Pre-lithiation method for lithium ion battery

Abstract

The invention discloses a pre-lithiation method for a lithium ion battery, and the method comprises the following steps: mixing lithium powder, a conductive agent and a polymer in a dry powder state at room temperature, adding a proper amount of lithium salt according to the condition, performing stirring to achieve the uniform pre-mixing, performing heating or adding an organic solvent, and finally performing stirring to obtain uniform multi-element mixed slurry; directly coating the surface of a negative plate of the lithium ion battery with the multi-element mixed slurry through different coating methods, and performing cooling or volatilizing a solvent to obtain a negative plate with a lithium-rich conductive coating on the surface layer; and finally, obtaining the lithium ion batteryby assembling the negative plate with the lithium-rich conductive coating on the surface layer. The pre-lithiation degree is controllable, the process is simple, the cost is low, the method is suitable for large-scale production, and meanwhile, the initial coulomb efficiency and the cycle stability of the lithium ion battery can be remarkably improved.

Description

technical field [0001] The invention belongs to the field of lithium-ion batteries, and in particular relates to a method for pre-lithiation of lithium-ion batteries by using a lithium-rich conductive coating. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, high safety, long cycle life and low self-discharge rate, making them a research hotspot in the field of energy storage today. In order to further increase the energy density of batteries, high-capacity anode materials (such as silicon-based, tin-based, and metal oxides, etc.) have been introduced into lithium-ion batteries. However, unlike lithium ion intercalation reaction negative electrode materials, this type of material has a large initial irreversible capacity loss during the charge and discharge process. The loss of the irreversible capacity for the first time consumes a large amount of lithium ions extracted from the electrolyte and positive electrode materials, re...

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Problems solved by technology

It is also more convenient and direct to carry out "dry spraying" lithium powder on the surface of the negative electrode to replenish lithium in practical applications. However, due to the large dust in this method, there is a great potential safety hazard; The fluctuation range of pre-lithiation is wide and it is difficult to control

Someone dissolves lithium powder in an organic solvent and sprays it on the surface of the negative electrode sheet. Although this wet spraying effectively solves the dust problem encountered in dry spraying, it also introduces new problems: First, the density of lithium powder It is small and easy to float, and it is difficult to disperse evenly when directly added to the solvent. If you want to disperse evenly, you must use high-intensity stirring, but this stirring method is easy to damage the protective layer on the surface of lithium powder; second, after the organic solvent volatilizes It is easy to cause certain harm to people and the environment; the third is the coating method, that is, the method of coating a lithium thin film on the surface of the negative electrode by using atomic layering method, chemical vapor deposition method and magnetron sputtering method.

Although this method can effectively control the amount of lithium supplementation, additional equipment needs to be purchased, and during the coating and transfer process, it is necessary to prevent the lithium sheet from being nitrided and oxidized, and the cost is high, which is not conducive to commercial promotion and application.

[0004] In short, although the above method can effectively improve the first coulombic efficiency and cycle stability of lithium-ion batteries, it also has the disadvantages of destroying the pole piece, difficulty in controlling the degree of pre-lithiation, dust, organic solvents, and high cost, which restrict the large-scale production of lithium powder. commercial use

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