Preparation method of lithium ion battery cathode sheet, and film coating and drying apparatus

Abstract

The invention discloses a preparation method of a lithium ion battery cathode sheet. The method comprises steps that: a cathode slurry containing graphite is prepared and is coated on a substrate; slurry drying is carried out upon the coated substrate, and a magnetic field is applied on the slurry being dried during a phase when the viscosity of the slurry reaches the lowest point, such that (004) planes of graphite particles are perpendicular to the substrate plane; then the magnetic field is removed, and the slurry is continuously dried until the slurry turns solid. The invention also discloses a film coating and drying apparatus used for realizing the method. According to the invention, magnetization is carried out upon graphite during the drying phase when the viscosity of the slurry reaches the lowest point. Therefore, turning resistance is reduced, alignment consistency of the (004) planes of the graphite particles is improved. Also, when the graphite particles are turned, the slurry is instantly processed through a drying phase wherein the slurry solid content and the slurry viscosity are rapidly increased, such that high consistency on a graphite particle alignment direction is maintained, and highly-oriented alignment of graphite in the cathode sheet is realized.

Description

technical field [0001] The invention relates to the field of preparation of lithium-ion batteries, in particular to a preparation method and related equipment of high-performance lithium-ion battery negative electrodes. Background technique [0002] Lithium-ion batteries usually use graphite as the negative electrode active material. Graphite has a layered structure. During battery charging, lithium ions are inserted from the edge of the layered graphite into the gap between the graphite layers, thereby obtaining Li-graphite inclusion compounds. [0003] Since most graphite particles are in the form of flakes, when preparing the negative electrode sheet, the plane of the graphite layer is usually parallel to the plane of the current collector, and the edges of the graphite layer are arranged perpendicular to the direction of the positive electrode. However, the resistivity of the graphite-containing composition in the plane direction of the graphite layer is about 1000 times...

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Problems solved by technology

Although this method can improve the performance of the negative electrode sheet to a certain extent, it still cannot achieve the best effect. This is because the graphite particles arranged by the magnetic field still have a large degree of freedom. After the magnetic field is removed, the negative electrode sheet is dried. Before, there is still a part of the graphite particles that will turn in the slurry

In order to avoid this situation, someone proposed to keep the magnetic field during the drying process. Although this method can ensure the alignment of graphite particles, the equipment is complicated, not only the manufacturing cost is high, but also the use of electromagnets to generate the magnetic field also requires a lot of energy.

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