DE102018220388A1 - Battery system - Google Patents

Abstract

The invention relates to a battery system (10) comprising a negative terminal (11), a positive terminal (12) and a plurality of cell stacks (40), the cell stacks (40) being connected in parallel with one another, each cell stack (40) having one Comprises a plurality of cell units, the cell units being stacked one above the other and connected in series with one another, and each cell unit comprising an anode, a cathode and a separator arranged between the anode and the cathode.

Description

The invention relates to a battery system, in particular a lithium-ion battery system, which comprises a negative terminal, a positive terminal and cell units, each cell unit comprising an anode, a cathode and a separator arranged between the anode and the cathode.

State of the art

Electrical energy can be stored using batteries. Batteries convert chemical reaction energy into electrical energy. In particular, accumulators are known which are rechargeable. For example, lithium-ion batteries are used in an accumulator. These are characterized, among other things, by high energy densities, thermal stability and extremely low self-discharge. Lithium-ion batteries are used, among other things, in motor vehicles, in particular in electric vehicles (EV), hybrid vehicles (hybrid electric vehicle, HEV) and plug-in hybrid vehicles (plug-in hybrid electric vehicle, PHEV). Lithium-ion batteries have at least one positive electrode, which is also called a cathode, and at least one negative electrode, which is also called an anode. The cathode and the anode each comprise an active material layer which has a corresponding electrochemical active material.

In the production of a lithium-ion battery, layers of the anode and layers of the cathode are placed on top of one another with the interposition of a separator. 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.

From the DE 10 2015 202 894 A1 a battery cell is known which has an electrode stack with an anode and a cathode. The anode and the cathode comprise a plurality of plate-shaped segments which are layered one above the other with the interposition of plate-shaped separators to form the electrode stack.

Battery systems for use in electric vehicles have a high capacity of, for example, 40 kWh and a high voltage of, for example, 400 V. These battery systems consist of individually packaged battery cells together with a voltage of 3.5 V each and a high capacity. These battery cells are connected in series until the desired voltage of the battery system is reached, typically between 80 and 120 battery cells. Of these strings of battery cells connected in series, so many are connected in parallel until the desired capacity of the battery system is reached, typically 1 to 5 strings.

The battery cells are subject to fluctuations in terms of their usable capacity and their internal resistance. As a result, the weakest battery cell in a string of battery cells connected in series determines the charge and discharge with regard to the duration and capacity of all the battery cells in the string. Separation of the battery cells is only possible due to the series connection if a battery cell is short-circuited by a parallel connection.

The document JP 2014-072181 discloses a cell stack having a plurality of cell units stacked one on top of the other. Each cell unit has an anode, a cathode and a separator arranged between the anode and the cathode.

The document too JP 2012-089421 discloses a cell stack having a plurality of cell units stacked one on top of the other. Each cell unit has an anode, a cathode and a separator arranged between the anode and the cathode.

Disclosure of the invention

A battery system, in particular a lithium-ion battery system, is proposed. The battery system includes a negative terminal, a positive terminal and a plurality of cell stacks. The individual cell stacks are electrically connected to one another in parallel. Each of said cell stacks comprises a plurality of cell units. The individual cell units are stacked on top of one another and electrically connected in series.

Each of said cell units comprises an anode, a cathode and a separator arranged between the anode and the cathode. The anode contains, for example, graphite, silicon or a mixture of these substances as the active material. Other active materials are also conceivable. The cathode contains, for example, an alloy of nickel, cobalt and manganese (NCM) or lithium manganese oxide (LMO) or lithium iron phosphate (LFP) as the active material. Other active materials are also conceivable. The separator is ionically conductive but electrically non-conductive.

Each of the cell units has a cell voltage of approximately 3.5 V, for example. For example, if the cell stack is a hundred electrical comprises cell units connected in series with one another, the cell stack has a stack voltage of approximately 350 V. Each of the cell stacks has only a relatively low capacity of, for example, 4 kWh and can only deliver a relatively low current. For example, if ten cell stacks are electrically connected in parallel, the battery system has a capacity of 40 kWh, for example. The current that can be supplied by the battery system is also correspondingly higher than the current that can be supplied by a cell stack.

Preferably, a number of cell units in each cell stack is larger than a number of cell stacks in the battery system. For example, each cell stack comprises a hundred cell units electrically connected in series, and the battery system comprises ten cell stacks electrically connected in parallel.

According to an advantageous embodiment of the invention, an electrically conductive intermediate layer is arranged in each cell stack between two adjacent cell units. The intermediate layer is designed, for example, in the form of a metallic foil, in particular made of copper or aluminum. The intermediate layer can also be designed in the form of a composite film with two or more materials.

The electrically conductive intermediate layer preferably abuts the anode of a cell unit and the cathode of the adjacent cell unit. This provides a high electrical conductivity between two adjacent cell units.

According to another advantageous embodiment of the invention, an electrically conductive intermediate layer is integrated in the anodes and / or in the cathodes of the cell units. The integrated intermediate layer is then in each case on the anode or on the cathode of the adjacent cell unit.

According to an advantageous embodiment of the invention, each cell stack comprises a negative current collector and a positive current collector. The negative current conductor is designed to be electrically conductive and is made, for example, of a metal, in particular of copper. The positive current conductor is designed to be electrically conductive and, for example, made of a metal, in particular aluminum.

The negative current arrester is in contact with an externally arranged cell unit, and the positive current arrester is in contact with an oppositely arranged cell unit. The cell units are thus arranged between the negative current conductor and the positive current conductor.

Preferably, the negative current conductor bears against the anode of the cell unit arranged on the outside, and the positive current conductor bears against the cathode of the cell unit arranged opposite on the outside.

According to an advantageous development of the invention, the negative current conductors of the cell stacks are electrically connected to one another and to the negative terminal of the battery system. The positive current arresters of the cell stacks are also electrically connected to one another and to the positive terminal of the battery system.

According to an advantageous embodiment of the invention, the separators of the cell units have a liquid electrolyte. The separator is soaked with the electrolyte, for example. The electrolyte increases the ionic conductivity of the separator.

According to another advantageous embodiment of the invention, the separators of the cell units have a solid electrolyte. The solid electrolyte has a particularly high conductivity, especially for lithium ions, and is not electrically conductive. The solid electrolyte is inorganic, in particular sulfidic, oxidic or polymeric.

A battery system according to the invention is advantageously used in an electric vehicle (EV), in a hybrid vehicle (HEV) or in a plug-in hybrid vehicle (PHEV). However, other uses for the battery system according to the invention are also not excluded.

Advantages of the invention

As a result of the construction of the battery system according to the invention, the output voltage of the battery system can be predetermined by appropriately selecting the number of cell units per cell stack. The capacity of the battery system can be specified by selecting the number of cell stacks accordingly. Due to the parallel connection of the cell stacks, the individual cell stacks can be controlled separately during loading and unloading and thus loaded and unloaded individually. Thus, a weakening or aging battery cell does not limit the performance of a series of several battery cells. A weakening or aging cell stack only affects the capacity of the respective cell stack.

The individual layers of a cell unit, i.e. anode, separator and cathode, can for example, prefabricated and then stacked on top of each other. The cell units produced in this way, in particular with correspondingly prefabricated intermediate layers, can then be stacked to form a cell stack. However, the individual layers can also be applied alternately, for example, by means of additive manufacturing processes, alternating anode - separator - cathode - possibly intermediate layer - anode - separator - cathode and so on.

Figure list

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

• 1 eine schematische Darstellung einer Zelleinheit,
• 2 eine schematische Darstellung eines Zellenstapels und
• 3 eine schematische Darstellung eines Batteriesystems.

Show it:

• 1 a schematic representation of a cell unit,
• 2nd a schematic representation of a cell stack and
• 3rd a schematic representation of a battery system.

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, with a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

1 shows a schematic representation of a cell unit 50 . The cell unit 50 includes an anode 21st and a cathode 22 . The anode 21st contains an anodic active material, for example graphite, silicon or a mixture of these substances. However, other anodic active materials are also conceivable.

The cathode 22 contains a cathodic active material, for example an alloy of nickel, cobalt and manganese (NCM) or lithium manganese oxide (LMO) or lithium iron phosphate (LFP). However, other cathodic active materials are also conceivable.

The cell unit 50 also includes a separator 18th which is between the anode 21st and the cathode 22 is arranged. The separator 18th is ionically conductive, i.e. permeable to lithium ions. The separator 18th but is electrically insulating, i.e. not conductive for electrons. The separator 18th can, for example, be impregnated with a liquid electrolyte. The separator 18th can also have a solid electrolyte.

The anode 21st who have favourited Cathode 22 and the separator 18th are each flat and plate-shaped. That means a length and a width of the anode 21st , the cathode 22 and the separator 18th are significantly larger than the thickness of the anode 21st , the cathode 22 and the separator 18th , preferably over a hundred times larger.

2nd shows a schematic representation of a cell stack 40 . The cell stack 40 includes a plurality of in 1 shown cell units 50 . For example, the cell stack includes 40 hundred cell units 50 . The cell stack 40 further comprises a plurality of electrically conductive intermediate layers 60 . The number of liners 60 is one less than the number of cell units 50 . The liners 60 are designed, for example, in the form of a metallic foil, in particular made of copper or aluminum. The liner 60 can also be designed in the form of a composite film with two or more materials.

Alternatively, in the anodes 21 and / or in the cathodes 22 of the cell units 50 also an electrically conductive intermediate layer 60 be integrated. The integrated liner 60 then lies on the anode 21st or on the cathode 22 the adjacent cell unit 50 at.

The individual cell units 50 are stacked one on top of the other, with two adjacent cell units 50 one electrically conductive intermediate layer each 60 is arranged. The cell units 50 and the liners 60 are arranged so that each liner 60 each on the anode 21st a cell unit 50 and on the cathode 22 the adjacent cell unit 50 is present. The individual cell units 50 are thus electrically connected in series.

The cell units 50 and the liners 60 are each flat and plate-shaped. That means a length and a width of the cell units 50 and the liners 60 are significantly larger than a thickness of the cell units 50 and the liners 60 , preferably over a hundred times larger.

The cell stack 40 also includes a negative current collector 31 and a positive current collector 32 . The negative current collector 31 is electrically conductive and made of a metal, in the present case of copper. The positive current arrester 32 is also electrically conductive and made from a metal, in the present case from aluminum.

The negative current collector 31 is due to the anode 21st an external cell unit 50 of the cell stack 40 . Here is the negative current conductor 31 with said anode 21st electrically connected. The positive current arrester 32 is on the cathode 22 the cell unit located on the outside opposite 50 at. Here is the positive current arrester 32 with the said cathode 22 electrically connected.

In the cathodes 22 of the cell units 50 lithium atoms are stored. When the cell units are being charged 50 Lithium ions migrate from the cathode 22 through the separator 18th to the anode 21st . The lithium ions in the anode 21st stored. At the same time, electrons flow from the cathode 22 through the adjacent liner 60 to the anode 21st the neighboring cell unit 50 .

From the cathode 22 the cell unit located on the outside 50 Electrons flow to the positive current conductor during a charging process 32 . From the positive current arrester 32 The electrons then flow in an external circuit to the negative current collector 31 and on to the anode 21st the cell unit located on the outside opposite 50 .

When the cell units are discharged 50 lithium ions migrate from the anode 21st through the separator 18th to the cathode 22 . The lithium ions are stored in the anode 21st reversible. At the same time, electrons flow from the anode 21st through the adjacent liner 60 to the cathode 22 the neighboring cell unit 50 .

From the anode 21st the cell unit located on the outside 50 Electrons flow to the negative current conductor during a discharge process 31 . From the negative current collector 31 The electrons then flow in an external circuit to the positive current conductor 32 and on to the cathode 22 the cell unit located on the outside opposite 50 .

Each of the cell units 50 has a cell voltage of approximately 3.5 V in the present case. The cell stack 40 points due to the electrical serial connection of the cell units 50 a stack voltage, which is the sum of the cell voltages of the individual cell units 50 corresponds. The present cell stack 40 So a stack voltage of about 350 V.

3rd shows a schematic representation of a battery system 10th . The battery system 10th includes a negative terminal 11 and a positive terminal 12 . Via the two terminals 11 , 12 can be one of the battery system 10th provided output voltage can be tapped. Furthermore, the battery system 10th via the two terminals 11 , 12 also be loaded.

The battery system 10th includes a plurality of in 2nd shown cell stacks 40 . For example, the battery system includes 10th ten cell stacks 40 . The negative current arrester 31 the cell stack 40 are electrical with each other and with the negative terminal 11 of the battery system 10th connected. The positive current arresters are also 32 the cell stack 40 electrically with each other and with the positive terminal 12 of the battery system 10th connected. So the individual cell stacks 40 electrically connected in parallel.

Each of the cell stacks 40 here has a capacity of about 4 kWh. The battery system 10th has a capacity which is the sum of the capacities of the individual cell stacks 40 corresponds. The present shows the battery system 10th So a capacity of about 40 kWh.

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

• DE 102015202894 A1 [0004]
• JP 2014072181 [0007]
• JP 2012089421 [0008]

Claims (11)

Battery system (10) comprising a negative terminal (11), a positive terminal (12) and a plurality of cell stacks (40), wherein the cell stacks (40) are connected in parallel with one another, each cell stack (40) comprising a plurality of cell units (50), the cell units (50) being stacked one above the other and connected in series with one another, and each cell unit (50) comprising an anode (21), a cathode (22) and a separator (18) arranged between the anode (21) and the cathode (22). Battery system (10) after Claim 1 wherein a number of cell units (50) in each cell stack (40) is greater than a number of cell stacks (40) in the battery system (10). Battery system (10) according to one of the preceding claims, wherein an electrically conductive intermediate layer (60) is arranged in each cell stack (40) between two adjacent cell units (50). Battery system (10) after Claim 3 , wherein the electrically conductive intermediate layer (60) abuts the anode (21) of a cell unit (50) and the cathode (22) of the adjacent cell unit (50). Battery system (10) according to one of the Claims 1 to 2nd , In each case an electrically conductive intermediate layer (60) is integrated in the anodes (21) and / or in the cathodes (22) of the cell units (50), each of which is adjacent to the anode (21) or to the cathode (22) arranged cell unit (50) is present. The battery system (10) according to one of the preceding claims, wherein each cell stack (40) comprises a negative current collector (31) and a positive current collector (32), wherein the negative current conductor (31) abuts an externally arranged cell unit (50), and wherein the positive current arrester (32) rests on an opposite cell unit (50). Battery system (10) after Claim 6 , wherein the negative current conductor (31) bears on the anode (21) of the one cell unit (50) arranged on the outside, and wherein the positive current conductor (32) bears on the cathode (22) of the cell unit (50) arranged on the outside on the outside. Battery system (10) according to one of the Claims 6 to 7 , wherein the negative current conductors (31) of the cell stack (40) are electrically connected to one another and to the negative terminal (11), and wherein the positive current collectors (32) of the cell stack (40) are electrically connected to one another and to the positive terminal (12) are. Battery system (10) according to one of the preceding claims, wherein the separators (18) of the cell units (50) have a liquid electrolyte. Battery system (10) according to one of the Claims 1 to 8th , wherein the separators (18) of the cell units (50) have a solid electrolyte. Use of a battery system (10) according to one of the preceding claims in an electric vehicle (EV), in a hybrid vehicle (HEV) or in a plug-in hybrid vehicle.

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