Cathode and method for manufacturing a cathode

Abstract

The present invention relates to a method (110) for manufacturing a cathode (112), a cathode (112) manufactured using the method, and a battery comprising such a cathode (112). The method (110) comprises the following steps: a) providing a current collector (114) wherein at least one surface (116) of the current collector (114) comprises a conductive material (118); b) coating the surface (116) of the current collector (114) with a carbon-containing layer (120); and c) applying a cathode active material (124) to the carbon-containing layer (120), wherein the carbon-containing layer (120) comprises more than 60% and less than 80% by weight of carbon and at least one polymer as a binder, and at least step b) is carried out at a temperature of at least 30°C and at most 70°C.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a cathode, a cathode, and a battery equipped with such a cathode. [Background technology]

[0002] For applications in the automotive industry, particularly for electric vehicles and stationary storage systems, energy storage systems with long lifespan and maximum energy and power density are desirable. Increasingly, high energy density is achieved by using nickel-rich cathode active materials composed of lithium nickel manganese cobalt oxide (NMC). Graphite anodes or silicon-based anode materials are frequently used on the anode side. These electrode materials are applied in the form of slips to thin metals, typically made of aluminum foil that acts as a current collector, by coating processes, particularly slot die coating or slip casting.

[0003] Conventional slips for electrode manufacturing involve aqueous treatments for anode coating and N-methyl-2-pyrrolidone (NMP)-based treatments for cathode coating. The solids content is typically 40% to 60% by weight for the anode slip and 50% to 70% by weight for the cathode slip, depending on the selected cathode active material, the weight ratio of the cathode active material to the carbon additive and binder, and the physicochemical properties of the cathode active material, particularly its particle shape, particle size, particle size distribution, and molecular weight. In the case of extrusion, solids content of up to 90% can also be achieved. While industrial-scale mixing processes are not generally known, it is common knowledge that the complex mechanisms and process steps of slip mixtures, particularly those related to wetting, dispersion, and stabilization, have a significant impact on the quality and stability of the finished electrodes and batteries equipped with such electrodes. In particular, for high-viscosity slips with high solid content, the selection of composition, binder, particle size, particle shape, and, if present, additives are crucial in order to obtain a uniform and reproducible cathode active material layer that meets the high-quality requirements of lithium-ion batteries.

[0004] For both cost and environmental reasons, and especially considering current and / or anticipated government legislation, the use of organic solvents, particularly N-methyl-2-pyrrolidone (NMP), in cathode slips will likely be phased out in the future. However, given the current known level of technology, the production of NMP-free cathode slips presents a significant technical challenge. High-nickel NMC cathode powders have a strong interaction with water, reducing slip stability and, in particular, allowing corrosion of the aluminum current collector to spread due to the high set pH of approximately 12. Corrosion of the aluminum current collector progresses in the pH range above pH > 9 and is associated with the formation of hydrogen gas, which can lead to damage to the surface of the aluminum current collector, particularly as a result of pore formation, cracking, or delamination. A known countermeasure to counteract such damage to the surface of the aluminum current collector is to add acid to lower the pH to typically 7–11, preferably 8–10, and especially 9 ± 0.5. However, the addition of acid can adversely affect the rheology of the cathode slip, the conductivity of the electrode, or the adhesion of its layer. Overall, the addition of acid can result in an observed increase in battery degradation. Depending on the type of acid, a reaction layer may form on the cathode active material particles, leading to an increase in battery resistance and potentially a decrease in the overall performance of the electrochemical battery. Alternatively or additionally, to prevent water from reacting with the cathode active material and thereby avoid an increase in pH, the cathode active material can be coated, particularly by an artificial solid electrolyte interface (SEI), for example, by a coating using ZrO2.

[0005] Patent Document 1 discloses a cathode unit for an alkali metal-sulfur battery, comprising a cathode current collector having a carbon substrate and an electrochemically active component selected from sulfur or alkali metal sulfides, which is in conductive contact with the carbon substrate.

[0006] Patent Document 2 discloses a method for manufacturing a Li-polymer battery by a composite system comprising a current collector, an electrode composition, and a separator, wherein a current collector film coated with a paste-like electrode composition is bonded together with a separator material such that the electrode substrate side coated with the electrode composition is in contact with the separator material. This process leads to a Li-polymer battery with a smooth structure without surface roughness, improved cycle stability, long-term stability, and suppressed troublesome side reactions.

[0007] Patent Document 3 discloses a carbon-coated aluminum material and a manufacturing process that can improve the adhesion between an aluminum material and an active material layer. This carbon-coated aluminum material comprises an aluminum material and a carbonaceous layer formed on the surface of the aluminum material, and further includes an intermediate layer containing aluminum and carbon formed between the aluminum material and the carbonaceous layer. The manufacturing process for this carbon-coated aluminum material includes the steps of placing the aluminum material in a space containing a hydrocarbon material and heating the aluminum material while it is placed in the space containing the hydrocarbon material.

[0008] Patent Document 4 discloses a method for manufacturing electrodes for lithium-containing batteries or capacitors, comprising the steps of: providing a graphite material comprising at least one conductive carbon material; providing an active material mixture comprising an electrochemically active material; supplying the graphite material and the active material mixture to a calendering apparatus such that a concentration gradient of the conductive carbon material is established over the gap width and gap height; and forming the supplied materials into a film in the calendering apparatus comprising at least a conductive carbon substrate and a layer comprising the active material mixture.

[0009] Patent Document 5 discloses an anode for a lithium battery. To improve the Coulomb efficiency and / or cycle stability of the lithium battery, the lithium battery comprises a graphite-coated porous silicon monolith. The present invention further relates to a manufacturing process, a lithium battery, and a lithium battery. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] German Patent Application Publication No. 10 2011 077 932 Specification [Patent Document 2] German Patent Application Publication No. 102 51 241 Specification [Patent Document 3] European Patent Application Publication No. 1 609 878 [Patent Document 4] German Patent Application Publication No. 10 2014 220 964 Specification [Patent Document 5] International Publication No. 2017 / 001118 [Overview of the project]

[0011] In view of the above, an object of the present invention is to provide a method for manufacturing a cathode that overcomes at least partially the known drawbacks and limitations of the prior art, the cathode itself, and a battery equipped with the cathode.

[0012] The above method and cathode are intended to avoid damage to the surface of the aluminum current collector in the cathode, which can lead to increased overall battery degradation, typically resulting from pore formation, crack formation, or layer delamination, or other adverse effects on the rheology or electrode conductivity and layer adhesion of cathode slip, and to avoid complex modifications to the current collector and / or cathode active material by additional physical coating processes, particularly by avoiding the addition of acids, and it is desirable that the specific capacity of the cathode produced by this method is not reduced compared to cathodes known from the prior art.

[0013] The objective is achieved by a method for manufacturing a cathode, a cathode, and a battery equipped with such cathode, according to the features of the independent claim. Advantageous developments that can be implemented individually or in any desired combination are described below in the description and dependent claims.

[0014] In a first aspect, the present invention relates to a method for producing a cathode having at least a current collector and a cathode active material. The term “cathode” refers to an electrode, i.e., an object that can be exposed to voltage and / or current and undergoes a reduction process during the battery discharge process, i.e., reduction to the oxidized state of transition metal cations in the cathode active material in general. In contrast, the term “anode” refers to a further electrode on which an oxidation process takes place during the battery discharge process. Furthermore, it is customary to retain the names “cathode” and “anode” even when the reduction and oxidation processes occur in reverse order during the battery charging process. In addition, the term “battery” refers to an electrochemical cell having at least one cathode, at least one anode electrically isolated from them, and at least one electrolyte configured for charge exchange, and further components, such as electrical connectors and / or separators, may be provided.

[0015] The method for manufacturing a cathode according to the present invention comprises steps a) to c) detailed below, all of which may be carried out sequentially in a specified order, preferably starting with step a), then step b), and then step c). Alternatively, at least two of the specified steps may be carried out partially simultaneously, specifically as a sequential process in which step c) is carried out on a portion of the cathode to which step b) has already been carried out, and simultaneously step b) is carried out on other portions of the cathode, and step a) is carried out on yet other portions of the cathode.

[0016] Each step of this method is: a) A step of providing a current collector, wherein at least the surface of the current collector includes a conductive material, b) a step of coating the surface of the current collector with a carbonaceous layer; c) a step of applying a cathode active material to the carbonaceous layer, and the carbonaceous layer contains more than 60% by weight and less than 80% by weight of carbon and at least one type of polymer as a binder, and at least step b) is carried out at a temperature of at least 30°C and at most 70°C.

[0017] According to step a) of the method, a current collector is provided. The term "current collector" refers to a part of the cathode installed to send the voltage and / or current generated by the cathode to an external conductive element, particularly at least one electrical terminal. For this purpose, at least the surface of the current collector, preferably the whole current collector, contains a conductive material. In a particularly preferred configuration, at least the surface of the current collector, preferably the whole current collector, contains aluminum, nickel, at least one noble metal, particularly gold or platinum, or 100% carbon, and aluminum is particularly preferred. However, it is also possible to use these materials or other materials, preferably a ceramic containing Al2O3, or a thin layer of a semiconductor such as Si in a preferably doped form, on any desired substrate.

[0018] According to step b) of the method, the conductive surface of the current collector is coated with a carbonaceous layer. Here, the term "coating" refers to an operation in which at least one material is applied to the substrate such that a layer is created on the substrate as a result. Here, the term "layer" refers to an arrangement in which the two-dimensional spread of the layer exceeds at least 5 times, preferably at least 10 times, more preferably at least 50 times the layer thickness of the layer.

[0019] Here, the term “carbonaceous layer” refers to a layer having a composition containing a detectable proportion of carbon (C), preferably carbon (C) making up the majority proportion. According to the present invention, the carbonaceous layer comprises more than 60% by weight, preferably at least 65% by weight, more preferably at least 67.5% by weight, and less than 80% by weight of carbon, preferably 75% by weight or less, preferably 72.5% by weight or less, particularly about 70% by weight of carbon, and at least one polymer as a binder, and it is more preferable that the total proportion of carbon and polymer in the carbonaceous layer is at most 100% by weight. The carbon used is preferably carbon black, and the term “carbon black” refers to a black powdery solid containing at least 80% by weight and at most 99.5% by weight of carbon. However, in principle, it is also conceivable to use at least one other type of carbon, particularly conductive carbon black having a particle size of up to several hundred nanometers, conductive graphite having a particle size in the μm or sub-μm range, such as KS6L, amorphous carbon including soft carbon or hard carbon, and / or polymorphs of carbon containing impurities, for example, in the form of heteroatoms.

[0020] "Binder" or "binding agent" refers to a substance designed to produce a composite material in the form of an essentially physical compound by adhesion, aggregation and / or adsorption between particles and / or between phase interfaces, whereby regions delimited by particles or phase interfaces in the composite material are adsorbed to each other so as to have cohesiveness, a network structure or binding properties. According to the present invention, the binder contained in the carbonaceous layer contains at least one polymer. As used herein, the term "polymer" refers to a compound containing a plurality of molecules of the same or similar type called "monomers" arranged side by side with each other. In a particularly preferred configuration, at least one polymer contained in the binder is selected from polyvinylidene fluoride (PVDF), polyamide (PA), polybutyl acrylate (PBA), polyacrylic acid (PAA), poly(methyl acrylate) (PMA), cellulose, preferably carboxymethyl cellulose (CMC), particularly Na-CMC or succinoyl carboxymethyl cellulose (SCMC), styrene butadiene rubber (SBR), a mixture of SBR and SCMC, an epoxy-based binder, particularly an epoxy curing agent-based, latex hydrogenated polymer, biopolymer, preferably a polysaccharide-based plant gum, particularly alginate, guar powder, karaya or xanthan. However, the use of at least one other polymer is also conceivable.

[0021] According to the present invention, the composition of the carbonaceous layer is thus adjusted to a predetermined narrow parameter range. If the proportion of carbon (C), particularly carbon black, becomes excessively high as a result of the leaching of carbon components, particularly carbon black, which typically occur from the composite composed of carbon and binder, then corrosion of the conductive electrode material, more preferably aluminum, on the surface of the current collector, in particular, will not be adequately prevented when the cathode active material is subsequently applied to the carbonaceous layer in step c). This effect could be confirmed by preliminary tests on commercially available aluminum graphite-coated current collectors. Furthermore, it could be observed that when the proportion of carbon (C), particularly carbon black, is very high, pores are formed in the carbonaceous layer, allowing the current collector to be exposed to corrosion and no longer protected from it. If the proportion of carbon (C), particularly carbon black, is too low, it may become significantly more difficult, or even impossible, to achieve a fairly substantially homogeneous coating of the carbonaceous layer, firstly, because the electrical contact between the cathode and the current collector deteriorates, and secondly, because the hydrophobic wetting behavior of the cathode slip is established, as could be demonstrated by the corresponding tests. For further details on this point, please refer to the description of the examples below.

[0022] Furthermore, according to the present invention, in step b), the surface of the current collector is coated with a carbonaceous layer at a temperature of at least 30°C, preferably at least 35°C, more preferably at least 40°C, up to a maximum of 70°C, preferably up to a maximum of 65°C, and more preferably up to a maximum of 60°C. For this purpose, the surface of the current collector is coated with a carbonaceous layer by a coating method, which is preferably selected from the squeegee method, spray method, slot die coating method, extrusion method, spin coating method, or printing method, particularly aerosol jet printing, but the use of different types of coating methods is also possible. Preferred coating methods are, in particular, simple methods that can be carried out inexpensively, and the use of complex and expensive coating methods, especially physical vapor deposition (PVD) or atomic layer deposition (ALD), can be omitted.

[0023] Therefore, the carbonaceous layer of the present invention can function particularly as a passivation layer. The term "passivation layer" as used herein refers to a layer that can sufficiently prevent corrosion of the surface of the current collector, more preferably the aluminum surface, while the cathode active material is being applied to the carbonaceous layer.

[0024] The carbonaceous layer of the present invention has a thickness of at least 0.1 μm, preferably at least 0.25 μm, more preferably at least 0.5 μm, and at most 20 μm, preferably at most 10 μm, and more preferably at most 7.5 μm. For further details on this point, please refer to the description of the examples below.

[0025] According to the present invention, in addition to adjusting the composition of the carbonaceous layer within a predetermined narrow parameter range, the carbonaceous layer can also be generated within an even further predetermined narrow parameter range. For this purpose, it has been experimentally shown that drying of the carbonaceous layer, which can proceed very quickly due to its very thin thickness, should not be carried out at temperatures above 70°C. This is because, at this temperature range, the texturing of the carbonaceous layer changes in the microscale and / or nanoscale range compared to drying at temperatures within a selected temperature range, so that hydrophobic wetting behavior, or even superhydrophobic wetting behavior, characterized by the occurrence of the so-called "lotus effect," is established for the layer coated on the carbonaceous layer. Further details on this point can be found in the description of the following examples.

[0026] According to step c) of this method, the cathode active material is coated onto the carbonaceous layer. The term “coating” here refers to the operation of coating a substrate with at least one material such that the material remains on the substrate as a result. The cathode material may include a lithium-containing material or a material containing at least one other cation, preferably sodium. The lithium-containing material is preferably lithium nickel manganese oxide (LiNi 0.5 Mn 1.5O4, LNMO), mixtures of LNMO with additional compounds selected from at least one element among Co, Al and additional Li, lithium-rich NMC (x LiMn2O3·NMC), lithium nickel manganese cobalt oxide (LiNixMnyCozO2,NMC), and lithium-rich lithium nickel manganese cobalt oxide (x LiMn2O3·NMC,x < 0.4) Lithium metal phosphate (LiMPO4), lithium cobalt oxide (LiCoO2, LCO), lithium manganese oxide (LiMn2O4 or Li2MnO3, LMO), or lithium nickel cobalt aluminum oxide (LiNi 1-x-y Co x Al y The cathode material is selected from O2 (NCA), where M is selected from at least one element of Fe, Mn, Co, or Ni, specifically from lithium iron phosphate (LiFePO4, LFP), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4, LCP), and lithium nickel phosphate (LiNiPO4). Furthermore, the cathode material may include other types of lithium-containing materials or sodium-containing materials. In addition, a combination of at least two cathode materials may also be preferred.

[0027] In a particularly preferred configuration, in step c), the cathode active material is c1) A step of applying an aqueous cathode slip to a carbonaceous layer, c2) The aqueous cathode slip can be applied to the carbonaceous layer by the step of drying the aqueous cathode slip on the carbonaceous layer. Here, the aqueous cathode slip may preferably contain an aqueous solution of the cathode active material.

[0028] The term "cathode slip" generally refers to a mixture of a cathode active material, at least one binder, optionally additives, particularly conductive carbon black or conductive graphite, and at least one solvent. Preferably, the use of water as the solvent makes it possible to more preferably omit the use of acid compared to known methods from the prior art, and as a result, firstly, the current collector can be better protected from corrosion, and secondly, the electrical capacity of a battery having at least one cathode produced by this method does not decrease.

[0029] In step c1), the aqueous cathode slip can be applied to the carbonaceous layer by a coating method. More preferably, the coating method used for this purpose may be the same as the one used in step b) to coat the surface of the current collector using the carbonaceous layer. The coating method is preferably selected from any of the above-described coating methods, but the use of other types of coating methods is also possible.

[0030] After step c1), or even during step c1), the aqueous cathode slip on the carbonaceous layer can be dried in step c2). Drying here can be passive or active, and active drying can be achieved using a drying method selected from radiative drying, particularly by laser or infrared irradiation, or convection drying, particularly by a floating dryer. For drying the aqueous cathode slip in step c2), at least one temperature gradient and / or at least one temperature zone can be used in a particular configuration.

[0031] During step c), the temperature used is preferably the same as the temperature used during the coating of the current collector surface with a carbonaceous layer in step b), but lower or higher temperatures may also be used. Thus, in certain configurations, step c), and especially step c2), may be carried out at lower temperatures, preferably room temperature, i.e., 15°C to 25°C, especially around 20°C, or after the completion of step b), at temperatures above 70°C, especially above 100°C, but below the glass transition temperature of the polymer used as the binder, and below the critical temperature at which a phase transition or change of state of matter occurs in the cathode active material, binder, optionally additives, particularly conductive carbon black or conductive graphite, contained in the cathode slip used in each case.

[0032] As will become clear in detail from the exemplary examples shown below, the selected composition of the carbonaceous layer within a narrow parameter range and the method for producing the carbonaceous layer within a narrow temperature range have the effect of more preferably forming a layer of cathode active material as a homogeneous layer on the surface of the carbonaceous layer. Here, the term “homogeneous” refers to a layer having a composition and spatial phase that is substantially independent of its position within the layer, particularly below each selected threshold. The creation of a homogeneous layer from the cathode active material is facilitated in that the carbonaceous layer exhibits wetting behavior that enables a homogeneous coating, and hydrophobic or superhydrophobic wetting behavior is eliminated. For further details on this point, please refer to the description of the exemplary examples below.

[0033] In a particularly preferred configuration, the coating of the cathode active material onto the carbonaceous layer in step c) may further include the following steps: c3) Next, the cathode active material is calendered on a carbonaceous layer, at least partially dried.

[0034] In particular, by using a calendering method that involves applying an aqueous cathode slip to a carbonaceous layer and then drying the aqueous cathode slip at least partially, preferably completely, on the carbonaceous layer, the cathode active material particles can be embedded or recessed into the carbonaceous layer, as detailed in the description of the exemplary embodiments below. Such an operation can be particularly advantageous in that it improves the mechanical and / or electrical adhesion of the current collector to the cathode active material. Thus, firstly, the presence of a carbonaceous layer in the cathode improves the adhesion between the cathode active material layer and the current collector, and secondly, the presence of a carbonaceous layer in the cathode also reduces the electrical conductivity resistance between the cathode active material layer and the current collector. However, other advantages can also be considered.

[0035] In a further embodiment, the present invention relates to a cathode preferably manufactured by the method disclosed herein, wherein the cathode is - A current collector containing a conductive material on its surface, - The carbonaceous layer on the surface of the current collector, - comprising a cathode active material on a carbonaceous layer, Here, the carbonaceous layer comprises more than 60% by weight and less than 80% by weight of carbon, and at least one polymer as a binder, and the cathode active material layer is formed as a homogeneous layer on the surface of the carbonaceous layer. For the term "homogeneous," please refer to the definition of this term above.

[0036] In a further embodiment, the present invention includes at least, -At least one cathode manufactured by the process disclosed herein, -At least one anode, - relating to a battery comprising at least one electrolyte.

[0037] In addition, the battery may comprise at least one further component, in particular a separator for spatially separating at least one cathode from at least one anode. Thus, the battery may be a lithium-ion battery, a lithium polymer battery, or a so-called post-lithium battery, preferably a sodium battery. In addition, other types of batteries or energy storage media may also be considered, such as solid batteries, including hybrid polymer ceramic solid batteries, or supercapacitors.

[0038] Here, at least one anode may comprise at least one anode material, which is preferably selected from graphite, amorphous carbon including soft carbon or hard carbon, silicon, silicon oxide, silicon / graphite composites, silicon oxide / carbon composites, silicon / carbon composites, metallic lithium, lithium titanate, lithium alloys comprising at least one element from tin, germanium, magnesium, aluminum, and zinc, or transition metal-doped zinc oxide or tin oxide, tin, germanium, magnesium, aluminum, or zinc, but the use of another anode material or a combination of at least two cathode materials is also possible.

[0039] For further details regarding both the cathode and the battery, please refer to the description of the method and exemplary examples disclosed herein.

[0040] The method for producing a cathode disclosed herein, the cathode, and a battery equipped with such a cathode offer numerous advantages over cathodes, methods for producing cathodes, and batteries equipped with such cathodes known from the prior art. In particular, the absence of the need to add acid in the production of the cathode prevents damage to the surface of the aluminum current collector in the cathode, typically resulting in pore formation, cracking, or delamination, thus avoiding further drawbacks that could increase overall battery degradation, especially regarding the rheology of cathode slip or electrode conductivity and layer adhesion. Furthermore, it eliminates the need for complex modification of the current collector and / or active material by additional physical coating processes. Finally, the specific capacity of the cathode produced by this method may remain unchanged or even be remarkably improved compared to cathodes known from the prior art.

[0041] The words “have,” “include,” “contain,” and “equip,” or any grammatical variations thereof, are used in a non-exclusive sense herein. Thus, these words can relate to both situations in which there are no further features in addition to the features introduced by these words, and situations in which one or more further features exist. For example, the expressions “A has B,” “A includes B,” “A contains B,” or “A is equipped with B” can relate to both situations in which there are no further elements in A other than B (i.e., A consists only of B), and situations in which, in addition to B, A has one or more further elements (e.g., element c, elements c and d, or further elements).

[0042] Furthermore, it should be noted that the expressions “at least one” and “one or more,” as well as their grammatical variations, when used in relation to one or more elements or features and intended to indicate that such elements or features may be provided once or more times, are generally used only once, for example, when such features or elements are first introduced. If such features or elements are subsequently mentioned again, the corresponding terms “at least one” or “one or more” are generally not used again, so that the possibility of such features or elements being provided once or more times is not limited.

[0043] Furthermore, phrases such as “preferably,” “particularly,” “for example,” or similar terms are used herein in relation to optional features, but this does not limit alternative embodiments. For example, features introduced by these phrases are optional features, and there is no intention to limit the scope of protection of claims, particularly independent claims, by these features. For example, as a person skilled in the art will understand, the present invention can also be carried out using different configurations. Similarly, features introduced in the form of “in one embodiment of the present invention” or “in an exemplary example of the present invention” are considered optional features, but there is no intention to limit the scope of protection of alternative configurations or independent claims by them. Moreover, these introductory expressions are not intended to affect all ways in which the features introduced thereby may be combined with other features, whether optional or not. [Brief explanation of the drawing]

[0044] Further details and features of the present invention will become apparent from the following preferred exemplary embodiments, particularly in relation to the dependent claims. In this context, each feature can be implemented individually or in combination with other features. However, the present invention is not limited to these exemplary embodiments. These exemplary embodiments are schematically shown in the following figures. The same reference numerals in the figures indicate the same or functionally identical elements, or elements that functionally correspond to each other. The drawings are as follows.

[0045] [Figure 1] This is a schematic diagram using a cross-sectional view of a preferred embodiment of the steps of the method for manufacturing a cathode according to the present invention. [Figure 2] This is a schematic diagram of the adjustments made by the present invention to accommodate both the mixing of carbonaceous layers across a parameter range (Figure 2a) and the production of carbonaceous layers across a temperature range (Figure 2b). [Figure 3] This is a schematic diagram of a cross-section of the cathode of the present invention. [Figure 4] This is a comparison of the changes in specific volume of NMC-622 half-cells as the number of cycles for different C rates, produced using water-based slip with added acid and water-based slip without added acid. [Figure 5] This figure shows the cyclic voltammograms for an exemplary example using a carbonaceous layer and a comparative example not using a carbonaceous layer. [Modes for carrying out the invention]

[0046] Figure 1 shows schematic diagrams of preferred embodiments of steps a) to c) of the method 110 of the present invention for manufacturing cathode 112, with cross-sectional views for each case.

[0047] A current collector 114 is provided according to step a) of the present method 110, wherein at least the surface 116 of the current collector 114 includes a conductive material 118. Preferably, at least the surface 116 of the current collector 114, preferably the entire current collector 114, includes aluminum, but the use of different conductive materials 118 is also possible.

[0048] According to step b) of the present method 110, particularly after step a), the surface 116 of the current collector 114 is coated with a carbonaceous layer 120. According to the present invention, the carbonaceous layer comprises more than 60% by weight, preferably at least 65% by weight, more preferably at least 67.5% by weight, and less than 80% by weight of carbon, preferably 75% by weight or less, preferably 72.5% by weight or less, particularly about 70% by weight of carbon, and at least one polymer as a binder, wherein the ratio of carbon to polymer in the carbonaceous layer is more preferably up to 100% by weight. The carbon used is preferably carbon black.

[0049] According to step c) of this method 110, the cathode active material 124 is applied to the surface 122 of the carbonaceous layer 120, particularly after or during step b). Here, step c) is preferably In step c1), a step of applying an aqueous cathode slip containing an aqueous solution of the cathode active material 124 to the surface 122 of the carbonaceous layer 120, Step c2) includes the step of drying the aqueous cathode slip on the surface 122 of the carbonaceous layer 120, Following this process, step c3) may include calendering the cathode active material 124 on the surface 122 of the carbonaceous layer 120, at least partially.

[0050] As will be described later with respect to Figure 3, optional calendering of the cathode active material 124 on the surface 122 of the carbonaceous layer 120 in step c3), after the step of coating the cathode active material 124 onto the carbonaceous layer 120, improves adhesion between the layer of cathode active material 124 and the current collector 114, improves electrical conductivity, and can reduce the electrical conductivity resistance between the cathode active material 124 and the current collector 114, as a result of the carbonaceous layer 120 being present on the cathode 112.

[0051] According to the present invention, step b) is carried out at a temperature of at least 30°C, preferably at least 35°C, more preferably at least 40°C, up to 70°C, preferably up to 65°C, more preferably up to 60°C, and particularly at about 50°C. With respect to step c), the same temperatures as described in detail above may be used, or even lower or higher temperatures may be used. Particularly as can be seen in detail from Figures 2a and 2b, the composition of the carbonaceous layer 120 selected within a narrow parameter range and the method of producing the carbonaceous layer 120 within a specific narrow temperature range have the effect of forming a layer of cathode active material 124 as a homogeneous layer on the surface 122 of the carbonaceous layer 120.

[0052] The carbonaceous layer 120 of the present invention may have a layer thickness of at least 0.1 μm, preferably at least 0.25 μm, more preferably at least 0.5 μm, and up to 20 μm, preferably up to 10 μm, and more preferably up to 7.5 μm. In the exemplary examples described below, layer thicknesses of 0.5 μm to 6 μm were used for the carbonaceous layer. This small layer thickness of the carbonaceous layer 120 of the present invention typically accounts for a maximum of 1% by weight, preferably up to 0.5% by weight, and more preferably up to 0.25% by weight of the total weight of the cathode 112, and therefore does not increase the total weight of the cathode 112 or the material cost. The carbonaceous layer 120 can function particularly as a passivation layer in that it can sufficiently prevent corrosion of the surface 116 of the current collector 114, especially aluminum, while the cathode active material 124 is applied to the surface 122 of the carbonaceous layer 120.

[0053] Figure 2 shows modified examples of the shape of the cathode active material 124 layer on the surface 122 of the carbonaceous layer 120, depending on the composition of the carbonaceous layer 120 (Figure 2a) or the manufacturing method of the carbonaceous layer 120 (Figure 2b).

[0054] As can be seen from Figure 2a, the desired homogeneous layer of the cathode active material 124 has a parameter range of 130, and the carbonaceous layer 120 is The carbon ratio of 132 is more than 60% by weight and less than 80% by weight, A binder ratio of at least 20% and up to 40% by weight, In either case, the mixture is formed on the surface 122 of the carbonaceous layer 120 only within a parameter range 130 such that the sum of the ratios 132 and 134 is no more than 100% by weight. The binder used as an example here was polymer polyvinylidene fluoride (PVDF), but it is also possible to use one or more other polymers.

[0055] A further parameter range 136 shown in Figure 2a, wherein the carbonaceous layer 120 is 132 has a carbon content of less than 60% by weight, A binder ratio of at least 40% by weight 134 In any case, within a further parameter range 136, such that the sum of the ratios 132 and 134 is up to 100% by weight, hydrophobic wetting behavior or even superhydrophobic wetting behavior is established on the surface 122 of the carbonaceous layer 120, which has the effect of the layer of cathode active material 124 becoming an undesirable droplet on the surface 122 of the carbonaceous layer 120 rather than a desired homogeneous layer.

[0056] Another further parameter range 138, similarly shown in Figure 2a, where the carbonaceous layer 120 is A carbon ratio of at least 80% by weight 132 A binder ratio of up to 20% by weight is 134. In either case, within another further parameter range 138, the sum of the ratios 132 and 134 is up to 100% by weight, craters or wells 140 and / or capillaries 142 are formed in the volume of the cathode active material 124 layer, and these extend to the surface 122 of the carbonaceous layer 120, or even to the surface 116 of the current collector 114. As a result of these effects, the surface 116 of the current collector 114, particularly the aluminum-containing surface, is no longer protected from corrosion, which is undesirable.

[0057] As can be seen from Figure 2b, the desired homogeneous layer of cathode active material 124 is formed on the surface 122 of the carbonaceous layer 120 only if the surface 116 of the current collector 114 is within the temperature range 144 in which the carbonaceous layer 120 is coated at a temperature of at least 30°C to a maximum of 70°C.

[0058] As shown in Figure 2b, in a further temperature range 148 including temperatures below 30°C, craters or wells 140 and / or capillaries 142 are formed in the volume of the cathode active material 124 layer, such that the surface 116 of the current collector 114, particularly the aluminum-containing one, is no longer protected from corrosion as a result of these effects, and these extend to the surface 122 of the carbonaceous layer 120, or even to the surface 116 of the current collector 114, and / or pores 150 are formed.

[0059] Similarly, as shown in Figure 2b, in another further temperature range 152 including temperatures above 70°C, essentially the same effect as in the parameter range 136 occurs, but this means that hydrophobic wetting behavior, or even superhydrophobic wetting behavior, occurs on the surface 122 of the carbonaceous layer 120, which has the effect of the layer of cathode active material 124 becoming an undesirable droplet on the surface 122 of the carbonaceous layer 120 rather than in the desired homogeneous layer form.

[0060] Figure 3 is a schematic cross-sectional view of the cathode 112 of the present invention. This figure clearly shows how the particles of the cathode active material 124 are embedded in or recessed in the carbonaceous layer 120, in particular, to improve the mechanical and electrical contact with the current collector 114.

[0061] Figure 4 shows the discharge ratio capacity C in mAh / g for NMC622 half cells according to the number of cycles n. dis The graph shows a comparison of the transitions of 170 and 172 for different C rates (>0 to <70). Here, NMC622-00 is a cathode active material 124 lithium nickel manganese cobalt oxide (LiNi) which is treated with phosphoric acid (H3PO4) during the manufacturing of cathode 112 and has a layer thickness of 70 μm. x Mny Co z While referring to a comparative sample not included in the present invention using (O2, NMC), NMC622-01 shows a sample of the present invention using NMC of cathode active material 124 that has not been acid-treated and has a layer thickness of 65 μm. Here, NMC622 refers to Li(Ni 0.6 MnCo 0.2 )O2. When comparing the transition of the discharge specific capacity 170 of the sample NMC622-01 of the present invention with the discharge specific capacity 172 of the comparative sample NMC622-00, surprisingly, the discharge specific capacity of the sample of the present invention has increased compared to the comparative sample, and in particular, it has actually been shown to exceed 1C.

[0062] FIG. 5 shows a cyclic voltammogram 180 as a typical example using a sample of the present invention including a carbonaceous layer 120, and a further cyclic voltammogram 182 as a comparative sample not included in the present invention and produced by adding an acid without a carbonaceous layer. The sample of the present invention was produced using an aqueous NMC622 slip without acid, while the comparative sample was produced using an aqueous NMC622 slip with added acid. Here, the slip without acid includes a slip that does not add any acid to affect the pH. Due to the reaction of NMC and water, a high pH is established, and the range may be 12 or more. When no acid is added, this high pH is maintained, but when acid is added, the pH may decrease, typically 7-11, preferably 8-10, and particularly 9±0.5 in this comparative example.

[0063] The NMC622 of the cathode active material 124 used is from the same batch in both measurements. The cyclic voltammogram 180 for the sample of the present invention and the cyclic voltammogram 182 for the comparative sample are https: / / doi.org / 10.3390 / nano11071840While these are available, a comparison reveals that the comparative samples exhibit oxidation-reduction peaks at 3.9V and 3.6V, while the samples of the present invention exhibit oxidation-reduction peaks at 3.78V and 3.71V, both very close together, suggesting a significantly lower polarizability of the cell. The improvement in cell polarization when using an acid-added aqueous slip may be due to the chemical reaction between the acid and the cathode active material 124, and the resulting increase in electrical conductivity between the active cathode material 124 layer and the current collector 114. Furthermore, this can achieve higher electrical conductivity in the deeper regions near the current collector, which can be particularly advantageous when the layer thickness is large. Further advantages are described in detail above. [Explanation of symbols]

[0064] 110 Method for manufacturing a cathode 112 Cathode 114 Current collector 116 Surface 118 Conductive materials 120 Carbonaceous layer 122 Surface 124 Cathode Active Material 130 Parameter Range 132 carbon ratio 134 Binder ratio 136 Parameter Range 138 Parameter Range 140 craters or wells 142 capillaries 144 temperature range 146 Temperature 148 temperature range 150 pores 152 Temperature range 160 particles 170 Changes in discharge ratio capacity of the sample of the present invention 172 Changes in discharge ratio capacity of comparative samples 180 Cyclic voltammogram of the sample of the present invention 182 Cyclic voltammograms of comparative samples

Claims

1. A method (110) for producing a cathode (112), The cathode (112) has at least one current collector (114) and a cathode active material (124), The method (110) includes the following steps. a) A step of providing a current collector (114), wherein at least the surface (116) of the current collector (114) includes a conductive material (118); b) A step of coating the surface (116) of the current collector (114) with a carbonaceous layer (120); and, c) A step of coating a cathode active material (124) onto the carbonaceous layer (120), wherein the carbonaceous layer (120) comprises more than 60% by weight and less than 80% by weight of carbon and at least one polymer as a binder, At least step b) is carried out at a temperature of at least 30°C and no more than 70°C.

2. The method according to the preceding claim (110), wherein the carbonaceous layer (120) contains carbon black, and the carbon black is a black powdery solid containing at least 80% by weight and at most 99.5% by weight of carbon.

3. The cathode active material (124) is c1) A step of applying an aqueous cathode slip to the carbonaceous layer (120), c2) A step of drying the aqueous cathode slip on the carbonaceous layer (120), Therefore, in step c), the carbonaceous layer (120) is coated, The method according to any one of the preceding claims (110), wherein the aqueous cathode slip comprises an aqueous solution of the cathode active material (124).

4. The method according to any one of the preceding claims (110), wherein the cathode active material (124) takes the form of a homogeneous layer on the surface (122) of the carbonaceous layer (120).

5. In step c) above, the step of coating the cathode active material (124) onto the carbonaceous layer (124) is, c3) The method (110) according to any one of the preceding claims, comprising the step of calendering the cathode active material (124) which has been at least partially dried on the carbonaceous layer (120).

6. The method according to any one of the preceding claims (110), wherein at least step b) is carried out at a temperature of at least 40°C and at most 60°C.

7. The method according to any one of the preceding claims, wherein the carbonaceous layer (120) comprises at least 65% by weight and a maximum of 75% by weight of carbon and the binder.

8. The method according to any one of the preceding claims (110), wherein the step of coating the surface (116) of the current collector (114) with the carbonaceous layer (120) in step b) is carried out until the carbonaceous layer (120) has a layer thickness of 0.1 μm to 20 μm.

9. The method according to the preceding claim (110), wherein the step of coating the surface (116) of the current collector (114) with the carbonaceous layer (120) in step b) is carried out until the carbonaceous layer (120) has a layer thickness of 0.1 μm to 10 μm.

10. The method according to the preceding claim (110), wherein the step of coating the surface (116) of the current collector (114) with the carbonaceous layer (120) in step b) is carried out until the carbonaceous layer (120) has a layer thickness of 0.1 μm to 7.5 μm.

11. The method (110) according to any one of the preceding claims, wherein at least the surface (116) of the current collector (114) includes aluminum, nickel, a precious metal, carbon, or a thin layer thereof, a thin layer of a dielectric, or a thin layer of a semiconductor.

12. The method according to any one of the preceding claims (110), wherein the at least one polymer is selected from polyvinylidene fluoride, polybutyl acrylate, polyacrylic acid, styrene-butadiene rubber, biopolymer, or a mixture thereof.

13. The method according to any one of the preceding claims (110), wherein the cathode active material (124) is selected from a lithium-containing material or a sodium-containing material.

14. A cathode (112), wherein the cathode (112) is A current collector (114), wherein the surface (116) of the current collector (114) contains a conductive material (118), The carbonaceous layer (120) on the surface (116) of the current collector (114), The carbonaceous layer (120) comprises a layer of cathode active material (124), A cathode (112) wherein the carbonaceous layer (120) comprises more than 60% by weight and less than 80% by weight of carbon and at least one polymer as a binder, and the layer of the cathode active material (124) is formed as a homogeneous layer on the carbonaceous layer (120).

15. At least one cathode (112) as described in the prior claim, At least one Anode and A battery comprising at least one electrolyte.

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