A kind of method of lithium ion battery pre-lithiation

Abstract

The invention relates to a method for pre-lithiation of a lithium ion battery, comprising the following steps: placing a bare battery cell in an electrolyte solution under an inert atmosphere condition, and respectively placing lithium metal strips in the electrolyte solution on both sides of the bare battery cell; Take two power supplies, the positive poles of the two power supplies are connected to the negative poles of the bare cell, and the negative poles of the two power supplies are respectively connected to two metal lithium strips to charge the negative pole of the bare cell. Pre-lithiation of the negative electrode; after the charging is completed, the bare cell is taken out from the electrolyte, and the bare cell is made into a lithium-ion battery according to the procedure; the design of the present invention adopts the "wet pre-lithiation", which has low cost and high production safety , Easy to operate and easy to use in large-scale mass production; and it can evenly pre-lithiate the negative electrode of lithium-ion batteries, and the amount of pre-lithium can be controlled more accurately by controlling the time and the current of the external circuit.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a method for prelithiation of lithium ion batteries. Background technique [0002] Lithium-ion batteries are currently the battery system with the highest energy density among commercial secondary batteries. Commercial lithium-ion batteries have good cycleability and safety in use. They have been widely used in communications, transportation, electronic equipment, and industrial products. , and quickly obtain a larger market. [0003] For the negative electrode of a lithium-ion battery, it will consume part of the lithium ions due to the formation of a solid electrolyte film (SEI film) during the first charge of the battery; although this film is beneficial to the cycle stability of the positive and negative electrode materials, However, it will cause lithium loss of part of the positive electrode material, resulting in a reduction in the first Coulombic efficiency...

AI Technical Summary

Problems solved by technology

[0008] As the name implies, Slurry application is mainly to add SLMP in the process of slurry mixing. This method is relatively simple to use and has a high utilization rate of SLMP. However, since SLMP is added in the process of slurry preparation, the solution required for slurry must not Those that react with lithium metal are mainly organic non-polar solvents such as hexane, pentane, and benzene, which are highly toxic and difficult to produce in large quantities; and from stirring to packaging, they need to be carried out in a dry environment, resulting in an increase in the cost of cell production ; In addition, because SLMP is dispersed inside the pole piece, but after liquid injection or charging and discharging, the lithium of the metal particles is embedded in the material, resulting in more pores inside the pole piece, increasing the internal resistance of the pole piece, so this method Not suitable for prelithiation

[0009] Surface application refers to pre-lithiation on the surface of the pole piece (CN201210237240.4), that is, coating SLMP on the surface of the pole piece; this method can uniformly coat SLMP on the surface of the pole piece in different ways, and the operation is relatively convenient. But the main disadvantage is the lack of safety; although SLMP is relatively stable, its surface is mainly a layer of lithium carbonate with a thickness of nanometer level, so it is relatively active lithium metal, and its density is basically the same as that of lithium metal, so it is very easy to cause dust

[0010] The second is the pre-lithiation of ultra-thin lithium foil. This method is mainly to cover the surface of the pole piece with thin lithium foil, and compound the lithium foil to the pole piece by rolling; after the liquid injection process, the metal lithium foil will be combined with the pole piece. Chemical and electrochemical lithium intercalation reactions occur to complete the pre-intercalation of lithium on the pole piece; because the thin lithium foil has a smaller specific surface area than SLMP, it is simpler and safer to use and operate, but because the battery The thickness of lithium foil required for pre-lithium is very thin, usually only 3-20um, or even thinner. The price of lithium foil products currently on the market cannot meet the demand, and at the same time, the thickness cannot meet the demand, so the battery is prone to lithium precipitation and other safety issues. Hidden danger

[0011] Furthermore, vacuum evaporation pre-lithiation, which mainly uses physical vapor deposition (PVD, Physical vapor deposition), uniformly deposits a layer of metal lithium on the surface of the negative electrode; its biggest advantage is that a relatively thin lithium layer can be obtained, Because of its limited evaporation rate, one of its disadvantages is that the amount of pre-lithiation is limited; in addition, due to vapor deposition, the particle size of lithium metal on the surface is mainly on the order of nanometers, and its activity is relatively large, so the production conditions required are extremely high. Harshness and high production cost limit the further development of this method

[0012] In view of the above analysis, although adding metal lithium powder, lithium foil, and evaporation methods to lithium-ion batteries can significantly improve the first-time efficiency of the battery, etc., and have been verified experimentally, it has not been widely promoted. In addition to its own safety performance and price, its environmental restrictions and safety factors in the use process are also a major reason for restricting its promotion.

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