Coating for electrode

Abstract

Method of forming a multilayered coating on an electrode, preferably anode, metal foil, comprising the steps of, (i) Providing a primer composition (a) and an active electrode composition (b); (ii) Simultaneously or substantially simultaneously applying the primer composition (a) and the active electrode composition (b) onto the electrode metal foil, wherein the primer composition (a) forms a primer layer (A) directly on the surface of the electrode metal foil and the active electrode composition (b) forms an active electrode layer (B) directly on the surface of the primer layer (A) to form the multilayered coating on the electrode metal foil; and (iii) drying the multilayered coating, wherein the primer composition (a) comprises, (I) at least one electro-conducting component comprising particulate carbon, (II) at least one binder component, (III) at least one co-binder component different from binder component (II), the co-binder being at least one polysaccharide or modified polysaccharide, and (IV) a dispersant component, wherein the dispersant component (IV) comprises a polymer of N-vinylpyrrolidone, the polymer of N-vinylpyrrolidone being (i) a homopolymer of N-vinylpyrrolidone which exhibits a K value in the range from 10 to 70; or (ii) a random copolymer of N- vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer which exhibits a K value in the range from 10 to 70. The invention also concerns a multilayered coated electrode, preferably anode, metal foil, comprising a primer layer (A) located directly on the surface of the electrode metal foil and an active electrode layer (B) which is located directly on the surface of the primer layer (A), the multilayered coated electrode metal foil being obtainable by the aforesaid method. The invention also includes the use of said polymer in the method.

Description

[0001] BASF SE 240343

[0002] Coating for Electrode

[0003] Field of the Invention

[0004] The present invention relates generally to batteries, and in particular, to primers for coating electrodes of batteries. The invention concerns a method for providing a multilayered coated electrode, particularly an anode, metal foil by employing said primer composition and also the coated electrode, preferably anode. The invention also relates to multilayered coated electrode produced by the method. The invention additionally relates to the use of a polymer in a method of forming a multilayered coating on an electrode, preferably anode, metal foil as a dispersant and for facilitating compatible surface tension between the layers.

[0005] Background of the Invention

[0006] Battery technology is becoming more important given the increasing concerns about global warming and climate change and as such there is a huge increase in the demand for renewable energies to reduce greenhouse gas emissions. The need for efficient batteries, specifically secondary batteries, i.e. rechargeable batteries, and in particular lithium-ion batteries, for storage of electricity, particularly "green" electricity is therefore an important part of achieving these objectives.

[0007] A typical battery, often regarded as an electrochemical cell, is composed of a cathode and an anode which participate in an electrochemical reaction. In a lithium-ion battery typically there is an anode comprising lithium-carbon (graphite) and electrolyte which is bounded by an anode metal foil and a cathode comprising lithium-metal oxide in an electrolyte which is bounded by a cathode metal foil. The anode and cathode are separated by a porous separator which only permits lithium ions to travel between the anode and cathode depending upon whether the battery is discharging or charging. Metal foils may be regarded as current collectors. In the case of a cathode the metal foil is typically aluminium and in the case of an anode it is typically copper.BASF SE 240343

[0008] In order to avoid the metal foils directly taking part in the electrochemical reactions the metal foils are normally coated to protect the metal from either being corroded or deposits being formed. Nevertheless, it is vital that the coating permits adequate electrical flow and maintains adequate protection of the metal foil. The battery metal foil coating would normally comprise an electro-active layer which allows the electrical current to transmit. This electro-active layer is typically formed from a layer of an active electrode composition containing electrically conductive components, typically carbon.

[0009] The active electrode composition which forms the electrode electroactive layer is normally affixed to the metal foil by a suitable adhering agent, which can suitably be a primer layer, which may be regarded as a binder layer or adhering layer. It is important to ensure that the electrode electroactive layer remains intact and affixed to the whole metal foil surface in order to avoid any breach of the protective electroactive layer and direct contact of the electrode electrolyte solution with any part of the metal surface. In addition, it is essential that the binder layer permits adequate electrical current flow between the electrolyte and the electrode electroactive layer.

[0010] United States Patent Application Publication No US 2010 / 0291442A1 describes an electrode having a conductive support; a first primer layer adjacent to the conductive support; and a second primer layer positioned adjacent to the first primer layer; and an electroactive layer in electrical communication with the second primer layer. The first primer layer comprises a first polymeric material having less than 30% by weight of a cross-linked polymeric material and the second primer layer comprises less than 30% by weight of a cross-linked polymeric material. In one embodiment the first polymeric material is polyvinyl alcohol. In another embodiment the second polymeric material comprises polyvinylpyrrolidone, polyvinyl acetate, polyacrylate, or polyvinyl butyral.

[0011] European Patent No 3582297 B1 describes a multilayered electrode for a rechargeable battery which includes a binder having high crystallinity. The electrode is said to comprise a current collector; a primer coating layer applied on the current collector, the primer coating layer including PVdF, as a first binder, and a conductiveBASF SE 240343

[0012] material; and an electro-composite layer applied on the primer coating layer, the electrode composite layer including a second binder and an electrode active material.

[0013] China Patent Application No CN 113140699 A relates to lithium-ion batteries and discloses a composite negative electrode sheet that comprises a negative electrode coating and a copper foil. The negative electrode coating comprises two or more layers, wherein the inner layer and outer layer comprises different active substances. The examples describe various inner layers, for instance example 1 describes preparing an inner layer by combining artificial graphite, carbon black, sodium carboxymethylcellulose, styrene butadiene rubber and deionised water to form a slurry, which is evenly coated on the negative electrode current collector electrolytic copper foil and rolled after drying. Example 3 describes preparing an inner layer of the negative electrode employing artificial graphite, carbon fibre, polyvinylpyrrolidone, polyacrylic acid and deionised water to form a slurry, which is evenly coated on the negative electrode current collector electrolytic copper foil and rolled after drying.

[0014] Japanese Patent Application No JP 2013004400 A provides a paste application device for applying in electrode paste to a support and a method for manufacturing an electrode. In the paste application apparatus, the dispersant is said to be a vinylpyrrolidone polymer having a basic functional group so that the positive electrode conductive material is well dispersed in the electrode paste. The positive electrode may be formed by directly applying a positive electrode paste onto a support. The positive electrode paste is said to be discharged from the discharge port of the device and applied to one side of the support with a certain thickness. Example 1 describes forming the positive electrode paste by combining positive electrode conductive material, dispersant and binder. The positive electrode conductive material was said to be Acetylene black; the dispersant was said to be a vinylpyrrolidone polymer and the binder a polyvinylidene fluoride with N-methyl pyrrolidone as the solvent.

[0015] US Published Patent Application No US 2023 / 0068865 A1 relates to a battery binder, a lithium-ion battery negative plate and a lithium-ion battery. The documentBASF SE 240343

[0016] describes a battery binder comprising a water-based polymer with a hydrophilic unit and a hydrophobic unit. In the polymer, a medium-low molecular weight polymer accounts for less than 5 weight % of the total polymer. The molecular weight of the medium-low molecular weight polymer is less than or equal to 100,000.

[0017] US Published Patent Application No 2021 / 0328225 A1 describes a negative electrode including a current collector and a negative electrode active layer disposed on the current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes silicon particles having an average particle diameter (D50) of 4 pm to 10 pm. The conductive agent includes carbon nanotubes and a graphite type conductive agent, and the binder includes a copolymer containing a polyvinyl alcohol-derived unit and an ionised substituted acrylate derived unit. Example 1 describes the preparation of a carbon nano tube dispersion employing bundle type carbon nanotubes composed of multiwall carbon nano tube units having an average diameter of 15 nm and an average length of 15 pm, polyvinylpyrrolidone (PVP) as a dispersant, and water as a dispersion medium.

[0018] International Application No WO2024 / 085296 A1 is said to relate to a method for manufacturing a lithium metal battery negative electrode material using a graphene pre-treatment substrate. Specifically, the method provides the lithium metal battery negative electrode material in which lithium metal foil is pretreated with graphene, which is said to have cohesive and conductive properties in order to laminate the lithium metal foil to the negative electrode substrate.

[0019] German published patent application No. DE 10342974 A1 describes a primer for use in electrochemical cells containing a lithium borosilicate of specified composition as binder. A primer (I) for use in electrochemical cells contains a lithium borosilicate of the formula LiwBxSiyOz as binder, in which w, x, y, z are greater than 0. The disclosure includes (1) electrochemical cells with a cathode and an anode, in which the collectors for the cathode and / or for anode are coated with a layer of (I); (2) a method for the production of (I) by adding an aqueous solution of lithium hydroxide and boric acid, and / or lithium borate, to a solution of a silicate with stirring.BASF SE 240343

[0020] US published patent application No. US2023163283 A1 describes an anode for a lithium secondary battery which includes an anode current collector, a primer layer formed on a surface of an anode current collector, and an anode active material layer including a first anode active material layer and a second anode active material layer sequentially disposed on the primer layer. Each of the first anode active material layer and the second anode active material layer includes a silicon-based active material. A ratio of a content of the silicon-based active material in the second anode active material layer relative to a content of the silicon-based active material in the first anode active material layer among a total content of the silicon-based active material included in the anode active material layer is greater than 1.25 and less than 5.

[0021] International application No. W02009054987 A1 reveals primer arrangements that facilitate electrical conduction and adhesive connection between an electroactive material and a current collector are presented in this document. In some embodiments, primer arrangements described include first and second primer layers. The first primer layer may be designed to provide good adhesion to a conductive support. In one particular embodiment, the first primer layer comprises a substantially uncross-linked polymer having hydroxyl functional groups, e.g. polyvinyl alcohol. The materials used to form the second primer layer may be chosen such that the second primer layer adhered to both the first primer layer and an electroactive layer. In certain embodiments including combinations of first and second primer layers, one or both of the first and second primer layers comprises less than 30% by weight of a cross-linked polymeric material. A primer including only a single layer of polymeric material is also provided.

[0022] A review by Carl D Reynolds et al. entitled, 'A review of metrology in lithium-ion electrode coating processes", Materials & Design 209 (2021) 109971, considers lithium-ion battery electric design and manufacture and considers that the slurry coating step has significant implications for electrode design. The review reveals that slurry rheology is important to the coating process and determined by microstructural properties of the coating. Reference is made to pumped systems (i.e. slot die coating), the viscosity (at the shear rates created in the tubing and the die), which are said to dictate the pressure of the system at a given flow rate, and the pressureBASF SE 240343

[0023] limits of the system may dictate the maximum flow rate that can be used, which can limit the speed of coating.

[0024] An article by Ralf Diehm et al. entitled, "High-Speed Coating of Primer Layer for Li-Ion Battery Electrodes by Using Slot Die Coating", Energy Technol.2020, 8, 2000259 (1-8), discusses a reduction of the inactive components can increase the energy density and reduce production cost of Li-ion batteries. It is revealed, however, that an effective reduction of the binder amount also negatively affects the adhesion of the electrode. Slot die coating of a primer layer for Li-ion anodes was investigated. The primer formulation was a water-based formulation consisting of equal parts of carboxy methyl cellulose (CMC), styrene butadiene rubber (SBR), and carbon black (CB).

[0025] An article by Ralf Diehm et al. entitled, "In Situ Investigations of Simultaneous Two Layer Slot Die Coating of Component Graded Anodes for Improved High Energy Li-Ion Batteries", Energy Technol. 2020, 8, 1901251 (1-7) describes the use of thicker electrodes which is said to be able to contribute to a reduction in cell costs. The possibility of simultaneous multilayer slot die coating was investigated to improve the electrode properties of medium and high-capacity anodes. The stable coating window of the two-layer slot die coating process was investigated to produce property graded multilayer electrodes. Electrodes with different styrene butadiene rubber (SBR) gradients were investigated with regard to adhesive force and electrochemical performance.

[0026] An article by Sandro Spiegel et al. entitled, "High-speed slot die coating of primer layers for Li-ion battery electrodes: model calculations and experimental validation of the extended coating window depending on coating speed coating gap and viscosity", J. Coat. Technol. Res., 41 (2) 493-505, 2024 refers to very thin primer layers being used to improve electrode adhesion on substrates or act as blocker layers to prevent corrosion in the case of aqueous cathodes. High-speed coating is said to be mandatory for these configurations to ensure the economic viability of the process. It is proposed that one way to realise high-speed coating is a setup including a slot die and a vacuum box to stabilise the coating bead. Another approach is said to be and at the same primer layer between the active material andBASF SE 240343

[0027] current collector which is said to offer the possibility of simultaneously improving adhesion, electrical conductivity and sell performance, even for poorly adhesive electrodes with low binder content. The layer thickness of adhesive primer layers should apparently be in the range of approximately 0.5 to 2 pm. The article describes three aqueous solutions being prepared with a defined content of carboxymethylcellulose (CMC) and disodium 4,4'-bis(2-sulfonatostyryl)biphenyl (DSBB).

[0028] When producing multilayered battery electrode foil coatings, it is more desirable to apply the coatings, for instance primer layer and electrode active layer, at the same time. This avoids subjecting the electrode foils to coating procedures two or more times if for instance the coatings were to be applied separately. It is therefore less time-consuming and hence more efficient to coat the electrode foils simultaneously. Furthermore, typical high-speed techniques for coating electrode foils, include slide bead coating, slide curtain coating, slot bead coating, slot curtain coating, and tensioned web coating.

[0029] A problem that can occur in such multilayered battery electrode coatings is that the coated electrodes often lack mechanical stability, high adhesion or peel force, specifically as regards the electrode active layer being adhered to the electrode foil, especially the anode foil. It would be desirable to provide an adhesive system, for instance a primer layer, that is able to achieve effective and / or good affixing of an electrode active layer, particularly anode active layer, to an electrode foil, particularly anode foil. In addition, it is necessary that said adhesive system, typically primer layer, used to adhere the electrode active layer to the electrode foil permits sufficient electrical conductivity between the electrode foil and the electroactive layer. A problem that can occur in multilayered battery electrode coatings is imperfections or defects in the surface coating. This can adversely affect electrical flow across the electrode foils. Furthermore, it would be desirable to provide such multilayer coatings containing a primer coating which can provide a coating to the electrode foil with reduced imperfections or defects by comparison to conventional primers.

[0030] The inventors realised that such problems in multilayered coatings for an electrode foil can be because of surface tension. Variations in or incompatibilities of theBASF SE 240343

[0031] surface tension exhibited by the primer layer can result in imperfections of the multilayer coating when the primer layer and electrode active layer are applied to the metal foil at the same time. Furthermore, such incompatibilities in surface tension can even result in convection flows within the multilayer coating before it has dried. Thus, a further problem addressed by the present invention is to employ a primer composition which avoids the surface tension incompatibilities of the primer layer. The inventors discovered that dispersants employed to disperse the electrically conductive carbon particles in the primer formulation can have an adverse effect on surface tension. Further, the inventors discovered that surface tension incompatibilities of the primer layer in the multilayered coating can be avoided by employing a dispersant which is a polymer of N-vinylpyrrolidone. As such, the present invention is able to overcome the aforesaid problems with multilayer coatings.

[0032] Summary of the Invention

[0033] The present invention provides method of forming a multilayered coating on an electrode, preferably anode, metal foil, comprising the steps of,

[0034] (i) Providing a primer composition (a) and an active electrode composition (b);

[0035] (ii) Simultaneously or substantially simultaneously applying the primer composition (a) and the active electrode composition (b) onto the electrode metal foil, wherein the primer composition (a) forms a primer layer (A) directly on the surface of the electrode metal foil and the active electrode composition (b) forms an active electrode layer (B) directly on the surface of the primer layer (A) to form the multilayered coating on the electrode metal foil; and

[0036] (iii) drying the multilayered coating,

[0037] wherein the primer composition (a) comprises,BASF SE 240343

[0038] (I) at least one electro-conducting component comprising particulate carbon,

[0039] (II) at least one binder component,

[0040] (III) at least one co-binder component different from binder component (II), the co-binder being at least one polysaccharide or modified polysaccharide, and

[0041] (IV) a dispersant component,

[0042] wherein the dispersant component (IV) comprises a polymer of N-vinylpyrrolidone, the polymer of N-vinylpyrrolidone being (i) a homopolymer of N-vinylpyrrolidone which exhibits a K value in the range from 10 to 70; or (ii) a random copolymer of N-vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer which exhibits a K value in the range from 10 to 70.

[0043] A further aspect of the present invention concerns a multilayered coated electrode, preferably anode, metal foil, comprising a primer layer (A) located directly on the surface of the electrode metal foil and an active electrode layer (B) which is located directly on the surface of the primer layer (A), the multilayered coated electrode metal foil being obtainable by the aforementioned method or any of the preferred embodiments.

[0044] A still further aspect of the present invention concerns the use of a polymer of N-vinylpyrrolidone in a method of forming a multilayered coating on an electrode, preferably anode, metal foil as a dispersant and for facilitating compatible surface tension between the layers, the method comprising the steps of,

[0045] (i) Providing a primer composition (a) and an active electrode composition (b);

[0046] (ii) Simultaneously or substantially simultaneously applying the primer composition (a) and the active electrode composition (b) onto the electrode metal foil, wherein the primer composition (a) forms a primer layer (A) directly on the surface of the electrode metal foil and the active electrode composition (b) forms an active electrode layer (B) directly on the surface of the primer layer (A) to form the multilayered coating on the electrode metal foil; andBASF SE 240343

[0047] (iii) drying the multilayered coating,

[0048] wherein the primer composition (a) comprises,

[0049] (I) at least one electro-conducting component comprising particulate carbon,

[0050] (II) at least one binder component,

[0051] (III) at least one co-binder component different from binder component (II), the co-binder being at least one polysaccharide or modified polysaccharide and

[0052] (IV) a dispersant component,

[0053] wherein the dispersant component (IV) comprises a polymer of N-vinylpyrrolidone, the polymer of N-vinylpyrrolidone being (i) a homopolymer of N-vinylpyrrolidone which exhibits a K value in the range from 10 to 70; or (ii) a random copolymer of N-vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer which exhibits a K value in the range from 10 to 70.

[0054] Detailed Description of the Invention

[0055] The primer composition (a) employed in the present invention comprises,

[0056] (I) at least one electro-conducting component comprising particulate carbon, (II) at least one binder component,

[0057] (III) at least one co-binder component different from binder component (II), the co-binder being at least one polysaccharide or modified polysaccharide, and

[0058] (IV) a dispersant component,

[0059] wherein the dispersant component (IV) comprises a polymer of N-vinylpyrrolidone, the polymer of N-vinylpyrrolidone being (i) a homopolymer of N-vinylpyrrolidone which exhibits a K value in the range from 10 to 70; or (ii) a random copolymer of N-vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer which exhibits a K value in the range from 10 to 70.BASF SE 240343

[0060] The electro-conducting component (I) comprises carbon in particulate form.

[0061] Typically, it may be selected from at least one of carbon black, nano carbon black, acetylene black, carbon fibre, multiwall carbon nanotubes, single walled carbon nanotubes, Ketien black, natural graphite, suitably at least one selected from the group of carbon black, nano carbon black, natural graphite and carbon nanotubes, preferably nano carbon black.

[0062] Suitably the particulate carbon contained in the electro-conducting component (I) may have a primary particle size of less than 100 nm, for instance less than 80 nm, typically less than 60 nm and frequently less than 50 nm. In addition, the particulate carbon desirably may have a BET specific surface area from 30 to 100 m2 / g, for instance from 40 to 80 m2 / g.

[0063] The electro-conducting component (I) may include other additives in addition to the carbon in particulate form. Generally, the carbon in particulate form should make up at least 80% by weight, preferably at least 90% by weight, more preferably at least 95% by weight, more preferably still at least 99% by weight, based on the total dry weight of the electro-conducting component (I).

[0064] Products suitable as electro-conducting components (I) are available commercially, for instance SUPER C65®, SUPER P®, ENSACO®, C-NERGY® product ranges available from Imerys, PBX® product range available from Cabot Specialty Chemicals, CONDUCTEX® and CB / CNT Hybrid® product ranges available from Birla Carbon, SMG-A5® available from Showa Denko.

[0065] Desirably the electro-conducting component (I) should form at least 25% by weight of the total dry weight of the primer composition (a), for instance from 25% to 60%, desirably from 25% to 50%, more desirably from 30% to 40% by weight.

[0066] The binder component (II) may include one or more polymeric materials typically employed as binders in formulations used in coatings for battery foils. Desirably the binder component (II) may include at least one synthetic polymer. Suitable synthetic polymers used for this purpose may be water insoluble or at least have hydrophobicBASF SE 240343

[0067] characteristics which can be imparted by hydrophobic and / or water insoluble monomers.

[0068] Desirably the at least one synthetic polymer may exhibit a degree of elasticity and / or exhibit tackiness characteristics. Suitable polymers may be formed from one or a mixture of ethylenically unsaturated monomers, for instance acrylonitrile, methacrylonitrile, styrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, sec-butyl acrylate 2-ethyl hexyl acrylate, cyclohexyl acrylate, isobornyl acrylate, hydroxy ethyl acrylate, hydroxypropyl acrylate, vinyl acetate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate sec-butyl methacrylate, tertbutyl methacrylate, 2-ethyl hexyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, pentyl acrylates, pentyl methacrylates, allyl esters of saturated carboxylic acids, allyl ethers, vinyl ethers, vinyl ketones, and dialkyl esters of ethylenically unsaturated dicarboxylic acids. Such monomers tend to have a hydrophobic characteristic. It may also be desirable to include at least one hydrophilic monomer into a monomer mixture that comprises hydrophobic monomers, for instance as described above.

[0069] Suitable hydrophilic monomers may include one or more of the ethylenically unsaturated monomers acrylic acid or a salt thereof, methacrylic acid or a salt thereof, allyloxyhydroxypropyl sulfonic acid or a salt thereof, vinyl sulfonic acid or salt thereof, 2-acrylamido-2-methylpropane sulfonic acid or salt thereof, allyl sulfonic acid or salt thereof, methylallyl sulfonic acid or a salt thereof, itaconic acid or salt thereof and maleic acid or salt thereof, vinylphosphonic acid or salt thereof, fumaric acid or salt thereof, crotonic acid or salt thereof, vinyl acetic acid or salt thereof, vinyl lactic acid or salt thereof, acrylamide, methacrylamide, hydroxyethyl acrylate,.

[0070] Desirably the polymer is a mixture of one or more hydrophobic monomers and one or more hydrophilic monomers. Such polymers may be prepared by polymerisation of the monomer or mixture of monomers in an organic solvent or an aqueous solvent. More desirably the polymers are prepared as an aqueous emulsion by aqueous emulsion polymerisation with the polymer contained in the dispersed phase.BASF SE 240343

[0071] Suitably the at least one binder component (II) is selected from at least one of the group of SBR (styrene butadiene rubber), at least one (meth) acrylic acid copolymer and at least one acrylonitrile copolymer, preferably at least one SBR (styrene butadiene rubber). Suitable polymers for use as binder component (II) are available commercially, for instance under the product name LICITY® from BASF.

[0072] Desirably the binder component (II) should be present in the primer composition (a) in an amount of at least 25% by dry weight of the total dry weight of the primer composition (a), for instance from 25% to 60%, desirably from 25% to 50%, more desirably from 30% to 40% by total dry weight of the primer composition (a).

[0073] The co-binder component (III) is at least one polysaccharide or modified polysaccharide. Examples of suitable polysaccharides or modified polysaccharides are selected from the group of methyl cellulose; hydroxy alkyl cellulose, for instance hydroxyethylcellulose (HEC); carboxymethylcellulose (CMC) or salts thereof; galactoglucomannan gum, for instance Konjac gum; xanthan gum. More preferably, the at least one polysaccharide or modified polysaccharide used as the co-binder component (III) is carboxymethylcellulose (CMC) or salts thereof and / or Konjac gum.

[0074] The primary function of the co-binder component (III) is to function as a binder in combination with the binder component (II). However, the co-binder component (III) may also contribute to dispersing the particulate carbon of the at least one electro conducting component (I). This is particularly so where the co-binder component (III) is hydrophilic and even more so when it is water-soluble.

[0075] The co-binder component (III) may have a water solubility at 25°C of at least 0.001 g / g de-ionised water, preferably at least 0.01 g / g, more preferably at least 0.02 g / g, particularly preferably at least 0.05 g / g.

[0076] Preferably, the co-binder component (III) is carboxymethylcellulose (CMC) having a water solubility at 25°C of at least 0.001 g / g deionised water, preferably at least 0.01 g / g, more preferably at least 0.02 g / g, particularly preferably at least 0.05 g / g.BASF SE 240343

[0077] Suitable polysaccharide or modified polysaccharide products for use as co-binder components (III) are available commercially, for instance the TEXTURECEL® product range available from IFF; carboxymethylcellulose (CMC) binder manufactured by Dai-lchi Kogyo SeiYaku, Japan; AkuPure product range available from Nouryon; and Konjac Gum Powder, available from Sarda Starch.

[0078] Desirably the co-binder component (III) should be present in the primer composition (a) in an amount of at least 20% by dry weight of the total dry weight of the primer composition (a), for instance from 20% to 50%, desirably from 25% to 45%, more desirably from 30% to 40% by dry weight based on the total dry weight of the primer composition (a).

[0079] The dispersant component (IV) comprises a polymer of N-vinylpyrrolidone. The polymer of N-vinylpyrrolidone may be a homopolymer of N-vinylpyrrolidone exhibiting a K value in the range from 10 to 70 or a random copolymer comprising N-vinylpyrrolidone, exhibiting a a value in the range from 10 to 70, for instance in an amount of at least 40 moles %, and at least one other monomer, for instance in an amount of up to 60 mol %. The polymer of N-vinylpyrrolidone may have a weight average molecular weight (Mw) of below 100,000 g / mol, suitably in the range from 4,000 to 80,000 g / mol. The weight average molecular weight (Mw) may be determined by size exclusion chromatography (SEC) also known as gel permutation chromatography (GPC).

[0080] In one embodiment the polymer of N-vinylpyrrolidone is a homopolymer of N-vinylpyrrolidone, suitably having a weight average molecular weight (Mw) in the range from 4,000 to 80,000 g / mol, preferably from 5,000 to 60,000 g / mol. The weight average molecular weight (Mw) may be determined by size exclusion chromatography (SEC) also known as gel permutation chromatography (GPC).

[0081] The homopolymer of N-vinylpyrrolidone exhibits a K value in the range from 10 to 70, suitably from 12 to 60, for instance from 12 to 50, preferably from 15 to 45 or from 15 to 40, such as from 15 to 25 or from 15 to 20. The K value is determined using the standard ISO 1628-1, 1% dry substance in distilled water.BASF SE 240343

[0082] The dispersant component (IV) may be a random copolymer of N-vinylpyrrolidone comprising at least one other monomer. Suitably the copolymer is a random copolymer of N-vinylpyrrolidone with at least one copolymerisable ethylenically unsaturated monomer. Typically, the at least one copolymerisable ethylenically unsaturated monomer is a non-ionic monomer, for instance selected from vinyl esters of saturated Ci to Cis carboxylic acids, preferably vinyl acetate, and esters of acrylic acid and methacrylic acid with monohydric Ci to Cis alcohols, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate, secbutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, pentyl acrylates, pentyl methacrylates, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, allyl esters of saturated carboxylic acids, vinyl ethers, vinyl ketones, dialkyl esters of ethylenically unsaturated carboxylic acids, N-vinyl formamide, N,N-dialkylaminoalkylacrylamides, N,N-dialkylaminoalkylmethacrylamides, N,N-dialkylaminoalkyl acrylates, N,N-dialkylaminoalkyl methacrylates, acrylamide, methacrylamide.

[0083] Suitably the random copolymer of N-vinylpyrrolidone and at least one ethylenically unsaturated copolymerisable monomer should contain at least 40 mol % of the N-vinylpyrrolidone monomer. Desirably the N-vinylpyrrolidone should be present in an amount of from 40 to 99.5 mol %, for instance from 50 to 95 mol %, such as from 55 to 90 mol % or from 55 to 85 mol %, preferably from 60 to 80 mol %, more preferably from 65 to 75 mol % and the ethylenically unsaturated copolymerisable monomer present in an amount of from 0.5 to 60 mole %, for instance from 5 to 50 mol %, such as from 10 to 45 mol %, preferably from 20 to 40 mol %, more preferably from 25 to 35 mol %. The molar amount of N-vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer combined should be 100%.

[0084] In one preferred embodiment the polymer of N-vinylpyrrolidone is a random copolymer of N-vinylpyrrolidone and vinyl acetate. Desirably the N-vinylpyrrolidone should be present in an amount of from 40 to 99.5 mol %, for instance from 50 to 95 mol %, such as from 55 to 90 mol % or from 55 to 85 mol %, preferably from 60 to 80 mol %, more preferably from 65 to 75 mol % and the vinyl acetate desirably should be present in an amount of from 0.5 to 60 mole %, for instance from 5 to 50 mol %,BASF SE 240343

[0085] such as from 10 to 45 mol %, preferably from 20 to 40 mol %, more preferably from 25 to 35 mol %. The molar amount of N-vinylpyrrolidone and vinyl acetate combined should be 100%.

[0086] When the polymer of N-vinylpyrrolidone is a random copolymer of N-vinylpyrrolidone with at least one copolymerisable ethylenically unsaturated monomer, suitably it may have a weight average molecular weight (Mw) in the range from 4,000 to 80,000 g / mol, for instance from 5,000 to 75,000 g / mol. In one preferred embodiment, the copolymer is a random copolymer of N-vinylpyrrolidone and vinyl acetate, more preferably a random copolymer comprising from 60 to 80 mol % N-vinylpyrrolidone and from 20 to 40 mol % vinyl acetate, particularly preferably having a weight average molecular weight (Mw) in the range from 40,000 to 75,000 g / mol. The weight average molecular weight (Mw) may be determined by size exclusion chromatography (SEC) also known as gel permutation chromatography (GPC).

[0087] The random copolymer of N-vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer exhibits a K value in the range from 10 to 70, suitably from 12 to 60, for instance from 15 to 50, preferably from 20 to 45 or from 20 to 40. The K value is determined using the standard ISO 1628-1 , 1% dry substance in distilled water.

[0088] The polymer (i.e. homopolymer or copolymer) of N-vinylpyrrolidone may be prepared by known methods described in the patent and literature. Suitably the polymer may be prepared by polymerising N-vinylpyrrolidone (as sole monomer in the case of the homopolymer and as a mixture with the at least one copolymerisable ethylenically unsaturated monomer in the case of the copolymer) in a suitable solvent in the presence of at least one free radical initiator, also referred to as free radical polymerisation initiators.

[0089] The free radical initiators used in the polymerisation process form free radicals under the reaction conditions. Typically, free radical initiators suitable for preparing the polymer of N-vinylpyrrolidone include oxidising agents, such as peroxides, or thermal initiators, for instance azo compounds, or redox initiator systems.BASF SE 240343

[0090] Peroxides used may in principle be inorganic peroxides and / or organic peroxides. Examples of suitable inorganic peroxides include hydrogen peroxide and peroxodisulfates, such as the mono- or di- alkali metal or ammonium salts of peroxodisulfuric acid, for example the mono- and disodium, mono- and dipotassium, or ammonium salts thereof. Examples of suitable organic peroxides are alkyl hydroperoxides, such as tert-butyl hydroperoxide, aryl hydroperoxides, such as p-menthyl or cumene hydroperoxide, and dialkyl or diaryl peroxides such as di-tert-butyl, dibenzoyl or dicumene peroxide.

[0091] Azo compounds used are essentially 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(N,N'-dimethyleneisobutyroamidine) dihydrochloride and 2,2'-azobis(amidinopropyl) dihydrochloride (AIBA, corresponding to V-50 from Wako Chemicals).

[0092] Redox initiator systems are combined systems made up of at least one organic or inorganic reducing agent and at least one peroxide. Suitable oxidants for redox initiator systems are essentially the peroxides mentioned above. Corresponding reducing agents that may be used are sulfur compounds in a low oxidation state such as alkali metal sulfites, for example potassium and / or sodium sulfite, alkali metal hydrogen sulfites, for example potassium and / or sodium hydrogen sulfite, alkali metal metabisulfites, for example potassium and / or sodium metabisulfite, acetone bisulfite, formaldehyde sulfoxylates, for example potassium and / or sodium formaldehyde sulfoxylate, alkali metal salts, specifically potassium and / or sodium salts of aliphatic sulfinic acids and alkali metal hydrogen sulfides, for example potassium and / or sodium hydrogen sulfide, salts of polyvalent metals, such as iron(ll) sulfate, iron(ll) ammonium sulfate, iron(ll) phosphate, enediols, such as dihydroxymaleic acid, benzoin and / or ascorbic acid, and reducing saccharides, such as sorbose, glucose, fructose and / or dihydroxyacetone.

[0093] Preferred free-radical initiators are inorganic and organic peroxides, preferably ammonium or alkali metal salts of peroxosulfates or peroxodisulfates, and tert-butyl, p-menthyl and cumyl hydroperoxide, in particular selected from sodium and potassium peroxodisulfate, tert-butyl hydroperoxide and cumyl hydroperoxide.

[0094] Preference is given here to using both at least one inorganic peroxide, preferablyBASF SE 240343

[0095] peroxodisulfate, in particular sodium peroxodisulfate, and / or one organic peroxide, preferably alkyl hydroperoxide, in particular t-butyl hydroperoxide.

[0096] The polymerization is generally carried out using 0.1 to 5 parts by weight of the free-radical initiator, preferably 0.5 to 4 parts by weight of the free-radical initiator, based on 100 parts by weight of total monomers.

[0097] Initiation of the polymerization reaction is understood to mean the start of the polymerization reaction of the monomers present in the polymerization vessel as a result of decomposition of the free-radical initiator.

[0098] Typically, it may be desirable to employ chain regulators (also known as chain transfer agents) in the polymerisation process, for instance to control the molecular weight of the resulting polymer. Examples of typical chain regulators used are frequently inorganic sulfur compounds such as hydrogen sulfites, disulfites and dithionites, organic sulfides, sulfoxides, sulfones and mercapto compounds, such as mercapto ethanol, mercapto acetic acid. Particularly suitable chain regulators include inorganic phosphorus compounds, such as hypophosphorous acid (phosphinic acid) and its salts, for instance sodium hypophosphite.

[0099] The polymerisation should be carried out in a suitable solvent, typically water or an aqueous solvent containing water and a cosolvent. Suitably the N-vinylpyrrolidone or monomer mixture comprising N-vinylpyrrolidone should be dissolved in the solvent and polymerised as an aqueous solution of monomer. Further, the so formed polymer of N-vinylpyrrolidone resulting from the polymerisation process should also be formed as a solution in the solvent, preferably as an aqueous solution.

[0100] The polymerisation process may be carried out in batch mode, fed batch mode, or as a continuous process.

[0101] It may be desirable to start the polymerisation process with all of the monomer, initiators and where used chain regulator as in the case of a batch process or it may be desirable to have a pre-charge of a portion of the monomer and / or initiators and / or where employed chain regulator and then during the process employ aBASF SE 240343

[0102] continuous feed of monomer and / or initiators and / or where employed chain regulator.

[0103] The polymer of N-vinylpyrrolidone may also be provided as a solid, for instance as a dry powder. This may be achieved by dehydrating an aqueous solution of the polymer of N-vinylpyrrolidone, for instance by spray drying. Alternatively, it may be desirable to provide the polymer of N-vinylpyrrolidone in solid form, for instance as a dry powder, by producing the polymer by precipitation polymerisation, for instance by employing a solvent in which the monomer or monomer mixture is soluble but in which the polymer is insoluble and thus precipitates form a particulate solid which can be dried to remove residual water and solvent.

[0104] An alternative way of preparing the polymer of N-vinylpyrrolidone in solid form includes conducting a suspension polymerisation process, for instance in which an aqueous solution of the monomer or monomer mixture as droplets is suspended in a water immiscible solvent in a stirred reactor. During the polymerisation process the polymerising monomer or monomer mixture forms solid particles of the polymer which can be dried to remove additional water and solvent.

[0105] Polymers of N-vinylpyrrolidone suitable for the invention are available commercially, for instance the SOKALAN® K or LUVISKOL® VA product ranges, available from BASF.

[0106] The polymers of N-vinylpyrrolidone suitable for the invention described herein are preferably water-soluble. Typically, these polymers will have a solubility in deionised water of at least 5 g of the polymer in 100 ml at 25°C. Suitably the water solubility is considerably higher, for instance at least 10 g, preferably at least 20 g, of polymer in 100 ml deionised water at 25°C.

[0107] The polymers of N-vinylpyrrolidone suitable for the invention described herein are suitably substantially linear polymers. By substantially linear we mean that the polymers are wholly linear or contain a minimal level of polymer chain structuring, for instance less than 2% structuring, preferably less than 1% structuring. Particularly preferably the polymers of N-vinylpyrrolidone are not cross-linked. Preferably theBASF SE 240343

[0108] polymers of N-vinylpyrrolidone are wholly linear. Preferably the polymers of N-vinylpyrrolidone are produced in the absence of cross-linking agent, branching agent or other polymer chain structuring agent.

[0109] It may be desirable for the polymer of N vinylpyrrolidone to be a mixture of a homopolymer of N-vinylpyrrolidone, as described herein, and a random copolymer of N-vinylpyrrolidone with a copolymerisable ethylenically unsaturated monomer, as described herein. Preferably such a mixture may be a homopolymer of N-vinylpyrrolidone, according to any of the aforementioned embodiments, and a copolymer of N-vinylpyrrolidone and vinyl acetate, as described herein.

[0110] Desirably the dispersant component (IV) should be present in the primer composition (a) in an amount of at least 0.1 % by dry weight of the total dry weight of the primer composition (a), for instance from 0.1% to 10%, desirably from 0.5% to 5%, more desirably from 1 % to 3% by dry weight based on the total dry weight of the primer composition (a).

[0111] The primer composition (a) comprises the components (I), (II), (III) and (IV) and is typically produced as a slurry in a liquid medium. The liquid medium is typically an aqueous liquid, comprising water and optionally one or more cosolvents. Suitable cosolvents include polar organic solvents, for instance C1-C5 alcohols, preferably ethanol. Other polar organic solvents may be used provided they are sufficiently soluble or miscible with water and do not phase separate. Generally, such cosolvents, if present at all, should be present in the water as a minor component, for instance from 0.5 to 3 ppm, by weight of the water present in the active electrode composition (b).

[0112] The solids content of the primer composition (a) is typically up to 10%, for instance from 0.5% to 10%, suitably from 0.5% to 5%, preferably from 1% to 3.5%, by weight based on the total weight of the primer composition (a), the remainder made up of water. Suitably the amount of liquid medium, typically water, optionally with cosolvent, in the primer composition (a) may range from at least 90%, for instance from 90% to 99.5%, suitably from 95% to 99.5%, preferably from 96.5 to 99%, by weight based on the total weight of the primer composition (a).BASF SE 240343

[0113] The primer composition (a) typically exhibits a viscosity of from 0.5 to 10 Pa*s, for instance from 1 to 10 Pa*s, for instance at shear rates from 10 s-1to 1000 s-1, such as from 10 s-1to 100 s-1. Preferably the viscosity of the primer composition (a) should substantially match the viscosity of the active electrode composition (b) at shear rates ranging from 10 s-1to 1000 s-1. By substantially match we mean that the viscosities may be the same or different by up to 10%, preferably up to 5%, more preferably up to 1 %. It is therefore particularly desirable that the viscosity of the primer composition (a) should substantially match the viscosity of the active electrode composition (b) during the multilayer coating process and especially under the process conditions and at the shear rates encountered during the multilayer coating operation. The viscosity of the primer composition (a) may be adjusted where necessary more closely match the viscosity of the active electrode composition (b) by the addition of additives that increase the viscosity, for instance viscosifying agents. The addition of co-binder, for instance when the co-binder is carboxymethyl cellulose (CMC), may achieve an increase in viscosity of the primer composition (a). Desirably the use of polysaccharide gums may be used to achieve an increase in the viscosity, where necessary. For instance, polysaccharide gums, such as Konjac gum, Xanthan gum, Guar gum, locust bean gum, or Carrageenan may be employed to increase the viscosity of the primer composition (a).

[0114] The primer composition (a) may be prepared by a method comprising combining components (I), (II), (III) and (IV) with liquid medium, suitably water and optionally cosolvent. Typically, the at least one co-binder component (III) and the dispersant component (IV) may be introduced into the liquid medium, typically water and optionally cosolvent, either sequentially or simultaneously followed by introducing the at least one electro-conducting component (I). When the components (III) and (IV) are introduced into the liquid medium, typically water and optionally cosolvent, sequentially the exact order does not particularly matter. Suitably, the components (III) and (IV) should be introduced into the liquid medium, typically water and optionally cosolvent, under stirring or other agitation to ensure the components are fully dispersed and / or dissolved throughout the water form a liquid medium, typically aqueous liquid medium. Further, desirably the at least one electro conducting component (I) should be introduced into the liquid medium, the aqueous liquidBASF SE 240343

[0115] medium, comprising the components (III) and (IV) under stirring or other agitation to ensure even distribution throughout the water-based liquid medium in order to form the primer composition (a). It may be desirable to introduce the at least one electro conducting component (I) into the liquid medium, typically aqueous liquid medium, over a period of time at a steady rate to facilitate efficient distribution of the solid particles and avoid the risk of particles clumping or otherwise forming aggregates. Finally, the binder component (II) should be introduced into the liquid medium.

[0116] Suitably the binder component (II) may be introduced into the liquid medium at a lower level of shear (e.g. reduced stirring or other agitation) than employed for introducing the electro conductive component (I) into the liquid medium.

[0117] In one preferred embodiment, the primer composition (a) comprises carbon black as component (I), and SBR resin as component (II), and carboxy methyl cellulose (CMC) in addition to Konjac gum as components (III), and either N-vinylpyrrolidone homopolymer or the copolymer of N-vinylpyrrolidone with vinyl acetate as component (IV). Preferably molar ratio of N-vinylpyrrolidone with vinyl acetate lies in the range from 60:40 to 80:20, more preferably 65:35 to 75:25. More preferably, in this embodiment the N-vinylpyrrolidone homopolymer and the copolymer of N-vinylpyrrolidone with vinyl acetate exhibit K values in the range from 10 to 40.

[0118] The active electrode composition (b) typically comprises optionally at least one electro conducting particulate material (bl), a binder component (bl I), a co-binder component (bill) which is different from binder component (bl I) and an electro-active component (bV).

[0119] The at least one electro conducting material (bl) may comprise any conducting particulate material but suitably comprises carbon. Desirably, the electro-conducting material (bl) may be one or more of the materials selected from carbon black, nano carbon black, acetylene black, carbon fibre, multiwall carbon nanotubes, single walled carbon nanotubes, Ketien black, natural graphite or artificial graphite.

[0120] Desirably, the electro-conducting material (bl) comprises particulate carbon and more desirably is selected from at least one of carbon black, nano carbon black, acetylene black, carbon fibre, multiwall carbon nanotubes, single walled carbon nanotubes, Ketien black, artificial graphite or natural graphite. Preferably the electro conducting material (bl) is at least one selected from the group of carbon black, nanoBASF SE 240343

[0121] carbon black and carbon nanotubes, more preferably nano carbon black. It may be desirable to use a combination of two or more electro conducting materials, currently two or more electro conducting materials comprising particulate carbon, especially two or more materials selected from carbon black, nano carbon black, natural graphite, synthetic graphite and carbon nanotubes.

[0122] Suitably the particulate carbon contained in the electro-conducting material (bl) may have a primary particle size of less than 100 nm, for instance less than 80 nm, typically less than 60 nm and frequently less than 50 nm. In addition, the particulate carbon desirably may have a BET specific surface area from 30 to 100 m2 / g, for instance from 40 to 80 m2 / g.

[0123] The electro-conducting material (bl) may include other additives in addition to the carbon in particulate form. Generally, the carbon in particulate form should make up at least 80% by weight, preferably at least 90% by weight, more preferably at least 95% by weight, more preferably still at least 99% by weight, based on the total dry weight of the electro-conducting material (bl). More preferably still, the electro conducting material (bl) comprises substantially entirely particulate carbon, for instance 100% by weight particulate carbon, based on the total dry weight of the electro conducting material (bl).

[0124] Products suitable as electro-conducting components (bl) are available commercially, for instance SUPER C65®, SUPER P®, ENSACO®, C-NERGY® product ranges available from Imerys, PBX® product range available from Cabot Specialty Chemicals, CONDUCTEX® and CB / CNT Hybrid® product ranges available from Birla Carbon, SMG-A5® available from Showa Denko.

[0125] The optional active electrode composition (b) when present tends to comprise a lower concentration of electro-conducting material than the primer composition (a). Typically, the concentration of electro-conducting material (bl) should be up to 2%, for instance from 0.01 % to 2%, desirably from 0.1 % to 1.75%, such as from 0.5% to 1.5%, by weight of the total dry weight of the active electrode composition (b).BASF SE 240343

[0126] The binder component (bl I) may include one or more polymeric materials typically employed as binders in formulations used in coatings for battery foils. Desirably the binder component (bl I) may include at least one synthetic polymer. Suitable synthetic polymers used for this purpose may be water insoluble or at least have hydrophobic characteristics which can be imparted by hydrophobic and / or water insoluble monomers.

[0127] Desirably the at least one synthetic polymer may exhibit a degree of elasticity and / or exhibit tackiness characteristics. Suitable polymers may be formed from one or a mixture of ethylenically unsaturated monomers, for instance acrylonitrile, methacrylonitrile, styrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, sec-butyl acrylate 2-ethyl hexyl acrylate, cyclohexyl acrylate, isobornyl acrylate, hydroxy ethyl acrylate, hydroxypropyl acrylate, vinyl acetate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate sec-butyl methacrylate, tertbutyl methacrylate, 2-ethyl hexyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, pentyl acrylates, pentyl methacrylates, allyl esters of saturated carboxylic acids, allyl ethers, vinyl ethers, vinyl ketones, and dialkyl esters of ethylenically unsaturated dicarboxylic acids. Such monomers tend to have a hydrophobic characteristic. It may also be desirable to include at least one hydrophilic monomer into a monomer mixture that comprises hydrophobic monomers, for instance as described above.

[0128] Suitable hydrophilic monomers may include one or more of the ethylenically unsaturated monomers acrylic acid or a salt thereof, methacrylic acid or a salt thereof, allyloxyhydroxypropyl sulfonic acid or a salt thereof, vinyl sulfonic acid or salt thereof, 2-acrylamido-2-methylpropane sulfonic acid or salt thereof, allyl sulfonic acid or salt thereof, methylallyl sulfonic acid or a salt thereof, itaconic acid or salt thereof and maleic acid or salt thereof, vinylphosphonic acid or salt thereof, fumaric acid or salt thereof, crotonic acid or salt thereof, vinyl acetic acid or salt thereof, vinyl lactic acid or salt thereof, acrylamide, methacrylamide and 2-hydroxyethyl acrylate.

[0129] Desirably the polymer is a mixture of one or more hydrophobic monomers and one or more hydrophilic monomers. Such polymers may be prepared by polymerisation of the monomer or mixture of monomers in an organic solvent or an aqueousBASF SE 240343

[0130] solvent. More desirably the polymers are prepared as an aqueous emulsion by aqueous emulsion polymerisation with the polymer contained in the dispersed phase.

[0131] Suitably the at least one binder component (bl I) is selected from at least one of the group of SBR (styrene butadiene rubber), at least one (meth) acrylic acid copolymer and at least one acrylonitrile copolymer, preferably at least one SBR (styrene butadiene rubber). Suitable polymers for use as binder component (bl I) are available commercially, for instance under the product name LICITY® from BASF.

[0132] Desirably the binder component (bl I) should be present in the active electrode composition (b) in an amount of at least 0.5% by dry weight of the total dry weight of the active electrode composition (b), for instance from 0.5 % to 4%, desirably from 1 % to 3%, more desirably from 1 % to 2% by total dry weight of the active electrode composition (b).

[0133] The co-binder component (bill) is different from binder component (bl I). The cobinder component (bill) may comprise at least one synthetic binder material which is different from binder component (bl I) and / or the co-binder component (bill) may be at least one polysaccharide or modified polysaccharide. In general, the co-binder component (bill) would tend to be a hydrophilic polymer or even a water-soluble polymer, and typically more hydrophilic than the binder component (bl I).

[0134] Examples of suitable synthetic polymers that can be used as the co-binder component (bill) include polyvinyl alcohol; polyvinyl pyridine; polyvinylpyrrolidone; hydrophilic copolymers of acrylic acid and acrylic esters, for instance anionic hydrophobically modified alkali soluble associative and non-associative polymers for modifying the rheology of water-based systems; non-ionic associative hydrophobically ethoxylated urethane polymers. Suitable commercially available synthetic polymers suitable as the co-binder component (bill) include the RHEOVIS® and STEROCOLL® product ranges available from BASF.

[0135] Preferably the co-binder component (bill) is at least one polysaccharide or modified polysaccharide. Examples of suitable polysaccharides or modified polysaccharidesBASF SE 240343

[0136] are selected from the group of methylcellulose; hydroxy alkyl cellulose, for instance hydroxyethylcellulose (HEC); carboxymethylcellulose (CMC) or salts thereof; galactoglucomannan gum, for instance Konjac gum; xanthan gum. More preferably, the at least one polysaccharide or modified polysaccharide used as the co-binder component (bill) is carboxymethylcellulose (CMC) or salts thereof and / or Konjac gum.

[0137] The primary function of the co-binder component (bill) is to function as a binder in combination with the binder component (bl I). However, the co-binder component (bill) may also contribute to dispersing the particulate carbon of the at least one electro conducting material (bl) or thickening (i.e viscosifying) the active electrode composition (b). This is particularly so where the co-binder component (bill) is hydrophilic and even more so when it is water-soluble.

[0138] Suitable polysaccharide or modified polysaccharide products for use as co-binder components (bill) are available commercially, for instance the TEXTURECEL® product range available from IFF; carboxy methyl Cellulose (CMC) Binder manufactured by Dai-lchi Kogyo SeiYaku, Japan; AkuPure product range available from Nouryon; and Konjac Gum Powder, available from Sarda Starch.

[0139] Desirably the co-binder component (bill) should be present in the active electrode composition (b) in an amount of at least 0.5% by dry weight of the total dry weight of the active electrode composition (b), for instance from 0.5% to 3%, desirably from 1 % to 3%, more desirably from 1 % to 2% by dry weight based on the total dry weight of the active electrode composition (b).

[0140] The electro-active component (bV) may typically be a material capable of storing electrical energy. When the electrode is an anode the electro-active component (bV) may be any anode active material which may be any material capable of intercalating lithium and de-intercalating lithium. Preferred anode active materials, useful as the electro-active component (bV), include any of the group selected from graphite, including natural graphite, synthetic graphite and fibre graphite, silicon, silicon oxide, silicon carbon composite, tin, lithium, aluminium, lithium titanium oxide and lithium silicon. More preferred are graphite, for example natural graphite,BASF SE 240343

[0141] synthetic graphite or fibre graphite, silicon, silicon oxide and silicon carbon composites. Particularly preferred is graphite, for example natural graphite, synthetic graphite or fibre graphite.

[0142] Anode active materials, suitable as the electro-active component (bV) for available commercially, for instance SMG-A5® available from Showa Denko.

[0143] When the electrode is a cathode, the electroactive component the electro-active component (bV) may be any cathode active material, suitably which may be capable of intercalating lithium and de-intercalating lithium. Suitable examples of cathode active material, suitable as the electro-active component (bV), may include a lithiummanganese oxide, a lithium-cobalt oxide, a lithium-nickel oxide a lithium-iron oxide, and a combination thereof. Other examples of cathode active material include nickel cobalt aluminium (NCA) and nickel cobalt manganese (NCM or NMC). Such cathode active materials are described, for example in WO 2021 / 078626.

[0144] The amount of electro-active component (bV) present in the active electrode composition (b), for example when the electro-active component (b) is an anode active material or a cathode active material, preferably an anode active material, suitably is in the range from 50% to 98 weight %, preferably from 75% to 98 weight %, for instance from 90 weight % to 97.5 weight %, desirably from 92 weight % to 97 weight %, by weight of the total dry weight of the active electrode composition (b).

[0145] The particle size of the electro-active component (bV) may typically be less than 30 pm, suitably less than 25 pm, for instance in the range from 0.5 to 25 pm. It may be desirable for the particle size to range from 0.5 to 1 pm, for instance 0.5 to 0.8 pm. Alternatively, it may be desirable for the particle size to range from 5 pm to 20 pm, for instance 10 pm to 20 pm.

[0146] The active electrode composition (b) comprises the components (bl), (bl I), (bill) and (bV) and is typically produced as a slurry in a liquid medium. The liquid medium is typically an aqueous liquid, comprising water and optionally one or more co-solvents. Suitable co-solvents include polar organic solvents, for instance C1-C5 alcohols,BASF SE 240343

[0147] preferably ethanol. Generally, such co-solvents, if present at all, should be present in the water as a minor component, for instance from 0.5 to 3 ppm, by weight of the water present in the active electrode composition (b).

[0148] The solids content of the active electrode composition (b) is typically up to 70%, for instance from 40% to 70%, preferably from 45% to 60%, by weight based on the total weight of the active electrode composition (b), the remainder made up of liquid medium, typically water and optionally co-solvent. Suitably the amount of water in the active electrode composition (b) may range from at least 30%, for instance from 30% to 60%, preferably from 40% to 55%, by weight based on the total weight of the active electrode composition (b). The active electrode composition (b) typically exhibits a viscosity of from 0.5 to 10 Pa*s, for instance from 1 to 10 Pa*s, for instance at shear rates from 10 s-1to 1000 s-1, such as from 10 s-1to 100 s-1.

[0149] The active electrode composition (b) may be prepared by a method comprising combining component (bill) with the liquid medium, suitably water and optionally cosolvent. Typically, at least one co-binder component (bill) may be introduced into liquid medium, suitably water and optionally cosolvent, either sequentially or simultaneously followed by introducing the at least one electro-conducting material (bl). Desirably, the component (bill) should be introduced into the liquid medium, typically water, optionally with cosolvent, with stirring or other agitation to ensure the components are fully dispersed and / or dissolved throughout the liquid medium, typically aqueous liquid medium. Further, desirably the at least one electro-active component (bV) and (where included) optional at least one electro- conducting material (bl) should be introduced into the liquid medium, typically aqueous liquid medium, comprising the component (bill) under stirring or other agitation to ensure even distribution throughout the water-based liquid medium. Finally, the binder component (bl I) should be added into the water-based liquid medium in order to form the active electrode composition (b). Suitably the binder component (bl I) may be introduced into the liquid medium at a lower level of shear (e.g. reduced stirring or other agitation) than employed for introducing the electro-active component (bV) and (where included) the optional electro-conductive component (bl) into the liquid medium. It may be desirable to introduce the electro-active component (bV) and (where included) the optional at least one electro conducting component (bl) into theBASF SE 240343

[0150] liquid medium, typically aqueous liquid medium, over a period of time at a steady rate to facilitate efficient distribution of the solid particles and avoid the risk of particles clumping or otherwise forming aggregates.

[0151] The method of forming a multilayered coating on an electrode, preferably anode, metal foil comprises applying the primer composition (a) and the active electrode composition (b) simultaneously or substantially simultaneously. The primer composition (a) should form a primer layer (A) directly on the surface of the electrode metal foil and the active electrode composition (b) should form an active electrode layer (B) directly on the surface of the primer layer (A) thereby forming a multilayered coating on the electrode metal foil. Thus, the primer layer (A) should be in communication with the surface of the electrode metal foil and the active electrode layer (B).

[0152] Applying the primer composition (a) and the active electrode composition (b) substantially simultaneously means applying the active electrode composition (b) on top of the primer layer (A) within a short period of time of applying the primer composition (a). Typically, this would be before the primer layer (A) has dried and normally this would be within a few minutes, for instance within 10 minutes, suitably within 5 minutes, desirably within 1 minute and normally within 30 seconds of applying the primer composition (a).

[0153] The primer composition (a) and the active electrode composition (b) should preferably be applied to the electrode metal foil simultaneously meaning essentially at the same time and / or as part of the same coating operation.

[0154] Preferably the primer composition (a) and the active electrode composition (b) should be applied to the electrode metal foil using any of the techniques including slide bead coating, slide curtain coating, slot bead coating, slot curtain coating or tensioned web coating. When these techniques are used for multi-layer coating of the primer composition (a) and the active electrode composition (b) the two compositions are applied simultaneously. More preferably the primer composition (a) and the active electrode composition (b) are applied using a multi-layer slot die, for instance a two-layer slot die.BASF SE 240343

[0155] The method of forming a multilayered coating according to the present invention has been found to overcome the problem of incompatibility of surface tension of the primer composition (a) and the primer layer (A) particularly as regards the electrode active composition (b) and the electrode active layer (B).

[0156] Once the multilayered coating comprising the primer layer (A) and the active electrode layer (B) has been applied to the electrode metal foil, the multilayered coating should then be dried. The primer layer (A) and the active electrode layer (B) should be dried at the same time. The drying may comprise one or several drying steps conducted at a temperature from 20 to 300°C, preferably at a temperature from 50 to 150°C. The drying step causes removal of the liquid medium of the primer layer (A) and the liquid medium of the active electrode layer (B). The multilayered coating may be dried until weight constancy is achieved. Conventional drying techniques for drying of electrode metal foil coatings may be employed. For instance, the multilayered coated metal foil may be passed below an impingement dryer.

[0157] Typically, a plate may be moved cyclically back and forth to obtain homogenous drying conditions until the multilayered coating has been dried.

[0158] The primer layer (A) may have an area weight from 0.5 to 5 g / m2, preferably from 0.5 to 4 g / m2, more preferably from 0.5 to 3 g / m2, still more preferably from 1 to 2 g / m2, based on the dry weight of the primer layer (A) on the area of the electrode metal foil. Typically, the primer layer (A) may have a dry thickness from 0.1 to 10 pm, for instance from 0.25 to 5 pm, suitably from 0.5 to 4 pm, desirably from 1 to 3 pm.

[0159] The primer layer (A) according to the present invention has been found to exhibit high peel force strength. Desirably the primer layer (A) exhibits a peel force strength of at least 5 N / m, such as at least 8 N / m, for instance at least 10 N / m, more desirably at least 12 N / m, preferably at least 13 N / m and more preferably at least 14 N / m. The peel force strength may be significantly higher, for instance up to 19 N / m or up to 20 N / m or higher. Peel force strength is measured using a 90° peel test.

[0160] The active electrode layer (B) may have an area weight ranging from 10 g / m2to 300 g / m2, preferably 25 g / m2to 200 g / m2, measured as a dry weight of active electrodeBASF SE 240343

[0161] layer (B) on the area of electrode metal foil. Typically, the active electrode layer (B) may have a dry thickness from 10 pm to 300 pm, preferably 20 pm to 250 pm, more preferably from 25 pm to 200 pm.

[0162] Suitably, the electrode metal foil is a foil formed from copper, gold, nickel, aluminium, copper-containing alloy, or a combination thereof. Desirably electrode metal foil is obtained from either copper or aluminium, preferably copper. Preferably, in accordance with the present invention and all the preferred embodiments, the electrode metal foil is an anode metal foil. Preferably the anode metal foil is formed from copper.

[0163] In a further embodiment, the electrode metal foil may be a cathode metal foil, desirably formed from aluminium.

[0164] The electrode metal foil, preferably anode metal foil, may have a thickness of at least 4 pm, for instance at least 5 pm, suitably from 6 to 15 pm, such as from 7 to 15 pm, for instance from 8 to 15 pm.

[0165] Suitably the dried multilayered coated metal foil may be molded. Molding may be done according to conventional methods known in the art. Non-limiting examples for molding devices employed to achieve molding include calenders or pressing devices.

[0166] As used herein, the term “molded metal foil” means a dried multilayered coated metal foil, which has been molded. The molded metal foil may have pores within its structure, for instance having a porosity from 10 to 60%, suitably from 30 to 50%. The presence of such pores may be helpful in certain cases to absorb and / or reduce any expansion or contraction of the negative electrode active during charging and discharging. In such cases, this may help the negative electrode retain its shape. The porosity can be controlled by changing the conditions for producing the molded metal foil. When producing the molded metal foil by applying pressure onto the dried multilayered coated collector for example, the compression force can be adjusted to control the porosity. The porosity can be calculated using a volume Vi determinedBASF SE 240343

[0167] from the size of the resulting molded metal foil and an absolute volume Vo of the moulded metal foil, which can be represented by the formula

[0168] {(Vi-V0) / Vi} x 100(%)

[0169] The multilayered coated electrode metal foil produced according to the method of the present invention, for instance including the molded metal foil, may typically be incorporated into a secondary battery i.e. rechargeable battery, in particular a lithium-ion battery. Typically, the multilayered coated electrode metal foil would be used as either the anode metal foil or cathode metal foil, but preferably as the anode metal foil. Suitably, the multilayered coated electrode metal foil would be mounted into the secondary battery as the current collector such that the multilayered coated surface of the metal foil would be in contact with the electrolyte of the battery electrochemical cell.

[0170] Generally, the electrochemical cell of the secondary battery, particularly lithium-ion battery, in which the multilayered coated electrode metal foil according to the present invention may be employed would comprise a cathode and an anode each of which will be separated by a porous separator. The anode metal foil would form the outer boundary of the anode, and the cathode metal foil would form the outer boundary of the cathode, and the inventive multilayered coated elected foil may be used as either anode metal foil or cathode metal foil or both but preferably is used as the anode metal foil. Desirably the anode may consist of lithium-carbon (e.g. graphite) in an electrolyte, and the cathode may consist of lithium metal oxide (e.g. transition metal oxide) in an electrolyte.

[0171] A separator which may be used in secondary battery includes any one which has been conventionally used in the art for example porous membranes or non-woven fabrics made of polyolefin-based polymer and are described, for example, in WO 2021 / 078626, page 10. The separator may preferably have but not be limited to a thickness of 5 to 50 pm. Also, the separator may have but not be limited to a pore size of 30 - 750 nm and a porosity of 10 to 95%.BASF SE 240343

[0172] In order to improve the mechanical strength of the separator and the safety of the secondary battery, a porous coating layer comprising inorganic particles, and a polymer binder may be further formed on at least one surface of the separator. The inorganic particles are not particularly limited if they are electrochemically stable. Electrochemically stable in this context means no oxidation-reduction reaction occurs in an operating voltage range of an applied secondary battery (e.g. 0 to 5V based on Li / Li+).

[0173] Further, a secondary battery is provided comprising a cathode, an anode on either or both, preferably an anode, comprising the multilayered coated metal foil according to the invention, a separator interposed between the cathode and the anode, and a non-aqueous electrolyte. In particular, among the secondary batteries, lithium secondary batteries including a lithium metal secondary battery, a lithium-ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery are preferred.

[0174] Assembling can be done by laminating, stacking or folding of a separator and an electrode, as well as a winding process. The resulting assembly is rolled or bent in accordance with the shape of a battery and put into a battery container, an electrolyte solution is injected into the battery container, and the battery container is sealed up. Also, the secondary battery is not limited to its shape. For example, the shape of the battery may be like a coin, button or pouch, cylindrical, prismatic square or flat. Also, the secondary battery is not limited to its shape.

[0175] The electrolyte solution used in the present disclosure comprises a lithium salt as an electrolyte salt. The lithium salt may be any one which is conventionally used in an electrolyte solution for a lithium secondary battery. Examples of suitable lithium salts are LiPFe, LiBF4, LiCIC , LiAsFe, LiCFsSOs, LiC(CnF2n+iSO2)3, lithium imides such as LiN(CnF2n+iSO2)2, where n is an integer in the range from 1 to 20, LiN(SO2F)2, Li2SiFe, LiSbFe, LiAICU and salts of the general formula (CnF2n+iSO2)tYLi, where t is defined as follows:

[0176] t = 1 , when Y is selected from among oxygen and sulfur,

[0177] t = 2, when Y is selected from among nitrogen and phosphorus, and

[0178] t = 3, when Y is selected from among carbon and silicon.BASF SE 240343

[0179] Preferred electrolyte salts are selected from among LiC(CF3SO2)3, LiN(CF3SO2)2, LiPFe, LiBF4, LiCIC , with particular preference being given to LiPFe and LiN(CF3SO2)2.

[0180] The electrolyte solution used in the present disclosure comprises an organic solvent which is conventionally used in an electrolyte solution for a lithium secondary battery. For example, solvents for electrolytes can be liquid or solid at room temperature and is preferably selected from cyclic or acyclic ethers, cyclic and acyclic acetals and cyclic or acyclic organic carbonates.

[0181] Additionally, the electrolyte solution may comprise thickeners like polyalkylene glycols, preferably poly-Ci-C4-alkylene glycols and in particular polyethylene glycols. Polyethylene glycols can comprise up to 20 mol% of one or more Ci-C4-alkylene glycols. Polyalkylene glycols are preferably polyalkylene glycols having two methyl or ethyl end caps.

[0182] The molecular weight Mwof suitable polyalkylene glycols and in particular suitable polyethylene glycols can be at least 400 g / mol. The molecular weight Mwof suitable polyalkylene glycols and in particular suitable polyethylene glycols can be up to 5 000000 g / mol, preferably up to 2000000 g / mol.

[0183] Examples of suitable acyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1 ,2-dimethoxyethane, 1 ,2-diethoxyethane, with preference being given to 1 ,2-dimethoxyethane.

[0184] Examples of suitable cyclic ethers are tetrahydrofuran and 1 ,4-dioxane.

[0185] Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1 ,1 -dimethoxyethane and 1 ,1 -diethoxyethane.

[0186] Examples of suitable cyclic acetals are 1 ,3-dioxane and in particular 1 ,3-dioxolane.BASF SE 240343

[0187] Examples of suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

[0188] Examples of suitable cyclic organic carbonates are compounds according to the general formulae (Fl) and (Fll)

[0189] (Fl)

[0190] (Fll)

[0191]

[0192] where R1, R2and R3can be identical or different and are selected from among hydrogen and Ci-C4-alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, with R2and R3preferably not both being tert-butyl.

[0193] Particularly preferred embodiments, R1is methyl and R2and R3are each hydrogen, or R1, R2and R3are each hydrogen.

[0194] Another preferred cyclic organic carbonate is vinylene carbonate, formula (Fill).

[0195]

[0196] The solvent or solvents is / are preferably used in the water-free state, i.e. with a water content in the range from 1 ppm to 0.1% by weight, which can be determined, for example, by Karl-Fischer titration.

[0197] Suitable uses of batteries employing the multilayered coated metal foils according to the present invention include a variety of mobile appliances. Examples of mobileBASF SE 240343

[0198] appliances are vehicles, for example automobiles, bicycles, aircraft, or water vehicles such as boats or ships. Other examples of mobile appliances are those which move manually, for example computers, especially laptops, telephones, or electric hand tools, for example in the building sector, especially drills, battery-powered screwdrivers, or battery-powered staplers.

[0199] The following examples illustrate the invention without intending to be limiting.

[0200] Examples

[0201] Preparation of Primer Compositions

[0202] The inventive primer compositions and one comparative primer composition were prepared by adding into a vessel demineralised water, ethanol, Dispersant Component (Shown in Table 1), C-NERGY® Super C65. The mixture was dispersed employing a dissolver mixer (DISPERMAT® CV, VMA GETZMANN GmbH) with a 50 mm dissolver disk for 10 minutes at 1000.00 rpm at 23°C. Subsequently Konjac Gum was added to the mixture followed by the addition of Texturecel® 40000 PA.

[0203] Following the addition of these additives the mixture was dispersed employing aforesaid dissolver mixer using the 50 mm dissolver disk for 30 minutes at 23°C. To this mixture Licity® 2680 was added and mixed using a dual asymmetric centrifuge (Speed Mixer) for 2 minutes at 200.00 mbar then applying a mixing speed of 2100 rpm for a further 2 minutes which was reduced to 800 rpm for a further 4 minutes.

[0204] The concentration of respective components for each of primer Composition is shown in Table 1.

[0205] Table 1 - concentration wet weight % of Components for each Primer Composition

[0206]

[0207] BASF SE 240343

[0208]

[0209] The dry weight % of the components are shown in Table 2.

[0210] Preparation of the Anode Active Composition

[0211] The Anode Active composition was prepared by adding into a vessel demineralised water (307.831 g), ethanol (0.001 g), C-NERGY® Super C65 (2.553 g) and Texturecel® 40000 PA (20.000 g). The mixture was dispersed employing a dissolver mixer (DISPERMAT® CV, VMA GETZMANN GmbH) with a 50 mm dissolver disk for 30 minutes at 1500 rpm at 23°C. Subsequently SMG-A5® (178.669 g) was added to the mixture. Following the addition of these additives the mixture was dispersed employing aforesaid dissolver mixer using the 50 mm dissolver disk for 30 minutes at 23°C. To this mixture Licity® 2680 (50% aqueous composition) (9.338 g) was added and mixed using a dual asymmetric centrifuge (SpeedMixer) for 2 minutes at 200.00 mbar then applying a mixing speed of 2100 rpm for a further 2 minutes which was reduced to 800 rpm for a further 4 minutes.

[0212] The dry weight % of the components are shown in Table 3.BASF SE 240343

[0213] Table 2 - Dry Weight % of Components in Primer Compositions

[0214]

[0215] Each composition includes 0.0002 wt. % Ethanol in the wet state.

[0216] Table 3 - Dry Weight % of Components in Anode Active Composition

[0217]

[0218] BASF SE 240343

[0219] Dispersant Component A is a powdered homopolymer of N-vinylpyrrolidone of average molar mass (Mw) 9,000 g / mol (GPC) and K-value of 17 (ISO 1628-1 measured as 5% dry in distilled water).

[0220] Dispersant Component B it is a powdered homopolymer of N-vinylpyrrolidone of average molar mass (Mw) 50,000 g / mol (GPC) and K-value of 30 (ISO 1628-1, measured as 1% dry in distilled water).

[0221] Dispersant Component C is a 50% solids by weight aqueous solution of the copolymer of N-vinylpyrrolidone and vinyl acetate (molar ratio 70:30), of K-value 24.0 to 32.0 (ISO 1628-1, measured as 1% dry in distilled water).

[0222] Dispersant Z is a commercially available dispersant based on a high molecular weight acrylic block copolymer (50% by weight aqueous composition) typically used for preparing anode primer formulations.

[0223] C-NERGY® Super C65 supplied from Imerys is a nano carbon black conductive additive for battery cathodes and anodes.

[0224] Konjac Gum from Sarda Starch is a glucomannan polysaccharide powder.

[0225] Texturecel® 40000 PA is a high viscosity sodium carboxymethyl cellulose

[0226] Texturecel® 20000 PA is a high purity sodium carboxymethyl cellulose.

[0227] Licity® 2680 produced by BASF is a styrene butadiene copolymer (50% by weight aqueous composition) suitable as an anode binder in lithium-ion batteries,

[0228] SMG A5® obtained from Showa Denko is a graphite suitable for high-capacity electrical storage in lithium-ion batteries

[0229] Electrode Metal Foil

[0230] The electrode metal foil consisted of a copper foil having a thickness of 10 pm (BF Plainstainproof, Circuit Foil Luxembourg).BASF SE 240343

[0231] Producing the Multilayered Coating to the Electrode Metal Foil

[0232] For the production of electrodes, the pilot coater KTF-S from Mathis AG (2015) at BASF was utilized. This coating station featured a two-layer slot die (RapidEdge Technology GmbH) with a coating width of 220 mm, which was fine-tuned using shim foils. To ensure that the anode was completely covered across the entire coating width, the coating width of the lower layer was decreased by 10 mm.

[0233] Throughout all experiments, the coating speed was consistently maintained at 1 m / min. The pilot line is eguipped with three drying zones, allowing for adjustments to both fan speed and air temperature from the top and bottom. The drying rate was determined by taking into account the heat transfer coefficient and the temperature of the film. The specific drying conditions for each zone are detailed in Table 4.

[0234] Table 4

[0235]

[0236] Calendering of Coated Metal Foil

[0237] Before measuring adhesion strength, the electrodes underwent calendering with a GKL 300 L (Saueressig) at BASF, aiming for a target density of 1.5 g / cm3and a processing speed of 0.5 m / min, which generated a line force of 120 N / mm.

[0238] Adhesion strength was evaluated using a 90° peel test with a TMTC-FR2.5TN.D09 (ZwickRoell GmbH & Co KG) machine. The coating side of the coated electrode foils were placed on a strip of two-sided adhesive tape the other side of which is affixed to an aluminium plate and then subjected to a standardized weight force to ensure consistent results. The electrode foil was subseguently attached to the clamping mechanism of the tensile testing machine. At the beginning of the experiment, the machine head moves upward at a constant speed while maintaining a 90° angle. The electrode foil, attached to the adhesive tape, is pulled away from the substrate,BASF SE 240343

[0239] and the force response is continuously recorded and then averaged arithmetically. Each electrode is tested a minimum of two times to ensure reliability of the results. The results are shown in Table 5.

[0240] Table 5 - Peel Force 90° Tests

[0241]

[0242] The results show that the Inventive Primer Compositions provide the multilayered coating with good peel strength, especially at the more optimum primer weight doses of 0.75 and 1.5 g / m2The peel strength of the multilayered coating employing Primer Composition C when tested at a primer weight dose of 1.5 g / m2increased by almost a factor of 4 by comparison to the Reference Anode.

[0243] Assessment of the Viscosity of the Coating Compositions

[0244] The viscosity of the Primer Compositions and Active Anode Composition was assessed in relation to the shear rate using a plate-plate rheometer (MCR-101) from Anton Paar, equipped with a 25 mm flat measuring head at a temperature of 25°C. Shear rate sweeps were conducted ranging from 0.01 to 1000 s’1.

[0245] The results are shown in Table 6.BASF SE 240343

[0246] Table 6 - Primer Viscosities

[0247]

[0248] BASF SE 240343

[0249] Surface Tension measurements for the Primer Compositions are shown in Table 7.

[0250] Table 7 - Surface Tension measurements on the Primer Compositions

[0251]

[0252] * Surface tension is measured on the wet composition

[0253] The Surface tension of the primer compositions is compared with Graphite-Anode of 64.7 g / m2dry and a surface tension of 72.5 mN / m. The surface tension results illustrate that the surface tension measurements for the inventive primer compositions are significantly closer to the surface tension of the Anode composition.

[0254] Visual Coating Effects

[0255] The visual coating effects for each of the primer compositions are illustrated in Figures 1-8. Table 8 lists the respective primer composition employed in each figure.

[0256] Table 8

[0257]

[0258] BASF SE 240343

[0259]

[0260] Figures 1-4 clearly illustrate defects in the respective coatings (both the wet and the dry states) employing the comparative dispersant component and no dispersant. This is in contrast to the coatings (both the wet and the dry states) employing the dispersant components according to the present invention where no defects are evident.

Claims

BASF SE 240343Claims1. A method of forming a multilayered coating on an electrode, preferably anode, metal foil, comprising the steps of,(i) Providing a primer composition (a) and an active electrode composition (b);(ii) Simultaneously or substantially simultaneously applying the primer composition (a) and the active electrode composition (b) onto the electrode metal foil, wherein the primer composition (a) forms a primer layer (A) directly on the surface of the electrode metal foil and the active electrode composition (b) forms an active electrode layer (B) directly on the surface of the primer layer (A) to form the multilayered coating on the electrode metal foil; and(iii) drying the multilayered coating,wherein the primer composition (a) comprises,(I) at least one electro-conducting component comprising particulate carbon,(II) at least one binder component,(III) at least one co-binder component different from binder component (II), the co-binder being at least one polysaccharide or modified polysaccharide and(IV) a dispersant component,wherein the dispersant component (IV) comprises a polymer of N-vinylpyrrolidone, the polymer of N-vinylpyrrolidone being (i) a homopolymer of N-vinylpyrrolidone which exhibits a K value in the range from 10 to 70; or (ii) a random copolymer of N-vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer which exhibits a K value in the range from 10 to 70.45BASF SE 2403432. The method according to claim 1 , wherein the at least one electro-conducting component (I) comprises at least one selected from the group of carbon black, natural graphite and carbon nanotubes, preferably nano carbon black.

3. The method according to any of claim 1 or claim 2, wherein the at least one binder component (II) comprises at least one synthetic binding polymer, suitably selected from the group of at least one SBR (styrene butadiene rubber), at least one (meth)acrylic acid copolymer and at least one acrylonitrile copolymer, preferably at least one SBR (styrene butadiene rubber).

4. The method according to any of claims 1 to 3, wherein the at least one cobinder component (III) comprises a carboxy methyl cellulose, or salts thereof, optionally in addition to Konjac gum.

5. The method according to any of claims 1 to 4, wherein the polymer of vinyl pyrrolidone is a homopolymer of N-vinylpyrrolidone, preferably having a weight average molecular weight (Mw) in the range from 5000 to 60,000 g / mol.

6. The method according to any of claims 1 to 4, wherein the polymer of N-vinylpyrrolidone is a random copolymer with a copolymerisable ethylenically unsaturated monomer, preferably a random copolymer of N-vinylpyrrolidone and vinyl acetate, more preferably a random copolymer comprising from 60 to 80 mol % N-vinylpyrrolidone and from 20 to 40 mol % vinyl acetate, particularly preferably having a weight average molecular weight (Mw) in the range from 40,000 to 75,000 g / mol.

7. The method according to any of claims 1 to 6, wherein the polymer of N-vinylpyrrolidone is a mixture of the homopolymer according to claim 5 and the random copolymer according to claim 6.

8. The method according to any of claims 1 to 7, wherein the primer composition (a) and the active electrode composition (b) are applied using a multilayer slot die, suitably a multi-layer slot die, for instance a two-layer slot die.46BASF SE 2403439. The method according to any of claims 1 to 8, wherein the primer layer (A) has an area weight from 0.5 to 5 g / m2, preferably from 0.5 to 4 g / m2, more preferably from 0.5 to 3 g / m2, still more preferably from 1 to 2 g / m2.

10. The method according to any of claims 1 to 9, wherein the electrode metal foil is a foil formed from copper or aluminium, preferably copper.

11. A multilayered coated electrode, preferably anode, metal foil, comprising a primer layer (A) located directly on the surface of the electrode metal foil and an active electrode layer (B) which is located directly on the surface of the primer layer (A), the multilayered coated electrode metal foil being obtainable by the method according to any of claims 1 to 10.

12. Use of a polymer of N-vinylpyrrolidone in a method of forming a multilayered coating on an electrode, preferably anode, metal foil as a dispersant and for facilitating compatible surface tension between the layers, the method comprising the steps of,(i) Providing a primer composition (a) and an active electrode composition (b);(ii) Simultaneously or substantially simultaneously applying the primer composition (a) and the active electrode composition (b) onto the electrode metal foil, wherein the primer composition (a) forms a primer layer (A) directly on the surface of the electrode metal foil and the active electrode composition (b) forms an active electrode layer (B) directly on the surface of the primer layer (A) to form the multilayered coating on the electrode metal foil; and(iii) drying the multilayered coating,wherein the primer composition (a) comprises,47BASF SE 240343(I) at least one electro-conducting component comprising particulate carbon,(II) at least one binder component,(III) at least one co-binder component different from binder component (II), the co-binder being at least one polysaccharide or modified polysaccharide and(IV) a dispersant component,wherein the dispersant component (IV) comprises a polymer of N-vinylpyrrolidone, the polymer of N-vinylpyrrolidone being (i) a homopolymer of N-vinylpyrrolidone which exhibits a K value in the range from 10 to 70; or (ii) a random copolymer of N-vinylpyrrolidone and at least one copolymerisable ethylenically unsaturated monomer which exhibits a K value in the range from 10 to 70.

13. The use according to claim 12, which comprises any of the features described in any of claims 2 to 10.

Images