 O^2), tin dioxide, and mixtures thereof.Either the inner electrode layer and the optionally present second inner electrode layer or the outer electrode layer and the optionally present second outer electrode layer can be a cathode of a lithium-ion battery, wherein the electrochemically active material is then selected from the group consisting of: lithium transition metal oxides, lithium nickel cobalt manganese compounds, lithium nickel cobalt aluminum oxides, lithium olivines, lithium spinels or combinations thereof.

[0035] Either the inner electrode layer and the optionally present second inner electrode layer or the outer electrode layer and the optionally present second outer electrode layer can be an anode of a sodium-ion battery and can be selected from a group consisting of: hard carbon, and graphene or combinations thereof.

[0036] Either the inner electrode layer and the optionally present second inner electrode layer or the outer electrode layer and the optionally present second outer electrode layer can be a cathode of a sodium-ion battery, wherein the electrochemically active material is then selected from a group consisting of: layered transition metal oxides, such as Na2 / 3Fei / 2Mn2O2, NaO76MnO5Nio3FeOiMgO2, or NaNiI / 4NaI / 6Mn2 / 12Ti4 / 12Sni / 12O2 and combinations thereof.

[0037] The electrically conductive additive may be selected from a group consisting of: conductive carbon black, carbon nanotubes, graphene, graphite, expanded graphite, carbon nanofibers, porous carbons, and combinations thereof.

[0038] The binder can be selected from a group consisting of: cellulose, cellulose derivatives, rubbers, polyolefins, polyperfluoroolefins, polyacrylic acid, and combinations thereof. In particular, binders such as polyacrylic acid, polyvinylidene fluoride, styrene-butadiene rubber, and carboxymethyl cellulose can be used.

[0039] The inner and outer current collector layers are preferably current collector foils. The current collector layers preferably comprise or are made of a metal or metal alloy, wherein the metal or metal alloy is selected from a group consisting of: copper, aluminum, nickel, and copper alloys. A current collector layer for the anode preferably comprises or is made of copper. A current collector layer for the cathode preferably comprises or is made of aluminum.

[0040] The layer arrangements comprising the inner or outer current collector layer and the inner or outer electrode layer, and the optionally present second inner and second outer current collector layer, can be applied to the current collector layer, for example, by doctor blades or using slot dies in a wet-chemical process and then dried. Alternatively, the inner and outer electrode layers can also be produced on the respective current collector layers using a solvent-free process, whereby a dry mixture of an electrochemically active compound, a dry binder, and optionally an electrically conductive additive is calendered onto the respective current collector layers.

[0041] The present invention also relates to an energy storage device comprising a housing, an electrode coil as already described and an electrolyte.

[0042] The energy storage device can in particular be a lithium-ion accumulator or a sodium ion battery.

[0043] In particular, an electrolyte solution containing an aprotic solvent such as ethylene carbonate (EC), propylene carbonate (PV), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or 1,2-dimethoxyethane can be used as the electrolyte. In a lithium-ion battery, a lithium conducting salt, such as lithium hexafluorophosphate (LiPFe), lithium tetrafluoroborate (UBF4), or lithium bis(oxalato)borate (LiBOB), dissolved in the aprotic solvent, can be used. In a sodium-ion battery, conducting salts such as NaClO4 or NaPF6 can be used.

[0044] Such energy storage devices can have a longer service life due to the use of an electrode winding according to the invention. Furthermore, such energy storage devices can be manufactured more cost-effectively due to the improved N / P ratio between the anode surface capacitance and the cathode surface capacitance. Furthermore, with lithium-ion batteries as energy storage devices, the risk of lithium plating, or deposition of lithium on the anode, can be reduced or even eliminated.

[0045] In the following, aspects of the present invention will be explained in more detail with reference to figures and exemplary embodiments. They show:

[0046] Figure 1 shows a schematic cross-section through an electrode coil,

[0047] Figure 2A shows a schematic cross-section through a conventional flat electrode stack of a rechargeable battery and the corresponding lengths for calculating an N / P ratio in the flat electrode stack, Figures 2B and 2C show a schematic cross-section through an electrode coil and the resulting arc lengths for calculating the N / P ratio,

[0048] Figure 3 shows a diagram with a progression of the first external loading and the second external loading with increasing number of turns in the electrode stack,

[0049] Figure 4 shows a diagram with a course of the inner N / P ratio and the outer N / P ratio in an electrode winding according to the invention with increasing number of turns in the electrode stack,

[0050] Figures 5A and 5B show schematic cross sections of developed layer arrangements of an inner current collector layer with inner electrode layers applied thereon and a layer arrangement of an outer current collector layer and outer electrode layers applied thereon,

[0051] Figures 6A and 6B show schematic cross sections of a further embodiment of developed layer arrangements of an inner current collector layer with inner electrode layers applied thereon and a layer arrangement of an outer current collector layer with outer electrode layers applied thereon, and

[0052] Figures 7A and 7B show schematic cross sections of an embodiment of layer arrangements, wherein only one inner electrode layer is applied to the inner current collector layer and also only one outer electrode layer is applied to the outer current collector layer.

[0053] In the following, identical elements or elements with the same function are given the same reference symbols.

[0054] Figure 1 shows a schematic cross-section through an electrode coil. For reasons of clarity, the different internal or external loads that are present in electrode coils according to the invention are not shown in Figure 1. The electrode coil 1 has a coil core 2, with a layer arrangement 10 consisting of an inner current collector layer 5 with a first inner electrode layer 4 and a second inner electrode layer 3 and a layer arrangement 11 with an outer current collector layer 9, a first outer electrode layer 7 and a second outer electrode layer 8 winding around the coil core 2. A separator layer 6 is arranged between the layer arrangement 10 and the layer arrangement 11. The first inner electrode layer 4 has an end 4A that is arranged adjacent to the coil core 2. Analogously, the second inner electrode layer 3 has an end 3A that is arranged adjacent to the coil core 2.The first outer electrode layer 7 applied to the outer current collector layer 9 has one end 7A, and the second outer electrode layer 8 has one end 8A, both ends 7A and 8A being adjacent to the winding core 2. The first inner electrode layer 4 and the second inner electrode layer 3 further have ends 4B and 3B, and the first outer electrode layer 7 and the second outer electrode layer 8 have ends 7B and 8B, these ends 4B, 3B, 7B, and 8B being located at the outer end of the electrode winding. In such an electrode winding 1, an internal N / P ratio can be calculated between the first inner electrode layer and the first outer electrode layer with the separator layer 6 located therebetween, indicated by the box provided with the reference numeral 12.Furthermore, a first external N / P ratio can be calculated between the second outer electrode layer 8 and the second inner electrode layer 3 with the separator 6 located therebetween, as indicated by the box with the reference number 13. With increasing number of windings and increasing distance from the winding core 2, further N / P ratios can be calculated. For example, a second external N / P ratio 22 can be calculated between the first inner electrode layer and the first outer electrode layer in the 2nd winding. With increasing number of windings, the arc lengths of the sections of the electrode layers on the current collector layers used to calculate the N / P ratio change, so that the loadings of the inner and outer electrode layers are adjusted depending on the distance from the winding core in order to keep the N / P ratio within a desired reference range.

[0055] Figure 2A shows a schematic cross-section through an electrode stack comprising a layer arrangement of superimposed flat electrode layers with current collector layers and separator layers. The area marked with box 14A is used to calculate the ratio of the surface capacitance N of the anode to the surface capacitance P of the cathode, the N / P ratio. Shown is a layer arrangement 10 comprising an inner current collector layer 5, with a first inner electrode layer 4 present on one main surface of the inner current collector layer and the second inner electrode layer 3 present on the opposite main surface of the inner current collector layer. The inner electrode layers comprise electrochemically active materials for an anode layer, as described above.The layer stack also includes a layer arrangement 11, which includes an outer current collector layer 9, with a first outer electrode layer 7 applied to one of its main surfaces and a second outer electrode layer 8 applied to the opposite main surface. The outer electrode layers comprise electrochemically active materials for a cathode. Figure 2A shows that with an increasing number of stacks, the lengths of the electrode layers relevant for calculating the N / P ratio do not change within the region 14A.

[0056] In contrast to the electrode stack in Figure 2A, Figure 2B shows a schematic cross-section through an electrode coil with a coil core 2. The region 14A used to calculate the N / P ratio in the electrode stack is marked as a dashed box. Due to the curvature of the layers in the electrode coil, in contrast to the electrode stack, the region 14B marked with the various gray layers must be used to calculate the N / P ratio in the electrode coil. This region 14B differs significantly from the region 14A in the electrode stack due to the curvature of the layers. Due to the curvature of the layers, for example, the hatched region marked 15 is missing in the first inner electrode layer compared to the electrode stack.As already described above, an internal N / P ratio can be calculated between the anode surface capacitance of the first inner electrode layer 4 and the cathode surface capacitance of the first outer electrode layer 7, as indicated by the bracket marked 12. Furthermore, a first external N / P ratio can be calculated between the second outer electrode layer 8 and the second inner electrode layer 3, as indicated by the bracket marked 13. Due to the curvature of the current collector layers and the electrode layers located thereon decreasing outward from the winding core 2, different arc lengths must be used when calculating the N / P ratios.Figure 20 shows, by way of example, a schematic cross-section of the respective lengths of the first inner electrode layer 4 and the first outer electrode layer 7, which must be used as a basis for calculating the inner N / P ratio 12 due to the different curvatures. The length of the first inner electrode layer 4 is shorter than the length of the first outer electrode layer 7 due to the greater curvature closer to the winding core. In order to keep the N / P ratio within the desired reference range, either the loading, i.e. the mass of electrode material per unit area of ​​the current collector layer, for the first inner electrode layer 4 can be increased or the loading for the first outer electrode layer 7 can be reduced.

[0057] Figure 3 shows in a diagram the calculated loading 70 of the first outer electrode layer 7 and the calculated loading 8 0 of the second outer electrode layer 8 in mg / cm 2Current collector layer to maintain the N / P ratio of an electrode coil in a desired range between 1.084 and 1.120. The number of windings in the electrode coil, starting from the winding core (winding 0), is plotted on the x-axis 17. The theoretical loadings were calculated, as described above, for an electrode material containing 96 weight percent of the electrochemically active cathode material NCM811 (LiNi0.8Co0.1Mn0.1O2). The nominal target value for the cathode material loading is 20.4 g of electrode material per cm 2 Current collector layer with theoretically equal arc lengths for the anode current collector layer and the cathode current collector layer. On the y-axis, the loading is in mg / cm 2 current collector layer. Figure 3 shows that on the winding core with winding 0, the loading 7C of the first outer electrode layer 7 has a minimum value of just over 19.4 g of electrode material per cm 2current collector layer and with increasing number of windings the loading 7C increases to approximately 19.84 g of electrode material per cm 2 Current collector layer. In contrast, the loading 8C of the second outer electrode layer 8 on the winding core at winding 0 is limited to a maximum value of 20.5 g of electrode material per cm 2 current collector layer and then decreases with increasing number of developments in the electrode winding to a value of about 20 g of electrode material per cm 2 Current collector layer. The loading of the first inner electrode layer 4, which is opposite the first outer electrode layer 7, and the loading of the second inner electrode layer 3, which is opposite the second outer electrode layer in the electrode coil, were kept constant, with the respective electrode layers having a loading of 12.6 g of electrode material per cm 2Current collector layer and the electrochemically active electrode material is graphite with a proportion of 96 weight percent of the anode material.

[0058] Instead of a continuous increase or decrease in the loading, it can also be increased or decreased stepwise. This is shown by the dashed lines, designated with reference numeral 7D, for the loading of the first outer electrode layer. For the loading of the second outer electrode layer, this is shown by the dashed lines, designated with reference numeral 8D. A stepwise increase or decrease in the loading of a current collector layer with an electrode layer can result in simpler production, depending on the machines used.

[0059] Figure 4 shows the calculated course of the internal N / P ratio 12A, which is calculated between the first inner electrode layer and the first outer electrode layer, and the course of the first outer N / P ratio 13A, which is calculated between the second outer electrode layer and the second inner electrode layer, for the continuous changes in loading shown in Figure 3. The x-axis 17 again indicates the number of windings starting from the winding core with winding 0, while the y-axis 19 indicates the N / P ratio. As can be seen, both N / P ratios run within a narrow range of approximately 1.085 to 1.12 and converge from approximately the 15th winding of the electrode winding into a narrower range of the N / P ratio of approximately 1.09 to 1.11.In an electrode winding in which the N / P ratio between different windings of the electrode winding is not adjusted as a function of the distance from the winding core by changing the loading of the respective current collector layers with the corresponding electrode layers, the N / P ratio ranges in a much larger range between approximately 1.06 to 1.12.

[0060] Figures 5A and 5B show the unwound layer arrangement 10 comprising the inner current collector layer 5 with the first inner electrode layer 4 and the second inner electrode layer 3 applied thereon, and the unwound layer arrangement 11 comprising the outer current collector layer 9 with the electrode layers, the first outer electrode layer 7 and the second outer electrode layer 8 applied thereon. Figures 5A and 5B show schematic cross sections of both layer arrangements, with the ends 3A, 4A and 7A, 8A of the respective electrode layers being visible on the left side of both figures, which are arranged near or adjacent to the winding core 2 in the electrode winding 1. The ends 3B, 4B and 7B, 8B of the respective electrode layers being visible on the right side of both figures, which are present at the outer end of the electrode winding at the maximum distance from the winding core 2.The compositions of the respective electrode layers do not change from the winding core to the outer end, so that only the loadings of the outer layers change.

[0061] Current collector layer 9 with the first outer electrode layer 7 and the second outer electrode layer 8 change from the winding core to the outer end of the electrode winding. In the electrode winding, the first inner electrode layer 4 of Figure 5B is arranged adjacent to the first outer electrode layer 7 of Figure 5A, whereby the separator layer 6 located between them in the electrode winding is not shown.

[0062] The layer arrangement 10 shown in Figure 5B with the first inner electrode layer and the second inner electrode layer serves as the anode in the electrode stack and has a constant thickness 4E or 3E of the respective electrode layers over the entire length from the winding core to the outer end of the electrode coil, with a constant composition of the electrode layers. The layer arrangement 11 shown in Figure 5A serves as the cathode in the electrode stack. Due to the strong curvature of the inner current collector layer 5 and the short arc length of the first inner electrode layer 4 close to the winding core, the loading of the first outer electrode layer 7 close to the winding core is reduced, which is shown in Figure 5A by the small thickness 7E of the first outer electrode layer 7.The outer current collector layer 9 can be divided into different adjacent surface units 30 with equal areas, which are separated from one another in Figure 5A by the dashed lines designated by reference numeral 20. With increasing distance from the winding core, the arc length of the first inner electrode layer 4, which is used as a basis for calculating the N / P ratio, increases, so that the loading of the outer current collector layer 9 with the first outer electrode layer 7 can continuously increase, which is expressed in an increasing thickness of the first outer electrode layer 7 on the outer current collector layer 9 with increasing distance from the winding core.In order to keep the surface capacitance of the outer current collector layer with the electrode layers located thereon as the cathode constant from the winding core to the end of the electrode winding, the loading of the second outer electrode layer opposite the first outer electrode layer is maintained such that for opposite surface units, the sum of the loading of the first outer electrode layer 7 and the second outer electrode layer 8 is the same. For example, the sum of the loadings 21 and 22, represented by the hatched areas, is exactly the same as the sum of the loadings 23 and 24, represented by the hatched areas further away from the winding core. The area of ​​the outer current collector layer 9 with the loadings 21 and 22 is exactly the same as the area of ​​the outer current collector layer 9 with the loadings 23 and 24.The change in the loading between adjacent surface units of the current collector layer 9 decreases from the winding core 2 towards the outer end of the electrode winding.

[0063] Figures 6A and 6B show a further embodiment of unwound layer arrangements 10 and 11 of an electrode coil according to the invention. In contrast to the layer arrangements 10 and 11 of Figures 5A and 5B, in these layer arrangements, the loading of the outer current collector layer 9 with the first outer electrode layer and the second outer electrode layer is kept the same, and only the loading of the inner current collector layer with the first inner electrode layer 4 and the second inner electrode layer 3 is changed. The loading of the inner current collector layer 5 with the first inner electrode layer 4 is maximum at the winding core and decreases from the winding core outwards with increasing distance from the winding core.Analogous to Figure 5A, in Figure 6B the sum of the loadings of opposite surface units 30 of the inner current collector layer 5, separated from one another by the dashed lines designated 20, is also the same for different opposite surface units. For example, the sum of the loadings 25 and 26 is equal to the sum of the loadings 27 and 28 and the sum of the loadings 29 and 30. Another embodiment of unrolled electrode layers of an electrode coil according to the invention is shown in Figures 7A and 7B. This embodiment corresponds to the embodiments shown in Figures 5A and 5B, but only each current collector layer is covered with one electrode layer. The inner current collector layer 5 is covered with the inner electrode layer 4, and the outer current collector layer 9 is covered with the outer electrode layer 7.Near the winding core, the thickness of the outer electrode layer 7 is small and increases with increasing distance from the winding core.

[0064] The invention is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, including, in particular, any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

Claims

Patent claims 1. An electrode coil having a coil core comprising a wound inner current collector layer, wherein an inner electrode layer is arranged on the inner current collector layer, a wound outer current collector layer, wherein an outer electrode layer is arranged on the outer current collector layer, - wherein the inner electrode layer and the outer electrode layer are arranged adjacent to each other and a separator layer is arranged between the inner and outer electrode layers, - wherein the inner current collector layer and the outer current collector layer extend radially outwardly from the winding core and the inner electrode layer is arranged closer to the winding core than the outer electrode layer, - wherein the inner current collector layer has an inner loading with a mass of inner electrode layer per unit area of inner current collector layer and the outer current collector layer has an outer loading with a mass of outer electrode layer per unit area of outer current collector layer, - whereby the internal loading decreases from the winding core outwards or the external loading increases from the winding core outwards.

2. Electrode coil according to the preceding claim, wherein either the inner or the outer electrode layer is an anode layer and the other electrode layer is a cathode layer, preferably wherein the inner electrode layer is an anode layer and the outer electrode layer is a cathode layer.

3. Electrode coil according to one of the preceding claims, wherein the internal loading is reduced or the external loading is increased, so that the ratio N / P of the anode surface capacitance N to the cathode surface capacitance P, starting from the coil core outwards, remains the same within a reference range, preferably wherein the reference range lies at values from 1.0 to 1.1, further preferably wherein the N / P ratio is defined as (area weight of the anode dex portion of the electrochemically active material in the anode layer x specific discharge capacity of the electrochemically active material of the anode) / (area weight of the cathode dex portion of the electrochemically active material at the cathode layer x specific discharge capacity of the electrochemically active material of the cathode).

4. Electrode coil according to one of the preceding claims, wherein the internal loading in the vicinity of the winding core has a maximum value of the internal loading on the inner current collector layer or the external loading in the vicinity of the winding core has a minimum value of the external loading on the outer current collector layer.

5. Electrode coil according to one of the preceding claims, wherein a change in the internal loading from the winding core outwards decreases with increasing distance from the winding core, preferably wherein the internal loading converges from the winding core outwards towards a minimum limit value of the internal loading.

6. Electrode winding according to one of the preceding claims, wherein the inner electrode layer has a constant composition starting from the winding core outwards and wherein the thickness of the inner electrode layer on the inner current collector layer decreases starting from the winding core outwards.

7. Electrode coil according to one of the preceding claims, wherein the internal loading decreases from the coil core outwards and wherein the external loading remains the same from the coil core outwards.

8. Electrode coil according to one of the preceding claims 1 to 5, wherein the external loading increases from the winding core outwards and wherein the internal loading remains the same from the winding core outwards 9. Electrode coil according to one of the preceding claims, - wherein the inner current collector layer has a first inner main surface and an opposite second inner main surface, and wherein the inner electrode layer is arranged as a first inner electrode layer on the first inner main surface, and wherein a second inner electrode layer is arranged on the second inner main surface, - wherein the outer current collector layer has a first outer main surface and an opposite second outer main surface, and wherein the outer electrode layer is arranged as a first outer electrode layer on the first outer main surface and wherein a second outer electrode layer is arranged on the second outer main surface, - wherein the first inner electrode layer and the first outer electrode layer are arranged adjacent to each other and the second inner electrode layer is arranged closer to the winding core than the first inner electrode layer, - wherein either a first internal loading with a mass of first inner electrode layer on a first surface of the first inner main surface of the inner current collector layer is greater than a second internal loading with a mass of second inner electrode layer on a second surface of the second inner main surface and wherein the first surface is opposite the second surface, or - wherein a first external loading with a mass of first outer electrode layer on a first surface of the first outer major surface of the outer current collector layer is smaller than a second external loading with a mass of second outer electrode layer on a second surface of the second outer major surface, and wherein the first surface is opposite the second surface.

10. Electrode coil according to the preceding claim, wherein the first internal loading decreases from the coil core outwards and the second internal loading increases from the coil core outwards.

11. Electrode coil according to the preceding claim, wherein the sum of the first internal loading on a first surface and the second internal loading on a second surface opposite the first surface remains the same from the coil core outwards.

12. Electrode coil according to one of the preceding claims, wherein the inner electrode layer, the optionally present second inner electrode layer, the outer electrode layer and the optionally present second outer electrode layer comprise a binder, an electrochemically active material and an electrically conductive additive.

13. Electrode coil according to the preceding claim, wherein either the inner electrode layer and the optionally present second inner electrode layer or the outer electrode layer and the optionally the second outer electrode layer present is an anode and wherein the electrochemically active material is selected from the group consisting of: carbonaceous materials, silicon, nano-silicon, silicon composites, silicon suboxides, silicon alloys, lithium, lithium alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, niobium pentoxide, titanium dioxide, titanates, lithium titanate (Li4Ti50i2), tin dioxide and mixtures thereof.

14. Electrode coil according to the preceding claim, wherein either the inner electrode layer and the optionally present second inner electrode layer or the outer electrode layer and the optionally present second outer electrode layer is a cathode and wherein the electrochemically active material is selected from the group consisting of: lithium transition metal oxides, lithium nickel cobalt manganese compounds, lithium nickel cobalt aluminum oxides, lithium olivines, lithium spinels or combinations thereof.

15. Energy storage device comprising: a housing, an electrode coil according to one of the preceding claims, and an electrolyte.

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