Abstract
A layer combination for an electrode can be used in rechargeable electrochemical cells. The rechargeable electrochemical cells are in the form of lithium batteries, e.g. a lithium-sulfur battery or a lithium-oxygen battery. The layer combination includes at least one superhydrophobic, nanostructured protective layer which repels polar substances.
Claims
1. A layer composite for an electrode of a rechargeable electrochemical element, the layer composite comprising: at least one superhydrophobic, nanostructured protective layer configured to repel polar substances.
2. The layer composite as claimed in claim 1, wherein: the superhydrophobic, nanostructured protective layer is made of nanostructured polypropylene, nanostructured polyethylene, nanostructured PE-PP copolymers or further polyolefins.
3. The layer composite as claimed in claim 1, wherein: the superhydrophobic, nanostructured protective layer is made of nanostructured silicon or of a polymer.
4. The layer composite as claimed in claim 1, wherein: the superhydrophobic, nanostructured protective layer within the layer composite is applied directly to a lithium layer or to a second electrode.
5. Layer composite as claimed in claim 1, wherein: the superhydrophobic, nanostructured protective layer within the layer composite is covered by at least one second polymer layer and/or at least one second ceramic layer.
6. The layer composite as claimed in claim 1, wherein: the superhydrophobic, nanostructured protective layer is applied to a lithium layer with immediate insertion of a second polymer layer and/or a second ceramic layer.
7. The layer composite as claimed in claim 1, further comprising: at least one separator layer between a lithium layer and a second electrode.
8. A process for producing a layer composite, comprising: applying a superhydrophobic, nanostructured protective layer to a support substrate, wherein the superhydrophobic protective layer is produced by coating by: a spray mist and subsequent drying with crosslinking or polymerization, application using a doctor blade of a thin layer and subsequent drying, or vapor deposition or vacuum vapor deposition and subsequent crosslinking or polymerization.
9. A process for producing a layer composite comprising: applying a superhydrophobic, nanostructured protective layer of nanostructured silicon to a support substrate, wherein the superhydrophobic, nanostructured protective layer is applied by sputtering, aerosol deposition or plasma enhanced chemical vapor deposition.
10. The layer composite as claimed in claim 1, wherein the layer composite is configured to be used in lithium batteries in traction batteries of hybrid vehicles, plug-in hybrid vehicles, electric vehicles or in electric tools, garden tools, computers, notebooks, PDAs, smartphones or cell telephones.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention is illustrated in detail below with the aid of the drawings:
[0025] In the drawings:
[0026] FIG. 1 schematically shows various contact angles of water droplets which these have in relation to a hydrophilic, a hydrophobic and a superhydrophobic support substrate,
[0027] FIG. 2 shows a first variant of a layer composite containing a superhydrophobic, nanostructured protective layer,
[0028] FIG. 3 shows a further, second variant of the layer composite,
[0029] FIG. 4 shows a further, third variant of the layer composite,
[0030] FIG. 5 shows a fourth variant of the layer composite containing the superhydrophobic, nanostructured protective layer,
[0031] FIG. 6 schematically shows a production process for the superhydrophobic, nanostructured protective layer,
[0032] FIG. 7 shows a further, fifth layer composite comprising a second electrode and a first electrode and
[0033] FIG. 8 shows a further variant of a layer composite having a superhydrophobic, nanostructured protective layer embedded between two separator layers between a second electrode and a first electrode.
[0034] In the figures, identical or similar components are denoted by the same reference numerals. Repeated description of these components will be omitted in individual cases.
[0035] FIG. 1 schematically illustrates what is meant by the term superhydrophobic in the present context. It can be seen from the depiction in FIG. 1 that the measure of hydrophobicity, i.e. repulsion of polar materials, is determined by means of a contact angle. The more hydrophobic a surface or a surface substrate, the higher the contact angle. In the case of a hydrophilic layer 12 as per the depiction in FIG. 1, a water droplet 10 spreads out to form a spot, a pool or a puddle, characterized by a contact angle of <90°. Such a surface is described as hydrophilic. On the other hand, a hydrophobic layer 14 is characterized by a contact angle of >90°. It can be seen from the depiction in FIG. 1 that the water droplet 10 experiences only minimal deformation. Superhydrophobic materials, on the other hand, are characterized by a contact angle of >160°, i.e. the water droplet 10 remains virtually undeformed on contact with a superhydrophobic layer 16.
EMBODIMENTS OF THE INVENTION
[0036] The depiction in FIG. 2 shows a first layer composite 30, which can also be referred to as first composite. In the first layer composite 30 as depicted in FIG. 2, it is possible to see, in descending order, firstly a first polymer layer 32 and adjoining first ceramic layer 34, finally a further, second polymer layer 36 and also a further, second ceramic layer 38. Between a lithium layer 42 and the second ceramic layer 38, there is a superhydrophobic, nanostructured protective layer 40 in the first layer composite 30 as depicted in FIG. 2. This protective layer 40 can, for example, be made of nanostructured polypropylene (PP), other polyolefins or polymers. Furthermore, it is possible to make the superhydrophobic, nanostructured protective layer 40 of nanostructured silicon, with nanostructured silicon having good lithium ion conduction properties. According to the depiction in FIG. 2, the superhydrophobic, nanostructured protective layer 40 has been applied directly to the lithium layer 42. In FIG. 2, a first electrode is denoted by the position 62. The lithium layer 42 covered by the superhydrophobic, nanostructured protective layer 40 represents the first electrode 62 which, in the first layer composite 30 as per the depiction in FIG. 2, is located above a power outlet lead 44 which is preferably made of copper. The further layers 32, 34, 36 and 38 depicted in the layer composite as per FIG. 2 serve to conduct lithium ions.
[0037] FIG. 3 shows a modification of the first layer composite, as is depicted in FIG. 2.
[0038] A second layer composite 46 depicted in FIG. 3 has, in contrast to the first layer composite 30 as shown in FIG. 2, only the first ceramic layer 34. Unlike the first layer composite 30 depicted in FIG. 2, the second ceramic layer 38 is absent in the second layer composite 46 as per FIG. 3. In the second layer composite 46 as depicted in FIG. 3, too, the first electrode 62 is formed by the lithium layer 42 and the superhydrophobic, nanostructured protective layer 40 which covers this. The second layer composite 46 as depicted in FIG. 3, too, comprises the power outlet lead 44 which is preferably made of copper.
[0039] FIG. 4 finally shows a further, third variant of the layer of composite.
[0040] FIG. 4 shows a third layer composite 48 which corresponds in terms of the number of layers to the first layer composite 30 as depicted in FIG. 2, but has a different order in respect of the layer sequence. Unlike the first layer composite 30 as depicted in FIG. 2, a second ceramic layer 38 is present between the superhydrophobic, nanostructured protective layer 40 and the lithium layer 42 in the third layer 48 as depicted in FIG. 4. In this case, the first electrode is formed by the lithium layer 42, the superhydrophobic, nanostructured protective layer 40 and the second ceramic layer 38 accommodated between these. The sequence of the first polymer layer 32, the first ceramic layer 34 and the second polymer layer 36 is identical to the layer sequence within the first layer composite 30 as depicted in FIG. 2.
[0041] FIG. 5 shows a further, fourth possible embodiment of a layer composite 50 comprising a superhydrophobic, nanostructured protective layer 40. In the fourth layer composite 50 as depicted in FIG. 5, too, there is a further layer, in this case the polymer layer 36, between the superhydrophobic, nanostructured protective layer 40 and the lithium layer 42, in a manner comparable to the third layer of composite 48 as per FIG. 4. This means that the first electrode 62 within the fourth layer of composite 50 as per FIG. 5 is formed by the lithium layer 42, the second polymer layer 36 and the superhydrophobic, nanostructured protective layer 40. Above this, there is, in the reverse order compared to the third layer composite 48 as per FIG. 4, the first ceramic layer 34, the first polymer layer 32 and the second ceramic layer 38.
[0042] FIG. 6 schematically shows an application method for producing the superhydrophobic, nanostructured protective layer 40.
[0043] FIG. 6 shows that a spray mist 52 can be formed from a nanostructured polypropylene or from nanostructured silicon. The spray mist 52 is applied by means of a movable spray head 54 to a support substrate 56 which has a sufficient area 58. The spray head 54 can be moved relative to the support substrate 56 in the spray direction 60, so that in the case of uniform movement and application of the spray mist 52 to the support substrate 56, a thin film of the superhydrophobic, nanostructured protective layer 40 is produced. Application of the coating via the spray head 54 to the support substrate 56 is followed by drying, during which crosslinking or polymerization of the superhydrophobic, nanostructured protective layer 40 occurs.
[0044] Although not represented in drawing, the superhydrophobic, nanostructured protective layer 40 can also be produced by applying a thin layer by knife-coating, and by a subsequent drying operation. A further option is to produce the superhydrophobic, nanostructured protective layer 40 by evaporation or vacuum evaporation. The drying operation may then optionally be accompanied by crosslinking and/or polymerization.
[0045] If nanostructured silicon is selected as material of which the superhydrophobic, nanostructured protective layer 40 is made, use can be made of sputtering as application method. In addition, there is the possibility of applying nanostructured silicon by means of aerosol deposition to the support substrate 56. As an alternative to this method, there is the possibility of applying nanostructured silicon to the support substrate 56 by plasma enhanced chemical vapor deposition.
[0046] FIG. 7 depicts a further possible embodiment of a layer composite 70 having at least one superhydrophobic, nanostructured protective layer 40.
[0047] FIG. 7 shows the fifth layer of composite 70, i.e. a fifth composite which comprises the power outlet lead 44, the lithium layer 42 and a first separator layer 72, preferably a polymeric protective layer. In this illustrative embodiment, the superhydrophobic, nanostructured protective layer 40 is located between this first separator layer 72 and a second electrode 74. In the illustrated embodiment shown in FIG. 7, the superhydrophobic, nanostructured protective layer 40 has been applied directly to the second electrode 74 within the fifth layer of composite 70. The first separator layer 72 is located between the lithium layer 42 representing the first electrode 62. Instead of the first separator layer 72, it is also possible for a plurality of layers of ceramic layers or an alternating sequence of a plurality of polymer layers and ceramic layers to be arranged alternately within the fifth layer of composite 70 as depicted in FIG. 7.
[0048] FIG. 8 shows a further possible embodiment of a layer of composite 76 similar to the fifth layer of composite 70 depicted in FIG. 7.
[0049] FIG. 8 shows the sixth layer of composite 76, i.e. a sixth composite in which the superhydrophobic, nanostructured protective layer 40 is embedded between the first separator layer 72, preferably a polymer, and a second separator layer 78, likewise preferably a polymer. In this case, the superhydrophobic, nanostructured protective layer 40 is not arranged directly on the second electrode 74. The two separator layers 72, 78 are located between the lithium layer 42 representing the first electrode 62 and the second electrode 74. Furthermore, further layers, for example polymer layers and ceramic layers in an alternating sequence, can be located between the lithium layer 42 representing the first electrode 62 and the superhydrophobic, nanostructured protective layer 40.
[0050] The layer of composites 30, 46, 48, 50, 70 and 76 as per the above illustrative embodiments of FIGS. 2 to 5, 7 and 8 including at least one superhydrophobic, nanostructured protective layer 40 contributes significantly to increasing the life, the cycling stability and the safety of lithium batteries, in particular lithium-sulfur battery systems and lithium-oxygen battery systems. In addition, it is also possible to use such layer of composites 30, 46, 48, 50, 70 and 76 in the case of first electrode 62 composed of a lithium alloy. The use is also possible independently of the cathode chemistry or cathode structure.
[0051] In addition, the solution proposed according to the invention contributes to increasing the safety of lithium anodes in lithium batteries, since in the case of thermal stress, the reaction of liquid electrolyte with metallic lithium is prevented or at least significantly reduced.
[0052] The solution proposed according to the invention is used in lithium batteries for electric tools, garden tools, computers, notebooks, PDAs, smartphones and cell telephones. In particular, the solution proposed according to the invention can be used in traction batteries for hybrid vehicles, plug-in hybrid vehicles and in electric vehicles. Owing to the particularly demanding requirements in respect of service life in the automobile sector, the solution proposed according to the invention is of particular interest there.
[0053] The invention is not limited to the examples described here and the aspects emphasized therein. Rather, many modifications of the kind that a person skilled in the art would make as a matter of routine are possible within the scope of the claims.
