DE102020101112A1 - Battery cells with surface-structured active material and process for their production - Google Patents

Abstract

The present invention relates to a battery cell (20), in particular a Li-ion cell, with at least two electrodes and separators arranged between the electrodes and an electrolyte, the electrodes each having at least one conductor and a plurality of electrode layers (1), as well as a casing (21) which tightly encloses components of the battery cell (20). The battery cell (20) is characterized in that the electrode layer (1) has an at least two-layer structure with a carrier layer (3) and at least one electrode layer (2) arranged thereon, with one surface (9) of the electrode layer (1) a structure is provided with cavities (8) which have a predetermined structure depth (10) of more than 30% of an electrode layer thickness (12)

Description

The present invention relates to a battery cell, in particular a Li-ion cell, with at least two electrodes, as well as separators arranged between the electrodes and an electrolyte, the electrodes each having at least one arrester and a plurality of electrode layers, as well as a casing that contains the Tightly encloses components of the battery cell. In particular, a method for producing the surface structures is also specified.

In the prior art, batteries are known which consist of a plurality of battery cells. Batteries of this type are increasingly required to provide electrical energy for mobile applications or transport tasks. In particular, the provision of electrical energy for the operation of vehicles for the transport of people and goods requires the provision of relatively large amounts of energy in order to ensure the required range of the vehicles. The battery cells are galvanic cells that are able to store electrical energy through chemical conversion and, if necessary, reverse this storage process, whereby energy can then be released again through a further chemical conversion. This process of chemical storage of electrical energy and the subsequent reversal of this process for energy release is also known as a cycle. The aim here is, for example, to design batteries in such a way that they are particularly durable, i. H. can run through a steadily increasing number of charge and discharge cycles and function properly with a storage capacity that is as constant as possible. In addition, there is a requirement that battery cells should be able to store the largest possible amount of energy in the shortest possible time and then be able to release it again. This property is also known as loading capacity or storage capacity. There are basically two ways of increasing the storage capacity of batteries and the battery cells built into them. On the one hand, the number of battery cells used can be increased. Another possibility is to increase the capacity of the individual battery cells, for example by increasing the geometric dimensions.

However, these previously known solutions have different disadvantages. For example, as a result of the implementation of the known solutions, the batteries are larger, heavier and more expensive.

The object of the present invention is therefore to at least partially solve the problems arising from the prior art. In particular, to provide a battery with an improved storage capacity.

To achieve these objects, a battery with the features according to the independent patent claims is proposed. Advantageous further developments are the subject of the dependent claims. The features listed individually in the patent claims can be combined with one another in a technologically sensible manner and can be supplemented by explanatory facts from the description and / or details from the figures, with further design variants of the invention being shown.

In the present case, a battery cell is proposed which can in particular be designed as a lithium-ion cell and has at least two electrodes and separators arranged between the electrodes. The battery cells furthermore comprise an electrolyte, at least one conductor on each electrode and a casing which tightly encloses these components of the battery cells. The arresters protrude at least partially from the casing in order to form the electrical connection poles of the battery cells. The electrodes of the battery cell each have a plurality of electrode layers which are arranged close to one another and which are electrically separated from the separators. Electrode layers can also be referred to as electrode foils. Each of these electrode layers has an at least two-layer structure which includes at least one carrier layer and an electrode layer arranged thereon. It is provided that the surface of the respective electrode layer has a structure with deep cavities. The cavities are designed in such a way that they have a structure depth that is more than 30% of an electrode layer thickness. In particular, the cavities produced in this way can achieve a type of porosity which is advantageous for the function of the electrode layer.

The electrode layer thickness is the geometric extension of the electrode layer in the normal direction to its surface. In the installed state, one side of the surface of the web-shaped electrode layer is in contact with the carrier layer and the opposite side of the surface is in contact with the surface of a separator adjoining it. The only exceptions to this are external electrode layers, provided that they are not enclosed by a separator on their outside. The electrode layer thickness is thus the measure of length that indicates the shortest distance from one surface of the electrode layer to its opposite surface.

In the present case, “cavities” are to be understood as indentations that extend from the surface of the Extending the electrode layer starting into this. The structure depth is the geometric length measured from the surface to the deepest point of the cavity. Because of the scatter and production fluctuations which occur in practice, one can also speak of mean or average structure depths and electrode layer thicknesses in connection with the present invention. In this case, the arithmetic mean of the respective measured values would have to be used.

By providing the surface of the electrode layer with a structure, the cavities of which have a structure depth of more than 30%, preferably more than 50%, of the electrode layer thickness, the respective electrode layer can be penetrated much better by the electrolyte present in the battery cells. This is expressed in the fact that the surface effectively available for the contact between the electrolyte and the electrode layer and the flow paths through the cavities are considerably enlarged. The artificially created pore-shaped cavities improve the accessibility of the electrolyte to the interior of the electrode layer. This accessibility is based on a tortuosity close to 1 paired with a corresponding diameter. Compared to the already existing relatively narrow gaps, the invention creates additional, relatively wide channels for the electrolyte. As a result, the electrolyte can better penetrate the electrode layer with the aid of the structure provided. Both the improved penetration and the increased surface area contribute to the fact that the storage capacity and / or the C-rate of the battery cell designed in this way is considerably improved without impairing its geometric dimensions and weight. In particular, the storage capacity can be made available at increased C rates of> 1C, which, for example, can shorten the charging time required for rapid charging of battery cells in vehicles. The C-rate is, for example, the quotient of the maximum charging current and the capacity of the battery cell or battery. The higher this value, the shorter the time required to charge the battery.

In particular, it can be provided that the structure depth is between 50% and 100% of the electrode layer thickness. It has been shown here that the effects described above can be intensified with increasing structure depth. Particularly clear effects can be achieved if the structure depth is at least half the electrode layer thickness. In this way, depending on the application, the storage capacity and / or the C-rate of the battery cell can be increased significantly.

In particular, it can be provided that the cavities of the structure have a lateral spacing which is in the range from 100% to 1000% of the electrode layer thickness. The cavities that are laterally spaced apart in this way achieve a significant increase in the storage capacity without significantly reducing the volume of the usable electrode layer. Rather, the usable volume of the electrode layer is available almost unchanged, but at the same time the mentioned advantages of increasing the storage capacity and increasing the energy density in the battery cells are achieved.

In particular, the cavities can be designed as cylindrical pores, with which particularly good results are achieved. However, elongated depressions are also conceivable which are arranged in a manner similar to furrows and whose width corresponds approximately to the diameter of the pore in the longitudinal and / or lateral direction.

Similar to a line with the same diameter, which in the case of x and y structuring through the nodes results in a checkerboard pattern.

It is also very particularly advantageous if the cavities in the electrode layer are generated by means of an electrode beam. Because of the extremely small geometrical dimensions, such a structure can be produced, for example, by means of laser radiation. In this way, the aforementioned technical advantages can already be achieved in that the cavities are generated by the coherent light radiation in the electrode layer. However, the introduction of the cavities by means of an electron beam has proven to be even more advantageous from an economic point of view. The creation of cavities by means of the electron beam allows a significantly economical process control with increased production speeds at the same time. This is of considerable importance in particular with regard to the future requirements for the mass production of battery cells.

In particular, provision can also be made for the cavities to have a diameter or a width of less than 50 μm (micrometers), preferably of less than 40 μm and in particular of less than 10 μm.

Even the very small diameter of the cavities is sufficient to achieve the positive effects on the storage capacity of the electrode layer and thus the battery cells. The selected dimensioning of the diameter is chosen so that it is large enough to ensure that the electrolyte can more easily penetrate into deeper regions of the electrode layer and penetrate them. This allows for easier wetting with the electrolyte even if the electrode layer is thicker, which enables higher energy densities with simultaneous high current capability in the battery cell.

In particular, a motor vehicle can be equipped with at least one battery cell that is equipped with electrodes, the electrode layers of which have the structured surfaces described above. Such a vehicle benefits from the improved storage capacity and thus the improved range. A further improvement is also achieved through the better high-current capability in terms of power consumption or power output. The higher currents allow shortened charging times on the one hand and the provision of larger currents for energy output on the other.

1. a) Auftragen einer Elektrodenschicht auf eine Trägerschicht zur Herstellung einer Elektrodenlage;
2. b) Bestrahlen der Elektrodenschicht der Elektrodenlage mit einem Elektronenstrahl zur Erzeugung von Kavitäten.

Furthermore, a method for producing an electrode layer for a battery cell is specified, which has the following steps:

1. a) applying an electrode layer to a carrier layer for producing an electrode layer;
2. b) irradiating the electrode layer of the electrode layer with an electron beam to generate cavities.

This method can be implemented cost-effectively in the context of the mass production of battery cells or batteries. In particular, the use of electron beams to create the cavities has the advantage that the structuring of the surface and thus also of the coating can take place with very short cycle times or throughput times. Depending on requirements, production can either take place in cycles or in a continuous process.

A further development of the method for producing an electrode film for a battery cell is also advantageous if the carrier layer is irradiated with an electron beam in order to produce cavities. In this case, only the carrier layer can be irradiated either alone or in combination with the electrode layer. By also providing the carrier layer with cavities, the penetration of the electron path through the electrolyte can be further improved.

The cavities thus cause an increase in the penetration speed (soaking speed) with which the electrolyte penetrates the coating and an improved electrolyte distribution. Furthermore, the cavities also ensure better adhesion of the electrode layer on the substrate of the carrier layer. The storage capacity and energy density of the battery cells can also be positively influenced by this measure, i.e. H. will ultimately be enlarged.

In addition, the method for producing the electrode film can advantageously be carried out in such a way that the electrode layers are blasted by means of the electron beam under a vacuum or under a reduced atmosphere. The fact that irradiation under vacuum requires a little more effort to generate the vacuum, but has the advantage that a micrometer-accurate structure with any pattern can be represented in the surface of the electrode layer, since the emitted electrons in the vacuum are not caused by other masses, molecules or atoms be scattered.

If, on the other hand, the present method is carried out under a reduced atmosphere or a lower atmosphere, i. H. with a reduced air pressure, there is a stochastic distribution of the electron impact locations on the surface of the electrode layer or the electrode layer or the carrier layer. Carrying out the method under a lower atmosphere, i.e. under a lower atmospheric pressure, is advantageous if, for example, a stochastic distribution of the electron impact locations is desired and already sufficient. In this case, a lower atmosphere is sufficient and only a reduced effort is required to generate it.

Alternatively, the method can also be carried out under the atmosphere at ambient pressure. However, due to the physical scattering effects, there is a greater scattering of the electron impact locations.

The explanations on the battery cell can also be used to characterize the method. In particular, the method proposed here can be used to generate the structure with the cavities, so that the explanations relating to the cavities or the structure are also an aid for the person skilled in the art to set the method correctly.

The electron beam can be used to generate the structure on the surface of the electrode film or layer, the cavities generated there extending from the surface into the depth and improving the penetration of electrolyte there.

The structuring can take place under vacuum, reduced atmosphere or under atmosphere. A very precise surface structure with any structure pattern can be achieved under vacuum. Under the atmosphere, for example, can be influenced by the probability of impact Electrons or, under a low / reduced atmosphere, the surface can be adequately structured through a stochastic distribution of the electron impact locations.

The depth of the structure in the active material can be set to a maximum of the layer thickness and a minimum of 0.3 times the electrode layer thickness. The diameter of the structure or cavities can be set to a few micrometers. The lateral spacing of the structures or cavities can be set to 1 to 5 times, preferably 1 to 2 times, the thickness of the electrode layer. If a multi-layer structure of the electrode layer is used, the structure depth can be determined in relation to the then present total layer thickness of the multi-layer electrode layer.

The processing of the electrode layer surface can be done with a stationary (moving substrate) or unsteady electron beam.

The structure can be designed differently over the individual electrode layer, so that the density of the structures or the cavities can vary over the area.

The high, possible process speed enables structuring over the entire width of the electrode, for example, in that a meander-shaped tracing of the surface is carried out. It is (also) possible to move the electrode layer under the electron beam.

As a precaution, it should be noted that the numerals used here (“first”, “second”, ...) primarily (only) serve to distinguish between several similar objects, sizes or processes, so in particular no dependency and / or sequence of these objects, sizes or prescribe processes to each other. Should a dependency and / or sequence be required, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described embodiment.

• 1: eine seitliche Schnittansicht einer Elektrodenlage;
• 2: eine erste Methode zu Erzeugung von Kavitäten;
• 3: eine zweite Methode zu Erzeugung von Kavitäten;
• 4: eine dritte Methode zu Erzeugung von Kavitäten; und
• 5: ein Kraftfahrzeug mit Batteriezellen.

The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be pointed out that the invention is not intended to be restricted by the exemplary embodiments cited. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description. In particular, it should be pointed out that the figures and in particular the size relationships shown are only schematic. Show it:

• 1 : a side sectional view of an electrode sheet;
• 2 : a first method of creating cavities;
• 3 : a second method of creating cavities;
• 4th : a third method of creating cavities; and
• 5 : a motor vehicle with battery cells.

In 1 is a possible embodiment of an electrode layer 1 shown in a side sectional view. The electrode position 1 is constructed in three layers in this embodiment. The top layer is a first electrode layer 2 . A carrier layer follows underneath 3 . On the underside of the carrier layer 3 is a second electrode layer 4th arranged. All three layers are permanently connected to one another to form an electrode layer. The electrode position 1 is in a continuous manufacturing process, preferably at a uniform speed in the direction of an arrow 5 emotional. Above the electrode layer 1 is an electron source 6th arranged, which the schematically shown electrons 7th in the direction of the electron orbit 1 can emit. The emitted electrons 7th are so rich in energy that they are suitable when they hit the first electrode layer 2 Cavities 8th to create. The cavities 8th extend from a surface 9 the first electrode layer 2 down towards the backing layer 3 . The distance from the surface 9 up to a reason 10 the cavity 8th defines a structure depth 10 . The cavities 8th show a lateral distance 11 on, which is about one layer thickness 12th the first electrode layer 2 is equivalent to. The layer thickness 12th is the distance between the carrier layer 3 and the surface 9 the first electrode layer 2 . The intensity and distribution of the electron source 6th emitted electrons 7th is chosen so that the cavities 8th a diameter 13th have which is smaller than 40 microns and in particular smaller than 10 microns. The production of the structured electrode layer 1 can in a manufacturing fixture 14th which enables compact, reliable and mass production. In particular, the manufacturing device 14th can also be designed as a closed system, which includes an integrated negative pressure chamber for generating a vacuum or a low atmosphere.

In 2 is an electrode sheet according to the invention 1 shown in a top view. During the manufacturing process, the electrode layer 1 in the direction of the arrow 5 promoted. The promotion can be carried out continuously or discontinuously, ie at a constant speed or in steps. In the embodiment shown here, a large number of cavities 8th with a stochastic distribution in the electrode layer 1 brought in. The electrode layer is used for this 1 at the position shown under the electron source 6th stopped. At the same time, the electrode source 6th alternately in the direction of the arrow 15th on both sides towards the edges 16 the electrode position 1 proceed to the point of impact of the emitted electrons 7th following a stochastic distribution on the surface 9 the electrode position 1 to distribute. When the electrons hit 7th on the surface 9 then become the cavities 8th generated.

In 3 an embodiment is shown in which the electron source 6th is operated stationary. I. E. different from the one shown previously 2 becomes the electron source in this embodiment 6th do not proceed. Instead it is the electron source 6th designed so that they get the electrons 7th only in the area of an approximately rectangular electron band 17th emitted. That means it sends electrons 7th in an area within this electron band 17th off that extends from the left edge 16 to the right edge 16 the electrode position 1 extends and in the direction of the arrow 5 seen has a defined width shown in the figure. With this electron source 6th who have favourited the electrons 7th The production of the electrode layer can be emitted “like a slot” 1 with a continuously emitting electron source with a continuous conveyance in the direction of the arrow 5 respectively. Alternatively, the electrode layer 1 also step by step by the width of the electron band 17th proceed and then be stopped again in order to activate the electron source in the stopped state 6th activate temporarily before the electron orbit 1 repeat the procedure and run through this cycle again.

the 4th shows a third possible embodiment of the present invention. There are four states during the introduction of cavities 8th into the electrode layer 1 shown. In the first step shown at the top left is the electron source 6th activated and electrons become 7th in the direction of the electrode position 1 emitted. At the top right the chronologically next state is shown in which the electron source 6th already partly to the left towards the left edge 16 has been proceeded. Behind the electron source as seen in the direction of travel 6th due to the electrons hitting there 7th already cavities 8th educated. The electron source 6th is guided following a meandering movement. The meandering movement is marked with the appropriate arrows. In the third state shown below on the left, the electron source has 6th the left margin 16 reached, whereupon a reversal of movement takes place and the electron source 16 now towards the right edge 16 is returned. During the reversing movement, the electrode position is 1 in the direction of the arrow 5 moved further, so that now the overlying area with cavities 8th is provided. This is in the fourth state at the bottom right in 4th shown.

Finally shows 5 a motor vehicle 18th with a battery 19th that come with a variety of battery cells 20th is equipped according to the present invention. The motor vehicle designed in this way 18th has due to the increased battery capacity and high current capability of the battery 19th about an improved range and power output or power consumption. The increased battery capacity is in turn due to the improved battery cells designed according to the invention 20th achieved. A wrap 21 protects the respective battery cell 20th with the components arranged therein and seals them off tightly from the environment. In this way, it is prevented, for example, that the battery cell 20th The electrolyte contained in it leaks or dries out, and foreign substances such as dirt and moisture enter the battery cell. However, the invention can also be used with other non-liquid electrolytes and achieve the advantages mentioned. The one from the battery 19th Provided energy can by means of a control 22nd needs-based, on a larger scale and over a very long period of time to an electric motor 23 be delivered by the motor vehicle 18th drives. In addition, the improved battery 19th can be loaded in a shorter time.

List of reference symbols

1

Electrode position

2

first electrode layer

3

Carrier layer

4th

second electrode layer

5

arrow

6th

Electron source

7th

electron

8th

cavity

9

surface

10

Structure depth

11

lateral distance

12th

Electrode layer thickness

13th

diameter

14th

Manufacturing device

15th

arrow

16

edge

17th

Electron band

18th

Motor vehicle

19th

battery

20th

Battery cells

21

Wrapping

22nd

steering

23

Electric motor

Claims (9)

Battery cell (20), in particular a Li-ion cell, with at least two electrodes as well as separators arranged between the electrodes and an electrolyte, the electrodes each having at least one conductor and a plurality of electrode layers (1), as well as a casing (21) , which tightly encloses the components of the battery cell (20), characterized in that the electrode layer (1) has an at least two-layer structure with a carrier layer (3) and at least one electrode layer (2) arranged thereon, with one surface (9) of the electrode layer (1) a structure with cavities (8) is provided which have a predetermined structure depth (10) of more than 30% of an electrode layer thickness (12). Battery cell (17) according to the preceding claim, characterized in that the structure depth (10) is between 50% and 100% of the electrode layer thickness (12). Battery cell (17) according to one of the preceding claims, characterized in that a lateral distance (11) between the cavities (8) is between 100% and 1000% of the electrode layer thickness (12). Battery cell (17) according to one of the preceding claims, characterized in that the cavities (8) are generated by means of an electron beam. Battery cell (17) according to one of the preceding claims, characterized in that the cavities (8) have a diameter (13) of less than 50 µm, preferably less than 40 µm and in particular less than 10 µm. Motor vehicle (13) with at least one battery cell (17) according to one of the preceding claims. Method for producing an electrode layer (1) for a battery cell (17), comprising the following steps: a) applying an electrode layer (2) to a carrier layer (3) for producing an electrode layer (1); b) irradiating the electrode layer (2) of the electrode layer (1) with an electron beam to generate cavities (8). Method for producing an electrode layer (1) for a battery cell (20) according to the preceding claim, characterized in that the carrier layer (3) is irradiated with an electron beam in order to produce cavities (8). Method for producing an electrode layer (1) for a battery cell (20) according to the preceding claim, characterized in that the irradiation takes place under vacuum or a reduced atmosphere.

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