DE102016210838A1 - Anode for a battery cell, method for making an anode and battery cell - Google Patents

Abstract

The invention relates to an anode (21) for a battery cell, comprising a current conductor (31) and an anodic active material (41) which contains lithium and is applied to the current conductor (31). A contact lug (35) of the current collector (31) is free of anodic active material (41). The invention also relates to a method for producing an anode (21), wherein a current conductor (31), which is porous and has pores, is coated on a first side with a first foil which contains lithium, the pores of the current conductor (31 ) are at least substantially filled with lithium, and the current conductor (31) is coated on a second side with a second film containing lithium. The invention also relates to a battery cell comprising at least one anode (21) according to the invention.

Description

The invention relates to an anode for a battery cell, which comprises a current conductor and an active material which contains lithium and is applied to the current conductor. The invention further relates to a method for producing an anode and a battery cell, which comprises an anode according to the invention.

State of the art

Electrical energy can be stored by means of batteries. Batteries convert chemical reaction energy into electrical energy. Here, a distinction is made between primary batteries and secondary batteries. 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 vehicles (HEV) and plug-in hybrid electric vehicles (PHEV).

Lithium-ion battery cells have a positive electrode, also referred to as a cathode, and a negative electrode, also referred to as an anode. As anodes, inter alia lithium-metal anodes are used. Such an anode comprises a metal layer which contains lithium or a lithium alloy.

Lithium atoms are embedded in the anode. During operation of 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. During a charging process of the battery cell, the lithium ions within the battery cell migrate from the cathode to the anode, and electrons flow in an external circuit from the cathode to the anode.

The electrodes of the battery cell are formed like a foil and, with the interposition of a separator, which separates the anode from the cathode, for example wound into an electrode winding. Such an electrode winding is also referred to as a jelly roll. Alternatively, the anode, cathode and separator may also be superimposed to form an electrode stack. The two electrodes of the electrode coil or electrode stack are electrically connected by means of collectors to poles of the battery cell, which are also referred to as terminals. A battery cell usually comprises one or more electrode units.

From the DE 10 2013 224 294 A1 For example, a battery cell is known which has a lithium metal electrode as the anode. The lithium metal electrode comprises a foil-like current conductor, which consists for example of copper, and an electrode coating, which consists for example of lithium.

The CN 103794800 discloses an electrode with a porous current collector, which is formed for example net-like. The current conductor is made of copper, for example, and filled with a filler containing lithium. In addition, the current conductor may be coated with a lithium-containing material.

In the US 2015/0037689 A1 There is disclosed a lithium secondary battery comprising a positive electrode and a negative electrode each having, as a current collector, a three-dimensional network porous body. The porous body for the negative electrode is a copper body whose pores are filled with an active material. The active material is, for example, lithium.

Disclosure of the invention

An anode for a battery cell is proposed. The anode comprises a current conductor and an anodic active material which contains lithium and is applied to the current conductor. Preferably, the anodic active material is applied to both sides of the current conductor of the anode. The thickness of the anodic active material is preferably in the range between 1 .mu.m and 2 .mu.m.

The current collector has a contact lug, which serves for electrically contacting the current collector. The contact lug protrudes away from the rest of the anode. According to the invention, the contact lug of the current conductor is free of anodic active material. So there is no lithium on a surface of the contact lug.

Preferably, the current conductor is formed porous and has pores, which are at least largely filled with a filler material containing lithium. The pores of the contact lug of the current collector are at least largely free of filling material. So there is no lithium in the pores of the contact lug.

According to an advantageous embodiment of the invention, the current conductor of the anode is as a Expanded metal formed of copper. Such an expanded metal can be produced by methods known to the person skilled in the art. Said expanded metal preferably has a thickness of less than 25 μm. Particularly preferably, the expanded metal has a thickness of less than 15 μm. Particularly preferably, the expanded metal has a thickness of less than 10 μm.

Preferably, the expanded metal has a mesh size of less than 1 mm. Particularly preferably, the expanded metal has a mesh size of less than 100 μm.

Alternatively, the current conductor of the anode can also be formed as a tissue made of copper. Likewise, the current conductor of the anode may also comprise sintered copper chips and copper fibers.

According to a further advantageous embodiment of the invention, the current conductor of the anode is formed as a fabric of carbon fibers. The said tissue preferably has a thickness of less than 30 μm. Particularly preferably, said tissue has a thickness of less than 20 microns.

Preferably, the carbon fibers of the fabric each have a thickness between 1/2 and 1/10 of the thickness of the fabric.

Also, the current conductor of the anode may be formed as a solid sheet of copper, which has a thickness of less than 10 microns. In particular, the current conductor of the anode formed as a solid sheet of copper has a thickness in the range between 5 μm and 6 μm.

Furthermore, a method for producing an anode is proposed. According to the method, a current conductor is first coated on a first side with a first film. The first film contains lithium or consists of lithium. The current collector of the anode is porous and has pores.

The coating of the current collector with the first film preferably takes place in a roll-to-roll process. If the current conductor is designed as an expanded metal, the expanded metal is produced by means of known methods, not described here, and is preferably used as a roll material.

After coating, the current collector is calendered with the first film. The calendering takes place in such a calender that the pores of the current collector are at least largely filled with lithium from the first film. The lithium from the first film is pressed into the pores of the current collector during calendering. The lithium from the first film located in the pores of the current collector after calendering thus represents a filling material.

After calendering, the current conductor is coated on a second side, which is opposite to the first side, with a second film. The second film also contains lithium or consists of lithium. Also, the coating of the current collector with the second film is preferably carried out in a roll-to-roll process.

After coating the current conductor of the anode, the lithium of the first film and the lithium of the second film constitute an anodic active material of the anode. The current conductor of the anode is thus coated on both sides with anodic active material.

The first sheet of lithium in this case has a thickness which is dimensioned such that with it the pores of the current conductor can be filled with lithium as filler, and that the remaining thickness of the first film then exactly the required for the cyclization thickness of the anodic active material on the first side of the current collector of the anode corresponds. The second foil of lithium has a thickness which corresponds to the required for cyclization thickness of the anodic active material on the second side of the current conductor of the anode.

As an alternative to calendering the current conductor with the first foil, it is also conceivable that the pores of the current conductor are at least largely filled with lithium galvanically and / or electrochemically.

If a lithium-containing cathodic active material is also used in the battery cell, only a relatively thin layer of about 1 μm on the anode is required for the cyclization in order to ensure homogeneous deposition of lithium on the anode.

According to a preferred embodiment of the method according to the invention, a contact lug of the current conductor during coating remains free of lithium.

Likewise, the pores of the contact lug remain at least largely free of lithium during calendering and during the galvanic and / or electrochemical filling of the pores of the current conductor.

In particular, the current conductor is coated in the region of the contact lug neither with the first foil nor with the second foil which contains lithium. Thus, calendering also occurs no lithium in the pores of the current conductor. The contact lug of the current collector protrudes away from the rest of the anode and is used for electrical contact of the current conductor.

According to a preferred development of the method according to the invention, the first film is provided with a first polymer film on a side facing away from the current conductor before coating. Likewise, prior to coating, the second film is provided with a second polymer film on a side facing away from the current collector. The first polymer film and the second polymer film are removed after coating the current collector of the first film and the second film. The first polymer film and the second polymer film are preferably made of PP or PTFE.

A battery cell is also proposed which comprises at least one anode according to the invention.

A battery cell according to the invention advantageously finds use in an electric vehicle (EV), in a hybrid vehicle (HEV), in a plug-in hybrid vehicle (PHEV), in an electric bicycle or in a portable device, in particular in a mobile telephone, in a tablet a laptop or a power tool.

Advantages of the invention

Battery cells with lithium metal anodes whose active material contains lithium have relatively high volumetric energy densities and increased specific energy. By suitable choice of the volume ratio of copper and lithium in the current conductor, in particular in the case of the execution as expanded metal or fabric, but also as sintered copper chips and copper fibers, the total mass of the current conductor can be kept constant, whereby the volumetric energy density continues to increase and the specific energy slightly increases or at least does not decrease.

In comparison with a pure lithium foil as a current conductor, a foil containing copper is mechanically more stable, easier to handle and thus thinner than a pure lithium foil. Thus, the copper-containing film can also be designed with reduced weight. Furthermore, the current dissipation is improved compared to a pure lithium anode foil.

Also contacting the Stromableiters and in particular the current dissipation through the anode is improved due to the higher electrical conductivity of the copper compared to lithium.

In comparison to lithium-metal anodes known from the prior art, an anode according to the invention has a reduced or slowed aging. Even with a thinning out of the lithium remains a defined residual thickness of the anode, which always corresponds at any point at least the thickness of the Stromableiters. An excess of lithium is minimized, which improves the safety of the cell. The less lithium metal is present in the battery cell, the safer the cell, since lithium is a very strong reducing agent.

An anode according to the invention can be used in particular for the realization of battery cells having a solid electrolyte, high electrode loadings with active material of up to 3 mAh / cm ² and at the same time allow a high constant current loads of up to 3C or higher in the loading direction and in the discharge direction.

Brief description of the drawings

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

Show it:

1 a schematic representation of a battery cell,

2 a schematic sectional view of an anode and

3 a schematic sectional view of the anode 2 along the section line AA.

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.

1 shows a schematic representation of a battery cell 2 , The battery cell 2 includes a housing 3 , which is prismatic, in the present cuboid, is formed. The housing 3 In the present case, it is designed to be electrically conductive and, for example, made of aluminum.

The battery cell 2 includes a negative terminal 11 and a positive terminal 12 , About the terminals 11 . 12 can one from the battery cell 2 provided voltage can be tapped. Furthermore, the battery cell 2 over the terminals 11 . 12 also be loaded.

Inside the case 3 the battery cell 2 is an electrode unit 10 arranged, which is designed as an electrode winding or as an electrode stack. The electrode unit 10 has two electrodes, namely an anode 21 and a cathode 22 , on. The anode 21 and the cathode 22 are each carried out like a foil and by a separator 18 separated from each other. The separator 18 is ionic conductive, so permeable to lithium ions.

The anode 21 the battery cell 2 includes an anodic active material 41 , which is designed like a film. The anode 21 further includes a current collector 31 , which is also formed like a foil and electrically conductive. The anodic active material 41 is present on both sides of the foil-like current conductor 31 the anode 21 applied. The current collector 31 the anode 21 is electric with the negative terminal 11 the battery cell 2 connected.

The cathode 22 the battery cell 2 comprises a cathodic active material 42 , which is designed like a film. The cathode 22 further includes a current collector 32 , which is also formed like a foil and electrically conductive. The cathodic active material 42 is present on both sides of the current collector 32 the cathode 22 arranged and connected to this. The current collector 32 the cathode 22 is electric with the positive terminal 12 the battery cell 2 connected.

2 shows a schematic sectional view of the anode 21 , The current collector 31 the anode 21 is presently designed as an expanded metal of copper. The current collector 31 the anode 21 but may for example be formed as a fabric made of copper. Likewise, the current collector 31 the anode 21 Also include sintered copper chips and copper fibers. Furthermore, the current collector 31 the anode 21 be formed as a fabric of carbon fibers.

The current collector 31 the anode 21 is thus porous and has pores. The pores of the current collector 31 the anode 21 are largely with a filler 33 filled. In the filler 33 in the pores of the current conductor 31 the anode 21 this is lithium.

The current collector 31 the anode 21 is bilateral with the anodic active material 41 coated. In the anodic active material 41 pointing to the current collector 31 the anode 21 is applied, it is also lithium.

From the current collector 31 the anode 21 protrudes a contact flag 35 gone, which is integral with the current collector 31 the anode 21 is trained. The contact flag 35 the anode 21 is thus also porous and has pores. The contact flag 35 the anode 21 is not with the anodic active material 41 coated, so it is free of anodic active material 41 , Also, the pores are the contact lug 35 the anode 21 not with the filler 33 filled, so are free of filler 33 ,

With the contact flag 35 of the current conductor 31 the anode 21 is a collector 51 electrically connected. Present is the collector 51 to the contact flag 35 of the current conductor 31 the anode 21 welded. The collector 51 serves for the electrical connection of the current conductor 31 the anode 21 with the negative terminal 11 the battery cell 2 , The collector 51 is made of solid copper, for example.

3 shows a schematic sectional view of the anode 21 out 2 along the section line AA. The of the current collector 31 the anode 21 away contact flag 35 is not with the filler 33 filled, so it is free of filling material 33 , The to the contact flag 35 the anode 21 welded collector 51 is not shown here.

The designed as an expanded metal of copper current conductor 31 the anode 21 has pores in the form of mesh, which with the filler material 33 are filled. The meshes are surrounded by webs of expanded metal. The web width is chosen so that less than 30% of the area and less than 30% of the volume of the current conductor 31 the anode 21 of copper is taken. Preferably, less than 20% of the area and volume of copper is occupied, more preferably less than 10% of the area and volume of copper is occupied.

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.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• DE 102013224294 A1 [0007]
• CN 103794800 [0008]
• US 2015/0037689 A1 [0009]

Claims (14)

Anode ( 21 ) for a battery cell ( 2 ), comprising a current collector ( 31 ) and an anodic active material ( 41 ), which contains lithium and on the current conductor ( 31 ), characterized in that a contact lug ( 35 ) of the current conductor ( 31 ) free of anodic active material ( 41 ). Anode ( 21 ) according to claim 1, characterized in that the current conductor ( 31 ) is porous and has pores which at least substantially with a filler ( 33 ), which contains lithium, and that the pores of the contact lug ( 35 ) at least substantially free of filling material ( 33 ) are. Anode ( 21 ) according to claim 2, characterized in that the current conductor ( 31 ) is formed as an expanded metal of copper having a thickness of less than 25 microns. Anode ( 21 ) according to claim 3, characterized in that the expanded metal has a mesh size of less than 1 mm. Anode ( 21 ) according to claim 2, characterized in that the current conductor ( 31 ) is formed as a fabric of carbon fibers having a thickness of less than 30 microns. Anode ( 21 ) according to claim 5, characterized in that the carbon fibers of the fabric have a thickness between 1/2 and 1/10 of the thickness of the fabric. Anode ( 21 ) according to claim 1, characterized in that the current conductor ( 31 ) is formed as a solid sheet of copper, which has a thickness of less than 10 microns. Method for producing an anode ( 21 ), where - a current conductor ( 31 ), which is porous and has pores, is coated on a first side with a first foil which contains lithium, - the pores of the current conductor ( 31 ) are at least largely filled with lithium, and - the current conductor ( 31 ) is coated on a second side with a second film containing lithium. Method according to claim 8, wherein the current conductor ( 31 ) is calendered with the first film such that the pores of the current conductor ( 31 ) are at least substantially filled with lithium from the first film. Method according to claim 8, wherein the pores of the current conductor ( 31 ) are at least largely filled with lithium galvanically and / or electrochemically. Method according to one of claims 8 to 10, wherein a contact lug ( 35 ) of the current conductor ( 31 ) remains free of lithium during the coating, and that the pores of the contact lug ( 35 ) during calendering and during the galvanic and / or electrochemical filling of the pores of the current conductor ( 31 ) remain at least substantially free of lithium. Method according to one of claims 8 to 11, wherein the first film on a current conductor ( 31 ) is provided with a first polymer film on the opposite side, and the second film on a current collector ( 31 ) is provided with a second polymer film, wherein the first polymer film and the second polymer film after the coating of the current conductor ( 31 ) are removed. Battery cell ( 2 ) comprising at least one anode ( 21 ) according to one of claims 1 to 7. Use of the battery cell ( 2 ) according to claim 13 in an electric vehicle (EV), in a hybrid vehicle (HEV), in a plug-in hybrid vehicle (PHEV), in an electric bicycle or in a portable device, in particular in a mobile phone, in a tablet, in a laptop or in a power tool.

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