DE102018217756A1 - Method for producing an electrode unit for a battery cell and battery cell - Google Patents

Abstract

The invention relates to a method for producing an electrode unit (10) for a battery cell, which has an anode (21) and a cathode (22), at least one porous and electronically insulating coating (50) on the anode (21) and / or is applied to the cathode (22) by means of a spraying process or a vapor deposition process, and the anode (21) and the cathode (22) are placed on top of one another in such a way that the at least one coating (50) removes the anode (21) from the cathode ( 22) separates. The invention also relates to a battery cell which comprises at least one electrode unit (10) which is produced by the method according to the invention.

Description

The invention relates to a method for producing an electrode unit for a battery cell, the electrode unit having an anode and a cathode, and at least one porous and electrically insulating coating being applied to the anode and / or to the cathode. The invention also relates to a battery cell which comprises at least one electrode unit which is produced by the method according to the invention.

State of the art

Electrical energy can be stored using batteries. Batteries convert chemical reaction energy into electrical energy. In particular, rechargeable batteries are known. For example, lithium-ion battery cells are used in an accumulator. These are characterized, among other things, by high energy densities, thermal stability and extremely low self-discharge. Lithium-ion battery cells are used in motor vehicles, in particular in electric vehicles (EV), hybrid vehicles (hybrid electric vehicles, HEV) and plug-in hybrid vehicles (plug-in hybrid electric vehicles, PHEV). A battery comprises one or more battery cells.

Lithium-ion battery cells have electrode units. An electrode unit has a positive electrode, which is also referred to as a cathode, and a negative electrode, which is also referred to as an anode. The cathode and the anode each comprise a current collector and an active material layer, which has an electrochemical active material. The active material for the cathode contains, for example, a simple metal oxide such as Li ₂ MnO ₃ , that is lithium manganese oxide, or also NCM, that is an oxide of three metals, here nickel, cobalt and manganese. The active material for the anode contains, for example, silicon, graphite, lithium or a mixture of these substances.

In the manufacture of an electrode unit for a battery cell, layers of the anode and layers of the cathode are placed on one another with the interposition of a separator, or are wound around one another. The separator has the function of maintaining the distance between the layers of the anode and the cathode in order to electronically isolate the layers from one another and thus to avoid internal short circuits. The separator is also permeable to ions to ensure charge transport. In order to achieve these functions, polyethylene, polypropylene or combinations of these materials are used in particular as separators.

In order to obtain a high energy density of an electrode unit and a battery cell, the separator is designed as a film that is as thin as possible. It is also known not to place the separator as an independent film between the anode and cathode but rather to apply the separator to one of the electrodes in the form of a porous and electronically insulating coating.

A generic method for producing an electrode unit for a battery cell is, for example, from the documents US 2013/052509 A1 such as DE 10 2012 214 844 A1 known. Electrically non-conductive particles are distributed in a viscous electrolyte. Then a layer of the resulting electrolyte-particle mixture is applied to the surface of the anode and / or the cathode. The anode and the cathode are then pressed together, with the layer of the electrolyte-particle mixture in between.

From the document US 2014/0363738 A1 an electrochemical cell is known which comprises a separator with a plurality of layers of glass and ceramic particles. The separator is produced from a mixture of an organic polymer material, glass and ceramic particles as well as a solvent.

Disclosure of the invention

A method for producing an electrode unit for a battery cell is proposed. The electrode unit has an anode, that is, a negative electrode, and a cathode, that is, a positive electrode. According to the method, at least one porous and electronically insulating coating is first applied to the anode and / or to the cathode by means of a spraying process or a vapor deposition process. The coating is also ionically conductive at the latest after wetting with an electrolyte, i.e. permeable to lithium ions.

The vapor deposition process applies electronically insulating, porous wettable powders or layers to a surface of the anode and / or the cathode. Depositions from the gas phase, for example PVD or sputtering, from the liquid phase, for example spray coating or slurry + blend, and a dry coating can be used for this purpose.

This porous, electronically insulating layer can consist, for example, of a metal oxide, in particular aluminum oxide. For application processes such as sputtering, pulsed laser deposition (PLD) and similar, targets made of aluminum oxide can be used directly, for example. In order to obtain a porous layer, the gas pressure should, for example, be greater than 1 mbar and the gas should consist of air or pure oxygen, for example. In particular, the pressure during sputtering and / or vapor deposition and / or laser deposition can be atmospheric pressure. In particular, the layer can be applied directly after the drying process of the electrode material while it is still on the roll. The electrode foil can be guided roll-to-roll through a corresponding vapor deposition system and can thus be steamed in a continuous process. Alternatively, in the case of an electrode stack, each anode and / or cathode can also be vaporized individually before the stacking process. In particular, the layer applied in this way can reach a thickness of 0.1 to 10 micrometers.

The anode and the cathode are then placed on top of one another in such a way that the at least one coating separates the anode from the cathode. The anode and the cathode are preferably placed directly one on top of the other, so in particular no additional separator in the form of an additional film is placed between them. The anode and the cathode together with the at least one coating in between already form an electrode unit.

The anode and the cathode, together with the at least one coating in between, can be wound further to form an electrode coil, which is also referred to as a jelly roll. Only two roles, one role with the anode and one role with the cathode, are to be positioned one above the other. An additional role for a separator is not necessary. The manufacture of the electrode coil is thus advantageously simplified.

The anode and the cathode can also be cut into segments together with the at least one intermediate coating, and the segments can be stacked to form an electrode stack. In the following, anode segments and cathode segments only have to be stacked alternately. Additional separator segments are not required. The manufacture of the electrode stack is thus advantageously simplified.

According to an advantageous embodiment of the invention, the at least one coating is impregnated with a liquid electrolyte after the anode and the cathode have been placed on top of one another. The electrolyte penetrates into the pores that are contained in the coating, thereby increasing the ionic conductivity within the electrode unit or thereby enabling ionic conduction between the anode and cathode. In particular, but not exclusively, a carbonate-containing electrolyte, consisting for example of ethylene carbonate, dimethyl carbonate and / or diethyl carbonate with a conductive salt, for example lithium hexafluorophosphate and other additives such as vinylene carbon, can be used as the electrolyte.

The electrode unit is preferably first inserted into a cell housing of a battery cell, and then the cell housing is filled with the liquid electrolyte. Thus, the anode and the cathode are surrounded by the liquid electrolyte. The liquid electrolyte penetrates particularly into the pores of the coating and the electrodes.

The at least one coating comprises a material which is electronically insulating, porous and optionally, but not necessarily, ionically conductive. The at least one coating preferably has an oxide or consists of an oxide. Of particular interest, but not exclusively, as the material for the coating are the oxides of the following chemical elements and combinations thereof: Si, Al, Ti, Zr, Sc, Y, V, Nb, Cr, Mo, W, Sn.

The thickness and the manufacturing process of the at least one coating should in particular be chosen so that a dense layer of material is formed, which has pores in the order of a few nanometers to micrometers, depending on the desired functionality. The at least one coating preferably has a thickness in a range between 100 nm and 10 μm. Depending on the process, the pore structure of the at least one coating can be adjusted by various parameters such as pressure, temperature or precursor material of the targets.

According to an advantageous embodiment of the invention, the anode has a current conductor on which an anodic active material layer is applied. The current collector of the anode is made electrically conductive and made of a metal, for example copper. The at least one coating is applied to the anodic active material layer. The anodic active material layer is thus between the current collector of the anode and the coating.

According to an advantageous development of the invention, an anodic active material layer is applied to the current conductor of the anode on both sides. A coating is applied to both sides of the anodic active material layers. It is also conceivable that only on one of the two anodic active material layers is coated.

According to a further advantageous embodiment of the invention, the cathode has a current conductor on which a cathodic active material layer is applied. The current conductor of the cathode is made electrically conductive and made of a metal, for example aluminum. The at least one coating is applied to the cathodic active material layer. The cathodic active material layer is thus between the current conductor of the cathode and the coating.

According to an advantageous development of the invention, a cathodic active material layer is applied to the current conductor of the cathode on both sides. A coating is applied to both sides of the cathodic active material layers. It is also conceivable that a coating is applied only to one of the two cathodic active material layers.

According to a further advantageous embodiment of the invention, at least one coating is applied to the anode and at least one coating is applied to the cathode. The coatings are applied in particular to the anodic active material layer and to the cathodic active material layer.

According to an advantageous development of the invention, the coating applied to the anode and the coating applied to the cathode have different materials. In particular, the coating applied to the anode and the coating applied to the cathode have oxides of different chemical elements, for example aluminum oxide and zirconium oxide.

A battery cell is also proposed which comprises at least one electrode unit which is produced by the method according to the invention.

Advantages of the invention

The costs for producing an electrode unit are advantageously reduced by the method according to the invention. The application of a coating to the anode and / or to the cathode can be carried out simply and inexpensively by means of the spraying process and by means of the vapor deposition process. Basically, applying a coating to the anode and / or to the cathode is less expensive than producing a conventional separator in the form of a film.

In the case of an electrode unit produced by the method according to the invention, no additional separator is required. The coating functions as a conventional separator. The coating creates the required distance between the anode and the cathode and thus prevents short circuits. The coating is permeable for ion transport and inert in contact with other cell components. The coating takes up less space than conventional separators, which means higher energy densities can be achieved. Savings in volume of the electrode unit of 5% - 15% compared to a conventional electrode unit are realistic. The coating does not contract at elevated temperatures, so there is no shrinkage as with conventional separators, which has safety-related advantages. In particular, short circuits between the anode and cathode are avoided, which can occur in the case of shrinking separators and can cause the battery cell to run thermally. The ionic cell resistance is reduced, which results in a higher power density of the electrode unit. The manufacturing process of the electrode unit becomes cheaper. To produce an electrode coil, only two rollers, one roller with the anode and one roller with the cathode, have to be positioned one above the other. An additional role for a separator is not necessary. To produce an electrode stack, anode segments and cathode segments only have to be stacked alternately. Additional separator segments are not required.

A faster filling of the battery cell with electrolyte is also possible under certain circumstances, since it may not be necessary to fill relatively small pores with diameters in the range of 10 nm of a conventional separator. The amount of electrolyte required in the battery cell is also advantageously reduced since the coating has a smaller volume. This further reduces costs and weight and at the same time increases safety, since in the event of a fault, less electrolyte can react with active material or burn with atmospheric oxygen. The coating and material properties per se have better safety behavior, since they do not contract when the temperature rises and even under crash conditions due to greater mechanical stability, failure of the electrode unit is delayed. With a suitable choice of the material of the coating, a further increased specific ionic conductivity is to be expected due to the "soggy sand" effect, which describes the formation of space charge zones along a percolated ion transport path along which the cation conductivity is increased due to adsorption of the anions. Because of the lesser Thickness and reduced tortuosity of the coating can be expected with a reduced ionic resistance of the electrode unit. This further increases the power density of the battery cell. The higher specific conductivity and the reduced ionic resistance also improve the behavior of the battery cell during rapid charging.

Embodiments of the invention are explained in more detail with reference to the drawings and the description below.

• 1 eine schematische Darstellung einer Batteriezelle und
• 2 eine schematische Schnittdarstellung einer Elektrodeneinheit.

Show it:

• 1 a schematic representation of a battery cell and
• 2nd is a schematic sectional view of an electrode unit.

Embodiments of the invention

In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference symbols, and a repeated description of these elements is dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

1 shows a schematic representation of a battery cell 2nd . The battery cell 2nd comprises a cell housing 3rd , which is prismatic, in the present case cuboid. The cell housing 3rd is electrically conductive in the present case and made, for example, of aluminum. The cell housing 3rd but can also be made of an electrically insulating material, for example plastic.

The battery cell 2nd includes a negative terminal 11 and a positive terminal 12th . Via the terminals 11 , 12th can one from the battery cell 2nd provided voltage can be tapped. Furthermore, the battery cell 2nd via the terminals 11 , 12th also be loaded.

Inside the cell housing 3rd the battery cell 2nd is an electrode unit 10th arranged, which is designed for example as an electrode stack or as an electrode coil. The electrode unit 10th has two electrodes, namely an anode 21 and a cathode 22 , on. The anode 21 and the cathode 22 are each foil-like and have a coating 50 separated from each other. The coating 50 is porous, electronically insulating and permeable to lithium ions over the electrolytes in the pores.

The anode 21 comprises an anodic active material layer 41 and a current arrester 31 . The current arrester 31 the anode 21 is electrically conductive and made of a metal, such as copper. The current arrester 31 the anode 21 is electrical with the negative terminal 11 the battery cell 2nd connected.

The cathode 22 comprises a cathodic active material layer 42 and a current arrester 32 . The current arrester 32 the cathode 22 is electrically conductive and made of a metal, such as aluminum. The current arrester 32 the cathode 22 is electrical with the positive terminal 12th the battery cell 2nd connected.

In the cathodic active material layer 42 the electrode unit 10th lithium atoms are stored. When the electrode unit is being charged 10th in the battery cell 2nd lithium ions migrate from the cathodic active material layer 42 through the coating 50 to the anodic active material layer 41 . The lithium ions in the anodic active material layer 41 stored. This process is also known as lithiation. At the same time, electrons flow from the cathode in an external circuit 22 to the anode 21 .

When operating the battery cell 2nd , that is, when the electrode unit is being discharged 10th , electrons flow from the anode in an external circuit 21 to the cathode 22 . Inside the electrode unit 10th lithium ions migrate from the anodic active material layer 41 through the coating 50 to the cathodic active material layer 42 . The lithium ions are deposited from the anodic active material layer 41 reversible, which is also called delithiation.

2nd shows a schematic sectional view of an electrode unit 10th which is an anode 21 and a cathode 22 includes. On the cathode 22 is a coating 50 upset. The anode 21 and the cathode 22 are placed on top of each other in such a way that they are on the cathode 22 applied coating 50 the anode 21 from the cathode 22 separates. On the anode 21 is another coating 50 upset. The further coating 50 is the cathode 22 arranged facing away.

On the current arrester 32 the cathode 22 is a cathodic active material layer on both sides 42 upset. The coating is present 50 on one of the two cathodic active material layers 42 upset. The coating 50 on the cathodic active material layer 42 is the anode 21 arranged facing.

On the current arrester 31 the anode 21 is an anodic active material layer on both sides 41 upset. The further coating is present 50 on one of the two anodic Active material layers 41 upset. The further coating 50 on the anodic active material layer 41 is the cathode 22 arranged facing away.

The electrode unit shown here 10th thus comprises in the following order: a cathodic active material layer 42 , a current arrester 32 the cathode 22 , another cathodic active material layer 42 , a coating 50 , an anodic active material layer 41 , a current arrester 31 the anode 21 , another anodic active material layer 41 and another coating 50 .

The coatings 50 on the anode 21 and on the cathode 22 are relatively thin and each have a thickness between 100 nm and 10 microns. For example, the coating 50 on the cathode 22 aluminum oxide as the material, and the further coating 50 on the anode 21 has silicon oxide as the material. The one on the cathode 22 applied coating 50 and the on the anode 21 applied further coating 50 thus have different materials.

In the present case, the electrode unit shown here comprises 10th an anode 21 in the form of a cut anode segment and a cathode 22 in the form of a cut cathode segment. The one on the cathode 22 applied coating 50 and the on the anode 21 applied further coating 50 are each in the form of a cut coating segment.

Several such anode segments and cathode segments can be stacked together with the coating segments to form an electrode stack. During stacking, the anode segments and the cathode segments are alternately arranged one above the other in such a way that in each case a coating segment lies between an anode segment and a cathode segment and separates the anode segment from the cathode segment.

It is also conceivable that the electrode unit 10th an anode 21 in the form of a ribbon-shaped anode element and a cathode 22 in the form of a band-shaped cathode element. The one on the cathode 22 applied coating 50 and the on the anode 21 applied further coating 50 are in the form of a band-shaped coating element.

The band-shaped anode element and the band-shaped cathode element can then be wound together with the coating elements to form an electrode coil, which is also referred to as a jelly roll. The band-shaped anode element and the band-shaped cathode element are arranged in such a way that in each case a coating element lies between the anode element and the cathode element and separates the anode element from the cathode element.

The invention is not restricted to the exemplary embodiments described here and the aspects emphasized therein. Rather, a large number of modifications are possible within the scope specified by the claims, which lie within the framework of professional action.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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.

Patent literature cited

• US 2013052509 A1 [0006]
• DE 102012214844 A1 [0006]
• US 2014/0363738 A1 [0007]

Claims (11)

Method for producing an electrode unit (10) for a battery cell (2), which has an anode (21) and a cathode (22), wherein at least one porous and electronically insulating coating (50) is applied to the anode (21) and / or to the cathode (22) by means of a spraying process or a vapor deposition process, and wherein the anode (21) and the cathode (22) are placed on top of one another such that the at least one coating (50) separates the anode (21) from the cathode (22). Procedure according to Claim 1 , After the anode (21) and the cathode (22) have been placed on top of one another, the at least one coating (50) is impregnated with a liquid electrolyte. Method according to one of the preceding claims, wherein the at least one coating (50) comprises an oxide. Method according to one of the preceding claims, wherein the at least one coating (50) has a thickness in a range between 100 nm and 10 µm. Method according to one of the preceding claims, wherein the anode (21) has a current conductor (31) to which an anodic active material layer (41) is applied, and wherein the at least one coating (50) is applied to the anodic active material layer (41). Procedure according to Claim 5 , wherein an anodic active material layer (41) is applied to both sides of the current conductor (31) of the anode (21), and a coating (50) is applied to both sides of the anodic active material layers (41). Method according to one of the preceding claims, wherein the cathode (22) has a current conductor (32) to which a cathodic active material layer (42) is applied, and wherein the at least one coating (50) is applied to the cathodic active material layer (42). Procedure according to Claim 7 , a cathodic active material layer (42) being applied to both sides of the current conductor (32) of the cathode (22), and a coating (50) being applied to both sides of the cathodic active material layers (42). Method according to one of the preceding claims, wherein at least one coating (50) is applied to the anode (21), and at least one coating (50) is applied to the cathode (22). Procedure according to Claim 9 , wherein the coating (50) applied to the anode (21) and the coating (50) applied to the cathode (22) have different materials. Battery cell (2) comprising at least one electrode unit (10) which is produced by the method according to one of the preceding claims.

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