Method for producing battery paste and battery

Abstract

The present invention relates to a method for manufacturing a battery slurry, the method comprising dispersing a particulate material in a binder and a solvent to form a battery slurry, where the particulate material is charged prior to dispersion. The invention further relates to a battery.

Description

Technical Field

[0001] The invention relates to a method for producing a battery slurry and a battery having a battery slurry obtained according to this method. Background Art

[0002] A battery has at least two different electrodes, a positive electrode (cathode) and a negative electrode (anode). To produce these electrodes, a battery slurry (also called "slurry") is used, which has at least one active material as well as an electrode binder and a solvent, optionally together with additives such as conductive additives or conductive additives.

[0003] The term "battery" here and below refers not only to primary batteries but also to secondary batteries.

[0004] One of the challenges in producing battery slurries is to ensure that the participating components are distributed as evenly as possible. In order to achieve this, efforts are made in particular to suppress agglomeration of the granular materials contained in the battery slurry as much as possible. Agglomeration ensures that the primary particles of the granular material are packed into larger secondary particles, i.e. agglomerates are formed.

[0005] This effect can be counteracted to a certain extent by using devices for mixing the components of the battery paste. However, the dispersing effect of such devices is limited by the structural conditions, so that these devices have a certain efficiency, which cannot be improved further. It is also desirable to use a dispersing process that is as short as possible in order to reduce the production time and production costs. In addition, the energy input in the dispersing process cannot be increased at will, because it is limited by the binder used.

[0006] Another possibility for increasing the dispersing effect is to add dispersing additives, which change the surface properties of the participating components and ensure a higher wettability, which in turn has a favorable effect on the dispersibility. The disadvantage of this solution is that the dispersing additive remains in the battery slurry, but when the battery with this battery slurry is subsequently used, the dispersing additive appears as an inactive material and thus reduces the energy density of the corresponding battery. In addition, undesirable side reactions with other components of the battery may occur, which limits the formulation freedom and / or reduces the reliability of the battery. Summary of the invention

[0007] The object of the present invention is therefore to provide a method for producing a battery slurry which allows an improved dispersion of the components of the battery slurry. In addition, a more cost-effective and / or more powerful battery is to be provided.

[0008] According to the invention, this object is achieved by a method for producing a battery slurry, wherein in the method a granular material is dispersed in a binder and a solvent to form a battery slurry and the granular material is charged before dispersion.

[0009] The invention is based on the basic idea of ​​influencing the surface tension of the granular material to be used in the battery slurry in a targeted manner in order to increase the wettability of the charged granular material even without the use of dispersing additives or at least with a reduced amount of dispersing additives and to achieve a good distribution of the components of the battery slurry and to counteract agglomeration. It has been recognized that the granular materials commonly used in battery slurries are in many cases electrically conductive and are therefore particularly suitable for charging.

[0010] The effect of increasing wettability of particulate materials due to charging is attributed to the following: the Zeta potential of the particulate material in a mixture with a binder and a solvent increases due to charging. With the increase in Zeta potential, the solvate shell of the dispersed particulate material grows to compensate for its charge. At the same time, the current dispersion is stabilized and the transfer of shear energy is improved, as the charged particles repel each other.

[0011] The method according to the invention thus makes it possible to achieve an improved dispersing effect while maintaining the same duration of the dispersing process or to achieve a shortened duration of the dispersing process while maintaining the same dispersing effect.

[0012] The granular material is preferably charged by means of a spray electrode.

[0013] Here, the term "spray electrode" refers to an ionizer, for example an ionizer that generates charged particles and distributes them to the granular material by means of a fan. Such a spray electrode is available at low cost and is simple to operate.

[0014] In particular, the spray electrode is operated at a power in the range of 700 to 800 Watt per kg of material to be treated, for example at 750 Watt per kg of material to be treated.

[0015] In one variant, the granular material is charged for 3 to 8 minutes, in particular for 4 to 5.5 minutes, for example for 5 minutes. When charging for less than 3 minutes, the charging charge may be too low, so that the wettability of the granular material is not sufficiently improved, while when charging for more than 8 minutes, the effort and duration of charging are excessively increased.

[0016] In order to achieve good distribution of the particulate material in the battery slurry, the particulate material may have an average particle diameter d below 7.0 μm after being dispersed in the battery slurry. 50 .

[0017] The average particle diameter after dispersion is d 50 Describes the particle size of secondary particles of a granular material, ie agglomerates of primary particles of the granular material added to the dispersion process.

[0018] Average particle diameter d 50 It can be determined with the aid of static light scattering in a particle size measuring instrument.

[0019] Preferably, the particulate material is a conductive additive. The conductive additive is already conductive due to its function and is therefore suitable to a particular extent for charging. Furthermore, the conductive additive is already provided in the conventional formulation of the battery slurry, so that no modification of the formulation is necessary.

[0020] Preferably, the conductive additive is carbon black. It is known that although carbon black is commercially available as a nanometer particle with an average particle diameter d 50 However, carbon black can be agglomerated during the dispersion process to form particles with an average particle diameter of about 10 μm. 50 This effect can be counteracted reliably and in a simple manner by the charging according to the invention.

[0021] In order to further optimize the wettability of the granular material, the weight ratio of the conductive additive to the solvent may be in the range of 1:1 to 1:4, in particular in the range of 1:3 to 1:4, for example 1:3.5.

[0022] In one variant, the solvent is water or contains water. Water is a particularly polar solvent, so that electrostatic charging of the granular material can have a particularly strong influence on wettability.

[0023] Water-based battery slurries are particularly suitable for anode battery slurries.

[0024] In one embodiment, the dispersing is performed in a nitrogen atmosphere. This is particularly advantageous if at least one of the components used in the battery slurry is flammable and / or easily ignitable, for example if a flammable solvent is used.

[0025] In order to prevent the charging charge of the granular material from being neutralized again, the dispersion can be carried out in a mixing container that is protected from discharge. Such a mixing container is usually grounded in order to suppress unintentional charging during the dispersion process. It is now known that, instead, a targeted charging charge and the maintenance of this charging charge can have a favorable effect on the dispersion process.

[0026] The object of the present invention is therefore achieved by a battery comprising a battery slurry obtained according to the above method.

[0027] The advantages and features of the method according to the invention apply correspondingly to the battery according to the invention and vice versa, and reference is made to the above explanations.

[0028] The battery is preferably a secondary battery, in particular a lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further features and characteristics of the invention can be gathered from the following examples, which are not to be understood in a limiting sense, and from the drawings. Figure 1 A line graph for particle size distribution is shown. DETAILED DESCRIPTION

[0030] Laboratory testing for making battery slurries

[0031] Example 1: Comparison Example

[0032] In a mixing container (mixer from Thinky Co.) were provided 0.81 g of a binder (water-soluble binder), 7.1 g of water as a solvent, and 0.23 g of carbon black as a granular material and a conductive additive.

[0033] Therefore, the total weight of the mixture was 8 grams, and the weight ratio of the conductive additive to the binder was 1:3.5.

[0034] The mixture was mixed in a mixing container at 2000 rpm for over 30 minutes to form a battery slurry.

[0035] Example 2

[0036] Example 2 was carried out similarly to Example 1, however the carbon black used was pretreated before being added to the mixture.

[0037] For this purpose, the carbon black was treated with an ionizer from the company KERN (type YBI-01) for 5 minutes at an ionizer power of 6 W and thus charged.

[0038] Measurement of particle size distribution

[0039] The particle size distribution of the dispersions or battery slurries obtained according to Examples 1 and 2 was measured by means of static light scattering according to the following protocol.

[0040] In a suitable container, weigh 40 g of solvent (VE water) and then weigh 0.5 g of the dispersion or battery slurry to be characterized. The dispersion is homogenized by stirring and, if necessary, by adding a suspending agent such as methoxypropyl acetate.

[0041] The particle size of the homogenized dispersion was determined by means of static light scattering, using a Horiba LA-950V2 particle analyzer (Retsch Technology).

[0042] The respective measured dispersion is checked for precipitation after the measurement in order to ensure that no precipitation occurred during the measurement.

[0043] The results were confirmed three times.

[0044] The single figure shows the measurement results for Examples 1 and 2, wherein curve 10 describes Example 1 (not according to the invention) and curve 12 describes Example 2 according to the invention.

[0045] As can be seen, the particle size distribution is shifted towards smaller particle sizes by using the charged conductive additive.

[0046] Average particle diameter d in Example 1 (not according to the present invention) 50 is 7.7 μm in Example 2 and 6.73 μm in Example 2. Thus, by charging the carbon black, it can be observed that the average particle diameter d 50 of reduction.

[0047] Furthermore, the distribution in Example 2 is much closer to a trimodal distribution than is the case for Example 1. 50 In addition to the desired reduction of , a defined distribution of particle diameters is ensured.

Claims

1. A method for producing a battery slurry, wherein: In this method, a particulate material is dispersed in a binder and a solvent to form a battery slurry, and the particulate material is charged prior to dispersion.

2. The method according to claim 1, wherein: The granular material is charged by means of a spray electrode.

3. The method according to claim 1 or 2, wherein The granular material is charged for 3 to 8 minutes.

4. A method according to any one of the preceding claims, wherein: The particulate material has an average particle diameter d of less than 7.0 μm after being dispersed in the battery slurry. 50 .

5. A method according to any one of the preceding claims, wherein: The particulate material is a conductive additive.

6. The method according to claim 5, wherein: The weight ratio of the conductive additive to the solvent is in the range of 1:1 to 1:

4.

7. A method according to any one of the preceding claims, wherein: The solvent is water or contains water.

8. A method according to any one of the preceding claims, wherein: The dispersion was performed in a nitrogen atmosphere.

9. A method according to any one of the preceding claims, wherein: The dispersion is performed in a mixing container which is protected from discharge.

10. A battery comprising a battery slurry obtained according to the method according to any one of the preceding claims.

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