Sodium-ion battery and method for manufacturing a sodium-ion battery

Abstract

The invention relates to a sodium-ion accumulator (2) comprising an accumulator cell (4) in which at least one positive electrode (10) is arranged, wherein the at least one positive electrode (10) comprises a first electrode material (22) and a second electrode material (24), wherein the first electrode material (22) comprises a layered metal oxide material and wherein the second electrode material (24) comprises a polyanionic material

Description

[0001] The invention relates to a sodium-ion battery. Furthermore, the invention relates to a method for manufacturing a sodium-ion battery.

[0002] Lithium-ion batteries are already widely used as storage devices for electrical energy. They are also used in the automotive sector, where they serve in particular as so-called drive or traction batteries for powering hybrid or electric vehicles.

[0003] A typical lithium-ion battery consists primarily of a positive electrode, a negative electrode, a separator, and an electrolyte. Numerous variations exist regarding its precise construction. However, all designs share the common feature of containing free and therefore mobile lithium ions, specifically lithium ions that can freely migrate back and forth through the electrolyte between the negative and positive electrodes.

[0004] A possible method for manufacturing a lithium-ion battery is outlined in “Heimes, Heiner Hans; Kampker, Achim; Lienemann, Christoph; Locke, Marc; Offermanns (2018): Production process of a lithium-ion battery cell, VDMA Frankfurt, ISBN 978-3-947920-00-6”.

[0005] Various components are required for this or other processes. The production of some of these components is schematically illustrated, for example, in "Heimes, Heiner Hans; Kampker, Achim; Kreisköther, Kim; Michaelis, Sarah; Rahimzei, Ehsan; vom Hemdt, Ansgar (2019): Komponentenherstellung einer Lithium-Ion-Batteriezelle, PEM der RWTH Aachen & VDMA, ISBN 978-3-947920-06-8".

[0006] Sodium-ion batteries are currently less common than lithium-ion batteries, but their importance is increasing significantly. Sodium-ion batteries are very similar to lithium-ion batteries in terms of function and construction. The manufacturing processes are also very similar. A key difference lies in the use of different cathode materials in their production.

[0007] The object of the present invention is to provide an advantageously designed sodium-ion battery and an advantageous method for manufacturing a sodium-ion battery.

[0008] This problem is solved by a sodium-ion battery with the features of claim 1 and by a method with the features of claim 10. The advantages and preferred embodiments mentioned with regard to the sodium-ion battery are also transferable to the method and vice versa. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0009] The method according to the invention serves to manufacture sodium-ion batteries according to the invention and is accordingly designed for this purpose. Conversely, the sodium-ion battery according to the invention is manufactured using the method according to the invention.

[0010] The sodium-ion battery, i.e. the sodium-ion battery according to the invention, has at least one battery cell in which at least one positive electrode is arranged, i.e. expediently at least one electrode which acts as a cathode during a discharge process and as an anode during a charging process in the completed sodium-ion battery.

[0011] In some applications, two or more positive electrodes are arranged in the at least one accumulator cell. Preferably, all positive electrodes of the at least one accumulator cell are designed identically, specifically according to the type of the aforementioned at least one positive electrode, which will be described in more detail below.

[0012] Furthermore, in various applications, the sodium-ion battery has two or more battery cells. In these cases, preferably all battery cells of the sodium-ion battery are identically designed, specifically in the manner of at least one battery cell described above.

[0013] Furthermore, the at least one positive electrode, which will hereinafter also be referred to simply as the positive electrode, comprises a first electrode material and a second electrode material. The first electrode material is a layered metal oxide material, in particular at least a layered metal oxide material, and the second electrode material is a polyanionic material, in particular at least a polyanionic material. Thus, the at least one positive electrode comprises not just one so-called cathode material or cathode active material, but two, or at least two.

[0014] In at least some applications, the two cathode materials are spatially separated from each other in two layers, which are applied one on top of the other to a metal foil. In this case, the metal foil then conveniently forms a current collector for at least one positive electrode.

[0015] Regardless, the aforementioned layered metal oxide (LMO) material is typically a material with the chemical formula: N / a a Li b MO 2.

[0016] Here, the condition for index a is 0.7 ≤ a ≤ 1.05 and for index b the condition is 0 ≤ b ≤ 0.3.

[0017] Furthermore, the M in the aforementioned chemical formula stands for a number of transition metal ions, namely, for example: - two transition metal ions: M' x M'' y, where the index x is subject to the condition 0 ≤ x ≤ 1 and the index y is subject to the conditions 0 ≤ y ≤ 1 and x + y = 1, or - three transition metal ions: M' x M'' y M''' z , where the index x is subject to the condition 0 ≤ x ≤ 1, the index y to the condition 0 ≤ y ≤ 1 and the index z to the conditions 0 ≤ z ≤ 1 and x + y + z = 1.

[0018] A previously mentioned transition metal ion is also, for example, an ion of a metal from the following selection: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Lu, Ta, W, Re, Ir, Pt, Au, Cr, Al, Mg, Ca, Bi.

[0019] The aforementioned polyanionic material (PA: Polyanionic) is usually a material with the chemical formula: N / a b M2(PO4)3 or with the chemical formula: N / a c M2(PO4)2F 3-x O x .

[0020] Here, the condition for index b is 1 ≤ b ≤ 3, for index c the condition is 0 ≤ c ≤ 2, and for index x the condition is x = 0 or x = 2.

[0021] Furthermore, in this case, M stands for a metal from the following selection: Mn, Fe, Co, Ni, V, Sc, Cr, Al, Ti, Zr, Nb, Mo, Bi, Y, Tc, Ru, Rh, Pd, Ta, Lu, Hf, W, Re, Os, Ir, Pt, Au.

[0022] Further embodiments are preferred in which the weight of the layered metal oxide material constitutes at least 15% of the total weight of the layered metal oxide material and the polyanionic material.

[0023] If at least one of the two cathode materials, i.e., at least the layered metal oxide material or at least the polyanionic material or both, contains vanadium, embodiments are also preferred in which the weight of the total vanadium, i.e., the total vanadium in both cathode materials, is less than 20% of the sum of the weight of the layered metal oxide material and the weight of the polyanionic material.

[0024] As previously explained, in at least some applications the two cathode materials, i.e. the layered metal oxide material on the one hand and the polyanionic material on the other, are now spatially separated from each other in two layers.

[0025] In alternative embodiments, at least one positive electrode has an electrode material layer comprising both the layered metal oxide material and the polyanionic material. The two cathode materials are then contained within a single layer, namely the electrode material layer.

[0026] Preferably, the electrode material layer is designed such that the weight of the layered metal oxide material and the weight of the polyanionic material together constitute at least 90% of the weight of the electrode material layer. The remaining weight is typically contributed by a binder and / or a number of additives, for example, a conductivity additive.

[0027] Preferably, the first electrode material is in the form of first particles and the second electrode material is in the form of second particles. Furthermore, the electrode material layer preferably comprises or is formed by a mixture. This mixture typically includes first particles and second particles, and usually also a binder that advantageously binds the first and second particles together. According to at least one embodiment, the electrode material layer is then formed by a mixture of the three components: first particles, second particles, and binder.

[0028] If the first electrode material is in the form of first particles, designs are advantageous in which the first particles are in a particle size distribution with a percentile d50 whose value is in the range of 0.05 µm to 50 µm and especially in the range of 0.1 µm to 15 µm.

[0029] If the first electrode material is in the form of first particles, then configurations in which the first particles are made of the layered metal oxide material are also advantageous. Depending on the application, the first particles are either monocrystalline or polycrystalline, or a mixture of monocrystalline and polycrystalline particles. Alternatively, the first particles have a core made of the layered metal oxide material and a coating applied to the core, namely a first coating.

[0030] Depending on the application, the first coating may be designed, for example, as a coating that has one or more of the following materials or is made of one or more of the following materials: ZrO2, Nb2O3, WO3, Ta2O3, TnO2, TiO2, Al2O3, Na3PO4.

[0031] In other embodiments, the first coating alternatively or additionally features amorphous carbon or is designed as an amorphous carbon coating. In these cases, the weight of the amorphous carbon typically accounts for 0.5% to 5% of the total weight of the layered metal oxide material and the polyanionic material.

[0032] If the second electrode material is in the form of second particles, designs are advantageous in which the second particles are in a particle size distribution with a percentile d50 whose value lies in the range of 0.05 µm to 50 µm and especially in the range of 0.1 µm to 15 µm.

[0033] If the second electrode material is in the form of first particles, then designs in which the second particles are made of the polyanionic material are also advantageous. Depending on the application, the second particles can be monocrystalline, polycrystalline, or a mixture of monocrystalline and polycrystalline particles. Alternatively, the second particles can have a core made of the polyanionic material and a coating applied to the core, namely a second coating.

[0034] Depending on the application, the second coating may be designed, for example, as a coating that has one or more of the following materials or is made of one or more of the following materials: ZrO2, Nb2O5, WO3, Ta2O5, TnO2, TiO2, Al2O3, Na3PO4.

[0035] In other embodiments, the second coating alternatively or additionally comprises amorphous carbon or is designed as an amorphous carbon coating. In these cases, the weight of the amorphous carbon typically accounts for 0.5% to 5% of the total weight of the layered metal oxide material and the polyanionic material.

[0036] Preferred embodiments include those in which the electrode material layer is designed to have a thickness in the range of 40 µm to 100 µm, and in particular in the range of 55 µm to 85 µm.

[0037] Furthermore, design variants are advantageous in which the electrode material layer is designed in such a way that it has a density whose value is in the range of 1.5 g / cm³. 3 up to 4.5 g / cm³ 3 lies and especially in the range of 2.5 g / cm² 3 up to 4.2 g / cm³ 3. A corresponding density can be specifically determined, for example, by the mass loading, the thickness of the coating and / or the settings of the calender.

[0038] Furthermore, design variants are advantageous in which the cathode material(s) is / are designed in such a way that it / they have a mass-related specific surface area whose value is in the range of 0.1 m². 2 / g up to 200 m 2 / g lies, preferably in the range of 0.1 m 2 / g up to 30 m 2 / g and especially in the 0.1 m range 2 / g up to 10 m 2 / g or in the range of 0.4 m 2 / g up to 2 m 2 / g. A corresponding mass-related specific surface area can be specifically determined, for example, by selecting suitable particle sizes and particle size distributions.

[0039] Preferred designs also include those in which the electrode material layer is configured to have a porosity in the range of 0.20 to 0.45, and particularly in the range of 0.25 to 0.35. Such a porosity can be specifically determined, for example, by an appropriate degree of compaction.

[0040] The previously described electrode material layer is typically applied to a metal foil, for example, an aluminum foil. The metal foil then forms a current collector for the positive electrode, i.e., for at least one positive electrode. Here, the metal foil of the positive electrode is typically coated with the electrode material layer over a large area, with only a small section at the edge of the foil remaining free of the electrode material layer. This section usually serves as a contact point and is commonly referred to as a current collector tab.

[0041] Further advantages include embodiments in which the positive electrode, i.e., at least one positive electrode, has an insulating layer, namely an electrically insulating layer. This insulating layer is then preferably positioned in the transition region between the aforementioned partial area without an electrode material layer and the surface of the metal foil coated with an electrode material layer.

[0042] Depending on the application, the insulating layer has a thickness or value ranging from 0.1 µm to 20 µm, and especially from 1 µm to 10 µm.

[0043] Furthermore, the insulating layer preferably has an extent transverse to the boundary between the partial area without electrode material layer and the surface of the metal foil coated with electrode material layer, with a value in the range of 1 mm to 20 mm and particularly in the range of 2 mm to 8 mm.

[0044] Along the boundary between the partial area without electrode material layer and the surface of the metal foil coated with electrode material layer, the insulating layer preferably has an extent that corresponds approximately to the extent of the boundary.

[0045] Depending on the application, the insulating layer may also contain or be made of one of the following materials: polyvinylidene difluoride, polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyphenylene oxide, polyoxyethylene, polyethylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene difluoride-co-hexafluoropropylene, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene difluoride-co-chlorotrifluoroethylene, etc. Alternatively or additionally, the insulating layer may contain, for example, boehmite.

[0046] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the schematic drawings. These show: Fig. 1 in a side view a sodium-ion accumulator with an accumulator cell in which a positive electrode is arranged, Fig. 2 in a first side view the positive electrode, Fig. 3 in a second side view the positive electrode, and Fig. 4 in an enlarged, partial cross-sectional view, the positive electrode.

[0047] Corresponding parts are marked with the same reference symbols in all figures.

[0048] A sodium-ion accumulator 2, described below as an example, is in Fig. Figure 1 is shown in a highly simplified side view. It features, by way of example, seven accumulator cells 4, which in the exemplary embodiment are held in a support structure 6 and interconnected via a connecting device 8.

[0049] In the exemplary embodiment, the accumulator cells 4 of the sodium-ion accumulator 2 are all identically designed and each has a positive electrode 10, a negative electrode 12 and a separator 14. Fig. 1 The positive electrode 10, the negative electrode 12 and the separator 14 of one of the accumulator cells 4 are indicated by dashed frames as examples.

[0050] Furthermore, all accumulator cells 4 are filled with a liquid electrolyte, which is not explicitly shown. This liquid electrolyte is typically a sodium salt solution. For example, sodium hexafluorophosphate is used as the sodium salt, and a mixture of various organic carbonates such as propylene carbonate, ethylene carbonate, and / or diethyl carbonate is used as the solvent.

[0051] Since all the accumulator cells 4 in the exemplary embodiment are identical, all positive electrodes 10 are also identical. The same applies to all negative electrodes 12 and all separators 14. The separators 14 and the negative electrodes 12 are further configured in a known manner, which is why a more detailed description of these components is omitted. The configuration of the positive electrodes 10, however, is described in more detail below.

[0052] One of these positive electrodes 10 is in Fig. 2 in a first side view, in Fig. 3 in a second side view and in Fig. Figure 3 shows an enlarged, partial sectional view. It has a metal foil 18 coated with an electrode material layer 16, the metal foil 18 being made of aluminum in particular. Here, the metal foil 18 serves as a current collector for the positive electrode 10 and has an uncoated section that functions as a contact terminal 20 and is often referred to as a current collector tab.

[0053] The strength or thickness D ES The electrode material layer 16 has a value between 40 µm and 100 µm, depending on the application. Fig. 2 gives the ratio between the thickness D ESThe electrode material layer 16 and the thickness of the metal foil 18 are not necessarily exactly reflected. The thickness of the metal foil 18 preferably has a value between 6 µm and 14 µm, and particularly a value between 8 µm and 12 µm.

[0054] Independently of this, the electrode material layer 16 comprises a first electrode material 22 and a second electrode material 24. The first electrode material 22 is in the form of first particles P 22 and the second electrode material 24 in the form of second particles P 24 In the exemplary embodiment, the electrode material layer 16 is ultimately formed by a mixture of first particles P 22 and second particles P 24 and a binder 26, which binds the first particles P 22 and the second particles P 24 binds together. This is from Fig. 4 is visible.

[0055] Furthermore, the first particles P22, and thus the first electrode material 22, consist of a layered metal oxide material. According to at least one embodiment, the first particles P22 are formed from this layered metal oxide material. This embodiment is described in Fig. Figure 4 shows that, alternatively, the first particles P22 have a core made of the layered metal oxide material, wherein the core is coated with a coating, namely a first coating, for example with a coating of amorphous carbon. This embodiment is not explicitly shown.

[0056] The second particles P24, and thus the second electrode material 24, consist of a polyanionic material. According to at least one embodiment, the second particles P24 are made of this polyanionic material. This embodiment is described in Fig. Figure 4 shows that, alternatively, the second particles P24 have a core made of the polyanionic material, the core being coated with a second coating, for example, a coating of amorphous carbon. This embodiment is not explicitly shown.

[0057] In the exemplary embodiment, the electrode material layer 16 is further designed such that the weight of the layered metal oxide material and the weight of the polyanionic material together make up at least 90% of the weight of the electrode material layer 16, i.e., for example, 95%. Fig. However, point 4 does not necessarily reflect this exactly.

[0058] Furthermore, in the exemplary embodiment, the electrode material layer 16 is designed such that the weight of the layered metal oxide material constitutes at least 15% of the sum of the weight of the layered metal oxide material and the weight of the polyanionic material. Fig. However, point 4 does not necessarily reflect this exactly.

[0059] As from Fig. 2 and Fig. As can be seen from Figure 3, the positive electrode 10 also has an insulating layer 28, for example an insulating layer 28 made of polyvinylidene fluoride. The insulating layer 28 covers a transition area between the uncoated part of the metal foil 18, i.e., the contact terminal 20, and the coated part of the metal foil 18.

[0060] In the exemplary embodiment, the insulating layer 28 is approximately 10 µm thick. Fig. 2 gives the ratio between the thickness D ES the electrode material layer 16 and the thickness of the insulating layer 28 are not accurately represented.

[0061] The extension of the insulating layer 28 in the direction of a width B MF The metal foil 18 corresponds approximately to the width B. KA of the contact connection 20. The width B KAThe contact terminal 20 is typically at most half the size of the width B. MF the metal foil 18.

[0062] The extent H IS the insulating layer 28 in the direction of a height H MF The metal foil 18 has a value that is typically in the range of 2 mm to 8 mm. It is also usually the case that the height H KA of the contact connection 20 maximum 40% of the height H MF corresponds to the metal foil 18. Reference symbol list 2 sodium-ion batteries 4 accumulator cells 6 Supporting structure 8. Interlocking device 10 positive electrode 12 negative electrode 14 Separator 16 Electrode material layer 18 metal foil 20 Contact connection 22 first electrode material 24 second electrode material 26 binders 28 Insulating layer P 22 first particle P 24 second particle D ES Thickness of the electrode material layer B MF Width of the metal foil B KA Width of the contact connection H MF Height of the metal foil H KA Height of the contact connection H IS Height of the insulation layer QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Heimes, Heiner Hans; Kampker, Achim; Lienemann, Christoph; Locke, Marc; Offermanns (2018): Production process of a lithium-ion battery cell, VDMA Frankfurt, ISBN 978-3-947920-00-6

[0004] Heimes, Heiner Hans; Kampker, Achim; Kreisköther, Kim; Michaelis, Sarah; Rahimzei, Ehsan; vom Hemdt, Ansgar (2019): Component production of a lithium-ion battery cell, PEM of RWTH Aachen & VDMA, ISBN 978-3-947920-06-8

[0005]

Claims

[1] Sodium-ion accumulator (2) comprising an accumulator cell (4) in which at least one positive electrode (10) is arranged, wherein - which has at least one positive electrode (10) comprising a first electrode material (22) and a second electrode material (24), - the first electrode material (22) is a layered metal oxide material and - the second electrode material (24) is a polyanionic material. [2] Sodium-ion accumulator (2) according to claim 1, wherein the weight of the layered metal oxide material is at least 15% of the sum of the weight of the layered metal oxide material and the weight of the polyanionic material. [3] Sodium-ion battery (2) according to claim 1 or 2, wherein the at least one positive electrode (10) has an electrode material layer (16) and wherein the electrode material layer (16) comprises the layered metal oxide material and the polyanionic material. [4] Sodium-ion accumulator (2) according to 3, wherein the weight of the layered metal oxide material and the weight of the polyanionic material together constitute at least 90% of the weight of the electrode material layer (16). [5] Sodium-ion battery (2) according to claim 3 or 4, wherein the first electrode material (22) is in the form of first particles (P 22 ) and the second electrode material (24) in the form of second particles (P 24 ) is present, wherein the electrode material layer (16) is a mixture of first particles (P 22 ) as well as second particles (P 24 ) and wherein the mixture comprises a binder (26) which binds the first particles (P 22 ) and the second particles (P 24 ) ties them together. [6] Sodium-ion battery (2) according to claim 5, wherein the first particles (P 22) in a particle size distribution with a percentile d50 whose value lies in the range of 0.05 µm to 50 µm. [7] Sodium-ion battery (2) according to claim 5 or 6, wherein the first particles (P 22 ) have a core made of the layered metal oxide material and a first coating applied to the core. [8] Sodium-ion battery (2) according to one of claims 5 to 7, wherein the second particles (P 24 ) in a particle size distribution with a percentile d50 whose value lies in the range of 0.05 µm to 50 µm. [9] Sodium-ion battery (2) according to any one of claims 5 to 8, wherein the second particles (P 24 ) have a core made of the polyanionic material and a second coating applied to the core. [10] Method for manufacturing a sodium-ion battery (2) according to any one of the preceding claims.

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