Dispersion electrolyte for particle-containing tin alloy layers

Abstract

The invention relates to, among others, a dispersion electrolyte for galvanically depositing particle-containing tin alloy layers. The dispersion electrolyte comprises 2 to 100 g / L of tin ions, 1 to 100 g / L of ions of a second alloy element, selected from copper, silver, bismuth, nickel, cobalt, cadmium, zinc, manganese, and combinations thereof, 1 to 200 g / L of at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof; at least one dispersant selected from anionic dispersants, non-anionic dispersants, and combinations thereof; and water. The pH value is 7 or lower. By virtue of the dispersion electrolyte, a particle-containing tin alloy layer can be galvanically deposited onto a metal or metallized substrate.

Description

[0001]1 264 525 n / n27 Dispersion electrolyte for particle-containing tin alloy layers Description Technical field of the invention The present invention relates to a dispersion electrolyte for the electrodeposition of particle-containing tin alloy layers, a method for the electrodeposition of a substrate with a particle-containing tin alloy layer, a coated substrate with a particle-containing tin alloy layer and an electrochemical cell comprising the coated substrate. Technical background For many electronic applications, it is desirable to partially or completely replace precious metals with more cost-effective base metals. In addition to good electrical properties, resistance to corrosion is also desirable in order to obtain long-lasting and thus sustainable electronic components, such as a contact or an electrode.One way to improve corrosion resistance is through cost-effective coatings with tin or tin alloys, which can be used to electroplate electronic components. Tin-nickel alloys in particular, which are typically deposited electroplatingly as SnNi, i.e., approximately 65 wt% tin and 35 wt% nickel, exhibit good corrosion resistance to acids and are therefore widely used. The corrosion resistance of tin-nickel alloys is better than that of pure tin coatings. Titanium and precious metals are also used as corrosion-resistant materials, although these are considerably more expensive than, for example, stainless steel or steel substrates with a corrosion-protection layer made of a tin alloy. However, tin and tin alloys can have disadvantageous electrical properties compared to precious metals.These can manifest themselves, for example, in increased contact resistance with other metals. Furthermore, higher overpotentials can be observed during electrochemical reactions in aqueous media, which are often caused by kinetic inhibition of a reaction. It would therefore be desirable to develop coatings with cost-effective materials that ensure good corrosion protection while simultaneously improving electrical properties, particularly reducing overpotentials for electrochemical reactions in aqueous media. Furthermore, compositions and processes are needed that allow these coatings to be produced economically.Summary of the Invention One object of the present invention is therefore to provide an electrolyte for the electrodeposition of tin alloy layers that are capable of reducing an overvoltage for electrochemical reactions and exhibit good corrosion resistance. Further objects are to provide a method for coating substrates with such a tin alloy layer, which uses the electrolyte, the coated substrate, and applications thereof. These objects are achieved by the dispersion electrolyte for the electrodeposition of particle-containing tin alloy layers, the method for electrodepositing a substrate with a particle-containing tin alloy layer, which uses the dispersion electrolyte, the coated substrate, and an electrochemical cell comprising the coated substrate, according to the independent claims.Optional and preferred embodiments are specified below and in the dependent claims. Brief Description of the Figures: Fig. 1: A scanning electron microscope image of the particle-containing layer of Example 1. Fig. 2: A scanning electron microscope image of the particle-containing layer of Example 2. Detailed Description of the Invention: The present invention provides a dispersion electrolyte for the electrodeposition of particle-containing tin alloy layers.The dispersed electrolyte comprises: - tin ions in a concentration of 2 to 100 g / L; - ions of a second alloying element selected from copper, silver, bismuth, nickel, cobalt, cadmium, zinc, manganese, and combinations thereof, in a concentration of 1 to 100 g / L; - at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, in a total concentration of 1 to 200 g / L; - at least one dispersant selected from anionic dispersants, nonionic dispersants, and combinations thereof; and - water; wherein the dispersed electrolyte has a pH of 7 or less. The dispersed electrolyte is also referred to below as "electrolyte" for short.The inventors have surprisingly found that with the dispersion electrolyte according to the invention, it is possible to electrodeposit the uncharged particles together with a tin alloy layer, thus forming a particle-containing tin alloy layer. The deposited tin alloy layer therefore contains, in addition to the tin alloy, particles of one or more inorganic piezoelectric materials and / or one or more electrically conductive ceramic materials. Using the dispersion electrolyte, the tin alloy described below can be produced using the process described below. In the process described below, in addition to tin, which can be regarded as the first alloying element, the second alloying element is also deposited during the electrodeposition. As explained in more detail below, further alloying elements can be contained in the deposited tin alloy.The dispersion electrolyte can therefore be used to form a secondary, ternary, or higher-dimensional alloy. The deposited tin alloy may contain unavoidable impurities. It was further surprisingly discovered that, compared to corresponding tin alloy layers without the particles, the overpotential for electrochemical reactions in aqueous media, even in aqueous acidic media, can be reduced using the particles made of an inorganic piezoelectric or electrically conductive ceramic material. Due to the lower overpotential, less current is required for the same electrochemical reaction, thus improving the reaction's economic efficiency. The electrolyte enables the particle-containing tin alloy layer to be galvanically deposited on a metallic or metallized substrate.The process described below can be used for this purpose, which enables deposition over broad temperature and current density ranges. During deposition, the particles are at least partially arranged on the surface of the particle-containing tin alloy layer, so that they form part of the surface. The particle-containing tin alloy layer is typically created as a final layer, i.e. as the outermost layer, on the substrate. Furthermore, it was surprisingly found that the particle-containing tin alloy layer, despite the particles, which are essentially foreign bodies in the tin alloy layer, exhibits good corrosion resistance in the acidic range and resistance in the alkaline range, comparable to the corrosion resistance of a corresponding tin alloy layer without particles. The second alloying element increases the corrosion resistance of the tin alloy compared to a corresponding tin layer.As mentioned at the beginning, tin-nickel alloys exhibit good corrosion resistance. The other second alloying elements, namely copper, silver, bismuth, cobalt, cadmium, zinc, and manganese, provide comparable corrosion resistance to nickel as the second alloying element, particularly good corrosion resistance at very low pH values. The deposited particle-containing tin alloy layer thus exhibits good corrosion resistance. The dispersion electrolyte according to the invention thus enables the formation of layers that both provide good protection against corrosion and reduce overpotential for electrochemical reactions at an interface, so that these advantageous properties can be realized simultaneously in a single layer.The particle-containing tin alloy layer can therefore advantageously be used as a protective layer, in particular as the outermost layer on a component, in particular an electronic component, for example a contact or an electrode. The dispersion electrolyte according to the invention comprises at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof. The particles can thus consist of one or more types of inorganic piezoelectric particles and / or one or more types of electrically conductive ceramic particles. The particles can be made of an inorganic piezoelectric material that is monocrystalline or polycrystalline. A piezoelectric effect can occur with non-centrosymmetric point groups (crystal groups). The unit cell of the material therefore has no inversion center.Consequently, cubic point groups with an inversion center, for example, do not exhibit piezoelectricity. If inorganic materials have both piezoelectric and non-piezoelectric modifications, only the piezoelectric modifications are counted as particles. For example, barium titanate (BaTiO3) can exist in a perovskite structure and in a cubic modification thereof. Since the cubic modification is not piezoelectric, it is not counted as a particle. Another example is boron nitride (BN). Since hexagonal boron nitride is piezoelectric, it can be used as a particle according to the invention. Cubic boron nitride is not piezoelectric and is therefore not counted as a particle. The particles can also be made of an electrically conductive ceramic material. Since these are electrically conductive, they do not exhibit piezoelectricity.Non-ceramic electrically conductive particles, such as carbon or metal particles, are not considered particles. The invention does not limit the use of inorganic piezoelectric particles and electrically conductive ceramic particles. Materials doped with foreign atoms can also be used as inorganic piezoelectric particles. The particles can be made of, for example, BN (hexagonal), AlN, ZnO, GaPO4, or M1. 2y MA 1-y [MB x Ti 1−x ]O3, M1 2y MA 1-y [MC x Zr 1−x ]O3, M1 2y MA 1-y [MD x Mn 1−x ]O3, M1 2y MA 1-y [ME x Hf 1−x ]O3, M1[MF x Nb 1−x ]O3, M1[MG x V 1−x ]O3, M1[MH x Ta 1−x]O3, TiN, TiC, TiB2, Ti2CN, B4C, WC and combinations thereof. The following applies to the general formulas: M1 is each independently at least one element selected from Li, Na and K, preferably Li; MA is each independently at least one element selected from Ca, Sr, Ba, Pb and La; MB is each independently selected from Zr, Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MC is selected from Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MD is selected from Hf, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; ME is selected from Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3; MF is selected from V, Ta and Mn; MG is selected from Ta and Mn; MH is Mn; x satisfies 0 ≤ x ≤ 1; and y satisfies 0 ≤ y ≤ 1. The particles are in particular made of BN (hexagonal), AlN, ZnO, GaPO4, Li 2y MA 1-y [MB x Ti 1−x ]O3, Li 2y MA 1-y [MC x Zr 1−x ]O3, Li 2y MA 1-y [MD x Mn 1−x ]O3, LiNbO3, LiVO3, LiMnO3, LiTaO3, TiN, TiC, TiB2, Ti2CN, B4C, WC, and combinations thereof. In the general formulas, the following applies: MA is independently at least one element selected from Ca, Sr, Ba, Pb, and La; MB is selected from Zr, Mn, and Mg. 1 / 3 Nb 2 / 3 ; MC is selected from Mn and Mg 1 / 3 Nb 2 / 3 ; MD is Mg 1 / 3 Nb 2 / 3; x each independently satisfies 0 ≤ x ≤ 1; and y each independently satisfies 0 ≤ y ≤ 1. Of the above-mentioned materials, TiN, TiC, TiB2, Ti2CN, B4C and WC are electrically conductive ceramic materials, and the rest are inorganic piezoelectric materials. According to a preferred embodiment, the particles are selected from inorganic piezoelectric particles. According to another preferred embodiment, the inorganic piezoelectric particles are selected from BN (hexagonal), AlN, ZnO, GaPO4, Li2[Zr x Ti 1−x ]O3, Li 2y MA 1-y [Zr x Ti 1−x ]O3, MA[Zr x Ti 1−x ]O3, Pb[Zr x Ti 1−x]O3, LaMnO3 and LiNbO3 and combinations thereof. The following applies to the general formulas: MA is in each case independently at least one element selected from Ca, Sr and Ba; x in each case independently satisfies 0 ≤ x ≤ 1; and y in each case independently satisfies 0 < y < 1. The particles are further preferably made of BN (hexagonal), AlN, BaTiO3, Li2ZrO3, Li2TiO3, CaTiO3, ZnO, LaMnO3, Pb[Zr x Ti 1−x]O3 (where x is in the range of 0 ≤ x ≤ 1), LiNbO3, GaPO4, and combinations thereof, and particularly preferably selected from BN (hexagonal), BaTiO3, CaTiO3, Li2ZrO3, and combinations thereof. The dispersion electrolyte contains the particles, selected from inorganic piezoelectric particles and / or electrically conductive ceramic particles, in a total concentration of 1 to 200 g / L. The dispersion electrolyte contains the particles in particular in a total concentration of 3 to 150 g / L, preferably 5 to 100 g / L, more preferably 8 to 80 g / L, even more preferably 15 to 60 g / L. At these concentrations, the dispersion electrolyte can be thoroughly mixed, and a suitable amount of particles can be deposited with the tin alloy layer to effectively reduce the overpotential for electrochemical reactions in aqueous media. As a rule, the particles should be smaller than the desired layer thickness of the particle-containing tin alloy layer.The particle size can be adjusted, for example, using common grinding and / or sieving processes, which can be used to separate out particles that are too coarse or too fine. Suitable particles are often also commercially available. For particles with an aspect ratio of less than 3.0, the average particle diameter is typically in the range of 20 nm to 20 µm, preferably 0.1 to 10 µm, more preferably 0.5 to 8 µm. The aspect ratio indicates the ratio of the largest diameter to the smallest diameter of a particle. For spherical particles, the aspect ratio is therefore 1. The aspect ratio of the particles can be determined microscopically by measuring 20 randomly selected particles. Depending on the size of the particles, a light microscope or an electron microscope with a reference can be used.If the particles have an aspect ratio of 3.0 or more, the average particle length is typically 0.1 to 90 µm, preferably 0.5 to 50 µm, more preferably 0.8 to 20 µm. Particles with such an aspect ratio are generally flat or elongated, for example needle-shaped or flake-shaped. The length refers to the largest diameter of a particle. The particle size can be determined using laser diffraction according to ISO 13320:2020, e.g. using a HELOS spectrometer (Helium-Neon Laser Optical System). The mean particle size is given as the D50 value. In a deposited layer, the average particle size can be determined from a top view or on a cross-section using a microscope or electron microscope. At least 100 randomly selected particles are considered to determine the average particle size.In principle, all common water-soluble tin salts, as well as salts of the second and third alloying elements, can be used for the dispersion electrolyte. The electrolyte also contains the corresponding anions of these salts. Suitable tin salts include tin sulfate, tin chloride, tin bromide, and tin acetate, especially tin sulfate and tin chloride. Examples of common nickel salts are nickel sulfamate, nickel sulfate, nickel chloride, nickel bromide, nickel acetate, especially nickel sulfamate, nickel sulfate, and nickel chloride. Other examples of suitable salts are copper sulfate, copper chloride, silver nitrate, cobalt chloride, cobalt sulfate, and bismuth chloride. All modifications of these salts, such as hydrates, can be used in the electrolyte. If a silver-containing alloy is to be formed, a halogen- and sulfide-free dispersion electrolyte is used to avoid the precipitation of poorly soluble silver salts.The dispersion electrolyte contains tin ions in a concentration of 2 to 100 g / L. The tin ions are present in the electrolyte in particular at a concentration of 5 to 80 g / L, preferably 10 to 70 g / L, more preferably 20 to 60 g / L. Furthermore, the dispersion electrolyte contains the ions of the second alloying element, which are present in the dispersion electrolyte in a concentration of 1 to 100 g / L. If there are several different second alloying elements, the concentration corresponds to the total concentration. The ions of the second alloying element are present in particular at a concentration of 2 to 80, preferably 5 to 70 g / L. The concentrations are selected such that the tin alloy layer has the desired tin content and the desired content of the second alloying element.The dispersion electrolyte contains, as stated above, ions of a second alloying element selected from copper, silver, bismuth, nickel, cobalt, cadmium, zinc, manganese, and combinations thereof. The second alloying element is preferably selected from copper, silver, bismuth, nickel, cobalt, and combinations thereof. According to a preferred embodiment, the second alloying element is nickel. During electrodeposition, a tin alloy containing tin and nickel is then formed. According to this embodiment, a particularly cost-effective coating with good corrosion resistance in the acidic, neutral, and alkaline ranges can be obtained. In strongly acidic media, i.e., aqueous media with a pH value of less than 2.5, such as sulfuric acid, a slow discharge of nickel from a tin-nickel alloy can occur, leading to a slow decomposition of the material.To improve resistance even at low pH values, the nickel content in the tin alloy can be reduced, i.e. nickel can be partially or completely replaced by other second or third alloying elements. According to a further preferred embodiment, the second alloying element is therefore selected from copper, silver, bismuth, cobalt and combinations thereof. Preferably, only one second alloying element is used. Particularly preferably, the second alloying element is copper, silver or bismuth. The dispersion electrolyte can contain ions of a third alloying element, which can be electrodeposited together with tin and the second alloying element. The third alloying element is different from tin and the second alloying element. It is typically selected from nickel, cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, tungsten and combinations thereof.The third alloying element is preferably selected from nickel, cobalt, antimony, copper, cadmium, bismuth, and combinations thereof. Preferably, only one third alloying element is used. If present, the ions of the third alloying element are typically present in the dispersion electrolyte at a concentration of up to 40 g / L. If several different third alloying elements are present, the concentration corresponds to the total concentration. The ions of the third alloying element are preferably present at a concentration of 1 to 20, more preferably 1 to 15 g / L. According to a preferred embodiment, nickel is the second alloying element, and the third alloying element is selected from cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, and tungsten. According to this embodiment, a tin-nickel alloy is deposited in which, to a certain extent, nickel is partially replaced by the third alloying element.As a result, the corrosion resistance to aqueous, strongly acidic media can be improved compared to a corresponding tin-nickel alloy without the third alloying element. In this embodiment, the third alloying element is preferably selected from cobalt, copper, and antimony. According to a further preferred embodiment, the second alloying element is cobalt and the third alloying element is selected from nickel, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, and tungsten. Good corrosion resistance in acidic media is obtained. In this embodiment, the third alloying element is preferably selected from nickel, antimony, and copper. According to a further preferred embodiment, the second alloying element is copper and the third alloying element is selected from nickel, cobalt, chromium, zinc, silver, gold, antimony, cadmium, bismuth, manganese, and tungsten. Good corrosion resistance in acidic media is obtained.Preferably, the third alloying element in this embodiment is selected from nickel, antimony, and cobalt. According to a further preferred embodiment, the second alloying element is silver, and the third alloying element is selected from nickel, cobalt, chromium, zinc, gold, antimony, copper, cadmium, bismuth, manganese, and tungsten. Good corrosion resistance in acidic conditions is achieved. Preferably, the third alloying element in this embodiment is selected from copper, antimony, and cadmium. According to a further preferred embodiment, the second alloying element is bismuth, and the third alloying element is selected from nickel, cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, manganese, and tungsten. Good corrosion resistance in acidic conditions is achieved. Preferably, the third alloying element in this embodiment is selected from copper, antimony, and nickel.According to these further preferred embodiments, a tin alloy can be electrodeposited using the dispersion electrolyte, which has particularly good corrosion resistance, in particular to aqueous, strongly acidic media. The dispersion electrolyte contains, in particular, the tin ions in a concentration of 5 to 80 g / L, preferably 10 to 70 g / L, more preferably 20 to 60 g / L, the ions of the second alloying element in a concentration of 2 to 80 g / L, preferably 5 to 70 g / L, and optionally the ions of the third alloying element in a concentration of 1 to 20 g / L, preferably 1 to 15 g / L. The electrolyte is storage-stable and can be operated economically at these concentrations, i.e., with appropriate deposition rates.The concentration of the tin ions, the ions of the second alloying element and, if present, the third alloying element are selected such that a tin alloy layer with the composition specified below or a preferred embodiment thereof is obtained. Since tin and the various second and third alloying elements are of varying noble and base metals, the composition of the alloy often does not reflect the ratio of the ions in the dispersion electrolyte. In general, a higher concentration of the ions of an element in the electrolyte also leads to increased incorporation of the element into the tin alloy and, conversely, a lower concentration leads to reduced incorporation of the element into the tin alloy. According to a further preferred embodiment, the dispersion electrolyte contains at least one further organic compound that is different from the dispersant.The additional organic compound can be decomposed during the electrodeposition of the tin alloy layer and thus serve as a carbon source for the tin alloy, thus leading to the incorporation of carbon into the tin alloy. Carbon can therefore be present in the tin alloy as a fourth alloying element. The additional organic compound can therefore be understood as a precursor compound of carbon and lead to an increased incorporation of carbon into the tin alloy. However, it is also possible that carbon is formed in another way, for example through the decomposition of the dispersant or other additives to the electrolyte, essentially as an impurity. The additional organic compound can typically be present in the dispersion electrolyte in a total concentration of up to 100 g / L, preferably up to 50 g / L.As further organic compounds, for example, conventional brighteners can be used, for example xanthates, carbamates, Turkey red oil, a ketone (for example benzalacetone), an aromatic aldehyde (for example naphthaldehyde). The further organic compound preferably comprises or consists of a xanthate, a carbamate, Turkey red oil, benzalacetone (4-phenylbutenone), naphthaldehyde and combinations thereof. More preferably, the further organic compound comprises or consists of benzalacetone and / or naphthaldehyde. The carbon formed from the organic compounds is present in the alloy in particular in nanoscale or atomic form, i.e. in the form of carbon structures with a size of up to 5 nm, in particular up to 2 nm, or as individual carbon atoms or groupings of several carbon atoms.Carbon forms an alloy component and can thus be distinguished from discrete particles, such as the electrically conductive particles made of a carbon material described below, which are not an alloy component. Detection can be achieved using the composition determination method specified below. Detection and size measurement can also be performed using transmission electron microscopy (TEM). Surprisingly, it was found that the incorporation of carbon into the tin alloy also leads to good corrosion resistance of the tin alloy layer. Therefore, the second and / or third alloying elements can be partially replaced with inexpensive carbon. Furthermore, the incorporation of carbon can lead to an increase in electrical conductivity.According to a further embodiment, the dispersion electrolyte comprises, as further particles, electrically conductive particles made of a carbon material, preferably graphite particles, in a total concentration of 1 to 100 g / L, preferably 2 to 50 g / L, more preferably 5 to 40 g / L. These particles can be used, for example, to improve the tribological properties of the particle-containing tin alloy layer or to reduce the contact resistance to metals. According to a further embodiment, the dispersion electrolyte contains no electrically conductive particles made of a carbon material and preferably no further particles other than the particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof. The further particles preferably have a particle size according to the embodiments described above for the particles.If the dispersion electrolyte contains further particles in addition to the particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, the total amount of particles, i.e., the total solids content, in the dispersion electrolyte typically does not exceed 200 g / L, preferably not 150 g / L, and more preferably not 120 g / L. Thus, good miscibility of the dispersion electrolyte and excessive agglomeration of particles in the deposited layer can be avoided. To achieve efficient dispersion of the particles and, if present, of the other particles in the electrolyte and to avoid significant clumping of the particles in the tin alloy layer, the dispersion electrolyte according to the invention contains at least one anionic and / or at least one nonionic dispersant.Typically, an anionic dispersant contains sulfate groups (OSO3-), sulfonate groups (SO3-), carboxylate groups (CO2-), or carboxy groups (CO2H), which can then be present as anions in aqueous solution. Counterions are usually H. + , alkali metal ions, preferably K + and / or Na + , and / or ammonium ions (NH4 + ) because they result in good water solubility, can increase conductivity, and do not negatively influence the electrodeposition. The electrolyte therefore also contains counterions of the anionic dispersant, preferably Na + and / or K +Sulfate groups and sulfonate groups are dissociated, i.e., non-protonated, at the pH of the dispersion electrolyte. Carboxy groups and carboxylate groups, however, can exist in equilibrium with each other. The anionic and / or non-ionic dispersant is typically used in the dispersion electrolyte at a total concentration of 0.1 to 100 g / L. In particular, it is used in the electrolyte at a total concentration of 0.5 to 50 g / L, preferably 0.6 to 20 g / L. The appropriate amount of dispersant can vary depending on the type of dispersant. In general, the more dispersant used, the better the dispersion of the particles.In the dispersion electrolyte, the weight ratio of the dispersant, selected from anionic dispersants, nonionic dispersants, and combinations thereof, to the total amount of particles (i.e., the solids content), i.e., the particles and, if present, the optional additional particles, is in particular in the range from 25:1 to 1:80, preferably 5:1 to 1:60, more preferably 1:5 to 1:50. Examples of nonionic dispersants are polyalkylene glycol ethers, in particular polyethylene glycol ethers, alkyl polyglucosides, or alkyl polyalkylene glycol ethers, and combinations thereof. According to a preferred embodiment, the dispersant comprises or consists of at least one anionic dispersant. Preferably, at least 60% by weight or more, more preferably at least 80% by weight or more, of the dispersant is one or more anionic dispersants.According to a further preferred embodiment, the dispersant comprises or consists of at least one anionic dispersant selected from sulfate compounds having an alkyl group, an aralkyl group or an aromatic group each having up to 30 carbon atoms, sulfonate compounds having an alkyl group, an aralkyl group or an aromatic group each having up to 30 carbon atoms, and carboxy- or carboxylate-group-containing polymers.More preferably, the anionic dispersant comprises at least one anionic dispersant selected from sulfate compounds having an alkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, sulfate compounds having an aralkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, sulfonate compounds having an aromatic group each with 6 to 24 carbon atoms, preferably 6 to 14 carbon atoms, and combinations thereof. It may also consist of these.According to a particularly preferred embodiment, the anionic dispersant comprises at least one first anionic dispersant selected from sulfate compounds having an alkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, sulfate compounds having an aralkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, and combinations thereof, and at least one second anionic dispersant selected from sulfonate compounds having an aromatic group with 6 to 24 carbon atoms, preferably with 6 to 14 carbon atoms. Preferably, the anionic dispersant consists of at least one first and at least one second anionic dispersant. These are used in particular in a weight ratio of first anionic dispersant to second anionic dispersant of 1:10 to 10:1, preferably 1:8 to 3:1, more preferably 1:3 to 2:1.The combination of the first and second dispersant is advantageous for effective dispersion of the particles and wetting of the surface of the substrate to be coated, which can improve deposition. The sulfate compounds containing an alkyl group are preferably selected from alkyl sulfates, alkyl polyether sulfates, alkyl aryl polyether sulfates, and combinations thereof. The alkyl group having 6 to 24 carbon atoms, preferably 10 to 20 carbon atoms, originates in particular from a fatty alcohol. Polyether groups are preferably polyethylene glycol groups. The sulfonate compounds containing an aromatic group having 6 to 24 carbon atoms, preferably 6 to 14 carbon atoms, are preferably selected from arylsulfonates and polymers containing aromatic sulfonate groups. Particularly preferred arylsulfonates are benzenesulfonic acid, phenolsulfonic acid, and naphthalenesulfonic acid, especially naphthalenesulfonic acid, and salts thereof.In polymers with aromatic sulfonate groups, the underlying aromatic groups preferably each have 6 to 14 carbon atoms and are derived in particular from benzenesulfonic acid, phenolsulfonic acid, and naphthalenesulfonic acid, and salts thereof. Such polymers are, for example, polycondensates of aromatic sulfonate compounds, such as benzenesulfonic acid, phenolsulfonic acid, and naphthalenesulfonic acid, or salts thereof, with formaldehyde, in particular naphthalenesulfonic acid-formaldehyde polycondensates and salts thereof, for example, tamole. ®from BASF SE. According to a further preferred embodiment, the dispersion electrolyte further contains a conductive medium. A conductive medium is understood to be a molecular compound that is present in the dispersion electrolyte in the form of ions and thereby increases its conductivity. The conductive medium differs from the salts of the alloying elements and the conductive salt specified below. For example, a sulfonic acid having 1 to 4 carbon atoms, preferably methylsulfonic acid, or a salt thereof can be used as the conductive medium. The sulfonic acid is preferably used. The conductive medium can be used in addition to the dispersant. The conductive medium can increase the deposition rates. Furthermore, the sulfonic acid can also be used as a reducing agent for tin ions (Sn 4+ to Sn 2+). The conductive medium is used in particular in a concentration of 1 to 40 g / L, preferably 5 to 20 g / L. The dispersion electrolyte has a pH of 7 or less. The pH can result directly from the constituents of the dispersion electrolyte or can be adjusted by adding acids or bases, in particular hydrochloric acid, sulfuric acid, sulfamic acid, sodium hydroxide, ammonia, potassium hydroxide or an aqueous solution thereof, preferably hydrochloric acid, sulfuric acid or potassium hydroxide. Furthermore, the dispersion electrolyte can contain customary additives, as are also known from conventional electrolytes for the electrodeposition of tin alloy layers. For example, customary conducting salts can be added to the electrolyte to increase the conductivity of the electrolyte. The conducting salt can also increase the solubility of the tin or the other alloying elements.The conducting salt is selected, for example, from sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, ammonium chloride, sodium acetate, potassium acetate, ammonium acetate, ammonium fluoride, ammonium bifluoride, sodium fluoride, and potassium fluoride, and combinations thereof, preferably from ammonium fluoride, ammonium bifluoride, ammonium acetate, and combinations thereof. The conducting salt can typically be present in the electrolyte in a concentration of 5 to 70 g / L, preferably 10 to 65 g / L, more preferably 40 to 60 g / L. Furthermore, complexing agents, for example, can be added to the dispersion electrolyte to keep the tin ions or ions of the alloying element stable in solution or to mobilize them, so that the particle-containing layer can be formed uniformly and with a good deposition rate. In principle, all complexing agents known to those skilled in the art and used for tin or electrolytes of the alloying elements can be used as complexing agents.The complexing agent is preferably at least one chelating, water-soluble, organic compound having at least three functional groups selected from amino groups, carboxyl groups, and carboxylate groups. Of the functional groups, at least two groups are preferably amino groups. The amino groups are selected from primary, secondary, and tertiary amino groups. More preferably, the complexing agent contains one or more secondary and / or tertiary amino groups. The functional groups intended for coordination are typically spaced apart by 2 or 3 carbon atoms, so that a stable chelate complex can form. More preferably, the complexing agent is at least one selected from the group consisting of EDTA, DETA, DOTA, and DOTATOC. EDTA stands for ethylenediaminetetraacetic acid. DETA denotes diethylenetriamine. DOTA stands for 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid.DOTATOC refers to a DOTA-derived complexing agent in which a DOTA molecule is linked to the N-terminus of an octapeptide (especially Phe-Cys-Tyr-Lys-Thr-Cys-Thr) via an amide bond. The amount of complexing agent used depends primarily on the concentration of tin ions or the concentration of the ions of the second and third alloying elements in the dispersion electrolyte. The complexing agent is typically present in the electrolyte at a concentration of 5 to 70 g / L, preferably 10 to 65 g / L, and more preferably 40 to 60 g / L. The dispersion electrolyte can be formed by mixing or dissolving a tin salt, a salt of a second alloying element, a salt of the optional third alloying element, the optional organic compound and the further components, in particular the anionic dispersant, the particles, water and optionally a conductive medium, a conductive salt and / or a complexing agent.The particles and, if present, the other particles can advantageously be added as a powdered solid without the need to disperse them separately or to treat the mixture with ultrasound for dispersal. When forming the electrolyte, stirring is preferably carried out and, if necessary, slightly heated to accelerate the dissolution or dispersion of the components. The pH can be adjusted as required, as described above. The dispersion electrolyte according to the invention can advantageously be produced on a large scale and is thus suitable for industrial applications. The electrolyte is storable, and any settled particles can be redispersed by stirring or the like. As a further aspect, the present invention relates to a method for electroplating a substrate with a particle-containing tin alloy layer.The method comprises the electrodeposition of the particle-containing tin alloy layer on a metallic or metallized substrate using the dispersion electrolyte according to at least one embodiment described herein. A coated substrate with a particle-containing tin alloy layer is obtainable via the method, for which the advantages described above are obtained. In particular, it can be a coated substrate as described in more detail below. The method arranges the particles at least partially on the surface of the particle-containing tin alloy layer, so that they form part of the surface. The particle-containing tin alloy layer is typically produced as a final layer, i.e., as the outermost layer, on the substrate.The process can be carried out using all common devices for the electroplating of tin alloy layers, for example, by rack or barrel plating. Typically, the electrolyte is mixed during deposition, for example, by stirring or circulating using a device. Stirring is preferred, for example, at 100 to 700 revolutions per minute (rpm). The metallic or metallized substrate is connected as the cathode in the process. It can be, for example, a metallic component, for example an electronic component, such as a contact, a switch part, or an electrode. The metallic or metallized substrate can consist entirely or partially of one or more metals. Examples of metals include aluminum, silver, copper, nickel, precious metals such as palladium or platinum, steel, stainless steel, brass, and / or bronze.A metal layer that can be electroplated can also be used as the substrate, for example a metallized plastic, in particular with a metal layer made of copper, nickel, silver and / or precious metals such as palladium or platinum. The production of metallized plastics is described, for example, in DE 2126 781 C1 or WO 2020 / 225052 A1, in particular in the examples. The surface to be coated can be cleaned beforehand using conventional methods, for example, degreased. The substrate can also be coated with one or more layers, for example of copper, nickel and / or silver, before deposition of the particle-containing tin alloy layer, which can improve adhesion to the substrate.Such layers can be deposited galvanically on a metallic or metallized substrate and electrolessly (i.e. chemically) on a polar or functionalized plastic, as described, for example, in DE 2126 781 C1 or WO 2020 / 225052 A1. Tin anodes, for example, can be used as the anode. This makes it easy to control the content of tin ions in the electrolyte. Multiple anodes, or anodes of one or a combination of alloying elements, can also be used. The process allows for great flexibility in process control. The particle-containing tin alloy layer can, in particular, be deposited over a wide current density range, for example with a current density of 0.1 to 10 A / dm. 2 , preferably 0.5 to 5 A / dm 2, are deposited. The process is typically carried out at a temperature of 5 to 85°C, preferably 10 to 85°C, more preferably 50 to 80°C, even more preferably 60 to 70°C. In the process, the particle-containing tin alloy layer can be deposited largely homogeneously, i.e. with a fairly uniform distribution of the particles. According to a further embodiment, the electrodeposition can be carried out such that the particles (and / or the other particles, if present) have a gradient. For example, the particle concentration in the interior of the tin alloy layer can be higher than on the outside. Preferably, the particle concentration on the outside is higher than in the interior of the tin alloy layer. A gradient can be obtained, for example, by modifying the mixing, modifying the current density or changing the concentration of the particles during deposition.Greater mixing generally leads to increased particle deposition. Higher current density generally leads to increased deposition of the tin alloy. Furthermore, multiple electrolytes, which differ, for example, in particle concentration, tin ion concentration, and / or the concentration of ions of the second and / or third alloying element, can be used to electroplate the substrate in multiple stages. In principle, the process can be used to produce a particle-containing tin alloy layer with any desired layer thickness. For example, the particle-containing tin alloy layer can be formed with a layer thickness of up to 200 µm or up to 100 µm. Typically, the particle-containing tin alloy layer is deposited with a thickness of 4 to 50 µm, preferably 5 to 30 µm, and more preferably 5 to 20 µm.The layer thickness is measured using X-ray fluorescence measurement in accordance with DIN EN ISO 3497 (2001-12), for example using a Fischerscope X-Ray XDAL fluorescence measuring device for layer thicknesses up to 20 µm. For layer thicknesses of more than 20 µm, the layer thickness is determined at the cross-section of the layer using a microscope. Typically, the deposition is carried out in such a way that the thickness of the tin alloy is greater than the particles. A further aspect of the present invention describes a coated substrate with a particle-containing tin alloy layer. The particle-containing tin alloy layer comprises 100 parts by weight of tin alloy and a total of 0.5 to 250 parts by weight of at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof. The tin alloy contains - 5 wt.% or more and 50 wt.-% or less of a second alloying element selected from copper, silver, bismuth, nickel, cobalt, cadmium, zinc, manganese, and combinations thereof, - optionally a third alloying element other than tin and the second alloying element, and - optionally carbon, and the remainder consists of tin and any unavoidable impurities. The particles are not counted as part of the tin alloy. Unavoidable impurities can arise, for example, from the decomposition of electrolyte components and lead, for example, to the incorporation of carbon, oxygen, nitrogen, and / or boron. This means that a certain amount of carbon can be incorporated into the tin alloy even without the use of the other organic compounds described above in the dispersion electrolyte. However, the content is then typically lower than if one of the other organic compounds described above is deliberately used.The particle-containing tin alloy layer typically forms an outermost layer on the coated substrate. The particles are at least partially arranged on the surface of the particle-containing tin alloy layer, so that they form part of the surface of the particle-containing tin alloy layer or the outermost layer of the coated substrate. The particle-containing tin alloy layer contains the particles in particular in an amount of 1 to 200 parts by weight, preferably 5 to 150 parts by weight, more preferably 10 to 100 parts by weight, based on 100 parts by weight of tin alloy. The coated substrate with the particle-containing tin alloy layer is obtainable by the method for electroplating a substrate with a particle-containing tin alloy layer using the dispersion electrolyte according to at least one embodiment described herein. The advantages described above are therefore obtained.The substrate is, as described above, a metallic or metallized substrate coated with the particle-containing tin layer. Furthermore, the optional and preferred embodiments described above apply analogously to the coated substrate. This applies in particular to the substrate coated with the particle-containing tin alloy layer, the layer thicknesses, the particle sizes, the optional additional particles, the optional gradient of the particles, and the embodiments relating to the second and third alloying elements. If present, the additional particles made of a conductive carbon material are present in the particle-containing layer in an amount of 1 to 100 parts by weight, preferably 2 to 50 parts by weight, more preferably 3 to 30 parts by weight, based on 100 parts by weight of tin alloy.The total amount of particles typically does not exceed 250 parts by weight, preferably not 200 parts by weight, more preferably not 150 parts by weight, based on 100 parts by weight of tin alloy. The particle-containing tin alloy layer is particularly mechanically stable and corrosion-resistant in acidic, neutral, and alkaline ranges. According to a preferred embodiment, the tin alloy consists of 50 wt.% or more, preferably 65 wt.% or more, even more preferably 75 wt.% or more of tin. The second alloying element is present in the tin alloy at 5 wt.% or more and 50 wt.% or less, preferably 5 to 30 wt.%, more preferably 10 to 25 wt.%, even more preferably 15 to 20 wt.%, based on the tin alloy. The tin alloy can optionally contain a third alloying element that is different from tin and the second alloying element.The third alloying element is typically present in a lower amount than the second alloying element. According to a preferred embodiment, the third alloying element is present in the tin alloy at up to 10 wt.%, more preferably 0.1 to 5 wt.%, even more preferably 0.5 to 3 wt.%, for example 2 wt.%. As stated above, the third alloying element is selected in particular from nickel, cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, tungsten, and combinations thereof. Preferably, the third alloying element is selected from nickel, cobalt, antimony, copper, cadmium, bismuth, and combinations thereof. Furthermore, the tin alloy can optionally contain carbon in an amount of up to 12 wt.% carbon, in particular up to 10 wt.% carbon, preferably 5 to 10 wt.% carbon. As described above, the carbon is an alloying constituent and is present in particular in nanoscale or atomic form.According to a preferred embodiment, the tin alloy of the particle-containing tin alloy layer contains - 5 wt.% or more and 50 wt.% or less of the second alloying element, - up to 10 wt.% of the third alloying element, which is different from the second alloying element and is selected from nickel, cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, tungsten and combinations thereof, and - optionally up to 12 wt.% carbon. The remainder of the alloy consists of tin and any unavoidable impurities. According to a particularly preferred embodiment, the tin alloy of the particle-containing tin alloy layer contains - 5 to 30 wt.%, preferably 10 to 25 wt.%, nickel as the second alloying element, - 0.1 to 5 wt.%, preferably 0.5 to 3 wt.-%, of the third alloying element, which is selected from cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, tungsten and combinations thereof, preferably from cobalt, copper and antimony, and - optionally up to 10 wt.% carbon. The tin alloy consists of the remainder tin and any unavoidable impurities. The particle-containing tin alloy layer according to this embodiment can be produced comparatively inexpensively and has good corrosion resistance. In the strongly acidic range, the corrosion resistance is better than that of a corresponding tin-nickel alloy in which nickel is not proportionally replaced by the third alloying element. According to a further particularly preferred embodiment, the tin alloy of the particle-containing tin alloy layer contains - 5 to 30 wt.%, preferably 10 to 25 wt.%, of copper, cobalt, silver or bismuth as a second alloying element, - 0.1 to 5 wt.%, preferably 0.5 to 3 wt.-% of the third alloying element, which is different from the second alloying element and is selected from nickel, cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, tungsten and combinations thereof, preferably from nickel, cobalt, antimony, copper, cadmium and bismuth, and - optionally up to 10 wt.% carbon. The tin alloy consists of the remainder tin and any unavoidable impurities. The particle-containing tin alloy layer according to this embodiment has particularly good corrosion resistance. As explained above, the coated substrate has good corrosion resistance. Compared to a substrate coated with a corresponding tin alloy layer without particles, it also has a reduced overvoltage for electrochemical reactions in aqueous media.The coated substrate is therefore used, for example, as an electronic component, in particular as a switch, contact, electrode, or other component of an electrochemical cell. It is preferably used as an electrode of an electrochemical cell, for example in the electrolysis of water or aqueous media, in particular acidic aqueous media such as sulfuric acid. It can be used independently as an anode, as a cathode, and as an anode and as a cathode. The dispersion electrolyte according to the invention can therefore be used to produce an electronic component, in particular to produce a switch, a contact, an electrode, and a component of an electrochemical cell, preferably an electrode. As a further aspect, the present invention provides an electrochemical cell comprising the coated substrate according to at least one embodiment described herein.The coated substrate preferably serves as the electrode. It can be used independently as an anode, as a cathode, preferably as an anode and as a cathode. Examples of an electrochemical cell are a redox flow battery, a fuel cell and an electrolyzer. Examples The present invention is illustrated below by examples. It is not limited to these examples. Measurement methods The following measurement methods were used. 1) Layer thickness The layer thickness was measured using a Fischerscope X-Ray XDAL fluorescence measuring device in accordance with DIN EN ISO 3497 (2001-12). An averaged measured value is given. 2) Composition The composition of the particle-containing tin alloy layer was also analyzed by X-ray fluorescence analysis on the coated substrate surface using the aforementioned device in accordance with DIN EN ISO 3497 (2001-12). The measured area was approximately 200 x 150 µm.The measured values ​​are obtained with an accuracy of ± 2 wt% or better. Preparation of the metallic substrates: Steel sheets (DC03) measuring 50 x 120 x 0.4 mm were used for the tests. These were pretreated as follows: 1 Degreasing: SLOTOCLEAN AK 160 (02040) 65 degreaser. o C 5 min 2 Rinse water RT* 3 Pickling aqueous HCl, 18%, with SLOTOCLEAN BEF 30 RT 30 s (01001) 4 Rinse water RT 5 Anodic degreasing Degreaser SLOTOCLEAN EL DCG (02037), 8 A / dm 2 RT 2 min 6 Rinse water RT 7 Pickling aqueous HCl, 5% RT 30 s 8 Rinse water RT 9 Deposition Nickel Strike, 3 A / dm 2RT 6 min interlayer *RT = room temperature Reagents The following reagents were used for the tests, among others. Slotoclean AK 160 (contains NaOH and disodium metasilicate), SLOTOCLEAN EL DCG (contains NaOH, disodium metasilicate and sodium carbonate), and SLOTOCLEAN BEF 30 (contains but-2-yne-1,4-diol and ethoxylated isotridecanol) are products from Dr.-Ing. Max Schlötter. Nickel Strike: Nickel electrolyte for the electrodeposition of the interlayer, from Dr.-Ing. Max Schlötter, containing 180 g / L NiCl2∙6H2O according to DIN 50970, 8 g / L HCl (concentrated), water SLOTOLOY NIT 11: Bath additive from Dr.-Ing. Max Schlötter for shiny tin-nickel coatings, containing diethylenetriamine as complexing agent, ammonium hydrogen difluoride as conductive salt, hydrochloric acid.Barium titanate (BaTiO3, perovskite structure): particle size 0.8 µm (aspect ratio < 3.0) from Sigma Aldrich, CAS: 12047-27-7 Boron nitride (BN, hexagonal): particle size about 1 µm, flake-shaped (aspect ratio > 3.0) from Sigma-Aldrich, CAS: 10043-11-5 Tamol. ® : Naphthalenesulfonic acid-formaldehyde polycondensates (sodium salts) from BASF SE Examples 1 to 4 and Comparative Example 1 Preparation of the electrolytes For Examples 1 to 4 and Comparative Example 1 (VB1), electrolytes with the following components were prepared in a plastic beaker (2 L): - 250 mL / L SLOTOLOY NIT 11 (bath additive) - 48 g / L SnCl2∙2H2O (corresponding to 25 g / L Sn) - 243 g / L NiCl2∙6H2O (corresponding to 60 g / L Ni) - 0.9 g / L Tamol ®(Dispersant) - distilled water - boron nitride (BN) or barium titanate (BaTiO3) according to Table 1 For this purpose, water (400 mL / L electrolyte) was first introduced and heated to 65°C. SnCl2·2H2O, NiCl2·6H2O, the bath additive, and the dispersant were added, the pH was adjusted to 4.6 with KOH, and the solids were dissolved at 65°C with stirring (400 rpm). After complete dissolution, the mixture was topped up with water. Then, powdered boron nitride (BN) was slowly added in Examples 1 and 2, and powdered barium titanate (BaTiO3) in Examples 3 to 4, and the mixture was dispersed with stirring (400 rpm). In Comparative Example 1, no particles were added. The pH was readjusted to 4.6 by adding hydrochloric acid and ammonia. The electrolyte volume was 2 L in each case.Table 1 BN (hexagonal) BaTiO3 (perovskite structure) [g / L] [g / L] Example 1 10 - Example 2 20 - Example 3 - 20 Example 4 - 40 Comparative Example 1 - - Electroplating Steel sheets were pretreated as described above and precoated with a nickel layer. The metallic substrates thus obtained were each electroplated as follows. The electrolyte was mixed in a plastic beaker (2 L) using a stirring bar (40 mm) (400 rpm). The steel sheets were each connected as the cathode and immersed 10 cm into the electrolyte. Two soluble Ni electrodes (25 x 120 x 5 mm) served as the anode and were arranged parallel to the cathode on both sides at a distance of 4 cm. The anodes were also immersed to a depth of 10 cm. The two parallel anodes were connected in series with the electrolyte, the cathode and a direct current source.The deposition was carried out at 65°C and a current density of 1 A / dm. 2for 35 min. Assessment of the deposited layers In examples 1 to 4 and in comparative example 1 (VB1), dense, pore-free and well-adhering tin alloy layers were deposited. The layer thicknesses were approximately 10 µm. Figs. 1 and 2 show scanning electron microscope images of examples 1 and 2 at a magnification of 500. It can be seen from Fig. 1 that boron nitride is effectively incorporated into the tin alloy layer at a concentration in the dispersion electrolyte of 10 g / L. The piezoelectric, i.e. non-electrically conductive, boron nitride particles can be seen as light areas in Fig. 1. The boron nitride particles therefore form part of the surface of the particle-containing tin alloy layer. Agglomerates of several particles were occasionally observed. As can be seen in Fig. 2, at a concentration of 20 g / L, more boron nitride particles were incorporated into the tin alloy layer.In particular, in Example 2, the incorporation was homogeneous across the entire layer. The composition was determined for Examples 1 and 2, 3, 4, and Comparative Example 1 (VB1) (see Table 2). Table 2 Example / 1 2 3 4 VB1 Element [wt.%] [wt.%] [wt.%] [wt.%] [wt.%] B 3.5 14.5 - - - C 4.2 5.2 9.8 11.0 10.6 N 1.3 4.0 2.1 0.7 3.0 O 1.0 0.8 13.7 2.4 2.2 Ni 20.8 16.2 15.1 16.2 18.3 Sn 69.3 59.3 32.5 28.6 60.9 Ti - - 9.4 11.4 - Ba - - 19.4 27.5 - The analyses confirm the incorporation of boron nitride or barium titanate into the tin alloy layers of Examples 1 to 4. Measurement of the overvoltages The determination of the overvoltages was carried out in an electrochemical cell from Gaskatel (Flexcell PP) with a sample area of ​​3 cm. 2The overpotentials were measured for the alkaline electrolysis of water in 30% aqueous KOH. The potential at which a current flow was observed was determined for the evolution of hydrogen (HER) or oxygen (OER). The coated substrate was used as an electrode in a chamber and connected as the cathode or anode, respectively. A standard hydrogen electrode (Gaskatel Hydroflex) served as the reference electrode. The counter electrode used consisted of wound Pt wire. The overpotential was the measured potential at 25°C for a current of -10 mA (-3.3 mA / cm 2 ) minus the theoretical potential of 0 V for hydrogen (HER) or at 25°C for a current of 10 mA (3.3 mA / cm 2) minus the theoretical potential of +1.23 V for oxygen (OER). The smaller the amount of overpotential, i.e. the closer the measured value is to 0, the lower the overpotential. The results are summarized in Table 3. Table 3 Particles in the electrolyte HER [V] OER [V] Comparative example 1 - -1.01 +0.22 Example 1 10 g / L BN -0.68 +0.20 Example 2 20 g / L BN -0.49 +0.24 Example 3 20 g / L BaTiO3 -0.69 +0.17 Example 4 40 g / L BaTiO3 -0.62 +0.10 Compared to Comparative example 1, the total overvoltages could be reduced by 0.33 V just by incorporating small amounts of piezoelectric boron nitride in Example 1. The overpotential for the formation of hydrogen was significantly reduced; No significant change in oxygen formation was observed. This effect was enhanced by the increased incorporation of boron nitride particles in Example 2, and the overpotential was reduced by approximately 0.5 V overall.In Examples 3 and 4, a significant reduction in the overpotential for the formation of hydrogen and a slight reduction in the overpotential for the formation of oxygen were observed with piezoelectric barium titanate. Overall, the overpotential was reduced by approximately 0.4 V and approximately 0.5 V in Examples 3 and 4, respectively. This confirms that the incorporation of piezoelectric boron nitride particles and piezoelectric barium titanate particles can reduce overpotentials for electrochemical water splitting in aqueous media. A greater reduction in the overpotential was observed at higher particle concentrations. As shown in Examples 1 to 4, the coated substrates from Examples 1 to 4 are suitable as anodes and, in particular, as cathodes for electrolysis in aqueous media. Significantly reduced overpotentials were measured, particularly for the cathode reaction, i.e., the formation of hydrogen.

Claims

Patent claims 1. Dispersion electrolyte for the electrodeposition of particle-containing tin alloy layers, comprising: - tin ions in a concentration of 2 to 100 g / L; - ions of a second alloying element selected from copper, silver, bismuth, nickel, cobalt, cadmium, zinc, manganese and combinations thereof in a concentration of 1 to 100 g / L; - at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles and combinations thereof in a total concentration of 1 to 200 g / L; - at least one dispersant selected from anionic dispersants, non-ionic dispersants and combinations thereof; and - water; wherein the dispersion electrolyte has a pH of 7 or less.

2. Dispersion electrolyte according to claim 1, wherein the particles are made of BN (hexagonal), AlN, ZnO, GaPO4, M1 2y MA 1- M1 2y MA 1- TiN, TiC, TiB2, Ti2CN, B4C, WC and combinations thereof, and wherein in the general formulas the following applies: M1 is in each case independently at least one element selected from Li, Na and K, preferably Li; MA is in each case independently at least one element selected from Ca, Sr, Ba, Pb and La; MB is selected from Zr, Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MC is selected from Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MD is selected from Hf, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; ME is selected from Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3; MF is selected from V, Ta and Mn; MG is selected from Ta and Mn; MH is Mn; x satisfies in each case independently 0 ≤ x ≤ 1; and y each independently satisfies 0 ≤ y ≤ 1.

3. Dispersion electrolyte according to claim 2, wherein the particles are made of BN (hexagonal), AlN, ZnO, GaPO4, Li2[Zr x Ti 1−x ]O3, Li 2y MA 1-y [Zr x Ti 1−x ]O3, MA[Zr x Ti 1−x ]O3, Pb[Zr x Ti 1−x]O3, LaMnO3, and LiNbO3, and combinations thereof, and wherein each MA is independently at least one element selected from Ca, Sr, and Ba; each x independently satisfies 0 ≤ x ≤ 1; and each y independently satisfies 0 < y < 1.

4. Dispersion electrolyte according to any one of the preceding, wherein the second alloying element is nickel, or wherein the second alloying element is selected from copper, silver, bismuth, cobalt, and combinations thereof.

5. Dispersion electrolyte according to any one of the preceding claims, wherein the dispersion electrolyte comprises up to 40 g / L of ions of a third alloying element different from the second alloying element and selected from nickel, cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, tungsten, and combinations thereof.Dispersion electrolyte according to one of the preceding claims, wherein the dispersion electrolyte contains - 5 to 80 g / L, preferably from 10 to 70 g / L, of tin ions; - 2 to 80 g / L, preferably 5 to 70 g / L, of ions of the second alloying element; and - optionally 1 to 20 g / L, preferably 1 to 15 g / L, of ions of the third alloying element.

7. Dispersion electrolyte according to one of the preceding claims, wherein it contains at least one further organic compound that is decomposed during electrodeposition and serves as a carbon source for the tin alloy. and which preferably comprises a xanthate, a carbamate, Turkey red oil, a ketone, in particular benzalacetone, an aromatic aldehyde, in particular naphthaldehyde, and combinations thereof.

8. Dispersion electrolyte according to any one of the preceding claims, wherein the dispersant comprises at least one anionic dispersant selected from sulfate compounds containing an alkyl group, an aralkyl group, or an aromatic group, each having up to 30 carbon atoms, sulfonate compounds containing an alkyl group, an aralkyl group, or an aromatic group, each having up to 30 carbon atoms, and polymers containing carboxy or carboxylate groups. 9.The dispersed electrolyte according to claim 8, wherein the anionic dispersant comprises at least one first anionic dispersant selected from sulfate compounds having an alkyl group with 6 to 24 carbon atoms, sulfate compounds having an aralkyl group with 6 to 24 carbon atoms, and combinations thereof, and at least one second anionic dispersant selected from sulfonate compounds having an aromatic group with 6 to 24 carbon atoms.

10. The dispersed electrolyte according to any one of the preceding claims, wherein the dispersed electrolyte contains one or more complexing agents, each independently an organic compound having at least three functional groups selected from amino groups, carboxyl groups, and carboxylate groups. 11.A method for electroplating a substrate with a particle-containing tin alloy layer, comprising electroplating the particle-containing tin alloy layer on a metallic or. metallized substrate using the dispersion electrolyte according to any one of claims 1 to 10.

12. Coated substrate with a particle-containing tin alloy layer, wherein the particle-containing tin alloy layer comprises 100 parts by weight of tin alloy and a total of 0.5 to 250 parts by weight of at least one type of particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, and wherein the tin alloy contains - 5 wt.% or more and 50 wt.% or less of a second alloying element selected from copper, silver, bismuth, nickel, cobalt, cadmium, zinc, manganese, and combinations thereof, - optionally a third alloying element different from the second alloying element, and - optionally carbon, and the remainder consists of tin and any unavoidable impurities.

13. Coated substrate according to claim 12, wherein the tin alloy contains at least 50 wt.-% tin.

14. The coated substrate according to claim 12 or 13, wherein the tin alloy contains - up to 10 wt.% of the third alloying element, which is different from the second alloying element and is selected from nickel, cobalt, chromium, zinc, silver, gold, antimony, copper, cadmium, bismuth, manganese, tungsten, and combinations thereof, and - optionally contains up to 12 wt.% carbon, the remainder being tin and unavoidable impurities.

15. A coated substrate according to claim 14, wherein the tin alloy contains - 5 to 30 wt.% of the second alloying element, which is nickel or selected from copper, silver, cobalt, and bismuth, - 0.1 to 5 wt.% of the third alloying element, and - optionally up to 10 wt.% carbon, the remainder being tin and any unavoidable impurities.

16. An electrochemical cell comprising the coated substrate according to any one of claims 12 to 15.