WO2017080801A1

WO2017080801A1 - Electrode unit for a battery cell and method for the examination of an electrode unit

Info

Publication number: WO2017080801A1
Application number: PCT/EP2016/075518
Authority: WO
Inventors: Markus Berger
Original assignee: Robert Bosch Gmbh
Priority date: 2015-11-10
Filing date: 2016-10-24
Publication date: 2017-05-18
Also published as: DE102015222051A1

Abstract

The invention relates to an electrode unit (10) for a battery cell, comprising an electrode (20), a counter electrode (27) and a separator layer (26) which is arranged between the electrode (20) and the counter electrode (27). The electrode (20) has a first metal conductor layer (21) and a second metal conductor layer (25), between which a first active material layer (22) and a second active material layer (24) are arranged, between which a separator layer (23) is arranged. The invention also relates to a method for the examination of an electrode unit (10) according to the invention, wherein the first metal conductor layer (21) and the second metal conductor layer (25) are electrically short circuited; the electrode unit (10) is electrically charged by applying a voltage between the first metal conductor layer (21) and the counter electrode (27); after charging the electrode unit (10), the first metal conductor layer (21) and the second metal conductor layer (25) are electrically separated; and a potential difference is measured between the first metal conductor layer (21) and the second metal conductor layer (25). The invention likewise relates to a method for the examination of an electrode unit (10) according to the invention, wherein, while the first metal conductor layer (21) and the second metal conductor layer (25) are electrically separated, the electrode unit (10) is electrically charged by applying a voltage between the first metal conductor layer (21) and the counter electrode (27); and during the charging of the electrode unit (10), an internal resistance of the electrode unit (10) is measured between the first metal conductor layer (21) and the counter electrode (27).

Description

Electrode unit for a battery cell and method for examining an electrode unit

The invention relates to an electrode unit for a battery cell, which comprises an electrode, a counter electrode and a separator layer, which is arranged between the electrode and the counter electrode. The invention further relates to two methods for the investigation of an inventive

Electrode unit.

State of the art

Electrical energy can be stored by means of batteries. Batteries convert chemical reaction energy into electrical energy. Here are

Primary batteries and secondary batteries distinguished. Primary batteries are only functional once, while secondary batteries, also referred to as accumulators, are rechargeable. A battery comprises one or more battery cells.

In particular, so-called lithium-ion battery cells are used in an accumulator. These are characterized among other things by high energy densities, thermal stability and extremely low self-discharge. Lithium-ion battery cells are used, inter alia, in motor vehicles, in particular in electric vehicles (EV), hybrid electric vehicles (H EV) and plug-in hybrid electric vehicles (PHEV).

Lithium-ion battery cells have a positive electrode, also known as

Cathode is called, and a negative electrode, which is also referred to as anode on. The cathode and the anode each include one

Current conductor, on which an active material is applied. The active material for the cathode is, for example, a metal oxide. In which Active material for the anode is, for example, graphite or silicon. The current collector and the active material of an electrode can also be formed in one piece. In the active material of the anode Lithiumins are embedded. When operating the

Battery cell, ie during a discharge process, electrons flow in an external circuit from the anode to the cathode. Within the battery cell, lithium ions migrate from the anode to the cathode during a discharge process. The lithium ions from the active material of the anode store reversibly, which is also called deintercalation. When charging the

Battery cell, the lithium ions migrate from the cathode to the anode. In this case, the lithium ions reversibly store back into the active material of the anode, which is also referred to as intercalation. The electrodes of the battery cell are formed like a film and under

Interlayer of a Separatorlage, which separates the anode from the cathode, wound into an electrode coil. Such an electrode winding is also referred to as a jelly roll. The electrodes can also be stacked to form an electrode stack or in another way form an electrode unit. A battery cell usually includes one or more

Electrode units.

The two electrodes of the electrode unit are electrically connected by means of collectors to poles of the battery cell, which are also referred to as terminals. The electrodes and the separator layer are surrounded by a generally liquid electrolyte. The electrolyte is conductive to the lithium ions and allows the transport of the lithium ions between them

Electrodes.

The transport properties for lithium ions in the electrode unit are of the electrolyte used, the separator layer, the temperature, the

Layer thickness and the structure of the active material of the electrodes depends. This also determines the dynamics of the charging processes and of the discharging processes in the electrode unit. To investigate the transport properties of lithium ions in the electrolyte are various investigation methods known, for example, "galvanostatic intermittent titration technique" (GITT), "potentiostatic intermittent titration technique" (PITT), and "pulsed gradient spin-echo nuclear magnetic resonance spectroscopy" (PGSE-NMR). Document DE 10 2011 015 792 A1 discloses a lithium-ion cell which has a positive electrode, a negative electrode and a reference electrode arranged therebetween. The positive electrode and the negative electrode each have two layers of active material

Stromabieiterschicht on.

The document DE 10 2014 220 993 Al discloses a lithium battery with a positive and a negative electrode. The battery includes a housing. The housing is designed as a metal cup. The battery cell additionally comprises a reference electrode, which on the inside of the metal cup

is deposited. The reference electrode serves to evaluate the state of

Battery cell.

Document DE 10 2011 114 613 A1 discloses a battery cell with an electrode unit. The electrode unit in this case comprises a positive electrode, a negative electrode and a separator arranged therebetween. Each of the two electrodes comprises two active material layers, as well as a Stromabieiterschicht.

The document DE 11 2013 000 826 T5 discloses an electrode stack for a battery cell. In this case, the positive electrode as well as the negative include

Electrode in each case a centrally located current collector, as well as on both sides of an active material layer. The positive electrode and two separator layers each form a structural unit. Disclosure of the invention

An electrode unit for a battery cell is proposed which comprises an electrode, a counterelectrode and a separator layer. The

Separator layer is arranged between the electrode and the counter electrode. The electrode unit serves primarily for examinations of transport properties for lithium ions in the active material of a

Electrode. The electrode unit preferably has only one layer, which comprises the electrode, the counter electrode and the separator layer. The electrode, the counter electrode and the separator layer therefore do not have to be wound or stacked into several layers.

According to the invention, the electrode of the electrode unit has a first metallic conductor layer and a second metallic conductor layer. Between the two metallic conductor layers of the electrode are a first

Active material layer and a second active material layer arranged. Between the two active material layers of the electrode, a separator layer is arranged. The electrode is thus constructed symmetrically with respect to the centrally located separator layer. In this case, the second metallic conductor layer faces the separator layer, and the first metallic conductor layer is the

Facing away separator layer. The first active material layer is located between the first metallic conductor layer and the separator layer, and the second active material layer is located between the second metallic conductor layer and the separator layer.

According to an advantageous development of the invention, the first metallic conductor layer of the electrode is electrically connected to a first connection contact, the second metallic conductor layer of the electrode is electrically connected to a second connection contact, and the counterelectrode is electrically connected to a mating connection contact. The electrode unit thus has three externally accessible connection contacts, which can be contacted, for example, to carry out measurements of electrical variables within the electrode unit.

According to an advantageous embodiment of the invention, the first metallic conductor layer of the electrode is designed as a metal mesh network. Furthermore, the second metallic conductor layer of the electrode is advantageously designed as a metal mesh with meshes. The meshes of the metal net ensure one

Permeability of the metallic conductor layer for electrolyte. Thus, one is

Transport of lithium ions by means of electrolyte through the metallic conductor layer possible. Preferably, the meshes of the metal mesh have a mesh size in the range of 1 μηη to 200 μηη. The ratio of mesh size to

Wire mesh diameter should be as high as possible. The thickness of the metal mesh is preferably in a range of less than 100 μηη.

Advantageously, the first active material layer of the electrode and the second active material layer of the electrode are made of the same material. The two active material layers of the electrode thus correspond to one

Active material layer separated by the central separator layer. The

Separator layer is electrically insulating and prevents electrical conductivity between the first metallic conductor layer and the second metallic conductor layer.

According to an advantageous embodiment of the invention, the counter electrode of the electrode unit is designed as a lithium-metal electrode. The

Counter electrode is thus formed in one piece and combines current collector and active material in a single layer.

It is also a method for examining an inventive

Electrode unit proposed. According to this method, while the first metallic conductor layer of the electrode and the second metallic

Conductor layer of the electrode are electrically short-circuited, for example, by closing a switch, the electrode unit by applying a voltage between the first metallic conductor layer and the counter electrode electrically charged.

In this case, the second active material layer of the electrode, which reaches the

Counter electrode is located, a higher state of charge than the first active material layer of the electrode, which is located away from the counter electrode. Thus, a charge state gradient arises within the active material of the electrode. The reason for this is an inhibition of the transport of

Lithium ions pass through the active material. The first metallic

Conductor layer and the second metallic conductor layer have, due to the short circuit, the same potential. After loading the electrode unit, the first metallic

Conductor layer and the second metallic conductor layer, for example, by opening the switch, electrically isolated, the short circuit is therefore canceled. Subsequently, a potential difference between the first metallic

Conductor layer and the second metallic conductor layer measured. Due to the measured potential difference between the first metallic conductor layer and the second metallic conductor layer, it is possible to respond to the different states of charge of the first active material layer and the second

Active material layer are closed. This allows the

Transport properties for lithium ions in the second active material layer of the electrode are evaluated.

In addition, a potential difference between the first metallic conductor layer and the counter electrode and a potential difference between the second metallic conductor layer and the counter electrode can be measured. By measuring the two potential differences between the metallic conductor layers and the counter electrode, a middle

Charge state of the two active material layers of the electrode can be determined. There is also a space between the two active material layers

Charge balance instead. After a certain period of time, the potential of the first active material layer is thus approximately equal to the potential of the second active material layer. It will be another method for examining an inventive

Electrode unit proposed. According to this further method, while the first metallic conductor layer of the electrode and the second metallic conductor layer of the electrode are electrically separated, the

Electrode unit by applying a voltage between the first

metallic conductor layer and the counter electrode electrically charged. The second metallic conductor layer is not connected, that is isolated from the first metallic conductor layer and the counter electrode.

In this case, only the first active material layer of the electrode is charged. The second active material layer of the electrode acts like an additional separator beside the Separator layer of the electrode and the separator layer of the electrode unit. The second active material layer of the electrode thus hinders the transport of the lithium ions, which migrate through the second active material layer of the electrode.

During charging of the electrode unit, an internal resistance of the electrode unit between the first metallic conductor layer and the counter electrode is measured. The transport properties of lithium ions in the second active material layer of the electrode can be evaluated by the internal resistance of the electrode unit.

Optionally, an additional voltage may be applied between the second metallic conductor layer and the counter electrode. As a result, the second active material layer of the electrode can likewise be charged or discharged. The internal resistance of the electrode unit between the first metallic

Conductor layer and the counter electrode and the transport properties for lithium ions in the second active material layer of the electrode can thus be measured and evaluated at different states of charge of the second active material layer.

Advantages of the invention

The electrode unit according to the invention, in conjunction with the methods according to the invention, permits an investigation of the transport properties for lithium ions in the active material layer of the electrode. Furthermore, they are separate

Measurements of the electrode potential in a region near a Stromableiters and a remote from the current collector range, or in a separator layer remote area and a separator layer near range possible. Thus, the transport properties of lithium ions in the active material layer of the electrode can be qualitatively and quantitatively evaluated.

In particular, the rate of charge equalization perpendicular to the electrode surface, that is along a charge state gradient within the active material of the electrode, can be determined.

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

Figure 1: a first circuit for the investigation of an inventive

Electrode unit and

Figure 2: a second circuit for the investigation of an inventive

Electrode unit.

Embodiments of the invention

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

FIG. 1 shows a first circuit for examining an electrode unit 10 according to the invention. The electrode unit 10 comprises an electrode 20, a counter electrode 27 and a separator layer 26, which is arranged between the electrode 20 and the counter electrode 27. The counter electrode 27 is embodied here as a one-piece lithium-metal electrode.

The electrode 20 has a multilayer structure and in the present case has five layers. These are a first metallic conductor layer 21, a second metallic conductor layer 25, a first active material layer 22, a second active material layer 24 and a separator layer 23. The first metallic conductor layer 21 and the second metallic conductor layer 25 are designed as a metal mesh network. The first active material layer 22 and the second active material layer 24 are configured identically and in particular made of the same active material.

The separator layer 23 of the electrode 20 is centrally located and surrounded by the first active material layer 22 and the second active material layer 24. On one of the Separatorschicht 23 opposite side of the first active material layer 22, the first metallic conductor layer 21 is arranged. On one of the

Separator layer 23 opposite side of the second active material layer 24, the second metallic conductor layer 25 is arranged. The electrode 20 is thus configured symmetrically with respect to the centrally arranged separator layer 23.

The electrode 20 is arranged inside the electrode unit 10 such that the second metallic conductor layer 25 faces the separator layer 26. The first metallic conductor layer 21 of the electrode 20 is thus the

Separator layer 26 facing away. On a side facing away from the electrode 20 of the separator layer 26, the counter electrode 27 is arranged.

A first terminal contact 31 is electrically connected to the first metallic one

Conductor layer 21 is connected, a second terminal contact 35 is electrically connected to the second metallic conductor layer 25, and a

Counter connection contact 37 is electrically connected to the counter electrode 27. Thus, the electrode unit 10 has three externally contactable

Terminal contacts 31, 35, 37, by means of which measurements of electrical variables within the electrode unit 10 can be carried out. Furthermore serve the

Connection contacts 31, 35, 37 also for loading or unloading the

Electrode unit 10, in particular the active material layers 22, 24th

Between the first connection contact 31 and the second connection contact 35, a switch 41 is arranged. By closing the switch 41, a

Short circuit between the first metallic conductor layer 21 and the second metallic conductor layer 25 are generated.

Further, between the first terminal contact 31 and the second

Terminal contact 35 a voltmeter 42 is arranged. The

Voltage measuring device 42 is thus arranged parallel to the switch 41. When the switch 41 is opened, a voltage, or a potential difference, between the first metallic conductor layer 21 and the second metallic conductor layer 25 can then be measured by means of the voltage measuring device 42. Between the first terminal contact 31 and the mating terminal contact 37, another, not shown here measuring device for measuring a

Voltage between the first metallic conductor layer 21 and the

Counter electrode 27 may be arranged. Likewise, between the second terminal contact 35 and the mating terminal contact 37 another, also not shown here measuring device for measuring a voltage between the second metallic conductor layer 25 and the counter electrode 27 may be arranged.

Between the first connection contact 31 and the mating contact 37, a voltage source 45 is connected. By applying a voltage by means of the voltage source 45 between the first terminal contact 31 and the mating terminal contact 37, the electrode unit 10, in particular the first active material layer 22 of the electrode 20, can be charged.

FIG. 2 shows a second circuit for examining the electrode unit 10 according to the invention. The electrode unit 10 is constructed identically to the electrode unit 10 shown in FIG. 1 and comprises an electrode 20 having five layers, a counterelectrode 27 and a

Separator layer 26 which is disposed between the electrode 20 and the counter electrode 27.

Further, like the electrode unit 10 shown in FIG. 1, a first terminal contact 31 is electrically connected to the first metal conductor layer 21, a second terminal contact 35 is electrically connected to the second metal conductor layer 25, and a mating terminal contact 37 is electrically connected to the counter electrode 27 connected.

Between the first connection contact 31 and the mating contact 37, a voltage source 45 is connected. By applying a voltage by means of the voltage source 45 between the first terminal contact 31 and the mating terminal contact 37, the electrode unit 10, in particular the first active material layer 22 of the electrode 20, can be charged. Between the second connection contact 35 and the mating terminal contact 37, a voltage source 45 is also connected. By applying a voltage by means of the voltage source 45 between the second

Terminal contact 35 and the mating terminal 37, the

Electrode unit 10, in particular the second active material layer 24 of the electrode 20, are charged.

Between the first connection contact 31 and the mating contact 37, a measuring device, not shown here, is arranged. By means of this measuring device, an internal resistance of the electrode unit 10 between the first metallic conductor layer 21 of the electrode 20 and the counter electrode 27 can be measured.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

Claims

claims

An electrode unit (10) for a battery cell, comprising

an electrode (20),

a counter electrode (27) and

a separator layer (26) disposed between the electrode (20) and the counter electrode (27),

characterized in that

the electrode (20)

a first metallic conductor layer (21) and a second metallic conductor layer (25),

between which a first active material layer (22) and a second

Active material layer (24) are arranged,

between which a separator layer (23) is arranged.

2. electrode unit (10) according to claim 1, characterized in that the first metallic conductor layer (21) with a first

Terminal contact (31) is electrically connected, and that

the second metallic conductor layer (25) with a second

Terminal contact (35) is electrically connected, and that

the counter electrode (27) is electrically connected to a mating terminal contact (37).

3. electrode unit (10) according to any one of the preceding claims,

characterized in that

the first metallic conductor layer (21) and / or the second metallic conductor layer (25) are designed as a metal mesh network.

4. electrode unit (10) according to claim 3, characterized in that the meshes have a mesh size in the range of 1 μηη to 200 μηη.

Electrode unit (10) according to one of the preceding claims, characterized in that

the first active material layer (22) and the second active material layer

(24) are made of the same material.

the counter electrode (27) is designed as a lithium-metal electrode.

A method of inspecting an electrode assembly (10) according to any one of the preceding claims, wherein

while the first metallic conductor layer (21) and the second metallic conductor layer (25) are electrically short-circuited, the electrode unit (10) is electrically charged by applying a voltage between the first metallic conductor layer (21) and the counter electrode (27),

after charging the electrode unit (10), the first metallic conductor layer (21) and the second metallic conductor layer (25) are electrically separated, and

a potential difference between the first metallic conductor layer (21) and the second metallic conductor layer (25) is measured.

A method of inspecting an electrode assembly (10) according to claim 7, wherein subsequently

a potential difference between the first metallic conductor layer (21) and the counter electrode (27) and / or

a potential difference between the second metallic conductor layer

(25) and the counter electrode (27) is measured.

9. A method for examining an electrode unit (10) according to any one of claims 1 to 6, wherein

while the first metallic conductor layer (21) and the second metallic conductor layer (25) are electrically separated,

the electrode unit (10) is electrically charged by applying a voltage between the first metallic conductor layer (21) and the counter electrode (27), and

during charging of the electrode unit (10), an internal resistance of the electrode unit (10) between the first metallic conductor layer (21) and the counter electrode (27) is measured.

A method of inspecting an electrode unit (10) according to claim 9, wherein during charging the electrode unit (10)

a voltage is applied between the second metallic conductor layer (25) and the counter electrode (27).