Anode and alkali metal secondary battery

Abstract

An anode (1) for an electrochemical system, in particular an alkali metal secondary battery, comprises a current collector (2) and a nucleation layer (3) located on the current collector (2). Located on the nucleation layer (3) is an artificial SEI layer (4) having at least one ta-C layer containing at least one doping element selected from the group of doping elements comprising hydrogen, silicon, nitrogen, oxygen, silver, tin, zinc, antimony, lead, gold, platinum, bismuth, magnesium, potassium, sodium, calcium, nickel, aluminum, gallium, indium, boron, germanium, tellurium, ruthenium and osmium, the total content of doping elements being at least 0.1 atomic % and not more than 20 atomic %.

Description

[0001] Anode and alkali metal secondary battery

[0002] The invention relates to an anode suitable for use in an electrochemical system. The invention further relates to an alkali metal secondary battery.

[0003] German patent DE 102018218561 A1 discloses a composite electrode designed for a solid-state electrochemical cell and characterized by reduced interfacial resistance. The electrode according to DE 102018218561 A1 comprises a current collector layer, an active material layer, and a nucleation material layer, the latter being located between the current collector layer and the active material layer. Both the active material layer and the nucleation material layer contain lithium.

[0004] From EP 3869584 A1, a solid-state secondary battery is known which, in addition to a cathode layer and a solid electrolyte layer, has an anode layer comprising an anode current collector and two different anode active material layers. Each of the latter two layers contains a carbon-containing anode active material.

[0005] An anode electrode described in EP 2978052 A1 has a porous conductive layer comprising a conduction charging layer and a current collector layer, each of these two layers having pores. Furthermore, the anode electrode according to EP 2978052 A1 comprises a lithium metal layer arranged adjacent to the porous conductive layer.

[0006] US Patent 2021 / 0066758 A1 relates to a solid-state battery comprising an anode layer containing at least one of the following components: amorphous carbon, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, or zinc. In cases where amorphous carbon, which may be in the form of carbon black or acetylene black, is used as the anode active material in combination with one of the aforementioned metals, this material, according to the teaching of US Patent 2021 / 0066758 A1, has a particle size of less than 4 pm, with the particle diameter being less than 1 pm.

[0007] The invention is based on the objective of providing an anode for an electrochemical system, in particular a secondary battery, which is further developed compared to the aforementioned prior art and is characterized by operating properties that remain as constant as possible over the long term.

[0008] This problem is solved according to the invention by an anode having the features of claim 1. According to claim 9, the anode is particularly suitable for use in an alkali metal secondary battery.

[0009] The anode intended for use in an electrochemical system, in particular a secondary battery, has a current collector, a nucleation layer located on the current collector, and an artificial SEI layer (SEI = Solid Electrolyte Interphase) located on the nucleation layer, which is formed as an amorphous carbon layer.

[0010] The invention is based on the premise that lithium-metal anodes can form dendrites during charging and discharging cycles, which negatively impact battery lifespan. Furthermore, charging and discharging processes can lead to volume changes, which represent a mechanical stress on the anode and also tend to shorten the battery's lifespan. In this context, lithium-metal anodes are understood to include both anodes that already contain metallic lithium in their production state and anodes that are initially free of metallic lithium, with lithium being added only during conditioning or operation.

[0011] In general, when working with electrochemical systems containing lithium, it is important to consider that lithium is a reactive metal. Therefore, particular precautions must be taken against overheating and short circuits. Reactions of metallic lithium with an electrolyte can lead to the undesirable formation of a SEI layer. Uneven lithium deposition on the anode can play a role in this.

[0012] Taking into account the aforementioned and further considerations, the solution as described in the application includes, among other things, the application of a nucleation layer to a current collector. The nucleation layer has the particular task of homogenizing the lithium deposition, which significantly contributes to increasing the lifetime of the electrochemical system.

[0013] The nucleation layer can, for example, comprise at least one element selected from the group containing silver, tin, zinc, antimony, lead, gold, platinum, bismuth, magnesium, calcium, potassium, sodium, nickel, aluminum, gallium, indium, boron, germanium, tellurium, silicon, ruthenium, and osmium. The nucleation layer can be a layer applied across the entire surface, with a thickness ranging, for example, from 1 nm to 0.5 pm. Alternatively, the nucleation layer can exist in the form of atomic islands, i.e., island-shaped clusters of elements.

[0014] Regardless of the shape and composition of the nucleation layer, the artificial SEI layer, that is, an artificial layer made of a solid-electrolyte interphase, can be in particular a ta-C layer, that is, a tetrahedral amorphous carbon layer with a sp 3-The proportion of carbon-carbon bonds exceeding 50% must be formed. Optionally, the artificial SEI layer contains a proportion of aC, that is, amorphous carbon with predominantly sp³ carbon. 2 -hybridized bonds. A multilayered structure can also exist, consisting of alternating ta-C and aC layers. The total thickness of the artificial SEI layer ranges from 5 nm to 1 pm in various configurations.

[0015] Possible dopants within the artificial SEI layer, which can be present individually or in any combination, include hydrogen, silicon, nitrogen, oxygen, silver, tin, zinc, antimony, lead, gold, platinum, bismuth, magnesium, potassium, sodium, calcium, nickel, aluminum, gallium, indium, boron, germanium, tellurium, ruthenium, and osmium. The total dopant content in the artificial SEI layer ranges from 0.1% to 20%, expressed as the proportion of atoms.

[0016] The current collector can, for example, incorporate one or more of the materials selected from the group containing copper, aluminum, nickel, stainless steel, and conductive polymers. A conductive polymer can be present, for instance, as a solid, mechanically robust component or as a conductive polymer film mounted on a support element. In various configurations, the current collector can be constructed from a composite material made of the aforementioned substances. In other cases, the current collector may optionally feature passivation.

[0017] According to a further possible embodiment, an intermediate layer exists between the nucleation layer and the SEI layer, which comprises at least one element of the nucleation layer and at least one element of the SEI layer. Regardless of the presence of such an intermediate layer, the anode can be configured, for example, as a lithium metal anode or a sodium metal anode. Several embodiments of the invention are explained in more detail below with reference to a drawing. This drawing shows, in each case, a schematic sectional view:

[0018] Fig. 1 shows a first embodiment of an anode for an electrochemical system, comprising a current collector, a nucleation layer, and an artificial SEI layer.

[0019] Fig. 2 shows an anode in which a nucleation layer is formed by islands of atoms,

[0020] Fig. 3 shows an anode with an intermediate layer arranged between a nucleation layer and an SEI layer.

[0021] Fig. 4 shows an anode with a current collector comprising an electrically conductive polymer film,

[0022] Fig. 5 shows an anode with a current collector having passivation.

[0023] Unless otherwise stated, the following explanations apply to all embodiments. Corresponding or essentially equivalent parts are marked with the same reference numerals in all figures.

[0024] An anode, designated by reference numeral 1, is used in a secondary battery, for example, a traction battery of an electric vehicle. The battery, which comprises multiple anodes 1, is an alkali metal secondary battery. The anode 1 has a layered structure and includes a current collector 2, a nucleation layer 3, and an artificial SEI layer 4. In the embodiment shown in Figure 1, the aforementioned layers 2, 3, and 4 are arranged in a planar fashion. In the embodiment shown in Figure 1, as well as in the embodiments shown in Figures 2, 3, and 5, the current collector 2 comprises copper, aluminum, nickel, and / or stainless steel.

[0025] The nucleation layer 3 in each anode 1, according to one of Figures 1 to 5, contains silver, tin, zinc, antimony, lead, gold, platinum, bismuth, magnesium, calcium, potassium, sodium, nickel, aluminum, gallium, indium, boron, germanium, tellurium, silicon, ruthenium and / or osmium. The thickness of the nucleation layer 3 is at least 1 nm and at most 500 nm in the cases of Figures 1, 3, 4, and 5.

[0026] The artificial SEI layer 4 (solid electrolyte interphase) is composed of ta-C, that is, tetrahedral amorphous carbon. In each of the embodiments visualized in Figures 1 to 5, the amorphous carbon layer 4 optionally contains one or more of the following dopants: hydrogen, silicon, nitrogen, oxygen, silver, tin, zinc, antimony, lead, gold, platinum, bismuth, magnesium, potassium, sodium, calcium, nickel, aluminum, gallium, indium, boron, germanium, tellurium, ruthenium, and osmium. The thickness of the SEI layer 4 ranges from 5 nm to 1 pm. The total dopant content in the SEI layer 4 does not exceed 20 atomic percent.

[0027] In contrast to the embodiment shown in Figure 1, in the embodiment shown in Figure 2 the nucleation layer 3 is in the form of individual atomic islands 9, which represent nucleation seeds. The atomic islands 9 can be placed on the surface of the current collector 2 in a defined arrangement or in a stochastic distribution. In both cases, as shown in Figure 2, contacts can exist between the SEI layer 4 and the current collector 2. In the embodiment shown in Figure 3, the nucleation layer 3 is separated from the artificial SEI layer 4 by an intermediate layer 5. The intermediate layer 5 contains at least one element that is also found in the nucleation layer 3, as well as at least one element that is also a component of the SEI layer 4.

[0028] In the case of Figure 4, the electrically conductive properties of the current collector 2 are provided by a polymer film 7, which is located on a support element 6. The support element 6 can, in particular, be made of an electrically non-conductive plastic.

[0029] The embodiment shown in Figure 5 differs from the embodiment shown in Figure 1 in that a passivation layer 8 is located on the current collector 2. The passivation layer 8 represents a protective layer which is located on the electrically conductive base material of the current collector 2 without negatively affecting its electrical properties to any significant extent.

[0030] The features of anodes 1 outlined in Figures 1 to 5 can be combined in various ways within one and the same anode 1. For example, an anode 1 can be produced in which the current collector 2 is passivated and the nucleation layer 3 is present in the form of atomic islands 9. Likewise, in an anode 1 in which the current collector 2 is passivated and / or the nucleation layer 3 is formed from individual atomic islands 9, an intermediate layer 5 can be formed between the nucleation layer 3 and the artificial SEI layer 4.

[0031] It is also possible to first deposit atomic islands 9 as a nucleation layer 3 on an electrically conductive polymer film 7, which is part of the current collector 2. Despite the non-complete surface area of ​​the nucleation layer 3, an intermediate layer 5, which is also not necessarily complete, can form between the nucleation layer 3 and the artificial SEI layer 4 in such a case. Partial contact between the intermediate layer 5 and the current collector 2 is possible. (List of reference symbols)

[0032] anode

[0033] power collector

[0034] Nucleation layer

[0035] artificial SEI layer, amorphous carbon layer, ta-C layer interlayer

[0036] Support element

[0037] Polymer film

[0038] passivation layer

[0039] Atomic island

Claims

Patent claims 1. Anode (1) for an electrochemical system comprising a current collector (2), a nucleation layer (3) located on the current collector (2), and an artificial SEI layer (4) located on the nucleation layer (3), which has at least one ta-C layer containing at least one dopant element selected from the group of dopant elements comprising hydrogen, silicon, nitrogen, oxygen, silver, tin, zinc, antimony, lead, gold, platinum, bismuth, magnesium, potassium, sodium, calcium, nickel, aluminum, gallium, indium, boron, germanium, tellurium, ruthenium, osmium, wherein the total content of dopant elements is at least 0.1 atomic % and not more than 20 atomic %.

2. Anode (1 ) according to claim 1 , characterized in that the thickness of the artificial SEI layer (4) is at least 5 nm and at most 1 pm.

3. Anode (1) according to claim 1 or 2, characterized in that the nucleation layer (3) contains at least one element selected from the group of elements comprising silver, tin, zinc, antimony, lead, gold, platinum, bismuth, magnesium, calcium, potassium, sodium, nickel, aluminium, gallium, indium, boron, germanium, tellurium, silicon, ruthenium and osmium.

4. Anode (1) according to claim 3, characterized in that the nucleation layer (3) has a layer thickness of at least 1 nm and at most 500 nm.

5. Anode (1) according to claim 4, characterized in that the nucleation layer (3) is in the form of atom islands (9).

6. Anode (1) according to one of claims 1 to 5, characterized in that the current collector (2) contains at least one of the materials which consists of selected from a group of materials that includes copper, aluminium, nickel, stainless steel and conductive polymers.

7. Anode (1) according to one of claims 1 to 6, characterized in that the SEI layer (4) is multilayered, namely alternating with ta-C layers and aC layers.

8. Anode (1) according to one of claims 1 to 7, characterized by an intermediate layer (5) located between the nucleation layer (3) and the SEI layer (4), which has at least one element of the nucleation layer (3) and at least one element of the SEI layer (4).

9. Alkali metal secondary battery comprising an anode (1) according to claim 1.

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