Method for forming a battery cell

Abstract

The invention relates to a method for forming a battery cell. A method for forming a battery cell (1), wherein the battery cell (1) has a housing (2) and at least one anode (3) arranged therein, a cathode (4), a separator (5) arranged therebetween, and an electrolyte (6) at least partially surrounding the anode (3), the cathode (4) and the separator (5); wherein the method comprises at least the following steps: a) providing a housing (2) and the anode (3), the cathode (4) and the separator (5) arranged therein; b) contacting the anode (3), the cathode (4) and the separator (5) with a first composition (7) of the electrolyte (6); c) charging the battery cell (1) in a first state (8) to a first voltage value (9) between the anode (3) and the cathode (4); d) replenishing the first composition (7) of the electrolyte (6) in the housing (2) with a second composition (11) of the electrolyte (6) that is different from the first composition (7).

Description

Technical Field

[0001] The present invention relates to a method for forming a battery cell. Background Art

[0002] Batteries, in particular lithium-ion batteries, are increasingly being used to power motor vehicles. Batteries are usually composed of cells, each of which has a housing and at least one anode and cathode arranged therein and a separator arranged therebetween.

[0003] Formation and subsequent aging are among the most important process steps in the production of battery cells, especially lithium-ion cells. During the formation process, freshly produced battery cells are charged and discharged for the first time. During this process, an important boundary layer is formed between the electrolyte and the active materials. Its properties have a significant influence on the performance and aging behavior of the cell. The boundary layer on the anode side is called the solid electrolyte interface (SEI for short), and the boundary layer on the cathode side is called the cathode decomposition layer (CDL for short) or cathode electrolyte interface (CEI for short).

[0004] After formation, the cell is aged for some time to improve cell performance. During this time, remaining byproducts react and the electrolyte can be distributed throughout the cell, if it has not already done so.

[0005] During the formation process, the battery cell is charged from an initial approximately 0 volt to a higher voltage in the first cycle. In the low voltage range, for example, less than 3.7 volts, some electrolyte components, such as electrolyte additives, have decomposed on electrodes, such as anodes. For some electrolyte components, such as cyclic carbonates or additives, this process is desirable (first class additives, such as SEI additives, i.e., they are used to form SEI), and for other electrolyte components, such as other additives, this process is undesirable (second class additives). The unwanted decomposition of electrolyte components may cause the internal resistance of the battery cell to increase. In addition, the second class additives may decompose in an undesirable manner, which causes them to no longer fully function due to the reduced amount.

[0006] For certain electrolyte components, such as certain solvents and safety additives, for example, the decomposition in the voltage range of secondary cells can be so great that the use of these electrolyte components in battery cells has hitherto been impossible. Furthermore, the use of electrolyte components in secondary cells whose decomposition has an excessively strong negative influence on the performance capabilities of the battery cell or whose supposed positive effects can no longer be measured due to the large degree of decomposition has hitherto been excluded.

[0007] In order to counteract the reduction in the amount of additives of the second type, for example, an excess of these additives can be added initially. However, this leads to increased costs.

[0008] Alternatively, other additives with higher reduction stability may be used. This results in a restriction of the choice of the second additive and may also result in increased costs or performance losses for the battery cell.

[0009] Finally, still further additives (either first or second type) may be introduced into the electrolyte composition that decompose at lower voltages to passivate the electrode and prevent or reduce decomposition of the second type additives. This complicates the electrolyte formulation and may also result in increased cost or performance loss of the battery cell.

[0010] In the past, electrolyte components such as solvents and safety additives that decompose to a large extent in the voltage range of secondary cells were largely discarded as far as possible. However, this severely limited the scope for development, since potentially interesting electrolyte components were not considered for use in cells at an early stage of development due to their instability.

[0011] A method for charging lithium batteries is known from DE 10 2014 219 421 A1.

[0012] An additive composition for rechargeable battery cells is known from DE 10 2016 013 809 A1.

[0013] A method for producing a lithium-ion battery cell is known from DE 10 2018 201 283 A1. Summary of the invention

[0014] The object of the present invention is to at least partially solve the problems listed with respect to the prior art. In particular, a method for forming a battery cell should be proposed, by which the provision of excessive amounts of additives, which has hitherto been considered necessary, can be avoided. Furthermore, the decomposition of second-class additives should be prevented. Furthermore, the freedom in the selection and development of the electrolyte should not be restricted.

[0015] A method having the features according to claim 1 contributes to achieving this object. Advantageous developments are the subject matter of the dependent claims. The features listed individually in the claims can be combined with one another in a technically meaningful manner and can be supplemented by explanatory details in the description and / or details in the drawings, which show further embodiments of the invention.

[0016] A method for forming a battery cell is proposed. The battery cell has a housing and at least one anode and a cathode arranged therein, a separator arranged therebetween, and an electrolyte, in particular a liquid electrolyte, at least partially surrounding the anode, cathode and separator. The method has at least the following steps:

[0017] a) providing a housing and an anode, a cathode and a separator arranged therein;

[0018] b) contacting the anode, cathode, and separator with a first composition of electrolyte to establish a first state of the battery cell;

[0019] c) charging the battery cell in the first state to a first voltage value between the anode and the cathode to establish a second state of the battery cell;

[0020] d) replenishing the first composition of the electrolyte in the housing with a second composition of the electrolyte that is different from the first composition to establish a third state of the battery cell.

[0021] The housing of a battery cell is, for example, a hard shell or a composite film for a soft pack cell. Anodes, cathodes and separators as electrodes are known components of a battery cell and are produced, for example, as conductive films coated with active materials. They can be arranged in a predetermined sequence in a stack in the battery cell. The housing is filled with an electrolyte, in particular a liquid electrolyte.

[0022] The battery cell is in particular a lithium-containing battery cell, in particular a secondary battery cell.

[0023] In particular, the battery cell is a known battery cell having known components arranged in a known manner relative to one another. The present application proposes a particularly advantageous method for forming a battery cell consisting of known components.

[0024] In particular, the sequential filling of the housing and the sequential formation of the battery cells are proposed. In this case, the composition of the electrolyte for the individual filling steps is selected in a targeted and suitable manner so that an electrolyte / electrode boundary phase or boundary layer can be formed intentionally.

[0025] For the first filling step of the method, i.e. step b), or for a subsequent filling step of the method, for example step d), the electrolyte composition is selected taking into account the potential of the respective electrode and the associated voltage present in the respective battery cell, in particular with regard to the targeted decomposition of electrolyte components and the associated formation of electrolyte / electrode boundary phases or boundary layers.

[0026] This enables the use of electrolyte components that were hitherto unavailable, such as additives, solvents and salts, in a subsequent filling step of the method, for example according to step d) or in a subsequent filling step of the method, for example step f).

[0027] In particular, the battery cell is initially filled with a first composition of an electrolyte which contains, in particular, additives of the first type known for passivating the anode.

[0028] After the charging step according to step c), the battery cell is further filled with the second composition in a second filling step, i.e. the first composition is replenished. The second composition comprises, for example, additives of the second type. In particular, the second composition is added only after the anode has been (at least partially) passivated, so that only a small amount of reduction of the additives of the second type still occurs, preferably no reduction. The addition of the second composition can be carried out within the following voltage range of the battery cell, within which the anode has a reduction potential, relative to which the additives of the second type are no longer decomposed. In addition, the additives of the second type are no longer decomposed in the subsequent charging step by the passivation of the anode carried out up to step d) and within the scope of steps b) and c).

[0029] In particular, after step d), the battery cell is further charged, stored or discharged at least once within the scope of step e). The storage can be carried out for a certain time interval together with a partial or complete discharge of the battery cell in order to establish a fourth state of the battery cell. Charging and storage and / or discharging can also be carried out in combination with one another.

[0030] In particular, after step e), within the scope of step f), the first and second compositions of the electrolyte are replenished with a third composition of the electrolyte that is different from the first and second compositions in order to establish a fifth state of the battery cell.

[0031] In particular, after the respective further filling, the further charging and / or storage of the battery cells takes place for a certain time interval.

[0032] In particular, further filling steps, charging steps and temperature storage steps can be carried out until the formation is completed. For example, additives can be added in the third filling step, for example according to step f), which additives cannot or should not decompose both at the anode and the cathode. Examples thereof can be overcharge additives, flame retardant additives or other electrolyte components.

[0033] The first composition of the electrolyte contains in particular an SEI additive, ie it is used to form an SEI on the anode. Examples of the first class of additives are organic carbonates, in particular the known VC (vinylene carbonate), FEC (fluoroethylene carbonate), VEC (vinylethylene carbonate).

[0034] The second composition of the electrolyte comprises in particular a CEI additive, ie it is used to form a CEI at the cathode. The second additive is, for example, a nitrile.

[0035] The third composition of the electrolyte contains in particular safety additives, in particular the known FPPN (pentafluoro(phenoxy)cyclotriphosphazene), TFP (tris(2,2,3-trifluoroethyl)phosphate), TFMP (bis(2,2,2-trifluoroethyl)methylphosphonate, FB (fluorobenzene), CHB (cyclohexylbenzene), and / or electrolyte components that are, for example, temperature-labile, in particular the known DTD, TMSP, MMDS) and / or easily decomposable electrolyte components, for example the known acetonitrile.

[0036] In particular, the first composition comprises no additives of the second type and / or no additives mentioned with respect to the third composition. In particular, the second composition comprises additives of the second type and additives mentioned with respect to the third composition.

[0037] In particular, the second composition comprises no additives of the first type and no additives mentioned with respect to the third composition.

[0038] In particular, due to the proposed method, it is not necessary to provide an excess of the second type of additive, since the anode is already passivated by contact with the first composition in the first charging step, i.e. within the scope of step c), after the first filling, i.e. within the scope of step b). As a result, the second type of additive is not or less reductively decomposed.

[0039] Due to the sequential filling and charging, in particular no adaptation of the desired electrolyte composition is required, so that the degrees of freedom in the development of the electrolyte are not restricted, but on the contrary even open up new development possibilities.

[0040] In the context of the second and / or third composition, the additives can in particular be added in concentrated form, so that the amount of liquid which is additionally added to the first composition is kept as low as possible.

[0041] In order to ensure a uniform distribution of the individual compositions within the battery cell or housing, various strategies can be used individually or in combination. In particular, a temperature storage step can be carried out after the housing is filled with the second composition and / or the third composition. In particular, the battery cell is stored for a certain time interval, for example for hours, days or even weeks, wherein the storage takes place in particular within a temperature interval or along a predeterminable temperature profile.

[0042] In particular, the housing is open to the environment at least during step d) or f), wherein excess electrolyte is removed from the housing prior to ready-to-use closure of the housing. In particular, gases generated during the formation of the SEI are removed.

[0043] In particular, the second filling of the battery cell according to step d) and / or the third filling according to step f) can be carried out with an excess of electrolyte, wherein the excess promotes thorough mixing of the various compositions. The excess can be discharged or sucked out when the battery cell is sealed under vacuum, for example.

[0044] Filling can therefore be carried out routinely on opened battery cells.

[0045] In particular, at least two or more than two compositions of the electrolyte can be arranged simultaneously in the housing, wherein at least one of the compositions is arranged in a container and is therefore arranged spatially separated from the anode, cathode, separator and at least one further composition in the housing. The container is opened after a certain time interval to thoroughly mix the compositions in the housing.

[0046] In particular, filling with the second composition and / or with the third composition can be carried out by means of an electrolyte bag, ie a closed container in which the respective composition is arranged.

[0047] During the production of the battery cell, the first composition is introduced into the housing, for example conventionally by means of at least one spray gun. In addition, before the housing of the battery cell is closed, at least one container is also introduced into the gas bag of the battery cell. The at least one container may contain further compositions, in particular second and / or third compositions, which are required at a later point in time to produce the desired composition of the ready-to-use battery cell.

[0048] In particular, the housing is closed immediately after the composition or the container has been arranged in the housing.

[0049] In particular, the at least one container is opened contactlessly.

[0050] The release of the second and / or third composition can be achieved by opening the container in question in a targeted manner. The targeted opening can occur, for example, by the action of pressure and / or temperature. The targeted opening can be carried out through a closed housing, i.e. contactlessly, i.e. without contacting the container.

[0051] In particular, after arranging the composition and before closing the housing, the pressure within the cell is reduced.

[0052] The advantage of using a container is that the housing does not have to be reopened for the second filling according to step d) and / or the third filling according to step f). Thus, the process chain can be kept essentially in its original form (i.e. filling the housing in a single step).

[0053] In particular, the first composition does not contain at least one additive, which is contained at least in the second composition. In particular, the second composition does not contain at least one additive, which is contained at least in the third composition.

[0054] In particular, the first voltage value is at least the lower trip voltage of the ready-to-use, formed battery cell, preferably at least 50% of the difference between the upper and lower trip voltages plus the lower trip voltage. In particular, the voltage value of the ready-to-use, formed battery cell, i.e. the rated voltage, is greater than 3.0 volts, particularly preferably greater than 3.2 volts. In particular, the voltage value of the ready-to-use, formed battery cell is at most 6 volts, preferably at most 5 volts.

[0055] In particular, the non-aqueous electrolyte consists of at least one non-aqueous solvent, at least one salt and at least one additive.

[0056] In particular, the second composition and / or the third composition comprises at least 10% by weight of additives which are not present in the first composition.

[0057] In particular, the third composition comprises additives that are not present in the first composition and the second composition.

[0058] In particular, the anode active material consists of a material that intercalates lithium ions or a material that forms a lithium alloy or a mixture thereof.

[0059] In particular, the anode comprises graphite.

[0060] In particular, the anode comprises silicon.

[0061] In particular, the anode comprises at least 30 wt. % silicon.

[0062] In particular, the cathode active material has an olivine structure, a spinel structure, or a layered oxide structure.

[0063] In particular, the cathode material having an olivine structure is lithium iron phosphate or lithium cobalt phosphate.

[0064] In particular, the cathode material having a spinel structure is lithium manganese oxide or lithium nickel manganese oxide.

[0065] In particular, the cathode material having a layered oxide structure is a lithium metal oxide. The metal may be one or more of the following elements: Ni, Co, Mn, Mg, Al, Fe, Zr, Mo, Nb, Cr, Ta, Sn, Zn, V, Ti.

[0066] In particular, at least one of the following additives is already included in the first composition: vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), methyl ethylene carbonate (MEC), methyl phenyl carbonate (MPC), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate (LiBF4), lithium tetrafluoro(oxalato)phosphate (LiTFOP), lithium difluorobis(oxalato)phosphate (LiDFBOP), lithium nitrate (LiNO3), lithium bis(fluorosulfonyl)imide (LiFSI), ethylene sulfite (ES), difluoromethyl acrylate (DFMA), 1,3,2-dioxathiolane 2,2-dioxide (DTD), 1,3-propane sultone (PS), methylene methanedisulfonate (MMDS), prop-1-ene-1,3-sultone (PES), and lithium difluorophosphate (LFO).

[0067] In particular, at least one of the following additives is already included in the second composition: lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate (LiBF4), lithium tetrafluoro(oxalato)phosphate (LiTFOP), lithium difluorobis(oxalato)phosphate (LiDFBOP), lithium nitrate (LiNO3), lithium bis(fluorosulfonyl)imide (LiFSI), ethylene sulfite (ES), difluoromethyl acrylate (DFMA), 1,3,2-dioxathiolane 2,2-dioxide (DTD), 1,3-propane sultone (PS), methylene disulfonate (MMDS), prop-1-ene-1,3-sultone (PES), tris(trimethylsilyl) phosphite (TMSPi ), tris(trimethylsilyl) phosphate (TMSP), lithium difluorophosphate (LFO), 4,5-dicyano-2-(trifluoromethyl)imidazole-1-lithium (LiTDI), pentafluoro(phenoxy)cyclotriphosphazene (FPPN), tris(2,2,2)-trifluoroethyl) phosphate (TFP), bis(2,2,2-trifluoroethyl) methylphosphonate (TFMP), fluorobenzene (FB), cyclohexylbenzene (CHB), acetonitrile (ACN), succinonitrile, adiponitrile, difluoroethyl carbonate (DiFEC), bis(2,2,2-trifluoroethyl) carbonate (TFEC), 2,2,3,4,4,4-hexafluorobutyl-methyl carbonate (HFBMC), 3-(1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoropropane (F-EPE), methyl carbonate (2,2,2-trifluoroethyl) ester (F-EMC).

[0068] In particular, at least one phosphazene-containing cyclic additive is included in the third composition.

[0069] In particular, the third composition includes at least one of the following additives: lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate (LiBF4), lithium tetrafluoro(oxalato)phosphate (LiTFOP), lithium difluorobis(oxalato)phosphate (LiDFBOP), lithium nitrate (LiNO3), lithium bis(fluorosulfonyl)imide (LiFSI), ethylene sulfite (ES), difluoromethyl acrylate (DFMA), 1,3,2-dioxathiolane 2,2-dioxide (DTD), 1,3-propane sultone (PS), methylene disulfonate (MMDS), prop-1-ene-1,3-sultone (PES), tris(trimethylsilyl) phosphite (TMSPi ), tris(trimethylsilyl) phosphate (TMSP), lithium difluorophosphate (LFO), 4,5-dicyano-2-(trifluoromethyl)imidazole-1-lithium (LiTDI), pentafluoro(phenoxy)cyclotriphosphazene (FPPN), tris(2,2,2)-trifluoroethyl) phosphate (TFP), bis(2,2,2-trifluoroethyl) methylphosphonate (TFMP), fluorobenzene (FB), cyclohexylbenzene (CHB), acetonitrile (ACN), succinonitrile, adiponitrile, difluoroethyl carbonate (DiFEC), bis(2,2,2,-trifluoroethyl) carbonate (TFEC), 2,2,3,4,4,4-hexafluorobutyl-methyl carbonate (HFBMC), 3-(1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoropropane (F-EPE), methyl (2,2,2-trifluoroethyl) carbonate (F-EMC).

[0070] In particular, the battery cells are rechargeable lithium-ion battery cells.

[0071] It should be noted in particular that each filling step causes time and costs. A two-step filling step, i.e. at least according to steps a) to d) or a) to e), can effectively reduce the decomposition problems of the second type of additives or the additives mentioned with respect to the third composition. A potential third filling step, for example according to step f), in particular causes new costs, but enables the use of electrolyte components or additives that were not available so far. Therefore, the cost / use potential is always taken into account.

[0072] In particular, the use of the indefinite article ("a" and "an") in the claims and the description thereof is to be understood as such and not as a numeral. Accordingly, the term or component introduced thereby is to be understood as presenting at least one, but in particular also a plurality may be present.

[0073] It should be noted as a precaution that the numerals used here ("first", "second", . . . ) serve primarily (only) to distinguish between a plurality of objects, dimensions or processes of the same type, i.e., in particular do not necessarily predetermine a dependency and / or sequence of these objects, dimensions or processes on one another. If a dependency and / or sequence is required, this is explicitly stated here or is obvious to a person skilled in the art when studying the specifically described configuration. If a component can occur in plurality ("at least one"), a description of one of these components may also apply to all or some of the plurality of these components, but this is not mandatory. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The invention and the technical field are explained in more detail below with the aid of the drawings. It should be noted that the invention is not to be restricted to the described embodiments. In particular, it is also possible to extract partial aspects of the situations illustrated in the drawings and to combine them with other components and insights from the present description, unless otherwise explicitly shown. It should be noted in particular that the drawings and in particular the dimensional ratios shown are only schematic. It is shown:

[0075] Figure 1 : First chart;

[0076] Figure 2 : Second chart;

[0077] Figure 3 : The third chart;

[0078] Figure 4 : Fourth diagram; and

[0079] Figure 5 : Implementation variants of battery cells. DETAILED DESCRIPTION

[0080] Figure 1 A first diagram is shown. On the vertical axis the voltage 22 in the battery cell 1 is plotted. On the horizontal axis the time 21 is plotted. The curve 23 schematically illustrates the course of the voltage 22 during charging.

[0081] According to step a) of the method, a housing 2 and an anode 3, a cathode 4 and a separator 5 arranged therein are provided. The voltage value of the voltage 22 at time zero is approximately 0 V. According to step b), the battery cell 1 is filled with a first composition 7, i.e. the anode 3, the cathode 4 and the separator 5 are in contact with a first composition 7 of an electrolyte 6, in order to establish a first state 8 of the battery cell 1 at time zero. According to step c), the battery cell 1 in the first state 8 is charged to a first voltage value 9 between the anode 3 and the cathode 4, in this case approximately 3.7 volts, in order to establish a second state 10 of the battery cell 1. According to step d), the first composition 7 of the electrolyte 6 is supplemented in the housing 2 with a second composition 11 of the electrolyte 6 which is different from the first composition 7, in order to establish a third state 12 of the battery cell 1. After step d), the battery cell 1 is further charged within the scope of step e) to a higher second voltage value 20, in this case approximately 4.2 volts, in order to establish a fourth state 14 of the battery cell 1.

[0082] Figure 2 A second diagram is shown. Figure 1 implementation method.

[0083] and Figure 1 Differently, after step d), within the scope of step e), the battery cell 1 is stored for a certain time interval 13 to establish a fourth state 14 of the battery cell 1. After step e), within the scope of step f), the first and second compositions 7, 11 of the electrolyte 6 are replenished with a third composition 15 of the electrolyte 6 which is different from the first and second compositions to establish a fifth state 16 of the battery cell 1.

[0084] Figure 3 A third diagram is shown. Figure 2 implementation method.

[0085] In this case, after step d), within the scope of step e), the battery cell 1 is further charged to a second, higher voltage value 20, here approximately 4.2 volts, and in parallel the battery cell 1 is stored for a certain time interval 13 in order to establish a fourth state 14 of the battery cell 1. After step e), within the scope of step f), the first and second compositions 7, 11 of the electrolyte 6 are replenished with a third composition 15 of the electrolyte 6 which is different from the first and second compositions in order to establish a fifth state 16 of the battery cell 1.

[0086] Figure 4 A fourth diagram is shown. Figure 3 implementation method.

[0087] and Figure 3According to step e), the battery cell 1 is discharged after charging to the second voltage value 20. When the fourth state 14 is reached, the voltage value is below the upper trip voltage. Only then, within the scope of step f), the first and second compositions 7, 11 of the electrolyte 6 are replenished with a third composition 15 of the electrolyte 6 which is different from the first and second compositions, in order to establish a fifth state 16 of the battery cell 1.

[0088] Figure 5 An embodiment variant of a battery cell 1 is shown, which comprises a housing 2 with an anode 3 and a cathode 4 arranged therein, a separator 5 arranged therebetween, and an electrolyte 6 , in particular liquid, having a first composition 7 , which at least partially surrounds the anode 3 , the cathode 4 and the separator 5 .

[0089] The two other compositions 11, 15 of the electrolyte 6 are arranged simultaneously in the housing 2, wherein the second composition 11 and the third composition 15 are each arranged in a container 18 and are therefore arranged spatially separated from the anode 3, the cathode 4, the separator 5 and the first composition 7 and the respective other composition 15, 11 in the housing 2. The container 18 can be opened after a certain time interval 13 in order to thoroughly mix the compositions 7, 11, 15 in the housing 2. The filling with the second composition 11 and with the third composition 15 is carried out by means of an electrolyte bag, i.e. a closed container 18 in which the respective composition 11, 15 is arranged.

[0090] During the production of the battery cell 1, the first composition 7 can be introduced into the housing 2 conventionally by means of at least one spray gun. In addition, the two containers 18 are placed together in the gas bag of the battery cell 1 before the housing 2 of the battery cell 1 is closed relative to the environment 17. The containers 18 can be opened together at a later time or at different times offset in time from one another to produce the desired composition of the ready-to-use battery cell 1.

[0091] After the composition 7 , 11 , 15 or the container 18 has been arranged in the housing 2 , the housing 2 is closed.

[0092] The container 18 is opened by the closed housing 2 , ie without contact.

[0093] The release of the second and third composition 11, 15 and the additives 19 contained therein can be achieved by targeted opening of the relevant container 18. The targeted opening can take place, for example, by the action of pressure and / or temperature.

[0094] Reference numerals list

[0095] 1 Battery Cell

[0096] 2 Housing

[0097] 3 Anode

[0098] 4 Cathode

[0099] 5 Diaphragm

[0100] 6 Electrolytes

[0101] 7. First Composition

[0102] 8 First State

[0103] 9 First voltage value

[0104] 10 Second State

[0105] 11. Second Composition

[0106] 12 Third State

[0107] 13 Time interval

[0108] 14 Fourth State

[0109] 15 Third Composition

[0110] 16 Fifth State

[0111] 17 Environment

[0112] 18 Container

[0113] 19 Additives

[0114] 20 Second voltage value

[0115] 21 Time

[0116] 22 Voltage

[0117] 23 Curve.

Claims

1. A method for forming a battery cell (1), wherein the battery cell (1) comprises a housing (2) and at least one anode (3) arranged therein, a cathode (4), a separator (5) arranged therebetween, and an electrolyte (6) at least partially surrounding the anode (3), the cathode (4) and the separator (5); wherein the method comprises at least the following steps: a) providing a housing (2) and an anode (3), a cathode (4) and a separator (5) arranged therein; b) contacting the anode (3), cathode (4) and separator (5) with a first composition (7) of an electrolyte (6) to establish a first state (8) of the battery cell (1); c) charging the battery cell (1) in the first state (8) to a first voltage value (9) between the anode (3) and the cathode (4) to establish a second state (10) of the battery cell (1); d) replenishing the first composition (7) of the electrolyte (6) in the housing (2) with a second composition (11) of the electrolyte (6) which is different from the first composition (7) to establish a third state (12) of the battery cell (1), At least two compositions (7, 11, 15) of an electrolyte (6) are arranged simultaneously in a housing (2), wherein at least one of these compositions (11, 15) is arranged in a container (18) and is thus arranged in the housing (2) spatially separated from an anode (3), a cathode (4), a separator (5) and at least one other composition (7, 11); wherein the container (18) is opened after a certain time interval (13) in order to thoroughly mix the compositions (7, 11, 15) in the housing (2).

2. The method according to claim 1, wherein after step d), within the scope of step e), the battery cell (1) is further charged at least once or the battery cell (1) is stored for a certain time interval (13) in order to establish a fourth state (14) of the battery cell.

3. The method according to claim 2, wherein after step e), within the scope of step f), the first composition (7) and the second composition (11) of the electrolyte (6) are supplemented with a third composition (15) of the electrolyte (6) which is different from the first composition (7) and the second composition (11) in order to establish a fifth state (16) of the battery cell (1).

4. The method according to any one of claims 1 to 3, wherein the housing (2) is closed immediately after the composition (7, 11, 15) is arranged in the housing (2).

5. The method according to any one of claims 1 to 3, wherein the container (18) is opened contactlessly.

6. The method according to any one of claims 1 to 3, wherein the first composition (7) is free of at least one additive (19) which is contained at least in the second composition (11).

7. The method according to any one of claims 1 to 3, wherein the first voltage value (9) is at least 50% of the second voltage value (20) of the ready-to-use formed battery cell (1).

8. The method according to any one of claims 1 to 3, wherein the battery cell (1) is a rechargeable lithium-ion battery cell.

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