EP2745335A1

EP2745335A1 - Energy storage device

Info

Publication number: EP2745335A1
Application number: EP12747980.6A
Authority: EP
Inventors: Tim Schaefer
Original assignee: Li Tec Battery GmbH
Current assignee: Li Tec Battery GmbH
Priority date: 2011-08-17
Filing date: 2012-08-10
Publication date: 2014-06-25
Also published as: WO2013023773A1; DE102011110703A1

Abstract

The invention relates to an energy storage device comprising at least one energy storage cell having an electrode stack (2) or an electrode winding. In order to ensure an enhanced functional reliability while keeping the structure simple, at least one outer functional layer (10) is provided on at least one outer wall of the energy storage cell, in particular the electrode stack (2) or electrode winding, said outer functional layer comprising a carrier layer that is at least partially permeable to substances.

Description

Energy storage device

Description

The present invention relates to an energy storage device according to the preamble of claim 1. Herewith, the entire contents of the priority application DE 10 2011 1 10 703.0 by reference is part of the present application.

Energy storage devices known from the prior art have at least one electrochemical energy storage cell, which is also referred to as an electrochemical cell or galvanic cell, in the form of an electrode stack or electrode coil, which is generally surrounded by a housing. The electrode stack usually comprises a plurality of two electrodes in each case and an intervening separator layer which can receive an electrolyte, composite electrode groups which are arranged or stacked next to one another or one above the other. In an electrode winding at least one electrode group is wound into a so-called. Winding. The electrodes of the electrode groups of the same polarity are each electrically connected to a current conductor, via which the electrical voltage generated in the cell can be tapped from the outside.

In the case of energy storage devices known from the prior art, it is not always possible to ensure a high level of functional reliability with a simultaneously simple design. It is an object of the present invention to provide an energy storage device which has an increased reliability with a simple structure.

This object is achieved by an energy storage device according to claim 1.

The energy storage device according to the invention is characterized in that on at least one outer wall of the energy storage cell, in particular on at least one outer wall of the electrode stack or electrode coil, an outer functional layer is provided which has an at least partially permeable support layer.

The invention is based on the idea of at least partially surrounding the electrode stack or electrode winding with an at least partially permeable functional layer which, in particular, excess electrolyte liquid, which can escape from the separator layers located between the anode and cathode layers of the stacking or winding layers, at least temporarily can absorb or bind. Damming excess quantities of electrolyte in the usually located in a liquid-tight container electrode stack or -wickel can be prevented in a simple manner, since there is additional space for receiving electrolyte liquid in the located between the electrode stack or -wickel and the container wall functional layer. A leakage of electrolyte liquid from the cell can be prevented in a simple manner. The functionality and security of the energy storage device is thereby significantly increased. In addition, the outer functional layer allows a mechanical fixation of the stack layers of the electrode stack or of the electrode winding, so that an additional fixation of the stack layers or of the wound winding layers is possible. layer, for example by gluing or laminating, can be omitted. In addition, the outer functional layer improves the resistance of the cell to mechanical stress, for example due to vibrations, and thermal stress, for example due to temperature increases occurring during charging or discharging, which has an overall life-prolonging effect.

Furthermore, the functional layer can serve as a supply for conducting salt, which can be taken up in the functional layer and, if necessary, can be dispensed to the electrolyte liquid in which conducting salt is dissolved in a solvent. In this way, the conductive salt concentration in the electrolyte, in particular in the separator layers, can be maintained at the required level. Alternatively or additionally, the functional layer can also serve as a reservoir for radical scavengers, which are preferably added to the electrolyte liquid and are taken up together with the functional layer. Radical scavengers prevent the release of free radicals at high temperatures in the cell, which can cause an explosion of the cell.

Overall, the invention provides increased reliability with a simplified design and ease of manufacture.

A functional layer in the sense of the invention here is a layer of a so-called functional material. Functional materials are materials whose structure and / or properties are purposefully chosen for a particular application. In the present invention, the functional layer is characterized, inter alia, by the fact that it is at least partially permeable to the material and therefore can absorb, inter alia, electrolyte fluid. For the purposes of the invention, an energy storage device is understood as meaning a device which is capable of generating, in particular, electrical energy. take, store and dispense, in particular taking advantage of electrochemical processes.

As an energy storage cell is understood within the meaning of the invention, a self-contained functional unit of the energy storage device, which in itself is also able to absorb electrical energy, store and release again, in particular by utilizing electrochemical processes. An energy storage device according to the invention may comprise an energy storage cell or a plurality of energy storage cells.

An energy storage cell can, for example, but not only, a galvanic primary or secondary cell (in the context of this application, primary or secondary cells indiscriminately referred to as battery cells and an energy storage device constructed therefrom as a battery or battery assembly), a fuel cell, a high power capacitor or an energy storage cell be different kind. In particular, in this context, an energy storage cell is to be understood as meaning an electrochemical energy storage cell which stores energy in chemical form, delivers it in electrical form to a consumer and preferably can also receive it in electrical form from a charging device. Important examples of such electrochemical energy stores are galvanic cells and fuel cells. The electrolyte of the energy storage cell preferably contains lithium ions. A container usually surrounding the cell is a device which is suitable for preventing the escape of chemicals from the electrode stack into the environment and for protecting the components of the electrode stack from damaging external influences. The container may be formed from one or more moldings and / or film-like. Further, the container may be single-layered or multi-layered. The container is preferably formed from a gas-tight and electrically insulating material or layer composite. Preferably, the at least partially permeable carrier layer is coated on at least one side with an inorganic material. As a result, a high thermal and chemical stability of the functional layer and consequently a high level of functional reliability of the energy storage device, in particular during temperature increases occurring during charging or discharging, can be achieved.

It is preferred that the inorganic material, in particular in a temperature range between - 40 ° C and + 200 ° C, ion conducting. In this way, the functional layer is particularly well suited in a wide temperature range for at least temporary absorption of electrolyte fluid.

It is also preferred that the inorganic material comprises at least one compound from the group of oxides, phosphates, sulfates, titanates, silicates, aluminosilicates with at least one of the elements Zr, Al, Li, in particular zirconium oxide. As a result, a high stability of the functionality of the cell, in particular over a wide temperature range is achieved.

Preferably, the inorganic material has particles with a largest diameter below 100 nm. Due to the nanoporosity of the functional layer thus achieved, their properties are particularly pronounced. In particular, in this case the absorption capacity and permeability for electrolyte fluid is particularly favorably influenced, which in turn has a positive effect on the functionality of the cell.

In a further preferred embodiment, the at least partially permeable carrier layer is made of an organic material, in particular a polymer, in particular polyethylene terephthalate (PET). This makes it possible to provide a carrier layer for the functional layer in a simple and cost-effective manner, which simplifies the manufacture and construction of the energy storage device as a whole. The at least partially permeable carrier layer is preferably configured as a fleece. This represents a particularly cost-effective variant of a suitable carrier layer. In principle, however, it is also possible to design the carrier layer as a tissue. In a particularly preferred embodiment, the functional layer is not or only slightly electron-conducting. This ensures that the functional layer, if no electrolyte liquid is absorbed therein, is reliably electrically insulating, so that no electrical currents can flow between a possibly metallic container of the cell and the cell itself. A further preferred embodiment of the invention provides that the at least one outer functional layer has the shape of a shell, in particular a half shell, which surrounds at least a part of the energy storage cell. As a result, a cladding or wrapping of the cell can be achieved in a particularly simple manner. By a suitable fastening of the two shells to one another and / or to a wall of the energy storage cell, the individual stack layers or the wound winding layer of the cell are held together by the two shells, so that an additional fixation, for example by laminating the stack layers or winding layer, can be omitted. It is also preferred to design the outer functional layer in such a way that it can be shrinked under the action of heat, and to surround at least a part of the energy storage cell by a shrunken outer functional layer. In this embodiment, the required for a sufficient fixation of the stacked layers or wound winding layer pressure on the stack or winding is generated by the shrinkage of the functional layer itself, without this would need to be additionally fixed with adhesive tapes or the like. As a result, construction and manufacture of the energy storage device are greatly simplified. In both preferred embodiments described above, the stack layers of the electrode stack or the winding of the electrode coil are held together in a simple manner with the aid of the outer functional layer, which represents a further special advantage of the outer functional layer in addition to the capacity for absorbing electrolyte liquid.

Preferably, the energy storage device has a container which is designed to receive the energy storage cell and, in particular, can be closed by a cover after the introduction of the electrode stack or coil. Preferably, the container has the form of a hollow body open on one side, which is in particular cuboid or cuboid with two outwardly curved end faces. Preferably, the hollow body is obtained by extrusion, in particular by cold extrusion, or deep drawing of a metal sheet blank. In this way, a mechanically and chemically stable enclosure of the cell can be realized simply and inexpensively, by means of which heat arising in the cell can be efficiently dissipated to the outside.

In addition to the fixation of the electrode stack or -wickel by means of the outer functional layer, the individual stack layers or winding layer may be at least partially connected to each other by lamination. In this case, the individual stacking layers are glued to each other at least in some areas by means of an adhesive. Preferably, the adhesive is a so-called. Hot melt adhesive, which is substantially solid at room temperature and only becomes liquid when heated and unfolds its adhesive effect. Accordingly, the stack layers are preferably glued together by pressing and / or rolling under the action of heat. By one or more of these measures, a particularly high mechanical stability of the electrode stack is achieved, wherein the stack layers are also thermally coupled to each other well, so that a derivative of heat generated in the cell in the direction of the container wall is favored. A battery arrangement has a plurality of energy storage devices according to the invention, on which contact elements are provided, which are electrically connected to each other, in particular in series and / or connected in parallel. In this way, the voltages or powers of the battery arrangement required for the respective application are realized.

The energy storage device or the battery arrangement according to the invention is advantageously used for supplying an electric drive or hybrid drive of a motor vehicle with electrical energy.

Further advantages, features and applications of the present invention will become apparent from the following description taken in conjunction with the figures. Show it:

1 shows an example of the construction of an energy storage device;

2 shows a section of an example of the structure of an electrode stack with inner functional layers;

3 shows a detail of an example of a winding layer of an electrode winding and a reduced, schematic representation of a winding layer wound around a winding core;

4 shows a cross section through an electrode stack with functional layers;

5 shows a cross section through an electrode winding with functional layers;

6 shows an example of a shell-shaped outer functional layer on an electrode stack; 7 shows a further example of an outer functional layer on an electrode stack; and

8 shows an example of a shell-shaped outer functional layer on an electrode winding. Figure 1 shows an example of the structure of an energy storage device having a substantially cuboid container 1, which is preferably formed of metal and is open to a narrow side. The container 1 can be produced, for example, by extrusion, in particular cold extrusion, or deep-drawing of a corresponding starting workpiece, in particular a sheet. Through the open side of the container 1, an electrode stack 2 or an electrode coil (not shown) is inserted into the container 1.

The electrode layers of the electrode stack 2 or electrode winding of the same polarity, ie anode and cathode layers, are electrically contacted with contact strips 3 and 5, respectively. The contact lugs 3 and 5 are contacted by means of further contact elements 4 and 6 through an insulating element 7 with the cover 8 of the energy storage device or led out by means of further, not shown contact elements through an opening 9 in the lid 8 through from the energy storage device. Before being introduced into the container 1, the electrode stack 2 or electrode winding is provided with an outer functional layer 10 which surrounds it at the two broad and / or end sides and / or at the bottom side of the cuboid electrode stack 2 or parallelepipedal electrode winding. The outer functional layer 10 protrudes in the illustrated example on the sides over the height of the electrode stack 2 addition, but may also be only up to the height of the sides of the electrode stack 2 or lower, ie only cover a portion of the side regions of the electrode stack 2. The outer functional layer 10 is not or only slightly electron-conducting and has an at least partially permeable carrier. The support is preferably coated on at least one side with an inorganic material. An organic material which is preferably configured as a nonwoven web is preferably used as the carrier, which is at least partially permeable to material. The organic material, which preferably comprises a polymer and particularly preferably a polyethylene terephthalate (PET), is coated with an inorganic, preferably ion-conducting material, which is more preferably ion-conducting in a temperature range from -40 ° C to + 200 ° C. The inorganic material preferably comprises at least one compound from the group of oxides, phosphates, sulfates, titanates, silicates, aluminosilicates with at least one of the elements Zr, Al, Li, particularly preferably zirconium oxide. The inorganic, ion-conducting material preferably has particles with a largest diameter below 100 nm. Layers having such properties are sold, for example, under the trade name "Separion" by Evonik AG in Germany.

In the region of the center of the electrode stack 2, at least one inner functional layer 40 is provided, which preferably extends over an entire stack level of the electrode stack 2. With regard to the properties of the inner functional layer 40, the above statements on the outer functional layer 10 apply correspondingly. This means that preferably "separation" layers are also used for the inner functional layers 40.

The at least partially permeable outer functional layer 10, which at least partially surrounds the electrode stack 2 or electrode winding, can at least temporarily take up or remove excess electrolyte fluid, which can escape from the separator layers located between the anode and cathode layers of the stacking or winding layers . tie. Damming of leaked electrolyte liquid in the liquid-tight container 1 can thereby be prevented in a simple manner, since in the between the electrode stack 2 or -wickel and the container wall located outer and Ren functional layer 10 in addition space for receiving electrolyte fluid is present. An escape of electrolyte liquid from the energy storage device can be prevented in a simple manner. The functionality and security of the energy storage device is thereby significantly increased.

The at least partially permeable inner additional layers 40 provided in the interior of an electrode stack 2 or electrode winding can also absorb or bind, at least temporarily, in particular, excess electrolyte fluid which can escape from the separator layers located between the anode and cathode layers of the stacking or winding layers. Damming excess quantities of electrolyte in the electrode stack 2 or electrode winding, which is usually located in a liquid-tight container 1, can thereby be prevented in a simple manner since there is additionally space for receiving electrolyte fluid in the functional layers 40 located in the interior of the electrode stack 2 or coil is. A leakage of electrolyte liquid from the cell can be prevented in a simple manner. The functionality and reliability of the energy storage device is thereby significantly increased. The at least partially permeable inner functional layer 40 also improves the resistance of the cell to mechanical stress, eg due to vibrations, and thermal stress, for example due to temperature increases occurring during charging or discharging, which has an overall life-prolonging effect. This is facilitated in particular by the fact that the inner functional layers 40 additionally present in the interior have a certain elasticity, by means of which an expansion space is created in the center of the stack 2 or in the winding core of the coil, by means of which an expansion or shrinkage of the stack 2 or Wickels can be compensated within certain limits, without the stack 2 or winding itself and / or the container 1 would be stressed too much. Figure 2 shows a section of an example of the structure of an electrode stack 2 of a plurality, in particular of a plurality of juxtaposed or stacked stack layers 20, each of which an anode layer 21, a cathode layer 22, an interposed therebetween Separatorschicht 23 Include an electrolyte and a provided on the anode layer 21 and / or cathode layer 22 insulating layer 24. In the region of the center of the electrode stack 2, a plurality of-in this case three-inner functional layers 40 are provided, which are enclosed by two stack layers 20. The inner functional layers 40 are in the example shown between about the same number of stack layers 20 on both sides. Alternatively, the inner functional layers 40 can also be offset to one side of the electrode stack 2, ie arranged eccentrically.

FIG. 3 shows a section (left-hand part of the FIGURE) of an example of a winding layer 30 of an electrode winding 12 'and a reduced schematic representation (right-hand part) of a winding layer 30 wound around a winding core 40. The winding layer 30 comprises an anode layer 31, a cathode layer 32, a separator layer 33 located therebetween for receiving an electrolyte, and an insulation layer 34 provided on the anode layer 31 and / or cathode layer 32.

In the so-called circular wraps 12 'shown schematically in the right-hand part of FIG. 3, the winding layer 30 was wound around a substantially round winding core 13, which is formed by one or more inner functional layers 40. After winding, the round wrap 12 'is brought into an approximately parallelepiped or prismatic shape, for example, by compression in the direction of the arrows shown in the figure, a so-called flat wrap 12 (see FIG cuboid container 1 fits. Preferably both the outer functional layer 10 provided on the outer walls of the electrode stack 2 or the electrode coil and the inner functional layers 40 provided within the electrode stack 2 or electrode coil are layers of "separation." In addition, separator layers 23 can be used , 33 and / or as insulating layers 24, 34 in the electrode stack 2 or in the electrode winding also advantageously "separation" layers are used.

FIG. 4 shows a cross section through an electrode stack 2, which is enclosed by an outer functional layer 10. The outer functional layer 10 is configured in this example as a so-called shrink layer, which can contract under the action of heat. In the production of the electrode stack 2, the stacked stacked layers 20, in the middle of which optionally at least one inner functional layer 40 is located, are provided and encased in the not yet shrunken outer functional layer 10. Subsequently, the sheath is heated, for example by irradiation with infrared radiation or by hot air, so that it contracts and tightly encloses the stack formed from the stack layers 20. The individual stacking layers 20 and the optionally additionally provided inner functional layer 40 are hereby fixed in a simple and fast manner to form a stable stack, without requiring an additional fixation of the individual stacking layers 20 or the inner functional layer 40, which makes the production of the electrode stack 2 significantly simplified.

FIG. 5 shows a cross section through a flat electrode winding 12 in which a winding layer 30 is wound around a winding core 13 several times. In the winding core 13, at least one inner functional layer 40 is provided. The outer region of the electrode coil 12 is surrounded by an outer functional layer 10. The production of such a so-called flat winding 12 can be effected, for example, by winding the winding layer 30 around an initially substantially circular winding core. is wrapped (see Figure 3). A plurality of layers, in particular a plurality of winding layers, of the inner functional layer 40 are preferably contained in the circular winding core. This so-called round wrap is then compressed so that a flat wrap having substantially parallel side walls, as shown in FIG. 5, is obtained. The flat coil 12 is then - as already explained in connection with Figure 4 - preferably surrounded with a shrinkable outer functional layer 10 and finally held after shrinkage of the outer functional layer 10 in the desired shape. According to the fixation of the stack layers 20 in the example shown in FIG. 4, the shrinkage of the electrode coil 12 also achieves a fixation of the individual winding layers 30 including the inner functional layers 40 located in the winding core 13, even in the example shown in FIG Fixing of the individual winding layers 30 and / or the inner functional layers 40, for example by lamination, can be dispensed with.

Additionally or alternatively to the fixation by means of the outer functional layer 10, it is possible to connect the individual stack layers 20 of the electrode stack 2 or the winding layer 30 of the electrode coil 12 at least in the region of part of their contact surface, preferably by means of an adhesive. It is preferred to choose an adhesive which is solid at room temperature and melts only by heating and unfolds its adhesive effect. In this case, the stacked layers 20 or winding layer 30 provided with a corresponding adhesive are joined to one another by a so-called hot lamination, for example by pressing and / or rolling them under the action of heat. By the described, at least partially, connection of the individual stacking layers 20 or winding layer 30, a particularly high mechanical stability of the stack 2 or coil 12, in particular in the event of damage to the container 1 from the outside, is achieved. In the examples shown in FIGS. 4 and 5, the outer functional layer 10 is configured in each case as a shrink layer. Alternatively, however, the outer functional layers 10 can also be attached in another way in the region of the outer walls of the electrode stack 2 or of the electrode winding 12. This will be explained in more detail with reference to the embodiments shown in Figures 6 to 8.

In the example shown in FIG. 6, the substantially cuboid electrode stack 2 is enclosed by two shell-like outer functional layers 10a and 10b. Due to the half-shell shape of the two outer functional layers 10a and 10b, these cover each one side surface of the electrode stack 2 completely and the front and rear end surface and the bottom surface of the electrode stack 2 in each case half. The two shell-shaped outer functional layers 10a and 10b are preferably dimensioned so that their front and bottom edges are in each case in abutment when the shells 10a and 10b enclose the electrode stack 2. In the region of the abutting edges, the two shells 10a and 10b are fixed by a suitable fixing means, for example a circulating adhesive tape 11.

In the example shown in FIG. 7, the outer functional layer 10 initially has the shape of a substantially triangular arc on which the electrode stack 2 with its bottom surface is centrally placed. In the region of the respective end face of the electrode stack 2, cutouts 15 and 16 are provided in the arcuate outer additional layer 10. The two wings of the arcuate functional layer 10 are then folded up and come to lie on the respective side surfaces of the electrode stack 2. The protruding in the region of the respective end portions 17 and 18 of the functional layer 10 are each folded to the front side of the stack 2 out and - according to the example shown in Figure 6 - fixed by means of a suitable fixative, in particular an adhesive tape. In the example shown in FIG. 8, an electrode winding 12 in the form of a flat coil is likewise surrounded by two shell-shaped outer functional layers 10a and 10b. The statements in connection with the example shown in Figure 6 apply accordingly.

Claims

P a n t a n s p r e c h e

Energy storage device with

at least one energy storage cell with an electrode stack (2) or electrode winding (12), characterized in that on at least one outer wall of the energy storage cell, in particular of the electrode stack (2) or electrode coil (12), an outer functional layer (10, 10a, 10b) is provided is, which has an at least partially permeable carrier layer.

2. Energy storage device according to claim 1, wherein the at least partially permeable carrier layer is coated on at least one side with an inorganic material.

Energy storage device according to claim 2, wherein the inorganic material, in particular in a temperature range between minus 40 ° C and plus 200 ° C, ion conducting.

Energy storage device according to claim 2 or 3, wherein the inorganic material comprises at least one compound selected from the group of oxides, phosphates, sulfates, titanates, silicates, aluminosilicates at least one of the elements Zr, Al, Li, in particular zirconium oxide.

5. Energy storage device according to one of claims 2 to 4, wherein the inorganic material has particles with a largest diameter below 100 nm.

6. Energy storage device according to one of the preceding claims, wherein the at least partially permeable carrier layer of an organic material, in particular a polymer, in particular polyethylene terephthalate (PET), is prepared. 7. Energy storage device according to one of the preceding claims, wherein the at least partially permeable carrier layer is configured as a nonwoven.

Energy storage device according to one of the preceding claims, wherein the outer functional layer (10, 10a, 10b) is not or only slightly electron-conducting.

9. Energy storage device according to one of the preceding claims, wherein the at least one outer functional layer (10, 10a, 10b) has the shape of a shell (10a, 10b), in particular a half-shell, which surrounds at least a part of the energy storage cell.

Energy storage device according to one of the preceding claims, wherein the outer functional layer (10) is designed such that it is shrinkable under heat, and wherein at least a part of the energy storage cell is surrounded by a shrunken outer functional layer (10). 1 1. Energy storage device according to one of claims 9 or 10, wherein the stack layers (20) of the electrode stack (2) or the winding of the electrode coil (12) by means of the outer functional layer (10, 10 a, 10 b) are held together or.

12. Energy storage device according to one of the preceding claims with a container (1) for receiving the energy storage cell.

13. Energy storage device according to claim 12, wherein the container (1) has a hollow body open on one side, which is in particular cuboid or cuboid formed with two outwardly curved end faces.

14. Battery arrangement with a plurality of energy storage devices according to one of the preceding claims, wherein provided on the energy storage devices contact elements (4, 6) are electrically connected to each other.

15. Use of the energy storage device according to one of claims 1 to 13 or the battery arrangement according to claim 14 for supplying an electric drive or hybrid drive of a motor vehicle with electrical energy.