Electrolyte component for electrochemical elements

Abstract

The invention relates to an electrolyte component for an electrochemical element, wherein the electrolyte component comprises an electrolyte and a support structure; the electrolyte is a solid or a gel, and the support structure has a plurality of pores which are at least partly filled by the electrolyte; and the support structure contains at least 5% and at most 30% fibrillated fibers of regenerated cellulose, at least 50% and at most 90% non-fibrillated matrix fibers, and at least 5% and at most 30% of a binder. The non-fibrillated matrix fibers - do not have a melting point or have a melting point which is at least 120°C, - do not dissolve in water or dissolve in water but not in water at a temperature of 80°C or less, and - have an average length-weighted length of at least 2.0 mm and at most 8.0 mm and an average length-weighted thickness of at least 1 µm and at most 16 µm, the binder dissolving in water at a temperature of 80°C but not in water at a temperature of 30°C.

Description

[0001] delfortgroup AG

[0002] H7O759WO

[0003] Electrolyte component for electrochemical elements

[0004] AREA OF INVENTION

[0005] The invention relates to an electrolyte component for an electrochemical element comprising a solid or gel-like electrolyte and a porous support structure, wherein the porous support structure has a high mechanical energy absorption capacity. This enables the efficient, high-speed, industrial-scale production of electrochemical elements with this electrolyte component. The invention also relates to a method for producing the support structure and an electrochemical element comprising the electrolyte component according to the invention.

[0006] BACKGROUND AND STATE OF THE ART

[0007] An electrochemical cell typically comprises at least one positive electrode, one negative electrode, a housing, current collectors, and a component that spatially and electrically separates the two electrodes and contains the electrolyte. In many cases, the electrolyte is a liquid containing a dissolved salt and usually one or more organic solvents. Electrochemical cells with such electrolytes therefore pose a fire hazard if damaged or malfunctioning, particularly because the organic solvents are flammable. Solid or gel-like electrolytes are known as alternatives in the field, which can reduce or eliminate this fire hazard.

[0008] The processing of these electrolytes in industrial plants often requires a porous support structure to contain the electrolyte, as the electrolyte itself lacks sufficient mechanical stability. This generally applies to gel-like electrolytes and especially to polymer electrolytes, which only polymerize into a solid electrolyte after the support structure has been filled. Often, production and application require elevated temperatures and pressures, for example, to keep the electrolyte's electrical resistance low, so a support structure is also necessary for stability in these situations.

[0009] The support structure must therefore meet high requirements regarding its mechanical and thermal properties. Furthermore, the support structure should also exhibit a small thickness, high porosity, and a large number of pores with low tortuosity in order to impart good electrical properties to the electrochemical element manufactured from it.

[0010] There is therefore an interest in improving the mechanical properties of the support structure in such electrolyte components.

[0011] SUMMARY OF THE INVENTION

[0012] The present invention is based on the objective of providing an electrolyte component for electrochemical elements whose support structure has a high mechanical energy absorption capacity, is thermally stable and nevertheless ensures favorable electrical properties of the electrochemical element produced therefrom.

[0013] This problem is solved by an electrolyte component according to claim i, an electrochemical element comprising this electrolyte component according to claim 32, and a method for producing a support structure for the electrolyte component according to claim 34. Advantageous embodiments are specified in the dependent claims.

[0014] The electrolyte component according to the invention comprises an electrolyte and a support structure, wherein the electrolyte is a solid or a gel and the support structure has a plurality of pores which are at least partially filled by the electrolyte, and wherein the support structure contains at least 5% and at most 30% fibrillated fibers of regenerated cellulose, at least 50% and at most 90% non-fibrillated matrix fibers and at least 5% and at most 30% of a binder, wherein the percentages refer in each case to the mass of the support structure, and wherein the non-fibrillated matrix fibers have no melting point or, if they have a melting point, it is at least 120°C, and the non-fibrillated matrix fibers are not soluble in water or, if they are soluble in water, are not soluble in water with a temperature of 80°C or less, and the non-fibrillated matrix fibers have a mean length-weighted length of at least 2,The binder must have a diameter of 0 mm and at most 8.0 mm and a mean length-weighted thickness of at least 1 pm and at most 16 pm, and must be soluble in water at a temperature of 80°C but not in water at a temperature of 30°C. Binders typically have a transition temperature or temperature range above which they become soluble in water or above which their solubility in water increases significantly. Below this transition temperature or temperature range, the binder is considered insoluble in water; above it, it is considered soluble. The criterion that the binder is soluble in water at a temperature of 80°C includes the case where it is already soluble in water at temperatures below 80°C, but in any case, not at temperatures of 30°C or less. For example, a binder that is soluble in water from a temperature of about 65°C is also soluble in water at 80°C.However, this would not be the case at 30 °C, and would therefore fulfill the aforementioned criterion. The term "matrix fibers" merely indicates that these form the "basic material" of the supporting structure, which is also referred to as the "matrix" in the field.

[0015] For all standards mentioned in this disclosure, any undated normative references in these standards refer to the versions of the references valid at the time of publication of the relevant standard cited herein.

[0016] The mean length-weighted length of fibers can be determined according to ISO 16065-2:2014. This method for automated optical analysis of fiber length is also used analogously by commercially available measuring instruments to determine the mean length-weighted thickness. For example, the L&W Fiber Tester Plus 912+ from Lorentzen & Wettre or the Valmet Fiber Image Analyzer (Valmet FS5) from Valmet Oyj are suitable measuring instruments for determining the mean length-weighted length or thickness. In this disclosure, references to the mean length-weighted thickness of fibers always refer to the thickness determined by automated optical analysis of a fiber suspension and not to other measurement methods, in particular not to measurements from light microscopy of fiber suspensions or the analysis of cross-sectional images by scanning electron microscopy.

[0017] The inventor recognized that a suitable porous support structure for solid or gel-like electrolytes could be produced from matrix fibers, which are cross-linked by fibrillated fibers of regenerated cellulose and a binder, thus giving the support structure high porosity and high energy absorption capacity.

[0018] The non-fibrillated matrix fibers serve to create a porous structure in which the fibrillated fibers of the regenerated cellulose can adhere and crosslink with the binder. The non-fibrillated matrix fibers, crosslinked in this way, generate high elongation, primarily due to their length, thus increasing energy absorption capacity. The non-fibrillated matrix fibers have no melting point, or if they do, it must be higher than 120°C. This requirement ensures, among other things, that the non-fibrillated matrix fibers do not melt during the fabrication of the support structure. The absence or high melting point of the non-fibrillated matrix fibers also means increased safety if an electrochemical element manufactured from them is exposed to higher temperatures during operation or in the event of damage.

[0019] The binder, in conjunction with the fibrillated fibers of regenerated cellulose, serves to bind the matrix fibers together and stabilize the support structure. A support structure formed in this way not only achieves high elongation at break but also, in relation to its relatively low basis weight, high tensile strength, so that the overall energy absorption capacity, which is largely determined by these two parameters, can be significantly increased. As explained in connection with the process according to the invention, it is essential for the desired effect that the binder is only dissolved during the drying of the fiber web, in which temperatures above 30°C are generally reached, but not in preceding process steps where temperatures below 30°C are present.

[0020] As explained below in the inventive method for producing the support structure, it is particularly advantageous if the binder is water-soluble even at moderate temperatures and is available in fiber form. In this form, it can be used directly in the production of the fiber web forming the support structure and does not need to be added later. Since the fiber web has a high moisture content during production and is dried at an elevated temperature according to the inventive method, the binder dissolves in the water during drying and, together with the fibrillated fibers of regenerated cellulose, binds the non-fibrillated matrix fibers together. The original fiber form of the binder may be at least partially lost in this process.

[0021] Fibrillated fibers of regenerated cellulose are preferably solvent-spun fibers of regenerated cellulose. Fibrillated lyocell fibers, for example, are well-suited fibrillated fibers of regenerated cellulose.

[0022] The proportion of fibrillated fibers of regenerated cellulose is preferably at least 5% and at most 25%, particularly preferably at least 12% and at most 22%, in each case based on the mass of the support structure. These proportions allow for particularly favorable cross-linking with the non-fibrillated matrix fibers within the support structure.

[0023] The fibers of regenerated cellulose can be fibrillated by milling them in aggregates commonly used in the paper industry. The intensity of the milling affects the mean pore size and, to some extent, also the tensile strength and elongation at break of the supporting structure. Preferably, the degree of refining of the fibrillated fibers of regenerated cellulose, measured according to ISO 5267-1:1999, is at least 45°SR and at most 90°SR, and particularly preferably at least 55°SR and at most 85°SR.

[0024] The fibers of regenerated cellulose preferably have a linear density of at least 0.5 g / 10000 m (0.5 dtex) and at most 2.5 g / 10000 m (2.5 dtex) before fibrillation, and particularly preferably at least 0.8 g / 10000 m (0.8 dtex) and at most 2.0 g / 10000 m (2.0 dtex).

[0025] Before fibrillation, the regenerated cellulose fibers have a mean length-weighted length of at least 2.0 mm and at most 6.0 mm, preferably at least 3.0 mm and at most 5.0 mm. The linear density of the fibers and the fiber length are important for giving the supporting structure a favorable pore structure and strength.

[0026] According to the invention, the matrix fibers are non-fibrillated fibers. This means that the fibers have not undergone any treatment primarily intended to release fibrils from the fibers. The non-fibrillated matrix fibers can be fibers that do not contain any fibrils at all, or they can be fibrillable fibers that are not fibrillated.

[0027] Preferably, the non-fibrillated matrix fibers are not soluble in water, or if they are soluble in water, they do not dissolve in water at a temperature of 90°C or less.

[0028] Preferably, the non-fibrillated matrix fibers are selected from the group consisting of polyvinyl alcohol fibers, polyethylene terephthalate fibers, and non-fibrillated regenerated cellulose fibers, or are a mixture of at least two of these fiber types. Particularly preferably, the non-fibrillated matrix fibers comprise regenerated cellulose fibers. Lyocell fibers, modal fibers, and viscose fibers, for example, are particularly suitable non-fibrillated regenerated cellulose matrix fibers.

[0029] Preferably, the proportion of non-fibrillated matrix fibers is at least 55% and at most 80%, particularly preferably at least 55% and at most 75%, in each case based on the mass of the support structure.

[0030] Preferably, the non-fibrillated matrix fibers have a mean length-weighted length of at least 2.5 mm and at most 6.0 mm, and particularly preferably at least 3.0 mm and at most 5.0 mm. Preferably, the non-fibrillated matrix fibers have a mean thickness of at least 2 µm and at most 14 pm, and particularly preferably at least 4 pm and at most 10 pm.

[0031] Preferably, the binder dissolves in water at a temperature of 75°C, but not in water at a temperature of 35°C, and particularly preferably, the binder dissolves in water at a temperature of 60°C, but not in water at a temperature of 40°C.

[0032] Preferably, the binder is selected from the group consisting of hydrolyzed polyvinyl acetate and polyvinyl alcohol, or is a mixture thereof.

[0033] Preferably, the binder is present at least partially in the form of fibers. In principle, it is advantageous to introduce the binder into the production of the support structure in the form of fibers. As described in more detail below, the binder typically dissolves at least partially during production and adheres to the non-fibrillated matrix fibers. This, in combination with the fibrillated fibers of regenerated cellulose, results in the favorable mechanical properties of the support structure. However, in some embodiments, the fiber structure of the binder originally introduced into the production process can still be detected in the finished electrolyte component.

[0034] The proportion of the binder is preferably at least 7% and at most 28%, particularly preferably at least 10% and at most 25%, in each case based on the mass of the support structure.

[0035] The support structure may also contain inorganic particles. Preferably, the inorganic particles are selected from the group consisting of silicon dioxide (SiO2), titanium dioxide (TiO2), aluminum oxide (α12O3), magnesium oxide (MgO), zinc oxide (ZnO), and zirconium oxide (ZrO2), or are a mixture of two or more of these substances, wherein the proportion of the inorganic particles in the support structure is at most 10%, and particularly preferably at least 1% and at most 8%, in each case based on the mass of the support structure.

[0036] The special composition of the support structure allows the basis weight and thickness of the support structure to be significantly lower than is usual in the prior art for fiber-based support structures.

[0037] Preferably, the basis weight of the support structure is at least 3.0 g / m². 2 and at most 20.0 g / m² 2 , particularly preferably at least 4.0 g / m³ 2 and at most 15.0 g / m² 2and especially preferably at least 5.0 g / m² 2 and at most 10.0 g / m² 2 The basis weight can be determined according to ISO 536:2019. A particular advantage of the invention is that such high energy absorption capacity can be achieved at such low basis weights. According to the inventor's findings, this is due to a synergistic effect of the fibrillated fibers of regenerated cellulose and the binder, which cause the cross-linking of the non-fibrillated matrix fibers.

[0038] Preferably, the thickness of the support structure is at least 5 pm and at most 60 pm, particularly preferably at least 10 pm and at most 50 pm, and most preferably at least 15 pm and at most 30 pm. The thickness can be determined according to ISO 534:2011.

[0039] The porosity of the support structure is important for absorbing a large quantity of electrolyte. Therefore, a high porosity is advantageous, while the strength of the support structure must not be too low. Porosity is the ratio of the pore volume to the total volume of the support structure and is usually expressed as a percentage. Preferably, the porosity is at least 60% and at most 90%, and particularly preferably at least 65% and at most 85%. These ranges combine favorable porosity with sufficiently high strength. The porosity can be measured, for example, by mercury porosity analysis or approximated from the thickness according to ISO 534:2011, the basis weight according to ISO 536:2019, and the density and mass fractions of the components.

[0040] The porosity of the support structure can also be characterized by its air permeability. The air permeability, measured at a pressure difference of 1 kPa, is preferably at least 5000 cm². 3 / (cm 2 -min) and at most 80000 cm 3 / (cm 2 -min), especially preferably at least 6000 cm 3 / (cm 2 -min) and at most 70000 cm 3 / (cm 2 -min). Air permeability can be determined according to ISO 2965:2019.

[0041] Although the test method according to ISO 2965:2019 is not directly intended for such support structures, it can nevertheless be applied without difficulty and, due to the large range of air permeability that the support structures for electrolyte components according to the invention can exhibit, other test methods, such as the Gurley air permeability test according to ISO 5636-5:2013, cannot be used.

[0042] A key aspect improved by the electrolyte components according to the invention is the mechanical properties of the support structure they contain. These properties include tensile strength and elongation at break, as well as energy absorption capacity, which is discussed in more detail below. The following discussion focuses on such mechanical properties of the support structure, which are also claimed in the appended claims. These are always mechanical properties of the support structure in isolation, i.e., before its pores are filled with the electrolyte to produce the electrolyte component. These properties may depend on the direction in which the sample was removed from the support structure.Generally, those skilled in the art distinguish between the machine direction, which is the direction in which the fiber web forming the support structure runs through the machine during manufacturing, and the transverse direction orthogonal to this direction, lying in the plane of the fiber web. Preferably, the tensile strength in the machine direction is at least 2 N / 15 mm and at most 25 N / 15 mm, more preferably at least 3 N / 15 mm and at most 20 N / 15 mm. Preferably, the elongation at break in the machine direction is at least 2.0% and at most 8.0%, more preferably at least 2.5% and at most 7.0%. The tensile strength and the elongation at break can be determined according to ISO 1924-2:2008.

[0043] The support structure of the electrolyte components according to the invention exhibits a particularly favorable mechanical energy absorption capacity. This represents a key aspect of the invention because, due to its high energy absorption capacity, the support structure can be quickly filled with the electrolyte and further processed during the manufacture of an electrochemical cell without tearing. The energy absorption capacity (tensile energy absorption, TEA) can be determined according to ISO 1924-2:2008. The mechanical energy absorption capacity can also be characterized by the TEA index. The TEA index is the ratio of the energy absorption capacity (TEA) to the basis weight, determined according to ISO 536:2019. Since the energy absorption capacity is approximately proportional to the basis weight for the same composition, the TEA index characterizes the energy absorption capacity independently of the basis weight, thus describing an intrinsic energy absorption capacity of the support structure.

[0044] Preferably, the energy absorption capacity of the support structure in the machine direction is at least 4 J / m². 2 and at most 80 J / m² 2 , particularly preferably at least 7 J / m² 2 and at most 70 J / m² 2 .

[0045] Preferably, the TEA index of the support structure in the machine direction is at least 700 J / kg and at most 6000 kJ / kg, particularly preferably at least 750 J / kg and at most 5000 J / kg.

[0046] There are no special requirements for solid or gel electrolytes.

[0047] Preferably, the electrolyte comprises a polymer and a salt, wherein the polymer is selected from the group consisting of polyethers, in particular polyethylene oxide or polypropylene oxide; polycarbonates; polysaccharides; polyimides; polyesters, in particular polycaprolactone; polyurethanes; polyphosphazenes; polysiloxanes, in particular polydimethylsiloxane; polyacrylonitrile; polyacrylamide; polymethyl methacrylate; polyvinyl alcohol; polyvinylpyrrolidone; polyvinylidene fluoride; and polyvinylidene fluoride hexafluoropropene, or wherein the polymer is a derivative of one of these polymers or a mixture of two or more of these polymers or their derivatives.

[0048] Preferably, the salt in the electrolyte is selected from the group consisting of lithium bis(trifluoromethylsulfonyl)amide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium perchlorate, lithium fluoride, sodium bis(trifluoromethylsulfonyl)amide, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetrafluoroborate, sodium fluoride and sodium tetrafluoroborate, or is a mixture of two or more of these salts.

[0049] Preferably, the electrolyte comprises inorganic particles, wherein the inorganic particles are formed by particles of oxides, mixed oxides, or phosphates containing silicon, titanium, aluminum, zirconium, lanthanum, lithium, or sodium. Particularly preferably, the inorganic particles are selected from the group consisting of lithium lanthanum zirconium oxide (LLZO) particles, lithium zirconium phosphate (LZP) particles, and lithium titanium phosphate (LTP) particles, or are a mixture of two or more of these particle types.

[0050] The electrolyte is particularly preferably in gel form and comprises an organic solvent or incompletely polymerized monomers.

[0051] Another aspect of the invention relates to electrochemical elements comprising an electrolyte component according to the invention.

[0052] The electrochemical element comprises an anode, a cathode and an electrolyte component according to one of the aforementioned embodiments.

[0053] Preferably, the electrochemical element is a lithium-ion battery.

[0054] Another aspect of the invention relates to a method for producing a support structure. The method according to the invention comprises steps A to C.

[0055] A - Providing an aqueous suspension comprising solids and water in a headbox of a paper machine, wherein the solids are formed by at least 5% and at most 30% fibrillated fibers of regenerated cellulose, by at least 50% and at most 90% non-fibrillated matrix fibers and by at least 5% and at most 30% of a binder, wherein the percentages refer to the mass of the solids in the suspension and

[0056] B- Dewatering the suspension flowing from the headbox of step A onto a sieve to form a fiber web,

[0057] C - Drying the fiber web from step B by applying heat so that the fiber web has a temperature of at least 90°C and at most 120°C in order to form a support structure,

[0058] wherein the non-fibrillated matrix fibers in the suspension of step A have no melting point or, if they have a melting point, it is at least 120°C, and the non-fibrillated matrix fibers in the suspension of step A are not soluble in water or, if they are soluble in water, are not soluble in water at a temperature of 80°C or less, and the non-fibrillated matrix fibers in the suspension of step A have a mean length-weighted length of at least 2.0 mm and at most 8.0 mm and a mean length-weighted thickness of at least 1 pm and at most 16 pm, and wherein the binder in the suspension of step A is formed by fibers that are soluble in water at a temperature of 80°C but not in water at a temperature of 30°C.

[0059] In addition to the advantages gained, according to the inventor's findings, through the use of fibrillated fibers of regenerated cellulose in combination with the binder, which have already been explained with regard to the support structure of the electrolyte component according to the invention, a special aspect of the process according to the invention is that in step A the binder is provided in the form of fibers, which are subsequently dissolved during drying in step C by the high water content of the fiber web and the high temperature, thus, according to a further development, bonding the non-fibrillated matrix fibers together. The manufacturing process is simplified because the binder does not need to be added later, but is already contained in the suspension in step A. However, in order for the binder to be added in step A, it is essential that it is not dissolved before drying in step C.Therefore, the binder must not dissolve in water at a temperature of less than 30°C, but must dissolve in water at a temperature of less than 80°C in order to bond the non-fibrillated matrix fibers together in step C of drying.

[0060] According to the inventor, another special aspect of the process according to the invention lies in the use of fibrillated fibers of regenerated cellulose. In step B, a fiber web is formed from the aqueous suspension of step A, which must already possess sufficient strength before step C, the drying step. This is particularly important when steps A to C are carried out on a paper machine where the suspension from step A is dewatered on a wire in step B. After step B, the fiber web must be lifted from the wire and transferred to the drying unit for drying in step C. At this point, neither the non-fibrillated matrix fibers are sufficiently cross-linked, nor is the binder sufficiently dissolved to bond the matrix fibers together.According to the inventor's findings, the strength of the fiber web is largely due to the fibrillated fibers of regenerated cellulose, which can already form hydrogen bonds between the fibrils during dewatering in step B.

[0061] Preferably, the paper machine in step A is a skewed wire paper machine.

[0062] Preferably, the process includes an additional step between steps B and C in which the fiber web is dewatered by mechanical pressure.

[0063] Preferably, drying in step C is carried out by contacting the fiber web with at least one heated drying cylinder.

[0064] The fibrillated fibers of regenerated cellulose in the support structure of step C are preferably solvent-spun fibers of regenerated cellulose.

[0065] The proportion of fibrillated fibers of regenerated cellulose in the support structure of step C is preferably at least 5% and at most 25%, particularly preferably at least 12% and at most 22%, in each case based on the mass of the support structure after drying of step C.

[0066] Preferably, the fineness of the fibrillated fibers of regenerated cellulose in the support structure of step C, measured according to ISO 5267-1:1999, is at least 45°SR and at most 90°SR, particularly preferably at least 55°SR and at most 85°SR.

[0067] The fibers of regenerated cellulose in the support structure of step C preferably have a linear density of at least 0.5 g / 10000 m (0.5 dtex) and at most 2.5 g / 10000 m (2.5 dtex) before fibrillation, and particularly preferably at least 0.8 g / 10000 m (0.8 dtex) and at most 2.0 g / 10000 m (2.0 dtex). The fibers of regenerated cellulose in the support structure of step C have a mean length-weighted length of at least 2.0 mm and at most 6.0 mm, and preferably at least 3.0 mm and at most 5.0 mm, before fibrillation.

[0068] Preferably, the non-fibrillated matrix fibers in the support structure of step C are not soluble in water, or if they are soluble in water, they do not dissolve in water at a temperature of 90°C or less.

[0069] Preferably, the non-fibrillated matrix fibers in the support structure of step C are selected from the group consisting of polyvinyl alcohol fibers, polyethylene terephthalate fibers, and non-fibrillated regenerated cellulose fibers, or are a mixture of at least two of these fiber types. Particularly preferably, the non-fibrillated matrix fibers comprise regenerated cellulose fibers.

[0070] Preferably, the proportion of non-fibrillated matrix fibers in the support structure of step C is at least 55% and at most 80%, particularly preferably at least 55% and at most 75%, in each case based on the mass of the support structure after drying of step C.

[0071] Preferably, the non-fibrillated matrix fibers in the support structure of step C have a mean length-weighted length of at least 2.5 mm and at most 6.0 mm, and particularly preferably at least 3.0 mm and at most 5.0 mm.

[0072] Preferably, the non-fibrillated matrix fibers in the support structure of step C have an average thickness of at least 2 pm and at most 14 pm, and particularly preferably at least 4 pm and at most 10 pm.

[0073] Preferably, the binder in the support structure of step C is a binder that dissolves in water at a temperature of 75°C but not in water at a temperature of 35°C, and particularly preferably, the binder in the support structure of step C dissolves in water at a temperature of 60°C but not in water at a temperature of 40°C. Note that these temperature specifications only characterize the solubility of the binder in water, but do not define the temperature at which step C is actually carried out.

[0074] Preferably, the binder in the support structure of step C is selected from the group consisting of hydrolyzed polyvinyl acetate and polyvinyl alcohol, or a mixture thereof. The proportion of the binder in the support structure of step C is preferably at least 7% and at most 28%, more preferably at least 10% and at most 25%, in each case based on the mass of the support structure after drying of step C.

[0075] Preferably, the binder comprises fibers made of hydrolyzed polyvinyl acetate, fibers made of polyvinyl alcohol, or a mixture of these fibers. An example of a suitable binder in fiber form is the fibers offered under the name KURALON.

[0076] In a preferred embodiment of the process, the fibers forming the binder in step A have a linear density of at least 0.05 g / 10000 m (0.05 dtex) and at most 5.0 g / 10000 m (5.0 dtex), particularly preferably at least 0.05 g / 10000 m (0.05 dtex) and at most 2.5 g / 10000 m (2.5 dtex).

[0077] In a preferred embodiment of the method, the fibers forming the binder in step A have a mean length-weighted length of at least 2 mm and at most 6 mm, particularly preferably at least 3 mm and at most 5 mm.

[0078] In a preferred embodiment of the process, the process according to step C further comprises a step D of filling the support structure with a solid or gel-like electrolyte to form an electrolyte component according to the invention. Particularly preferably, the electrolyte comprises a polymer, and the process further comprises a step E of polymerizing the polymer in the electrolyte component of step D. Most preferably, the polymerization in step E is carried out by a ring-opening polymerization, for example of 1,3-dioxolane, or a chain polymerization, for example of vinylene carbonate with a radical initiator, such as azobis(iosbutyronitrile) or dibenzoyl peroxide. The filling in step D and the polymerization in step E can also be carried out during the fabrication of the electrochemical element.

[0079] In this preferred embodiment of the process, the support structure of step C can also contain inorganic particles. Preferably, the inorganic particles are selected from the group consisting of silicon dioxide (SiO2), titanium dioxide (TiO2), aluminum oxide (α12O3), magnesium oxide (MgO), zinc oxide (ZnO), and zirconium oxide (ZrO2), or are a mixture of two or more of these substances, wherein the proportion of the inorganic particles in the support structure of step C is at most 10%, and particularly preferably at least 1% and at most 8%, in each case based on the mass of the support structure after drying of step C. Preferably, the basis weight of the support structure after drying of step C is at least 3.0 g / m². 2 and at most 20.0 g / m² 2 , particularly preferably at least 4.0 g / m³ 2 and at most 15.0 g / m² 2 and especially preferably at least 5.0 g / m² 2 and at most 10.0 g / m² 2The basis weight can be determined according to ISO 536:2019.

[0080] Preferably, the thickness of the support structure of step C is at least 5 pm and at most 60 pm, more preferably at least 10 pm and at most 50 pm, and most preferably at least 15 pm and at most 30 pm. The thickness can be determined according to ISO 534:2011.

[0081] Preferably, the porosity of the support structure of step C is at least 60% and at most 90%, more preferably at least 65% and at most 85%. The porosity can be measured, for example, by mercury porosimetry or calculated approximately from the thickness according to ISO 534:2011, the areal weight according to ISO 536:2019, and the density and mass fractions of the components.

[0082] The air permeability of the support structure of step C, measured at a pressure difference of 1 kPa, is preferably at least 5000 cm². 3 / (cm 2 -min) and at most 80000 cm3 / (cm 2 -min), especially preferably at least 6000 cm 3 / (cm 2 -min) and at most 70000 cm 3 / (cm 2 -min). Air permeability can be determined according to ISO 2965:2019.

[0083] Preferably, the tensile strength of the support structure of step C in the machine direction is at least 2 N / 15 mm and at most 25 N / 15 mm, more preferably at least 3 N / 15 mm and at most 20 N / 15 mm. Preferably, the elongation at break of the support structure of step C in the machine direction is at least 2.0% and at most 8.0%, more preferably at least 2.5% and at most 7.0%. The tensile strength and the elongation at break can be determined according to ISO 1924-2:2008.

[0084] Preferably, the energy absorption capacity of the support structure of step C in the machine direction is at least 4 J / m². 2 and at most 80 J / m² 2 , particularly preferably at least 7 J / m² 2 and at most 70 J / m² 2 .

[0085] Preferably, the TEA index of the support structure of step C in the machine direction is at least 700 J / kg and at most 6000 kJ / kg, particularly preferably at least 750 J / kg and at most 5000 J / kg.

[0086] BRIEF DESCRIPTION OF THE FIGURES Fig. 1 shows an example of a scanning electron microscope image of a support structure for an electrolyte component according to the invention.

[0087] DESCRIPTION OF SOME PREFERRED EXECUTIONS AND COMPARISON WITH NON-INDUCTIVE EXECUTIONS

[0088] The advantages of the invention will be demonstrated using exemplary electrolyte components according to the invention, comprising a support structure, in comparison to non-inventive examples.

[0089] Several support structures were prepared for the production of the electrolyte component. According to step A of the process according to the invention, an aqueous suspension comprising water, fibrillated fibers of regenerated cellulose, non-fibrillated matrix fibers, and a binder in the form of fibers was provided. The composition of the aqueous suspensions is given in Table i, where ID denotes the support structure and the numbers are to be understood as percentages based on the mass of the solids in the suspension and, correspondingly, also as the composition of the support structure based on the mass of the support structure.

[0090] Table 1: Composition of the suspensions and support structures for electrolyte components according to the invention

[0091] ID CEL MAT1 MAT2 BIN

[0092] Soi 20 0 60 20

[0093] S02 20 0 60 20

[0094] S03 20 0 60 20

[0095] S04 20 0 60 20

[0096] S05 20 30 30 20

[0097] S06 20 30 30 20

[0098] S07 20 30 30 20

[0099] S08 20 30 30 20

[0100] S09 15 40 30 15

[0101] S10 15 40 30 15

[0102] S11 20 0 60 20

[0103] S12 20 30 30 20

[0104] S13 20 30 30 20

[0105] S14 15 40 30 15

[0106]

[0107] S15 20 20 40 20

[0108] S16 20 20 40 20

[0109]

[0110] In Table i, CEL refers to fibrillated fibers of regenerated cellulose, specifically lyocell fibers with a linear density of 1.4 g / 10000 m (1.4 dtex) before fibrillation and a mean length-weighted length of 4 mm before fibrillation, which were milled to a fineness of 82°SR. In Table 1, MÄTi denotes a first non-fibrillated matrix fiber made of polyethylene terephthalate with a linear density of 0.06 g / 10,000 m (0.06 dtex), a mean length-weighted length of 3.0 mm, and a mean length-weighted thickness of 9 pm, and MÄT2 denotes a second non-fibrillated matrix fiber made of polyvinyl alcohol with a linear density of 0.55 g / 10,000 m (0.55 dtex), a mean length-weighted length of 3.0 mm, and a mean length-weighted thickness of 14 pm. The mean length-weighted length was measured according to ISO 16065-2:2014 using the L&W Fiber Tester Plus 912+. The mean length-weighted thickness was also determined using the same instrument.

[0111] The non-fibrillated matrix fibers MÄTi were insoluble in water and had a melting point above 250°C. The non-fibrillated matrix fibers MÄT2 were insoluble in liquid water and had a melting point of approximately 200 ± 20°C. Furthermore, in Table 1, BIN denotes the binder in the form of polyvinyl alcohol fibers with a linear density of 1.2 g / 10,000 m (1.2 dtex) and a mean length-weighted length of 4 mm, which were soluble in water at a temperature of 60°C.

[0112] According to step B of the inventive process, each of the suspensions was dewatered on the screen of an inclined screen machine to form fiber webs, which were then dried at a temperature of 105°C according to step C. At this temperature, the water contained in the fiber web can evaporate, thus dissolving the binder present in fiber form. The dissolved binder adheres to the non-fibrillated matrix fibers and, in combination with the fibrillated fibers of regenerated cellulose, thus imparting the favorable mechanical properties, in particular the high energy absorption capacity, of the support structures produced from suspensions S01 to S16.

[0113] The support structures produced from the suspensions Sn, S12, S13 and S14 were additionally calendered in a rolling gap.

[0114] The essential properties of the support structures are given in Table 2. In Table 2, ID denotes the support structure, which corresponds to the designation of the suspension from Table 1, and BW denotes the basis weight in g / m². 2 According to ISO 536:2019, TH is the thickness in pm; according to ISO 534:2011, PO is the porosity in %, AP is the air permeability at 1 kPa pressure difference in cm. 3 / (cm 2 -min) according to ISO 2965:2019, TS the tensile strength in machine direction in N / 15 mm according to ISO 1924-2:2008, EL the elongation at break in machine direction in % according to ISO 1924-2:2008, TEA the energy absorption capacity in machine direction in J / m 2 According to ISO 1924-2:2008 and TEA-I, the TEA index in J / kg is the quotient of the energy absorption capacity TEA and the basis weight BW.

[0115] Table 2: Properties of the support structures for electrolyte components according to the invention ID BW TH PO AP TS EL TEA TEA-I

[0116] S01 15.7 46.7 74 6245 17.6 5.5 41.4 2640

[0117] S02 9,8 31,6 76 12906 9,1 4,9 19,7 2008

[0118] S03 7,7 25,2 77 24676 5,5 4,1 10,4 1350

[0119] S04 6,3 21,4 77 51531 3,7 3,5 6,1 963

[0120] S05 15,1 45,8 76 6701 H,3 4,9 25,7 1703

[0121] S06 10,0 31,0 77 13228 6,2 4,6 14,0 1395

[0122] S07 8,4 27,0 77 16045 5,4 5,1 13,4 1593

[0123] S08 5,8 19,7 79 28265 2,7 5,1 7,0 1198

[0124] S09 7,4 22,2 76 14658 3,9 5,1 10,2 1375

[0125] S10 5,7 17,7 77 25554 2,8 6,8 9,6 1675

[0126] S11 7,2 17,4 68 11543 6,4 3,8 10,4 1444

[0127] S12 8,8 15,1 58 11944 6,6 4,5 13,7 1557

[0128] S13 6,2 12,5 64 19421 4,0 4,8 9,8 1581

[0129] S14 7,8 16,0 64 14565 5,9 4,0 H,8 1513

[0130] S15 7,3 20,3 73 11236 3,9 3,6 6,8 924

[0131] S16 5,4 16,5 76 24832 2,6 4,1 5,1 951

[0132]

[0133] A scanning electron microscope image of the support structure S15 according to the invention is shown in Fig. 1. In Fig. 1, non-fibrillated matrix fibers 1 can be seen, forming a porous structure in which the fibrillated fibers of regenerated cellulose 2 are embedded. At the intersection points of the fibers 3, the binder can form a bond between the non-fibrillated matrix fibers 1, thus contributing to a high energy absorption capacity. The fiber structure of the binder is largely lost because the fibers detached during the drying of the support structure in step C.

[0134] The support structures S01 to S16 from Table 2 were impregnated with polyethylene oxide and lithium bisfo-xalato)borate dissolved in acetonitrile and subsequently dried to obtain electrolyte components according to the invention. It was found that the support structures could be impregnated with the electrolyte much more reliably than commercially available support structures known from the prior art. In particular, the number of failures was considerably reduced.

[0135] The conductivity of these electrolyte components was determined by impedance spectroscopy at a temperature of 60°C and a contact pressure of 0.5 MPa. The electrolyte components exhibited a conductivity of approximately 0.1 mS / cm to 0.05 mS / cm.

[0136] The support structure S09 according to the invention was further used to manufacture a lithium iron phosphate battery. The cathode of the lithium iron phosphate battery consisted essentially of lithium iron phosphate, and the anode of metallic lithium. The support structure was arranged between the cathode and the anode and filled with the electrolyte. The electrolyte contained 1 M lithium difluoro(oxalato)borate dissolved in vinylene carbonate and 1 M lithium difluoro(oxalato)borate dissolved in a mixture of ethylene carbonate and diethyl carbonate. The vinylene carbonate was polymerized directly in the support structure at elevated temperature by a small amount of dibenzoyl peroxide to obtain a gel-like electrolyte with good ionic conductivity. The lithium iron phosphate battery obtained in this way could be charged and discharged as expected and, with a Coulomb efficiency of more than 99%, was comparable to commercial lithium iron phosphate batteries.

[0137] For comparison, support structures X01, X02, X03, X04, and X05, suitable for the production of electrolyte components not according to the invention, were also produced in an equivalent manner. Table 3 shows the composition of these comparative examples. In Table 3, ID denotes the support structure, and the numbers are to be understood as percentages based on the mass of the support structure. The materials designated CEL, MATi, MAT2, and BIN correspond exactly to those described for Table 1. Support structure X04 was additionally calendered in a rolling gap.

[0138] A support structure could not be produced from suspension X06 using the inclined screen machine because the strength of the fiber web was insufficient to transfer it to the press section. Although a support structure could initially be produced from suspension X07, its strength properties were already so visibly poor that further testing was abandoned.

[0139] Table 3: Composition of the suspensions and support structures for electrolyte components not according to the invention ID CEL MAT1 MAT2 BIN

[0140] Xoi 85 15 0 0

[0141] X02 70 30 0 0

[0142] X03 40 30 30 0

[0143] X04 70 30 0 0

[0144] X05 40 20 20 20

[0145] X06 3 55 17 25

[0146] X07 25 55 17 3

[0147]

[0148] The essential properties of the support structures Xoi to X05 are given in Table 4. In Table 4, ID denotes the support structure that corresponds to the designation of the support structure from Table 3, and the remaining designations BW, TH, PO, AP, TS, EL, TEA and TEA-I correspond to those in Table 2.

[0149] Table 4: Properties of support structures for electrolyte components not according to the invention

[0150] ID BW TH PO AP TS EL TEA TEA-I

[0151] Xoi 15.5 50.0 76 361 7.9 1.3 4.9 316

[0152] X02 13.1 33.8 75 618 5.4 1.5 4.0 305

[0153] X03 10.8 29.8 75 4843 2.4 1.7 1.9 176

[0154] X04 12.6 24.5 67 298 4.4 1.2 2.5 198

[0155] X05 9.7 32.3 72 4660 4.8 1.3 3.1 320

[0156]

[0157] Initially, the experiments with suspensions X06 and X07 demonstrate that the combination of fibrillated fibers of regenerated cellulose and the binder is indeed crucial for producing a support structure that exhibits sufficient strength and elongation at break, and thus high energy absorption capacity. This demonstrates a synergistic effect between the fibrillated fibers of regenerated cellulose and the binder.

[0158] A comparison of the support structures S01 to S16 for electrolyte components according to the invention with the support structures Xoi to X05, which serve as a comparison example, shows that the composition and manufacturing process according to the invention lead to a significantly higher TEA index. The support structures S01 to S16 achieve a TEA index of more than 900 J / kg, while none of the support structures Xoi to X05 even comes close to this value. This applies in particular to the support structure X05, which is very similar to the support structures S05 to S08 in terms of composition. The inventor assumes that the content of fibrillated fibers of regenerated cellulose in the support structures Xoi to X05 is too high. While this achieves good porosity, the energy absorption capacity is low.Only through the binding agent and a lower proportion of fibrillated fibers of regenerated cellulose in the intervals according to the invention can both high porosity and high energy absorption capacity be achieved.

[0159] Furthermore, the support structures Xoi to X05 of the comparative examples have a lower air permeability than the support structures S01 to S16 of the embodiments according to the invention. In conjunction with the approximately comparable porosity, this, according to the inventor's findings, indicates that the pores in the support structures Xoi to X05 of the comparative examples are more closed or exhibit high tortuosity. Such pores are not available for efficient ion transport in the electrochemical element, which is why the electrical properties of the electrochemical elements manufactured therefrom are not as favorable.

[0160] Overall, this comparison shows that the special composition of the support structures and the manufacturing process according to the invention enable the production of electrolyte components that are superior to other fiber-based support structures in terms of their processability into electrochemical components. Despite this, the electrochemical elements produced from these components exhibit good electrical properties.

Claims

delfortgroup AG H70759WO REQUIREMENTS 1. Electrolyte component for an electrochemical element, wherein the electrolyte component comprises an electrolyte and a support structure, wherein the electrolyte is a solid or a gel and the support structure has a plurality of pores which are at least partially filled by the electrolyte, and wherein the support structure contains at least 5% and at most 30% fibrillated fibers of regenerated cellulose, at least 50% and at most 90% non-fibrillated matrix fibers and at least 5% and at most 30% of a binder, wherein the percentages refer to the mass of the support structure, where the non-fibrillated matrix fibers - have no melting point or, if they have a melting point, it is at least 120°C, - do not dissolve in water or, if they do dissolve in water, do not dissolve in water with a temperature of 80°C or less, and - have a mean length-weighted length of at least 2.0 mm and at most 8.0 mm and a mean length-weighted thickness of at least 1 pm and at most 16 pm, and wherein the binder dissolves in water at a temperature of 80°C, but not in water at a temperature of 30°C.

2. Electrolyte component according to claim 1, wherein the fibrillated fibers of regenerated cellulose are fibers of regenerated cellulose spun in a solvent, in particular lyocell fibers.

3. Electrolyte component according to claim 1 or 2, wherein the proportion of fibrillated fibers of regenerated cellulose is at least 5% and at most 25%, preferably at least 12% and at most 22%, in each case based on the mass of the support structure.

4. Electrolyte component according to any of the preceding claims, wherein the degree of refining of the fibrillated fibers of regenerated cellulose, as measured according to ISO 5267-1:1999, is at least 45°SR and at most 90°SR, preferably at least 55°SR and at most 85°SR.

5. Electrolyte component according to any one of the preceding claims, wherein the fibers of regenerated cellulose have a linear density of at least 0.5 g / 10000 m (0.5 dtex) and at most 2.5 g / 10000 m (2.5 dtex), preferably at least 0.8 g / 10000 m (0.8 dtex) and at most 2.0 g / 10000 m (2.0 dtex), prior to fibrillation.

6. Electrolyte component according to any one of the preceding claims, wherein the fibers of regenerated cellulose have a mean length-weighted length of at least 3.0 mm and at most 5.0 mm prior to fibrillation.

7. Electrolyte component according to any of the preceding claims, wherein the nonfibrillated matrix fibers are not soluble in water, or, if soluble in water, are not soluble in water at a temperature of 90°C or less.

8. Electrolyte component according to any of the preceding claims, wherein the non-fibrillated matrix fibers are selected from the group consisting of fibers made of polyvinyl alcohol, fibers made of polyethylene terephthalate and non-fibrillated fibers of regenerated cellulose, or a mixture of at least two of these fiber types.

9. Electrolyte component according to any of the preceding claims, wherein the non-fibrillated matrix fibers are or comprise non-fibrillated lyocell fibers, non-fibrillated modal fibers and / or non-fibrillated viscose fibers.

10. Electrolyte component according to any of the preceding claims, wherein the proportion of non-fibrillated matrix fibers is at least 55% and at most 80%, preferably at least 55% and at most 75%, in each case based on the mass of the support structure.

11. Electrolyte component according to any of the preceding claims, wherein the non-fibrillated matrix fibers have a mean length-weighted length of at least 2.5 mm and at most 6.0 mm, preferably at least 3.0 mm and at most 5.0 mm.

12. Electrolyte component according to any of the preceding claims, wherein the non-fibrillated matrix fibers have an average thickness of at least 2 pm and at most 14 pm, preferably at least 4 pm and at most 10 pm.

13. Electrolyte component according to any one of the preceding claims, wherein the binder dissolves in water at a temperature of 75°C, but not in water at a temperature of 35°C, and preferably the binder dissolves in water at a temperature of 60°C, but not in water at a temperature of 40°C.

14. Electrolyte component according to any one of the preceding claims, wherein the binder is selected from the group consisting of hydrolyzed polyvinyl acetate and polyvinyl alcohol, or is a mixture thereof.

15. Electrolyte component according to one of the preceding claims, wherein the binder is at least partially in the form of fibers.

16. Electrolyte component according to one of the preceding claims, wherein the proportion of the binder is at least 7% and at most 28%, preferably at least 10% and at most 25%, in each case based on the mass of the support structure.

17. Electrolyte component according to one of the preceding claims, wherein the support structure contains up to 10%, preferably at least 1% and at most 8% inorganic particles, in each case based on the mass of the support structure.

18. Electrolyte component according to claim 17, wherein the inorganic particles are selected from the group consisting of silicon dioxide (SiO2), titanium dioxide (TiO2), aluminum oxide (α12O3), magnesium oxide (MgO), zinc oxide (ZnO) and zirconium oxide (ZrO2), or a mixture of two or more of these substances.

19. Electrolyte component according to one of the preceding claims, wherein the basis weight of the support structure is at least 3.0 g / m² 2 and at most 20.0 g / m² 2 , preferably at least 4.0 g / m² 2 and at most 15.0 g / m² 2 and especially preferably at least 5.0 g / m³ 2 and at most 10.0 g / m² 2 amounts.

20. Electrolyte component according to any of the preceding claims, wherein the thickness of the support structure is at least 5 pm and at most 60 pm, preferably at least 10 pm and at most 50 pm and particularly preferably at least 15 pm and at most 30 pm.

21. Electrolyte component according to one of the preceding claims, wherein the porosity of the support structure is at least 60% and at most 90%, preferably at least 65% and at most 85%.

22. Electrolyte component according to one of the preceding claims, wherein the support structure has an air permeability, measured at a pressure difference of 1 kPa, of at least 5000 cm². 3 / (cm 2 -min) and at most 80000 cm 3 / (cm 2 -min), preferably of at least 6000 cm 3 / (cm 2 -min) and at most 70000 cm 3 / (cm 2-min).23- Electrolyte component according to one of the preceding claims, wherein the tensile strength of the support structure in the machine direction is at least 2 N / 15 mm and at most 25 N / 15 mm, preferably at least 3 N / 15 mm and at most 20 N / 15 mm.

24. Electrolyte component according to one of the preceding claims, wherein the elongation at break of the support structure in the machine direction is at least 2.0% and at most 8.0%, preferably at least 2.5% and at most 7.0%.

25. Electrolyte component according to one of the preceding claims, wherein the mechanical energy absorption capacity (tensile energy absorption, TEA) of the support structure in the machine direction, as determined according to ISO 1924-2:2008, is at least 4 J / m². 2 and at most 80 J / m² 2 , preferably at least 7 J / m² 2 and at most 70 J / m² 2 amounts.

26. Electrolyte component according to one of the preceding claims, wherein the support structure has a TEA index in the machine direction of at least 700 J / kg and at most 6000 kJ / kg, preferably at least 750 J / kg and at most 5000 J / kg, wherein the TEA index is the ratio of the energy absorption capacity (TEA) according to ISO 1924-2:2008 and the basis weight determined according to ISO 536:2019.

27. Electrolyte component according to any one of the preceding claims, wherein the electrolyte comprises a polymer and a salt, the polymer being selected from the group consisting of polyethers, in particular polyethylene oxide or polypropylene oxide; polycarbonates; polysaccharides; polyimides; polyesters, in particular polycaprolactone; polyurethanes; polyphosphazenes; polysiloxanes, in particular polydimethysiloxane; polyacrylonitrile; polyacrylamide; polymethyl methacrylate; polyvinyl alcohol; polyvinylpyrrolidone; polyvinylidene fluoride and polyvinylidene fluoride hexafluoropropene, or wherein the polymer is a derivative of one of these polymers or a mixture of two or more of these polymers or their derivatives.

28. Electrolyte component according to claim 27, wherein the salt in the electrolyte is selected from the group consisting of lithium bis(trifluoromethylsulfonyl)amide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium perchlorate, lithium fluoride, sodium bis(trifluoromethylsulfonyl)amide, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetrafluoroborate, sodium fluoride, and sodium tetrafluoroborate, or a mixture of two or more of these salts.

29. Electrolyte component according to any one of the preceding claims, wherein the electrolyte comprises inorganic particles, the inorganic particles being formed by particles of oxides, mixed oxides, or phosphates containing silicon, titanium, aluminum, zirconium, lanthanum, lithium, or sodium.

30. Electrolyte component according to claim 29, wherein said inorganic particles are selected from the group consisting of lithium lanthanum zirconium oxide (LLZO) particles, lithium zirconium phosphate (LZP) particles, and lithium titanium phosphate (LTP) particles, or a mixture of two or more of these particle types.

31. Electrolyte component according to any of the preceding claims, wherein the electrolyte is gel-like and comprises an organic solvent or incompletely polymerized monomers.

32. Electrochemical element comprising an electrolyte component according to one of claims 31.

33. Electrochemical element according to claim 32, wherein the electrochemical element is a lithium-ion battery.

34. Method for producing a support structure comprising steps A to C: A - Providing an aqueous suspension comprising solids and water in a headbox of a paper machine, wherein the solids are formed by at least 5% and at most 30% fibrillated fibers of regenerated cellulose, by at least 50% and at most 90% non-fibrillated matrix fibers and by at least 5% and at most 30% of a binder, wherein the percentages refer to the mass of the solids in the suspension, B- Dewatering the suspension flowing from the headbox of step A onto a sieve to form a fiber web, C - Drying the fiber web from step B by applying heat so that the fiber web has a temperature of at least 90°C and at most 120°C in order to form a support structure, wherein the non-fibrillated matrix fibers in the suspension of step A- have no melting point or, if they have a melting point, it is at least 120°C, - do not dissolve in water or, if they do dissolve in water, do not dissolve in water with a temperature of 80°C or less, and - have a mean length-weighted length of at least 2.0 mm and at most 8.0 mm and a mean length-weighted thickness of at least 1 pm and at most 16 pm, and wherein the binder in the suspension of step A is formed by fibers that dissolve in water at a temperature of 80°C but not in water at a temperature of 30°C.

35. Method according to claim 34, wherein the fibers of the binder are at least partially dissolved during drying in step C by the water content and the temperature of the fiber web of between 90 °C and 120 °C and the non-fibrillated matrix fibers are interlinked.

36. Method according to any one of claims 34 to 36, wherein the paper machine in step A is a skew wire paper machine.

37. Method according to any one of claims 34 to 36, wherein the method includes a step between steps B and C in which the fiber web is dewatered by mechanical pressure.

38. Method according to one of claims 34 to 37, wherein the drying in step C is carried out by contact of the fiber web with at least one heated drying cylinder.

39. Method according to any one of claims 34 to 38, wherein the fibrillated fibers of regenerated cellulose in the support structure of step C are fibers of regenerated cellulose spun in a solvent.

40. Method according to any one of claims 34 to 39, wherein the proportion of fibrillated fibers of regenerated cellulose in the support structure of step C is at least 5% and at most 25%, preferably at least 12% and at most 22%, in each case based on the mass of the support structure after drying of step C.

41. Method according to any one of claims 34 to 40, wherein the degree of refining of the fibrillated fibers of regenerated cellulose in the support structure of step C, measured according to ISO 5267-1:1999, is at least 45°SR and at most 90°SR, preferably at least 55°SR and at most 85°SR.

42. Method according to any one of claims 34 to 41, wherein the fibers of regenerated cellulose in the support structure of step C have a linear density of at least 0.5 g / 10000 m (0.5 dtex) and at most 2.5 g / 10000 m (2.5 dtex), preferably at least 0.8 g / 10000 m (0.8 dtex) and at most 2.0 g / 10000 m (2.0 dtex), prior to fibrillation.

43. Method according to any one of claims 34 to 42, wherein the fibers of regenerated cellulose in the support structure of step C have a mean length-weighted length of at least 2.0 mm and at most 6.0 mm, preferably at least 3.0 mm and at most 5.0 mm, prior to fibrillation.

44. Method according to any one of claims 34 to 43, wherein the non-fibrillated matrix fibers in the support structure of step C are not soluble in water, or, if they are soluble in water, do not dissolve in water at a temperature of 90°C or less.

45. A method according to any one of claims 34 to 44, wherein the non-fibrillated matrix fibers in the support structure of step C are selected from the group consisting of fibers made of polyvinyl alcohol, fibers made of polyethylene terephthalate and non-fibrillated fibers of regenerated cellulose, or are a mixture of at least two of these fiber types.

46. ​​Method according to any one of claims 34 to 45, wherein the proportion of non-fibrillated matrix fibers in the support structure of step C is at least 55% and at most 80%, preferably at least 55% and at most 75%, in each case based on the mass of the support structure after drying of step C.

47. Method according to any one of claims 34 to 46, wherein the non-fibrillated matrix fibers in the support structure of step C have a mean length-weighted length of at least 2.5 mm and at most 6.0 mm, preferably at least 3.0 mm and at most 5.0 mm.

48. A method according to any one of claims 34 to 47, wherein the non-fibrillated matrix fibers in the support structure of step C have an average thickness of at least 2 pm and at most 14 pm, preferably at least 4 pm and at most 10 pm.

49. A method according to any one of claims 34 to 48, wherein the binder in the support structure of step C is a binder that dissolves in water at a temperature of 75°C but does not dissolve in water at a temperature of 35°C, and preferably the binder in the support structure of step C dissolves in water at a temperature of 60°C but does not dissolve in water at a temperature of 40°C.

50. A method according to any one of claims 34 to 49, wherein the binder in the support structure of step C is selected from the group consisting of hydrolyzed polyvinyl acetate and polyvinyl alcohol, or a mixture thereof.

51. Method according to any one of claims 34 to 50, wherein the proportion of the binder in the support structure of step C is at least 7% and at most 28%, preferably at least 10% and at most 25%, in each case based on the mass of the support structure after drying of step C.

52. Method according to any one of claims 34 to 51, wherein the binder comprises fibers of hydrolyzed polyvinyl acetate, fibers of polyvinyl alcohol or a mixture of these fibers.

53. Method according to any one of claims 35 to 52, wherein the fibers forming the binder in step A have a linear density of at least 0.05 g / 10000 m (0.05 dtex) and at most 5.0 g / 10000 m (5.0 dtex), preferably at least 0.05 g / 10000 m (0.05 dtex) and at most 2.5 g / 10000 m (2.5 dtex).

54. Method according to any one of claims 35 to 53, wherein the fibers forming the binder in step A have a mean length-weighted length of at least 2 mm and at most 6 mm, preferably at least 3 mm and at most 5 mm.

55. Method according to any one of claims 34 to 54, wherein the method according to step C comprises a step D of filling the support structure with a solid or gel-like electrolyte to form an electrolyte component.

56. The method of claim 55, wherein the electrolyte comprises a polymer, and wherein the method comprises a step E of polymerizing the polymer in the electrolyte component of step D.

57. The method of claim 56, wherein the polymerization in step E is carried out by a ring-opening polymerization, in particular of 1,3-dioxolane, or a chain polymerization, in particular of vinylene carbonate, with a radical initiator, in particular azo-bis(iosbutyronitrile) or dibenzoyl peroxide.

58. Method according to any one of claims 34 to 57, wherein the support structure of step C contains inorganic particles, wherein the proportion of inorganic particles in the support structure of step C is preferably at most 10% and particularly preferably at least 1% and at most 8%, in each case based on the mass of the support structure after drying of step C.

59. The method of claim 58, wherein the inorganic particles are selected from the group consisting of silicon dioxide (SiO2), titanium dioxide (TiO2), aluminum oxide (α12O3), magnesium oxide (MgO), zinc oxide (ZnO) and zirconium oxide (ZrO2), or are a mixture of two or more of these substances.

60. Method according to any one of claims 34 to 59, wherein the basis weight of the support structure after drying step C is at least 3.0 g / m² 2 and at most 20.0 g / m² 2 , preferably at least 4.0 g / m³ 2 and at most 15.0 g / m² 2 and especially preferably at least 5.0 g / m³ 2 and at most 10.0 g / m² 2 amounts.

61. Method according to any one of claims 34 to 60, wherein the thickness of the support structure of step C is at least 5 pm and at most 60 pm, preferably at least 10 pm and at most 50 pm and particularly preferably at least 15 pm and at most 30 pm.

62. Method according to any one of claims 34 to 61, wherein the porosity of the support structure of step C is at least 60% and at most 90%, preferably at least 65% and at most 85%.

63. Method according to any one of claims 34 to 62, wherein the air permeability of the support structure of step C, measured at a pressure difference of 1 kPa, is at least 5000 cm². 3 / (cm 2 -min) and at most 80000 cm 3 / (cm 2 -min), preferably at least 6000 cm 3 / (cm 2 -min) and at most 70000 cm 3 / (cm 2 -min).

64. A method according to any one of claims 34 to 63, wherein the tensile strength of the support structure of step C in the machine direction is at least 2 N / 15 mm and at most 25 N / 15 mm, preferably at least 3 N / 15 mm and at most 20 N / 15 mm.

65. A method according to any one of claims 34 to 64, wherein the elongation at break of the support structure of step C in the machine direction is at least 2.0% and at most 8.0%, preferably at least 2.5% and at most 7.0%.

66. Method according to any one of claims 34 to 65, wherein the tensile energy absorption (TEA) of the support structure of step C in the machine direction, as determined according to ISO 1924-2:2008, is at least 4 J / m 2 and at most 80 J / m² 2 , preferably at least 7 J / m² 2 and at most 70 J / m² 2 amounts.

67. Method according to any one of claims 34 to 66, wherein the support structure of step C has a TEA index in the machine direction of at least 700 J / kg and at most 6000 kJ / kg, preferably at least 750 J / kg and at most 5000 J / kg, wherein the TEA index is the ratio of the energy absorption capacity (TEA) according to ISO 1924-2:2008 and the basis weight determined according to ISO 536:2019.

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