WO2025011825A1 - Method for producing a solvent-free electrode compound and method for dispensing a supply by means of a discharge device - Google Patents

Abstract

The invention relates to a method for producing an in particular dry or solvent-free electrode compound by mixing at least one active electrode material (1), at least one conductive material (2) and at least one in particular fibrillatable polymer binder (3) in a continuous mixer (4) having a continuous kneader (5) and a gear pump (6). A small proportion of the electrode material (1) in relation to the total amount is added in a feed zone (8) together with at least a large part, preferably the total amount, of the binder (3) and plasticised in a compression zone (9) of the mixer (4). Then, the larger proportion of the electrode material (1) and the conductive material (2) is added successively in a region of a mixing zone (12) adjoining the compression zone (9) through preferably a plurality of inlet openings (10, 11). As a result, the binder (3) is sufficiently plasticised and the electrode material (1) and the conductive material (2), which contains, for example, carbon black as an essential component, are homogenised and dispersed in as stress-free a manner as possible, wherein degassing (17) takes place in the kneader (5) and/or the extruder (7).

Description

Applicant:

TROESTER GmbH & Co. KG Am Brabrinke 1-4 30519 Hanover

Process for producing a solvent-free electrode compound and a process for dispensing a template by means of a dispensing device

The invention relates to a method for producing a particularly dry or solvent-free electrode compound by mixing at least one active electrode material, at least one conductive material and at least one binder, in particular with a substantial material proportion of at least one monomer, polymer and/or resin, in a continuous mixing process of a mixer, which are plasticized and mixed in particular in a continuous kneader.

Solid-state batteries represent a promising further development of lithium-ion batteries. In solid-state batteries, a solid lithium ion conductor (or sodium ion conductor) is used as an electrolyte instead of a liquid electrolyte system. This simultaneously serves as an ion conductor between active material particles and as an ion-conductive separator between the anode and cathode. It is essential that the contact surface between the solid-state electrolyte and the active materials is equipped with as many contact points and as few cavities as possible.

When manufacturing battery electrodes, layers 50 pm to 200 pm thick must be applied to metallic current conductors at high web speeds. This is typically done using wet-chemical roll-to-roll processes from suspensions of active materials in aqueous or organic solvents. This requires a high energy input both for dispersing the active material and for drying the layer. There is an increasing desire to implement the coating in a solvent-free, i.e. dry, manner. For this, dry powder mixtures of active material, conductive additives and suitable binders must be converted into mechanically resilient layers. Polytetrafluoroethylene (PTFE), for example, can be used as a binding agent, which forms fibrils under the influence of energy, in particular shear forces.

First, the materials for the electrodes (anode and cathode) are prepared. These materials consist of active materials (such as lithium nickel manganese cobalt oxide or lithium nickel cobalt aluminum oxide) for the cathode and graphite for the anode), binders, conductive carbon black (conductive material) and other additives.

The electrode material is applied to the current collector and evenly distributed. This can be done by calendering, doctoring, screen printing or other coating techniques. The coated electrode is then calibrated and compacted. This step serves to optimize the thickness and density of the electrode coating and to ensure good adhesion between the active material and the film.

However, when the electrode material is applied, irregularities such as air inclusions can occur in the mass, which cannot be reliably eliminated even during compaction, with the result that the electrical properties are impaired. In particular, it can happen that the electrode material is too coarse and irregularly shaped for the calender feed.

To counteract this problem, the material is additionally pulverized and cooled before being fed into the calender gap. The cooled powder can be easily processed on the calender rolls.

EP 4 152 445 A1 discloses a method for producing a powder mixture for an electrode for producing a dry electrode film by preparing a powdery mixture comprising an electrode active material, a conductive material and a binder resin. In this process, the powdery mixture is kneaded to produce mixture lumps, which are then pulverized to obtain mixed powder for the electrode, which is calendered to obtain a free-standing dry electrode film. A kneading step is to bind or bond the powder particles of the electrode active material and the conductive material to each other while fibrillating the binder resin so that mixture lumps (mixed lumps) having a solid content of 100% can be formed. When the kneading is carried out at a low temperature below the temperature range defined above, it is not possible to perform fibrillation of the binder during the kneading and sufficient lump formation by the kneading. As a result, it is not possible to form a film easily during calendering. On the other hand, if kneading is carried out at an excessively high temperature, the binder may rapidly fibrilize and the resulting fibers may be undesirably cut by excessive shear forces.

EP 0 657 951 B1 also discloses a method for producing an electrode, a cathode or anode, by extruding an element comprising an electrolyte film based on an ion-conducting polymer and at least one electrode film using a corresponding nozzle, wherein the extruded material is applied to a carrier, which is preferably heated, as it exits the nozzle. The electrode is calendered by protecting it on both sides with films.

CN 1 13 937289 A describes a process in which an active electrode material, a conductive agent and a binder are mixed without solvent and the mixture is kneaded and rolled to form a flexible, dry electrode pole piece membrane.

DE 102017208220 A1 relates to a method for producing a dry film, in which a dry powder mixture is processed into the dry film, for example by a calender rolling device. The formation of the fibril structure can be supported by heatable rollers.

In a solid-state battery according to DE 102018 222 129 A1, the use of fibrillated polytetrafluoroethylene as a binder reduces the amount of binder used and therefore improves the electrical properties. The powder mixture is typically formed into the flexible composite layer by rolling, pressing or extrusion.

According to DE 102018222 142 A1, the fibrillated polytetrafluoroethylene can be produced by attrition grinding, mixing in a screw shaft or in a calender rolling device or a kneading device.

DE 102021 209 121 B4 describes a process for the solvent-free production of an electrode, wherein the binder contains a polyamide and a polypeptide which is suitable for forming fibrils under the action of a mechanical force.

In EP 2 820699 B1, shear forces are realized to form PTFE fibrils by mixing in a screw shaft, for example of an extruder. In a method for producing a carbon electrode material according to WO 2014/116 771 A1, dry materials are subjected to shear, compression and tensile forces, for example in a screw extruder, in order to achieve improved fibrillation of the binder.

EP 3 533 095 A1 describes the mixing of conductive flakes with active particles, at least one fibrillatable polymer and spherical conductive carbon particles to form a paste. A self-supporting electrode film is produced by extruding the paste and calendering or rolling.

US 2019/0280289 A1 discloses a method for producing an electrode film comprising mixing particulate materials and fibrillatable polymers with conductive flakes to form a paste, fibrillating the fibrillatable polymers, and extruding and rolling the paste into a self-supporting electrode film.

US 2006/0246 343 A1 discloses a method for producing a cathode, wherein a solvent-free composition containing PTFE, an electrically conductive carbon material and optionally also the active cathode material is provided and is fibrillated by shear forces.

It is known from US 2022 / 0 006 071 A1 that in dry electrode processes the density of the electrode film and the target loading weight of the electrode material are determined by controlling the thickness and the applied compression pressure, which is usually achieved by successive calendering passes. Unlike wet coating, independent control over the weight of the electrode material and the thickness of the electrode film is therefore limited.

In practice, insufficient mixing of the various components leads to agglomerations and air inclusions, and thus to defects that cannot be compensated for by subsequent calendering.

Stronger mixing combined with increased compression in the plasticizing zone results in excessive shear forces being transferred to the active material and the conductive material, which leads to deteriorated electrical properties. In particular, the formation of fine fibrils in the binder requires shear forces, but these are destroyed or broken down as a result of high shear forces. changed and the properties of the bound active material and the conductive material are impaired. Accordingly, inhomogeneous mixing is usually accepted and the mixture is then pulverized before rolling and compacting in order to dissolve inhomogeneities. However, this additional process step involves considerable additional effort, particularly due to the cooling required so that the mixture can be ground, as well as the interruption of the process between mixing and compaction, which has a negative impact on the manufacturing effort.

The invention is based on the object of creating a possibility of producing a homogeneous, in particular agglomeration-free mixture without additional intermediate steps, for example for homogenization. In particular, the mixture produced should be able to be fed directly to a compaction process, for example by rolling.

This object is achieved according to the invention with a method according to the features of claim 1. The further embodiment of the invention can be found in the subclaims.

According to the invention, a method is therefore provided in which a first portion of the active electrode material, in particular less than 30% of the total active electrode material added to the mixture, is added in the area of a feed zone together with a significant portion of in particular more than 70% of the total binding agent added to the mixture and plasticized in a compression zone or plasticizing zone, and at least the remaining portion of the active electrode material and the conductive material are added in an area of a mixing zone following the compression zone. The invention is based on the finding that by adding the active material step by step both at the beginning of the plasticizing zone and in the mixing zone following it, two objectives that have previously been considered incompatible in the professional world can be reconciled in a surprisingly simple manner. By melting and simultaneously mixing the portion of the active electrode material added there in conjunction with the binding agent in the plasticizing zone as a result of high pressure, high shear forces are transferred to the active material and the conductive material. Undesirable air inclusions and agglomerations can thus be reliably avoided. It has been found that this homogenized mixture in the mixing zone can gradually receive further, namely a much larger, proportion of the active electrode material can be added without agglomerations forming in this section after plasticization. Air inclusions are specifically prevented by allowing the air to escape from the mixer, which is designed as a kneader, for example, through vent openings. In addition, degassing is provided at the end of the process. As a result of the reduced shear forces prevailing in this section, impairments to the properties of the active electrode material and the conductive material are reliably avoided, which also significantly promotes the formation of fine fibrils through the targeted introduction of defined shear in the individual process zones.

A particularly advantageous embodiment of the invention is also realized in that the active electrode material and/or the conductive material is supplied in the area of the mixing zone through several inlet openings, also referred to as ports, in particular in different proportions, with the supply being regulated based on parameters recorded in situ. In particular, the distribution of the proportions is variable, so that the properties of the mixture produced in this way can be optimally adjusted and adapted to the respective requirements.

Freely deployable injection lances in each tooth or bolt of the kneader can serve as inlet openings, enabling optimal mixing of the supplied substances in a wide viscosity range.

Another, also particularly promising embodiment of the invention is realized by adding the active electrode material together with the conductive material through the same inlet opening in the mixing zone. This creates very good mixing with a quantity ratio predetermined by the proportions, so that high requirements for the homogeneous distribution of the different mixture components can be met with reproducible accuracy.

In principle, the mixing could be achieved by a co-rotating twin-screw extruder. However, it is particularly advantageous if the mixing process is carried out using an oscillating single-shaft mixer. The oscillating single-shaft mixer, also known as a kneader, avoids undesirable peaks in shear stress. At the same time, monitoring of the process temperatures of the actual product temperature can be easily implemented, in particular by means of freely deployable temperature sensors in each tooth or bolt of the continuous kneader, so that the mixing process can be continuously monitored and controlled accordingly. By controlling the temperature, conclusions can also be drawn about the homogeneity of the mixture. The mixture is preferably discharged using a positive displacement pump, in particular a gear pump through a nozzle.

Furthermore, it has proven particularly promising if the active electrode material and/or the conductive material is added a short distance in front of the outlet opening in the direction of flow of the mixture, depending on the shear sensitivity. By adding the active electrode material or the conductive material as late as possible, the residence time within the mixer and thus the effect of shear forces is kept to a minimum. Since inadequate mixing can lead to agglomerations, constant monitoring of possible accumulations is particularly effective.

A further, also particularly promising modification of the invention is achieved in that the discharged mixture is compacted by rolling or rollers, in particular by calendering, so that the desired layer thickness can be produced in particular between several calender rollers arranged in pairs.

The mixture produced and compacted in this way can be self-supporting and can therefore be fed for further processing, for example by means of simple support rollers. However, a modification of the invention in which the mixture is applied to a carrier, in particular a coated carrier, serving as a current conductor, in particular a metal foil, is particularly advantageous, so that the composite produced can be used in battery production without further processing steps. In addition, or as an alternative to the carrier, a metallic layer can also be produced together with the mixture, for example by coextrusion or in the outlet nozzle.

In another particularly expedient embodiment of the invention, the addition of the active electrode material and the conductive material, in particular the distribution via various inlet openings, takes place depending on measured temperature values within the mixer, so that not only the mixture can be optimally adjusted by the addition.

According to a particularly advantageous embodiment of the invention, at least one opening for volatile components, designed in particular as a degassing opening, is provided in the flow direction of the mixture in front of the outlet opening in order to remove undesirable To reliably remove air inclusions in the mixture. For example, the outlet opening can be connected to a vacuum system.

Preferably, the mixer, in particular the kneader, or the extruder are operated in such a way that a shear force sufficient to produce fibrils in the binder is generated. In this way, the pressure and in particular the oscillating movement can produce a film or a layer, which is then transferred to a current collector foil in a calender gap, whereby both sides can also be coated simultaneously.

In a final step, the products are then cut to size as required and the individual parts are stacked accordingly to produce the finished battery cell.

Of course, the mixture is not limited to electrode material, conductive material and binder. Rather, other auxiliary materials, including nanoparticles, can also be added to the mixture in order to improve the electrical properties of the product to be manufactured through faster conversion.

It is particularly advantageous if the monomer, polymer or resin of the binder is transferred to the molding process immediately after mixing, for example in a continuous kneader, as the material remains in a molten state in which the molecules have a higher mobility. This enables better alignment, especially of polymer chains, and promotes the formation of fibrils along the flow direction during the extrusion process. In-situ fibrillation increases the strength and stiffness of the electrode mass, which in turn is advantageous for the free-standing film concept. Immediate molding after mixing minimizes the time the monomer, polymer and/or resin remains in a molten state. This reduces thermal degradation and enables efficient processing. The direct connection between mixing and molding allows the process parameters to be better controlled and the desired material properties to be optimized in a more targeted manner. The resin can be a natural resin and/or a synthetic resin.

The above advantages of directly forming the mixture in a molten state, for example in a “roller-head” process, can also be achieved by using a ready-mix. The mixing of the active electrode material with the binder and the electrically conductive additive is then carried out in an upstream, separate process so that the finished mixture can be fed in.

The object of the invention is further achieved by the fact that a discharge device with an extruder or a gear pump, which are in particular independently driven, is connected upstream of the calendering process for compacting the template. In addition to the continuous conveying and the necessary pressure build-up, the discharge device also influences the packing density of the mixture and provides the adapted template for the calender rolls by means of a nozzle, in particular a wide spray nozzle. This achieves independent control over the loading weight of the electrode material and the thickness of the electrode film.

The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and is described below. This shows in a schematic diagram

Fig. 1 shows a process for producing an electrode compound by means of a kneader;

Fig. 2 shows a variant of the process shown in Figure 1 with an extruder instead of a gear pump.

The method according to the invention for producing a particularly dry or solvent-free electrode compound is explained in more detail below with reference to Figures 1 and 2. The method comprises mixing at least one active electrode material 1, at least one conductive material 2 and at least one fibrillatable monomeric, polymeric and/or resinous binder 3 in a continuous mixer 4, which in a variant shown in Figure 1 comprises a continuous kneader 5 in connection with a gear pump 6 and in a variant shown in Figure 2 comprises an extruder 7. A small proportion of the electrode material 1 in relation to the total amount is added in a feed zone 8 together with at least a large part, preferably the total amount of the binder 3 and plasticized in a compression zone 9 of the mixer 4.

Subsequently, the larger portion of the electrode material 1 and the conductive material 2 are added successively through preferably several inlet openings 10, 11 in a region of a mixing zone 12 adjoining the compression zone 9. As a result, the binder 3 is sufficiently plasticized and the electrode material 1 and the, for example, Conductive material 2 containing soot as an essential component is homogenized and dispersed as stress-free as possible, with degassing 17 taking place in the kneader 5 and/or the extruder 7. The mixture is then formed into a continuous film-like template 14 in a nozzle 13, in particular a slot nozzle, by means of the gear pump 6 or the extruder 7. The desired layer thickness of the template 14 is produced between calender rollers 15 arranged in pairs, optionally on a current collector foil 16. According to the invention, material-friendly mixing is achieved by targeted introduction of the shear forces in different process zones of the feed zone 8, the compression zone 9 and the mixing zone 12 and the distribution of the raw material feed to preferably up to four inlet openings 10, 11.

REFERENCE NUMERALS LIST

1 electrode material

2 conductive material

3 binders

4 mixers

5 kneaders

6 gear pump

7 extruders

8 catchment area

9 compression zone

10 inlet opening

11 inlet opening

12 mixing zone

13 nozzle

14 template

15 calender rolls

16 current collector foil

17 Degassing/Venting

Claims

PATENT CLAIMS 1. Method for producing an electrode compound, in particular a solvent-free one, by mixing at least one active electrode material (1), at least one conductive material (2) and at least one binder (3), in particular with a substantial material proportion of a monomer, polymer and/or resin, in a continuous mixing process, characterized in that a first proportion of the active electrode material (1) of in particular less than 30% of the total active electrode material (1) fed to the mixture is added in the region of a feed zone (8) together with a substantial proportion of the total binder (3) fed to the mixture and plasticized in a compression zone (9) and at least a further proportion of the active electrode material (1) and the conductive material (2) is added in a region of a mixing zone (12) adjoining the compression zone (9). 2. Method according to claim 1, characterized in that the active electrode material (1) and/or the conductive material (2) is supplied in the region of the mixing zone (12) through a plurality of inlet openings (10, 11) in particular in different proportions. 3. Method according to claim 1 or 2, characterized in that in the mixing zone (12) the active electrode material (1) is added together with the conductive material (2) through the same inlet opening (10, 11). 4. Method according to at least one of the preceding claims, characterized in that the mixing process is carried out by means of an oscillating single-shaft mixer, in particular a kneader (5). 5. Method according to at least one of the preceding claims, characterized in that the discharged mixture is compacted by rolling or rolling, in particular by calendering. 6. Method according to at least one of the preceding claims, characterized in that the mixture is applied to a current conductor, in particular a coated carrier, or a current collector foil (16). 7. Method according to at least one of the preceding claims, characterized in that the addition of the active electrode material (1) and the conductive material (2), in particular the distribution via different inlet openings (10, 11), takes place as a function of measured temperature values within the mixer (4). 8. Method according to at least one of the preceding claims, characterized in that in the flow direction of the mixture upstream of the outlet opening at least one outlet opening for volatile components, in particular designed as a degassing device (17), is provided. 9. Method according to at least one of the preceding claims, characterized in that the mixer (4) is operated in such a way that a shear force sufficient for the formation of fibrils in the binder (3) is generated. 10. Method for dispensing a template by means of a dispensing device, wherein the dispensing device has at least one nozzle, for example a wide spray nozzle, and at least one extruder and/or a pump, in particular a gear pump, characterized in that a supplied mixture in the plasticized state is discharged through the nozzle as a template and is then compacted to a certain thickness by rolling, in particular calendering.