Lithium ion battery positive pole piece with safety coating and preparation method of lithium ion battery positive pole piece

Abstract

The invention relates to a lithium ion battery positive pole piece with a safe coating and a preparation method thereof, and the method comprises the following steps: preparation of safe coating slurry: adding a matrix material aerogel material, a high-stability positive pole material, a conductive agent and a binder into a dispersant, and dispersing to obtain the safe coating slurry; preparing positive electrode active material slurry: mixing and stirring raw materials of the positive electrode active material to obtain the positive electrode active material slurry; multi-layer extrusion coating: coating a positive electrode current collector (001) with the safe coating slurry and the positive electrode active material slurry; and cold pressing: carrying out cold pressing on the coated positive current collector (001) to obtain the lithium ion battery positive pole piece with the safety coating. Compared with the prior art, the method has the advantages that the influence on the electrical performance of the battery cell is avoided, the production period is shortened, the production cost is reduced and the like.

Description

technical field [0001] The invention relates to the field of electrochemistry, in particular to a positive pole piece of a lithium ion battery with a safety coating and a preparation method thereof. Background technique [0002] With the large-scale application of lithium-ion batteries, the number of accidents such as fire and explosion is increasing day by day, so the safety function of lithium-ion batteries needs to be improved urgently. Internal short circuit is an important cause of safety accidents in lithium-ion batteries. After internal short circuit occurs due to thermal abuse, mechanical abuse, etc., after the short circuit point generates heat, the temperature rises, triggering a reaction, further heat generation, and the formation of H-T-R (Heat-thermo -reaction) cycle, eventually triggering thermal runaway. [0003] According to the structure of the short circuit point, the short circuit in the lithium battery is divided into four types: positive electrode-negat...

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Problems solved by technology

[0006] However, this two-step coating method has brought the following problems: (1) if the safety coating also uses an oil phase dispersant such as NMP, while the positive electrode active material slurry mainly uses NMP as a dispersant, so in When coating the positive electrode active material slurry, a part of the safety coating will be dissolved, resulting in mixing, and destroying the interface between the safety coating and the positive electrode active material. The battery manufactured by using this kind of pole piece has a large DCR and fast growth. , CPK increase and other issues; and if the safety coating uses water as a dispersant, due to the high surface tension of water, the surface dyne value of aluminum foil is much lower than that of copper foil, resulting in a narrow processing window and it is difficult to ensure a safe coating Complete coverage, and the use of water-based binders on the positive electrode will affect the performance of the battery. Therefore, the electrical performance of the battery prepared by using the current safety-coated positive electrode sheet will deteriorate to a certain extent;

[0007] (2) The existing safety coating has no capacity or uses a high-stability positive electrode material with a low capacity as the main material, which will cause a loss in the energy density of the battery cell

However, in the existing coating methods of safety coatings, the lower limit of the thickness of transfer coating and extrusion coating is about 10 μm, which cannot meet the requirements of the energy density of the battery cell.

The coating thickness of spraying can be very low, but it cannot guarantee that the surface of the positive electrode current collector is completely covered by the safety coating, which cannot meet the requirements of safety performance

Therefore, gravure coating is often used at present, but in the case of ensuring that the positive electrode current collector is not exposed, the lower limit of the coating thickness is also relatively large, at about 3 μm, it will still cause 1-3% loss to the energy density of the battery cell ;

[0008] (3) Compared with the coating of conventional positive electrodes, it is necessary to add coating equipment for safety coatings, which increases the production cycle and increases production costs

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