DE102018217518A1 - Method of manufacturing an electrode for an accumulator - Google Patents

Abstract

Method for producing an electrode (1) for an accumulator (2), the electrode (1) being an electrode material (3), at least comprising a large number of particles (4) of an active material and a binder material (5) for spatially fixing the particles ( 4) the active material; the electrode material (3) additionally having absorber particles (6); the method comprising at least the following steps: a. Providing the electrode (1) with the electrode material (3) b. Irradiating the electrode material (3) with at least one radiation source (7) for the targeted activation of the absorber particles (6); c. Changing a spatial structure (9) of the electrode material (3) in predetermined areas (10) of the electrode material (3).

Description

The invention relates to a method for producing an electrode, an electrode material for producing an electrode, an electrode produced by the method and an accumulator. The electrode is used in particular in lithium-ion batteries.

In the field of lithium-ion batteries, there are various complex methods for structuring electrodes three-dimensionally. These methods are often complicated to use, expensive, difficult in existing electrode manufacturing processes such as Integrate roll-to-roll processes or inflexible in the application.

The structuring of the electrode can offer advantages, e.g. with regard to the available surface and thus the electrode kinetics, which enables higher charging and discharging rates.

The electrodes are usually structured using pre-structured carrier materials (arresters) such as e.g. Nets or grids, or etched or microstructured structures on their surface. The structuring of the electrode itself can also be carried out using chemical etching or conventional microstructuring methods such as e.g. B. photolithography, epitaxy or laser structuring. Structuring via the use of structured initial particles is also possible, e.g. B. highly porous particles, fibrous or tubular particles or generally about the shape and size of the starting particles. Another solution is to align the particles in a magnetic field and fix the alignment while the electrode is drying.

The disadvantages of the respective processes are specific to the specific process. Microstructuring techniques that use epitaxy or photolithography are often complex and expensive. Depending on the level of detail of the structuring to be generated, laser structuring is likewise expensive and time-consuming or only allows the generation of surface structures, since the penetration depth of laser radiation is limited. The use of chemical etching is highly material-specific and may be incompatible with other components of the electrode mixture or the electrode material. The pre-structuring of the arrester is only a relocation of the process, but has similar problems. The generation of structured starting particles is, depending on the desired modification, complicated and requires additional steps in material synthesis such as. B. etching or sintering, through which the price of the starting materials can be significantly increased. The structuring of the particles themselves or their alignment in the magnetic field has an impact on the performance of the particles and sometimes requires different process steps when manufacturing the electrode (different mix, use of other binder materials, occupation of the particle surface with inactive particles, use of strong magnets).

The methods mentioned are subject to constant improvement in practice. To reduce costs and effort, microstructuring processes are often limited to relatively simple surface structuring. Commercially available particles are usually structured relatively simply in order to reduce costs. Etching processes are specifically adapted to electrode materials in order to achieve the desired effects.

From the CN 104091918 A a method for coating an electrode material is known. The coating is produced by coupling in microwave radiation.

The object of the present invention is to at least partially solve the problems mentioned with reference to the prior art. In particular, a further method for structuring electrode material is to be proposed. The structuring is intended in particular to increase the surface area of an active material within the electrode material, so that in particular higher charging and discharging rates are made possible. In particular, the method should be easy to carry out, flexible and inexpensive and can be used in common process methods such as roll-to-roll.

A method with the features according to claim 1 contributes to solving these problems. Advantageous further developments are the subject of the dependent claims. The features listed individually in the patent claims can be combined with one another in a technologically meaningful manner and can be supplemented by explanatory facts from the description and / or details from the figures, further embodiment variants of the invention being shown.

1. a. Bereitstellen der Elektrode mit dem Elektrodenmaterial;
2. b. Bestrahlen des Elektrodenmaterials mit mindestens einer Strahlungsquelle zur gezielten Aktivierung der Absorberpartikel;
3. c. (zumindest) Verändern einer räumlichen Struktur des Elektrodenmaterials in vorbestimmten Bereichen des Elektrodenmaterials.

Insbesondere ist die Elektrode eine Komposit-Elektrode, wobei das Elektrodenmaterial zumindest aus einem (Kathoden- oder Anoden-)Aktivmaterial (z. B. NCM - also Lithium-Nickel-Cobalt-Mangan-Oxid, LCO - also Lithium-Cobalt-Oxid, NCA - Lithium-Nickel-Cobalt-Aluminium-Oxid, LNMO - Lithium-Nickel-Mangan-Oxid (Hochvoltspinel), LFP - Lithiumeisenphosphat oder andere) und einem Bindermaterial besteht.A method for producing an electrode for an accumulator is proposed. The electrode has an electrode material, at least comprising a large number of particles of an active material and a binder material for spatially fixing the particles of the active material. The electrode material additionally includes absorber particles. The method has at least the following steps:

1. a. Providing the electrode with the electrode material;
2. b. Irradiating the electrode material with at least one radiation source for targeted activation of the absorber particles;
3. c. (at least) changing a spatial structure of the electrode material in predetermined areas of the electrode material.

In particular, the electrode is a composite electrode, the electrode material at least consisting of a (cathode or anode) active material (e.g. NCM - that is lithium-nickel-cobalt-manganese oxide, LCO - that is lithium-cobalt oxide, NCA - lithium-nickel-cobalt-aluminum oxide, LNMO - lithium-nickel-manganese oxide (high-voltage spinel), LFP - lithium iron phosphate or others) and a binder material.

Binder material is especially added to the electrode material in order to improve the cohesion between the particles of the electrode material or the active material itself and between particles and a conductor. In most cases, the electrode can be held together only by the binder material. As binder materials such. B. polymers or polymer compounds are used.

Possible, generally customary binder materials are e.g. B. polyvinylidene difluoride (PvdF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylamide (PAM), polymethyl methacrylate (PMMA), alginates, natural rubber derivatives (xanthan, gellan, guarane) etc. and others organic polymers.

The electrode material additionally includes absorber particles. In particular, the absorber particles are arranged within or at least adjacent to the binder material.

The electrode in particular further comprises an (electrical current) arrester, e.g. B. an electrode sheet on which the electrode material is arranged and, if necessary, additionally an electronic guide additive in the electrode material, for. B. conductive carbon black, graphene, carbon nanotubes, carbon nanorods and others. The key additive can in particular be at least partially replaced by the absorber particles.

In particular, a microwave radiator is used as the radiation source, which emits microwave radiation. It is also possible to use different radiation sources together or to use another radiation source (e.g. infrared radiator). In particular, only one type of radiation source is used.

With the use of radiation, in particular microwave radiation, the structure of the binder material present in the electrode material can in particular be destroyed at certain points. In particular, this is done by activating the absorber particles (e.g. heating the absorber particles or by activating absorber particles designed as radical formers), with the binder material decomposing after activation.

It is therefore proposed in particular not to directly stimulate the decomposition of the binder material, but e.g. B. by absorption of the radiation on other materials, namely the absorber particles (e.g. carbon), e.g. B. to generate local hotspots that lead to thermal decomposition of the binder material.

By using radiation, in particular infrared radiation or microwave radiation, the binder material can be decomposed in a targeted manner by activating absorber particles, as a result of which it loses its binding effect and the cohesion of the electrode material is dissolved.

The activation of the absorber particles or the decomposition of the binder material can also take place via the formation of interference by the radiation. For this purpose, at least two radiation sources are used, the radiation of which is oriented to form interference.

In particular, it is possible to position the intensity maxima in the interior of the electrode material via an angular relationship and wavelength modulation of the type of radiation used. The energy of the radiation and the respective maxima can be set in such a way that an intensity necessary for the decomposition of the binder material occurs only at the interference maxima of the radiation. By positioning the intensity maxima, a structure can be created within the electrode material.

The material of the electrode material which is influenced in its adhesion (in particular the decomposed binder material and possibly the absorber particles) can then be physically removed from the electrode material.

Irradiation of the radiation is, apart from the desired effect, a non-invasive and non-contact technique, which is a simple radiation z. B. allows a tape roll. The band only has to be placed under a radiation source and / or through the focus or interference plane, e.g. B. two specifically arranged radiation sources. The removal of the excess material following the decomposition of the binder material can e.g. B. by blowing compressed air or shaking.

In particular, it is possible to introduce other materials into the electrode material in order to achieve structuring effects in response to the radiation, e.g. B. by substances that release gases when irradiated.

The use of radiation, in particular infrared or microwave radiation, can be specifically adapted to the absorber particles used, so that energy is essentially only introduced into the absorber particles. Thermal stresses on the electrode or the other components or areas of the electrode are in particular avoided.

Through the distribution and targeted irradiation of absorber particles in a specific area of the electrode material, a decomposition effect can be limited, in particular locally.

By means of absorber particles distributed in a targeted manner in the electrode material, the radiation, in particular microwave radiation, can be used to selectively heat the electrode around the absorber particles and to decompose the binder material locally and thus with limited space. The wavelength or frequency of the radiation can be adjusted to the resonance frequency of the absorber particles in order to minimize an influence on the other electrode components. It is also possible to introduce radical-forming absorber particles which, after excitation, bring about a chemical decomposition of the binder material without the development of heat.

The material affected in its adhesion can then be physically removed from the electrode. The structure of the electrode can be controlled via the distribution of the absorber particles and in particular via the positioning of the interference maxima in the electrode.

The frequency or wavelength of the radiation can be modulated in a small range around the resonance frequency of the absorber particles in order, for. B. to control the depth of penetration into the electrode material. If the frequency of the radiation corresponds exactly to the resonance frequency, no deep penetration is achieved due to the high absorption, the frequency deviates slightly, the absorption is lower and the penetration depth is higher. The lower absorption can be compensated for by higher radiation intensity. Furthermore, the penetration depth can be controlled via a distribution of the absorber particles in the electrode material.

The coupling of the thermal energy in particular requires heating of the absorber particles, which essentially consist of metals or substances with high electrical permittivity. Materials with high electrical permittivity are typically metal and transition metal oxides such as barium titanate, strontium titanate, titanium dioxide, hafnium dioxide, lanthanum oxide, tantalum oxide, yttrium oxide, zirconium dioxide (also yttrium stabilized), aluminum oxide, calcium copper titanate (CCTO with perovskite structure) and many others. So-called radical starters can also be used as absorber particles which break down into radicals when activated and thus decompose the binder, e.g. Azoisobutyronitrile (AIBN), dibenzene peroxide (DBPO), other azo compounds, organic and inorganic peroxides (e.g. peroxodisulfates) and many more.

In the case of metal particles as absorber particles, these can additionally serve as a conductive additive in the electrode material and partially replace the carbon (conductive carbon black) usually used for this.

In particular, the additional admixing of further components into the electrode material in order to achieve a structuring is not desirable, since it requires additional effort and active material of the electrode material of the electrode is replaced. This reduces the energy density of the electrode. The absorber particles can therefore, for. B. at least partially formed by an already existing structural component (the soot) of the electrode.

The binder material is in particular the most thermally unstable component of the electrode or the electrode material and is therefore primarily decomposed by thermal stress as soon as temperature maxima form in the electrode or in the electrode material.

The proposed method enables, in particular, inexpensive and non-invasive structuring of electrodes and is completely compatible with the existing electrode manufacturing and processing methods. The structuring can e.g. B. in the roll-to-roll process and only requires the introduction of the existing electrode in a radiation field of one or more radiation sources. In particular, no changes to the composition or components of the electrode may be necessary, since only existing components (binder material and conductive carbon black) of the electrode material may be used for the structuring.

At least one microwave radiator is preferably used as the radiation source, which emits microwave radiation, by means of which the absorber particles are heated or excited.

In particular, the microwave radiation has a frequency in the range from 300 MHz [MegaHertz] to 300 GHz [GigaHertz]. In particular, the wavelength of the radiation is between 1 mm [millimeters] and 1,000 mm.

In particular, infrared radiation can additionally or alternatively be used. In particular, the infrared radiation has a wavelength in the range from 0.8 µm [micrometer] to 1,000 µm.

Radiation, in particular infrared radiation and microwave radiation, denotes electromagnetic waves with the specified wavelengths and / or frequencies.

In particular, the absorber particles at least partially comprise metal oxides or transition metal oxides, which are activated as a result of the radiation and thus heated.

As an alternative or in addition, the absorber particles can at least partially comprise free-radical formers, which are activated by heating or photochemical excitation as a result of the radiation and, in the activated state, at least partially (chemically) decompose an adjacent binder material (e.g. a polymer).

The wavelength or frequency of the radiation used can also be adapted to the absorption maxima of the absorber material used in the electrode material.

Furthermore, the wavelength or frequency of the radiation used is particularly dependent on the desired structure.

The binder material is decomposed in particular thermally (by forming hotspots) or chemically (by activating the radical formers). If the intensity of the radiation is sufficiently high, the bond breaks, e.g. B. of polymers used as binder material, and for decomposing the binder material. The binder material is either completely decomposed or a polymer structure is dissolved. In both cases, it loses its binding properties and allows physical material to be subsequently removed.

In particular, structuring can also be achieved by generating an interference pattern in the electrode material through the use of at least two discrete radiation sources via angular relationships and possibly (slight) wavelength modification. The intensity required to decompose the binder material occurs in particular (only) at the interference maxima of the radiation and can thus be distributed three-dimensionally in the electrode material.

In particular, there is the possibility of using interference phenomena from microwaves in order to generate local intensity maxima of the microwave radiation within the electrode material. The radiation can then be coupled in via other components of the electrode that are not specifically used as absorber materials and lead to local hotspots.

Additional radiation sources can be used to produce more complex interference patterns.

The introduction of specific absorber particles enables in particular the establishment of an uncomplicated radiation process. The wavelength of the radiation can be adjusted to the absorber particles. In particular, it is not necessary to vary the material of the absorber particles themselves. The selection of the absorber particles or the material used for this essentially depends on the chemical environment in the electrode material or in the electrode and / or on the stability of the material in this environment. However, the chemical environment in most surge arresters and electrode materials is very similar, so that the same absorber particles can be used in many different electrode systems.

In the case of metals as absorber particles, the supposed disadvantage of an additionally necessary electrode component can in particular be compensated for by the fact that the metal can partially replace the typical conductive additive (carbon) in the electrode material.

When using radical formers as absorber particles, particular attention should be paid to the fact that the radicals formed can also attack non-specific other components of the electrode or the electrode material in addition to the binder material. In addition, the radical formers should be activated in particular while the electrode material is in the wet state in order to be effective.

In particular, the radical formers are activated with radiation in the visible (frequency) range, but this is also strongly absorbed by other components (carbon, active material) of the electrode material.

The structured electrode material shows in particular an improved penetration through an electrolyte and thus an optimized mass transport. In particular, higher charging and discharging currents and thus a higher output of an accumulator in which the electrode is used can be achieved.

In particular, changing the spatial structure comprises at least partially decomposing the binder material in predetermined areas of the electrode material.

In particular, after step c. in a further step d. the at least partially decomposed binder material is removed from the electrode or from the electrode material.

The removal is preferably carried out by blowing off (for example by compressed air) or by shaking (ie moving or shaking the electrode so that the decomposed binder material falls out of the electrode material). Other separation processes such as centrifugal spinning, suction or the like are also possible.

In particular, changing the spatial structure comprises at least partially converting a component of the electrode material into a gaseous state, at least this converted and now gaseous component being removed from the electrode material.

In particular, the spatial structure is changed in an inner region of the electrode material, that is to say at a distance from a surface of the electrode material.

Changing the spatial structure preferably includes the formation of at least one cavity (in particular a plurality of cavities) within the electrode material, or at least one depression (in particular a plurality of depressions in the form of a structure) on the surface of the electrode.

The at least one created cavity or depression can be used to intercept or compensate for changes in volume of the electrode material, in particular during the operation of a rechargeable battery (ie when charging or discharging). In particular, the generation of voltages in the electrode material can be reduced or prevented.

In particular, a wavelength or frequency of the radiation is selected and used taking into account an absorption maximum of the absorption particles.

In particular, the wavelength or the frequency can thus be set precisely to the respective absorption maximum of the absorption particles, so that the radiation energy is coupled into the absorption particles to a maximum.

According to another embodiment, the wavelength or frequency cannot be adjusted to the respective absorption maximum of the absorption particles, so that coupling of the radiation energy into the absorption particles is reduced and also lower-lying absorption particles (i.e. further away from the surface of the electrode material) due to the absorption particles Radiation can be reached and excited.

In particular, a wavelength of the radiation is selected and used taking into account an absorption maximum of a different material of the electrode than the absorption particle, so that an at least partial decomposition of the binder material takes place due to heat conduction from the other material (e.g. conductive additives). In particular, other materials, e.g. B. carbon-containing structures, the structure of which is not changed. The heating of the other material can then (also) be used to decompose the binder material.

Furthermore, an electrode material for producing an electrode using the described method is proposed, the electrode material having at least a large number of particles of an active material and a binder material for spatially fixing the particles of the active material. The electrode material also has absorber particles.

An electrode for a rechargeable battery is also proposed, produced using the described method. In particular, the electrode has at least one cavity within an electrode material or a depression on the surface of the electrode.

An accumulator is proposed, at least having an anode and a cathode and an electrolyte, at least one anode and cathode being the electrode described, the at least one cavity being at least filled with the electrolyte.

The electrolyte is in particular lithium ion conductive.

The structuring of the electrodes and the electrodes or accumulators produced in this way can be used in particular in all current and future fields of application of the lithium-ion accumulators. These include e.g. B. consumer electronics and microelectronic applications as well as stationary or mobile energy storage and automotive applications.

The statements regarding the method apply equally to the electrode material, the electrode and the accumulator and vice versa.

As a precaution, it should be noted that the numerals used here ("first", "second", ...) serve primarily (only) to differentiate between several similar objects, sizes or processes, in particular no dependency and / or sequence of these objects, sizes or mandate processes to each other. If a dependency and / or sequence is required, this is explicitly stated here or it is evident for the person skilled in the art to study the specifically described configuration.

• 1: einen Akkumulator;
• 2: eine Elektrode vor der Strukturierung;
• 3: eine Elektrode nach der Strukturierung; und
• 4: eine Elektrode während der Strukturierung gemäß den Schritten b. und c. des Verfahrens.

The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be pointed out that the invention is not intended to be limited by the exemplary embodiments mentioned. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description. In particular, it should be pointed out that the figures and in particular the proportions shown are only schematic. Show it:

• 1 : an accumulator;
• 2nd : an electrode before structuring;
• 3rd : an electrode after structuring; and
• 4th : an electrode during the structuring according to steps b. and c. of the procedure.

1 shows an accumulator 2nd comprising an anode 14 and a cathode 15 that have a separator 18th are arranged separately from each other. The electrodes 1 each have an arrester 17th and on the arrester 17th Electrode material 3rd on.

2nd shows an electrode 1 before structuring. 3rd shows an electrode 1 after structuring. 4th shows an electrode 1 during structuring according to steps b. and c. of the procedure. The 2nd to 4th are described together below.

The electrode 1 comprises an electrode material 3rd that on a surge arrester 17th the electrode 1 is arranged. The electrode material 3rd includes a variety of particles 4th an active material and a binder material 5 that the spatial fixation of the particles 4th serves. The electrode material further comprises 3rd Key addenda 19th , through which an electronic conductivity of the electrode 1 is improved. An electrolyte 16 is in the electrode material 3rd , comprising the particles 4th , the binder material 5 and the key additions 19th , arranged to transport the lithium ions 20th along the diffusion paths 21 through the electrode material 3rd .

In 3rd is the spatial structure 9 of the electrode material 3rd in certain areas 10th of the electrode material 3rd noticeably changed. There are cavities 12th or flaws in the structure 9 of the binder material 5 before that now from the electrolyte 16 are filled out. This is the transport of the lithium ions 20th inside the electrode material 3rd and along the diffusion paths 21 easier possible.

In 4th is shown that starting from an activation of absorber particles 6 that are in or on the binder material 5 are arranged, a change in structure 9 can be done. Here is the radiation 8th over the surface 11 of the electrode material 3rd into the electrode material 3rd and the absorber particles arranged therein 3rd and / or the other material 14 (e.g. binder material 5 ) coupled. By creating hotspots or by activating radical formers 8th (as a result of the activation of the absorber particles 6 ) in certain areas 10th , also spaced from the surface 12th of the electrode material 3rd , can binder material 5 from the electrode material 3rd decomposed and then removed.

When changing the structure 9 (the structuring) of the electrode material 3rd there is a local decomposition of the binder material 5 . As a result, the particles lose 4th of the active material internal cohesion and adhesion in these areas 10th and can then be physically removed. The loss of material occurs only in certain areas 10th the structure 9 of the electrode material 3rd on so that a change in structure 9 in these areas 10th is made possible. The changed structure 9 enables better penetration of the electrode material 3rd through the electrolyte 16 and improved diffusion of the lithium ions 20th : The structure can also offer buffer zones for a volume expansion of the electrode materials.

Reference list

1

electrode

2nd

accumulator

3rd

Electrode material

4th

particle

5

Binder material

6

Absorber particles

7

Radiation source

8th

radiation

9

structure

10th

Area

11

surface

12th

cavity

13

material

14

anode

15

cathode

16

electrolyte

17th

Arrester

18th

separator

19th

Key addition

20th

Lithium ion

21

Diffusion path

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• CN 104091918 A [0007]

Claims (14)

Method for producing an electrode (1) for an accumulator (2), the electrode (1) being an electrode material (3), at least comprising a large number of particles (4) of an active material and a binder material (5) for spatially fixing the particles ( 4) the active material; the electrode material (3) additionally having absorber particles (6); the method comprising at least the following steps: a. Providing the electrode (1) with the electrode material (3); b. Irradiating the electrode material (3) with at least one radiation source (7) for the targeted activation of the absorber particles (6); c. Changing a spatial structure (9) of the electrode material (3) in predetermined areas (10) of the electrode material (3). Procedure according to Claim 1 , At least one microwave radiator being used as the radiation source (7), which emits microwave radiation (8) through which the absorber particles (6) are heated. Procedure according to Claim 2 , wherein the microwave radiation (8) has a frequency in the range from 300 MHz to 300 GHz. Method according to one of the preceding claims, wherein the absorber particles (6) at least partially comprise metal oxides or transition metal oxides which are activated as a result of the radiation and thus heated. Method according to one of the preceding claims, wherein the absorber particles (6) at least partially comprise free-radical formers which are activated by heating or photochemical excitation as a result of the radiation and in the activated state at least partially decompose an adjacent binder material (5). Method according to one of the preceding claims, wherein changing the spatial structure (9) comprises at least partially decomposing the binder material (5) in predetermined areas (10) of the electrode material (3). Procedure according to Claim 6 , after step c. in a further step d. the at least partially decomposed binder material (5) is removed from the electrode (1). Procedure according to Claim 7 , the removal being carried out by blowing off or by shaking off. Method according to one of the preceding claims, wherein the spatial structure (9) is changed in an inner region (10) of the electrode material (3), ie at a distance from a surface (11) of the electrode material (3). Method according to one of the preceding claims, wherein the change in the spatial structure (9) comprises the formation of at least one cavity (12) within the electrode material (3). Method according to one of the preceding claims, wherein a wavelength of the radiation (8) is selected and used taking into account an absorption maximum of the absorber particles (6). Electrode material (3) for producing an electrode (1) with a method according to one of the preceding claims, wherein the electrode material (3) at least a plurality of particles (4) of an active material and a binder material (5) for spatially fixing the particles (4) of the active material; the electrode material (3) additionally having absorber particles (6). Electrode (1) for an accumulator (2), produced with a method according to one of the preceding Claims 1 to 11 The electrode (1) has at least one cavity (12) within an electrode material (3) of the electrode (1). Accumulator (2), at least having an anode (14) and a cathode (15) and an electrolyte (16), at least one anode (14) and cathode (15) following an electrode (1) Claim 13 , the at least one cavity (12) being filled at least with the electrolyte (16).

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