Lithium ion battery lithium-enriching technology and lithium ion battery prepared by the technology

Abstract

The invention discloses a lithium ion battery lithium-enriching technology and a lithium ion battery prepared by the technology. The lithium-enriching technology comprises the following steps: evenly pre-mixing lithium powder and EC powder under a dry state at a temperature which is lower than the melting point of EC, then heating the mixture to a temperature which is higher than the melting point of EC to melt EC powder to evenly disperse lithium powder in the EC solvent so as to obtain lithium powder slurry; painting the obtain lithium powder slurry on at least one of the positive electrode sheet, the negative electrode sheet, or the diaphragm of a lithium ion battery, and then cooling to a temperature that is lower than the EC melting point so as to obtain a positive electrode sheet, negative electrode sheet and / or diaphragm containing a lithium-enriched surface layer. Compared to the prior art, the lithium-enriching technology has the advantages of simple preparation method, even dispersing effect, and no destruction on the surface protective layer of lithium powder during the dispersing process, moreover, the lithium-enriched layer does not to be dried after painting, and thus the phenomenon that lithium powder is oxidized and released into the air during the high temperature baking process is effectively avoided.

Description

technical field [0001] The invention belongs to the field of lithium-ion batteries, and more specifically, the invention relates to a lithium-rich process for lithium-ion batteries and a lithium-ion battery prepared by using the process. Background technique [0002] Since the large-scale commercialization of lithium-ion batteries, they have been widely used in portable electrical appliances such as laptops, cameras, and mobile communications due to their high energy density and high power density. However, with the continuous updating of the design of consumer electronic products and the gradual increase of integrated functions, the requirements for battery energy density and performance improvement are also getting higher and higher. [0003] In order to increase the energy density of lithium-ion batteries, an important direction is to use high-capacity anode materials, such as silicon-carbon anodes and alloy anodes. However, these high-capacity negative electrode materia...

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Problems solved by technology

However, these high-capacity negative electrode materials all have the problem of relatively low initial efficiency. If the initial efficiency cannot be improved by enriching lithium, the energy density of lithium-ion batteries will not be significantly improved.

[0004] Although lithium-rich is an effective means to improve the efficiency of lithium-ion batteries for the first time, there are many problems in the current process methods, which need to be further improved. The slurry is coated on the current collector and the slurry is dried to achieve the purpose of enriching lithium; however, after the lithium powder in the pole piece prepared by this process is absorbed by the negative electrode active material, it will remain in the position of the original lithium powder in the pole piece. The contact impedance between the particles in the pole piece is deteriorated due to the lower hole; 2) Someone proposes to filter the lithium powder from the filter screen and sprinkle it on the surface of the pole piece to form a lithium-rich layer through vibration and electric field; this method has the advantages of simple process, The advantage of not needing to prepare slurry, but its production efficiency is relatively low, and in the actual operation process, there is a problem of uneven lithium powder spilling in the width direction of the pole piece, and it is also easy to cause lithium powder to float, which poses a great safety hazard; 3) It has also been proposed to enrich lithium by covering the surface of the negative electrode with a layer of lithium sheet. However, since the thickness of the currently available lithium sheet is far greater than the lithium-enriched amount required by the negative electrode sheet, the excess lithium will cause a lot of damage in the battery. 4) It is also proposed to use vacuum evaporation to deposit a lithium metal layer on the surface of the pole piece to enrich lithium, but this method needs to be carried out in a high vacuum environment and has The shortcomings of low efficiency and high overall process cost; 5) Some people have proposed to add lithium powder to solvents such as NMP to prepare lithium powder slurry, and then apply the lithium powder slurry to the pole piece or separator, and then heat and dry. The lithium-rich layer is obtained by volatilization of the solvent; one of the problems of this process is that the lithium powder is very light and easy to float, and it is difficult to disperse evenly when it is directly added to the solvent. Both stirring methods are easy to damage the protective layer on the surface of lithium powder; the second problem of this process is that the removal of solvent requires heating and drying, and heating and drying can easily lead to rapid oxidation of lithium powder, and due to the heating and drying of EC and PC solvents The temperature needs to be above 200°C, so it will also cause a certain degree of damage to the performance of the separator and the pole piece; 6) Some people solve the problems in method 5) by drying the lithium powder slurry under the protection of nitrogen at 50°C , which can indeed avoid the damage of lithium powder, pole piece, and separator due to high-temperature drying, but it brings two other problems: one is that nitrogen itself will react with lithium; the other is that nitrogen, as a dry atmosphere, will consume and ancillary equipment will bring about a large cost increase

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