Method for producing an electrode of an energy accumulator, energy accumulator, and vehicle

Abstract

In a method for producing an electrode of an energy accumulator, active material, additives and binder material are dry-mixed to form a powder mixture. The method further involves calendering the powder mixture to form an electrode film and laminating the electrode film onto a current collector to form an electrode foil. In the method, the electrode foil is singulated to form an electrode. The method further involves defluorinating the electrode film and / or the electrode foil and / or the electrode.

Description

[0001] 23-3764

[0002] - 1 -

[0003] Description

[0004] Method for manufacturing an electrode of an energy storage device, energy storage device and vehicle

[0005] The invention relates to a method for manufacturing an electrode of an energy storage device. The invention further relates to an energy storage device and a vehicle.

[0006] Polytetrafluoroethylene (PTFE) can be used as a processing aid and binder for the dry processing of electrodes for battery cells. An example of this in the prior art is US2013157141A1. Under mechanical stress, PTFE forms a network of fibrils, bonding the powdered electrode materials into a stable, free-standing film. This enables sustainable and environmentally friendly electrode production without the use of carrier solvents such as N-methyl-2-pyrrolidone (NMP). However, a major disadvantage of PTFE lies in its chemical reactivity with alkali metals such as lithium and sodium. This reaction leads, in particular, to the defluorination of PTFE and the formation of metal fluorides. In lithium-ion and sodium-ion batteries, the PTFE reacts irreversibly with lithium or sodium, rendering these ions unusable for energy storage.This leads to a loss of capacity and a reduction in the energy of the battery cell.

[0007] The object underlying the invention is to provide a method for the dry production of an electrode of an energy storage device, as well as a corresponding energy storage device and a vehicle.

[0008] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are characterized in dependent claims 23-3764.

[0009] - 2 -

[0010] According to a first aspect, the invention relates to a method for manufacturing an electrode of an energy storage device.

[0011] The process comprises mixing active material, additives, and binder material into a powder mixture, calendering the powder mixture into an electrode film, laminating the electrode film onto a current collector to form an electrode foil, and singulating the electrode foil into the electrode. Furthermore, the process includes defluorinating the electrode film and / or the electrode foil and / or the electrode.

[0012] For example, the aforementioned formulation components, such as active material, additives, and binder, are dosed in the appropriate ratios before being mixed into a powder mixture. The additives, for instance, include substances that create pores in the electrode or provide electrical conductivity. The mixing process involves, for example, a dry mixture. Polytetrafluoroethylene (PTFE) is used as a binder. Under mechanical stress (shear), the PTFE forms a network of fibrils, which binds the powdered materials of the electrode into a free-standing film.

[0013] In calendering, the powder mixture or the freestanding film is compressed into an electrode film, for example by one or more rotating pairs of rollers.

[0014] During lamination, the electrode film is laminated onto a copper foil, for example. Cathode active materials are laminated onto an aluminum foil, and anode active materials onto a copper foil. The copper or aluminum foil can be coated with an electrically conductive adhesion promoter. Such adhesion promoters, also called primers, are known from DE102004014383A1. 23-3764

[0015] - 3 -

[0016] Singulation of the electrode foil describes a separation process in which the electrode foil is divided into several smaller electrode segments. Singulation can be carried out mechanically, for example, by cutting.

[0017] Defluorination can be carried out, for example, after calendering the powder mixture into an electrode film, whereby the electrode film is defluorinated. Alternatively or additionally, defluorination can be carried out after laminating the electrode film onto a current collector, whereby the electrode foil is defluorinated. Alternatively or additionally, defluorination can be carried out after separating the electrode foil, whereby the electrode is defluorinated.

[0018] Defluorination describes a process in which fluorine atoms are removed from the electrode film, electrode foil, and / or electrode. For example, the fluorine atoms are abstracted. This process is used, for instance, to defluorinate the binder material, such as PTFE. The fluorine atoms can be abstracted from the PTFE using atomic hydrogen.

[0019] Defluorination is carried out, for example, before the electrode is inserted into an energy storage device.

[0020] Defluorination of the electrode film and / or electrode foil and / or electrode can reduce or prevent unwanted chemical reactions within an energy storage device between elements of the electrode film, electrode foil and / or electrode and alkali metals.

[0021] For example, reactions of binder materials such as PTFE when operating an energy storage device with alkali metals such as lithium or sodium lead to defluorination of the PTFE and the formation of metal fluorides. For example, in lithium and sodium-ion batteries, the PTFE reacts irreversibly with Li+ or Na+, rendering these ions unusable for energy storage. 23-3764

[0022] - 4 - can. This leads to a loss of nominal capacity and thus a reduction in the energy of the energy storage device.

[0023] Advantageously, the defluorination of the electrode film and / or the electrode foil and / or the electrode during the manufacture of an electrode or before the electrode is inserted into an energy storage device reduces or avoids irreversible reactions with lithium or sodium during initial charging during the formation of the energy storage device, thus not reducing the nominal capacity of the energy storage device.

[0024] Furthermore, the method, particularly in energy storage devices with a non-metallic negative electrode, such as graphite or graphite / silicon active materials, advantageously allows for savings of positive electrode active material, since this material can be fully utilized for energy storage due to the absence of irreversible reaction with, for example, the binder material. The method according to the invention requires less cathode active material to store the same amount of energy in the energy storage device.

[0025] Furthermore, the process eliminates other disadvantages of irreversible reactions by preventing them from occurring within the energy storage device. For example, this increases the lifespan of the energy storage device.

[0026] According to at least one embodiment, the defluorination of the electrode film and / or the electrode foil and / or the electrode is carried out physically.

[0027] For example, defluorination can be carried out physically by irradiating the electrode film and / or the electrode assembly and / or the electrode. In this process, the PTFE is treated, for example, with high-energy 23-3764

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[0029] irradiated with gamma rays or electron beams to cause bond breaking and defluorination.

[0030] Alternatively or additionally, defluorination can be carried out physically by mechanical grinding or milling. For example, PTFE is milled to break down the polymer structure and promote defluorination.

[0031] Alternatively or additionally, defluorination can be carried out physically through high-temperature treatment. In this process, for example, the PTFE is heated to very high temperatures, such as temperatures above 400 °C, to effect defluorination via thermal degradation.

[0032] By performing the defluorination of the electrode film and / or electrode foil and / or electrode physically, chemical additives can be advantageously avoided, thus eliminating the need for additional chemicals. Furthermore, physical defluorination allows for precise and defined control to achieve the desired material properties.

[0033] According to at least one embodiment, the defluorination of the electrode film and / or the electrode foil and / or the electrode is carried out chemically.

[0034] For example, defluorination can be carried out chemically by alkaline hydrolysis. In this process, PTFE is treated with strongly alkaline solutions such as sodium hydroxide (NaOH) at elevated temperatures to break the fluorocarbon bonds and remove fluorine atoms.

[0035] Alternatively or additionally, defluorination can be carried out chemically by acid hydrolysis. In this process, for example, PTFE is treated with strong acids, such as sulfuric acid (H₂SO₄) or hydrochloric acid (HCl), at elevated temperatures to break the fluorocarbon bonds and remove fluorine atoms. 23-3764

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[0037] Alternatively or additionally, defluorination can be carried out chemically by thermal treatment with reactive gases. For example, PTFE is heated in the presence of reactive gases such as ammonia (NH3) or hydrogen (H2) to initiate defluorination reactions.

[0038] Alternatively or additionally, defluorination can be carried out chemically by plasma treatment. For example, the PTFE can be exposed to a low-pressure plasma generated by reactive gases such as oxygen (O2) or nitrogen (N2) to trigger chemical reactions and defluorination.

[0039] By carrying out the defluorination of the electrode film and / or the electrode foil and / or the electrode chemically, a more advanced or extensive defluorination can be advantageously carried out, since carbon-fluorine bonds (CF bonds) can be specifically targeted.

[0040] According to a second first aspect, the invention relates to an energy storage device, wherein the energy storage device comprises an electrode produced according to the method of the first aspect.

[0041] According to a third aspect, the invention relates to a vehicle comprising an energy storage device according to the second aspect.

[0042] Exemplary embodiments of the invention are explained in more detail below with reference to the schematic drawings. These show:

[0043] Figure 1 Flowchart of a process for manufacturing an electrode of an energy storage device.

[0044] The following describes a method for manufacturing an electrode for an energy storage device. 23-3764

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[0046] According to one embodiment, in the first process step S1 according to Figure 1, the electrode active material is first mixed together with additives and PTFE as a binder to form a powder agglomerate.

[0047] In a second process step S3, the powder mixture is calendered into an electrode film. For example, the powder mixture is compacted by several rotating pairs of rollers.

[0048] In a third process step, S5, the electrode film is then laminated onto a current collector. This process step produces an electrode foil consisting of the electrode film and the current collector foil.

[0049] In process step S7, the electrode foil is separated into several electrodes. For example, several electrodes are cut out of the electrode foil.

[0050] In a further process step S9, defluorination is carried out. For example, one of several electrodes cut from the electrode foil is defluorinated. The defluorination of the electrode is carried out chemically, for example, using plasma treatment. For example, the PTFE binder material of the electrode is exposed to reactive gases such as oxygen or nitrogen during plasma treatment. For example, fluorine atoms react with the oxygen, thereby defluorinating the electrode or releasing the fluorine atoms from the electrode material or the PTFE binder material.

[0051] For example, the electrode produced in this way can subsequently be inserted into an energy storage device, in particular a lithium-ion battery. Premature defluorination prevents an irreversible reaction of the electrode inserted into the energy storage device with alkali metals such as the lithium in the energy storage device during formation or initial operation. Thus, the ions 23-3764 can be advantageously

[0052] - 8 - of the energy storage device for energy storage. Defluorinating the electrode before inserting it into the energy storage device prevents irreversible reaction with the ions of the energy storage device. This advantageously prevents capacity loss within the energy storage device and improves the energy efficiency of the electrode and the energy storage device.

[0053] The exemplary embodiment relates to a process in which the defluorination step is carried out on the isolated electrode. Alternatively or additionally, the defluorination can be carried out after calendering the powder mixture into an electrode film and / or after laminating the electrode film onto a current collector.

Claims

23-3764 - 9 - Patent claims 1. Method for manufacturing an electrode of an energy storage device, the method comprising: - Mixing active material, additives and binder material into a Powder mixture - Calendering the powder mixture into an electrode film, - Laminating the electrode film onto a current collector to form a Electrode foil - Separating the electrode foil to the electrode, whereby - defluorination of the electrode film and / or the electrode foil and / or the The electrode is used.

2. The method of claim 1, wherein the defluorination is carried out by irradiation of the Electrode film and / or electrode assembly and / or electrode.

3. The method of claim 1, wherein the defluorination is carried out by mechanical means. Grinding and / or milling of the electrode film and / or the electrode composite and / or the electrode is performed.

4. The method of claim 1, wherein the defluorination is carried out by a High-temperature treatment of the electrode film and / or the electrode composite and / or the electrode is carried out.

5. Method according to claim 1, wherein the defluorination is carried out by alkaline or acidic hydrolysis of the electrode film and / or the electrode composite and / or the electrode.

6. The method of claim 1, wherein the defluorination is carried out by thermal means Treatment of the electrode film and / or the electrode assembly and / or the electrode with reactive gases is carried out. 23-3764 - 10 - 7. Method according to claim 1, wherein the defluorination is carried out by plasma treatment of the electrode film and / or the electrode assembly and / or the electrode.

8. Energy storage device comprising an electrode manufactured according to the method of any one of claims 1 to 7.

9. Vehicle comprising an energy storage device according to claim 8.

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