Battery cell and method for producing such a battery cell

Abstract

Battery cell (10) with a cell housing (12), a cell stack (30) and a guide element (46) arranged or formed in the cell housing (12) and / or on the cell stack (30) to facilitate the introduction of the cell stack (30) into the cell housing (12), characterized in that the guide element (46) is formed from a porous material with a storage capacity for electrolyte (38) for supplying the cell stack (30).

Description

[0001] The invention relates to a battery cell and a method for producing such a battery cell according to the preamble of the independent patent claims.

[0002] Battery cells require an electrolyte to facilitate the electrochemical reactions during charging and discharging, which enables the transport of ions within the battery cell. A typical lithium-ion battery cell has a pore structure saturated with a liquid electrolyte within the active material coatings of the anode and cathode, as well as within the separator. To ensure the battery cell's functionality, this pore structure must remain filled with electrolyte throughout the battery cell's entire service life to ensure that sufficient electrolyte is always available for optimal operation. Aging processes within the cell, such as undesirable side reactions that occur parallel to the desired charge-discharge reactions, consume electrolyte over the course of its operating life.If this causes the electrodes and / or the separator to dry out, ion transport can no longer take place, which causes the cell's internal resistance to rise sharply and practically no electrical energy can be extracted from the cell.

[0003] These processes can cause the cell's functionality to be completely lost within a very short period of time, a condition known as "sudden death" of the battery cell. To compensate for this and achieve a service life appropriate to the application, more electrolyte is typically added to the cell during production than the pore structure of the electrodes and separator can accommodate.

[0004] Thus, a certain amount of excess electrolyte accumulates within the remaining free spaces in the battery cell, which serves as a reserve for the amount of electrolyte consumed through aging. It is important to ensure that the excess electrolyte remains in contact with the electrode winding or electrode stack throughout the entire operating period, so that new electrolyte can be continuously transported into the pore structure, particularly through diffusion and capillary effects.

[0005] In hard-case battery cells with prismatic and cylindrical designs, this excess electrolyte tends to accumulate due to gravity in a gap between the electrode coil or electrode stack and the cell housing base. If, at some point during operation, so much electrolyte is consumed that the excess electrolyte level no longer completely fills this gap or no longer reaches the electrode coil or electrode stack, the remaining excess electrolyte can no longer be pumped into the electrode stack and used for the battery cell.

[0006] Prior art solutions include filling the battery cell with more excess electrolyte than is actually required for its intended service life. This ensures that the gap between the electrode winding or electrode stack and the housing remains completely filled with electrolyte even at the end of the battery cell’s planned service life. However, this results in increased electrolyte requirements and, associated with this, increased energy consumption during battery cell production, as well as resulting increased costs. Prior art solutions also include at least partially closing the gap between the housing and the electrode winding or electrode stack by inserting plastic parts. These plastic parts are typically provided with holes and / or bores to allow the electrolyte to pass through them.

[0007] WO 99 / 03164 A1 discloses an electrochemical accumulator comprising a generally cylindrical or prismatic chamber containing liquid electrolyte and an electrochemical assembly comprising at least one positive electrode, a separator, and a negative electrode, alternating between them. The accumulator comprises a housing and a porous material in the form of a porous washer, which is placed on the bottom of the housing before filling the accumulator with electrolyte and serves as an electrolyte reservoir. The porous washer is resistant to the electrolyte, no less hydrophilic than the separator, and incompressible.

[0008] From DE 10 2019 111 941 A1, a mixing device is known which is designed for installation in an electrochemical accumulator operated with liquid electrolyte in order to at least assist mixing of the electrolyte by means of capillary action, wherein the mixing device has a plurality of capillary connection paths which are designed to connect a head region of the accumulator to a bottom region of the accumulator.

[0009] The invention is based on the object of simplifying the production and assembly of a battery cell and reducing the amount of electrolyte required for the long-term safe operation of the battery cell.

[0010] This object is achieved by a battery cell comprising a cell housing, a cell stack, and a guide element arranged or formed in the cell housing and / or on the cell stack to facilitate the insertion of the cell stack into the cell housing. According to the invention, the guide element is formed from a porous material with a storage capacity for electrolyte to supply the cell stack.

[0011] A porous guide element can be used to create an additional reservoir for electrolyte in a gap between the cell casing and the cell stack of the battery cell, from which electrolyte can be replenished to the cell stack if electrolyte is consumed by an undesirable side reaction in the battery cell. This ensures that sufficient ion transport is always guaranteed in the battery cell. This prevents the battery cell from drying out and the associated increase in the cell's internal resistance as well as a significant reduction in electrical performance. Guide elements for inserting a cell stack into a cell casing of a battery cell are already known from the prior art. However, the known guide elements are not suitable for holding electrolyte, but serve merely as an assembly aid to prevent damage to the cell stack.In a battery cell according to the invention, such a guide element is modified in such a way that no additional components are required. This allows the manufacturing and assembly costs for the battery cell to be kept low, and the modification also creates a reservoir for reserve electrolyte to improve the supply of electrolyte to the cell stack and ensure a longer-term supply of electrolyte to the cell stack with the same amount of electrolyte compared to known battery cells.

[0012] The additional features listed in the dependent claims enable advantageous improvements and further developments of the battery cell specified in the independent claim.

[0013] In a preferred embodiment of the invention, the guide element is a guide rail that can be inserted into the cell housing or comprises a guide rail that can be inserted into the cell housing. A guide rail is a particularly simple and cost-effective guide element for facilitating the insertion of the cell stack into the cell housing. By means of a porous guide rail, which is preferably fastened to the cell stack or to the cell housing, the guide function can be easily combined with the electrolyte storage function. The guide rail is preferably attached to a geodetically viewed underside of the cell stack or a floor of the cell housing so that the porous structure fills by gravity when the electrolyte is added and the excess electrolyte collects in the guide rail during operation of the battery cell.

[0014] In a further preferred embodiment of the invention, the guide element is a guide sleeve that can be inserted into the cell housing or comprises a guide sleeve that can be inserted into the cell housing. A guide sleeve is provided that encloses the cell stack and closes a gap between the cell housing and the cell stack. This provides particularly good protection for the cell stack against mechanical damage during insertion into the cell housing. Furthermore, a guide sleeve enclosing the cell stack allows more electrolyte to be stored in the porous guide element, ensuring an even better supply and tracking of electrolyte into the cell stack.

[0015] In a further preferred embodiment of the invention, it is provided that the cell housing comprises a base, a first side wall preferably arranged perpendicular to the base and a top wall opposite the base and preferably arranged perpendicular to the first side wall, wherein the cell housing has an insertion opening for inserting the cell stack into the cell housing on a side opposite the first side wall.

[0016] It is preferred if a guide element for inserting the cell stack into the cell housing is arranged or formed at least on the bottom or on a side of the cell stack facing the bottom. The guide element can serve as a sliding element on which the cell stack rests during insertion into the cell housing. This allows for particularly easy insertion of the cell stack with minimal force, further reducing the risk of damage to the cell stack during battery cell assembly.

[0017] It is particularly preferred if a guide element of the cell stack is arranged or formed in the cell housing on both the floor and the ceiling wall, or on both the floor and the ceiling wall of the cell stack. Two guide elements, in particular two guide rails or a guide sleeve enclosing the cell stack, enable particularly simple assembly of the battery cell, since the guide elements ensure particularly good guidance and sufficient spacing between the cell stack and the cell housing.

[0018] The porous guide element can be connected to the cell stack in the battery cell by a positive, material, or force fit. A positive or material fit is preferred, as this creates a permanent connection that promotes the rising of the electrolyte.

[0019] In an advantageous embodiment of the battery cell, the cell housing comprises a cover with which the insertion opening can be closed after the cell stack has been inserted into the cell housing. The cover forms a second side wall opposite the first side wall. This enables particularly simple and cost-effective assembly of the battery cell. After assembly, the cover is preferably integrally bonded to the rest of the cell housing, thereby forming a fluid-tight cell housing that is stable over the service life of the battery cell and reliably prevents electrolyte leakage.

[0020] It is preferred if a first terminal for electrically contacting the cell stack is arranged or formed on the first side wall, and a second terminal for electrically contacting the cell stack is arranged or formed on the second side wall. This enables particularly simple and stable electrical contacting of the cell stack.

[0021] It is particularly preferred if the first terminal forms an anode of the battery cell and the second terminal forms a cathode of the battery cell. Alternatively, it is advantageously provided that the first terminal forms a cathode of the battery cell and the second terminal forms an anode of the battery cell.

[0022] In a preferred embodiment of the battery cell, it is provided that the cell stack has at least one anode layer and one cathode layer, wherein the anode layer and the cathode layer are electrically separated from one another by a separator.

[0023] In an advantageous further development of the battery cell, a ventilation element is arranged on the cell housing to regulate heat and pressure in the battery cell in the event of a battery cell failure. Since a large amount of gas must be removed from the battery cell within a short period of time in the event of a battery cell failure, the open-pore structure of the guide element can facilitate gas removal. In particular, channels formed in the porous guide element can guide the gas generated in the event of a battery cell failure out of the battery cell with low flow resistance.

[0024] According to an advantageous embodiment of the battery cell, the guide element is made of a porous plastic, with the porosity being designed such that the pores in the guide element convey the electrolyte into the cell stack by capillary action. Capillary action allows the electrolyte to rise from the bottom of the battery cell into the cell stack, thereby preventing at least partial drying out of the cell stack.

[0025] It is particularly preferred if the porous plastic is a sintered plastic, in particular a sintered thermoplastic, preferably a sintered thermoplastic from the group of polyolefins, particularly preferably sintered polypropylene.

[0026] Alternatively, the porous guide element can also be manufactured in another way, as long as an open-pore structure is created in the plastic and the pores are not closed by the manufacturing process. In particular, the guide element can also be produced by adding pore-forming substances during the manufacturing process or by foaming a plastic.

[0027] A further aspect of the invention relates to a method for producing such a battery cell, which comprises the following steps: - Providing a cell housing, - Inserting a porous guide element into the cell casing or fixing a porous guide element to a cell stack of the battery cell, - Inserting the cell stack into the cell housing or sliding the cell housing onto a cell stack, wherein the cell stack or the cell housing is guided by the porous guide element, and - Filling an electrolyte into the cell housing, whereby the cell stack and the porous guide element are impregnated with the electrolyte, whereby an electrolyte reserve quantity is stored in the porous guide element which exceeds the quantity of electrolyte necessary for the full function of the cell stack.

[0028] The proposed process makes it possible to produce a battery cell that provides sufficient additional electrolyte to ensure long-term battery cell function even in the event of electrolyte loss due to undesirable side reactions within the battery cell. The need for excess electrolyte can be reduced compared to existing battery cells, thereby saving energy and costs in battery cell production and reducing overall environmental impact.

[0029] In an advantageous embodiment of the method, it is provided that the cell housing comprises a base, a first side wall preferably arranged perpendicular to the base and a top wall opposite the base and preferably arranged perpendicular to the first side wall, wherein the cell housing has an insertion opening on a side opposite the first side wall, wherein the cell stack is pushed into the cell housing through the insertion opening.

[0030] Further preferred embodiments of the invention emerge from the remaining features mentioned in the subclaims.

[0031] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in the individual case.

[0032] The invention is explained below in exemplary embodiments with reference to the accompanying drawings. They show: Fig. 1 a preferred embodiment of a battery cell according to the invention, Fig. 2 shows a representation of the introduction of a cell stack into a cell housing of a battery cell according to the invention, and Fig. 3 a flow chart for the production of such a battery cell.

[0033] Fig. 1 shows a preferred embodiment of a battery cell 10 according to the invention. The battery cell 10 is preferably designed as a prismatic battery cell and comprises a cell housing 12, a cell stack 30, and at least one guide element 46 to facilitate the insertion of the cell stack 30 into the cell housing 12. The cell housing 12 comprises a base 14, which, in a geodetic view, forms a bottom side of the cell housing 12, on which the battery cell 10 rests during assembly and / or during operation. The cell housing 12 further comprises a first side wall 16 connected to the base 14 and preferably arranged perpendicular to the base 14, as well as a top wall 20, preferably parallel to the base 14 and arranged perpendicular to the first side wall 16.The cell housing 12 further comprises a second side wall 18 opposite the first side wall 16, which connects the base 14 to the top wall 20 and encloses the cell stack 30 in a fluid-tight manner. To enable insertion of the cell stack 30 into the cell housing 12, the second side wall 18 in the form of a lid 40 or a cap is placed onto the remaining cell housing 12 after insertion of the cell stack 30 and is preferably integrally connected thereto to produce a fluid-tight cell housing 12.

[0034] The cell stack 30 comprises at least one anode layer 50 and at least one cathode layer 52, which are electrically separated by a separator layer 54 to prevent an electrical short circuit between the anode layer 50 and the cathode layer 52. Preferably, the cell stack 30 has a plurality of anode layers 50 and cathode layers 52, which are arranged alternately in the cell stack 30 and are each separated from one another by a separator layer 54. In a preferred embodiment, each separator layer 54 has contact with the porous guide element 46 at its lower edge in order to receive the electrolyte 38 stored in the porous guide element 46.

[0035] At least one guide element 46, preferably one or more guide rails 34 or a guide sleeve 44, is arranged on the cell stack 30. The guide element 46 protects the outer surfaces of the cell stack 30 against mechanical damage during insertion into the cell housing 12. The guide element 46 has a porous structure 32, which is suitable for receiving and storing at least a small amount of electrolyte 38. In this way, the electrolyte 38 introduced into the battery cell 10 can be fully utilized to supply the cell stack 30.

[0036] Alternatively, the at least one guide element 46 can also be inserted into the cell housing 12 in order to protect the cell stack 30 when it is inserted into the cell housing 12.

[0037] For electrically contacting the cell stack 30, a first terminal 22 and a second terminal 24 are provided, which are arranged in the first sidewall 16 and the second sidewall 18, respectively. The first terminal 22 in the first sidewall 16 is designed as an anode 26 and is electrically connected to the anode layers 50 in the cell stack 30. The second terminal 24 in the second sidewall 18 is designed as a cathode 28 and is electrically connected to the cathode layers 52 in the cell stack 30.

[0038] Furthermore, a ventilation element 42 is provided on the battery cell 10, with which gases and heat generated in the battery cell 10 in the event of a failure of the battery cell 10 can be dissipated in order to regulate the pressure and temperature in the battery cell 10 and to avoid damage to other battery cells 10.

[0039] As an alternative to prismatic battery cells 10 with lateral terminals 22, 24, the invention can also be used in prismatic battery cells 10 with terminals arranged in the ceiling wall 20 or in round cells.

[0040] In Fig. 2 shows a battery cell 10 according to the invention during assembly of the battery cell 10. The cell stack 30 is inserted into the cell housing 12. The cell housing 12 comprises a base 14, a first side wall 16 running perpendicular to the base 14, and a top wall 20 running perpendicular to the first side wall 16 and parallel to the base 14. On a side opposite the first side wall 16, an insertion opening 48 is formed through which a cell stack 30 can be inserted into the cell housing 12. As in Fig. 2, a porous guide element 46, in particular a porous insertion rail 36, is arranged on a side of the cell stack 30 facing the bottom 14 of the cell housing 12 and on a side of the cell stack 30 facing the top wall 20 in order to facilitate the insertion of the cell stack 30 into the cell housing 12. Alternatively, the guide element 46 facing the top wall 20 can also be formed from a plastic without porosity and without electrolyte storage capacity, as in solutions known from the prior art, since the guide element 46, in particular the guide rail 34 between the cell stack 30 and the top wall essentially only serves to protect the cell stack 30 and to facilitate insertion.The guide element 46 between the cell stack 30 and the base 14 is always made of a porous plastic with a storage capacity for electrolyte 38 in order to absorb and store this electrolyte in the pores when filling the battery cell 10 and to release it to the cell stack 30 by capillary action during later operation of the battery cell 10.

[0041] In Fig.3 shows a flow chart for the production of such a battery cell 10. In a first process step <100> a cell housing 12 is provided. In a second process step <110> a porous guide element 46 is inserted into the cell housing 12 or a porous guide element 46 is fixed to a cell stack 30 of the battery cell 10 in order to facilitate subsequent insertion of the cell stack 30 into the cell housing 12 and to avoid mechanical damage to the cell stack 30. In a subsequent process step <120> The cell stack 30 is pushed into the cell housing 12, or the cell housing 12 is pushed onto the stationary cell stack 30. The cell stack 30 or the cell housing 12 is guided by the porous guide element 46, which allows the assembly forces to be kept low.In a further process step <130> An electrolyte is poured into the cell housing 12, whereby the cell stack 30 and the porous guide element 46 are impregnated with the electrolyte. In this process, an amount of electrolyte is stored in the porous guide element 46 that exceeds the amount of electrolyte required for the function of the cell stack. In one process step <140> the cell housing 12 is finally sealed fluid-tight to prevent unwanted and uncontrolled leakage of electrolyte from the battery cell 10. List of reference symbols 10 battery cells 12 cell housings 14 Floor 16 first side wall 18 second side wall 20 ceiling wall 22 first terminal 24 second terminal 26 Anode 28 Cathode 30 cell stacks 32 porous structure 34 Guide rail 36 porous insertion rail 38 Electrolyte 40 lids 42 Ventilation element 44 Guide sleeve 46 Guide element 48 insertion opening 50 anode layer 52 Cathode layer 54 Separator layer

Claims

[1] Battery cell (10) comprising a cell housing (12), a cell stack (30) and a guide element (46) arranged in or formed in the cell housing (12) and / or on the cell stack (30) to facilitate the insertion of the cell stack (30) into the cell housing (12), characterized by , that the guide element (46) is made of a porous material with a storage capacity for electrolyte (38) to supply the cell stack (30). [2] Battery cell (10) according to claim 1, characterized by , that the guide element (46) is a guide rail (34) that can be inserted into the cell housing (12) or comprises a guide rail (34) that can be inserted into the cell housing (12). [3] Battery cell (10) according to claim 1, characterized by , that the guide element (46) is a guide sleeve (44) that can be inserted into the cell housing (12) or comprises a guide sleeve (44) that can be inserted into the cell housing (12). [4] Battery cell (10) according to one of claims 1 to 3, characterized by , that the cell housing (12) comprises a bottom (14), a first side wall (16) and a top wall (20) opposite the bottom (14), wherein the cell housing (12) has an insertion opening (48) on one side opposite the first side wall (16) for introducing the cell stack (30) into the cell housing (12). [5] Battery cell (10) according to claim 4, characterized by , that at least on the bottom (14) or on a side of the cell stack (30) facing the bottom (14) a guide element (46) for introducing the cell stack (30) into the cell housing (12) is arranged or formed. [6] Battery cell (10) according to claim 4 or 5, characterized by , that a guide element (46) for introducing the cell stack (30) into the cell housing (12) is arranged or formed both on the floor (14) and on the ceiling wall (20) or both on a side of the cell stack (30) facing the floor (14) and on a side of the ceiling wall (20). [7] Battery cell (10) according to one of claims 4 to 6, characterized by , that the cell housing (12) comprises a lid (40) with which the insertion opening (48) can be closed after the cell stack (30) has been inserted into the cell housing (12), wherein the lid (40) forms a second side wall (18) opposite the first side wall (16). [8] Battery cell (10) according to claim 7, characterized by , that a first terminal (22) for electrical contacting the cell stack (30) is arranged or formed on the first side wall (16) and a second terminal (24) for electrical contacting the cell stack (30) is arranged or formed on the second side wall (18). [9] Battery cell (10) according to claim 8, characterized by, that the first terminal (22) forms an anode (26) of the battery cell (10) and the second terminal (24) forms a cathode (28) of the battery cell (10) or the first terminal (22) forms a cathode (28) and the second terminal (24) forms an anode (26) of the battery cell (10). [10] Battery cell (10) according to any one of claims 1 to 9, characterized by , that the cell stack (30) has at least one anode layer (50) and one cathode layer (52), wherein the anode layer (50) and the cathode layer (52) are separated from each other by a separator layer (54). [11] Battery cell (10) according to any one of claims 1 to 10, characterized by , that a ventilation element (42) is arranged on the cell housing (12) for the removal of gases and heat in the event of a failure of the battery cell (10). [12] Battery cell (10) according to any one of claims 1 to 11, characterized by, that the guide element (46) is made of a porous plastic, wherein the porosity is such that the pores in the guide element are able to transport the electrolyte into the cell stack (30) by means of capillary action. [13] Battery cell (10) according to claim 12, characterized by that the porous plastic is a sintered plastic, in particular sintered polypropylene. [14] Method for manufacturing a battery cell (10) according to any one of claims 1 to 13, comprising the following steps: - Providing a cell housing (12), - Inserting a porous guide element (46) into the cell housing (12) or fixing a porous guide element (46) to a cell stack (30) of the battery cell (10), - Inserting the cell stack (30) into the cell housing (12) or sliding the cell housing (12) onto the cell stack (30), wherein the cell stack (30) or the cell housing (12) is guided through the porous guide element (46), and - Filling an electrolyte into the cell housing (12), wherein the cell stack (30) and the porous guide element (46) are soaked with the electrolyte, wherein - in the porous guide element (46) an amount of electrolyte is stored which exceeds the amount of electrolyte necessary for the full function of the cell stack (30). [15] Method for manufacturing a battery cell (10) according to claim 14, wherein the cell housing (12) comprises a bottom (14), a first side wall (16) and a top wall (20) opposite the bottom (14) and the cell housing (12) has an insertion opening (48) on one side opposite the first side wall (16), wherein the cell stack (30) is inserted into the cell housing (12) through the insertion opening (48).

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