Method and apparatus for applying magnetic fields on an object.

[0001] The invention concerns a method for applying magnetic fields on an object, wherein the application of the magnetic fields in particular takes place continuously and in particular to a graphite coating, and more particularly for producing an article in the form of a negative electrode with vertically oriented graphite particles, for example of quick-loading lithium-ion batteries. It concerns a further with the invented method produced negative electrode nwith vertically oriented graphite particles.

[0002] Carbon-based materials, in particular crystalline graphite as active material in the negative battery electrode application find. Graphite has a layer-like structure consisting of individual carbon layers between the lithium ion, for example in a lithium-ion battery, intercalated during charging. The layer structure of the graphite in flake form reflected by its occurrence.

In the use of flake-like graphite as active material in an electrode the lamellar graphite particles parallel to an underlying current sensor film (horizontally). This leads to confused communications through the electrode pores. The lithium ions, the positive electrode in the negative of the diffusing and vice versa, must pass through this pore away confused. Particularly in the case of high loading rates can not sufficiently rapidly through the pores of the lithium ions moving, reduce the usable storage capacity can lead what. By the alignment of the graphite particles can the path lengths, the lithium ion on loading and unloading and cover, and the loading and unloading of an electrochemical properties - be reduced to improve memory.

[0003] For the industrial preparation of negative electrodes is the lamellar graphite graphite often rounded. Up to 70% of the original material in the mechanical however lost rounding process.

[0004] The application of a magnetic field on an object is known. A halfoh array is a special configuration of permanent magnets. Such a configuration allows, that the magnetic flux on the one side the configuration removes almost, but on the other hand increased, also known under the name "on the one-sided fluxing" ("one-sided flow" dt.). A further property of such a configuration is, that the direction of the magnetic flux changes at the surface of the configuration in the direction of the magnetic field locally - function of location rotates.

The EP 2,793,300 a1 discloses a application for manufacturing electrodes, wherein magnetic nanoparticles are applied electrochemically active particles, which in turn ("slurry" or "pastes" dt.) as a slurry applied to a substrate and then a magnetic field is applied to the particles. This suspension must be subsequently solidified, for example by drying. The addition of magnetic nanoparticles in the preparation of the graphite paste may complicate the process. Due to the addition of magnetic nanoparticles it can come to undesired electrochemical processes, may have adverse effects on the final product. A method for applying a continuous magnetic fields not is disclosed.

[0005] The patent us 7,326,497 b2 describes a negative electrode for use in a rechargeable lithium ion and same battery. It is disclosed a method, wherein the graphite coating is aligned in a magnetic field having a flux density greater than 0.5 T between two magnets. To obtain good vertical orientations, flux densities of over 1 tonnes or even proposed 2.3 tonnes. In this area are technically difficult to implement flow densities, it needs for such high flux density for example superconducting magnets.

[0006] In a further patents described us 7,976,984 b2 is a rechargeable battery, wherein the graphite particles in a magnetic field are aligned mechanically rounded.

[0007] By the alignment of the graphite particles in a magnetic field may the path length of the rounded lithium ion and in the loading and unloading - although slightly shortened properties are improved, this enhancing effect is further reinforced by the use of flake-like graphite. But is, as mentioned above, up to 70% of the original material lost in rounding process.

[0008] The invention is therefore based on the problem, a method for applying magnetic fields, particularly for continuously applying magnetic fields on an object, in particular a layer or a, with a layer is coated article, and more particularly to a graphite coating of producing an article in the form of a negative electrode to develop.

[0009] The task is solved with the features of Patent claim 1.

[0010] The article, only a layer also may be, for example graphite can, a binder and a, volatile solvent by drying are, said method at least one quasi-continuous application in particular manufacturing and/or processing method of negative electrodes during a - quick-loading for example lithium ion batteries because of the specific magnetic field configuration allows and graphite particles without the addition of magnetic nanoparticles wherein flux density acting diamagnetic of less than 0.5 tonnes can orient vertically.

This is the meaning of "in a continuous production process" continuously such as "roll-to-roll processing" and not as "constantly" defined.

[0011] Invention is a magnetic field by halfoh array directly on the article, in particular a graphite coating consisting of graphite particles, a binder and the volatile solvent with a preferably flat or rectangular training applied in drying, wherein the graphite coating halfoh array is moved relative to a (tool).

[0012] There is a demand for technologies, which allows a rapid loading of electrochemical storing. The state of the art already discloses the advantage of vertically oriented graphite particles in the negative electrode of battery electrodes. But fall short simple manufacturing - or machining method, applying a continuous magnetic fields during the manufacturing or machining method of graphite coatings -, the lamellar graphite contain, allow.

The action of magnetic fields on graphite coatings to the method allows for alignment of lamellar graphite particles in a contained therein, for industrial manufacturing suitable manner.

[0013] Graphite and has a diamagnetic anisotropy is diamagnetic. As a result, at right angles to that at a (002) plane of the graphite diamagnetic susceptibility about 40 - 50 - times the magnetic field acting as large as in the case of perpendicular to the (110) plane acting magnetic field.

Consequently the energy leads to stabilization of the graphite in the magnetic field, the (002) plane of the graphite - extends parallel to the magnetic field aligns. The method is based on a number of permanent magnets are arranged in a special order. The permanent magnets can both a planar, cylindrical and be arranged. The relative movement of the graphite coating to the magnet arrangement described results, that the diamagnetic graphite particles are exposed to a rotating magnetic field, the diamagnetic containing graphite particles in the coating which aligns vertically.

The subsequent immobilization can take place for example by drying the aligned graphite particles. A drying, is characterized, in that a graphite coating the graphite coating contained solvent leaves, this leads for immobilizing said vertically oriented graphite particles.

The drying can both passive, e.g. due to the ambient temperature, i.e. not supported take place, as well as active, i.e. for example by a targeted drying with a fan.

The aim of the process of the invention is a continuous application to allow magnetic fields, for example for the production of negative electrodes with vertically oriented graphite particles by influencing the constituents of the graphite coating.

[0014] The technical benefits include the possibility, magnetic fields of a magnetic or a magnetic roll on for example a graphite coating package, consisting of diamagnetic graphite particles to act. The magnet or the magnetic packet as part of a continuous manufacturing process the properties roller may, for example a graphite coating in the production of electrodes change, for example for use in lithium-ion batteries.

[0015] Preferred embodiments of the invention are disclosed in the dependent claims process.

[0016] The invention is described with reference to an embodiment subsequently in a drawing. In the drawing show the

Fig. 1: a halfoh array with rigid, planar permanent magnet; (010),

Fig. 2: a halfoh array, is formed as a rotatable roller core;

Fig. 3: a scanning electron microscope receiving a graphite coating in cross section;

Fig. 4: a histogram for orientation of graphitic particles;

Fig. 5: a further scanning electron microscope receiving the graphite coating

Fig. 6: a further histogram for orientation of graphite particles.

[0017] 97 g of flake-shaped graphite is 25 g of a carboxymethyl cellulose (CMC is) solution (2 wt %) with 41 g of de-ionized water for 1 hour and then with 25 g of CMC solution further kneaded and (2 wt %) and 30 g of deionized water with stirring diluted.

To this mixture is then 5 g of a SBR latex (40 wt %) and stirred for 2 min supplied.

[0018] The resulting graphite paste is thereafter with a doctor blade onto an article 011, a copper foil (thickness of the copper foil to 15) applied, the previously between two, not shown circular rubber rollers was clamped.

[0019] Then the two rubber rolls are driven by an electrical motor for rotation brought, so that the copper foil with the coating at a speed of 3 m/thereon in the example circuit moved in minutes. A magnet is then in the form of a rigid insertion, 010 (Fig. 1) planar magnetic insert, consisting of Flalbach array, placed under the moving copper foil.

[0020] The planar permanent magnet acting on the moving object Flalbach arrays with 010 011.

[0021] With the coating on the copper foil is moved past magnetic insertion 011, there is relative movement between the magnetic insert and copper foil respectively. The distance to the copper foil is 3 mm in the example with a Gaussian meters and determined, acting flux density is the actually measured flux density corresponds to the B.E.T. 0.35 at the location of the graphite coating acting flux density.

According 3 min is the liquid graphite coating on together with hot air blown thereby moving copper foil with the graphite coating for FHeizpistolen brought drying. The solvent is removed and the graphite particles immobilized in vertically aligned.

Application of the magnetic field is a substantially before introduction of the active drying phase (and during).

[0022]Arotating magnetic field for the graphite particles, can come about in the alternative, that the graphite particles of an article to a rotatable 022relativ, halfoh array 021 020 moving on a roller core, as represented in the Fig. 2 is. This is a halfoh array as rotatable rollers formed core (021), extending around a fixed center (020) and on which a subject can move to be coated (022) is moved past.

[0023] The Figure 3. shows a micrograph of a cross section of a graphite coating with flake-like grid electrode graphite, without the action of a magnetic field was obtained. The lamellar graphite particles lie parallel to the underlying current sensor film.

Fig. 4 is a histogram of the orientation of the graphite particles in a graphite coating represented, without the action of a magnetic field was obtained.

Fig. 6 shows a histogram of the orientation of the graphite particles in a graphite coating, in a magnetic field by the procedure described in the example was obtained.

The lamellar graphite particles are vertically (90° angle in) for current collector film covered by majority. A raster microscope analysis of a cross section of the electrodes in the example by keeping graphite coating shows (Fig. 5) vertical alignment of the lamellar graphite particles. Fig. 5 shows a micrograph of a cross section of a graphite coating this grid electrodes aligned with flake-like graphite, the procedure described in the example by the obtained in a magnetic field.

The lamellar graphite particles are vertically (90° angle in) for current collector film covered by majority.

[0024] The analysis of the coating by means of a X-ray diffraction device (RiagakuSmartLab) shows a significantly increased amount of graphite particles, whose (110) - plane vertically, i.e. 90 °, for copper foil are aligned, in comparison with a graphite coating, not the rotating magnetic field (Fig. 3 and Fig. 4) is exposed.

[0025] Graphite coating obtained according to the invention with the vertically oriented lamellar particles contained therein to a porosity of 30% is then calendered.

A further, subsequent analysis by means of a X-ray diffraction device the compressed graphite coating showed a significantly increased intensity for further (RiagakuSmartLab) graphite particles, whose (110) - plane is oriented vertically for copper foil.

[0026]

010 Halfoh array with permanent magnets

011 the magnetic field acts on the object being moved

020 fixed center, about which a rotatable roll core moved

021 Rotatable halfoh array with permanent magnets

022 the magnetic field acts on the object being moved