Improved lithium ion battery manufacture process

Abstract

The invention discloses an improved lithium ion battery manufacture process, comprising the steps of: cutting a positive current-collector aluminum foil, and coating a positive electrode material on two faces of an aluminum foil current collector to obtain an positive electrode piece, wherein the positive electrode materials is prepared by uniformly mixing and stirring lithium nickelate, lithium iron phosphate, lithium vanadium oxides, lithium cobalt oxides, lithium manganese oxides and an adhesive electric conductive agent in proportion; cutting a negative current-collector copper foil, and coating a negative electrode material on two faces of a copper foil current collector to obtain a negative electrode piece, wherein the negative electrode material is prepared by uniformly stirring one of natural graphite, artificial graphite or hard coke, an adhesive of polyvinylidene fluoride and NMP (N-Methyl-2-Pyrrolidone), and deionized water; heating and drying in a vacuum container after the above steps are completed; alternatively stacking and assembling diaphragm materials between the positive electrode material and the negative electrode material for separation after the drying step is completed; and after the assembling step, filling an electrolyte solution, forming and exhausting gas, sealing an air vent and carrying out capacity grading and parameter testing. Because the drying is finished in the vacuum drying oven, the quality problems that the manufactured positive electrode and the manufactured negative electrode are wet inside and dry outside and are easy to chap on the surface, and the like are solved.

Description

technical field [0001] The present invention relates to a method for manufacturing lithium-ion batteries, in particular to improve the manufacturing process of lithium-ion batteries. The method includes manufacturing a negative electrode and a positive electrode, and placing a separator material between the negative electrode and the positive electrode to stack and assemble the lithium-ion battery. The process includes The following steps: [0002] Positive electrode current collector aluminum thin → cutting sheet → coating positive electrode material such as: lithium nickelate (LiNiO 2 ), lithium iron phosphate LiFePO 4 , lithium vanadium oxide (VOPO 4 、LiVO 2 ), lithium cobalt oxide, lithium manganese oxide, and the binder conductive agent are mixed and stirred evenly in proportion, and then coated on both sides of the aluminum foil current collector to form a positive electrode sheet. [0003] Negative electrode current collector copper thin → cutting pieces → coating n...

AI Technical Summary

Problems solved by technology

[0008] (1) In order that the coating film of the active material of the positive and negative electrodes of the lithium battery will not be detached from the current collector and will not produce cracks, the adhesion fastness must be increased, and the adhesion fastness is increased by improving the adhesive and increasing the adhesive Increase the binder will cause volume occupation, the more the binder, the less active material in the positive and negative electrodes, which not only reduces the specific energy of the battery, but also increases the internal resistance due to the increase of non-conductive substances, The performance of the battery will be lost, but the lack of binder will cause the coating process to drop slurry and the coating will loosen, resulting in an increase in the scrap rate

[0009] (2) The existing process is: first side coating→drying→winding→second side coating→drying→winding→grinding and pressing→winding→slit cutting→winding→section cutting→ Winding the battery core, the process is four times of winding and unwinding processes. Since the coating layer of the active material of the positive and negative electrodes of the lithium battery is not a flexible body, after four winding and unwinding processes, the positive and negative electrodes of the lithium battery will inevitably be damaged. Cracks in the coating layer of the active material and damage to the adhesion fastness to the surface of the polar fluid, resulting in loosening and the formation of gaps, whether it is a crack in the coating layer of the active material of the positive or negative electrode or damage to the adhesion fastness to the surface of the polar fluid, resulting in Looseness and gaps will cause changes in the internal resistance of the battery, which will inevitably lead to uneven current and uneven temperature, resulting in an excessively high temperature zone, causing the active materials of the positive and negative electrodes to loosen from the current collector, further causing an increase in internal resistance

[0013] The quality of the coating process of the active material of the negative electrode is closely related to the folding resistance of the copper foil. Different types of lithium-ion batteries have different requirements for the folding resistance of the copper foil. The manufacturing of lithium batteries by the winding process requires better copper foil. Copper foil with poor folding resistance may crack or even break during the folding process in the winding process. Cracks will affect the density uniformity of the active material and will also cause changes in internal resistance. Electrolytic copper foil and rolled copper The folding resistance of copper foil has a significant difference, but the high price of rolled copper foil will significantly increase the cost

[0014] The quality of the coating process of the active material of the negative electrode is closely related to the tensile strength and elongation of the copper foil. The copper foil must have sufficient tensile strength and elongation. In the process of rolling, grinding and flattening, the contact performance between the copper foil and the active material will deteriorate, which will deteriorate the dimensional stability and flatness of the negative electrode sheet, and the excessive elongation will cause the active material of the negative electrode to adhere to the in-situ displacement , the active material of the negative electrode adheres to the in-situ displacement, which will affect the yield of the negative electrode, battery capacity, internal resistance and cycle life, etc. If the elongation rate is too small, it will cause breakage and cracks. It is also a material property that is very difficult to control.

[0015] The coating process of the active material of the positive and negative electrodes adopts the ordinary hot air convection drying method or the drying cylinder heat conduction drying method. The drying efficiency is low and the solvent volatilization is large, resulting in increased cost and serious environmental pollution. Due to the heat transfer on the surface, the dried coating The layer often has quality problems such as external dryness and internal humidity or surface chapping, and surface chapping will also increase internal resistance

[0016] The manufacturing process of the positive electrode and the negative electrode sheet adopts the same coating process, and the defects of the coating process of the active material of the negative electrode exist at the same time in the manufacture of the positive electrode sheet