RECHARGEABLE BATTERY CELL

Description

[0001] The invention relates to a rechargeable battery cell with an SO2-based electrolyte.

[0002] Rechargeable battery cells are of great importance in many technical fields. They are frequently used in applications requiring only small rechargeable battery cells with relatively low currents, such as in mobile phones. However, there is also a significant demand for larger rechargeable battery cells for high-energy applications, with mass energy storage in the form of battery cells being of particular importance for the electric propulsion of vehicles.

[0003] A key requirement for such rechargeable battery cells is high energy density. This means that the rechargeable battery cell should contain as much electrical energy as possible per unit of weight and volume. Lithium has proven particularly advantageous as an active metal for this purpose. Rechargeable battery cells containing lithium as the active metal are also known as lithium-ion cells. The energy density of these lithium-ion cells can be increased either by increasing the specific capacitance of the electrodes or by increasing the cell voltage. Both the positive and negative electrodes of lithium-ion cells are designed as insertion electrodes. For the purposes of this invention, the term "insertion electrode" refers to electrodes that have a crystal structure into which ions of the active metal can be inserted and removed during operation of the lithium-ion cell.The active metal of a rechargeable battery cell is the metal whose ions migrate within the electrolyte to the negative or positive electrode during charging or discharging, where they participate in electrochemical processes. In the case of an insertion electrode, this means that the electrode processes can occur not only on the surface of the electrodes but also within the crystal structure. During charging of the lithium-ion cell, the ions of the active metal are extracted from the positive electrode and inserted into the negative electrode. The reverse process occurs during discharging. These electrochemical processes lead directly or indirectly to the release of electrons into the external circuit or the absorption of electrons from the external circuit.To enable electrons to be released into or absorbed from the external circuit, the positive and negative electrodes of the lithium-ion cell each have a leakage element. These leakage elements are essential components of the positive and negative electrodes. The electrons (e-) released in the electrode reactions of the first electrode are released into the external circuit via its leakage element. The electrons required for the electrode reactions of the second electrode are supplied from the external circuit by the leakage element of this electrode. Good electronic conductivity of both leakage elements is a prerequisite for the high current-carrying capacity of the battery cell. The leakage elements can be, for example, planar in the form of a metal sheet or three-dimensional in the form of a porous metal foam.The active materials of the negative or positive electrode are embedded in the metal foam or applied to the planar metal sheet of the grounding element. The active material in the metal foam and the coating of the planar metal sheet with the active material are porous, allowing the electrolyte to penetrate the respective porous structure and thus come into contact with the grounding element. During the charging and discharging of a battery cell, a potential difference is established between the electrodes. Reactions of the grounding element with the active electrode materials or the electrolyte can be promoted by this potential difference. Therefore, the grounding element material must be inert to both the active electrode materials and the electrolyte within the relevant potential range, without any undesirable side reactions occurring.Therefore, when selecting a suitable discharge element, the electrolyte used and the expected potential range must be taken into account. In the following text, the terms "discharge element," "discharge arrester," and "current collector" are synonymous.

[0004] The electrolyte is also a crucial functional element of every rechargeable battery cell. It usually contains a solvent or a solvent mixture and at least one conducting salt. Solid electrolytes or ionic liquids, for example, contain no solvent, only the conducting salt. The electrolyte is in contact with the positive and negative electrodes of the battery cell. At least one ion of the conducting salt (anion or cation) is mobile enough in the electrolyte to allow charge transport between the electrodes via ionic conduction, which is essential for the function of the rechargeable battery cell. Above a certain upper cell voltage, the electrolyte undergoes oxidative electrochemical decomposition. This process often leads to the irreversible destruction of electrolyte components and thus to the failure of the rechargeable battery cell.Reductive processes can also decompose the electrolyte below a certain lower cell voltage. To prevent these processes, the positive and negative electrodes are selected such that the cell voltage is below or above the electrolyte's decomposition voltage, respectively. The electrolyte thus determines the voltage window within which a rechargeable battery cell can be operated reversibly, i.e., repeatedly charged and discharged.

[0005] Lithium-ion cells known from the prior art contain an electrolyte consisting of an organic solvent or solvent mixture and a conducting salt dissolved therein. The conducting salt is a lithium salt, such as lithium hexafluorophosphate (LiPF₆). The solvent mixture may contain, for example, ethylene carbonate. The electrolyte LP57, which has the composition 1 M LiPF₆ in EC:EMC 3:7, is an example of such an electrolyte. Due to the organic solvent or solvent mixture, such lithium-ion cells are also referred to as organic lithium-ion cells.

[0006] Besides lithium hexafluorophosphate (LiPF₆), which is frequently used as a conducting salt in the prior art, other conducting salts for organic lithium-ion cells are also described. For example, document JP 4 306858 B2 (hereinafter referred to as [V1]) describes conducting salts in the form of tetraalkoxy or tetraaryloxyborate salts, which may be fluorinated or partially fluorinated. JP 2001 143750 A (hereinafter referred to as [V2]) reports on fluorinated or partially fluorinated tetraalkoxyborate salts and tetraalkoxyaluminate salts as conducting salts. In both documents [V1] and [V2], the described conducting salts are dissolved in organic solvents or solvent mixtures and used in organic lithium-ion cells.

[0007] It has long been known that the unintentional overcharging of organic lithium-ion cells leads to the irreversible decomposition of electrolyte components. This involves the oxidative decomposition of the organic solvent and / or the conducting salt at the surface of the positive electrode. The heat of reaction generated during this decomposition and the resulting gaseous products are responsible for the subsequent "thermal runaway" and the resulting destruction of the organic lithium-ion cell. The vast majority of charging protocols for these organic lithium-ion cells use the cell voltage as an indicator of the end of charging. Accidents caused by thermal runaway are particularly likely when using multi-cell battery packs in which several organic lithium-ion cells with different capacities are connected in series.

[0008] Therefore, organic lithium-ion cells are problematic with regard to their stability and long-term operational reliability. Safety risks are also caused, in particular, by the flammability of the organic solvent or solvent mixture. If an organic lithium-ion cell catches fire or even explodes, the organic solvent in the electrolyte forms a flammable material. To avoid such safety risks, additional measures must be taken. These measures include, in particular, very precise control of the charging and discharging processes of the organic lithium-ion cell and an optimized battery design. Furthermore, the organic lithium-ion cell contains components that can melt in the event of an unintended temperature increase, flooding the cell with molten plastic. This prevents further uncontrolled temperature increases.However, these measures lead to increased production costs in the manufacture of the organic lithium-ion cell, as well as increased volume and weight. Furthermore, these measures reduce the energy density of the organic lithium-ion cell.

[0009] A prior art advancement involves the use of a sulfur dioxide (SO₂)-based electrolyte instead of an organic electrolyte for rechargeable battery cells. Rechargeable battery cells containing an SO₂-based electrolyte exhibit, among other things, high ionic conductivity. For the purposes of the present invention, the term "SO₂-based electrolyte" refers to an electrolyte that contains SO₂ not only as an additive in low concentration, but in which the mobility of the ions of the conducting salt contained in the electrolyte, which facilitates charge transport, is at least partially, largely, or even completely ensured by SO₂. The SO₂ thus serves as a solvent for the conducting salt. The conducting salt is, for example,Often, lithium tetrachloroaluminate (LiAlCl₄) is used, which forms a liquid solvate complex with gaseous SO₂, binding the SO₂ and significantly reducing its vapor pressure compared to pure SO₂. This results in electrolytes with a low vapor pressure. Such SO₂-based electrolytes have the advantage of being non-flammable compared to the previously described organic electrolytes. Safety risks associated with the flammability of the electrolyte can thus be eliminated. Examples of SO₂-based electrolytes are disclosed in WO 2020 / 013667 A1 and WO 2021 / 006704 A1. WO 2020 / 013667 A1 describes a rechargeable lithium battery with a positive electrode, a negative electrode, an intermediate separator, and an SO₂-based electrolyte in combination with a negative electrode where the carbon material is coated with titanium oxide.The experiments use a LiAlCl 4 * 3 SO 2 electrolyte.

[0010] WO 2021 / 006704 A1 discloses an SO₂-based electrolyte comprising two different conducting salts of the general formula MNX-n(SO₂). (where M = alkali metal; N = at least one metal selected from the alkali metals, transition metals, or post-transition metals; X = halogen). An SO₂-based electrolyte with the compositions LiAlCl₄*3SO₂ and NaAlCl₄*2SO₂ is described.

[0011] For example, EP 2 534 725 B1 (hereinafter referred to as [V3]) discloses a rechargeable battery cell with an SO 2-based electrolyte, which preferably contains a tetrahaloaluminate, in particular LiAlCl 4, as the conducting salt.

[0012] Regarding current collectors, [V3] reports that "nickel or a nickel alloy is frequently used for the current collectors to and from the electrodes." The document further states that nickel foam is commonly used as a current collector for the electrodes.

[0013] US patent 2004 / 0157129 A1 (hereinafter referred to as [V4]) also discloses a rechargeable battery cell with an SO₂-based electrolyte. The inventors of [V4] found that undesirable reactions occur between the leakage element and the SO₂-based electrolyte, particularly with chloride-containing conductive salts such as LiAlCl₄. This problem is especially prevalent in battery cells that reach very high cell voltages (more than 4 volts) during charging. The problem is solved by a battery cell in which an electronically conductive leakage element of at least one electrode contains a surface layer containing a chromium alloy with another metal and / or a protective metal as a reaction shielding material to protect the leakage element against undesired reactions.

[0014] EP 2534719 B1 (hereinafter referred to as [V5]) also discloses an SO₂-based electrolyte with, among other things, LiAlCl₄ as a conducting salt. This LiAlCl₄ forms complexes with SO₂, for example, of the formula LiAlCl₄ * 1.5 mol SO₂ or LiAlCl₄ * 6 mol SO₂. Lithium iron phosphate (LiFePO₄) is used as the positive electrode in [V5]. LiFePO₄ has a lower charging voltage (3.7 V) compared to LiCoO₂ (4.2 V). The problem of undesirable reactions of the discharge element does not occur in this rechargeable battery cell, as upper potentials of 4.1 volts are not reached.

[0015] A further development of the [V5] with respect to the positive electrode is described in EP 3 734 724 A1. Improved results are achieved in the same SO₂-based electrolyte using sulfur-doped lithium iron phosphate. Here, too, the problem of undesirable reactions of the leakage element does not occur, since maximum potentials of 3.7 volts are reached.

[0016] Another problem with SO2-based electrolytes is that many conducting salts, especially those known for organic lithium-ion cells, are not soluble in SO2.

[0017] US patent 4,510,220 reports that organic co-solvents are used in SO₂-based electrolytes to dissolve conductive salts that are otherwise insoluble in SO₂. However, organic materials tend to participate in irreversible reactions. SO₂-based electrolytes without organic co-solvents require the use of electrolyte salts that are soluble in SO₂, which is generally a poor solvent, and also provide a usable conductive electrolyte solution. Only salts such as tetrachloroaluminates, tetrachlorogallates, tetrachloroindates, and clovoborates of alkali or alkaline earth metals have proven useful in SO₂ (although clovoborates are very expensive). The focus of this US patent US 4,510,220 is on a battery cell with a PbS 2 cathode and an SO 2-based electrolyte of the composition LiAlCl 4 *3SO 2 or LiGaCl 4 *3SO 2 .

[0018] Within the scope of the invention, measurements of the solubilities of various conducting salts in SO₂ were carried out. Table 2 shows the results. Table 2: Solubilities of various conducting salts in SO₂ Conductive salt Solubility / mol / L in SO₂ Conductive salt Solubility / mol / L in SO₂ LiF 2,1·10 -3< LiPF 6 1,5·10 -2< LiBr 4.9·10 -3< LiSbF 6 2.8·10 -4< Li 2 SO 4 2.7·10 -4< LiBF 2 (C 2 O 4 ) 1,4·10 -4< LiB(C 2 O 4 ) 2 3.2·10 -4< CF3SO2 NLiSO2 CF3 1,5·10 -2< Li 3 PO 4 - LiBO 2 2.6·10 -4< Li 3 AlF 6 2,3·10 -3< LiAlO 2 4.3·10 -4< LiBF 4 1.7·10 -3< LiCF 3 SO 3 6.3·10 -4< LiAsF 6 1,4·10 -3<

[0019] Measurements showed that SO₂ is a poor solvent for many conducting salts, such as lithium fluoride (LiF), lithium bromide (LiBr), lithium sulfate (Li₂SO₄), lithium bis(o-xalato)borate (LiBOB), lithium hexafluoroarsenate (LiAsF₆), lithium tetrafluoroborate (LiBF₄), trilithium hexafluoroaluminate (Li₃AlF₆), lithium hexafluoroantimonate (LiSbF₆), lithium difluoro(oxalato)borate (LiBF₂C₂O₄), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium metaborate (LiBO₂), lithium aluminate (LiAlO₂), lithium triflate (LiCF₃SO₃), and lithium chlorosulfonate (LiSO₃Cl). The solubilities of these conducting salts in SO₂ are approximately 10⁻² < -10⁻⁴ < mol / L (see Table 2). At these low salt concentrations, it can be assumed that only very low conductivities are present, which are insufficient for the effective operation of a rechargeable battery cell.

[0020] In order to further improve the application possibilities and properties of rechargeable battery cells containing an SO2-based electrolyte, the present invention is based on the objective of providing a rechargeable battery cell with an SO2-based electrolyte which, compared to rechargeable battery cells known from the prior art, The electrodes have inert leakage elements that do not react with the SO₂-based electrolyte and are stable even at higher charging potentials; the electrodes have leakage elements that neither dissolve at high potentials nor accelerate oxidative electrolyte decomposition. Furthermore, reactions leading to the formation of the cover layer must not be impaired. It has a wide electrochemical window, so that no oxidative electrolyte decomposition occurs at the positive electrode; it has a stable cover layer on the negative electrode, whereby the cover layer capacitance should be low and no further reductive electrolyte decomposition occurs at the negative electrode during subsequent operation.contains an SO₂-based electrolyte that exhibits good solubility for conducting salts and is therefore a good ion conductor and electronic insulator, thus facilitating ion transport and minimizing self-discharge; contains an SO₂-based electrolyte that is inert to other components of the rechargeable battery cell, such as separators, electrode materials, and cell packaging materials, and is robust against various forms of abuse, such as electrical, mechanical, or thermal stress; contains an SO₂-based electrolyte that exhibits increased stability against residual amounts of water in the cell components of rechargeable battery cells; exhibits improved electrical performance, in particular high energy density; and exhibits improved overcharge and deep discharge capabilities and lower self-discharge.an increased lifespan, in particular a high number of usable charge and discharge cycles, and the lowest possible price and high availability. This is of particular importance for large batteries or batteries with widespread use.

[0021] Such rechargeable battery cells should in particular exhibit very good electrical energy and performance data, high operational reliability and service life, especially a high number of usable charge and discharge cycles, without the electrolyte decomposing during operation of the rechargeable battery cell.

[0022] This problem is solved by a rechargeable battery cell with the features of claim 1. Claims 2 to 25 describe advantageous further developments of the rechargeable battery cell according to the invention.

[0023] A rechargeable battery cell according to the invention comprises an active metal, at least one positive electrode with a leakage element, at least one negative electrode with a leakage element, a casing, and an electrolyte. The leakage element of the positive electrode and the leakage element of the negative electrode are independently formed from a material selected from the group consisting of aluminum and copper. The electrolyte is SO₂-based and contains at least one first conducting salt. This first conducting salt has the formula (I) In formula (I), M is a metal selected from the group consisting of alkali metals, alkaline earth metals, group 12 metals of the periodic table, and aluminum. x is an integer from 1 to 3. The substituents R<1, R<2, R<3, and R<4 are independently selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C40 cycloalkyl, C6-C14 aryl, and C5-C14 heteroaryl. The central atom Z is either aluminum or boron.

[0024] In the context of the present invention, the term "lead element" refers to an electronically conductive element that serves to enable the necessary electronically conductive connection of an active material of the respective electrode to the external circuit. For this purpose, the respective lead element is in electronically conductive contact with the active material involved in the electrode reaction of the respective electrode.

[0025] The SO₂-based electrolyte used in the rechargeable battery cell according to the invention contains SO₂ not only as an additive in low concentrations, but in concentrations at which the mobility of the ions of the first conducting salt, which is contained in the electrolyte and effects charge transport, is at least partially, largely, or even completely ensured by the SO₂. The first conducting salt is dissolved in the electrolyte and exhibits very good solubility therein. It can form a liquid solvate complex with the gaseous SO₂, in which the SO₂ is bound. In this case, the vapor pressure of the liquid solvate complex drops significantly compared to pure SO₂, resulting in electrolytes with a low vapor pressure.However, it is also within the scope of the invention that, depending on the chemical structure of the first conducting salt according to formula (I), no reduction in vapor pressure can occur during the production of the electrolyte according to the invention. In the latter case, it is preferred that the production of the electrolyte according to the invention is carried out at low temperature or under pressure. The electrolyte can also contain several conducting salts of formula (I) which differ from one another in their chemical structure.

[0026] For the purposes of the present invention, the term "C1-C10 alkyl" includes linear or branched saturated hydrocarbon groups with one to ten carbon atoms. This includes, in particular, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, 2,2-dimethylpropyl, n-hexyl, iso-hexyl, 2-ethylhexyl, n-heptyl, iso-heptyl, n-octyl, iso-octyl, n-nonyl, n-decyl, and the like.

[0027] For the purposes of the present invention, the term "C2-C40 alkenyl" encompasses unsaturated linear or branched hydrocarbon groups with two to ten carbon atoms, wherein the hydrocarbon groups have at least one C-C double bond. This includes, in particular, ethenyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, iso-butenyl, 1-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 1-nonenyl, 1-decenyl, and the like.

[0028] The term "C2-C10 alkynyl" as used in the present invention comprises unsaturated linear or branched hydrocarbon groups with two to ten carbon atoms, wherein the hydrocarbon groups have at least one C-C triple bond. This includes, in particular, ethynyl, 1-propynyl, 2-propynyl, 1-n-butynyl, 2-n-butynyl, isobutynyl, 1-pentynyl, 1-hexynyl, 1-octynyl, 1-nonynyl, 1-decinyl, and the like. The term "C3-C10 cycloalkyl" as used in the present invention comprises cyclic, saturated hydrocarbon groups with three to ten carbon atoms. This includes, in particular, cyclopropyl, cyclobutyl, cyclopentyl, cycloheptyl, cyclohexyl, cycloononyl, and cyclodecanyl.

[0029] For the purposes of the present invention, the term "C6-C14 aryl" encompasses aromatic hydrocarbon groups with six to fourteen ring-shaped carbon atoms. This includes, in particular, phenyl (C6H5 group), naphthyl (C10H7 group), and anthracyl (C14H9 group).

[0030] For the purposes of the present invention, the term "C5-C14 heteroaryl" encompasses aromatic hydrocarbon groups with five to fourteen ring-shaped hydrocarbon atoms, in which at least one hydrocarbon atom is replaced or exchanged by a nitrogen, oxygen, or sulfur atom. This includes, in particular, pyrrolyl, furanyl, thiophenyl, pyrridinyl, pyranyl, thiopyranyl, and the like. All of the aforementioned hydrocarbon groups are bonded via the oxygen atom to the central atom according to formula (I).

[0031] A rechargeable battery cell with such an electrolyte has the advantage over rechargeable battery cells with electrolytes known from the prior art that the first conducting salt contained therein exhibits higher oxidation stability and consequently shows essentially no decomposition at higher cell voltages. This electrolyte is oxidation-stable preferably at least up to an upper potential of 4.0 volts, more preferably at least up to an upper potential of 4.2 volts, more preferably at least up to an upper potential of 4.4 volts, more preferably at least up to an upper potential of 4.6 volts, more preferably at least up to an upper potential of 4.8 volts, and particularly preferably at least up to an upper potential of 5.0 volts.Thus, when using such an electrolyte in a rechargeable battery cell, there is only minimal or even no electrolyte degradation within the operating potentials, i.e., in the range between the charging cut-off voltage and the discharging cut-off voltage of both electrodes of the rechargeable battery cell. As a result, rechargeable battery cells according to the invention can have a charging cut-off voltage of at least 4.0 volts, more preferably at least 4.4 volts, more preferably at least 4.8 volts, more preferably at least 5.2 volts, more preferably at least 5.6 volts, and particularly preferably at least 6.0 volts. The service life of the rechargeable battery cell containing this electrolyte is significantly extended compared to rechargeable battery cells containing electrolytes known from the prior art.

[0032] Furthermore, a rechargeable battery cell with such an electrolyte is also resistant to low temperatures. At a temperature of, for example, -40°C, 61% of the charged capacity can still be discharged. The conductivity of the electrolyte at low temperatures is sufficient for the operation of a battery cell. Additionally, a rechargeable battery cell with such an electrolyte exhibits increased stability with respect to residual amounts of water. If small residual amounts of water (in the ppm range) remain in the electrolyte, the electrolyte, or rather the first conducting salt, forms hydrolysis products with the water, which are significantly less aggressive towards the cell components compared to prior art SO₂-based electrolytes. Therefore, the absence of water in the electrolyte plays a less significant role compared to prior art SO₂-based electrolytes.These advantages of the electrolyte according to the invention outweigh the disadvantage arising from the fact that the first conducting salt according to formula (I) has a significantly larger anion size compared to conducting salts known from the prior art. This larger anion size leads to a lower conductivity of the first conducting salt according to formula (I) compared to the conductivity of LiAlCl₄. Conductors of the positive and negative electrodes

[0033] Advantageous further developments of the rechargeable battery cell according to the invention are described below with regard to the discharge element of the positive electrode and the discharge element of the negative electrode: According to the invention, both the positive electrode and the negative electrode have a discharge element. These discharge elements serve to enable the necessary electronically conductive connection of the active material of the respective electrode to the external circuit. For this purpose, the discharge element is in contact with the active material involved in the electrode reaction of the respective electrode. As already mentioned, according to the invention, the discharge element of the positive electrode and the discharge element of the negative electrode are formed independently of one another from a material selected from the group consisting of aluminum and copper.An advantageous embodiment of the rechargeable battery cell according to the invention provides that the discharge element of the positive electrode is made of aluminum. In a further advantageous embodiment of the rechargeable battery cell according to the invention, the discharge element of the negative electrode is made of copper. The discharge element of the positive electrode and / or the discharge element of the negative electrode can be formed in one piece or in multiple parts.

[0034] The positive electrode and / or the negative electrode can be planar, in the form of a thin metal sheet or foil. The thin metal sheet or foil can have a perforated or mesh-like structure. Alternatively, the planar electrode can be made of a metal-coated plastic film. This metal coating preferably has a thickness in the range of 0.1 µm to 20 µm. The active material of the respective electrode is preferably applied to the surface of the thin metal sheet, foil, or plastic film. The active material can be applied to the front and / or back of the planar electrode. Such planar electrodes preferably have a thickness in the range of 0.5 µm to 50 µm, and particularly preferably in the range of 1 µm to 20 µm.When using planar conductive elements, the respective electrode can have a total thickness of at least 20 µm, preferably at least 40 µm, and particularly preferably at least 60 µm. The maximum thickness is preferably at most 300 µm, more preferably at most 150 µm, and particularly preferably at most 100 µm.

[0035] The area-specific capacitance of the positive electrode and / or the negative electrode, based on the coating of one side of the respective discharge element, preferably has at least 0.5 mAh / cm² when using the planar discharge element, with the following values ​​being further preferred in this order: 1 mAh / cm², 3 mAh / cm², 5 mAh / cm², 10 mAh / cm², 15 mAh / cm², 20 mAh / cm².

[0036] If the conducting element is planar in the form of a thin metal sheet, a thin metal foil or a metal-coated plastic film, the amount of active material of the negative or positive electrode, i.e. the charging of the electrode, based on the coating of one side, is preferably at least 1 mg / cm², more preferably at least 3 mg / cm², more preferably at least 5 mg / cm², more preferably at least 8 mg / cm², more preferably at least 10 mg / cm², and particularly preferably at least 20 mg / cm².

[0037] The maximum loading of the electrode, based on the coating of one side, is preferably at most 150 mg / cm², more preferably at most 100 mg / cm² and particularly preferably at most 80 mg / cm².

[0038] Furthermore, the discharge element of the positive electrode and / or the discharge element of the negative electrode can also be formed three-dimensionally in the form of a porous metal structure, particularly in the form of a metal foam. The three-dimensional porous metal structure is porous enough to allow the active material of the respective electrode to be incorporated into the pores of the metal structure. The amount of incorporated or applied active material constitutes the electrode's charge. If the discharge element is formed three-dimensionally in the form of a porous metal structure, particularly in the form of a metal foam, then the respective electrode preferably has a thickness of at least 0.2 mm, more preferably at least 0.3 mm, more preferably at least 0.4 mm, more preferably at least 0.5 mm, and most preferably at least 0.6 mm.

[0039] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the area-specific capacity of the positive electrode and / or the negative electrode, when using a three-dimensional discharge element, in particular in the form of a metal foam, is preferably at least 2.5 mAh / cm², with the following values ​​being further preferred in this order: 5 mAh / cm², 15 mAh / cm², 25 mAh / cm², 35 mAh / cm², 45 mAh / cm², 55 mAh / cm², 65 mAh / cm², 75 mAh / cm². If the discharge element is three-dimensionally formed in the form of a porous metal structure, in particular in the form of a metal foam, the amount of active material of the positive or negative electrode, i.e.,The loading of each electrode, based on its area, is at least 10 mg / cm², preferably at least 20 mg / cm², more preferably at least 40 mg / cm², more preferably at least 60 mg / cm², more preferably at least 80 mg / cm², and particularly preferably at least 100 mg / cm². This loading of the respective electrode has a positive effect on the charging and discharging processes of the rechargeable battery cell. The rechargeable battery cell can also comprise at least one positive electrode with a conducting element in the form of a porous metal structure, in particular in the form of a metal foam, and at least one negative electrode with a planar conducting element in the form of a thin metal sheet, a thin metal foil, or a metal-coated plastic film.Alternatively, the rechargeable battery cell can also have at least one negative electrode with a discharge element in the form of a porous metal structure, in particular in the form of a metal foam, and at least one positive electrode with a planar discharge element in the form of a thin metal sheet, a thin metal foil or a metal-coated plastic film.

[0040] The active material of the positive electrode can at least partially or even completely cover the discharge element. Furthermore, the active material of the negative electrode can at least partially or even completely cover the discharge element.

[0041] Both the planar and three-dimensional conductive elements can be multi-part. To connect the conductive elements, the rechargeable battery cell can have additional components, such as tabs, wires, sheets, and the like, which are attached to the respective conductive element. These components can be made of the same material as the conductive element, i.e., aluminum or copper, or of a different material. electrolyte

[0042] The following describes advantageous further developments of the rechargeable battery cell with regard to the SO2-based electrolyte.

[0043] As previously described, the substituents R1<, R2<, R3< and R4< in formula (I) of the first conducting salt are independently selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C40 cycloalkyl, C6-C14 aryl and C5-C14 heteroaryl. In a further advantageous embodiment of the rechargeable

[0044] In a battery cell, the substituents R1<, R2<, R3< and R4< of the first conducting salt are independently selected from the group formed by C1-C6 alkyl; preferably C2-C4 alkyl; particularly preferably the alkyl groups 2-propyl, methyl, and ethyl; C2-C6 alkenyl; preferably C2-C4 alkenyl; particularly preferably the alkenyl groups ethenyl and propenyl; C2-C6 alkynyl; preferably C2-C4 alkynyl; C3-C6 cycloalkyl; phenyl; and C5-C7 heteroaryl.

[0045] In this advantageous embodiment of the SO₂-based electrolyte, the term "C₁-C₆ alkyl" encompasses linear or branched saturated hydrocarbon groups with one to six hydrocarbon groups, in particular methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, 2,2-dimethylpropyl, n-hexyl, and iso-hexyl. C₂-C₄ alkyls are preferred, with 2-propyl, methyl, and ethyl being particularly preferred.

[0046] In this advantageous embodiment of the SO₂-based electrolyte, the term "C₂-C₆ alkenyl" encompasses unsaturated linear or branched hydrocarbon groups with two to six carbon atoms, wherein the hydrocarbon groups have at least one C-C double bond. This includes, in particular, ethenyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, iso-butenyl, 1-pentenyl, and 1-hexenyl, with C₂-C₄ alkenyls being preferred. Ethenyl and 1-propenyl are especially preferred. In this advantageous embodiment of the SO₂-based electrolyte, the term "C₂-C₆ alkynyl" encompasses unsaturated linear or branched hydrocarbon groups with two to six carbon atoms, wherein the hydrocarbon groups have at least one C-C triple bond. This includes in particular ethinyl, 1-propynyl, 2-propynyl, 1-n-butynyl, 2-n-butynyl, iso-butynyl, 1-pentynyl, and 1-hexynyl. C2-C4 alkynyls are preferred among these.

[0047] In the case of this advantageous embodiment of the SO₂-based electrolyte, the term "C₃-C₆ cycloalkyl" encompasses cyclic saturated hydrocarbon groups with three to six carbon atoms. These include, in particular, cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0048] In the case of this advantageous embodiment of the SO2-based electrolyte, the term "C5-C7 heteroaryl" includes phenyl and naphthyl.

[0049] In a further advantageous embodiment of the rechargeable battery cell according to the invention, at least two of the substituents R1<, R2<, R3< and R4< are bridged to each other to form a bidentate chelating ligand. Such a bidentate chelating ligand can, for example, have the following structure:

[0050] Preferably, three or even four of the substituents R1<, R2<, R3<, and R4< can be bridged to each other to form a tridentate or tetradentate chelating ligand. The chelating ligand coordinates to the central atom Z, forming a chelate complex. The term "chelating complex"—or simply "chelate"—refers to complex compounds in which a polydentate ligand (possessing more than one lone pair of electrons) occupies at least two coordination sites (bonding sites) of the central atom. The central atom is the positively charged metal ion Al³⁺< or B³⁺<. The ligand and central atom are linked via coordinate bonds, meaning that the bonding electron pair is provided solely by the ligand.

[0051] An advantageous further development of the rechargeable battery cell according to the invention has a cell voltage of at least 4.0 volts, preferably at least 4.4 volts, more preferably at least 4.8 volts, more preferably at least 5.2 volts, more preferably at least 5.6 volts and particularly preferably at least 6.0 volts.

[0052] To improve the solubility of the first conducting salt in the SO₂-based electrolyte, in a further advantageous embodiment of the rechargeable battery cell, the substituents R₁, R₂, R₃, and R₄ are substituted by at least one fluorine atom and / or by at least one chemical group, wherein the chemical group is selected from the group consisting of C₁-C₄-alkyl, C₂-C₄-alkenyl, C₂-C₄-alkynyl, phenyl, and benzyl. The chemical groups C₁-C₄-alkyl, C₂-C₄-alkenyl, C₂-C₄-alkynyl, phenyl, and benzyl exhibit the same properties and chemical structures as the hydrocarbon groups described above. In this context, substituted means that individual atoms or groups of atoms of the substituents R 1< , R 2< , R 3< and R 4< are replaced by the fluorine atom and / or by the chemical group.

[0053] A particularly high solubility of the first conducting salt in the SO2-based electrolyte can be achieved by having at least one of the substituents R1< , R2< , R3< and R4< be a CF3 group or an OSO2 CF3 group.

[0054] In a further advantageous development of the rechargeable battery cell, the first conducting salt is selected from the group formed by

[0055] The last-mentioned first conducting salt with the molecular formula LiB(O 2 C 2 (CF 3 ) 4 ) 2 has two bidentate chelating ligands with the following structure which are coordinated to the central atom B 3+< to form the chelate complex. For this purpose, two perfluorinated alkoxy substituents are bridged to each other via a C-C single bond.

[0056] In order to adjust the conductivity and / or other properties of the electrolyte to a desired value, in a further advantageous embodiment of the rechargeable battery cell according to the invention, the electrolyte comprises at least a second conducting salt that differs from the first conducting salt according to formula (I). This means that, in addition to the first conducting salt, the electrolyte can contain one or more further second conducting salts that differ from the first conducting salt in their chemical composition and chemical structure.

[0057] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the second conducting salt is an alkali metal compound, in particular a lithium compound. The alkali metal compound or the lithium compound is selected from the group consisting of an aluminate, a halide, an oxalate, a borate, a phosphate, an arsenate, and a gallate. Preferably, the second conducting salt is a lithium tetrahaloaluminate, in particular LiAlCl₄.

[0058] Furthermore, in a further advantageous embodiment of the rechargeable battery cell according to the invention, the electrolyte contains at least one additive. This additive is preferably selected from the group consisting of vinylene carbonate and its derivatives, vinylethylene carbonate and its derivatives, methylethylene carbonate and its derivatives, lithium (bisoxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium oxalate, 2-vinylpyridine, 4-vinylpyridine, cyclic exomethylene carbonates, sulfones, cyclic and acyclic sulfonates, acyclic sulfites, cyclic and acyclic sulfinates, organic esters of inorganic acids, acyclic and cyclic alkanes, which have a boiling point at 1 bar of at least 36 °C, aromatic compounds, halogenated cyclic and acyclic sulfonylimides, halogenated cyclic and acyclic phosphate esters.halogenated cyclic and acyclic phosphines, halogenated cyclic and acyclic phosphites, halogenated cyclic and acyclic phosphazenes, halogenated cyclic and acyclic silylamines, halogenated cyclic and acyclic halogenated esters, halogenated cyclic and acyclic amides, halogenated cyclic and acyclic anhydrides and halogenated organic heterocycles.

[0059] With regard to the total weight of the electrolyte composition, the electrolyte in a further advantageous embodiment of the rechargeable battery cell has the following composition: (i) 5 to 99.4 wt.% sulfur dioxide, (ii) 0.6 to 95 wt.% of the first leading salt, (iii) 0 to 25 wt.% of the second leading salt and (iv) 0 to 10 wt.% of the additive.

[0060] As mentioned previously, the electrolyte can contain not only a first conducting salt according to formula (I) and a second conducting salt, but also several first conducting salts according to formula (I) and several second conducting salts. In the latter case, the aforementioned percentages also include several first conducting salts and several second conducting salts. The molar concentration of the first conducting salt is in the range of 0.01 mol / l to 10 mol / l, preferably from 0.05 mol / l to 10 mol / l, more preferably from 0.1 mol / l to 6 mol / l, and particularly preferably from 0.2 mol / l to 3.5 mol / l, based on the total volume of the electrolyte.

[0061] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the electrolyte contains at least 0.1 mol SO₂, preferably at least 1 mol SO₂, more preferably at least 5 mol SO₂, more preferably at least 10 mol SO₂, and particularly preferably at least 20 mol SO₂ per mol of conducting salt. The electrolyte can also contain very high molar amounts of SO₂, with the preferred upper limit being 2600 mol SO₂ per mol of conducting salt, and upper limits of 1500, 1000, 500, and 100 mol SO₂ per mol of conducting salt in that order being further preferred. The term "per mol of conducting salt" refers to all conducting salts contained in the electrolyte.SO₂-based electrolytes with such a concentration ratio between SO₂ and the conducting salt have the advantage that, compared to electrolytes known from the prior art, which are based, for example, on an organic solvent mixture, they can dissolve a larger quantity of conducting salt. Within the scope of the invention, it was found that, surprisingly, an electrolyte with a relatively low concentration of conducting salt is advantageous despite the associated higher vapor pressure, particularly with regard to its stability over many charge and discharge cycles of the rechargeable battery cell. The concentration of SO₂ in the electrolyte affects its conductivity. Thus, by selecting the SO₂ concentration, the conductivity of the electrolyte can be adapted to the intended use of a rechargeable battery cell operated with this electrolyte.The total content of SO2 and the first conducting salt can be greater than 50 wt% of the weight of the electrolyte, preferably greater than 60 wt%, more preferably greater than 70 wt%, more preferably greater than 80 wt%, more preferably greater than 85 wt%, more preferably greater than 90 wt%, more preferably greater than 95 wt% or more preferably greater than 99 wt%.

[0062] The electrolyte may contain at least 5 wt% SO₂ based on the total amount of electrolyte contained in the rechargeable battery cell, with values ​​of 20 wt% SO₂, 40 wt% SO₂ and 60 wt% SO₂ being further preferred. The electrolyte may also contain up to 95 wt% SO₂, with maximum values ​​of 80 wt% SO₂ and 90 wt% SO₂ being preferred in that order.

[0063] It is within the scope of the invention that the electrolyte preferably contains only a small percentage or even no percentage of at least one organic solvent. Preferably, the proportion of organic solvents in the electrolyte, which is present, for example, in the form of one or a mixture of several solvents, may be at most 50% by weight of the electrolyte. Particularly preferred are lower proportions of at most 40% by weight, at most 30% by weight, at most 20% by weight, at most 15% by weight, at most 10% by weight, at most 5% by weight, or at most 1% by weight of the electrolyte. It is further preferred that the electrolyte is free of organic solvents. Due to the small proportion of organic solvents or even their complete absence, the electrolyte is either barely flammable or not flammable at all.This increases the operational reliability of a rechargeable battery cell operated with such an SO₂-based electrolyte. The SO₂-based electrolyte is particularly preferably free of organic solvents.

[0064] With regard to the total weight of the electrolyte composition, the electrolyte in a further advantageous embodiment of the rechargeable battery cell has the following composition: (i) 5 to 99.4 wt.% sulfur dioxide, (ii) 0.6 to 95 wt.% of the first leading salt, (iii) 0 to 25 wt.% of the second leading salt, (iv) 0 to 10 wt.% of the additive and (v) 0 to 50 wt.% of an organic solvent. Active metal

[0065] Advantageous further developments of the rechargeable battery cell according to the invention with regard to the active metal are described below: In an advantageous further development of the rechargeable battery cell, the active metal an alkali metal, in particular lithium or sodium; an alkaline earth metal, in particular calcium; a metal of group 12 of the periodic table, in particular zinc; or aluminium. Positive electrode

[0066] The following are advantageous further developments of the rechargeable battery cell according to the invention with regard to the positive electrode: A first advantageous further development of the rechargeable battery cell according to the invention provides that the positive electrode can be charged at least up to an upper potential of 4.0 volts, preferably up to a potential of 4.4 volts, more preferably up to a potential of 4.8 volts, more preferably up to a potential of 5.2 volts, more preferably up to a potential of 5.6 volts and particularly preferably up to a potential of 6.0 volts.

[0067] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the positive electrode contains at least one active material. This material can store ions of the active metal and release and reabsorb these ions during operation of the battery cell.

[0068] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the positive electrode contains at least one intercalation compound. For the purposes of this invention, the term "intercalation compound" refers to a subcategory of the insertion materials described above. This intercalation compound acts as a host matrix with interconnected vacancies. During the discharge process of the rechargeable battery cell, the ions of the active metal can diffuse into these vacancies and be incorporated there. This incorporation of the ions of the active metal results in only minor or no structural changes in the host matrix.

[0069] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the positive electrode contains at least one conversion compound as the active material. For the purposes of this invention, the term "conversion compounds" refers to materials that form other materials during electrochemical activity; that is, chemical bonds are broken and reformed during the charging and discharging of the battery cell. Structural changes occur in the matrix of the conversion compound during the uptake or release of ions from the active metal.

[0070] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the active material has the composition A x M' y M" z O a. In this composition A x M' y M" z O a, the following components are present: A at least one metal selected from the group consisting of the alkali metals, the alkaline earth metals, the metals of group 12 of the periodic table, or aluminum; M' at least one metal selected from the group consisting of the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn; M" at least one element selected from the group consisting of the elements of groups 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and 16 of the periodic table of elements; x and y independently greater than 0 numbers; z a number greater than or equal to 0; and a a number greater than 0.

[0071] A is preferably the metal lithium, i.e. the compound can have the composition Li x M' y M" z O a.

[0072] The indices y and z in the composition A x M' y M" z O a refer to the entirety of the metals and elements represented by M' and M" respectively. For example, if M' comprises two metals M' 1< and M' 2<, then the index y is given by: y = y1 + y2, where y1 and y2 represent the indices of the metals M' 1< and M' 2<. The indices x, y, z, and a must be chosen such that charge neutrality prevails within the composition.

[0073] Examples of compounds where M' comprises two metals are lithium nickel manganese cobalt oxides of the composition Li x Ni y1 Mn y2 Co z O 2 with M' 1< = Ni, M' 2< = Mn and M'' = Co. Examples of compounds where z=0, i.e., which do not contain any other metal or element M'', are lithium cobalt oxides Li x Co y O a . For example, if M" comprises two elements, a metal M"<1 and phosphorus M"<2, then the index z is given by: z = z1 + z2, where z1 and z2 represent the indices of the metal M"1 and the phosphorus M"2, respectively. The indices x, y, z, and a must be chosen to ensure charge neutrality within the composition. Examples of compounds where A is lithium, M" comprises a metal M"1 and phosphorus M"2 are lithium iron manganese phosphates Lix Fey Mn z1 P z2 O4, with A = Li, M' = Fe, M"1 = Mn, M"2 = P, and z2 = 1. In another composition, M" can comprise two nonmetals, for example, fluorine M"1 and sulfur M"2.Examples of such compounds are lithium iron fluorosulfates Li x Fe y F z1 S z2 O 4 with A= Li, M'=Fe, M" 1 =F and M" 2 =P.

[0074] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that M' consists of the metals nickel and manganese and M" is cobalt. These can be compositions of the formula Li x Ni y1 Mn y2 Co z O 2 (NMC), i.e., lithium nickel manganese cobalt oxides having the structure of layered oxides. Examples of these active materials made of lithium nickel manganese cobalt oxide are LiNi 1 / 3 Mn 1 / 3 CO 1 / 3 O 2 (NMC111), LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622), and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811).Other compounds of lithium nickel manganese cobalt oxide can have the composition LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.5 Mn 0.25 Co 0.25 O 2 , LiNi 0.52 Mn 0.32 Co 0.16 O 2 , LiNi 0.55 Mn 0.30 Co 0.15 O 2 , LiNi 0.58 Mn 0.14 Co 0.28 O 2 , LiNi 0.64 Mn 0.18 Co 0.18 O 2 , LiNi 0.65 Mn 0.27 Co 0.08 O 2 , LiNi 0.7 Mn 0.2 Co 0.1 O 2 , LiNi 0.7 Mn 0.15 Co 0.15 O 2 , LiNi 0.12 Mn 0.10 Co 0.18 O 2 , LiNi 0.76 Mn 0.14 Co 0.10 O 2 , LiNi 0.86 Mn 0.04 Co 0.10 O 2 , LiNi 0.90 Mn 0.05 Co 0.05 O 2 , LiNi 0.95 Mn 0.025 Co 0.025 O 2 or a combination thereof. These compounds can be used to produce positive electrodes for rechargeable battery cells with a cell voltage above 4.6 volts.

[0075] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the active material is a metal oxide rich in lithium and manganese (in English: Lithium- and Manganese-Rich Oxide Material). This metal oxide can have the composition Li x Mn y M" z O a. In the formula Li x M' y M" z O a described above, M' thus represents the metal manganese (Mn). The subscript x is greater than or equal to 1, the subscript y is greater than the subscript z, or greater than the sum of the subscripts z1+z2+z3, etc. If, for example, M" comprises two metals M" 1< and M" 2< with the subscripts z1 and z2 (e.g., Li 1.2 Mn 0.525 Ni 0.175 Co 0.1 O 2 with M" 1< = Ni z1=0.175 and M" 2< = Co z2=0.1), then the following applies to the subscript y: y>z1+z2, the subscript z is greater than or equal to 0, and the subscript a is greater than 0. The subscripts x, y, z, and a must be chosen such that charge neutrality is ensured. within the composition prevails.Metal oxides rich in lithium and manganese can also be described by the formula mLi₂MnO₃·(1-m)LiM'O₂, where 0 < m < 1. Examples of such compounds are Li₁₂Mn₀.525Ni₀.175Co₀.1O₂, Li₁₂Mn₀.6Ni₀.2O₂, or Li₁₂Ni₀.13Co₀.13Mn₀.54O₂.

[0076] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the composition has the formula A x M' y M" z O 4. These compounds are spinel structures. For example, A can be lithium, M' cobalt, and M" manganese. In this case, the active material is lithium cobalt manganese oxide (LiCoMnO 4). Positive electrodes for rechargeable battery cells with a cell voltage of over 4.6 volts can be produced using LiCoMnO 4. This LiCoMnO 4 is preferably Mn 3+< free. In another example, M' can be nickel and M" manganese. In this case, the active material is lithium nickel manganese oxide (LiNiMnO 4). The molar proportions of the two metals M' and M" can vary. Lithium nickel manganese oxide can, for example, have the composition LiNi 0.5 Mn 1.5 O 4.

[0077] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the positive electrode contains at least one active material, which is a conversion compound. During the uptake of the active metal, e.g., lithium or sodium, conversion compounds undergo a solid-state redox reaction in which the crystal structure of the material changes. This occurs through the breaking and recombination of chemical bonds. Completely reversible reactions of conversion compounds can, for example, proceed as follows: Type A: MX z + y Li ↔ M + z Li (y / z) X Type B: X + y Li ↔ Li y X

[0078] Examples of conversion compounds are FeF 2 , FeF 3 , CoF 2 , CuF 2 , NiF 2 , BiF 3 , FeCl 3 , FeCl 2 , CoCl 2 , NiCl 2 , CuCl 2 , AgCl, LiCl, S, Li 2 S, Se, Li 2 Se, Te, I and Lil.

[0079] In a further advantageous embodiment, the compound has the composition A x M' y M" 1< z1 M" 2< z2 O 4, where M" 1< is selected from the group formed by the elements of groups 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and 16 of the periodic table of elements, M" 2< is the element phosphorus, x and y are independent values ​​greater than 0, z1 is a value greater than 0, and z2 has the value 1. The compound with the composition A x M' y M" 1< z1 M" 2< z2 O 4 is a so-called lithium metal phosphate. In particular, this compound has the composition Li x Fe y Mn z1 P z2 O 4. Examples of lithium metal phosphates are lithium iron phosphate (LiFePO₄) or lithium iron manganese phosphates (Li(Fe₂YMn₂Z)PO₄). An example of a lithium iron manganese phosphate is the phosphate with the composition Li(Fe₂O₃Mn₂O₇)PO₄.7) PO4. Lithium metal phosphates of other compositions can also be used for the battery cell according to the invention.

[0080] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the positive electrode contains at least one metal compound. This metal compound is selected from the group consisting of a metal oxide, a metal halide, and a metal phosphate. Preferably, the metal of this metal compound is a transition metal with atomic numbers 22 to 28 of the periodic table of elements, in particular cobalt, nickel, manganese, or iron.

[0081] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the positive electrode contains at least one metal compound having the chemical structure of a spinel, a layered oxide, a conversion compound or a polyanionic compound.

[0082] It is within the scope of the invention that the positive electrode, as the active material, contains at least one of the described compounds or a combination of the compounds. A combination of the compounds is understood to be a positive electrode containing at least two of the described materials.

[0083] In a further advantageous embodiment of the battery cell according to the invention, the positive electrode comprises at least one binder. This binder is preferably a fluorinated binder, in particular a polyvinylidene fluoride and / or a terpolymer composed of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. However, it can also be a binder consisting of a polymer composed of monomeric structural units of a conjugated carboxylic acid, or of the alkali, alkaline earth, or ammonium salt of this conjugated carboxylic acid, or of a combination thereof. Furthermore, the binder can also consist of a polymer based on monomeric styrene and butadiene structural units. Finally, the binder can also be a binder from the group of carboxymethylcelluloses.The binder is preferably present in the positive electrode in a concentration of at most 20 wt%, more preferably at most 15 wt%, more preferably at most 10 wt%, more preferably at most 7 wt%, more preferably at most 5 wt% and particularly preferably at most 2 wt% based on the total weight of the positive electrode. Negative electrode

[0084] Advantageous embodiments of the rechargeable battery cell according to the invention with regard to the negative electrode are described below: A further advantageous embodiment of the rechargeable battery cell provides that the negative electrode is an insertion electrode. This insertion electrode contains an insertion material as the active material, into which the ions of the active metal are inserted during charging of the rechargeable battery cell and from which the ions of the active metal can be removed during discharging of the rechargeable battery cell. This means that the electrode processes can take place not only on the surface of the negative electrode, but also within the interior of the negative electrode.For example, if a lithium-based conducting salt is used, lithium ions can be inserted into the insertion material during charging of the rechargeable battery cell and released from it during discharging. Preferably, the negative electrode contains carbon as the active material or insertion material, particularly in the graphite form. However, it is also within the scope of the invention that the carbon is present in the form of natural graphite (flake-forming or rounded), synthetic graphite (mesophase graphite), graphitized MesoCarbon MicroBeads (MCMB), carbon-coated graphite, or amorphous carbon.

[0085] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the negative electrode comprises lithium intercalation anode active materials that do not contain carbon, such as lithium titanates (e.g. Li 4 Ti 5 O 12 ).

[0086] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the negative electrode comprises lithium alloy-forming anode active materials. These are, for example, lithium-storing metals and metal alloys (e.g., Si, Ge, Sn, SnCo x C y , SnSi x and the like) and oxides of the lithium-storing metals and metal alloys (e.g., SnO x , SiO x , oxide glasses of Sn, Si and the like).

[0087] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the negative electrode contains conversion anode active materials. These conversion anode active materials can be, for example, transition metal oxides in the form of manganese oxides (MnO₃), iron oxides (FeO₃), cobalt oxides (CoO₃), nickel oxides (NiO₃), copper oxides (CuO₃), or metal hydrides in the form of magnesium hydride (MgH₂), titanium hydride (TiH₂), aluminum hydride (AlH₃), and boron-, aluminum-, and magnesium-based ternary hydrides, and the like.

[0088] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the negative electrode comprises a metal, in particular metallic lithium.

[0089] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the negative electrode is porous, with the porosity preferably being at most 50%, more preferably at most 45%, more preferably at most 40%, more preferably at most 35%, more preferably at most 30%, more preferably at most 20%, and most preferably at most 10%. The porosity represents the ratio of the void volume to the total volume of the negative electrode, the void volume being formed by so-called pores or cavities. This porosity leads to an increase in the internal surface area of ​​the negative electrode. Furthermore, the porosity reduces the density of the negative electrode and thus also its weight. During operation, the individual pores of the negative electrode can preferably be completely filled with the electrolyte.

[0090] In a further advantageous embodiment of the battery cell according to the invention, the negative electrode comprises at least one binder. This binder is preferably a fluorinated binder, in particular a polyvinylidene fluoride and / or a terpolymer composed of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. However, it can also be a binder consisting of a polymer composed of monomeric structural units of a conjugated carboxylic acid, or of the alkali, alkaline earth, or ammonium salt of this conjugated carboxylic acid, or of a combination thereof. Furthermore, the binder can also consist of a polymer based on monomeric styrene and butadiene structural units. Finally, the binder can also be a binder from the group of carboxymethylcelluloses.The binder is preferably present in the negative electrode in a concentration of at most 20 wt%, more preferably at most 15 wt%, more preferably at most 10 wt%, more preferably at most 7 wt%, more preferably at most 5 wt% and particularly preferably at most 2 wt% based on the total weight of the negative electrode.

[0091] In a further advantageous embodiment of the battery cell according to the invention, the negative electrode comprises at least one conductivity additive. The conductivity additive should preferably have low weight, high chemical resistance, and a high specific surface area. Examples of conductivity additives are particulate carbon (carbon black, Super P, acetylene black), fibrous carbon (CarbonNanoTubes CNT, carbon (nano)fibers), finely divided graphite, and graphene (nano-sheets). Structure of the rechargeable battery cell

[0092] Advantageous embodiments of the rechargeable battery cell according to the invention are described below with regard to its structure: To further improve the function of the rechargeable battery cell, a further advantageous embodiment of the rechargeable battery cell according to the invention provides that the rechargeable battery cell comprises several negative electrodes and several positive electrodes, which are arranged alternately stacked in the housing. The positive electrodes and the negative electrodes are preferably electrically separated from each other by separators.

[0093] The rechargeable battery cell can also be designed as a wound cell, in which the electrodes consist of thin layers wound together with a separator material. The separators physically and electrically separate the positive and negative electrodes and are also permeable to the ions of the active metal. This creates large electrochemically active surfaces, enabling a correspondingly high current output. The separator can be made of a nonwoven fabric, a membrane, a woven fabric, a knitted fabric, an organic material, an inorganic material, or a combination thereof. Organic separators can consist of unsubstituted polyolefins (e.g., polypropylene or polyethylene), partially to fully halogen-substituted polyolefins (e.g., partially to fully fluorine-substituted, especially PVDF, ETFE, PTFE), polyesters, polyamides, or polysulfones.Separators containing a combination of organic and inorganic materials include, for example, glass fiber textiles in which the glass fibers are coated with a suitable polymer. The coating preferably contains a fluorine-containing polymer such as polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroethylene propylene (FEP), THV (a terpolymer of tetrafluoroethylene, hexafluoroethylene, and vinylidene fluoride), a perfluoroalkoxy polymer (PFA), aminosilane, polypropylene, or polyethylene (PE). The separator can also be folded within the housing of the rechargeable battery cell, for example, in the form of so-called "Z-folding." In this Z-folding, a strip-shaped separator is folded through or around the electrodes in a Z-shape. Furthermore, the separator can also be designed as separator paper.

[0094] It is also within the scope of the invention that the separator can be designed as a casing, wherein each positive electrode or each negative electrode is enclosed by the casing. The casing can be made of a nonwoven fabric, a membrane, a woven fabric, a knitted fabric, an organic material, an inorganic material, or a combination thereof.

[0095] Encasing the positive electrode leads to a more uniform ion migration and distribution within the rechargeable battery cell. The more uniform the ion distribution, particularly in the negative electrode, the higher the potential charging of the negative electrode with active material and, consequently, the usable capacity of the rechargeable battery cell. Simultaneously, risks associated with uneven charging and the resulting deposition of the active metal are avoided. These advantages are particularly pronounced when the positive electrodes of the rechargeable battery cell are encased.

[0096] The surface dimensions of the electrodes and the covering can preferably be coordinated in such a way that the outer dimensions of the covering of the electrodes and the outer dimensions of the uncovered electrodes match at least in one dimension.

[0097] The surface area of ​​the coating can preferably be larger than the surface area of ​​the electrode. In this case, the coating extends beyond a boundary of the electrode. Two layers of the coating covering both sides of the electrode can therefore be joined together at the edge of the positive electrode by an edge connection.

[0098] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the negative electrodes have a covering, while the positive electrodes do not have a covering.

[0099] Further advantageous features of the invention are described and explained in more detail below with reference to figures, examples and experiments. Figure 1: shows a first embodiment of a rechargeable battery cell according to the invention in a cross-sectional view; Figure 2: shows an electron micrograph of the three-dimensional porous structure of the metal foam of the first embodiment from Figure 1 as a detailed view; Figure 3: shows a second embodiment of a rechargeable battery cell according to the invention in a cross-sectional view; Figure 4: shows a detail of the second embodiment from Figure 3Figure 5: shows a third embodiment of the rechargeable battery cell according to the invention in an exploded view; Figure 6: shows the potential in [V] of two test cells with graphite electrodes with copper or nickel leakage elements, filled with the reference electrolyte from Example 1, during charging as a function of the capacity, which is based on the theoretical capacity of the negative electrode, during a coating layer formation on the negative electrode; Figure 7: shows the discharge capacity as a function of the number of cycles of two test cells with graphite electrodes with copper or nickel leakage elements, wherein the test cells are filled with the reference electrolyte; Figure 8: shows the potential in [V] of two test cells with graphite electrodes with copper or nickel leakage elements.Nickel discharge element filled with electrolyte 1, during charging as a function of the capacitance, which is referenced to the theoretical capacitance of the negative electrode, during a layer formation on the negative electrode; Figure 9: shows the discharge capacity as a function of the number of cycles of two test cells with graphite electrodes with copper and nickel discharge elements respectively, the test cells being filled with electrolyte 1; Figure 10 shows a photograph of the copper discharge element after measurement. Figure 9Figure 11: shows the potential profile during charging and discharging in volts as a function of the percentage charge of one cycle of a half-cell with a graphite electrode and a copper discharge element, the half-cell being filled with electrolyte 5; Figure 12: shows the potential and current as a function of time of half-cells with an aluminum discharge element, the half-cells being filled with either the reference electrolyte or electrolyte 1; Figure 13: shows an aluminum discharge element before the experiment in the half-cell with reference electrolyte. Figure 12 Figure 14 shows the aluminum discharge element after the experiment in the half-cell with reference electrolyte. Figure 12 Figure 15 shows the aluminum discharge element after the experiment in the half-cell with electrolyte 1. Figure 12Figure 16 shows the potential profile during charging and discharging in volts as a function of the percentage charge of the first cycle of a half-cell with a positive electrode with an aluminum discharge element, the half-cell being filled with electrolyte 1; Figure 17 shows the discharge capacity as a function of the number of cycles of a test full cell with a positive electrode with an aluminum discharge element, the test full cell being filled with electrolyte 1; Figure 18 shows the discharge capacities as a function of the number of cycles of two full cells with positive electrodes with an aluminum discharge element and negative electrodes with a copper discharge element, the full cells being filled with electrolyte 1 and the final charging voltage being 4.3 and 4.6 volts, respectively;Figure 19: shows the potential profile during charging and discharging in volts as a function of the percentage charge of the first cycle of a half-cell with a positive electrode with an aluminum discharge element, the half-cell being filled with electrolyte 5; Figure 20: shows the potential in [V] of three test full cells filled with electrolytes 1 and 3 from Example 2 and the reference electrolyte from Example 1, during charging of a negative electrode as a function of the capacitance relative to the theoretical capacitance of the negative electrode, during a coating layer formation on the negative electrode; Figure 21: shows the potential profile during discharge in volts as a function of the percentage charge of four test full cells filled with electrolytes 1, 3, 4 and 5 from Example 2 and containing lithium nickel manganese cobalt oxide (NMC) as the active electrode material;Figure 22 shows the conductivities in [mS / cm] of electrolytes 1, 4 and 6 from Example 2 as a function of the concentration of compounds 1, 4 and 6; and Figure 23 shows the conductivities in [mS / cm] of electrolytes 3 and 5 from Example 2 as a function of the concentration of compounds 3 and 5.

[0100] Figure 1Figure 1 shows a first embodiment of a rechargeable battery cell 2 according to the invention in cross-sectional view. This rechargeable battery cell 2 is designed as a prismatic cell and includes, among other things, a housing 1. This housing 1 encloses an electrode arrangement 3, which comprises three positive electrodes 4 and four negative electrodes 5. The positive electrodes 4 and the negative electrodes 5 are arranged alternately stacked in the electrode arrangement 3. However, the housing 1 can also accommodate more positive electrodes 4 and / or negative electrodes 5. In general, it is preferred if the number of negative electrodes 5 is one greater than the number of positive electrodes 4. This results in the outer end faces of the electrode stack being formed by the electrode surfaces of the negative electrodes 5.Electrodes 4 and 5 are connected via electrode terminals 6 and 7 to corresponding terminals 9 and 10 of the rechargeable battery cell 2. The rechargeable battery cell 2 is filled with an SO₂-based electrolyte such that the electrolyte penetrates as completely as possible into all pores and cavities, especially within electrodes 4 and 5. The electrolyte is in . Figure 1Not visible. In the present embodiment, the positive electrodes 4 contain an intercalation compound as the active material. This intercalation compound is LiCoMnO 4 with a spinel structure. In the present embodiment, the electrodes 4, 5 are planar, i.e., layers with a thickness that is smaller than their surface area. They are separated from each other by separators 11. The housing 1 of the rechargeable battery cell 2 is essentially cuboidal, with the electrodes 4, 5 and the walls of the housing 1, shown in cross-sectional view, extending perpendicular to the plane of the drawing and being essentially straight and planar. However, the rechargeable battery cell 2 can also be designed as a wound cell, in which the electrodes consist of thin layers wound together with a separator material.The separators 11 spatially and electrically separate the positive electrode 4 and the negative electrode 5, and are also permeable to the ions of the active metal. This creates large electrochemically active surfaces, enabling a correspondingly high current yield. Electrodes 4 and 5 each have a lead element that provides the necessary electronically conductive connection for the active material of the respective electrode. This lead element is in contact with the active material involved in the electrode reaction of the respective electrode 4 or 5 (in ). Figure 1(not shown). The discharge elements are formed in the form of a porous metal foam 18. The metal foam 18 extends over the thickness dimension of the electrodes 4, 5. The active material of the positive electrodes 4 and the negative electrodes 5 is incorporated into the pores of this metal foam 18, so that it uniformly fills its pores over the entire thickness of the metal structure. To improve mechanical strength, the positive electrodes 4 contain a binder. This binder is a fluoropolymer. The negative electrodes 5 contain carbon as the active material in a form suitable as an insertion material for the uptake of lithium ions. The structure of the negative electrode 5 is similar to that of the positive electrode 4. In the present first embodiment, one discharge element of the positive electrode 4 is made of aluminum and one discharge element of the negative electrode 5 is made of copper.

[0101] Figure 2 shows an electron micrograph of the three-dimensional porous structure of the metal foam 18 of the first embodiment. Figure 1 Based on the given scale, it can be seen that the pores P have an average diameter of more than 100 µm, and are therefore relatively large.

[0102] Figure 3 Figure 1 shows a second embodiment of a rechargeable battery cell 20 according to the invention in cross-sectional view. This second embodiment differs from the one shown in Figure 2. Figure 1The first embodiment shown is distinguished by the fact that the electrode arrangement comprises a positive electrode 23 and two negative electrodes 22. They are each separated from one another by separators 21 and surrounded by a housing 28. The positive electrode 23 has a discharge element 26 in the form of a planar metal foil, onto which the active material 24 of the positive electrode 23 is applied on both sides. The negative electrodes 22 also comprise a second discharge element 27 in the form of a planar metal foil, onto which the active material 25 of the negative electrode 22 is applied on both sides. Alternatively, the planar discharge elements of the edge electrodes, i.e., the electrodes that terminate the electrode stack, can be coated with active material on only one side. The uncoated side faces the wall of the housing 28.The electrodes 22, 23 are connected via electrode terminals 29, 30 to corresponding connection contacts 31, 32 of the rechargeable battery cell 20.

[0103] Figure 4 The planar metal foil, which serves as a conductor element 26, 27 for the positive electrodes 23 and the negative electrodes 22 in the second embodiment, is shown. Figure 3 This metal foil has a perforated or net-like structure with a thickness of 20 µm.

[0104] Figure 5 Figure 1 shows a third embodiment of a rechargeable battery cell 40 according to the invention in an exploded view. This third embodiment differs from the two previously described embodiments in that the positive electrode 44 is enclosed by a casing 13. The surface area of ​​the casing 13 is larger than the surface area of ​​the positive electrode 44, the boundary 14 of which is defined in Figure 5The positive electrode 44 is shown as a dashed line. Two layers 15, 16 of the covering 13, which cover both sides of the positive electrode 44, are connected to each other at the circumferential edge of the positive electrode 44 by an edge connection 17. The two negative electrodes 45 are not covered. The electrodes 44 and 45 can be contacted via the electrode terminals 46 and 47. Example 1: Production of a reference electrolyte

[0105] A reference electrolyte used for the examples described below was prepared according to the process described in patent EP 2 954 588 B1 (hereinafter referred to as [V6]). First, lithium chloride (LiCl) was dried under vacuum at 120 °C for three days. Aluminum particles (Al) were dried under vacuum at 450 °C for two days. LiCl, aluminum chloride (AlCl₃), and Al were mixed together in a molar ratio AlCl₃:LiCl:Al of 1:1.06:0.35 in a glass bottle with a gas-permeable opening. This mixture was then heat-treated stepwise to produce a molten salt. After cooling, the resulting molten salt was filtered, then cooled to room temperature, and finally SO₂ was added until the desired molar ratio of SO₂ to LiAlCl₄ was achieved.The reference electrolyte thus formed had the composition LiAlCl 4 * x SO 2 , where x depends on the amount of SO 2 supplied. Example 2: Production of six embodiments 1, 2, 3, 4, 5 and 6 of an SO2-based electrolyte for a battery cell

[0106] For the experiments described below, six embodiments 1, 2, 3, 4, 5 and 6 of the SO₂-based electrolyte were prepared (hereinafter referred to as electrolytes 1, 2, 3, 4, 5 and 6). For this purpose, five different first conducting salts according to formula (I) were first prepared according to a preparation procedure described in the following documents [V7], [V8] and [V9]: [V7] "I. Krossing, Chem. Eur. J. 2001, 7, 490; [V8] SM Ivanova et al., Chem. Eur. J. 2001, 7, 503; [V9] Tsujioka et al., J. Electrochem. Soc., 2004, 151, A1418"

[0107] These six different, first conducting salts according to formula (I) are subsequently referred to as compounds 1, 2, 3, 4, 5 and 6. They belong to the polyfluoroalkoxyaluminate family and were prepared according to the following reaction equation starting from LiAlH₄ and the corresponding alcohol R-OH with R₁< =R₂< =R₃< =R₄< in hexane.

[0108] Chelate complexes were prepared from the corresponding diol HO-R-OH according to a manufacturing process described in the following document [V10]: [V10] Wu Xu et al., Electrochem. Solid-State Lett. 2000, 3, 366-368

[0109] This resulted in the following compounds 1, 2, 3, 4, 5 and 6 being formed with their respective molecular and structural formulas:

[0110] For purification, compounds 1, 2, 3, 4, 5, and 6 were first recrystallized. This removed any residues of the starting material LiAlH₄ from the first conducting salt, as this starting material could potentially lead to sparking in the presence of any traces of water in SO₂.

[0111] Subsequently, compounds 1, 2, 3, 4, 5 and 6 were dissolved in SO2. It was found that compounds 1, 2, 3, 4, 5 and 6 dissolved well in SO2.

[0112] The production of electrolytes 1, 2, 3, 4, 5 and 6 was carried out at low temperature or under pressure according to the following process steps 1 to 4: 1) Place each of the respective compounds 1, 2, 3, 4, 5 and 6 into a pressure flask with a riser tube, 2) Evacuate the pressure flasks, 3) Infuse liquid SO2 and 4) Repeat steps 2 + 3 until the target amount of SO2 has been added.

[0113] The respective concentrations of compounds 1, 2, 3, 4, 5, and 6 in electrolytes 1, 2, 3, 4, 5, and 6 were 0.6 mol / L (mol concentration per liter of electrolyte), unless otherwise specified in the experimental description. The experiments described below were performed using electrolytes 1, 2, 3, 4, 5, and 6 and the reference electrolyte. Example 3: Production of test full cells

[0114] The test cells used in the experiments described below are rechargeable battery cells with two negative electrodes and one positive electrode, each separated by a separator. The positive electrodes contained an active material, a conductivity enhancer, a binder, and a grounding element. The active material of the positive electrode is specified in the respective experiment. The negative electrodes contained graphite as the active material, a binder, and also a grounding element. If mentioned in the experiment, the negative electrodes may also contain a conductivity additive. The grounding element materials of the positive and negative electrodes are aluminum and copper, respectively, and are specified in the respective experiment. Nickel serves as the reference grounding material from the prior art.Among other things, the aim of the investigations is to confirm the use of the conductive materials aluminum and copper for the positive and negative electrodes in a battery cell according to the invention. Table 3 shows which tests were carried out with the different conductive materials.

[0115] The test cells were each filled with the electrolyte required for the experiments, i.e., either the reference electrolyte or electrolytes 1, 2, 3, 4, 5, or 6. For each experiment, several identical test cells were prepared, i.e., two to four. The results presented in the experiments are mean values ​​obtained from the measurements taken for the identical test cells. Example 4: Measurement in test full cells Top layer capacity:

[0116] The capacity consumed in the first cycle for the formation of a coating layer on the negative electrode is an important criterion for the quality of a battery cell. This coating layer forms on the negative electrode during the first charging of the test cell. Lithium ions are irreversibly consumed for this coating layer formation (coating layer capacity), so the test cell has less cycleable capacity available for subsequent cycles. The coating layer capacity, expressed as a percentage of the theoretical capacity, consumed for the formation of the coating layer on the negative electrode is calculated using the following formula: Deckschichtkapazität in % der Theorie = Q lad x mAh − Q ent y mAh / Q NEL

[0117] Qlad describes the amount of charge in mAh specified in the respective experiment; Qent describes the amount of charge in mAh obtained during the subsequent discharge of the test cell. QNEL is the theoretical capacity of the negative electrode used. For example, the theoretical capacity of graphite is calculated to be 372 mAh / g. Discharge capacity:

[0118] In measurements using test cells, the discharge capacity is determined, for example, by the number of cycles. For this purpose, the test cells are charged with a specific charging current up to a certain upper potential. This upper potential is maintained until the charging current has dropped to a specific value. Discharge then occurs with a specific discharge current down to a specific discharge potential. This charging method is called current-voltage charging. This process is repeated depending on the desired number of cycles.

[0119] The upper potentials (or discharge potential) and the respective charging and discharging currents are specified in the experiments. The value to which the charging current must have dropped is also described in the experiments.

[0120] The term "upper potential" is used synonymously with "charging potential," "charging voltage," "final charging voltage," and "upper potential limit." These terms refer to the voltage / potential to which a cell or battery is charged using a battery charging device.

[0121] Preferably, the battery is charged at a current rate of C / 2 and at a temperature of 22°C.

[0122] The term "discharge potential" is used synonymously with "lower cell voltage". It refers to the voltage / potential to which a cell or battery is discharged using a battery charging device.

[0123] Preferably, the battery is discharged at a current rate of C / 2 and at a temperature of 22°C.

[0124] The discharge capacity is derived from the discharge current and the time required to meet the discharge termination criteria. The accompanying figures show average discharge capacities as a function of the number of cycles. These average discharge capacities are often normalized to 100% of the initial capacity and expressed as a percentage of the nominal capacity.

[0125] The following experiments investigate the properties of conductive elements made of either nickel, copper, or aluminum. According to [V3], nickel conductive elements are normally used in the prior art electrolyte LiAlCl₄·xSO₂, which is referred to below as the reference electrolyte. These nickel conductive elements are referred to below as nickel conductive elements (see Example 1). Therefore, experiments were carried out both in the reference electrolyte LiAlCl₄·xSO₂ and in various electrolytes that can also be components of the rechargeable battery cell according to the invention. The electrical conductivities of copper and aluminum known from the literature are better than the electrical conductivity of nickel (see Table 1). Copper and aluminum conductive elements are therefore preferred within the scope of the present invention. Table 1: Electrical conductivities of copper, aluminum and nickel material Electrical conductivity σ / 20°C [S / m] copper 5,80E+07 aluminum 3,70E+07 nickel 1,40E+07 Experiment 1: Behavior of nickel and copper electrodes for the negative electrode in test cells with reference electrolyte of the composition LiAlCl₄ * 4.5 SO₂

[0126] Negative electrodes were fabricated using graphite as the active material. These negative electrodes contained no binder. The discharge element of the first negative electrodes consisted of copper in the form of copper foam. The second negative electrodes contained a nickel discharge element in the form of nickel foam. Nickel is the state-of-the-art material used for discharge elements in rechargeable battery cells with electrolytes of the composition LiAlCl₄·SO₂.

[0127] Two negative electrodes with copper discharge elements were combined with a positive electrode containing lithium iron phosphate as the active electrode material to form a first test cell 1 according to Example 3. A second test cell 2 according to Example 3 was constructed using the negative electrodes containing nickel discharge elements. Both test cells 1 and 2 were filled with a reference electrolyte according to Example 1 with the composition LiAlCl₄ * 4.5 SO₂.

[0128] First, in the first cycle, the surface layer capacities were determined according to Example 4. Figure 6 shows the potential in volts of the test cells when charging the negative electrode as a function of the capacity in [%], which is based on the theoretical capacity of the negative electrode, where the solid curve corresponds to test cell 1 and the dashed curve to test cell 2.

[0129] The two curves shown represent averaged results from several experiments with the test cells 1 and 2 described above. First, the test cells were charged with a current of 15 mA until a capacity of 125 mAh (Qlad) was reached. Then, the test cells were discharged with 15 mA until a potential of 2.5 volts was reached. The discharge capacity (Qent) was then determined.

[0130] The measured capacitances [in % of the theoretical capacitance of the negative electrode] are higher than, for example, the capacitances measured with binder-containing electrodes, due to the lack of binder in the negative electrode. For test cell 1 with a graphite electrode and copper foam discharge element, the capacitance is 19.8%, and for test cell 2 with a graphite electrode and nickel foam discharge element, it is 15.5%.

[0131] To determine the discharge capacities (see Example 4), the two test cells 1 and 2 were charged at a charging rate of C / 2 up to an upper potential of 3.8 volts. They were then discharged at a discharge rate of C / 2 down to a discharge potential of 2.5 volts.

[0132] Figure 7 The graph shows mean discharge capacities of the two test cells 1 and 2 as a function of the number of cycles, with the solid curve representing test cell 1 and the dashed curve representing test cell 2. 190 cycles were performed. These mean discharge capacities are expressed as a percentage of the nominal capacity [% nominal capacity].

[0133] The discharge capacities of the two test cells, 1 and 2, show a steady, decreasing trend. However, the capacity decrease is significantly greater for those test cells containing graphite electrodes with a copper foam discharge element. For example, the capacity of test cell 1 (nickel discharge element) is still at 70% after 190 cycles, while the capacity of test cell 2 (copper discharge element) is only at 64% after 190 cycles.

[0134] In the reference electrolyte, a negative electrode with a nickel discharge element exhibits lower capacitance and better cycle behavior than a negative electrode with a copper discharge element. This also confirms the findings of [V3], which state that nickel is the commonly used discharge element in LiAlCl₄·xSO₂ electrolytes. Experiment 2: Behavior of nickel and copper leakage elements for the negative electrode in test full cells with electrolyte 1

[0135] Negative electrodes were again produced using graphite as the active material. The discharge element of the first negative electrodes consisted of copper in the form of a porous copper foam. The second negative electrodes contained a nickel discharge element in the form of a porous nickel foam.

[0136] Two negative electrodes with copper foam as a grounding element were assembled together with a positive electrode containing lithium nickel manganese cobalt oxide (NMC 622) as the active electrode material to form a first test cell according to Example 3. A second test cell according to Example 3 was also constructed using the negative electrodes containing nickel foam as a grounding element. Both test cells were filled with electrolyte 1 according to Example 2.

[0137] First, in the first cycle, the surface layer capacities were determined according to Example 4.

[0138] Figure 8The graph shows the potential in volts of the two test cells when charging the negative electrode as a function of the capacity in [%], relative to the theoretical capacity of the negative electrode. The two curves shown represent averaged results from several experiments with the test cells described above. The solid curve represents the test cell with the graphite electrode and copper discharge element, and the dashed curve represents the test cell with the graphite electrode and nickel discharge element. The test cells were initially charged with a current of 15 mA until a capacity of 125 mAh (Qlad) was reached. They were then discharged at 15 mA until a potential of 2.5 volts was reached. The discharge capacity (Qent) was then determined.

[0139] In the test cell with a graphite electrode and a copper discharge element, the capacitance is 6.7%, and in the test cell with a graphite electrode and a nickel discharge element, it is 7.3%. The capacitance is lower when using a copper discharge element than when using a nickel discharge element.

[0140] To determine the discharge capacities (see Example 4), the two test cells were charged at a rate of C / 2 up to an upper potential of 4.4 volts. They were then discharged at a rate of C / 2 down to a discharge potential of 2.5 volts.

[0141] Figure 9The graph shows mean discharge capacities of the two test cells as a function of the number of cycles. The solid curve represents the test cell with the graphite electrode and copper discharge element, and the dashed curve represents the test cell with the graphite electrode and nickel discharge element. These mean discharge capacities are expressed as a percentage of the nominal capacity [% nominal capacity]. The discharge capacity curves of the two test cells show a smooth, almost linear progression. Only a slight decrease in capacity is observed in both test cells. At cycle 200, the capacities of the two test cells are still approximately 95% (nickel discharge element) and 94% (copper discharge element), respectively.

[0142] Figure 10 shows a photograph of the copper discharge element after the previously described measurement. Figure 9 From this Figure 10It is evident that no corrosion occurs on the copper discharge element during the experiment.

[0143] In electrolyte 1, negative electrodes with a nickel discharge element and negative electrodes with a copper discharge element exhibit low capacitance and good cycle behavior. No corrosion is visible on the copper discharge element after the experiment. Experiment 3: Behavior of copper conductors for the negative electrode in half-cells with electrolyte 5 and electrolyte 6

[0144] Negative electrodes were again produced using graphite as the active material. The electrodes' conductive element consisted of copper in the form of a copper foil.

[0145] The experiments were conducted in half-cells using metallic lithium as the counter and reference electrodes. The working electrode was the graphite electrode under investigation, with a copper separator. One half-cell was filled with electrolyte 5, and the other with electrolyte 6. The half-cells were charged / discharged at a rate of 0.02C up to a potential of 0.03 volts and discharged down to a potential of 0.5 volts. Figure 11 Figure 1 shows the potentials of the respective charging and discharging curves for the fourth cycle in electrolyte 5 and the second cycle in electrolyte 6 of the half-cells, where solid lines represent the charging potentials and dashed lines represent the discharging potentials. The charging and discharging curves exhibit stable, battery-typical behavior. Copper leakage elements are suitable as leakage elements for the negative electrode in electrolytes 5 and 6 and exhibit stable behavior. Experiment 4: Behavior of aluminum conductive elements in half-cell experiments with reference electrolyte and with electrolyte according to the invention 1

[0146] These experiments aimed to investigate the long-term stability of aluminum discharge elements under current stress in the reference electrolyte and electrolyte 1. The experiments were conducted in half-cells using metallic lithium as the counter and reference electrodes. The working electrodes were the aluminum discharge element under investigation, in the form of an aluminum sheet. The half-cells were filled with either a reference electrolyte with the composition LiAlCl₄·1.5SO₂ or electrolyte 1.

[0147] A constant current of 0.1 mA was applied to the half-cell with an aluminum discharge element in reference electrolyte for approximately 300 hours. The dashed lines in Figure 12The graph shows the current (scale on the right) and the resulting potential (scale on the left) over a period of 90 hours. A potential of approximately 3.9 volts was observed throughout this time. After the experiment, the aluminum grounding element was removed from the half-cell and examined.

[0148] In the half-cell with an aluminum grounding element in electrolyte 1, a constant current of 0.1 mA was initially applied. The target potential of the experiment, 5.0 V, was reached after approximately 2 minutes. The current was then reduced to 0.5 µA and successively increased to the following currents every 10 hours: 1 µA, 2 µA, 3 µA, 4 µA, 6 µA, 8 µA, 10 µA, and 12 µA. The solid lines in Figure 12The graph shows the current intensity (scale on the right) and the resulting potential (scale on the left) over a period of 90 hours. After the experiment, the aluminum grounding element was removed from the half-cell and examined.

[0149] Figure 13 The figure shows an example of an aluminum discharge element, which was inserted into the respective half-cell at the beginning of the measurements. Figure 14The aluminum discharge element is shown after the experiment in the half-cell with reference electrolyte. Significant corrosion is visible on the edges and surface of the aluminum sheet after the experiment in the half-cell with reference electrolyte. This corrosion is also reflected in a very large weight loss of 61.5% of the aluminum discharge element. Aluminum is not stable in the reference electrolyte under current load. Figure 15 shows the aluminum discharge element after the experiment in the half-cell with electrolyte 1. No difference is visible on the aluminum sheet compared to the beginning of the measurement; that is, no corrosion is detectable on the discharge element. Aluminum is very stable in the electrolyte 1 according to the invention under current load. Experiment 5 : Behavior of aluminum conductive elements for the positive electrode in test full cells and half cells with electrolyte 1

[0150] To further investigate the aluminum electrodes, they were coated with an active, positive material. Positive electrodes were fabricated using LiNi 0.5 Mn 1.5 O 4 (LNMO) as the active material. LNMO is an active material that can be charged to a high upper potential, for example, 5 volts. The electrodes' electrodes consisted of an aluminum sheet. A half-cell was constructed using a positive electrode and a lithium electrode as the counter electrode and reference electrode. The half-cell was filled with electrolyte 1. To determine the discharge capacities (see Example 4), the half-cells were charged and discharged at a rate of 0.1C up to a potential of 5 volts.

[0151] Figure 16 shows the potentials of the charging curves (solid line) and discharging curves (dashed line) for the first cycle of the half-cell with aluminum discharge element as a function of the capacity.

[0152] The charging and discharging curves show stable, typical battery behavior. Aluminum leakage elements are very stable as leakage elements of the positive electrode in electrolyte 1. Experiment 6 : Behavior of aluminum conductive elements for the positive electrode in test full cells with electrolyte 1

[0153] To further test the stability of aluminum discharge elements, a test cell was constructed with one positive electrode containing nickel manganese cobalt oxide (NMC622) as the active material and an aluminum foil as the discharge element, and two negative electrodes. The negative electrodes contained graphite as the active material and a nickel discharge element. To determine the discharge capacities (see Example 4), the test cell was charged at a rate of 0.1 C up to an upper potential of 4.4 volts. It was then discharged at a rate of 0.1 C down to a discharge potential of 2.8 volts. Figure 17 This shows the discharge capacity over 200 cycles. The test cell exhibits very stable behavior with an almost horizontal capacity curve. This confirms that aluminum conductive elements are very stable as conductive elements for the positive electrode in electrolyte 1. Experiment 7: Behavior of aluminum discharge elements for the positive electrode in combination with copper discharge elements for the negative electrode in full cells with electrolyte 1

[0154] To test the behavior of aluminum electrodes for the positive electrode in combination with copper electrodes for the negative electrode in full cells with electrolyte 1 according to the invention, a full cell with 24 negative and 23 positive electrodes was constructed. The positive electrodes contained nickel manganese cobalt oxide (NMC622) as the active material and an aluminum foil as the electrode. The negative electrodes contained graphite as the active material and a copper foil as the electrode.

[0155] To determine the discharge capacities (see Example 4), the full cell was charged at a rate of 0.1 C to various upper potentials of 4.3 V and 4.6 V. The charging capacity was limited to 50% of the theoretical cell capacity. Discharge was then carried out at a rate of 0.1 C to a discharge potential of 2.8 volts. Figure 18 The graph shows the discharge capacity curve normalized to the maximum capacity of the full cells with an upper potential of 4.3 V and the full cells with an upper potential of 4.6 V over 10 cycles. The full cells exhibit very stable behavior with an almost horizontal capacity curve, even when measured at a higher upper potential. This confirms that aluminum leakage elements for the positive electrode, in combination with copper leakage elements for the negative electrode, are very stable in full cells with electrolyte 1. Experiment 8: Behavior of aluminum conductive elements for the positive electrode in half-cells with electrolyte 5

[0156] Positive electrodes were fabricated using nickel manganese cobalt oxide (NMC811) as the active material. The discharge element of the positive electrodes consisted of aluminum in the form of an aluminum foil. The experiments were conducted in half-cells with metallic lithium as the counter and reference electrode. The working electrode was the positive electrode under investigation, which had an aluminum discharge element. The half-cell was filled with electrolyte 5. To determine the discharge capacities (see Example 4), the half-cells were charged / discharged at a rate of 0.02 C up to a potential of 3.9 volts and discharged down to a potential of 3 volts.

[0157] Figure 19 shows the potential during charging and for the second cycle of the half-cell with aluminum leakage element as a function of capacity.

[0158] The charging and discharging curves show stable, typical battery behavior. Aluminum leakage elements are very stable as leakage elements of the positive electrode in the electrolyte 5. Experiment 8: Investigation of electrolytes 1, 3, 4 and 5

[0159] To investigate electrolytes 1, 3, 4, and 5, various experiments were conducted. Firstly, the capacitances of the surface layer of electrolytes 1 and 3 and the reference electrolyte were determined, and secondly, the discharge capacitances in electrolytes 1, 3, 4, and 5 were determined.

[0160] To determine the surface layer capacity, three test cells were filled with electrolytes 1 and 3 described in Example 2 and the reference electrolyte described in Example 1. The three test cells contained lithium iron phosphate as the active material of the positive electrode.

[0161] Figure 20The graph shows the potential in volts of the test cells when charging the negative electrode as a function of the capacity, which is referenced to the theoretical capacity of the negative electrode. The two curves shown represent averaged results from several experiments with the test cells described above. First, the test cells were charged with a current of 15 mA until a capacity of 125 mAh (Qlad) was reached. Then, the test cells were discharged with 15 mA until a potential of 2.5 volts was reached. The discharge capacity (Qent) was then determined.

[0162] The absolute capacity losses are 7.58% and 11.51% for electrolytes 1 and 3, respectively, and 6.85% for the reference electrolyte. The capacity for the formation of the cover layer is somewhat higher for both electrolytes according to the invention than for the reference electrolyte. Values ​​in the range of 7.5% to 11.5% for the absolute capacity losses are good results in combination with the possibility of using high-voltage cathodes up to 5 volts. For the discharge experiments, four test cells according to Example 3 were filled with the electrolytes 1, 3, 4, and 5 described in Example 2. The test cells had lithium nickel manganese cobalt oxide (NMC) as the active material of the positive electrode. To determine the discharge capacities (see Example 4), the test cells were charged with a current of 15 mA up to a capacity of 125 mAh. The discharge then took place with a current of 15 mA up to a discharge potential of 2.5 volts.

[0163] Figure 21This shows the potential profile during discharge versus the amount of charge discharged in % [% of maximum charge (discharge)]. All test cells show a flat discharge curve, which is necessary for the proper operation of a battery cell. Experiment 9: Determination of the conductivities of electrolytes 1, 3, 4, 5 and 6

[0164] To determine the conductivity, electrolytes 1, 3, 4, 5, and 6 were prepared with varying concentrations of compounds 1, 3, 4, 5, and 6. For each concentration of the different compounds, the conductivities of the electrolytes were determined using a conductive measurement method. After tempering, a four-electrode sensor was held in contact with the solution and measurements were taken within a range of 0.02–500 mS / cm.

[0165] Figure 22The graph shows the conductivities of electrolytes 1, 4, and 6 as a function of their respective concentrations. Electrolyte 1 exhibits a maximum conductivity of approximately 37.9 mS / cm at a concentration of compound 1 of 0.6 mol / L to 0.7 mol / L. In comparison, conventional organic electrolytes, such as LP30 (1 M LiPF6 / EC-DMC (1:1 wt.)), have a conductivity of only about 10 mS / cm. Electrolyte 4 reaches a maximum conductivity of 18 mS / cm at a concentration of 1 mol / L. Electrolyte 6 shows a maximum conductivity of 11 mS / cm at a concentration of 0.6 mol / L.

[0166] The Figure 23The graph shows the conductivities of electrolytes 3 and 5 as a function of their concentrations. Electrolyte 5 reaches a maximum conductivity of 1.3 mS / cm at a conducting salt concentration of 0.8 mol / L. Electrolyte 3 exhibits its highest conductivity of 0.5 mS / cm at a conducting salt concentration of 0.6 mol / L. Although electrolytes 3 and 5 show lower conductivities, charging and discharging a test half-cell, as described in Experiment 3, or a test full cell, as described in Experiment 8, is readily achievable. Experiment 10: Low temperature behavior

[0167] To determine the low-temperature behavior of electrolyte 1 compared to the reference electrolyte, two test cells were prepared according to Example 3. One test cell was filled with reference electrolyte of the composition LiAlCl₄·6SO₂, and the other test cell with electrolyte 1. The test cell with the reference electrolyte contained lithium iron phosphate (LEP) as the active material, while the test cell with electrolyte 1 contained lithium nickel manganese cobalt oxide (NMC) as the active material of the positive electrode. The test cells were charged at 20°C to 3.6 volts (LEP) and 4.4 volts (NMC), respectively, and discharged at the respective temperature under investigation to 2.5 volts. The discharge capacity achieved at 20°C was assessed as 100%. The discharge temperature was decreased in 10 K increments. The achieved discharge capacity was described as a percentage of the discharge capacity at 20°C.Since the low-temperature discharges are almost independent of the active materials used for the positive and negative electrodes, the results can be generalized to all combinations of active materials. Table 5 shows the results.

[0168] The test cell with electrolyte 1 exhibits very good low-temperature performance. At -20°C, 82% of the capacity is still achieved, and at -30°C, 73%. Even at a temperature of -40°C, 61% of the capacity can still be discharged. In contrast, the test cell with the reference electrolyte only shows a discharge capability down to -10°C, achieving a capacity of 21%. At lower temperatures, the cell with the reference electrolyte can no longer be discharged. Table 5: Discharge capacities depending on temperature temperature Electrolyte discharge capacity 1 Discharge capacity of the reference electrolyte 20°C 100% 100% 10°C 99% 99% 0°C 95% 46% -10°C 89% 21% -20°C 82% n / a -30°C 73% n / a -35°C 68% n / a -40°C 61% n / a

Claims

1. Rechargeable battery cell (2, 20, 40) containing an active metal, at least one positive electrode (4, 23, 44) with a discharge element (26), at least one negative electrode (5, 22, 45) with a discharge element (27), a housing (1, 28) and an electrolyte, wherein the discharge element (26) of the positive electrode (4, 23, 40) and the discharge element (27) of the negative electrode (5, 22, 45) are formed independently from each other from a material selected from the group formed by aluminum and copper, and wherein the electrolyte is based on SO2 and contains at least a first conducting salt which has the formula (I), wherein - M is a metal which is selected from the group which is formed by alkali metals, earth alkali metals, metals from group 12 of the periodic table of the elements and aluminum; - x is an integer from 1 to 3; - the substituents R1, R2, R3 and R4 are selected independently from each other from the group formed by C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C10 cycloalkyl,C6-C14 aryl andC5-C14 heteroaryl; wherein - optionally at least two of the substituents R1, R2, R3 and R4 are bridged to each other to form a chelate ligand; and - optionally at least one of the substituents R1, R2, R3 and R is substituted by at least one fluorine atom and / or by at least one chemical group, wherein the chemical group is selected from the group formed by C1-C4alkyl, C2-C4alkenyl, C2-C4alkynyl, phenyl and benzyl; wherein Z is aluminum or boron.

2. Rechargeable battery cell (2, 20, 40) according to claim 1, in which the discharge element (26) of the positive electrode (4, 23, 44) is made of aluminum.

3. Rechargeable battery cell (2, 20, 40) according to claim 1 or 2, in which the discharge element (27) of the negative electrode (5, 22, 45) is made of copper.

4. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the discharge element (26) of the positive electrode (4, 23, 44) and / or the discharge element (27) of the negative electrode (5, 22, 45) is formed - either to be planar in the form of a metal sheet, a metal foil, preferably with a perforated or net-like structure, or a metal-coated plastic foil, or - three-dimensional in the form of a porous metal structure, in particular in the form of a metal foam (18).

5. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the electrolyte is oxidation stable at least up to an upper potential of 4.0 Volt, preferably at least up to an upper potential of 4.2 Volt, further preferably at least up to an upper potential of 4.4 Volt, further preferably at least up to an upper potential of 4.6 Volt, further preferably at least up to an upper potential of 4.8 Volt and most preferably at least up to an upper potential of 5.0 Volt.

6. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the substituents R1, R2, R3 and R4 of the first conducting salt are selected independently of each other from the group formed by - C1-C6 alkyl; preferably C2-C4 alkyl; most preferably the alkyl groups 2-propyl, methyl and ethyl; - C2-C6 alkenyl; preferably C2-C4 alkenyl; most preferably the alkenyl groups ethenyl and propenyl; - C2-C6alkynyl; preferably C2-C4alkynyl; - C3-C6 cycloalkyl; - phenyl; and - C5-C7 heteroaryl.

7. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, wherein at least one of the substituents R1, R2, R3 and R4 of the first conducting salt is a CF3group.

8. Rechargeable battery cell (2, 20, 40) according to any one of claims 1 to 6, in which the first conducting salt is selected from the group formed by 9. Rechargeable battery cell (2, 20, 40) according to any one of claims 1 to 6, in which the first conducting salt has the following formula 10. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, wherein the electrolyte contains at least one second conducting salt differing from the first conducting salt according to formula (I).

11. Rechargeable battery cell (2, 20, 40) according to claim 10, in which the second conducting salt of the electrolyte is an alkali metal compound, in particular a lithium compound, selected from the group formed by an aluminate, in particular lithium tetrahalogenoaluminate, a halide, an oxalate, a borate, a phosphate, an arsenate and a gallate.

12. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the electrolyte contains at least one additive.

13. Rechargeable battery cell (2, 20, 40) according to claim 12, in which the additive of the electrolyte is selected from the group formed from vinylene carbonate and its derivatives, vinylethylene carbonate and its derivatives, methylethylene carbonate and its derivatives, lithium(bisoxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium oxalate, 2-vinylpyridine, 4-vinylpyridine, cyclic exomethylene carbonates, sulfones, cyclic and acyclic sulfonates, acyclic sulfites, cyclic and acyclic sulfinates, organic esters, inorganic acids, acyclic and cyclic alkanes, which acyclic and cyclic alkanes have a boiling point at 1 bar of at least 36° C, aromatic compounds, halogenated cyclic and acyclic sulfonylimides, halogenated cyclic and acyclic phosphate esters, halogenated cyclic and acyclic phosphines, halogenated cyclic and acyclic phosphites, halogenated cyclic and acyclic phosphazenes, halogenated cyclic and acyclic silylamines, halogenated cyclic and acyclic halogenated esters, halogenated cyclic and acyclic amides, halogenated cyclic and acyclic anhydrides and halogenated organic heterocycles.

14. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the electrolyte has the composition (i) 5 to 99.4 wt% sulfur dioxide, (ii) 0.6 to 95 wt% of the first conducting salt, (iii) 0 to 25 wt.% of the second conducting salt, and (iv) 0 to 10 wt.% of the additive, based on the total weight of the electrolyte composition.

15. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the material quantity concentration of the first conducting salt is in the range from 0.01 mol / I to 10 mol / l, preferably from 0.05 mol / I to 10 mol / l, further preferably from 0.1 mol / I to 6 mol / l and most preferably from 0.2 mol / I to 3.5 mol / I based on the total volume of the electrolyte.

16. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the electrolyte contains at least 0.1 mol SO2, preferably at least 1 mol SO2, further preferably at least 5 mol SO2, further preferably at least 10 mol SO2 and most preferably at least 20 mol SO2 per mol of conducting salt.

17. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the active metal is - an alkali metal, in particular lithium or sodium; - an earth alkali metal, in particular calcium; - a metal of group 12 of the periodic table, in particular zinc; or aluminum.

18. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the positive electrode (4, 23, 44) contains, as active material, at least one compound which preferably has the composition AxM'yM"z0a, wherein - A is at least one metal which is selected from the group which is formed by the alkali metals, the earth alkali metals, the metals of group 12 of the periodic table or aluminum; - M' is at least one metal selected from the group formed by the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn; - M" is at least one element selected from the group formed by the elements of groups 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 of the periodic table of elements; - x and y are numbers greater than 0 independently of each other; - z is a number greater than or equal to 0; and - a is a number greater than 0.

19. Rechargeable battery cell (2, 20, 40) according to claim 18, in which the compound has the composition LixNiy1Mny2CozOa, wherein x, y1and y2 are numbers greater than 0 independently of each other, z is a number greater than or equal to 0, and a is a number greater than 0.

20. Rechargeable battery cell (2, 20, 40) according to claim 18, in which the compound has the composition AxM'yM"1z1M"2z2O4, wherein - M"1 is selected from the group formed by the elements of groups 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 of the periodic table of elements; - M"2 is the element phosphorus; - x and y are numbers greater than 0 independently of each other; - z1 is a number greater than 0; and - z2 has the value 1.

21. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the positive electrode (4, 23, 44) contains at least one metal compound selected from the group formed by a metal oxide, a metal halide and a metal phosphate, wherein the metal of the metal compound is preferably a transition metal of atomic numbers 22 to 28 of the periodic table of elements, in particular cobalt, nickel, manganese or iron.

22. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the positive electrode (4, 23, 44) contains at least one metal compound which has the chemical structure of a spinel, a layered oxide, a conversion compound or a polyanionic compound.

23. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the negative electrode (5, 22, 45) is an insertion electrode which preferably contains carbon as an active material, in particular in the modification graphite.

24. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, in which the positive electrode (4, 23, 44) and / or the negative electrode (5, 22, 45) contains at least one binder, preferably a fluorinated binder, in particular a polyvinylidene fluoride and / or a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, or a binder consisting of a polymer constructed from monomer structural units of a conjugated carboxylic acid or from the alkali, earth alkali or ammonium salt of this conjugated carboxylic acid or of a combination thereof, or a binder consisting of a polymer based on monomeric styrene and butadiene structural units, or a binder from the group of carboxymethyl celluloses, wherein the binder is preferably present in a concentration of at most 20 wt.%, further preferably at most 15 wt.%, further preferably at most 10 wt.%, further preferably at most 7 wt.%, further preferably at most 5 wt.% and most preferably at most 2 wt.%, based on the total weight of the positive electrode or the negative electrode.

25. Rechargeable battery cell (2, 20, 40) according to any one of the preceding claims, which comprises several negative electrodes (5, 22, 45) and at least one, preferably several positive electrodes (4, 23, 44) which are arranged alternately stacked in the housing (1, 28), wherein the positive electrodes (4, 23, 44) and the negative electrodes (5, 22, 45) are preferably electrically separated from each other by separators (11, 21, 13).