Sodium-ion battery with sodium metal anode, and method for producing a sodium-ion battery

Abstract

A sodium-ion battery has a cathode, which comprises a cathode active material, and a sodium metal anode, the cathode active material being at least partially desodiated prior to the first discharging and / or charging process of the sodium-ion battery. A method for producing a sodium-ion battery is also disclosed.

Description

[0001] Sodium ion battery with sodium metal anode and method for producing a sodium ion battery

[0002] The invention relates to a sodium ion battery with a sodium metal anode and a method for producing a sodium ion battery.

[0003] In the following, the term "sodium-ion battery" is used synonymously for all commonly used terms in the prior art for sodium-containing galvanic elements and cells, such as sodium battery, sodium cell, sodium ion cell, sodium polymer cell, sodium ion polymer cell, and sodium ion accumulator. This particularly includes rechargeable batteries (secondary batteries). The terms "battery" and "electrochemical cell" are also used synonymously with the term "sodium ion battery." The sodium ion battery can also be a solid-state battery, for example, an inorganic, ceramic, gel-based, or polymer-based solid-state battery.

[0004] To meet the demand for electrochemical energy storage devices for stationary and mobile applications, lithium-free electrolytic cells and systems are increasingly coming into focus. Sodium-ion batteries are a fundamentally well-known alternative to electrochemical storage devices based on lithium-containing compounds.

[0005] A sodium-ion battery has at least two different electrodes: a positive electrode (cathode) and a negative electrode (anode). Each of these electrodes contains at least one active material, referred to as a cathode active material or anode active material, respectively, optionally together with additives such as electrode binders and electrical conductivity additives, such as conductive carbon black.

[0006] A general description of sodium-ion technology can be found in Chen et al.: "Readiness Level of Sodium-Ion Battery Technology: A Materials Review" (Adv. Sustainable Syst. 2018, 2, 1700153, doi: 10.1002 / adsu.201700153) and in Hasa et al.: "Challenges of today for Na-based batteries of the future: From materials to cell metrics" (Journal of Power Sources, 2021, 282, 22872, doi: 10.1016 / j.jpowsour.2020.228872). In sodium-ion batteries, both the cathode active material and the anode active material must be able to reversibly absorb or release sodium ions.

[0007] Sodium-ion batteries are currently assembled and manufactured in a completely uncharged state. This corresponds to a state in which the sodium ions are completely intercalated, i.e., stored, in the cathode, while the anode typically contains no active, i.e., reversibly cyclable, sodium ions.

[0008] Analogous to lithium-ion batteries with a metallic lithium anode, sodium-ion batteries are also known that use metallic sodium as the anode (also referred to as "sodium metal anode"). The cyclable sodium contained in the cathode active material after assembly can deposit on the sodium metal anode during charging and release again during discharging.

[0009] Typically, a thin layer of sodium metal is used on the anode, onto which the cyclable sodium of the cathode is deposited. This "excess" serves as a substrate for the metal deposition, but also improves the service life of such an electrochemical cell, since in the case of sodium-consuming side reactions, this excess can be used for cycling.

[0010] A disadvantage of such sodium-ion batteries is that the sodium metal anode used in the sodium-ion battery must have a thickness of approximately 10 μm. This is to minimize the excess sodium metal for cost reasons and to minimize the loss of energy density caused by the excess sodium metal. Rolling processes are typically used for this purpose. However, such rolling processes are complex and expensive, with the effort and costs increasing disproportionately with decreasing thickness.

[0011] In addition, the volume changes occurring due to the cyclable sodium deposited on the anode cannot always be sufficiently determined in advance, which can have a detrimental effect on the dimensional stability and service life of the sodium-ion battery due to unexpected expansion effects of the anode when charging the sodium-ion battery.

[0012] In state-of-the-art cell production, sodium-ion batteries are first assembled in an uncharged state and then formed, i.e., an initial charge and discharge cycle is performed. Formation is an extremely cost-intensive process, as it requires both specialized equipment and compliance with the highest safety standards, particularly with regard to fire protection.

[0013] The object of the invention is to provide a sodium-ion battery that has a long service life and can be produced cost-effectively. Furthermore, the object of the invention is to provide a cost-effective method by which such a sodium-ion battery can be produced.

[0014] The object is achieved according to the invention by a sodium ion battery having a cathode comprising a cathode active material and a sodium metal anode, wherein the cathode active material is at least partially deodiated before the first discharge and / or charging process of the sodium ion battery.

[0015] According to the invention, an at least partially deodiated active material has a degree of sodiation of less than 1, while a sodiated or pre-sodiated active material has a degree of sodiation of greater than 0.

[0016] The term "degree of sodiation" refers to the content of reversibly cyclable sodium, in the form of sodium ions, metallic sodium, and / or sodium alloys, per formula unit of the active material relative to the maximum content of reversibly cyclable sodium in the active material. In other words, the degree of sodiation is a measure of the percentage of the cyclable sodium specified by the formula unit of the active material that is intercalated or intercalated within the structure of the active material.

[0017] A degree of sodiation of 1 indicates a fully sodiated active material, while a degree of sodiation of 0 indicates a fully deodiated active material. It is understood that the amount of reversibly cyclable sodium depends on the voltage range in which the sodium-ion battery is to be operated. Accordingly, the formula unit of the active material may contain sodium that is not reversibly cyclable in the intended voltage range, even if it would be reversibly cyclable if the voltage range were expanded to comparatively higher voltages. In this case, the degree of sodiation refers only to the proportion of sodium that is reversibly cyclable in the selected voltage range.

[0018] In particular, the voltage range is limited by a maximum voltage of at most 5.0 V, preferably of at most 4.5 V, particularly preferably of at most 4.3 V.

[0019] For example, in a stoichiometric sodium vanadium phosphate fluoride (NVPF) with the formula unit NasV2(PO4)F3, the degree of sodiation is 1 and in the deodiated corresponding compound NaV2(PO4)Fs, the degree of sodiation is 0 when the voltage range has a maximum voltage of at most 4.3 V, in particular when the voltage range has a voltage in the range of 2.0 V to 4.3 V.

[0020] It is also possible to specify the sodiation degree as a percentage by multiplying the respective sodiation degree value by 100%. For example, a sodiation degree of 1 corresponds to a sodiation degree of 100%, a sodiation degree of 0.5 corresponds to a sodiation degree of 50%, and a sodiation degree of 0 corresponds to a sodiation degree of 0%.

[0021] According to the invention, the cathode active material is at least partially deodiated before the first discharge and / or charge process of the sodium ion battery. The term “deodiated” or “deodiation” indicates that, even before the first discharge and / or charge process of the sodium ion battery, sodium in the structure of the cathode active material has been at least partially removed compared to the fully sodiated cathode active material, i.e., a degree of sodification of less than 1 is present. The amount of cyclable sodium missing in the cathode active material due to the deodiation is correspondingly made available by the sodium metal anode, in which metallic sodium is present. Thus, even before the first discharge and / or charge process, the sodium ion battery according to the invention is at least partially charged, i.e., has a state of charge (SoC) of greater than 0%. This enables the sodium ion battery to be charged immediately after assembly orAssembly is ready for use.

[0022] The first discharge and / or charge process can therefore take place directly in the intended application, for example, at the end customer's site. Individual electrochemical cells can also be connected to form a battery module and then discharged and / or charged for the first time.

[0023] This eliminates the pre-charge and formation steps—the initial charging of the sodium-ion battery—during the manufacturing process, shortening production time. It also reduces power consumption during production, as well as the size and operation of the required production facilities.

[0024] A further advantage of the sodium-ion battery according to the invention is that the volume change occurring during charging of the sodium-ion battery compared to the volume during cell assembly can be minimized or even completely eliminated, since the amount of sodium corresponding to the extent of deodinization of the cathode active material is already provided by the installed sodium metal anode. This increases the dimensional stability and thus the reliability and service life of the sodium-ion battery.

[0025] In addition, the thickness of the sodium metal anode, which must be used and handled during the assembly of the sodium-ion battery, can be chosen to be greater than is the case when using a fully sodiated cathode active material, while maintaining the same energy content of the finished sodium-ion battery. This eliminates additional processing steps in the manufacture of the sodium metal anode, such as additional rolling steps, thereby reducing the manufacturing costs of the sodium-ion battery.

[0026] For example, the sodium metal anode has a thickness of at most 75 pm, preferably a thickness in the range of 20 to 50 pm. In this context, the thickness refers to the thickness of the sodium metal anode before the first discharge and / or charge process of the sodium-ion battery.

[0027] It is understood that when the sodium ion battery is charged to a SoC above the SoC obtained immediately after assembly of the sodium ion battery, the thickness of the sodium metal anode may further increase, and when the sodium ion battery is discharged to a SoC below the SoC obtained immediately after assembly of the sodium ion battery, the thickness of the sodium metal anode may further decrease.

[0028] The cathode active material may have a sodiation degree of at most 0.50, preferably at most 0.25, before the first discharge and / or charge process of the sodium-ion battery. As the sodiation degree of the cathode active material decreases, the SoC of the sodium-ion battery, which is obtained immediately after its assembly, increases, and a sodium metal anode with increasingly greater thickness can be used.

[0029] In one variant, the cathode active material is completely deodiated before the first discharge and / or charge cycle of the sodium-ion battery. In other words, apart from unavoidable impurities, no cyclable sodium is present within the cathode active material before the first discharge and / or charge cycle of the sodium-ion battery.

[0030] Thus, in this variant, the degree of sodiation of the cathode active material is zero before the first discharge and / or charge process, and the SoC of the sodium-ion battery is 100% immediately after assembly. This allows the use of a sodium metal anode whose thickness corresponds to the maximum thickness of the sodium-ion battery during operation, resulting in a particularly dimensionally stable sodium-ion battery.

[0031] Furthermore, such a design of the sodium-ion battery is particularly advantageous when the synthesis of a fully deodiated cathode active material is easier to implement than the synthesis of a partially deodiated cathode active material. Partially or fully deodiated cathode active materials are commercially available or can be obtained by electrochemical extraction of sodium from fully or partially sodiated cathode active materials.

[0032] Chemical extraction of sodium from fully or partially sodiated cathode active materials is also possible, in which the sodium is dissolved out using acids, for example sulfuric acid (H2SO4).

[0033] Another possibility is to synthesize formulations by solid-state synthesis that have the desired degree of sodiation a priori.

[0034] The cathode active material can be selected from the group consisting of Prussian Blue analogues, polyanionic cathode active materials, layered oxides and combinations thereof, preferably from the group consisting of Prussian Blue analogues, polyanionic cathode active materials and combinations thereof.

[0035] Prussian blue analogues and polyanionic cathode active materials are fully compatible with common electrode binders, electrolyte compositions and conductivity additives, such as conductive carbon black, as well as with common manufacturing processes for cathode active materials, such as mixing, coating, calendering, punching, cutting, winding, stacking and lamination processes.

[0036] Prussian Blue analogues (also referred to as "PBA") are known as active materials for sodium-ion batteries. The term "Prussian Blue analogues" refers to compounds whose crystal II structure is similar or essentially similar to that of Prussian Blue. For example, the structure of Prussian White Na2Fe[Fe(CN)e] is retained when deodiated analogues with the formula unit Na2-xFe[Fe(CNe)], where 0 < x < 2, are obtained by deodiation.

[0037] The type of Prussian blue analogue is fundamentally not further restricted, as long as at least partially deodiated forms of the respective cathode active material can be produced or produced. For the general state of the art on the use of Prussian blue analogues in sodium-ion batteries, reference is made to WO 2018 / 209653 A1 and WO 2022 / 121570 A1.

[0038] The Prussian Blue analogue is particularly selected from the group of compounds Nax M[M'(CN)6]i- y * z H2O, where 0 < x < 2, 0 < y < 1 and z > 0, and where M and M' are each selected from the group of transition metals, preferably from the group consisting of iron, manganese, chromium, nickel, cobalt and copper.

[0039] Preferably, M and M' are each selected from the group consisting of iron, manganese, and chromium. Accordingly, the Prussian Blue analogue is preferably free of nickel and cobalt.

[0040] Particularly preferred is the combination of M and M' (M / M') selected from the group Fe and Fe (Fe / Fe), Fe and Mn (Fe / Mn) and manganese and manganese (Mn / Mn).

[0041] Possible synthesis routes for the preparation of suitable cathode active materials based on Prussian blue analogues are described, for example, in Cheryldine QX Lim and Zhi-Kuang Tan: "Prussian White with Near-Maximum Specific Capacity in Sodium-ion Batteries" (ACS Appl. Energy Mater. 2021 , 4, pp. 6214-6220, doi: 10.1021 / acsaem.1c00987) and Brant et al.: "Selective Control of Composition in Prussian White for Enhanced Material Properties" (Chem. Mater. 2019, 31 , pp. 7203-7211 , doi:

[0042] 10.1021 / acs.chemmater.9b01494).

[0043] Polyanionic cathode active materials are also known as active materials for sodium-ion batteries. For the general state of the art on the use of polyanionic cathode active materials in sodium-ion batteries, see, for example, EP 3 933 997 A1 and Hasa et al.: "Challenges of today for Na-based batteries of the future: From materials to cell metrics" (Journal of Power Sources, 2021, 282, 22872, doi: 10.1016 / j.jpowsour.2020.228872).

[0044] The type of polyanionic cathode active material is fundamentally not further restricted, as long as at least partially deodiated forms of the respective cathode active material can be produced or produced. The polyanionic cathode active material is in particular selected from the group of phosphates, sulfates, silicates, and combinations thereof. Corresponding polyphosphates, polysulfates, and polysilicates are included in this selection.

[0045] The polyanionic cathode active material is preferably selected from compounds with a NASICON structure, tavorite structure, olivine structure, alluaudite structure, layered compounds, and combinations thereof. Such compounds are capable of reversibly absorbing and releasing sodium ions while essentially preserving the basic structure of the cathode active material. This reduces stress on the cathode material during charge and discharge cycles and thus increases the service life of the sodium-ion battery.

[0046] In this context, the term “layered compounds” does not include so-called “layered oxides” which contain oxygen anions and have the general formula Na x MO2, where M denotes a transition metal.

[0047] The polyanionic cathode active material may contain a transition metal selected from the group consisting of iron, manganese, vanadium, and combinations thereof.

[0048] For example, the polyanionic cathode active material is selected from the group of compounds Nai- x FePO4 (NFP), Naz- x Fe3(PO4)3, Naz-xFePzO?, Nai- x MnPO4, Naz-xMnPzO?, Naz-xMnPzO?, Naz- x MnPO4F, Na4- x .(Fe,Mn)3(PO4)2(P2O7), Na3- x V2(PO4)3 (NVP), Na3^V2(PO4)2F3 (NVPF), Na3^V2. y(VO) y (PO4)2F3-y, Naz- x Fe(SO4)3, Na2+2z- X “Fe2-z(SO4)3, Na2- x Mn2(SO4)3, Naz- x Fez(SiO4)3, Naz- x Mnz(SiO4)3, Naz- x FeSiO4, Naz- x MnSiO4 and combinations thereof, where 0 < x < 1, 0 < x' < 2, 0 < x“ < 3, 0 < x“' < 4, 0 < y < 3 and 0 < z < 2.

[0049] The layered oxide, also called “layered oxide”, can be a compound of the general formula Na x MOz, where M denotes a transition metal and 0 < x < 1.

[0050] For example, the layered oxide is selected from the group of compounds Na x MOz, where M is selected from the group consisting of manganese, iron, cobalt, nickel, aluminum, copper, titanium, zinc or combinations thereof and 0 < x < 1.

[0051] It is also possible that the cathode active material is doped, whereby the element used for doping partially replaces the transition metal.

[0052] For example, a Prussian Blue analogue in which M and M' are each Fe may be doped with an element selected from the group consisting of manganese, chromium, nickel, cobalt, and copper. In the case of a polyanionic cathode active material containing a transition metal selected from the group consisting of iron, manganese, vanadium, and combinations thereof, the cathode active material may be doped with an element selected from the group consisting of manganese, chromium, nickel, cobalt, copper, and combinations thereof.

[0053] Doping is understood to mean a content of the respective element in a proportion of not more than 5 percent by weight, based on the total weight of the polyanionic cathode active material, in particular in a proportion of not more than 1 percent by weight.

[0054] The cathode active material can have a particle size in the range of 0.1 to 35 pm, preferably from 1 to 20 pm. Such particle sizes are ideal for blending the cathode active material with other particles, especially conductive carbon black. This allows a homogeneous and highly compacted cathode coating composition to be obtained, which can be used in the cathode of a sodium-ion battery.

[0055] In addition to the cathode active material, the cathode may also comprise additives such as binders and electrical conductivity additives.

[0056] The binder (also referred to as electrode binder) is in particular selected from the group consisting of polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), cellulose, acrylates (for example polymethyl methacrylate), styrene-butadiene rubber (SBR), polyisobutene (PIB) and mixtures thereof. The electrical conductivity additive (also referred to as electrical conductivity additive) can be selected from the group consisting of conductive carbon black, carbon nanotubes (CNT), graphene, graphite, expanded graphite and carbon nanofibers, porous carbons (as described, for example, in EP 2 528 879 B1 and DE 10 2013 106 114 A1), gas-phase produced carbon nanofibers (also referred to as “VGCF” for English “vapour grown carbon fibers”) and combinations thereof.

[0057] The anode is a sodium metal anode in which metallic sodium serves as the active material and at the same time as the matrix to which the cyclable sodium binds.

[0058] The sodium metal anode may have at least one modification, for example a metal doping, a carbon additive or a stabilizing element such as a framework structure attached to the sodium metal anode.

[0059] However, the anode is in particular free of anode active materials other than metallic sodium, for example free of hard carbon, soft carbon, synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, tin, tin oxide, phosphorus, antimony, antimony oxide, Prussian blue analogues and mixtures thereof.

[0060] In one variant, the sodium-ion battery is a solid-state battery. A solid-state battery is characterized by the fact that it does not require a liquid electrolyte. This prevents unwanted side reactions between the electrolyte and the sodium metal anode and simplifies the design of the sodium-ion battery.

[0061] In order to provide sufficient ionic conductivity in the sodium-ion battery without a liquid electrolyte, the cathode may comprise a solid-state electrolyte, also referred to as a cathode solid electrolyte.

[0062] The choice of cathode solid electrolyte is fundamentally unrestricted, as long as it can provide sufficient sodium ion conductivity and can be processed with the other cathode components to form a homogeneous cathode coating mass. For example, the cathode solid electrolyte is a ceramic solid electrolyte, in particular a ß-aluminum oxide compound, a compound with a NASICON structure, a sodium rare earth silicate, a chalcogenide-based compound such as NasPSe4, or a combination thereof.

[0063] It is understood that compounds with NASICON structure, which can be used as cathode solid electrolyte, differ from polyanionic cathode active materials with NASICON structure.

[0064] In particular, compounds with a NASICON structure that are suitable as cathode solid electrolytes exhibit a higher conductivity for sodium ions than is the case for polyanionic cathode active materials with a NASICON structure. An example compound with a NASICON structure that can be used as a cathode solid electrolyte is described in Von Alpen et al.: "Compositional dependence of the electrochemical and structural parameters in the Nasicon system (Nai +x Si x Zr2P3.- x Oi2)'' (Solid State Ionics, Vol. 3-4, 1981 , pp. 215-218, doi: 10.1016 / 0167-2738(81)90085-0).

[0065] Between the cathode and the sodium metal anode of the sodium ion battery, there is a further solid electrolyte which also functions as a separator and is therefore also referred to as a separator solid electrolyte.

[0066] The separator solid electrolyte may be selected from the same compounds as the cathode solid electrolyte, whereby the separator solid electrolyte and the cathode solid electrolyte may be the same or different from each other.

[0067] The object of the invention is further achieved by a method for producing a sodium-ion battery, comprising the following steps: A cathode active material is provided, wherein the cathode active material is at least partially deodinated. A sodium metal anode is provided. The cathode active material is incorporated into a cathode, and the cathode and the sodium metal anode are assembled to form a sodium-ion battery.

[0068] The individual components of the sodium-ion battery produced by the process according to the invention are made, in particular, from the materials previously described for the sodium-ion battery according to the invention. Accordingly, the previously described sodium-ion battery according to the invention is obtainable, in particular, by the process according to the invention.

[0069] The at least partially deodiated cathode active material can be provided by solid-state synthesis or pre-sodium treatment of a fully deodiated cathode active material.

[0070] The pre-sodium treatment of the cathode active material can be carried out in particular by the techniques known in the prior art for the production of sodium-containing active materials.

[0071] For example, a mixture of a cathode active material with metallic sodium can be prepared. The mixture of cathode active material can be stored for a period of up to two weeks, preferably up to one week, particularly preferably up to five days. During this period, the sodium can be incorporated into the cathode active material, resulting in a pre-sodium-treated, i.e., partially deoxidized, cathode active material.

[0072] In one variant, the pre-sodium plating of the cathode active material can be carried out by mixing the cathode active material with a sodium precursor and subsequently converting the sodium precursor to metallic sodium.

[0073] In a further variant, the pre-sodium treatment of the cathode active material can be carried out by injecting sodium into the cathode active material.

[0074] In a further variant, the pre-sodium plating of the cathode active material can be carried out by vapor deposition of sodium onto the cathode active material.

[0075] The sodium metal anode can be adjusted to a maximum thickness of 75 pm before assembly, preferably to a thickness in the range of 20 to 50 pm. The selected thickness is particularly tailored to the deodinization of the cathode active material; with increasing deodination of the cathode active material, a greater thickness of the sodium metal anode can be used. The thickness of the sodium metal anode can be adjusted by rolling, compression, sputtering, or evaporation using physical vapor deposition.

[0076] Preferably, the sodium metal anode is rolled to the desired thickness before assembly. Rolling processes are comparatively cost-effective, and the necessary rolling mills have been proven in battery production facilities.

[0077] After the assembly step, before a first discharge and / or charge process of the sodium-ion battery, the sodium-ion battery can have a state-of-charge (SoC) of at least 50%, preferably at least 75%. Accordingly, the manufactured sodium-ion battery is immediately suitable for use in the intended application scenario.

[0078] In one variant, the sodium-ion battery is discharged to a target state of charge (target SoC) after assembly. The target SoC is selected in particular such that the sodium-ion battery has a desired state of charge for transporting the sodium-ion battery.

[0079] The electrical energy generated when discharging the sodium-ion battery can be used to operate the production facility used to manufacture the sodium-ion battery and / or fed into a power grid. This allows the energy requirements of the production facility to be optimized.

[0080] It is also possible that the discharging of the sodium-ion battery is decoupled from the assembly step in order to use the electrical energy generated during the discharging of the sodium-ion battery at a time when there is an increased demand for energy from this source, for example at a time when electrical energy from renewable sources is only available to a limited extent, for example during a period of darkness or at night.

[0081] Further advantages and features of the invention will become apparent from the following description and examples, which are not to be understood in a limiting sense.

[0082] Table 1 lists the substances and materials used in the examples. Table 1: Substances and materials used.

[0083] Example 1 (Reference Example) A mixture of 75 wt.% Prussian White (Na2Fe[Fe(CN)e]), 3.5 wt.% PVdF, 3.5 wt.% conductive carbon black, and 18 wt.% solid electrolyte is suspended in NMP at 20 °C using a high-shear dissolver mixer. A homogeneous cathode coating mass is obtained, which is doctored onto an aluminum carrier foil rolled to a thickness of 15 μm. After removing the NMP, a composite cathode film with a basis weight of 24.4 mg / cm is obtained. 2 .

[0084] As anode, a 10 pm thick sodium layer is applied to a 15 pm thick rolled aluminum carrier foil, for example by roll bonding.

[0085] The cathode with the cathode film is combined with the anode and a separator solid electrolyte to form an electrochemical cell with 25 cm 2The active electrode surface is packaged and sealed in a high-quality aluminum composite foil (thickness: 0.12 mm). The result is a pouch cell with external dimensions of approximately 0.5 mm x 6.4 mm x 4.3 mm.

[0086] The cell is first charged to 3.8 V (C / 10) and then discharged with C / 10 to 2.2 V.

[0087] The capacity of the first charge is 70.6 mAh and the capacity of the first discharge is 68.5 mAh. This results in a formation efficiency of approximately 97% for the entire cell, which corresponds to a formation loss of approximately 3%.

[0088] Example 2 (Sodium ion battery according to the invention)

[0089] A mixture of identical substances and amounts of substances as in Example 1, but with fully deodiated Prussian White (Fe[Fe(CN)e]) instead of the fully sodiated Prussian White from Example 1, is suspended in NMP at 20 °C using a high-shear dissolver mixer. This results in a homogeneous cathode coating mass, which is doctored onto an aluminum collector carrier foil rolled to a thickness of 15 μm. After removing the NMP, a cathode film with a basis weight of 21.7 mg / cm is obtained. 2 . The reduced basis weight results from the completely deodiated Prussian White, which does not contain the mass of sodium that is not present in completely sodiated Prussian White, for identical amounts of substance.

[0090] The cathode active material used thus has a sodiation degree of

[0091] 0. As anode, a 35 pm thick sodium layer is applied to a 15 pm thick rolled aluminum carrier foil, for example by roll bonding.

[0092] The cathode with the cathode film is combined with the anode and a separator solid electrolyte to form an electrochemical cell with 25 cm 2 The active electrode surface is packaged and sealed in a high-quality aluminum composite foil (thickness: 0.12 mm). The result is a pouch cell with external dimensions of approximately 0.5 mm x 6.4 mm x 4.3 mm.

[0093] After final sealing, the cell according to the invention has an open voltage of approximately 3.25 to 3.5 V, resulting from the potential difference between the cathode with deodized cathode active material and the sodium metal anode. The nominal capacity of the sodium-ion battery is 68.5 mAh, and the sodium-ion battery has a state-of-charge (SoC) of 100% immediately after production.

[0094] The sodium-ion battery according to the invention has an identical nominal capacity to the sodium-ion battery of the reference example. Since a cathode with deodidified cathode active material is used to manufacture the sodium-ion battery according to the invention, the sodium-ion battery according to the invention can be used immediately after the assembly step.

[0095] In addition, a 35 pm thick sodium foil can be used in the anode, which is easier and cheaper to produce in rolling processes, since fewer rolling steps are necessary to obtain a sodium foil of such a thickness than is the case for a 10 pm thick sodium foil.

[0096] Furthermore, the sodium-ion battery is manufactured with the electrodes and the entire sodium-ion battery fully expanded. This means that the sodium-ion battery already has its external dimensions in a fully charged state, thus avoiding mechanical stresses due to subsequent expansion of the anode during the charging process.

[0097] In addition, after assembly, the sodium-ion battery can be at least partially discharged, thereby reducing the SoC to a target SoC to enable particularly safe transport of the sodium-ion battery. The electrical energy discharged in this process can be sustainably used directly in the cell factory or fed into the power grid.

Claims

Patent claims 1. A sodium ion battery having a cathode comprising a cathode active material and a sodium metal anode, wherein the cathode active material is at least partially deodiated before the first discharge and / or charge process of the sodium ion battery.

2. Sodium ion battery according to claim 1, wherein the sodium metal anode has a thickness of at most 75 pm, preferably a thickness in the range of 20 to 50 pm.

3. Sodium ion battery according to claim 1 or 2, wherein the cathode active material has a degree of sodiation of at most 0.50, preferably of at most 0.25, before the first discharge and / or charge process of the sodium ion battery.

4. A sodium ion battery according to claim 3, wherein the cathode active material is completely deodiated before the first discharge and / or charge process of the sodium ion battery.

5. A sodium ion battery according to any one of the preceding claims, wherein the cathode active material is selected from the group consisting of Prussian blue analogues, polyanionic cathode active materials, layered oxides and combinations thereof.

6. A sodium ion battery according to any one of the preceding claims, wherein the sodium ion battery is a solid-state battery.

7. A method for producing a sodium ion battery, comprising the following steps: - providing a cathode active material, wherein the cathode active material is at least partially deodinated; - Providing a sodium metal anode; - incorporating the cathode active material into a cathode; and - Assembling the cathode and the sodium metal anode to form a sodium ion battery.

8. The method according to claim 7, wherein the sodium metal anode is adjusted to a thickness of at most 50 pm before fabrication, preferably to a thickness in the range of 40 to 50 pm.

9. The method according to claim 7 or 8, wherein the sodium ion battery has a state of charge, SoC, of ​​at least 50%, preferably of at least 75%, immediately after the assembly step, before a first discharge and / or charge process of the sodium ion battery.

10. The method according to any one of claims 7 to 9, wherein the sodium ion battery is discharged to a target state of charge, target SoC, after assembly.

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