DE102018200977A1 - Process for producing an electrode material - Google Patents

Abstract

The invention relates to a method for producing an electrode material (1) comprising the following steps: a. Providing a mixture (3) consisting of a binder (5) and a solvent (7), b. Presenting and moving a powdered active material (9), which preferably contains lithium, in a mixing device (11), c. Adding the mixture (3) into the mixing device (11), wherein the powdered active material (9) is coated with the binder (5), so that coated particles (13) arise andd. if appropriate, at least partial removal of the solvent (7) from the coated particles (13) so that particles of the electrode material (1) are formed. Furthermore, the invention relates to a battery and a use of the battery.

Description

The invention relates to a method for producing an electrode material comprising providing a mixture, presenting and moving a powdery active material in a mixing device and adding the mixture. Furthermore, the invention relates to a battery comprising the electrode material and a use of such a battery.

State of the art

Among other things, lithium-ion batteries are characterized by a very high specific energy and extremely low self-discharge. Lithium-ion batteries have at least one positive and at least one negative electrode (cathode or anode), with lithium ions migrating from one electrode to the other during the charging and discharging of the battery. For the transport of lithium ions, a so-called lithium-ion conductor is necessary. As a lithium-ion conductor, a liquid electrolyte or a solid electrolyte can be used.

The lithium-ion batteries may be enclosed in a package. For example, aluminum composite films are used as packaging. So packaged batteries are referred to as a pouch or soft pack because of their soft packaging. In addition to the softpack packaging designs, solid metal housings are also used as packaging, for example in the form of deep-drawn or pressed housing parts. In this case we speak of a solid housing or hardcase.

A lithium-ion battery includes the electrodes, the lithium-ion conductor and current conductors that make the electrical connections. The current conductors can also be called current collectors and are often designed as copper foils or as aluminum foils.

The electrodes are often produced based on solutions or dispersions, so-called slurries. The slurries are applied by means of a coating process to the respective current conductor, which is usually designed as a metal foil, and dried in a subsequent drying process. The solvents or dispersion liquids used are removed by heat supply or pressure reduction in a vacuum process from the applied slurries, whereby the porosity of the electrodes is adjusted.

The slurries can be prepared in different mixers and / or agitators starting from powdery starting materials of different particle size. These methods are very time consuming depending on the powdery materials. Twin-screw extruders can be used to mix the powdery starting materials, which offer a reduction in the mixing time.

The powdery raw materials include active materials such as lithium-nickel-manganese-cobalt-oxide (NCM) for producing a cathode, and besides the active material, there may be contained various conductive additives such as graphite and carbon black, and also binders which may also be referred to as binders.

For the preparation of a cathode material, depending on the binder used, solvents are used which are hazardous to health.

Mixing methods for the production of electrode materials aim for an optimum distribution of particles consisting of binder, so that in the subsequent coating and pressing, in particular calendering, the electrode material on both the current collector and particles of the electrode material to each other by the influence of pressure and heat be bound to an electrode layer.

Accordingly, the quality of the mixing process has a direct influence on the mechanical and electrochemical properties of the electrodes produced.

In addition to the slurry process, so-called dry-coating processes are also used in which no solution and dispersing liquids are used. Here, the powdery starting materials are dry-mixed and then processed in a rolling / rolling process for a freestanding film. This is laminated to the current conductors, which are usually designed as a metallic foil.

US 2015/0303481 A1 relates to a dry-coating process and is directed to an energy storage device wherein the cathode and / or anode is constructed of a polytetrafluoroethylene (PTFE) composite binder and contains polyvinylidene fluoride (PVDF), a PVDF copolymer and / or polyethylene oxide (PEO) , For deagglomerating and mixing polymer particles, a jet mill is used.

US 2013/0295451 A1 describes a solid-state battery electrode formed of a lithium-ion conductor, an active material, and a solid electrolyte, wherein a particle comprises a plurality of lithium-ion conductors and a plurality of Contains active materials. Further, a method for producing the particles is disclosed, which comprises a mixing step of the particles with a solid electrolyte.

US 2007/0003836 A1 relates to composite particles for electrodes, wherein in a granulation step, a conductive additive and a binder are brought into close contact with particles which consist of an electrode active material.

Disclosure of the invention

1. a. Bereitstellen einer Mischung, die aus einem Bindemittel und einem Lösungsmittel besteht,
2. b. Vorlegen und Bewegen eines pulverförmigen Aktivmaterials, das bevorzugt Lithium enthält, in einer Mischvorrichtung,
3. c. Zugeben der Mischung in die Mischvorrichtung, wobei das pulverförmige Aktivmaterial mit dem Bindemittel beschichtet wird, so dass beschichtete Partikel entstehen und
4. d. ggfs. zumindest teilweises Entfernen des Lösungsmittels aus den beschichteten Partikeln, so dass Partikel des Elektrodenmaterials entstehen.

A method for producing an electrode material is proposed, comprising the following steps:

1. a. Providing a mixture consisting of a binder and a solvent,
2. b. Presenting and moving a powdery active material, which preferably contains lithium, in a mixing device,
3. c. Adding the mixture in the mixing device, wherein the powdered active material is coated with the binder, so that coated particles are formed and
4. d. if necessary, at least partial removal of the solvent from the coated particles, so that particles of the electrode material are formed.

First, a mixture, which may be a solution and / or a dispersion, is prepared from the binder and the solvent. In the mixing device, the powdery active material, which is present in dry form, preferably having a moisture content of less than 100 ppm, in particular having a moisture content of less than 20 ppm, is introduced and moved, in particular mixed. The active material includes, for example, lithium nickel manganese cobalt oxides (NCM), lithium nickel cobalt aluminum oxides (NCA), lithium manganese oxide (LMO), lithium iron phosphates (LFP), lithium cobalt ( III) oxide (LCO), lithium titanate (LTO), silicon and / or graphite. The active material preferably consists of NCM 111 ,

The powdered active material, which is located in the mixing device, the mixture is added, in particular by spraying, wherein at least the binder contained in the mixture lays on the surface of the powdered active material and this at least partially covers, which may also be referred to as coating. The coated particles thus formed preferably have a thin layer of binder. The binder layer thickness is preferably between 1 nm and 1000 nm, more preferably between 1 nm and 100 nm.

Preferably, the solvent is at least partially removed in the mixing device from the coated particles. The removal can be achieved by a gas flow or the application of negative pressure. Preferably, during the addition of the mixture in step c), there is a pressure of less than one bar in the mixing device.

Furthermore, the solvent is preferably at least partially removed from the mixture and / or from the coated particles when the mixture is added, in particular by evaporation in a gas stream. By the immediate removal of the solvent before or during contact with the powdery active material and solvents can be used, which usually show negative interactions with the powdered active material. In contrast to a slurry process, wherein the active material is in the solvent, there is only a short contact time between the powdered active material and the solvent, which is present in particular in the form of mist according to the inventive method.

Alternatively, the coated particles can be removed from the mixing device and then the solvent is at least partially removed from the coated particles, so that particles of the electrode material are formed.

The solvent is preferably an organic solvent. The solvent preferably comprises acetone, N-methyl-2-polydone (NMP), acetonitrile, ethanol, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), tetrahydrofuran (THF). or mixtures thereof and optionally lithium salt such as LiPF ₆ , LiTFSI and / or LiClO ₄ .

The solvent particularly preferably has the composition of a battery electrolyte. For example, the solvent contains 1 mol / L LiPF ₆ in a liquid containing 30% by volume of EC and 70% by volume of EMC. If the electrolyte used in the battery to be produced is already used as a solvent in the production of the electrode material, removal of the solvent may be at least partially dispensed with, or only small amounts of the solvent need to be removed.

In the case where the solvent does not contain all the constituents of the later battery electrolyte, further constituents of the electrolyte (eg conductive salt, conductive polymer or liquid electrolyte) may be added in the subsequent preparation of the electrode. Is working with liquid electrolyte, can also in the electrolyte filling the Battery can be achieved through the addition of other electrolyte components optimum electrolyte content.

Furthermore, the particles of the electrode material and / or the coated particles can be agglomerated, preferably in the mixing device or in a subsequent agglomeration step. The agglomeration of the particles of the electrode material and / or the coated particles can be carried out in a subsequent process step by fluidized bed spray agglomeration, fluidized bed spray granulation or high shear granulation. In this case, agglomerates are formed from individual particles of the electrode material and / or individual coated particles, which are better suited for conveying in further process steps and for handling in further process steps.

The mixing device may comprise a stirrer. In the event that the mixing device comprises a stirrer, depending on the shear entry, the shape of the binder can be adjusted. For example, PTFE shows under shear the formation of thin fibrils, which serve to strengthen the composite material of the electrode material.

Preferably, the powdered active material is present in the mixing device in the form of a fluidized bed, in particular while the mixture is being sprayed. Accordingly, the mixing device is preferably a fluidized bed apparatus. Under a fluidized bed, which is also called fluidized bed, a bed of solid particles is understood, which is caused by an upward flow of a fluid in a fluidized state, the bed has fluid-like properties. As fluids such as inert gases, such as. As nitrogen, argon and mixtures thereof, preferably dry gases such as nitrogen and argon having a purity of more than 99.99% in question. By using a fluidized bed, a particularly good mixing of the powdered active material is achieved because individual particles of the powdery active material are present in the fluid and are available for coating with the binder.

The binder may comprise a mixture of substances, preferably the binder comprises a first, solvent-soluble substance and / or a second, solvent-insoluble substance. The first substance and / or the second substance may show fibrillation.

The binder preferably contains a polymer, in particular polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly (vinyl) idenefluoride-co-hexafluoropropylene (PVDF-HFP), a PVDF copolymer, polymethylmethylacrylate (PMMA), polystyrene-butadiene-styrene (SPS), Carboxylmethylcelluloses (CMC) and / or polytetrafluoroethylene (PTFE). More preferably, the binder contains more than 90% by weight of polymer. Particularly preferably, the binder does not contain a conductive additive and the mixture particularly preferably contains no conductive additive.

The mixture preferably contains 1% by weight to 20% by weight of binder, in particular 2% by weight to 18% by weight of PEO. For example, the mixture consists of 8 g of PEO and 100 g of acetone.

Preferably, an electrical and / or an ionic conductive additive is added to the powdered active material, the coated particles and / or the particles of the electrode material, wherein particularly preferably the addition of the electrical and / or the ionic conductive additive is carried out separately from adding the mixture containing the binder.

The active material may, in particular before step c), be in a form coated with an electrical conductive additive.

The separate addition of the electrical and / or the ionic Leitadditives, separate from the mixture, it is avoided that the viscosity of the mixture by the addition of, for example, an ionic Leitadditivs increases dramatically, which would complicate the further processing in terms of flowability, reproducibility and efficiency , The ionic conductive additive is very soluble in polymers with donor properties, such as. B. PEO, so that a homogenization in the last step of the processing is possible. Similarly, the addition of an electrical conduction additive would also affect the viscosity of the mixture. In addition, it is to be foreseen from the addition of the electrical conductive additive in the gas stream, since due to the lower density of the electrical Leitadditives there is a risk that the partially nanoparticulate particles present are discharged through the gas stream.

By the targeted coating of the powdery active material with the binder, the order of addition of various components and also the addition of the conductive additives can be varied more freely, independently of the interactions of the added substances in conventional mixing processes.

The various components and / or the electrical and / or the ionic conductive additive can form a bond with the coated particles. Further, by the selected time of addition of the components and / or the electrical or ionic Leitadditives the Degree of homogenization of the electrode material and / or the degree of coating of the coated particles can be adjusted.

At least two mixing devices, preferably connected in series, can be used, so that in addition to a batch process, a quasi-continuous process is also possible.

Furthermore, a battery is proposed which comprises the electrode material produced according to the invention. The electrode material produced according to the invention can also be used in PEM fuel cells and in supercapacitors, which are also referred to as super caps.

A battery according to the invention advantageously finds use in an electric vehicle (EV), in a hybrid vehicle (HEV), in a plugged-in hybrid vehicle (PHEV) or in a consumer electronics product. Consumer electronics products are in particular mobile phones, tablet PCs or notebooks.

In the context of this description, the term battery or battery cell is used as is customary in the vernacular, that is to say the term battery encompasses both a primary battery and a secondary battery (accumulator).

Advantages of the invention

With the method according to the invention, the amount of solvent can be reduced and hazardous solvent can be completely avoided.

In the production of electrode films can be dispensed with according to the inventive method, the complex drying step and also films can be made with a greater thickness.

In addition, the solvent can be recovered directly from a fluidized bed and the energy requirement can be reduced by reducing furnace distances to evaporate the solvent from the finished electrode.

Furthermore, the binder in the produced electrode material is distributed more homogeneously, whereby the required amount of binder, which is at least needed for the production of electrode films, can be reduced. A reduction in the amount of binder allows an increase in the proportion of active material in the electrode, so that an increased energy density in the battery can be achieved. A lower proportion of binder can also improve the electrical conductivity of the electrode and thereby the performance of the electrode.

With the method according to the invention, the binder can be applied specifically to particles of the active material, while, for example, in the slurry method, the binder is distributed in the electrode material. By targeted coating of the particles new material compositions of the electrodes can be realized.

It can be omitted further mixing steps, so that the number of conveying steps and mixing units can be reduced in the manufacturing process. Furthermore, the mixing time is greatly reduced.

The process according to the invention can replace known slurry processes or dry production processes.

list of figures

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below.

• 1 eine schematische Darstellung einer Ausführungsform des erfindungsgemäßen Verfahrens und
• 2 eine schematische Darstellung einer Beschichtung von Aktivmaterial.

Show it:

• 1 a schematic representation of an embodiment of the method according to the invention and
• 2 a schematic representation of a coating of active material.

1 shows a method according to the invention for producing an electrode material 1 ,

In a mixing device 11 in which a powdered active material 9 was submitted, is a fluidized bed 15 established. A gas stream 17 flows through the powdery active material 9 in the mixing device 11 from the bottom up.

Further, a mixture 3 made from a binder 5 and a solvent 7 exists in the fluidized bed 15 the mixing device 11 sprayed. The powdered active material 9 is with the binder 5 coated so that coated particles 13 arise. The coated particles 13 contained in the illustrated embodiment in addition to the binder 5 also the solvent 7 ,

By the gas flow 17 becomes the solvent 7 at least partially from the coated particles 13 removed, leaving particles of the electrode material 1 arise.

2 schematically shows the coating of a powdered active material 9 with a binder 5 , The powdered active material 9 is with drops of a mixture 3 made from the binder 5 and the solvent 7 is contacted, taking the mixture 3 on the surface of the powdery active material 9 attaches and the powdered active material 9 partially or completely coated, so that a coated particle 13 arises.

From the coated particle 13 becomes the solvent 7 at least partially removed so that particles of an electrode material 1 are formed, wherein on the surface of the powdery active material 9 the binder 5 has attached and the powdered active material 9 coated.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• US 2015/0303481 A1 [0012]
• US 2013/0295451 A1 [0013]
• US 2007/0003836 A1 [0014]

Claims (12)

Method for producing an electrode material (1) comprising the following steps: a. Providing a mixture (3) consisting of a binder (5) and a solvent (7), b. Presenting and moving a powdered active material (9), which preferably contains lithium, in a mixing device (11), c. Adding the mixture (3) in the mixing device (11), wherein the powdered active material (9) is coated with the binder (5), so that coated particles (13) arise and d. if appropriate, at least partial removal of the solvent (7) from the coated particles (13), so that particles of the electrode material (1) are formed. Method according to Claim 1 , characterized in that the solvent (7) is at least partially removed from the coated particles (13) in the mixing device (11). Method according to Claim 2 , characterized in that the solvent (7) by means of a gas stream (17) is removed. Method according to one of the preceding claims, characterized in that the powdered active material (9) in the mixing device (11) in the form of a fluidized bed (15) is present. Method according to one of the preceding claims, characterized in that the active material (9), in particular before step c), is present in a form coated with an electrical conductive additive. Method according to one of the preceding claims, characterized in that during the addition of the mixture (3) in step c), a pressure of less than 1 bar in the mixing device (11) prevails. Method according to one of the preceding claims, characterized in that the coated particles (13) and / or the particles of the electrode material (1) are agglomerated. Method according to one of the preceding claims, characterized in that the binder (5) is a polymer, in particular polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly (vinyl) idenefluoride-co-hexafluoropropylene (PVDF-HFP), a PVDF copolymer, polymethylmethylacrylate ( PMMA), polystyrene-butadiene-styrene (SPS), carboxymethylcelluloses (CMC) and / or polytetrafluoroethylene (PTFE). Method according to one of the preceding claims, characterized in that the solvent (7) acetone, N-methyl-2-pyrrolidone (NMP), acetonitrile, ethanol, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate ( DMC), ethyl methyl carbonate (EMC), tetrahydrofuran (THF) or mixtures thereof and optionally lithium salt such as LiPF ₆ , LiTFSI and / or LiClO ₄ . Method according to one of the preceding claims, characterized in that the powdery active material (9), the coated particles (13) and / or the particles of the electrode material (1) an electrical and / or an ionic conductive additive such as electrolyte salt is added. A battery comprising an electrode material (1) produced by a method according to one of Claims 1 to 10 , Using a battery after Claim 11 in an electric vehicle (EV), in a hybrid vehicle (HEV), in a plug-in hybrid vehicle (PHEV) or in a consumer electronics product.

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