DE102022112527A1 - Method and device for producing a separator for a battery cell - Google Patents

Abstract

The invention relates to a method for producing a separator (36) for a battery cell, which comprises the following steps:
- supplying a metallic, electrically conductive substrate (30),
- applying a slurry (38) of a solid separator, comprising a solid electrolyte, a polymer binder and a solvent, to the substrate (30),
- Drying the coated substrate (32) by inductively exciting and heating the metallic, electrically conductive substrate, and
- Sintering the dried, coated substrate (32), the metallic, electrically conductive substrate (30) being permanently bonded to the solids separator (38) by inductive excitation through a sintering process.
The invention further relates to a device (10) for producing such a separator (36) for a battery cell.

Description

The invention relates to a method and a device for producing a separator for a battery cell according to the preamble of the independent claims.

Lithium-ion batteries have attracted significant attention over the past two decades for a variety of applications in portable electronic devices such as cell phones and laptops. Due to the rapid market development of electric vehicles and grid energy storage, high-performance, low-cost lithium-ion batteries are currently one of the most promising options for large-scale energy storage.

A lithium-ion battery generally consists of a separator, a cathode and an anode. Currently, the electrodes are manufactured by dispersing fine powders of a battery electrode active material, a conductive agent and a binder in a suitable solvent. The dispersion can be applied to a current collector, e.g. B. a copper or aluminum metal foil can be applied and then dried at elevated temperature to remove the solvent. The cathode and anode sheets are then stacked or rolled, with the separator separating the cathode and anode to form a battery.

The production of separators for solid electrolytes is time-consuming, energy-intensive and therefore expensive. As a rule, such separators are manufactured on individual sheets, with a carrier material being coated with solid separator. The composite of carrier material and solids separator is then dried and the carrier material is removed, resulting in a green compact of the solids separator. This green compact is then further processed in a sintering process to create the finished solids separator. Since the production takes place from individual sheets, increased handling effort is also necessary when coating, drying and sintering the solids separator.

From the EP 3 836 253 A1 a method for producing an electrode based on an aqueous slurry is known. This involves applying an aqueous slurry to a carrier material and then drying it to remove moisture from the aqueous slurry.

From the EP 2 830 125 B1 a separator for an electrochemical cell, preferably for a lithium-ion battery, is known. The separator comprises a porous layer which comprises at least one organic binder and at least one functionalized aluminum oxide hydroxide of the general formula AIOOH, which is functionalized on its surface with at least 2.5% by weight of at least one silicon-containing organic compound. This separator is characterized by rapid liquid absorption, high porosity, good mechanical strength and very low shrinkage under thermal stress and enables a significant improvement in the safety of today's common lithium-ion batteries.

The invention is based on the object of simplifying the production of a separator for a battery cell and increasing the energy efficiency of production and the production speed.

• - Zuführen eines metallischen, elektrisch leitenden Substrates,
• - Auftragen eines Schlickers eines Feststoffseparators, umfassend einen Feststoffelektrolyt, einen Polymerbinder und ein Lösemittel, auf das Substrat,
• - Trocknen des beschichteten Substrates durch induktives Anregen und Erhitzen des metallischen, elektrisch leitenden Substrates, und
• - Sintern des getrockneten beschichteten Substrates, wobei das metallische, elektrisch leitende Substrat durch induktive Anregung mit dem Feststoffseparator durch einen Sinterprozess dauerhaft stoffschlüssig verbunden wird.

This task is solved by a method for producing a separator for a battery cell, which includes the following steps:

• - supplying a metallic, electrically conductive substrate,
• - applying a slurry of a solid separator, comprising a solid electrolyte, a polymer binder and a solvent, to the substrate,
• - Drying the coated substrate by inductively stimulating and heating the metallic, electrically conductive substrate, and
• - Sintering the dried coated substrate, whereby the metallic, electrically conductive substrate is permanently bonded to the solids separator through a sintering process by inductive excitation.

A slip is a liquid, mushy to viscous solvent-mineral mixture for the production of ceramic products. In the context of this patent application, drying is understood to mean the complete or partial removal of liquid from a moist slurry by evaporation or evaporation. In this context, sintering is understood to mean the heating of a fine-grained ceramic material, whereby the temperatures of the sintering process remain below the melting temperature of the main components, so that the shape of the workpiece is retained except for process-related shrinkage.

The method according to the invention enables a particularly simple, quick and cost-effective production of a separator. The slip is dried intensively and homogeneously from the inside out, which means that a particularly uniform structure of the solid electrolyte can be achieved.

The additional features listed in the dependent claims make advantageous improvements and further developments of the method for producing a separator for a battery cell specified in the independent claim possible.

In a preferred embodiment of the invention it is provided that the slurry of the solids separator is applied to both sides of the metallic, electrically conductive substrate. A coating on both sides is particularly advantageous because the inductive heating during drying and sintering occurs from the inside through the inductive heating of the metallic, electrically conductive substrate. This allows a particularly uniform structure to be achieved in the ceramic of the solids separator. In addition, it is possible to adjust the porosity of the ceramic of the solids separator during the drying process and/or the sintering process, whereby the mechanical and electrochemical properties can be specifically influenced.

In a further preferred embodiment of the invention it is provided that the metallic, electrically conductive substrate is supplied as strip material. By supplying a strip material, a particularly simple and cost-effective production of the separator is possible. In particular, the processing of the substrate and the slip is possible in a continuous process, whereby the production speed of the separator can be increased since manual handling effort for coating the substrate, loading a drying oven or loading a sintering oven can be eliminated.

According to an advantageous embodiment of the method, it is provided that drying takes place at a steady-state temperature below a sintering temperature of the slip. This allows the porosity of a green compact, i.e. the coated substrate before the sintering process, to be adjusted during drying in order to achieve the desired mechanical and electrochemical properties.

In an advantageous embodiment of the method it is provided that the substrate with the sintered coating is removed as strip material. This enables a particularly simple process for coating, drying and sintering, whereby the substrate with the sintered coating can be wound onto a receiving device, in particular a roll, a sleeve or a drum, in order to easily carry out a further manufacturing step in the production to be supplied to the battery. Alternatively, the sintered substrate can also be cut into the shape of the desired separators after the sintering process and fed as stackable piece goods to the next process step in the production of the battery.

In an advantageous improvement of the method, it is provided that the substrate with the sintered coating is briefly heated above a melting temperature after the sintering process. By briefly heating above the melting temperature, the connection between the solids separator and the metallic, electrically conductive substrate can be improved. In particular, the interface resistances between the metallic, electrically conductive substrate and the solid separator can be reduced by short-term melting. In addition, the short-term melting can reduce residual stresses in the substrate and/or the sintered coating in order to improve the durability of the separator and reduce the risk of mechanical or thermal damage to the separator during later operation of the battery.

According to a preferred embodiment of the method, it is provided that the metallic, electrically conductive substrate is coated, dried and the coating applied to the substrate is sintered in a continuous process. Due to the continuous process control, a strip material can be processed, which means that the metallic, electrically conductive substrate can be coated with short process times. In particular, with a continuous process there are no break times for loading and unloading a drying oven or loading a sintering oven. In addition, the application of the slip to the metallic, electrically conductive substrate is simplified, since this process is also continuous and enables a uniform, preferably double-sided coating of the metallic, electrically conductive substrate.

In a preferred embodiment of the invention it is provided that the metallic, electrically conductive substrate is a copper foil, a nickel foil or a composite foil. A copper foil or a nickel foil can be heated particularly easily using inductive excitation in order to dry and sinter the substrate.

In a further preferred embodiment of the invention it is provided that the slurry of the solid separator is an oxidic, ion-conducting material, preferably an oxidic, lithium-ion-conducting ceramic or glass ceramic, in particular lithium-lanthanum-zirconium oxide (LLZO), a lithium-aluminum-titanium phosphate, a lithium lanthanum titanate or a derivative. Lithium lanthanum zirconium oxide offers over elemental Lithium and other lithium compounds have the advantage that they are particularly chemically and mechanically stable. Furthermore, in a further improvement of the method, it is provided that in order to dry the coated substrate, the substrate is heated inductively and dry air and/or a process gas is additionally supplied. An atmosphere is created in the process room that is largely free of water vapor in order to avoid side reactions when drying and sintering the slip. An atmosphere that is largely free of water is understood to mean an atmosphere with a dew point of less than -20°C, preferably less than -40°C, particularly preferably less than -65°C. Alternatively or additionally, the atmosphere can also include process gases, in particular inert gases such as nitrogen, which prevent a reaction of water vapor with the slip during the tempering process. Alternatively, reactive process gases can also be used, which create a diffusion equilibrium and prevent the lithium from diffusing out of the slip.

• - Mittel zum Zuführen eines metallischen, elektrisch leitenden Substartes,
• - Mittel zum Auftragen eines Schlickers eines Feststoffseparators auf das Substrat,
• - Mittel zum induktiven Trocknen des beschichteten Substrates durch induktives Anregen und Erhitzen des metallischen, elektrisch leitenden Substrates,
• - Mittel zum Sintern des getrockneten, beschichteten Substrates, wobei das metallische, elektrisch leitende Substrat durch induktive Anregung mit dem Feststoffseparator durch einen Sinterprozess dauerhaft stoffschlüssig verbunden wird.

A further partial aspect of the invention relates to a device for producing a separator for a battery cell, comprising

• - means for supplying a metallic, electrically conductive substrate,
• - means for applying a slurry of a solids separator to the substrate,
• - means for inductively drying the coated substrate by inductively exciting and heating the metallic, electrically conductive substrate,
• - Means for sintering the dried, coated substrate, whereby the metallic, electrically conductive substrate is permanently bonded to the solids separator by inductive excitation through a sintering process.

Such a device enables the production of a separator for a battery in a simple manner.

In an advantageous embodiment of the device it is provided that the means for inductive drying of the coated substrate comprise a floating dryer. A float dryer enables particularly gentle drying of the coated substrate. In particular, the stresses introduced into the coated substrate during floating drying can be kept low, whereby the mechanical and thermal stability of the separator can be improved.

In a further improvement of the device it is provided that the means for inductively drying the coated substrate and/or the means for sintering the dried, coated substrate comprise a plurality of induction elements, the induction elements being arranged on different sides of the substrate. This enables an even heat input into the substrate. This enables very uniform drying, which results in an essentially homogeneous structure of the coated and dried substrate. Furthermore, heating on both sides enables the binding agent to migrate from the center of the slip to the surface, which can improve the electrochemical properties of the separator.

In a further improvement of the device it is provided that the means for inductive drying of the coated substrate have nozzles for supplying dry air or a process gas.

It is particularly preferred if the nozzles for supplying dry air and the induction elements are arranged alternately along a drying process path.

The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless stated otherwise in individual cases.

• 1 eine erfindungsgemäße Vorrichtung zur Herstellung eines Separators für eine Batteriezelle;
• 2 ein mit einem Feststoffseparator beschichtetes Substrat zur induktiven Trocknung und Sinterung; und
• 3 ein Ablaufdiagramm zur Durchführung eines erfindungsgemäßen Verfahrens zur Herstellung eines Separators für eine Batteriezelle.

The invention is explained below in exemplary embodiments using the associated drawings. Show it:

• 1 a device according to the invention for producing a separator for a battery cell;
• 2 a substrate coated with a solids separator for inductive drying and sintering; and
• 3 a flowchart for carrying out a method according to the invention for producing a separator for a battery cell.

1 shows a device 10 for producing a separator 36 for a battery cell. The device 10 comprises means 12, 14 for feeding a metallic, electrically conductive substrate 30, which comprise a first receiving device 12, in particular a roller, a mandrel on a clamping sleeve or a drum, on which the metallic, electrically conductive substrate 30 is in shape a strip material is wound and fed to the other components of the device 10. The means for feeding further comprise a first deflection roller 14, with which the metallic, electrically conductive substrate is deflected and a heater zone 24 for drying and subsequent sintering.

The device 10 further comprises means 20, 22 for applying a slurry 38 of a solids separator to the metallic, electrically conductive substrate. For this purpose, a first application unit 20 is provided in order to apply a slurry 38 of a solids separator to a first side of the metallic, electrically conductive substrate 30. The means 20, 22 for applying a slip 38 further comprise a second application unit 22 for applying the slip 38 of the solids separator to a second side of the metallic, electrically conductive substrate 30. The slurry 38 of the solids separator comprises a solvent, a solid electrolyte and a polymer binder. By applying the slip 38 to both sides of the metallic, electrically conductive substrate 30, the metallic, electrically conductive substrate 30, in particular a copper foil, an aluminum foil or a composite foil, which comprises a copper foil and/or an aluminum foil as well as additional metallic layers, becomes uniform coated on both sides.

The device 10 further comprises means 24, 26, 40, 42, 44 for inductively drying the coated substrate 32. The means include a drying unit 26, which comprises a plurality of induction elements 40, 42, 44. The drying unit 26 can additionally comprise one or preferably several nozzles 50, 52, 54, with which dry air or a process gas is blown into the drying unit 26. The induction elements 40, 42, 44 are preferably on both sides of the coated substrate 32 guided through the drying unit, in the drawing 1 , i.e. arranged above and below the coated substrate 32. Particularly preferred in the process direction through the drying unit 26 on both sides of the coated substrate 32 are alternating induction elements 40, 42, 44 for inductively stimulating and associated heating of the metallic, electrically conductive substrate 30 and nozzles 50, 52, 54 for blowing in dry air or a process gas.

The device 10 further comprises means 46, 48 for sintering the dried coated substrate 32, in particular a sintering unit 28, which adjoins the means 26, 40, 42, 44 for drying the coated substrate 32 in the process direction W. The means for sintering 46, 48 in particular include further induction elements 46, 48, which are also preferably arranged on both sides, ie above and below the substrate 34 to be sintered in the drawing. The means for sintering 46, 48 are in particular designed to further heat the temperature of the dried, coated substrate 32 from a steady-state temperature T _B for drying to a sintering temperature Ts of preferably 1000 ° C to 1200 ° C. Further nozzles 56, 58 can be arranged in the sintering unit 28 in order to also supply the sintering unit 28 with dry air or a process gas to optimize the sintering process. The means for sintering 46, 48 can also be set up to briefly heat the sintered substrate 34 after sintering to a temperature T _L above the sintering temperature, in particular to a temperature of more than 1200 ° C, in order to briefly prevent melting at the connection point between the metallic, electrically conductive substrate 30 and the solid separator 38, whereby internal stresses in the sintered substrate 34 can be reduced and the contact resistance between the metallic, electrically conductive substrate 30 and the solid separator 38 can be reduced.

The means for drying 26, 40, 42, 44 and the means for sintering 46, 48 can be formed in a common heating zone 24, in particular as parts of a float dryer 62 or a continuous furnace 64.

The device 10 further comprises a second deflection roller 16, with which the sintered substrate 34 is led out of the heating zone 24 and fed to a second receiving device 18, in particular a further roller, a drum or a sleeve on a mandrel, on which the substrate 34 is fed with the Sintered coating can be rolled up for further processing.

The device 10 further comprises a control device 70 with a memory unit 72 and a computing unit 74. A machine-readable program code 76 for controlling the device and for executing a method according to the invention is stored in the memory unit 72. The control device 70 is set up to carry out a method according to the invention for producing a separator 36 with the device 10 described when the machine-readable program code 76 is executed by the computing unit 74.

2 shows a coated substrate 32 in a drying and a subsequent sintering process. A metallic, electrically conductive substrate 30, in particular a copper foil or an aluminum foil, is coated at least on one side with a slip 38 of a solids separator. An induction element 40, 42 is arranged on both sides of the coated substrate 32 in order to heat the metallic, electrically conductive substrate 30 by inductive excitation A and to dry the slip 38. In this way, a dried, coated substrate 32 is produced, which is heated and sintered in a subsequent process step by further inductive excitation of the metallic, electrically conductive substrate 30, so that a sintered substrate 34 is created, which is cohesively bonded to the metallic, electrically conductive Substrate 30 is connected.

3 shows a flowchart for carrying out a method according to the invention for producing a separator 36 for a battery cell. In a first method step <100>, a metallic, electrically conductive substrate 30 is fed to a coating process. This is preferably done in the form of a strip material which is unwound from a first roll 12 of the device 10. In a method step <110>, a slurry 38 of a solids separator is applied to a first side of the metallic, electrically conductive substrate 30 using a first application unit 20. Subsequently, in a method step <120>, a slurry 38 of a solids separator is applied to a second side of the metallic, electrically conductive substrate 30 using a second application unit 22. The application of the slip 38 to the two sides of the metallic, electrically conductive substrate 30 can also take place in parallel. In a simplified embodiment of the method, the metallic, electrically conductive substrate 30 can also be coated with a slip on only one side, so that one of the method steps <110> or <120> can be omitted.

In a method step <130>, the substrate 32 coated with the slip 38 is fed to a heating zone 24, which includes a drying unit 26 and a sintering unit 28. The drying unit 26 and the sintering unit 28 are preferably arranged together in a common housing, so that the coated substrate 32 is continuously heated and dried in a process step <140> by inductive excitation of the metallic, electrically conductive substrate 30. In a process step <150> following the drying, the coated substrate 32 is sintered by inductively heating the metallic, electrically conductive substrate 30 and/or the slip/solids separator (38), so that a mechanically stable sintered separator (36) is created. In a further method step <160>, the substrate 3 can be briefly heated above a melting temperature, which causes melting in the connection area between the metallic, electrically conductive substrate 30 and the solid separator 38, whereby the contact resistance and the internal stresses can be reduced. This allows both the mechanical strength and the thermal stability of the separator 36 to be increased.

Reference symbol list

10

contraption

12

first recording device

14

first pulley

16

second deflection roller

18

second recording device

20

first application unit

22

second application unit

24

Heating zone

26

Drying unit

28

Sintering unit

30

metallic, electrically conductive substrate

32

coated substrate

34

Substrate with sintered coating

36

separator

38

Slurry/solids separator

40

first induction element

42

second induction element

44

third induction element

46

fourth induction element

48

fifth induction element

50

first nozzle

52

second nozzle

54

third nozzle

56

fourth nozzle

58

fifth nozzle

60

Process room

62

Float dryer

64

Continuous oven / belt oven

70

Control unit

72

Storage unit

74

Computing unit

76

machine-readable program code

A

Area excited by induction

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 3836253 A1 [0005]
• EP 2830125 B1 [0006]

Claims (15)

Method for producing a separator (36) for a battery cell, comprising the following steps: - supplying a metallic, electrically conductive substrate (30), - applying a slurry (38) of a solid separator, comprising a solid electrolyte, a polymer binder and a solvent, to the substrate (30), - Drying the substrate (32) coated with the slip (38) by inductively stimulating and heating the metallic, electrically conductive substrate (30), and - Sintering the dried, coated substrate (32), the metallic, electrically conductive substrate (30) being permanently bonded to the solids separator (38) by inductive excitation through a sintering process. Method for producing a separator (36) for a battery cell Claim 1 , wherein the slurry (38) of the solids separator is applied to both sides of the metallic, electrically conductive substrate (30). Method for producing a separator (36) for a battery cell Claim 1 or 2 , wherein the metallic, electrically conductive substrate (30) is supplied as strip material. Method for producing a separator (36) according to one of Claims 1 until 3 , drying taking place at a steady-state temperature (T _B ) below a sintering temperature (Ts) of the slip (38). Method for producing a separator (36) according to one of Claims 1 until 4 , wherein the substrate (34) with the sintered coating is removed as strip material. Method for producing a separator (36) according to one of Claims 1 until 5 , wherein the substrate (34) with the sintered coating is briefly heated above a melting temperature (T _L ) after the sintering process. Method for producing a separator (36) according to one of Claims 1 until 6 , wherein the metallic, electrically conductive substrate (30) is coated in a continuous process, dried and the coating applied to the substrate (30) is sintered. Method for producing a separator (36) according to one of Claims 1 until 7 , wherein the metallic, electrically conductive substrate (30) is a copper foil, a nickel foil or a composite foil. Method for producing a separator (36) according to one of Claims 1 until 8th , wherein in order to dry the coated substrate (32), the substrate (30) is heated inductively and dry air and/or a process gas is additionally supplied. Method for producing a separator (36) according to one of Claims 1 until 9 , wherein the slurry (38) of the solid separator comprises an oxidic, ion-conducting material, in particular a lithium lanthanum zirconium oxide, a lithium aluminum titanium phosphate, a lithium lanthanum titanate or a derivative. Device (10) for producing a separator (36) for a battery cell, comprising - means (12, 14) for supplying a metallic, electrically conductive substrate (30), - means (20, 22) for applying a slurry (38) of a solids separator to the substrate (30), - Means (26, 40, 42, 44) for inductively drying the substrate (32) coated with the slip (38) by inductively exciting and heating the metallic, electrically conductive substrate (30), - Means (46, 48) for sintering the dried, coated substrate (32), the metallic, electrically conductive substrate (30) being permanently bonded to the solids separator (38) by inductive excitation through a sintering process. Device according to Claim 11 , wherein the means (26, 40, 42, 44) for inductive drying of the coated substrate comprise a float dryer (62). Device according to Claim 11 or 12 , wherein the means (26, 40, 42, 44) for inductively drying the coated substrate (32) and / or the means for sintering (46, 48) of the dried, coated substrate (32) comprise a plurality of induction elements (40, 42, 44 , 46, 48), at least two of the induction elements (40, 42, 44, 46, 48) being arranged on different sides of the coated substrate (32). Device according to one of the Claims 11 until 13 , wherein the means (26, 40, 42, 44) for inductive drying of the coated substrate (32) have nozzles (50, 52, 54, 56, 58) for supplying dry air or a process gas. Device according to Claim 13 and Claim 14 , whereby the nozzles (50, 52, 54, 56, 58) for supplying dry air and the induction elements (40, 42, 44, 46, 48) are arranged alternately along a process path (W) for drying.

Images