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. 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 of the cell and participate in electrochemical processes there. 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. Rechargeable battery cells containing lithium as the active metal are also called lithium-ion cells.The energy density of these lithium-ion cells can be increased either by increasing the specific capacity of the electrodes or by increasing the cell voltage.

[0004] 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 material can be inserted and removed during operation of the lithium-ion cell. This means that the electrode processes can take place not only on the surface of the electrodes but also within the crystal structure itself. During charging of the lithium-ion cell, the ions of the active metal are removed from the positive electrode and inserted into the negative electrode. The reverse process occurs during discharging of the lithium-ion cell.

[0005] 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.

[0006] Lithium-ion cells known from the prior art contain an electrolyte consisting of a conducting salt dissolved in an organic solvent or solvent mixture. 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.

[0007] In addition to 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.

[0008] 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.

[0009] 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.

[0010] 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 not only contains SO₂ 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 can form 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. This eliminates the safety risks associated with the flammability of the electrolyte.

[0011] Examples of SO2-based electrolytes are disclosed in WO 2020 / 013667 A1 and WO 2021 / 006704 A1.

[0012] 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 LiAl-Cl₄·3SO₂ electrolyte.

[0013] 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.

[0014] For both lithium-ion cells with organic electrolyte solutions and rechargeable battery cells with an SO₂-based electrolyte, the choice of binder for the positive and negative electrodes is crucial. Binders are intended to improve the mechanical and chemical stability of the electrodes. The formation of deposits on the negative electrode, and thus the deposit capacity in the first cycle, should be minimized, thereby increasing the battery cell's lifespan. This binder must be stable with respect to the electrolyte used and maintain its stability over a long period, even if, during charging and discharging cycles, the active metal—in the case of a lithium cell, lithium—is deposited as a metallic material and comes into contact with the binder in the event of malfunctions. If the binder reacts with the metal, the result is a destabilization of the electrode's mechanical structure.Binders in the electrode influence the wettability of the electrode surface. If wettability is impaired, high resistances within the rechargeable battery cell result, leading to operational problems. An important aspect in selecting the binder is the shape of the electrode element. Electrode elements can be planar, for example, in the form of a thin metal sheet or foil, or three-dimensional, such as a porous metal structure like a metal foam. A three-dimensional porous metal structure is porous enough that the active material of the electrode can be incorporated into the pores. With planar electrode elements, the active material is applied to the surface of the front and / or back of the element. Depending on the shape of the electrode element, there are different requirements for the binder.Adhesion to the electrode element must be sufficient. When selecting the binder and its mass fraction within the electrode, a compromise often has to be found between mechanical stabilization on the one hand and improving the electrochemical properties of the electrode on the other.

[0015] For example, the authors of the article (hereinafter referred to as [V3]) report: "Effects of Styrene-Butadiene Rubber / Carboxymethylcellulose (SBR / CMC) and Polyvinylidene Difluoride (PVDF) Binders on Low Temperature Lithium Ion Batteries" Jui-Pin Yen, Chia-Chin Chang, Yu-Run Lin, Sen-Thann Shen and Jin-Long Honga Journal of The Electrochemical Society, 160 (10) A1811-A1818 (2013) Investigations of graphite-based anodes with the binders SBR / CMC or PVDF in an organic electrolyte solution with LiPF 6 as a conducting salt (1M) in ethylene carbonate (EC) / diethyl carbonate (DEC) (v / v=1:1). They conclude that the electrodes with the PVDF binder have lower resistance, a better discharge rate and better cycle stability compared to the electrodes with SBR / CMC binder mixture.

[0016] US patent 2015 / 0093632 A1 (hereinafter referred to as [V4]) discloses an SO₂-based electrolyte with the composition LiAlCl₄ * SO₂. The electrolyte preferably contains lithium tetrahaloaluminate, and more preferably lithium tetrachloroaluminate (LiAlCl₄), as the conducting salt. The positive and negative electrodes are unusually thick and feature a discharge element with a three-dimensional porous metal structure. To increase the starting capacity and improve the mechanical and chemical stability of the negative and positive electrodes, it is proposed to use a binder A, which consists 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, such as...to use lithium polyacrylate (LiPAA), or a binder B consisting of a polymer based on monomeric styrene and butadiene structural units, or a mixture of binder A and B.

[0017] WO 2020 / 221564 (hereinafter referred to as [V5]) also discloses an SO₂-based electrolyte with, among other things, LiAlCl₄ as a conducting salt in combination with a sulfur-doped active material for the positive electrode. Fluorinated binders, e.g., vinylidene fluoride (THV) or polyvinylidene fluoride (PVDF), or salts of polyacrylic acid, e.g., lithium polyacrylate (LiPAA), or binders made from a polymer based on monomeric styrene and butadiene structural units, or binders from the carboxymethylcellulose group are proposed as binders for the negative electrode and for the positive electrode, which preferably has a conductor element with a three-dimensional porous metal structure. For the positive electrode, THV and PVDF have proven particularly suitable.

[0018] One disadvantage, which also occurs with these SO₂-based electrolytes, is that any hydrolysis products formed in the presence of residual water can react with the cell components of the rechargeable battery cell, leading to the formation of undesirable byproducts. Therefore, when manufacturing such rechargeable battery cells with an SO₂-based electrolyte, care must be taken to minimize the residual water content in the electrolyte and the cell components.

[0019] Another problem with SO2-based electrolytes is that many conducting salts, especially those known for organic lithium-ion cells, are not soluble in SO2. Table 1: Solubilities of various conducting salts in SO₂ Conductive salt Solubility / mol / L in SO 2 Conductive salt Solubility / mol / L in SO 2 LiF 2,1·10 -3< LiPF 6 1,5·10 - 2< LiBr 4.9·10 -3< LiSbF 6 2.8·10 -4< Li2SO4 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<

[0020] 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 1). 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.

[0021] 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 SO2-based electrolytes that, compared to rechargeable battery cells known from the prior art, Electrodes with inert binders that do not react with the SO₂-based electrolyte, are stable even at higher charging potentials, do not accelerate oxidative electrolyte degradation, and do not impair the reactions for coating formation; a binder that allows the production of electrodes with good mechanical stability; a binder that, together with an active material of the electrodes, can be evenly distributed or applied to the discharge element of the respective electrode and enables good electrical bonding of the active material to the discharge element of the respective electrode; good wettability of the electrodes with the electrolyte; and the lowest possible price and high availability, especially for large batteries or batteries with widespread use.has a wide electrochemical window, so that no oxidative electrolyte decomposition occurs at the positive electrode; 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 further operation; contains an SO₂-based electrolyte, which has good solubility for conducting salts and is therefore a good ionic conductor and electronic insulator, so that ion transport can be facilitated and self-discharge can be kept to a minimum; contains an SO₂-based electrolyte that is also inert to other components of the rechargeable battery cell, such as separators, electrode materials and cell packaging materials; is robust against various abuses, such as electrical, mechanical or thermal; has improved electrical performance characteristics, in particular a high energy density;It exhibits improved overcharge and deep discharge capabilities, reduced self-discharge, and increased lifespan, particularly a high number of usable charge and discharge cycles.

[0022] 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.

[0023] This problem is solved by a rechargeable battery cell with the features of claim 1. Claims 2 to 21 describe advantageous further developments of the rechargeable battery cell according to the invention.

[0024] A rechargeable battery cell according to the invention comprises an active metal, at least one positive electrode with a planar grounding element, at least one negative electrode with a planar grounding element, a housing, and an SO₂-based electrolyte containing a first conducting salt. The positive and / or negative electrodes contain at least one first binder and at least one second binder. The first binder consists of a polymer based on monomeric styrene and butadiene structural units. The second binder is selected from the group of carboxymethylcelluloses.

[0025] In developing this battery cell according to the invention, the applicant encountered a number of difficult problems related to the use of the SO₂-based electrolyte and the use of planar electrodes. To distribute the active material, together with the respective binder or a combination of binders, as uniformly as possible on the planar electrode, a homogeneous mixture of the components must be produced with a solvent. This homogeneous mixture must be easy to apply to the planar electrode. If these conditions are not met, significant problems arise in the production of a mechanically stable electrode.In the case of the rechargeable battery cell according to the invention, these problems were solved because a homogeneous mixture could be produced from the first and second binders together with the active material, and this homogeneous mixture could be easily applied to the planar conductive element of the respective electrode. Styrene-butadiene rubber (SBR) can be used as the first binder in particular. Carboxymethylcellulose (CMC) is used as the second binder in particular.

[0026] 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 the active material of the respective electrode to the external circuit. For this purpose, the lead element is in electronic contact with the active material involved in the electrode reaction of the electrode. The lead element is planar, i.e., in an approximately two-dimensional embodiment.

[0027] 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. 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 is significantly lower than that of 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, no reduction in vapor pressure may occur during the production of the electrolyte according to the invention.In the latter case, it is preferred that the electrolyte according to the invention is produced at low temperature or under pressure. The electrolyte can also contain several conducting salts which differ from one another in their chemical structure.

[0028] A rechargeable battery cell with such an electrolyte has the advantage that the primary conducting salt it contains exhibits high 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 most 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 decomposition within the operating potentials.in the range between the charging cut-off voltage and the discharging cut-off voltage of both electrodes of the rechargeable battery cell. This allows rechargeable battery cells according to the invention to 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.

[0029] 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. Positive electrode

[0030] 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.

[0031] 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. It is essential that the binding agent of the positive electrode does not impair the good electrical bonding of the active material to the planar grounding element. The use of the first and second binding agents ensures good electrical bonding of the active material to the planar grounding element of the positive electrode, which is maintained even during operation within the battery.

[0032] 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.

[0033] 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.

[0034] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the active material has the following composition:

[0035] A x M' y M" z O a. In this composition A x M' y M" z O a, there is / are 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.

[0036] A is preferably the metal lithium, i.e. the compound can have the composition Li x M' y M" z O a.

[0037] 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. 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, one a metal M" 1< and the other phosphorus as M" 2< , then the following applies to the index z: z=z1+z2, where z1 and z2 represent the indices of the metal M" 1< and of the phosphorus (M" 2< ).The indices x, y, z, and a must be chosen such that charge neutrality prevails within the composition. Examples of compounds where A comprises lithium, M" a metal M"<, and phosphorus as M"< are lithium iron manganese phosphates LixFeyMnz1Pz2O4 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 as M"1 and sulfur as M"2. Examples of such compounds are lithium iron fluorosulfates LixFeyFz1Sz2O4 with A = Li, M' = Fe, M"1 = F, and M"2 = P.

[0038] 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. n Ickel m angan cCobalt oxides that exhibit the structure of layered oxides. Examples of these active materials made from 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 0.7 Mn 0.15 Co 0.15 O 2 , LiNi 0.72 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 0.25 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.

[0039] 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 yM " 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.

[0040] 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). LiCoMnO 4 can be used to produce positive electrodes for rechargeable battery cells with a cell voltage of over 4.6 volts. 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.

[0041] 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

[0042] 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.

[0043] In a further advantageous embodiment, the compound has the composition A x M' y M" z1 M" z2 O 4, where M" is phosphorus and z2 has the value 1. The compound with the composition Li x M' y M" z1 M" 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 (LiFePO 4) or lithium iron manganese phosphates (Li(Fe y Mn z )PO 4). An example of a lithium iron manganese phosphate is the phosphate with the composition Li(Fe 0.3 Mn 0.7 )PO 4. Lithium metal phosphates of other compositions can also be used for the battery cell according to the invention.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The battery cell according to the invention has a positive electrode with a planar discharge element. This means that the positive electrode comprises a discharge element in addition to the active material. This discharge element serves to enable the necessary electronically conductive connection of the active material of the positive electrode. For this purpose, the discharge element is in contact with the active material involved in the electrode reaction of the positive electrode. This planar discharge element is preferably a thin metal sheet or a thin metal foil. The thin metal foil can have a perforated or mesh-like structure. The planar discharge element can also consist of a metal-coated plastic film. These metal coatings have a thickness in the range of 0.1 µm to 20 µm.The active material of the positive electrode is preferably applied to the surface of the thin metal sheet, thin metal foil, or metal-coated plastic film. The active material can be applied to the front and / or back of the planar discharge element. Such planar discharge elements have a thickness in the range of 5 µm to 50 µm. A thickness of the planar discharge element in the range of 10 µm to 30 µm is preferred. When using planar discharge elements, the positive 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 at most 200 µm, preferably at most 150 µm, and particularly preferably at most 100 µm.The area-specific capacitance of the positive electrode with respect to the coating of one side preferably has at least 0.5 mAh / cm² when using a planar discharge element, with the following values ​​in this order being further preferred: 1 mAh / cm², 3 mAh / cm², 5 mAh / cm², 10 mAh / cm², 15 mAh / cm², 20 mAh / cm². 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 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.

[0048] 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.

[0049] In a further advantageous embodiment of the battery cell according to the invention, the positive electrode comprises at least one additional binder that differs from the first and second binders. This additional binder is preferably a fluorinated binder, in particular a polyvinylidene fluoride (abbreviation: PVDF) and / or a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, or 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.

[0050] The additional binder in the form of the polymer can be lithium polyacrylate (LiPAA). The positive electrode can also contain two further binders that differ from the first and second binders. In this case, the positive electrode preferably contains a third binder in the form of the fluorinated binder, in particular polyvinylidene fluoride (abbreviated PVDF) and / or the terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and a fourth binder in the form of the 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. A problem with the use of the fluorinated binder is that it is often only soluble in highly flammable, environmentally harmful organic solvents.The production of positive electrodes with a fluorinated binder requires complex equipment that accommodates the use of these solvents. Explosion protection, environmental protection, and the protection of exposed personnel are particularly problematic in this context. The applicant had to consider these issues when developing this advantageous further development of the battery cell according to the invention.

[0051] During the development of the rechargeable battery cell of the present patent application, the applicant found that determining the optimal concentration of the first, second, third, and / or fourth binder relative to the total weight of the positive electrode was difficult: A concentration that was too low in the positive electrode led to poor handling of the manufactured positive electrode, since, for example, binder-free electrodes do not adhere to the discharge element, which can lead to particle release of the active material and consequently to the unusability of the manufactured rechargeable battery cell. Conversely, a concentration of binder that was too high negatively affected the energy density of the rechargeable battery cell. This is because the weight of the binder reduces the energy density.Furthermore, an excessively high binder concentration can lead to poor wetting of the positive electrode by the SO₂-based electrolyte. Therefore, the concentration of all binders in the positive electrode is preferably 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%, more preferably at most 2 wt%, more preferably at most 1 wt%, and most preferably at most 0.5 wt%, based on the total weight of the positive electrode. The concentration of all binders in the positive electrode is preferably in the range between 0.05 wt% and 20 wt%, more preferably in the range between 0.5 wt% and 10 wt%, and most preferably in the range between 0.5 wt% and 5 wt%.The concentrations mentioned above enable good wetting of the positive electrode with the SO2-based electrolyte, good handling of the positive electrode, and good energy density of the rechargeable battery cell with such a positive electrode. electrolyte

[0052] The first conducting salt has formula (I), where M is a metal selected from the group consisting of alkali metals, alkaline earth metals, group 12 metals of the periodic table of elements, and aluminum; x is an integer from 1 to 3; the substituents R1<, R2<, R3<, and R4< are independently selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C10 cycloalkyl, C6-C14 aryl, and C5-C14 heteroaryl; and where Z is aluminum or boron.

[0053] 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.

[0054] For the purposes of the present invention, the term "C2-C10 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.

[0055] For the purposes of the present invention, the term "C2-C10 alkynyl" encompasses 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, iso-butynyl, 1-pentynyl, 1-hexynyl, 1-heptynyl, 1-octynyl, 1-nonynyl, 1-decinyl, and the like.

[0056] For the purposes of the present invention, the term "C3-C10 cycloalkyl" encompasses cyclic, saturated hydrocarbon groups with three to ten carbon atoms. This includes, in particular, cyclopropyl, cyclobutyl, cyclopentyl, cyclohepyl, cyclohepyl, cyclocononyl, and cyclodecanyl.

[0057] 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).

[0058] 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).

[0059] In a further advantageous embodiment of the rechargeable battery cells, the substituents R 1< , R 2< , R 3< and R 4< of the first conducting salt with formula (I) 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.

[0060] 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.

[0061] 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.

[0062] In the case of 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 at least

[0063] exhibit a C-C triple bond. This includes, in particular, ethynyl, 1-propynyl, 2-propynyl, 1-n-butynyl, 2-n-butynyl, iso-butynyl, 1-pentynyl, and 1-hexynyl. C2-C4 alkynyls are preferred among these.

[0064] 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.

[0065] In the case of this advantageous embodiment of the SO2-based electrolyte, the term "C5-C7 heteroaryl" includes phenyl and naphthyl.

[0066] 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.

[0067] 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.

[0068] In a further advantageous embodiment of the rechargeable battery cell, the first conducting salt according to formula (I) is selected from the group formed by

[0069] 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. 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.

[0070] 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, sultones, 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.

[0071] 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.

[0072] As mentioned previously, the electrolyte can contain not only a first conducting salt and a second conducting salt, but also several first 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.

[0073] 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%.

[0074] 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.

[0075] 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.

[0076] 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

[0077] 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. Negative electrode

[0078] 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.

[0079] 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 ).

[0080] 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).

[0081] 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 (MnO₂), iron oxides (FeO₂), cobalt oxides (CoO₂), nickel oxides (NiO₂), copper oxides (CuO₂), 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. It is essential that the binding agent of the negative electrode does not impair the good electrical connection of one of the aforementioned active materials to the planar discharge element.The use of the first and second binders enables good electrical bonding of the aforementioned active materials to the planar conductive element of the negative electrode, which is also maintained during operation within a battery.

[0082] In a further advantageous embodiment of the rechargeable battery cell according to the invention, the negative electrode comprises a metal, in particular metallic lithium.

[0083] A further advantageous embodiment of the rechargeable battery cell according to the invention provides that the negative electrode is porous, wherein the porosity is preferably 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.

[0084] The individual pores of the negative electrode can preferably be completely filled with the electrolyte during operation.

[0085] The battery cell according to the invention provides that the negative electrode has a planar discharge element. This means that the negative electrode comprises a planar discharge element in addition to the active material or insertion material. This planar discharge element is preferably a thin metal sheet or a thin metal foil. The thin metal foil preferably has a perforated or mesh-like structure. The planar discharge element can also be a metal-coated plastic film. This metal coating has a thickness in the range of 0.1 µm to 20 µm. The active material of the negative electrode is preferably applied to the surface of the thin metal sheet, the thin metal foil, or the metal-coated plastic film. The active material can be applied to the front and / or the back of the planar discharge element. Such planar discharge elements have a thickness in the range of 5 µm to 50 µm.A thickness of the planar discharge element in the range of 10 µm to 30 µm is preferred. When using planar discharge elements, the negative 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 at most 200 µm, preferably at most 150 µm, and particularly preferably at most 100 µm. The area-specific capacitance of the negative electrode, based on the coating of one side, preferably has at least 0.5 mAh / cm² when using a 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. If the discharge 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 electrode, i.e.The electrode loading, 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. The maximum electrode loading, 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.

[0086] In a further advantageous embodiment of the battery cell according to the invention, the negative electrode comprises at least one additional binder that differs from the first and second binders. This additional binder is preferably a fluorinated binder, in particular a polyvinylidene fluoride (abbreviation: PVDF) and / or a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, or 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.

[0087] The additional binder in the form of the polymer can be lithium polyacrylate (LiPAA). The negative electrode can also contain two further binders that differ from the first and second binders. In this case, the negative electrode preferably contains a third binder in the form of the fluorinated binder, in particular polyvinylidene fluoride (abbreviated PVDF) and / or the terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and a fourth binder in the form of the 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.

[0088] The use of fluorinated binders presents the problem that they are often only soluble in highly flammable, environmentally harmful organic solvents. Manufacturing negative electrodes with a fluorinated binder requires complex equipment designed to handle these solvents. Explosion protection, environmental protection, and the protection of exposed personnel are particularly problematic. The applicant had to consider these issues when developing this advantageous embodiment of the battery cell according to the invention.During the development of the rechargeable battery cell of the present patent application, the applicant found that determining the optimal binder concentration relative to the total weight of the negative electrode was difficult: A concentration that was too low in the negative electrode led to poor handling of the manufactured negative electrode, as, for example, binder-free electrodes do not adhere to the discharge element, which can lead to particle release of the active material and consequently to the unusability of the manufactured rechargeable battery cell. Conversely, a binder concentration that was too high negatively affected the energy density of the rechargeable battery cell. The weight of the binder reduces the energy density. Furthermore, an excessively high binder concentration could result in poor wetting of the negative electrodes by the SO₂-based electrolyte.Therefore, the concentration of all binders in the negative electrode is preferably 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%, more preferably at most 2 wt%, more preferably at most 1 wt%, and most preferably at most 0.5 wt% based on the total weight of the negative electrode. The concentration of all binders in the negative electrode is preferably in the range between 0.05 wt% and 20 wt%, more preferably in the range between 0.5 wt% and 10 wt%, and most preferably in the range between 0.5 wt% and 5 wt%. The aforementioned concentrations enable good wetting of the negative electrode with the SO₂-based electrolyte, good handling of the negative electrode, and a good energy density of a rechargeable battery cell with such a negative electrode.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 (carbon nanotubes, CNTs, carbon (nano)fibers), finely divided graphite, and graphene (nanosheets).

[0089] Structure of the Rechargeable Battery Cell Advantageous further developments 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 development of the rechargeable battery cell according to the invention provides that the rechargeable battery cell comprises several negative electrodes and several high-voltage electrodes, which are arranged alternately stacked in the housing. Here, the positive electrodes and the negative electrodes are preferably electrically separated from each other by separators.

[0090] 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.

[0091] It is also within the scope of the invention that the separator can be designed as a casing, wherein each high-voltage 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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 a detail of the first embodiment. Figure 1Figure 3 shows a second embodiment of the rechargeable battery cell according to the invention in an exploded view; Figure 4 shows a third embodiment of the rechargeable battery cell according to the invention in an exploded view; Figure 5 shows the potential in [V] as a function of the capacity, which is based on the theoretical capacity of the negative electrode, during a coating layer formation, of three test cells with electrodes having different binder combinations and three-dimensional discharge elements and filled with a lithium tetrachloroaluminate electrolyte from Example 1; Figure 6 shows the discharge capacity as a function of the number of cycles of three test cells with electrodes having different binder combinations and three-dimensional discharge elements and filled with the lithium tetrachloroaluminate electrolyte from Example 1;Figure 7: shows the potential in [V] as a function of the capacitance of three half-cells with electrodes having different binder combinations and planar discharge elements, filled with the electrolyte 1 from Example 1; Figure 8: shows the discharge capacity as a function of the number of cycles of two half-cells with electrodes having different binder combinations and planar discharge elements, filled with the electrolyte 1 from Example 1; Figure 9: shows the potential in [V] as a function of the capacitance, relative to the theoretical capacitance of the negative electrode, of three wound cells with electrodes having different binder combinations and planar discharge elements, filled with the electrolyte 1 from Example 1, during charging during a coating layer formation on the negative electrode;Figure 10 shows the discharge capacity as a function of the cycle count of two wound cells with electrodes having different binder combinations and planar discharge elements, filled with electrolyte 1 from Example 1; Figure 11 shows the potential in [V] as a function of the capacitance, relative to the theoretical capacitance of the negative electrode, of three test cells filled with electrolytes 1 and 3 and the lithium tetrachloroaluminate electrolyte from Example 1, during charging during a coating layer formation on the negative electrode; Figure 12 shows the potential profile during discharge in volts [V] as a function of the percentage charge of three test cells filled with electrolytes 1, 3, 4, and 5 from Example 1, containing lithium nickel manganese cobalt oxide (NMC) as the active electrode material;Figure 13 shows the conductivities in [mS / cm] of electrolytes 1 and 4 from Example 1 as a function of the concentration of compounds 1 and 4; and Figure 14 shows the conductivities in [mS / cm] of electrolytes 3 and 5 from Example 1 as a function of the concentration of compounds 3 and 5.

[0097] Figure 1Figure 1 shows a first embodiment of a rechargeable battery cell 20 according to the invention in cross-sectional view. This first embodiment shows an electrode arrangement with a positive electrode 23 and two negative electrodes 22. The electrodes 22 and 23 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 a homogeneous mixture of the active material 24 of the positive electrode 23, a first binder SBR, and a second binder CMC is applied on both sides. The negative electrodes 22 also comprise a discharge element 27 in the form of a planar metal foil onto which a homogeneous mixture of the active material 25 of the negative electrode 22, the first binder SBR, and the second binder CMC is applied on both sides.Alternatively, the planar conductive 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 terminal contacts 31, 32 of the rechargeable battery cell 20.

[0098] Figure 2 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 1 This metal foil has a perforated or net-like structure with a thickness of 20 µm.

[0099] Figure 3Figure 1 shows a second embodiment of the rechargeable battery cell 40 according to the invention in an exploded view. This second embodiment differs from the first embodiment described above in that the positive electrode 44 is enclosed by a casing 13, which serves as a separator. 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 5 The 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.

[0100] Figure 4Figure 1 shows a third embodiment of a rechargeable battery cell 101 according to the invention in an exploded view. The essential structural elements of a battery cell 101 with a wound electrode arrangement are shown. An electrode arrangement 105, wound from a web-like starting material, is located in a cylindrical housing 102 with a cover part 103. The web consists of several layers, including a positive electrode, a negative electrode, and a separator running between the electrodes, which electrically and mechanically insulates the electrodes from each other but is sufficiently porous or ion-conducting to allow the necessary ion exchange.The positive electrode has a discharge element in the form of a planar metal foil, onto which a homogeneous mixture of the active material 24 of the positive electrode 23, a first binder SBR, and a second binder CMC is applied on both sides. The negative electrode also comprises a discharge element in the form of a planar metal foil, onto which a homogeneous mixture of the active material 25 of the negative electrode 22, the first binder SBR, and the second binder CMC is applied on both sides.

[0101] The cavity of the housing 102, insofar as it is not occupied by the electrode arrangement 105, is filled with an electrolyte (not shown). The positive and negative electrodes of the electrode arrangement 105 are connected via corresponding terminals 106 for the positive electrode and 107 for the negative electrode to the terminal contacts 108 for the positive electrode and 109 for the negative electrode, which enable the electrical connection of the rechargeable battery cell 101. Alternatively to the one shown in Figure 4 In addition to the electrical connection of the negative electrode shown using the connecting tab 107 and the connecting contact 109, the electrical connection of the negative electrode can also be made via the housing 102. Example 1 : Production of exemplary embodiments of an SO2-based electrolyte for a battery cell

[0102] The electrolyte LiAlCl₄ × SO₂ used for the experiments described below was prepared according to the process described in patent EP 2 954 588 B1 (hereinafter referred to as [V6]). First, lithium chloride (LiCl₂) was dried under vacuum at 120 °C for three days. Aluminum particles (Al) were dried under vacuum at 450 °C for two days. LiCl₂, 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 electrolyte thus formed had the composition LiAlCl₄ * x SO₂, where x depends on the amount of SO₂ supplied. In the experiments, this electrolyte is referred to as lithium tetrachloroaluminate electrolyte.

[0103] For the experiments described below, five embodiments 1, 2, 3, 4 and 5 of the SO₂-based electrolyte with a conducting salt of formula (I) were prepared (hereinafter referred to as electrolytes 1, 2, 3, 4 and 5). For this purpose, five different first conducting salts of 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"

[0104] These five different, first conducting salts according to formula (I) are subsequently referred to as compounds 1, 2, 3, 4 and 5. 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.

[0105] This resulted in the following compounds 1, 2, 3, 4 and 5 being formed with their respective molecular and structural formulas:

[0106] For purification, compounds 1, 2, 3, 4, and 5 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 spark formation in the SO₂ solution if any traces of water were present.

[0107] Subsequently, compounds 1, 2, 3, 4 and 5 were dissolved in SO2. It was found that compounds 1, 2, 3, 4 and 5 dissolved well in SO2.

[0108] The production of electrolytes 1, 2, 3, 4 and 5 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 and 5 into a pressure flask with a riser tube, 2) Evacuate the pressure flasks, 3) Infuse liquid SO2 and 4) Repeat steps 2 and 3 until the target amount of SO2 has been added.

[0109] The respective concentrations of compounds 1, 2, 3, 4 and 5 in electrolytes 1, 2, 3, 4 and 5 were 0.6 mol / l (mol concentration per 1 liter of electrolyte), unless otherwise described in the experiment description.

[0110] The experiments described below were carried out using the lithium tetrachloroaluminate electrolyte and electrolytes 1, 2, 3, 4 and 5. Example 2: Production of test full cells

[0111] 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, and two binders. The negative electrodes contained graphite as the active material and also two binders. As mentioned in the experiment, the negative electrodes can also contain a conductivity additive. The active material of the positive electrode is named in the respective experiment. Among other things, the aim of the investigations is to confirm the use of different binders or a combination of binders for electrodes with planar conductive elements in a battery cell according to the invention with an SO₂-based electrolyte. Table 2a shows which binders were investigated.Table 2b lists the binder combinations used in the experiments.

[0112] The test cells were each filled with the electrolyte required for the experiments, i.e., either the lithium tetrachloroaluminate electrolyte or electrolytes 1, 2, 3, 4, or 5. For each experiment, several identical test cells were usually prepared, typically two to four. The results presented in the experiments are then mean values ​​obtained from the measurements taken for the identical test cells. Table 2a: Binders investigated binder abbreviation Styrene-butadiene rubber (as an example of the first binder) SBR Carboxymethylcellulose (as an example of the second binder) CMC Polyvinylidene fluoride (as an example of the third binder) PVDF Lithium polyacrylate (as an example of the fourth binder) LiPAA Table 2b: Overview of experiments (% corresponds to wt%) experiment Binder combinations Type of drain element / electrolyte 1 2.0% LiPAA / 2.0% CMC Three-dimensional / Lithium tetrachloroaluminate electrolyte 2.0% LiPAA / 2.0% SBR 2.0% SBR / 2.0% CMC 2. Adhesion 1.0% CMC / 2.0% LiPAA / 1.0% SBR Planar 1.0% SBR / 2.0% CMC 2 Loading 2.0% LiPAA / 2.0% CMC Planar 2.0% SBR / 2.0% CMC 3 3.0% SBR / 1.0% CMC Planar / Electrolyte 1 2.0% SBR / 2.0% CMC 2.0 - 4.0% PVDF 4 Cover layer capacity 2.5% SBR / 1.5% CMC Planar / Electrolyte 1 2.0% SBR / 2.0% CMC 1.0% SBR / 2.0% CMC 4 discharge capacity 2.5% SBR / 1.5% CMC Planar / Electrolyte 1 2.0% SBR / 2.0% CMC 5-7 Investigation of electrolyte properties Electrolyte 1, Electrolyte 3 Electrolyte 4, Electrolyte 5 Example 3: Measurement in test full cells Top layer capacity:

[0113] 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

[0114] 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:

[0115] 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 held 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.

[0116] 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.

[0117] 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.

[0118] Preferably, the battery is charged at a current rate of C / 2 and at a temperature of 22°C. By definition, a charge / discharge rate of 1C charges or discharges the nominal capacity of a cell in one hour. A charge rate of C / 2 therefore means a charging time of 2 hours.

[0119] 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.

[0120] Preferably, the battery is discharged at a current rate of C / 2 and at a temperature of 22°C.

[0121] The discharge capacity is derived from the discharge current and the time until the discharge termination criteria are met. The associated

[0122] Figures show mean values ​​for the discharge capacities as a function of the number of cycles. These mean values ​​of the discharge capacities are often normalized to the maximum capacity achieved in the respective test and are expressed as a percentage of the nominal capacity. experiment 1: Investigations of different binder combinations in test full cells with a three-dimensional discharge element

[0123] Prior art rechargeable batteries with SO₂-based electrolytes mainly use electrodes with a three-dimensional discharge element, e.g., made of nickel foam (see [V5]). A preferred binder for the negative electrode is lithium polyacrylate (LiPAA) (see [V4]). Negative electrodes (NELs) with graphite as the active material and various binder combinations were produced. All electrodes comprised the prior art three-dimensional discharge element in the form of nickel foam. The binder combinations are: 2 wt% LiPAA / 2 wt% CMC, 2 wt% LiPAA / 2 wt% SBR and 2 wt% SBR / 2 wt% CMC.

[0124] Two identical negative electrodes were assembled together with a positive electrode containing lithium iron phosphate (LEP) as the active electrode material to form a test cell 1 according to Example 2. Three test cells were obtained, differing in the binder combination within the negative electrode. All three test cells were filled with a lithium tetrachloroaluminate electrolyte according to Example 1 with the composition LiAlCl₄·6SO₂.

[0125] First, in the first cycle, the surface layer capacities were determined according to Example 3.

[0126] The test cells were charged with a current of 15 mA until a capacity of 125 mAh (Qlad) was reached. The test cells were then discharged at 15 mA until a potential of 2.5 volts was reached. The discharge capacity (Qent) was then determined.

[0127] Figure 5Each figure shows the potential in volts of the different test full cells when charging the negative electrode as a function of the capacity in [%], which is based on the theoretical capacity of the negative electrode.

[0128] The determined capacitances of the surface layer [in % of the theoretical capacitance of the negative electrode] of the various negative electrodes are as follows: NEL 2% SBR / 2% CMC: 7.48% d. th. NE NEL 2% LiPAA / 2% CMC: 7.15% d. th. NE NEL 2% LiPAA / 2% SBR: 9.34% d. th. NE

[0129] The surface layer capacities are lowest with the binder combination 2% LiPAA / 2% CMC.

[0130] To determine the discharge capacities (see Example 3), the test cells were charged with a current of 100 mA up to an upper potential of 3.6 volts. The potential of 3.6 volts was maintained until the current dropped to 40 mA. Discharge was then carried out with a discharge current of 100 mA down to a discharge potential of 2.5 volts.

[0131] Figure 6 This graph shows mean discharge capacities of the test full cells as a function of the number of cycles. 500 cycles were performed. These mean discharge capacities are expressed as a percentage of the nominal capacity [% nominal capacity].

[0132] The discharge capacities of the test cells show a steady, slightly decreasing trend. However, the capacity decrease is smallest in those test cells containing graphite electrodes with the binder combination 2% LiPAA / 2% CMC.

[0133] When using a three-dimensional electrode in the form of a nickel foam electrode, the negative electrode with the binder combination 2% LiPAA / 2% CMC shows a lower capacitance and better cycle behavior than the negative electrodes with the binder combinations 2% LiPAA / 2% SBR or 2% SBR / 2% CMC. This also confirms the findings of [V4], which state that a binder containing LiPAA has a positive effect when using a three-dimensional electrode in the form of a nickel foam electrode. Experiment 2: Mechanical investigations of graphite with different binders on a planar conductive element

[0134] To investigate the properties of graphite with different binders on a planar discharge element, mechanical tests were initially carried out. Firstly, values ​​for the adhesion of the electrode mass to the planar discharge element were determined, and secondly, tests were conducted to determine the loading, i.e., the amount of active mass per cm² of electrode area.

[0135] To investigate the adhesion of graphite with two different binder combinations to a planar conductive element, tests were conducted using a T1000 tensile / compression testing machine from MFC Sensortechnik. These tests consisted of 90° peel tests. A peel test is used to verify the properties of a film bonded to a substrate by means of a tensile test. The coated films under investigation were mounted on a carrier plate, then one free end was clamped in the tensile testing machine and pulled upwards at a constant speed of 100 mm / min. During this process, the planar conductive element, in the form of a conductive film, was detached from the electrode layer, and the adhesive force along the electrode film was measured.Two graphite electrodes were tested on a metal foil as a planar conductive element, one with the binders CMC-LiPAA-SBR (1%-2%-1%) (electrode 1) and the other with the binder CMC-SBR (2%-1%) (electrode 2). Table 3 shows the results of the adhesion measurements. Table 3: Results of the adhesion measurements Electrode 1 Electrode 2 Binder combination CMC-LiPAA-SBR (1%-2%-1%) CMC-SBR (2%-1%) Adhesion (N / m) 5,4 13,4

[0136] The graphite with the binder combination containing LiPAA has a significantly lower adhesion value than graphite with the binder combination without LiPAA. This means that the adhesion of the graphite to the electrode element is poorer for electrode 1, and mechanical stresses during battery cell operation can lead to electrode material flaking off. Electrodes with the CMC / SBR binder combination, on the other hand, adhere well to the planar electrode element.

[0137] The potential loading, i.e., the amount of active mass per cm² of electrode area, of a planar electrode was investigated. To fabricate planar electrodes, a mixture of graphite and binders was prepared and processed with a solvent to form a homogeneous paste. The finished paste was homogeneously applied to a metal foil and dried in air or at low temperatures in an oven. This step is necessary to render the electrodes solvent-free. After cooling, the electrode was compacted using a calender.

[0138] Graphite electrodes were produced using two binder mixtures: one with LiPAA (2 wt%) and CMC (2 wt%), and the other with a binder mixture of SBR (2 wt%) and CMC (2 wt%). Due to the inferior mechanical properties of LiPAA on planar electrodes, only approximately 5 mg / cm² of graphite / binder could be applied to the metal foil. Using the SBR / CMC binder mixture, the desired application rate of 14 mg / cm² was achieved. The SBR / CMC binder combination is well-suited for producing electrodes with a high coating and thus high capacity. Experiment 3 : Investigations of different binder combinations in half-cells with planar discharge elements and filled with electrolyte 1

[0139] Initially, graphite electrodes with various binder combinations were investigated in three-electrode half-cells, where the reference and counter electrodes each consisted of metallic lithium. The electrolyte used in the half-cell was electrolyte 1 according to Example 1. The following binder combinations on a planar discharge element were used: Graphite electrode with 3.0 wt% SBR and 1.0 wt% CMC; Graphite electrode with 2.0 wt% SBR and 2.0 wt% CMC; Graphite electrode with approx. 2.0 - 4.0 wt% PVDF

[0140] Since PVDF is also proposed as a suitable binder in the prior art (see [V3] and [V5]), graphite electrodes with this binder were also investigated. First, the capacitances of the surface layer were determined. For this purpose, the half-cells were charged at a rate of 0.1 C up to a potential of 0.03 V and discharged at the same rate up to a potential of 0.5 V. The capacitance loss of the first cycle was calculated from the capacitance loss. Figure 7 Each figure shows the potential in volts of the different test full cells when charging the negative electrode as a function of the capacity in [%], which is based on the theoretical capacity of the negative electrode.

[0141] The determined capacitances of the surface layer [in % of the theoretical capacitance of the negative electrode] are as follows for the different electrodes: NEL 3% SBR / 1% CMC: 14.0% of the total NE NEL 2% SBR / 2% CMC: 14.0% of the total NE NEL 2.0 - 4.0 wt% PVDF: 21.5% of the total NE

[0142] The capacitance of the negative electrode with PVDF binder is very high at 21.5%. This means that almost a quarter of the battery capacity is already consumed in capacitance formation. The sole use of PVDF binder for electrodes with a planar discharge element is not suitable for rechargeable battery cells with an SO₂-based electrolyte. However, this PVDF binder can be used as an additional, third binder alongside the SBR / CMC binder combination.

[0143] In contrast, electrodes with SBR / CMC binder exhibit a lower capacitance.

[0144] To determine the discharge capacities (see Example 3), the half-cells with SBR / CMC binder were charged in cycles 1 to 5 at a charging rate of 0.1 C up to a potential of 0.03 volts and discharged up to a potential of 0.5 volts. From cycle 6 onwards, the charging and discharging rates were increased to 1 C. Furthermore, the potential of 0.03 volts was maintained during charging until the charging rate had dropped to 0.01 C. Figure 8 This shows mean values ​​for the discharge capacities of the two half-cells as a function of the number of cycles. 25 (2% SBR / 2% CMC) and 50 (3% SBR / 1% CMC) cycles were performed. These mean discharge capacities are expressed as a percentage of the nominal capacity [% nominal capacity]. Both half-cells exhibit a stable discharge capacity. The combination of SBR and CMC binders is very well suited for electrodes with a planar grounding element in the SO₂-based electrolyte. Experiment 4: Investigations of different binder combinations in winding cells with planar discharge elements and filled with electrolyte 1

[0145] In addition to the half-cell experiments, wound cells with a positive electrode containing lithium nickel manganese cobalt oxide (NMC811) as the active material and a negative graphite electrode with the following binder combinations were investigated: 2.5 wt% SBR / 1.5 wt% CMC 2.0 wt% SBR / 2.0 wt% CMC 1.0 wt% SBR / 2.0 wt% CMC

[0146] First, in the first cycle, the capacitances of the surface layer were determined according to Example 3. For this purpose, the wound cells were charged with a current of 0.1 A until a capacity of 0.9 Ah (Qlad) was reached. The wound cells were then discharged with 0.1 A until a potential of 2.5 volts was reached. From this, the discharge capacity (Qent) was determined.

[0147] Figure 9The graph shows the potential in volts of the various wound cells when charging the negative electrode as a function of the capacitance in [%], which is relative to the theoretical capacitance of the negative electrode. The determined surface layer capacitances [in % of the theoretical capacitance of the negative electrode] for the three wound cells tested are approximately 11% of the theoretical capacitance, which is a good value.

[0148] To determine the discharge capacities (see Example 3), the wound cells with the binder combinations 2.5% SBR / 1.5% CMC and 2.0% SBR / 2.0% CMC were charged with a current of 0.2 A up to an upper potential of 4.2 volts. They were then discharged with a discharge current of 0.2 A down to a discharge potential of 2.8 volts. The charging voltage was increased to 4.4 volts and then to 4.6 volts, which was maintained for all subsequent cycles.

[0149] Figure 10This shows mean values ​​for the discharge capacities of the winding cells as a function of the number of cycles. 15 (2.5% SBR / 1.5% CMC) and 60 (2.0% SBR / 2.0% CMC) cycles were performed. These mean discharge capacities are expressed as a percentage of the nominal capacity [% nominal capacity].

[0150] The discharge capacities of both wound cells show a smooth, slightly decreasing curve. The combination of SBR and CMC binders is also very well suited for solid cells with SO₂-based electrolytes and electrodes with a planar discharge element. experiment 5: Examination of electrolytes 1, 3, 4 and 5

[0151] 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 lithium tetrachloroaluminate electrolyte were determined, and secondly, the discharge capacities in electrolytes 1, 3, 4, and 5 were determined.

[0152] To determine the surface layer capacity, three test cells were filled with electrolytes 1 and 3 and the lithium tetrachloroaluminate electrolyte as described in Example 1. The three test cells contained lithium iron phosphate as the active material of the positive electrode.

[0153] Figure 11 The graph shows the potential in volts of the test cells during charging as a function of the capacitance, which is referenced to the theoretical capacitance 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

[0154] The test cells were 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.

[0155] The absolute capacity losses are 7.58% and 11.51% for electrolytes 1 and 3, respectively, and 6.85% for the lithium tetrachloroaluminate electrolyte. The capacity for surface layer formation is low for all electrolytes.

[0156] For the discharge experiments, three test cells were filled according to Example 2 with the electrolytes 1, 3, 4, and 5 described in Example 1. The test cells used lithium nickel manganese cobalt oxide (NMC) as the active material of the positive electrode. To determine the discharge capacities (see Example 3), the test cells were charged with a current of 15 mA up to a capacity of 125 mAh. They were then discharged with a current of 15 mA down to a discharge potential of 2.5 volts.

[0157] Figure 12 This shows the potential profile during discharge versus the amount of charge discharged in % [% of the maximum charge (discharge)]. All test cells show a flat discharge curve, which is necessary for the proper operation of a battery cell. experiment 6: Determination of the conductivities of electrolytes 1, 3, 4 and 5

[0158] To determine the conductivity, electrolytes 1, 3, 4, and 5 were prepared with varying concentrations of compounds 1, 3, 4, and 5. 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.

[0159] Figure 13The graph shows the conductivities of electrolytes 1 and 4 as a function of the concentration of compounds 1 and 4, respectively. Electrolyte 1 exhibits a maximum conductivity of approximately 37.9 mS / cm at a compound 1 concentration 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 conducting salt concentration of 1 mol / L.

[0160] The Figure 14 shows the conductivities of electrolytes 3 and 5 as a function of the concentration of compounds 3 and 5, respectively.

[0161] Electrolyte 5 achieves 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 possible. experiment 7: Low-temperature behavior

[0162] To determine the low-temperature behavior of electrolyte 1 compared to the lithium tetrachloroaluminate electrolyte, two test cells were prepared according to Example 2. One test cell was filled with lithium tetrachloroaluminate electrolyte of the composition LiAlCl₄·6SO₂, and the other test cell with electrolyte 1. The test cell with the lithium tetrachloroaluminate 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. Table 5: Discharge capacities depending on temperature temperature Electrolyte discharge capacity 1 Discharge capacity of the lithium tetrachloroaluminate 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

[0163] 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 lithium tetrachloroaluminate electrolyte only shows a discharge capability down to -10°C, achieving a capacity of 21%. At lower temperatures, the cell with the lithium tetrachloroaluminate electrolyte can no longer be discharged.

Claims

1. Rechargeable battery cell (20, 40, 101) containing an active metal, at least one positive electrode (23, 44) having a planar discharge element (26), at least one negative electrode (22, 45) having a planar discharge element (27), a housing (28) and an electrolyte based on SO2which contains a first conducting salt, wherein the positive (23, 44) and / or the negative electrode (22, 45) contain at least a first binding agent which consists of a polymer based on monomer styrene and butadiene structural units, and at least a second binding agent from the group of carboxymethylcelluloses, and in which the first conducting salt 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 aluminium; - x is a whole number from 1 to 3; - the substituents R1, R2, R3 and R4 are selected independently of each other from the group which is formed by C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkinyl, C3-C10 cycloalkyl, C6-C14 aryl and C5-C14 heteroaryl; and - optionally at least one of the substituents R1, R2, R3 and R4 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 which is formed by C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkinyl, phenyl and benzyl; and - wherein Z is aluminum or boron.

2. Rechargeable battery cell (20, 40, 101) according to claim 1, in which the positive electrode (23, 44) and / or the negative electrode (22, 45) contains at least one additional binding agent which differs from the first and second binding agent, wherein this additional binding agent is preferably - a fluorinated binding agent, in particular a polyvinylidene fluoride and / or a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, or - a polymer which is 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 from a combination thereof.

3. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, in which the concentration of all binding agents in the positive (23, 44) or negative electrode (22, 45) is preferably a maximum of 20 % by weight, further preferably a maximum of 15 % by weight, further preferably a maximum of 10 % by weight, further preferably a maximum of 7 % by weight, further preferably a maximum of 5 % by weight, further preferably a maximum of 2 % by weight, further preferably a maximum of 1% by weight and most preferably a maximum of 0.5 % by weight based on the overall weight of the positive (23, 44) or negative electrode (22, 45).

4. Rechargeable battery cell (20, 40, 101) according to claim 1 to 3, in which the substituents R1, R2, R3 and R4 of the first conducting salt are selected independently of each other from the group which is formed by - C1-C6 alkyl; preferably C2-C4 alkyl; most preferably from the alkyl groups 2-propyl, methyl and ethyl; - C2-C6 alkenyl; preferably C2-C4 alkenyl; most preferably from the alkenyl groups ethenyl and propenyl; - C2-C6 alkinyl; preferably C2-C4alkinyl; - C3-C6 cycloalkyl; - phenyl; and - C5-C7 heteroaryl.

5. Rechargeable battery cell (20, 40, 101) according to any one of claims 1 to 4, in which at least one of the substituents R1, R2, R3 and R4 of the conducting salt is a CF3 group.

6. Rechargeable battery cell (20, 40, 101) according to any one of claims 1 to 4, in which the first conducting salt is selected from the group which is formed by 7. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, in which the electrolyte contains at least a second conducting salt which differs from the first conducting salt.

8. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, in which the electrolyte contains at least one additive.

9. Rechargeable battery cell (20, 40, 101) according to claim 8, in which the additive of the electrolyte is selected from the group which is formed by vinylene carbonate and the derivatives thereof, vinylethylene carbonate and the derivatives thereof, methyl ethylene carbonate and the derivatives thereof, lithium(bis oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium oxalate, 2-vinylpyridine, 4-vinylpyridine, cyclical exomethylene carbonate, sultones, cyclical and acyclical sulfonates, acyclical sulphites, cyclical and acyclical sulfinates, organic esters, inorganic acids acyclical and cyclical alkanes, which acyclical and cyclical alkanes have a boiling point at 1 bar of at least 36° C, aromatic compounds, halogenated cyclical and acyclical sulfonylimides, halogenated cyclical and acyclical phosphate esters, halogenated cyclical and acyclical phosphines, halogenated cyclical and acyclical phosphites, halogenated cyclical and acyclical phosphazenes, halogenated cyclical and acyclical silylamines, halogenated cyclical and acyclical halogenated esters, halogenated cyclical and acyclical amides, halogenated cyclical and acyclical anhydrides and halogenated organic heterocyclenes.

10. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, in which the electrolyte has the composition (i) 5 to 99.4 % by weight sulphur dioxide, (ii) 0.6 to 95 % by weight of the first conducting salt, (iii) 0 to 25 % by weight of the second conducting salt and (iv) 0 to 10 % by weight of the additive, based on the total weight of the electrolyte composition.

11. Rechargeable battery cell (20, 40, 101) 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 / I and most preferably from 0.2 mol / l to 3.5 mol / I based on the total volume of the electrolyte.

12. Rechargeable battery cell (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.

13. Rechargeable battery cell (20, 40, 101) 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.

14. Rechargeable battery cell (20, 40, 101) 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 - aluminium15. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, in which the positive electrode (23, 44) contains as an active material (24) at least one compound which preferably has the composition AxM'yM"zOa, 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 which is selected from the group which is formed by the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn; - M" is at least one element which is selected from the group which is 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 the 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.

16. Rechargeable battery cell (20, 40, 101) according to claim 15, in which the compound has the composition LixNiy1Mny2CozOa, wherein x, y1 and 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.

17. Rechargeable battery cell (20, 40, 101) according to claim 15, in which the compound has the composition AxM'yM"1z1M"2z2O4, wherein M"1 is at least one element which is selected from the group which is formed by the elements of the groups 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 of the periodic table of the elements, M"2 is phosphorus, z is a number greater than or equal to 0 and z2 has the value 1.

18. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, in which the positive electrode (23, 44) contains at least one metal compound which is selected from the group which is formed by a metal oxide, a metal halide and a metal phosphate, wherein the metal of the metal compound is preferably a transition metal with the atomic numbers 22 to 28 of the periodic table of elements, in particular cobalt, nickel, manganese or iron.

19. Rechargeable battery cell (20, 40) according to any one of the preceding claims, in which the positive electrode (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.

20. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, in which the negative electrode (22, 45) is an insertion electrode which preferably contains carbon as an active material, in particular in the modification graphite.

21. Rechargeable battery cell (20, 40, 101) according to any one of the preceding claims, which comprises at least one negative electrode (22, 45) and at least one positive electrode (23, 44), which are arranged in an alternating stacked state or wound in the housing (28), wherein the positive electrode (23, 44) and the negative electrode (22, 45) are preferably electrically separated from each other in each case by at least one separator (21, 13).