Pole piece film and preparation method and application thereof

Abstract

The invention relates to a pole piece film and a preparation method and application thereof, the pole piece film comprises a polymer with a networked structure and powder bonded to the surface of thepolymer, the powder comprises an active material and an auxiliary material, and the auxiliary material comprises a lithium supplement additive; and a battery prepared from the pole piece film has highfirst effect and capacity and excellent cycle performance. The preparation method comprises the following steps: premixing the active material, the auxiliary material and the fiberable polymer, drawing the fiberable polymer under the effect of a shearing force to form fibers, enabling the auxiliary material to contain a lithium supplementing additive, and performing hot pressing treatment to a preset thickness to obtain the pole piece film. By the adoption of the method, no solvent needs to be introduced in the whole process, the tedious processes that the lithium supplementing amount is attenuated due to existence of the solvent and the solvent needs to be removed through further baking are avoided, the lithium supplementing amount can be accurately controlled, meanwhile, the lithium supplementing additive is evenly mixed into the electrode powder through the method, more uniform lithium supplementing can be achieved, the problem of lithium supplement gradient is avoided, and the preparation method is simple to operate.

Description

technical field [0001] The invention belongs to the field of batteries, and relates to a pole piece film, a preparation method and application thereof. Background technique [0002] With the rapid development of new energy vehicles, the requirements for energy density and safety performance of vehicle power batteries are constantly increasing. It is estimated that by 2025, the energy density of power batteries will reach more than 500Wh / kg. With the continuous improvement of the energy density of power batteries, the gram capacity and compaction density of existing negative electrode materials have reached the limit value. Therefore, the use of silicon carbon materials will be a hot spot in the future. At the same time, the low initial charge and discharge efficiency of silicon carbon materials, large expansion, and long-term cycle will bring about material pulverization problems, as well as matching problems with related electrolytes and glues, which have always plagued re...

AI Technical Summary

Problems solved by technology

[0005] Among the current lithium supplementation technologies that can be industrialized, lithium powder and ultra-thin lithium strips are the main research trends. However, in the preparation process of ultra-thin lithium strips, the requirements for technology and equipment are high, and high-precision rollers are required. Press equipment and some specific protective films and lubricating oil are used to assist; and at present, the thickness of the lithium belt is difficult to be less than 3 μm. If the lithium belt above 3 μm is directly used to supplement lithium, it is too much for most existing systems. , in the process of cell cycle, it is easy to cause lithium to be separated from the pole piece, resulting in short circuit of the battery

Lithium supplementation with lithium powder can achieve more precise control of the amount of lithium supplementation, but lithium powder is light in weight, prone to agglomeration, and more dangerous, which brings a lot of inconvenience to industrial production

At present, wet lithium supplementation is mostly used. ① fully disperse lithium powder, solvent and stabilizer, and disperse it on the negative electrode in a certain way, but most of the dispersion effect is average and the electrode needs to be further dried to remove the residual solvent. ;②Add passivated lithium powder directly in the mixing process of pole pieces. This method has more stringent requirements on the mixing process, increases the selection of inert solvents, and the process steps are cumbersome

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