HK40092900A - So2-based electrolyte for a rechargeable battery cell, and rechargeable battery cell - Google Patents

Description

SO2-based electrolytes for rechargeable battery cells and rechargeable battery cells

This invention relates to _SO2 -based electrolytes for rechargeable battery cells and rechargeable battery cells.

Rechargeable battery cells are crucial in many technological fields. They are typically used in applications requiring relatively low current, such as operating mobile phones. However, there is also a significant need for larger rechargeable battery cells for high-energy applications, particularly for the large-scale energy storage required for the electric drive of vehicles.

A key requirement for rechargeable battery cells is high energy density. This means that a rechargeable battery cell should contain as much electrical energy as possible per unit weight and volume. For this purpose, lithium has proven particularly advantageous as an active material. The active metal in a rechargeable battery cell refers to a metal whose ions migrate within the electrolyte to the negative or positive electrode and participate in electrochemical processes there during charging or discharging. These electrochemical processes directly or indirectly result in the release of electrons into or the reception of electrons from external circuits. Rechargeable battery cells containing lithium as an active metal are also called lithium-ion cells. The energy density of these lithium-ion cells can be increased by increasing the specific capacity of the electrodes or by increasing the cell voltage.

Both the positive and negative electrodes of a lithium-ion battery cell are designed as insertion electrodes. The term "insertion electrode" is understood within the meaning of this invention to refer to an electrode with a crystalline structure in which ions of the active material can be inserted and extracted during the operation of the lithium-ion battery cell. This means that the electrode process can occur not only on the electrode surface but also within the crystalline structure. Both electrodes typically have a thickness of less than 100 μm and are therefore designed to be very thin. During charging of the lithium-ion battery cell, ions of the active metal are extracted from the positive electrode and inserted into the negative electrode. During discharging of the lithium-ion battery cell, the reverse process occurs.

The electrolyte is also a crucial functional component of every rechargeable battery cell. It typically contains a solvent or a mixture of solvents and at least one conductive salt. For example, solid electrolytes or ionic liquids contain no solvent but only a conductive salt. The electrolyte is in contact with the positive and negative electrodes of the battery cell. At least one ion (anion or cation) of the conductive salt moves within the electrolyte such that charge transfer necessary for the function of the rechargeable battery cell can occur between the electrodes via ionic conduction. Above a specific upper limit cell voltage of the rechargeable battery cell, the electrolyte electrochemically decomposes through oxidation. This process typically leads to irreversible degradation of the electrolyte components and thus causes the rechargeable battery cell to fail. Below a specific lower limit cell voltage, a reduction process can also decompose the electrolyte. To avoid these processes, the positive and negative electrodes are chosen such that the cell voltage is below and above the electrolyte's decomposition voltage, respectively. Therefore, the electrolyte determines the voltage window within which the rechargeable battery cell can operate reversibly, that is, the voltage window within which it can be repeatedly charged and discharged.

Lithium-ion cells known in the prior art contain an electrolyte, which consists of an organic solvent or solvent mixture and a conductive salt dissolved therein. The conductive salt is a lithium salt, such as lithium hexafluorophosphate ( _LiPF6 ). For example, the solvent mixture may contain ethylene carbonate (EC). The electrolyte LP57, with a composition of 1M LiPF6 in EC:EMC 3: ₇ , is an example of such an electrolyte. Due to the organic solvent or solvent mixture, this type of lithium-ion cell is also referred to as an organic lithium-ion cell. In addition to lithium hexafluorophosphate ( _LiPF6 ), which is frequently used as a conductive salt in the prior art, other conductive salts for use in organic lithium-ion cells have been described. For example, the document JP 4306858 B2 (hereinafter referred to as [V1]) describes conductive salts, namely tetraalkoxy or tetraaryloxyborates, which can be fluorinated or partially fluorinated. JP 2001143750 A (hereinafter referred to as [V2]) reports fluorinated or partially fluorinated tetraalkoxyborates and tetraalkoxyaluminates as conductive salts. In two documents, [V1] and [V2], the described conductive salts are dissolved in organic solvents or solvent mixtures and used in organic lithium-ion cells. The negative electrode of many organic lithium-ion cells consists of a carbon coating applied to a copper current collector. The current collector establishes the necessary electronic conductive connection between the carbon coating and the external circuitry. The positive electrode consists of lithium cobalt oxide ( _LiCoO₂ ) applied to an aluminum current collector.

It is well known that undesirable overcharging of organic lithium-ion cells leads to irreversible decomposition of the electrolyte components. Here, the oxidative decomposition of organic solvents and/or conductive salts occurs at the positive electrode surface. The heat of reaction generated during this decomposition and the resulting gaseous products are the cause of subsequent so-called "thermal runaway" and the resulting damage to the organic lithium-ion cell. Most charging protocols for these organic lithium-ion cells use cell voltage as an indicator of the end of charging. This thermal runaway-induced failure is particularly likely to occur when using multi-cell battery packs with multiple mismatched organic lithium-ion cells connected in series.

Therefore, organic lithium-ion cells present challenges in terms of stability and long-term operational safety. Safety risks are also particularly arising from the flammability of organic solvents or solvent mixtures. If an organic lithium-ion cell catches fire or even explodes, the organic solvents in the electrolyte form flammable materials. Another drawback of organic lithium-ion batteries is the highly corrosive nature of hydrolysis products that can form in the presence of residual water, affecting the cell components of rechargeable battery cells. These issues regarding stability and long-term operational safety make it particularly difficult to develop organic lithium-ion cells that possess both excellent energy and performance data and very high operational safety and lifespan, especially a large number of usable charge-discharge cycles.

Therefore, further research and development guidelines based on existing technology specify the use of sulfur dioxide ( _SO₂ )-based electrolytes instead of organic electrolytes in rechargeable battery cells. Rechargeable battery cells containing _SO₂ -based electrolytes exhibit particularly high ionic conductivity. The term " _SO₂ -based electrolyte" should be understood as an electrolyte that not only contains a low concentration of _SO₂ as an additive, but also ensures, at least partially, largely, or even entirely _{, the inclusion of conductive salts in the electrolyte and facilitates charge transport through the migration of ions. SO₂ thus} serves as a solvent for the conductive salts. The conductive salts can form liquid solvate complexes with gaseous _SO₂ , where _SO₂ is bound and the vapor pressure is significantly lower than that of pure _SO₂ , forming an electrolyte with a low vapor pressure. Compared to the aforementioned organic electrolytes, such _SO₂ -based electrolytes have the advantage of being non-flammable. Therefore, safety risks arising from the flammability of the electrolyte can be eliminated.

For example, EP 1201004 B1 (hereinafter referred to as [V3]) describes a combination of an _SO2 -based electrolyte with the composition _LiAlCl4 * _SO2 and a positive electrode made of _LiCoO2 . To avoid interfering decomposition reactions, such as the undesirable formation of chlorine gas ( _Cl2 ) from lithium tetrachloroaluminate ( _LiAlCl4 ), when the rechargeable battery cell is overcharged above 4.1 volts to 4.2 volts, [V3] recommends the use of an additional salt.

EP 2534719 B1 (hereinafter referred to as [V4]) also discloses an _SO2 -based electrolyte, which in particular contains _LiAlCl4 as a conductive salt. The _LiAlCl4 forms a complex with _SO2 , for example, with the formula _LiAlCl4 * 1.5 moles of _SO2 or _LiAlCl4 * 6 moles of _SO2 . Lithium iron phosphate ( _LiFePO4 ) is used as the positive electrode. Compared to _LiCoO2 (4.2V), _LiFePO4 has a lower charging potential (3.7V). Undesirable overcharge reactions do not occur in this rechargeable battery cell because the harmful potential of 4.1V for the electrolyte is not reached.

A drawback of using _SO₂ -based electrolytes is that hydrolysis products formed in the presence of residual water can react with the cell components of the rechargeable battery, leading to undesirable byproducts. Therefore, when manufacturing rechargeable battery cells containing _SO₂ -based electrolytes, care must be taken to minimize the residual water content in the electrolyte and cell components.

Another problem with _SO₂ -based electrolytes is that many conductive salts, especially those known to be used in organic lithium-ion cells, are insoluble in _SO₂ . Measurements show that _SO₂ is a poor solvent for many salts, such as lithium fluoride (LiF), lithium bromide (LiBr), _lithium sulfate ( _Li₂SO₄ ), lithium hexafluoroarsenate ( _LiAsF₆ ), lithium tetrafluoroborate ( _LiBF₄ ), trilithium hexafluoroaluminate ( _Li₃AlF₆ ), lithium hexafluoroantimonylate (LiSbF₆), lithium _bis (trifluoromethanesulfonyl)imino ( _LiTFSI ), lithium metaborate ( _LiBO₂ ), lithium aluminate ( _LiAlO₂ ), lithium _{trifluoromethanesulfonate} ( _LiCF₃SO₃ ), and lithium chlorosulfonate ( _LiSO₃Cl ). The solubility of these salts in _SO₂ is approximately ^10⁻² – ^10⁻⁴ mol/L (see Table 1). Under these low concentration conditions, it can be assumed that there is at most only low conductivity, which is insufficient for the rechargeable battery cell to operate properly.

Table 1: Solubility of various salts in _SO₂

To further improve the potential uses and performance of _SO₂ -based electrolytes and rechargeable battery cells containing such electrolytes, an object of the present invention is, in one aspect, to provide an _SO₂ -based electrolyte that, compared with electrolytes known in the prior art...

- It has a wide electrochemical window, so electrolyte oxidative decomposition will not occur at the positive electrode;

-A stable capping layer is formed on the negative electrode, wherein the capping layer capacity should be low, so that the negative electrode will not undergo further electrolyte reduction and decomposition during further operation;

- The wide electrochemical window provides the possibility of operating rechargeable battery cells with high-voltage cathodes.

- It has good solubility in conductive salts, thus it is a good ionic conductor and electronic insulator, which can promote ion transport and limit self-discharge to a minimum;

It is also inert to other components of rechargeable battery cells, such as separators, electrode materials, and cell packaging materials.

- Robust against various abuses such as electrical, mechanical, or thermal; and

- Improved stability of residual water content in cell assemblies of rechargeable battery cells.

This electrolyte should be particularly suitable for use in rechargeable battery cells that have excellent energy and performance data, high operational safety and lifespan, and especially a large number of usable charge and discharge cycles, while the electrolyte does not decompose during the operation of the rechargeable battery cell.

On the other hand, the object of the present invention is to provide a rechargeable battery cell comprising an _SO2 -based electrolyte, which, compared with rechargeable battery cells known in the prior art...

- It features improved electrical performance data, especially high energy density;

- Improved overcharge and deep discharge capabilities;

- It has a low self-discharge;

-Exhibits extended lifespan, especially a large number of available charge and discharge cycles.

-With reduced total weight;

- Enhanced operational safety, even under harsh environmental conditions within the vehicle; and

- It has the effect of reducing production costs.

The objective is achieved by an _SO₂ -based electrolyte having the features of claim 1 and a rechargeable battery cell having the features of claim 15. Claims 2 to 14 define advantageous extensions of the electrolyte according to the invention. Claims 16 to 25 describe advantageous extensions of the rechargeable battery cell according to the invention.

The _SO2 -based electrolyte for rechargeable battery cells of the present invention comprises at least one first conductive salt having formula (I).

in

-M is a metal selected from alkali metals, alkaline earth metals, group 12 metals of the periodic table, and aluminum;

-x is an integer from 1 to 3;

- Substituents ^R1 and ^R2 are independently selected from halogen atoms, hydroxyl groups, chemical groups - ^OR5 and chelate ligands formed by at least two of the substituents ^R1 , ^R2 , ^R3 and ^R4 and coordinated with Z;

- Substituent ^R3 is selected from hydroxyl groups, chemical groups ^-OR5 , and chelate ligands formed by at least two of the substituents ^R1 , ^R2 , ^R3 , and ^R4 and coordinated with Z;

- Substituent ^R4 is selected from halogen atoms, hydroxyl groups, and chelate ligands formed by at least two of the substituents ^R1 , ^R2 , ^R3 , and ^R4 and coordinated with Z;

-Substituent ^R5 is selected from _C1 - _C10 alkyl, _C2 - _C10 alkenyl, _C2 - _C10 ynyl, _C3 - _C10 cycloalkyl, _C6 - _C14 aryl, and _C5 - _C14 heteroaryl; and

-Z represents aluminum or boron.

Therefore, the substituents ^R1 , ^R2 , ^R3 , and ^R4 are independently selected from halogen atoms, hydroxyl groups (-OH), and the chemical group ^-OR5 , wherein ^R1 , ^R2 , ^R3 , and ^R4 are neither four halogen atoms nor four chemical groups ^-OR5 , especially alkoxy groups. In the context of this invention, the expression "a chelate ligand formed by at least two of the substituents ^R1 , ^R2 , ^R3 , and ^R4 and coordinated to Z" should be understood to mean that at least two of the substituents ^R1 , ^R2 , ^R3 , and ^R4 can be bridged to each other, wherein the bridging of two substituents results in the formation of a bidentate chelate ligand. For example, the chelate ligand can be designed as bidentate according to the formula ^-OR5 -O-. To form this chelate ligand ^-OR5 -O-, structurally, the first substituent ^R1 is preferably an ^OR5 group, and the second substituent ^R2 is preferably a hydroxyl group. They are connected to each other by forming chemical bonds in their bridged state, thus having the above formula ^-OR5 -O-. Such a chelate ligand can, for example, have the following structural formula:

The chelating ligand coordinates with the central atom Z to form a chelate complex. In the case of the bidentate chelating ligand ^-OR5 -O-, the two oxygen atoms coordinate with the central atom Z. Such chelate complexes can be synthesized as described in Example 1 below. The term "chelate complex" refers to a complex compound in which a polydentate ligand (having more than one free electron pair) occupies at least two coordination sites (bonding sites) of the central atom. The chelate ligand can also be designed to be polydentate if three or four of the substituents ^R1 , ^R2 , ^R3 , and ^R4 are each bridged to each other.

The _SO₂ -based electrolyte according to the invention not only contains a low concentration of _SO₂ as an additive, but also ensures the ion migration of a first conductive salt, which is at least partially, largely, or even completely contained in the electrolyte and enables charge transport, through _SO₂ . The first conductive salt dissolves in the electrolyte and exhibits very good solubility therein. It can form a liquid solvate complex with gaseous _SO₂ , in which _SO₂ is bound. In this case, the vapor pressure of the liquid solvate complex is significantly lower than that of pure _SO₂ , and an electrolyte with a low vapor pressure is formed. However, also within the scope of the invention, in the manufacture of the electrolyte according to the invention, a decrease in vapor pressure does not occur depending on the chemical structure of the first conductive salt according to formula (I). In the last mentioned case, it is preferred that the manufacture of the electrolyte according to the invention is carried out at low temperature or under pressure. The electrolyte may also contain multiple conductive salts of formula (I) whose chemical structures differ from each other.

In the context of this invention, the term " _C1 - _C10 alkyl" includes straight-chain or branched saturated hydrocarbon groups having one to ten carbon atoms. These specifically include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, 2,2-dimethylpropyl, n-hexyl, isohexyl, 2-ethylhexyl, n-heptyl, isoheptyl, n-octyl, isooctyl, n-nonyl, n-decyl, etc.

In the context of this invention, the term " _C2 - _C10 alkenyl" includes unsaturated straight-chain or branched hydrocarbon groups having two to ten carbon atoms, wherein the hydrocarbon group has at least one C-C double bond. These particularly include vinyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, isobutenyl, 1-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 1-nonenyl, 1-decenyl, etc.

In the context of this invention, the term " _C2 - _C10 ynyl" includes unsaturated straight-chain or branched hydrocarbon groups having two to ten carbon atoms, wherein the hydrocarbon group has at least one C-C triple bond. These particularly include ethynyl, 1-propynyl, 2-propynyl, 1-n-butynyl, 2-n-butynyl, isobutynyl, 1-pentynyl, 1-hexynyl, 1-heptyynyl, 1-octyynyl, 1-nonynyl, 1-decynyl, etc.

In the context of this invention, the term " _C3 - _C10 cycloalkyl" includes cyclic saturated hydrocarbon groups having three to ten carbon atoms. These particularly include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclohexyl, cyclononyl, and cyclodecyl.

In the context of this invention, the term " _C6 - _C14 aryl" includes aromatic hydrocarbon groups having six to _fourteen carbon atoms in the ring. These particularly include phenyl ( _C6H5 group), naphthyl ( _{C10H7 group} ), and anthracene ( _{C14H9 group} ).

In the context of this invention, the term " _C5 - _C14 heteroaryl" includes aromatic hydrocarbon groups having five to fourteen hydrocarbon atoms in the ring, wherein at least one hydrocarbon atom is substituted or replaced by a nitrogen, oxygen, or sulfur atom. These particularly include pyrrole, furanyl, thiophene, pyridyl, pyranyl, thioranyl, etc.

The advantage of this electrolyte over electrolytes known in the prior art is that the first conductive salt it contains has higher oxidation stability and therefore shows virtually no decomposition at higher cell voltages. This electrolyte is oxidation-stable, preferably at a potential of at least 4.0 V, more preferably at least 4.2 V, more preferably at least 4.4 V, more preferably at least 4.6 V, more preferably at least 4.8 V, and particularly preferably at least 5.0 V. Therefore, when this electrolyte is used in a rechargeable battery cell, only minimal or even no electrolyte decomposition occurs within the operating potentials of the two electrodes of the rechargeable battery cell. Consequently, the service life of this electrolyte is significantly longer than that of electrolytes known in the prior art. Furthermore, this electrolyte is resistant to low temperatures. If a small amount of residual water remains in the electrolyte (in the ppm range), the electrolyte or the first conductive salt forms hydrolysis products with the water, which are significantly less corrosive to the cell assembly compared to _SO₂ -based electrolytes known in the prior art. Therefore, compared to _SO₂ -based electrolytes containing the conductive salt _LiAlCl₄ known in the prior art, the absence of water in the electrolyte renders it less important. These advantages of the electrolyte according to the invention overcome the disadvantage caused by the significantly larger anion size of the first conductive salt according to formula (I) compared to known conductive salts in the prior art. This larger anion size results in a lower conductivity of the first conductive salt according to formula (I) compared to the conductivity of _LiAlCl₄ .

Another aspect of the invention provides a rechargeable battery cell. This rechargeable battery cell comprises the electrolyte described above according to the invention or an electrolyte according to one of the advantageous embodiments of the electrolyte described below according to the invention. Furthermore, the rechargeable battery cell according to the invention comprises an active metal, at least one positive electrode, at least one negative electrode, and a casing.

electrolytes

Advantageous extensions of the electrolyte according to the present invention are described below:

In a first advantageous embodiment of the electrolyte according to the invention, the substituent ^R5 is selected from:

_-C1 - _C6 alkyl; preferably _C2 - _C4 alkyl; particularly preferred alkyl groups are selected from 2-propyl, methyl and ethyl;

_-C2 - _C6 alkenyl; preferably _C2 - _C4 alkenyl; particularly preferred alkenyl groups are selected from vinyl and propenyl groups;

_-C2 - _C6 ynyl group; preferably _C2 - _C4 ynyl group;

-C _3- C ₆ cycloalkyl;

-phenyl; and

_-C5 - _C7 heteroaryl.

In advantageous embodiments of the electrolyte according to the invention, the term " _C1 - _C6 alkyl" includes straight-chain or branched saturated hydrocarbon groups having one to six hydrocarbon groups, particularly methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, 2,2-dimethylpropyl, n-hexyl, and isohexyl. _C2 - _C4 alkyl is preferred. Particularly preferred are _C2 - _C4 alkyl groups, which are 2-propyl, methyl, and ethyl.

In an advantageous embodiment of the electrolyte according to the invention, the term " _C2 - _C6 alkenyl" comprises an unsaturated straight-chain or branched hydrocarbon group having two to six carbon atoms, wherein the hydrocarbon group has at least one C-C double bond. These particularly include vinyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, isobutenyl, 1-pentenyl, and 1-hexenyl, with _C2 - _C4 alkenyl being preferred. Vinyl and 1-propenyl are particularly preferred.

In an advantageous embodiment of the electrolyte according to the invention, the term " _C2 - _C6 ynyl" comprises an unsaturated straight-chain or branched hydrocarbon group having two to six carbon atoms, wherein the hydrocarbon group has at least one C-C triple bond. These particularly include ethynyl, 1-propynyl, 2-propynyl, 1-n-butynyl, 2-n-butynyl, isobutynyl, 1-pentynyl, and 1-hexynyl. _C2 - _C4 ynyl is preferred.

In advantageous embodiments of the electrolyte according to the invention, the term " _C3 - _C6 cycloalkyl" includes cyclic saturated hydrocarbon groups having three to six carbon atoms. These particularly include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

In an advantageous embodiment of the electrolyte according to the invention, the term " _C5 - _C7 heteroaryl" includes phenyl and naphthyl groups.

To improve the solubility of the first conductive salt in _SO₂ -based electrolytes, at least one individual atom or group of substituent ^R₅ is replaced by a halogen atom, particularly a fluorine atom, or by a chemical group selected from _C₁ - _C₄ -alkyl, _C₂ - _C₄ -alkenyl, _C₂ - _C₄ -ynyl, phenyl, benzyl, and fully and partially halogenated, particularly fully and partially fluorinated, _C₁ - _C₄ -alkyl, _C₂ - _C₄ -alkenyl, _C₂ - _C₄ -ynyl, phenyl, and benzyl groups. The _C₁ - _C₄ -alkyl, _C₂ - _C₄ -alkenyl, _C₂ - _C₄ -ynyl, phenyl, and benzyl chemical groups have the same properties or chemical structures as the aforementioned hydrocarbon groups.

If one to three of the substituents ^R1 , ^R2 , ^R3 , and ^R4 are hydroxyl groups (-OH), then one to three hydrogen atoms (H) of these hydroxyl groups can also be replaced by chemical groups selected from _C1 - _C4 -alkyl, _C2 - _C4 -alkenyl, _C2 - _C4 -ynyl, phenyl, benzyl, and fully and partially halogenated, especially fully and partially fluorinated, _C1 - _C4 -alkyl, _C2 - _C4 -alkenyl, _C2 - _C4 -ynyl, phenyl, and benzyl groups. The chemical groups _C1 - _C4 -alkyl, _C2 - _C4 -alkenyl, _C2 - _C4 -ynyl, phenyl, and benzyl have the same properties or chemical structures as the aforementioned hydrocarbon groups.

The exceptionally high solubility of the first conductive salt in _SO₂ -based electrolytes can be achieved by having at least one atomic group of substituent ^R₅ preferably a _CF₃- group or _{an OSO₂CF₃-} group.

In another advantageous embodiment of the electrolyte according to the invention, the first conductive salt is selected from:

To adapt the conductivity and/or other properties of the electrolyte to desired values, in another advantageous embodiment, the electrolyte has at least one second conductive salt that differs from the first conductive salt according to (I). This means that, in addition to the first conductive salt, the electrolyte may also contain one or more second conductive salts that differ from the first conductive salt in their chemical composition and chemical structure.

In an advantageous embodiment of the electrolyte according to the invention, the second conductive salt has formula (II).

In formula (II), M is a metal selected from alkali metals, alkaline earth metals, Group 12 metals of the periodic table, and aluminum. x is an integer from 1 to 3. Substituents ^R6 , ^R7 , ^R8 , and ^R9 are independently selected from _C1 - _C10 alkyl, _C2 - _C10 alkenyl, _C2 - _C10 alkynyl, _C3 - _C10 cycloalkyl, _C6 - _C14 aryl, and _C5 - _C14 heteroaryl. The central atom Z is aluminum or boron. In order to improve the solubility of the second conductive salt of formula (II) in an _SO2 -based electrolyte, substituents ^R6 , ^R7 , ^R8 , and ^R9 are substituted with at least one halogen atom and/or at least one chemical group selected from _C1 - _C4 -alkyl, _C2 - _C4 -alkenyl, _C2 - _C4 -alkynyl, phenyl, and benzyl in another advantageous embodiment of the rechargeable battery cell. In this document, substitution refers to the replacement of each atom or group of substituents ^R6 , ^R7 , ^R8 , and ^R9 by a halogen atom and/or by a chemical group. The chemical groups _C1 - _C10 alkyl, _C2 - _C10 alkenyl, _C2 - _C10 alkynyl, _C3 - _C10 cycloalkyl, _C6 - _C14 aryl, and _C5 - _C14 heteroaryl have the same properties or chemical structures as the hydrocarbon groups described for the first conductive salt having formula (I). The particularly high solubility of the second conductive salt according to formula (II) in _SO2 -based electrolytes can be achieved by at least one of the substituents ^R6 , ^R7 , ^R8 , and ^R9 being a _CF3- group or an _{OSO2 CF3-} group.

In another advantageous embodiment of the electrolyte according to the invention, the second conductive salt is an alkali metal compound, particularly a lithium compound. The alkali metal compound or lithium compound is selected from aluminates, halides, oxalates, borates, phosphates, arsenates, and gallates. The second conductive salt is preferably lithium tetrahaloaluminate, particularly _LiAlCl₄ .

Furthermore, in another advantageous embodiment, the electrolyte comprises at least one additive. This additive is preferably selected from vinylene carbonate and its derivatives, vinylene carbonate and its derivatives, methyl ethylene carbonate and its derivatives, lithium (bis(oxalate)borate), lithium difluoro(oxalate)borate, lithium tetrafluoro(oxalate)phosphate, lithium oxalate, 2-vinylpyridine, 4-vinylpyridine, cyclic exomethylene carbonates, sulcolones, cyclic and acyclic sulfonates/esters, acyclic sulfites/esters, cyclic and acyclic sulfite/esters, organic esters, and inorganic esters. Acids, acyclic and cyclic alkanes, the acyclic and cyclic alkanes having a boiling point of at least 36°C at 1 bar, aromatic compounds, halogenated cyclic and acyclic sulfonamides, halogenated cyclic and acyclic phosphates, halogenated cyclic and acyclic phosphines, halogenated cyclic and acyclic phosphites/esters, 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 acid anhydrides, and halogenated organic heterocycles.

Based on the total weight of the electrolyte composition, in another advantageous embodiment, the electrolyte has the following composition:

(i) 5 to 99.4% by weight of sulfur dioxide,

(ii) 0.6 to 95% by weight of the first conductive salt,

(iii) 0 to 25% by weight of a second conductive salt and

(iv) 0 to 10% by weight of additives.

As described above, the electrolyte may contain not only one first conductive salt and one second conductive salt according to formula (I), but also multiple first conductive salts and multiple second conductive salts according to formula (I). In the latter case, the above percentage examples also include multiple first conductive salts and multiple second conductive salts. The molar concentration of the first conductive salt is from 0.05 mol/L to 10 mol/L, 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.

In another advantageous embodiment of the rechargeable battery cell according to the invention, the electrolyte contains at least 0.1 moles of _SO₂ , preferably at least 1 mole of _SO₂ , more preferably at least 5 moles of _SO₂ , even more preferably at least 10 moles of _SO₂ , and particularly preferably at least 20 moles of _SO₂ per mole of conductive salt. The electrolyte may also contain a very high molar proportion of _SO₂ , wherein a preferred upper limit of 2600 moles of _SO₂ per mole of conductive salt can be given, and upper limits of 1500, 1000, 500, and 100 moles of _SO₂ per mole of conductive salt are more preferred in this order. The term “per mole of conductive salt” is used here based on all conductive salts contained in the electrolyte. The advantage of _SO₂ -based electrolytes having this concentration ratio between _SO₂ and conductive salt is that they can dissolve a larger amount of conductive salt compared to electrolytes known in the prior art, such as those based on organic solvent mixtures. Within the scope of the invention, it has been surprisingly found that electrolytes with relatively low concentrations of conductive salt, while having a higher vapor pressure associated with them, are advantageous, particularly in terms of their stability during multiple charge and discharge cycles of the rechargeable battery cell. The _SO2 concentration in an electrolyte affects its conductivity. Therefore, by selecting the _SO2 concentration, the conductivity of the electrolyte can be adapted to the intended use of the rechargeable battery cell operating with that electrolyte.

The total content of _SO2 and the first conductive salt can be greater than 50% by weight (wt%) of the electrolyte, preferably greater than 60% by weight, more preferably greater than 70% by weight, more preferably greater than 80% by weight, more preferably greater than 85% by weight, more preferably greater than 90% by weight, more preferably greater than 95% by weight or more preferably greater than 99% by weight.

_Based on the total amount of electrolyte contained in the rechargeable battery cell, the electrolyte may contain at least 5% by weight of _SO2 , with values of 20 _% by weight, 40% by weight, and 60% by weight of _SO2 being more preferred. The electrolyte may also contain up to 95% by weight of _SO2 , with the maximum values of 80% by weight and 90% by weight _{of SO2} being preferred in that order.

Within the scope of this invention, the electrolyte preferably contains only a small percentage or even no percentage of at least one organic solvent. The proportion of the organic solvent (e.g., present in the form of one solvent or a mixture of solvents) in the electrolyte is preferably up to 50% by weight of the electrolyte. Lower proportions of up to 40%, 30%, 20%, 15%, 10%, 5%, or 1% by weight of the electrolyte are particularly preferred. More preferably, the electrolyte is free of organic solvents. Because the proportion of organic solvents is only low or even completely absent, the electrolyte is almost non-flammable or not flammable at all. This improves the operational safety of rechargeable battery cells operating using such _SO₂ -based electrolytes. Particularly preferably, the _SO₂ -based electrolyte is substantially free of organic solvents.

Active metals

The following describes an advantageous extension of the active metal in the rechargeable battery cell according to the present invention:

In the first advantageous extension of rechargeable battery cells, the active metal is...

-Alkali metals, especially lithium or sodium;

-Alkaline earth metals, especially calcium;

- Metals in Group 12 of the periodic table, especially zinc; or

-aluminum.

negative electrode

The following describes an advantageous extension of the rechargeable battery cell according to the invention with respect to the negative electrode:

Another advantageous extension of the rechargeable battery cell specifies that the negative electrode is an insertion electrode. This insertion electrode comprises an insertion material as the active material, into which active metal ions can be inserted during charging and extracted during discharging. This means that the electrode process can occur not only on the surface of the negative electrode but also inside it. For example, if a lithium-based conductive salt is used, lithium ions can be inserted into the insertion material during charging and extracted during discharging. The negative electrode preferably comprises carbon as the active or insertion material, particularly in the form of variant graphite. However, also within the scope of this invention, carbon can be present in the form of natural graphite (sheet-like or spherical), synthetic graphite (mesophase graphite), graphitized mesophase carbon microspheres (MCMB), carbon-coated graphite, or amorphous carbon.

In another advantageous extension of the rechargeable battery cell according to the invention, the negative electrode comprises a carbon-free lithium-intercalated anode active material, such as lithium _titanate (e.g. _{, Li₄Ti₅O₁₂} ).

In another advantageous extension of the rechargeable battery cell according to the invention, the negative electrode comprises an anode active material alloyed with lithium. This is, for example, a lithium-storing metal and metal alloy (e.g., Si, Ge, Sn, _SnCoxCy , _{SnSix ,} etc.) and oxides of lithium-storing metals and metal alloys (e.g., _SnOx , _SiOx , Sn, Si oxide glasses, etc.).

In another advantageous extension of the rechargeable battery cell according to the invention, the negative electrode comprises a switching anode active material. The switching anode active material may be, for example, a transition metal oxide in the form of manganese oxide (MnO _x ), iron oxide (FeO _x ), cobalt oxide (CoO _x ), nickel oxide (NiO _x ), copper oxide (CuO _x ), or a metal hydride in the form of magnesium hydride ( _MgH₂ ), titanium hydride ( _TiH₂ ), aluminum hydride ( _AlH₃ ), and boron, aluminum, and magnesium-based ternary hydrides.

In another advantageous extension of the rechargeable battery cell according to the invention, the negative electrode comprises a metal, particularly lithium metal.

In another advantageous extension of the rechargeable battery cell according to the invention, 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 particularly preferably at most 10%. Porosity represents the cavity volume relative to the total volume of the negative electrode, wherein the cavity volume is formed by so-called pores or cavities. This porosity increases the internal surface area of the negative electrode. Furthermore, the porosity reduces the density of the negative electrode and thus also reduces its weight. The pores of the negative electrode can preferably be completely filled with electrolyte during operation.

In another advantageous extension of the battery cell according to the invention, the negative electrode has a current collector. This means that the negative electrode includes a current collector in addition to the active material or intercalation material. This current collector is used to achieve the electronic conduction connection required for the active material of the negative electrode. For this purpose, the current collector is in contact with the active material participating in the electrode reaction of the negative electrode. The current collector can be designed in the form of a planar thin metal plate or a thin metal film. The thin metal film preferably has a perforated or mesh structure. The negative electrode active material is preferably applied to the surface of the thin metal plate or thin metal film. The thickness of such a planar current collector is from 5 μm to 50 μm. The thickness of the planar current collector is preferably from 10 μm to 30 μm. When using a planar current collector, 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. When using a planar current collector, the area specific capacity of the negative electrode is preferably at least 0.5 mAh/ ^cm² , wherein the following values are more preferred in this order: 1 mAh/ ^cm² , 3 mAh/ ^cm² , 5 mAh/ ^cm² , and 10 mAh/ ^cm² .

Furthermore, it is also possible that the current collector can be designed as a three-dimensional porous metal structure, particularly in the form of a metal foam. The term "three-dimensional porous metal structure" refers to a structure composed of metal that extends not only in the length and width of the flat electrode, like a thin metal plate or film, but also in its thickness. The three-dimensional porous metal structure is so porous that the active material of the negative electrode can be incorporated into the pores of the metal structure. The amount of active material incorporated or applied is the loading of the negative electrode. If the current collector is designed as a three-dimensional porous metal structure, particularly in the form of a metal foam, the negative electrode preferably has a thickness of at least 0.2 mm, more preferably at least 0.3 mm, more preferably at least 0.4 mm, more preferably at least 0.5 mm, and particularly preferably at least 0.6 mm. In this case, the electrode thickness is significantly greater than that of the negative electrode used in organic lithium-ion cells. Another advantageous embodiment specifies that, when using a three-dimensional current collector in the form of metal foam, particularly metal foam, the areal capacity of the negative electrode is preferably at least 2.5 mAh/ ^cm² , with the following values being more preferred in this order: 5 mAh/ ^cm² , 10 mAh/ ^cm² , 15 mAh/ ^cm² , 20 mAh/ ^cm² , 25 mAh/ ^cm² , and 30 mAh/ ^cm² . If the current collector is designed as a three-dimensional porous metal structure, particularly metal foam, the amount of active material in the negative electrode, i.e., the electrode load, based on its area, is at least 10 mg/ ^cm² , preferably at least 20 mg/ ^cm² , more preferably at least 40 mg/ ^cm² , more preferably at least 60 mg/ ^cm² , more preferably at least 80 mg/ ^cm² , and particularly preferably at least 100 mg/ ^cm² . This loading of the negative electrode has a positive impact on the charging and discharging processes of the rechargeable battery cell.

In another advantageous extension of the battery cell according to the invention, the negative electrode has at least one adhesive. This adhesive is preferably a fluorinated adhesive, particularly polyvinylidene fluoride and/or a terpolymer formed from tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. However, it can also be an adhesive composed of monomeric structural units of a conjugated carboxylic acid or polymers formed from alkali metal, alkaline earth metal, or ammonium salts of the conjugated carboxylic acid, or combinations thereof. Furthermore, the adhesive can also be composed of polymers based on monomeric styrene and butadiene structural units. Additionally, the adhesive can also be an adhesive selected from carboxymethyl cellulose. The adhesive is preferably present in the negative electrode at a concentration of at most 20% by weight, more preferably at most 15% by weight, more preferably at most 10% by weight, more preferably at most 7% by weight, more preferably at most 5% by weight, and particularly preferably at most 2% by weight, based on the total weight of the negative electrode.

positive electrode

The following describes an advantageous extension of the rechargeable battery cell according to the invention with respect to the positive electrode:

In another advantageous extension of the battery cell according to the invention, the positive electrode comprises at least one intercalation compound as an active material. In the context of this invention, the term "intercalation compound" should be understood to refer to a subcategory of the aforementioned intercalation materials. This intercalation compound acts as a host matrix with interconnected vacancies. Ions of the active metal can diffuse into these vacancies and intercalate there during the discharge of the rechargeable battery cell. During this intercalation of the active metal ions, only little or no structural change occurs in the host matrix. Preferably, the intercalation compound has the composition Li _{_x}M_{_y}M_{_z}O_{_a} , wherein...

-M' is at least one metal selected from the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn;

"-M" is at least one element selected from groups 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 of the periodic table;

-x and y are independently greater than 0;

-z is greater than or equal to 0; and

-a is greater than 0.

The exponents y and z here refer to all metals and elements represented by M' and M" respectively. For example, if M' includes two metals _M'1 and _M'2 , then the following applies to the exponent y: y = y1 + y2, where y1 and y2 represent the exponents of metals _M'1 and _M'2 . The exponents x, y, z, and a must be chosen such that there is charge neutrality within the composition.

The preferred composition is Li _x M' _y M" _z O _4. In another advantageous extension of the rechargeable battery cell according to the invention, in the composition Li _x M' _y M" _z O ₄ , M' is iron and M" is phosphorus. In this case, the intercalation compound is lithium iron phosphate (LiFePO ₄ ). In another advantageous extension of the rechargeable battery cell according to the invention, in the composition Li _x M' _y M" _z O ₄ , M' is manganese and M" is cobalt. In this case, the intercalation compound is lithium cobalt manganese oxide (LiCoMnO ₄ ). With LiCoMnO ₄ , so-called high-voltage electrodes for high-energy cells with cell voltages exceeding 5 volts can be manufactured. This LiCoMnO ₄ preferably does not contain Mn ³⁺ .

In another advantageous extension of the rechargeable battery cell according to the invention, M' is composed of metallic nickel and manganese, and M” is cobalt. It is composed of the formula Li _{_x}Ni _{_y1}Mn_{_y2}Co_{z O₂} (NMC). Examples of these lithium nickel manganese cobalt oxide intercalation compounds are LiNi _{_1/3}Mn_{_1/3} Co _{_1/3} O _₂ (NMC111), LiNi _{_0.6}Mn_{_0.2}Co_₂O_₂ (NMC622), and LiNi _{_0.8} Mn _{_0.1} Co _{_0.1}O_₂ (NMC811).

The high-voltage electrode can be cycled in the rechargeable battery cell according to the invention at an upper limit potential of at least 4.0 volts, more preferably at least 4.2 volts, more preferably at least 4.4 volts, more preferably at least 4.6 volts, more preferably at least 4.8 volts, and particularly preferably at least 5.0 volts.

In another advantageous embodiment of the rechargeable battery cell according to the invention, the positive electrode comprises at least one metal compound. This metal compound is selected from metal oxides, metal halides, and metal phosphates. The metal of this compound is preferably a transition metal with atomic numbers 22 to 28 of the periodic table, particularly cobalt, nickel, manganese, or iron.

In another advantageous extension of the battery cell according to the invention, the positive electrode has a current collector. This means that the positive electrode includes a current collector in addition to the active material. This current collector is used to achieve the electronic conduction connection required for the active material of the positive electrode. For this purpose, the current collector is in contact with the active material participating in the electrode reaction of the positive electrode.

The current collector can be designed as a planar thin metal plate or thin metal film. The thin metal film preferably has a perforated or mesh structure. The positive electrode active material is preferably applied to the surface of the thin metal plate or thin metal film. The thickness of this planar current collector is 5 μm to 50 μm. The thickness of the planar current collector is preferably 10 μm to 30 μm. When using a planar current collector, 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. When using a planar current collector, the areal capacity of the positive electrode is preferably at least 0.5 mAh/ ^cm² , wherein the following values are more preferred in this order: 1 mAh/ ^cm² , 3 mAh/ ^cm² , 5 mAh/ ^cm² , and 10 mAh/ ^cm² .

Furthermore, it is also possible that the current collector of the positive electrode is designed in the form of a three-dimensional porous metal structure, particularly in the form of metal foam. The three-dimensional porous metal structure is so porous that the active material of the positive electrode can be incorporated into the pores of the metal structure. The amount of active material incorporated or applied is the loading of the positive electrode. If the current collector is designed in the form of a three-dimensional porous metal structure, particularly in the form of metal foam, the positive electrode preferably has a thickness of at least 0.2 mm, more preferably at least 0.3 mm, more preferably at least 0.4 mm, more preferably at least 0.5 mm, and particularly preferably at least 0.6 mm. Another advantageous embodiment specifies that when using a three-dimensional current collector in the form of metal foam, particularly metal foam, the areal capacity of the positive electrode is preferably at least 2.5 mAh/ ^cm² , wherein the following values are more preferred in this order: 5 mAh/ ^cm² , 10 mAh/ ^cm² , 15 mAh/ ^cm² , 20 mAh/ ^cm² , 25 mAh/ ^cm² , and 30 mAh/ ^cm² . If the current collector is designed as a three-dimensional porous metal structure, particularly a metal foam, the amount of active material in the positive electrode, i.e., the electrode load, based on its area, is at least 10 mg/ ^cm² , preferably at least 20 mg/ ^cm² , more preferably at least 40 mg/ ^cm² , more preferably at least 60 mg/ ^cm² , more preferably at least 80 mg/ ^cm² , and particularly preferably at least 100 mg/ ^cm² . This loading of the positive electrode has a positive impact on the charging and discharging processes of the rechargeable battery cell.

In another advantageous extension of the battery cell according to the invention, the positive electrode has at least one adhesive. This adhesive is preferably a fluorinated adhesive, particularly polyvinylidene fluoride and/or a terpolymer formed from tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. However, it can also be an adhesive composed of monomeric structural units of a conjugated carboxylic acid or polymers formed from alkali metal, alkaline earth metal, or ammonium salts of the conjugated carboxylic acid, or combinations thereof. Furthermore, the adhesive can also be composed of polymers based on monomeric styrene and butadiene structural units. Additionally, the adhesive can also be an adhesive selected from carboxymethyl cellulose. The adhesive is preferably present in the positive electrode at a concentration of at most 20% by weight, more preferably at most 15% by weight, more preferably at most 10% by weight, more preferably at most 7% by weight, more preferably at most 5% by weight, and particularly preferably at most 2% by weight, based on the total weight of the positive electrode.

Structure of rechargeable battery cells

The following describes an advantageous structural extension of the rechargeable battery cell according to the present invention:

To further improve the functionality of the rechargeable battery cell, another advantageous extension of the rechargeable battery cell according to the invention specifies that the rechargeable battery cell includes a plurality of negative electrodes and a plurality of positive electrodes arranged alternately in a housing. In this case, the positive and negative electrodes are preferably electrically isolated from each other by separators.

However, rechargeable battery cells can also be designed as wound cells, where the electrodes consist of thin layers wound together with a separator material. On the one hand, the separator spatially and electrically separates the positive and negative electrodes; on the other hand, they are particularly permeable to ions of active metals. In this way, a large electrochemically active surface is created, enabling a correspondingly high current output.

The separator can be formed from nonwoven fabrics, membranes, woven fabrics, knitted fabrics, organic materials, inorganic materials, or combinations thereof. Organic separators can consist of unsubstituted polyolefins (e.g., polypropylene or polyethylene), partially to fully halogenated polyolefins (e.g., partially to fully fluorinated, particularly PVDF, ETFE, PTFE), polyesters, polyamides, or polysulfones. Separators comprising combinations of organic and inorganic materials are, for example, glass fiber textiles, in which the glass fibers have a suitable polymer coating. This coating preferably comprises fluoropolymers such as polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene (ETFE), perfluoroethylene-propylene (FEP), THV (a terpolymer of tetrafluoroethylene, hexafluoroethylene, and vinylidene fluoride), perfluoroalkoxy polymers (PFA), aminosilanes, polypropylene, or polyethylene (PE). The separator can also be folded within the casing of a rechargeable battery cell, for example, in a so-called "Z-fold" configuration. In this Z-fold configuration, the strip-shaped separator is folded in a Z-shape through or around the electrodes. Alternatively, the separator can also be designed as a separator paper.

Also within the scope of this invention, the diaphragm can be designed as a sheath, wherein each positive electrode or each negative electrode is encapsulated by the sheath. The sheath can be formed of nonwoven fabric, membrane, woven fabric, knitted fabric, organic material, inorganic material, or a combination thereof.

Encapsulating the positive electrode results in more uniform ion migration and distribution within the rechargeable battery cell. A more uniform ion distribution, particularly in the negative electrode, allows for a higher potential loading of active materials, thus increasing the usable capacity of the rechargeable battery cell. Simultaneously, it avoids the risks associated with uneven loading of active metals and the resulting separation. These advantages are particularly evident when the positive electrode of the rechargeable battery cell is encapsulated.

The area sizes of the electrode and the sheath can preferably be matched to each other so that the outer dimensions of the sheath and the outer dimensions of the unencapsulated electrode match at least in one dimension.

The area of the envelope can preferably be larger than that of the electrode. In this case, the envelope extends beyond the boundary of the electrode. Therefore, the two layers of the envelope covering both sides of the electrode can be joined together at the edge of the positive electrode through an edge connection.

In another advantageous embodiment of the rechargeable battery cell according to the invention, the negative electrode has a sleeve, while the positive electrode does not.

Other advantageous features of the invention are described and explained in more detail below with reference to the accompanying drawings, embodiments, and experiments.

Figure 1: Shows a cross-sectional view of a first embodiment of a rechargeable battery cell according to the present invention;

Figure 2: An electron micrograph showing the three-dimensional porous structure of the metal foam of the first embodiment in Figure 1 as a detailed view;

Figure 3: A cross-sectional view showing a second embodiment of a rechargeable battery cell according to the present invention;

Figure 4 shows details of the second embodiment of Figure 3;

Figure 5: An exploded view showing a third embodiment of the rechargeable battery cell according to the present invention;

Figure 6: Shows the charging and discharging potential curves in volts [V] vs. charge percentage for a half-cell filled with electrolyte X1;

Figure 7: Shows the charge and discharge potential curves in volts [V] vs. charge percentage of the test full cell filled with electrolyte X1;

Figure 8: Shows the potential in [V] of two test full cells filled with 9%/91% electrolyte and a reference electrolyte during charging versus the capacity during the formation of a capping layer on the negative electrode, based on the theoretical capacity of the negative electrode;

Figure 9: Shows the discharge capacity vs. cycle number of two test cells filled with 9%/91% electrolyte and a reference electrolyte;

Figure 10: Shows the potential in [V] of two test full cells filled with 30%/70% electrolyte and a reference electrolyte during charging, versus the capacity during the formation of a capping layer on the negative electrode, based on the theoretical capacity of the negative electrode;

Figure 11: Shows the discharge capacity vs. cycle number of two test cells filled with 30%/70% electrolyte and a reference electrolyte;

Figure 12 shows the conductivity vs. concentration of electrolyte X1 according to the present invention in [mS/cm].

Figure 1 shows a cross-sectional view of a first embodiment of a rechargeable battery cell 2 according to the present invention. The rechargeable battery cell 2 is designed as a prismatic cell and, in particular, has a housing 1. The housing 1 surrounds an electrode assembly 3, which includes three positive electrodes 4 and four negative electrodes 5. The positive electrodes 4 and negative electrodes 5 are arranged alternately in the electrode assembly 3. However, the housing 1 may also accommodate more positive electrodes 4 and/or negative electrodes 5. Generally, it is preferred that the number of negative electrodes 5 is one more than the number of positive electrodes 4. As a result, the outer end face of the electrode stack is formed by the electrode surface of the negative electrode 5. Electrodes 4 and 5 are connected to corresponding contact points 9 and 10 of the rechargeable battery cell 2 via electrode connectors 6 and 7. The rechargeable battery cell 2 is filled with an _SO₂ -based electrolyte such that the electrolyte permeates as completely as possible into all pores or cavities, particularly within electrodes 4 and 5. The electrolyte is not visible in Figure 1. In this embodiment, the positive electrode 4 contains an intercalating compound as an active material. This intercalating compound is _LiCoMnO₄ .

In this embodiment, electrodes 4 and 5 are designed to be flat, i.e., as layers with a thickness smaller than their area size. They are separated from each other by separator 11. The casing 1 of the rechargeable battery cell 2 is designed to be generally cuboid, wherein the walls of electrodes 4 and 5 and casing 1, as shown in the cross-sectional view, extend perpendicularly to the plane of the drawing and are formed generally straight and flat. However, the rechargeable battery cell 2 can also be designed as a wound cell, wherein the electrodes consist of thin layers wound together with the separator material. Separator 11 separates the positive electrode 4 and negative electrode 5 spatially and electrically, and is particularly permeable to ions of the active metal. In this way, a large electrochemically active surface is generated, which enables a correspondingly high current output.

Electrodes 4 and 5 also have current collectors (not shown in Figure 1) for achieving the electronic conduction connections required for the active materials of their respective electrodes. These current collectors are in contact with the active materials (not shown in Figure 1) participating in the electrode reactions of their respective electrodes 4 and 5. The current collectors are designed in the form of a porous metal foam. The metal foam extends along the thickness dimension of electrodes 4 and 5. The active materials of the positive electrode 4 and the negative electrode 5 are incorporated into the pores of this metal foam so that it uniformly fills the pores across the entire thickness of the metal structure. To improve mechanical strength, the positive electrode 4 contains a binder. This binder is a fluoropolymer. The negative electrode 5 contains carbon as an active material, which is in a form suitable for receiving lithium ions as an intercalation material. The structure of the negative electrode 5 is similar to that of the positive electrode 4.

Figure 2 shows an electron micrograph of the three-dimensional porous structure of the metal foam 18 of the first embodiment of Figure 1. As can be seen from the scale bar, the pores P have an average diameter greater than 100 μm, which is relatively large.

Figure 3 shows a cross-sectional view of a second embodiment of the rechargeable battery cell 20 according to the present invention. This second embodiment differs from the first embodiment shown in Figure 1 in that the electrode arrangement includes a positive electrode 23 and two negative electrodes 22. The electrodes 22 and 23 are each separated from each other by a separator 21 and surrounded by a housing 28. The positive electrode 23 has a current collector 26 in the form of a planar metal film, with active material 24 applied to both sides of the positive electrode 23. The negative electrode 22 also includes a current collector 27 in the form of a planar metal film, with active material 25 applied to both sides of the negative electrode 22. Alternatively, the planar current collector of the edge electrode, i.e., the electrode of the closed electrode stack, may be coated with active material on only one side. The uncoated side faces the wall of the housing 28. The electrodes 22 and 23 are connected to corresponding contact points 31 and 32 of the rechargeable battery cell 20 via electrode connectors 29 and 30.

Figure 4 shows a planar metal film, which serves as current collector elements 26 and 27 for the positive electrode 4 and negative electrode 5, respectively, in the second embodiment of Figure 3. This metal film has a perforated or mesh structure and a thickness of 20 μm.

Figure 5 shows an exploded view of a third embodiment of the rechargeable battery cell 40 according to the present invention. This third embodiment differs from the two embodiments explained above in that the positive electrode 44 is encapsulated by a sleeve 13, which serves as a separator. Here, the area of the sleeve 13 is larger than that of the positive electrode 44, and the boundary 14 of the positive electrode is drawn with a dashed line in Figure 5. The two layers 15 and 16 of the sleeve 13 covering both sides of the positive electrode 44 are joined together at the periphery of the positive electrode 44 by an edge connection 17. The two negative electrodes 45 are not encapsulated. Electrodes 44 and 45 can contact each other through electrode connectors 46 and 47.

Example 1 : Manufacturing a reference electrolyte

For the following experiments, a reference electrolyte based on _SO₂ was prepared. To this end, compound 1, as a conductive salt according to formula (II), was first prepared according to the manufacturing method described in the following reference [V5]:

[V5],,I.Krossing,Chem.Eur.J.2001,7,490;

Compound 1 is derived from the polyfluoroalkoxyaluminate family and is prepared in hexane starting from _LiAlH4 and the corresponding alcohol R-OH according to the following reaction equation, where ^R1 = ^R2 = ^R3 = ^R4 .

The result is compound 1 shown below, which has the following general formula or structural formula:

To prepare the reference electrolyte, compound 1 was dissolved in _SO₂ . The concentration of the conductive salt in the reference electrolyte was 0.6 mol/L.

Example 2 : An example of manufacturing the electrolyte according to the present invention

The conductive salt of formula (I) having chelating ligands is prepared from the corresponding diol HO-R-OH according to the manufacturing method described in the following document [V6]:

[V6] Wu Xu et al., Electrochem. Solid-State Lett. 2000, 3, 366-368.

For example, the following reaction equation describes the preparation of compound X1:

For purification, compound X1 was first recrystallized. This removed the reactant residue from the conductive salt.

The conductive salt of formula (I), wherein three alkoxy groups and one fluoride ion group are coordinated to the central atom, can be manufactured according to the manufacturing method described in the following document [V7]:

[V7] A. Martens et al., Chem. Sci., 2018, 9, 7058–7068.

The following compound X2 was used in the experiment:

The conductive salt of formula (I), wherein at least one alkoxy group and at least one hydroxyl group are coordinated to the central atom, can be prepared by treating a tetraalkoxy compound with a stoichiometric amount of donor solvent. For example, compounds X3 and X4 are produced by the reaction of Li[Al(OC( _{CF3)3 ) 4} ] with water:

To prepare electrolytes X1, X2, X3, and X4, compounds X1, X2, X3, and X4 were dissolved in _SO2 . This preparation was carried out at low temperature or pressure according to steps 1 to 4 of the following method:

1) Compounds X1, X2, X3, and X4 are pre-placed in their respective pressure flasks equipped with risers.

2) Evacuate the pressure flask.

3) Allow liquid _SO2 to flow into and

4) Repeat steps 2 and 3 until the target amount of _SO2 has been added.

Example 3: Manufacturing and Testing of All Battery Cells

The test cells used in the experiments described below are rechargeable battery cells having two negative electrodes and one positive electrode, each separated by a separator. The positive electrode comprises an active material, a conductivity promoter, a binder, and a current collector made of nickel or aluminum. The active materials of the positive electrode are named in their respective experiments. The negative electrode comprises graphite as the active material, a binder, and a current collector made of nickel or copper. Conductive additives may also be included in the negative electrode, if mentioned in the experiments. The purpose of the study is, in particular, to confirm the functionality of various electrolytes in the battery cells according to the invention. The test cells were filled with the electrolytes required for the experiments, i.e., filled with a reference electrolyte or electrolytes X1, X2, X3, and X4 according to the invention.

For each experiment, multiple, i.e., two to four identical test cells are typically manufactured. The results given in the experiment are, at this point, the average values of the measurements obtained from the same test cells.

Example 4 : Measurements in the entire battery cell

Overlay capacity:

The capacity consumed during the first cycle in which the capping layer forms on the negative electrode is an important criterion for battery cell quality. This capping layer forms on the negative electrode during the first charge of the tested full cell. For this capping layer formation, lithium ions are irreversibly consumed (capping layer capacity), therefore a small portion of the cycleable capacity of the tested full cell is available for subsequent cycles. The capping layer capacity consumed to form the capping layer on the negative electrode, expressed as a percentage of the theoretical value, is calculated using the following formula:

Cover layer capacity [theoretical value %] = (Q _{_lad} (x mAh) - Q _{_ent} (y mAh)) / Q _{_NEL}

Q _{_lad} describes the predetermined charge quantity in mAh for each experiment; Q _{_ent} describes the charge quantity in mAh obtained when the entire cell is subsequently discharged. _{Q_NEL} is the theoretical capacity of the negative electrode used. For example, in the case of graphite, the calculated theoretical capacity is 372 mAh/g.

Discharge capacity:

For example, in testing a full battery cell, the discharge capacity after a certain number of cycles is determined. To do this, the test cell is charged to a specific upper limit potential with a specific charging current intensity. This upper limit potential is maintained until the charging current drops to a specific value. Afterward, it is discharged with a specific discharge current intensity until a specific discharge potential is reached. This charging method is called I/U charging. This process is repeated according to the required number of cycles.

The upper limit potential or discharge potential, and their respective charging or discharging current intensities, were specified in the experiment. The values to which the charging current must decrease were also described in the experiment.

The term "upper limit potential" is used synonymously with the terms "charging potential," "charging voltage," "charging termination voltage," and "potential limit." These terms refer to the voltage/potential reached when charging a cell or battery using a battery charging device. The battery is preferably charged at a current rate of C/2 and a temperature of 22°C.

The term "discharge potential" is used synonymously with the term "lower limit cell voltage." This refers to the voltage/potential reached when a cell or battery is discharged using a battery charging device. Preferably, the battery discharges at a current rate of C/2 and a temperature of 22°C. Discharge capacity is obtained from the discharge current and the time until the discharge termination criterion is met. The accompanying figures show the average discharge capacity versus the number of cycles. These average discharge capacities are typically normalized to 100% of the initial capacity and expressed as a percentage of the nominal capacity.

Experiment 1: Characteristics of the negative electrode in a half-cell with electrolyte X1

The experiment was conducted in a half-cell containing lithium metal as both the counter and reference electrodes. The working electrode was a graphite electrode. The half-cell was filled with electrolyte X1.

The half-cell was charged to 0.03 volts and discharged to 0.5 volts at a charge/discharge rate of 0.02C. Figure 6 shows the charging and discharging potentials of the half-cell during the second cycle. The solid line corresponds to the potential of the charging curve, and the dashed line corresponds to the potential of the discharging curve.

The charge and discharge curves show the typical characteristics of the battery. This demonstrates the basic function of the electrolyte X1 in the half-cell.

Example 2: Characteristics of a test cell with electrolyte X1

In the experiment, the electrolyte X1 in the entire battery cell was studied and tested. This structure corresponds to the structure described in Example 3. The negative electrode uses graphite as the electrode active material, and the positive electrode uses nickel manganese cobalt oxide (NMC622) as the electrode active material.

To determine the discharge capacity, the test cell was charged to 4.6 volts and discharged to 2.5 volts with a charge/discharge current of 100mA.

Figure 7 shows the potential curves during the second cycle of charging and discharging the entire battery cell. The potential curves illustrate the typical characteristics of the battery. This demonstrates the basic function of the electrolyte X1 in the battery cell.

Example 3: A mixture having 9 wt% electrolytes X2, X3, and X4 and 91 wt% reference electrolyte Testing the characteristics of all battery cells

To investigate electrolytes X2, X3, and X4, a mixture of these electrolytes was prepared. 9% by weight of this mixture was mixed with 91% by weight of a reference electrolyte. The resulting electrolyte was termed "9%/91% electrolyte". Various experiments were conducted using the 9%/91% electrolyte. The coating capacity of the electrolyte was determined, and the discharge capacity within the electrolyte was measured. For comparison, both experiments were also performed using a reference electrolyte.

For the experiments, the reference electrolyte and electrolyte 9%/91% were studied in the test full cell, respectively. This structure corresponds to the structure described in Example 3. The negative electrode uses graphite as the electrode active material, and the positive electrode uses nickel manganese cobalt oxide (NMC622) as the electrode active material.

Figure 8 shows the potential vs. capacity in [V] of the entire cell tested during charging, based on the theoretical capacity of the negative electrode. The dashed line shows the results for the reference electrolyte, and the solid line shows the results for the electrolyte according to the invention at 9%/91%. The two curves shown represent the results for a representative single cell. First, the entire cell was charged to a capacity of 125mAh at a current intensity of 15mA. Then, the entire cell was discharged at a current intensity of 15mA until a potential of 2.5V was reached. The capping capacity was determined from the capacity characteristics during the first cycle.

The capacity loss of the electrolyte (9%/91%) was 6.64%, while the capacity loss of the reference electrolyte was 5.62%. The capacity of the coating layer formed with the electrolyte according to the invention is slightly higher than that with the reference electrolyte. A capacity loss of approximately 6.6% is a very good result.

To determine the discharge capacity (see Example 4), after determining the capping capacity, the two test cells were charged to a potential of 4.4 volts at a current intensity of 100 mA. Subsequently, they were discharged to a discharge potential of 2.5 volts at a current intensity of 100 mA.

Figure 9 shows the discharge capacity vs. cycle number in % [nominal capacity] of the tested full cell during 100 cycles. Here, the dashed line shows the results for the reference electrolyte, and the solid line shows the results for the electrolyte according to the invention at 9%/91%. During the measurement of the test full cell with the 9%/91% electrolyte, measurement interference occurred from cycle 4 to cycle 34. Therefore, the values in this range were slightly lower. From cycle 35 onwards, the interference was eliminated. Both test full cells showed very flat discharge capacity curves. The 9%/91% electrolyte is well-suited for operation in battery cells.

Example 4: A mixture comprising 30 wt% electrolytes X2, X3, and X4 and 70 wt% reference electrolyte Testing the characteristics of all battery cells

To further investigate electrolytes X2, X3, and X4, a mixture of these electrolytes was prepared. This time, 30% by weight of this mixture was mixed with 70% by weight of a reference electrolyte. The resulting electrolyte was designated "electrolyte 30%/70%". The same tests as those described for the 9%/91% electrolyte in Experiment 3 were performed using the 30%/70% electrolyte. The measurement parameters can be obtained from Experiment 3. The coating capacity of the electrolyte was determined on one hand, and the discharge capacity in the electrolyte on the other. For comparison, both experiments were also conducted using a reference electrolyte.

Figure 10 shows the potential vs. capacity of the entire cell in volts during cell charging, based on the theoretical capacity of the negative electrode. The dashed line shows the results for the reference electrolyte, and the solid line shows the results for the electrolyte according to the invention at 30%/70%.

The capacity loss of the electrolyte at 30%/70% was 5.63%, while the capacity loss of the reference electrolyte was 6.09%. In the case of the electrolyte according to the invention, the capacity of the coating layer formed is lower than that of the reference electrolyte. A capacity loss of approximately 5.6% is an excellent result.

Figure 11 shows the discharge capacity vs. cycle number, in % [nominal capacity], of the tested full cells during 200 cycles. Here, the dashed line shows the results for the reference electrolyte, and the solid line shows the results for the electrolyte 30%/70% according to the invention. Both tested full cells show very flat discharge capacity curves, with the curve for the 30%/70% electrolyte being slightly more stable. The 30%/70% electrolyte is extremely suitable for operation in battery cells.

Experiment 5: Determining the conductivity of electrolyte X1

To determine conductivity, electrolyte X1 with different concentrations of compound X1 was prepared. For each concentration of the compound, the conductivity of the electrolyte was determined using a conductivity measurement method. Here, after temperature adjustment, a four-electrode sensor was kept in contact with the solution, and measurements were performed within a measurement range of 0.02–500 mS/cm.

Figure 12 shows the conductivity of electrolyte X1 versus the concentration of compound X1. A maximum conductivity of approximately 11.3 mS/cm is observed at a compound X1 concentration of 0.6 mol/L.

Claims (25)

1. An _SO₂ -based electrolyte for rechargeable battery cells, comprising at least one first conductive salt having formula (I). in -M is a metal selected from alkali metals, alkaline earth metals, group 12 metals of the periodic table, and aluminum; -x is an integer from 1 to 3; - Substituents ^R1 and R2 are independently selected from halogen atoms, hydroxyl groups, chemical groups ^-OR5 and chelate ligands formed by at least two of the substituents ^R1 , R2, R3 and ^R4 and coordinated with Z; - Substituent R3 is selected from hydroxyl groups, chemical groups -OR ⁵ , and chelate ligands formed by at least two of the substituents ^R1 , R2, R3, and ^R4 and coordinated with Z; - Substituent ^R4 is selected from halogen atoms, hydroxyl groups, and chelate ligands formed by at least two of substituents ^R1 , R2, R3, and ^R4 and coordinated with Z; -Substituent ^R5 is selected from _C1 - _C10 alkyl, _C2 - _C10 alkenyl, _C2 - _C10 ynyl, _C3 - _C10 cycloalkyl, _C6 - _C14 aryl, and _C5 - _C14 heteroaryl; and -Z represents aluminum or boron. 2. The electrolyte of claim 1, wherein the substituent ^R5 is selected from: _-C1 - _C6 alkyl; preferably _C2 - _C4 alkyl; particularly preferred alkyl groups are selected from 2-propyl, methyl and ethyl; _-C2 - _C6 alkenyl; preferably _C2 - _C4 alkenyl; particularly preferred alkenyl groups are selected from vinyl and propenyl groups; _-C2 - _C6 ynyl group; preferably _C2 - _C4 ynyl group; -C _3- C ₆ cycloalkyl; -phenyl; and _-C5 - _C7 heteroaryl. 3. The electrolyte of claim 1 or 2, wherein at least one individual atom or group of substituent ^R5 is replaced by a halogen atom, particularly a fluorine atom, or by a chemical group selected from _C1 - _C4 -alkyl, _C2 - _C4 -alkenyl, _C2 - _C4 -ynyl, phenyl, benzyl and fully and partially halogenated, particularly fully and partially fluorinated, _C1 - _C4 -alkyl, _C2 - _C4 -alkenyl, _C2 - _C4 -ynyl, phenyl and benzyl. 4. The electrolyte according to any one of claims 1 to 3, wherein at least one atomic group of substituent ^R5 is a _CF3- group or _{an OSO2CF3-} group. 5. The electrolyte according to any one of claims 1 to 4, wherein the chelating ligand is designed to be bidentate, particularly according to formula -OR ⁵ -O-, or designed to be multidentate. 6. The electrolyte according to any one of claims 1 to 5, The first conductive salt is selected from 7. The electrolyte according to any one of claims 1 to 6, wherein it contains at least one second conductive salt different from the first conductive salt according to formula (I). 8. The electrolyte according to claim 7, The second conductive salt has formula (II). in -M is a metal selected from alkali metals, alkaline earth metals, group 12 metals of the periodic table, and aluminum; -x is an integer from 1 to 3; The substituents ^R6 , ^R7 , ^R8 , and ^R9 are independently selected from _C1 - _C10 alkyl, _C2 - _C10 alkenyl, _C2 - _C10 ynyl, _C3 - _C10 cycloalkyl, _C6 - _C14 aryl, and _C5 - _C14 heteroaryl; and - Where Z is aluminum or boron. 9. The electrolyte according to claim 7, wherein the second conductive salt is an alkali metal compound, particularly a lithium compound, selected from aluminates, preferably lithium tetrahaloaluminate, particularly lithium tetrachloroaluminate, halides, oxalates, borates, phosphates, arsenates and gallates. 10. The electrolyte according to any one of claims 1 to 9, wherein it contains at least one additive. 11. The electrolyte according to claim 10, wherein the additive is selected from vinylene carbonate and its derivatives, vinylene carbonate and its derivatives, methyl ethylene carbonate and its derivatives, lithium (bis(oxalate)borate), lithium difluoro(oxalate)borate, lithium tetrafluoro(oxalate)phosphate, lithium oxalate, 2-vinylpyridine, 4-vinylpyridine, cyclic exomethylene carbonate, sulopentalide, cyclic and acyclic sulfonates/esters, acyclic sulfites/esters, cyclic and acyclic sulfonates/esters Esters, organic esters, inorganic acids, acyclic and cyclic alkanes, wherein the acyclic and cyclic alkanes have a boiling point of at least 36°C at 1 bar, aromatic compounds, halogenated cyclic and acyclic sulfonamides, halogenated cyclic and acyclic phosphates, halogenated cyclic and acyclic phosphines, halogenated cyclic and acyclic phosphites/esters, 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 acid anhydrides, and halogenated organic heterocycles. 12. The electrolyte according to any one of claims 1 to 11, It has the following components (i) 5 to 99.4% by weight of sulfur dioxide, (ii) 0.6 to 95% by weight of the first conductive salt, (iii) 0 to 25% by weight of a second conductive salt and (iv) 0 to 10% by weight of additives, Based on the total weight of the electrolyte composition. 13. The electrolyte according to any one of claims 1 to 12, The molar concentration of the first conductive salt is 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. 14. The electrolyte according to any one of claims 1 to 13, The electrolyte contains at least 0.1 moles of _SO₂ , preferably at least 1 mole of _SO₂ , more preferably at least 5 moles of _SO₂ , more preferably at least 10 moles of _SO₂ , and particularly preferably at least 20 moles of _SO₂ per mole of conductive salt. 15. A rechargeable battery cell (2, 20, 40) comprising an electrolyte, an active metal, at least one positive electrode (4, 23, 44), at least one negative electrode (5, 22, 45), and a casing (1, 28) according to at least one of the preceding claims. 16. The rechargeable battery cell (2, 20, 40) according to claim 15, The active metals are alkali metals, especially lithium or sodium; -Alkaline earth metals, especially calcium; - Metals in Group 12 of the periodic table, especially zinc; or -aluminum. 17. The rechargeable battery cell (2, 20, 40) according to claim 15 or 16, wherein the negative electrode (5, 22, 45) is an insertion electrode, which preferably contains carbon as an active material, particularly in the form of a graphite variant. 18. The rechargeable battery cell (2, 20, 40) according to any one of claims 15 to 17, The positive electrode (4, 23, 44) contains at least one intercalation compound as an active material, which preferably has the composition Li _{_x}M'_{_y}M"_{_z}O_{_a}. -M' is at least one metal selected from the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn; "-M" means at least one element selected from groups 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 of the periodic table; -x and y are independently greater than 0; -z is greater than or equal to 0; and -a is greater than 0. 19. The rechargeable battery cell (2, 20, 40) according to claim 18, The composition of the embedded compound is Li _x M' _y M" _z O _a , where M' is iron and M" is phosphorus, and x, y and z are preferably 1 and a is preferably 4. 20. The rechargeable battery cell (2, 20, 40) according to claim 18, The composition of the intercalated compound is Li _x M' _y M" _z O _a , where M' is manganese and M" is cobalt, and x, y and z are preferably 1 and a is preferably 4. 21. The rechargeable battery cell (2, 20, 40) according to claim 18 or 20, The composition of the intercalated compound is Li _x M' _y M" _z O _a , where M' includes nickel and manganese and M" is cobalt. 22. The rechargeable battery cell (2, 20, 40) according to any one of claims 15 to 21, wherein the positive electrode (4, 23, 44) contains at least one metal compound selected from metal oxides, metal halides and metal phosphates, wherein the metal of the metal compound is preferably a transition metal with atomic number 22 to 28 of the periodic table, particularly cobalt, nickel, manganese or iron. 23. The rechargeable battery cell (2, 20, 40) according to any one of claims 15 to 22, The positive electrode (4, 23, 44) and/or the negative electrode (5, 22, 45) have current collector elements (26, 27), which are preferably designed as planar metal plates or metal films; or - Three-dimensional porous metal structures, especially metal foams (18). 24. The rechargeable battery cell (2, 20, 40) according to any one of claims 15 to 23, The positive electrode (4, 23, 44) and/or the negative electrode (5, 22, 45) contain at least one adhesive, preferably a fluorinated adhesive, particularly polyvinylidene fluoride and/or a terpolymer formed from tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, or An adhesive composed of polymers formed from monomeric structural units of a conjugated carboxylic acid or from an alkali metal, alkaline earth metal, or ammonium salt of that conjugated carboxylic acid, or combinations thereof; Adhesives composed of polymers based on monomeric styrene and butadiene structural units, or adhesives selected from carboxymethyl cellulose. The adhesive is preferably present at a concentration of up to 20% by weight, more preferably up to 15% by weight, more preferably up to 10% by weight, more preferably up to 7% by weight, more preferably up to 5% by weight, and particularly preferably up to 2% by weight, based on the total weight of the positive or negative electrode. 25. The rechargeable battery cell (2, 20, 40) according to any one of claims 15 to 24, It includes multiple positive electrodes (4, 23, 44) and multiple electrodes (5, 22, 45), which are arranged in an alternately stacked manner in the housing (1), wherein the positive electrodes (4, 23, 44) and the negative electrodes (5, 22, 45) are preferably electrically isolated from each other by diaphragms (11, 21).