Method for making battery positive plate and positive electrode slurry thereof

Abstract

The invention discloses a method for fabricating a battery positive electrode plate, and a positive electrode paste thereof. The method comprises the following steps: (1) producing a cold-rolled plate to an expanded steel mesh, and coating a Ni layer on the outer surface; (2) mixing and stirring the following components based on the weight ratio to obtain a paste: H2O: 1% of CMC:1% of PMMA: CoO: C powder: Ni(OH)2: 4% of PTFE is equal to (16 to 18):(1.5 to 2.5):(1.5 to 2.5):(1.5 to 5.0):(3 to 15):(80 to 95.5):(0.5 to 1.5); (3) coating the paste on the expanded steel mesh; (4) drying and rolling; and (5) cutting the positive electrode plate into pieces by a cutting machine. The mesh holes of the expanded steel mesh have a maximal diagonal distance of 1.0 to 3.5 mm, and a minimal diagonal distance of 0.5 to 1.5 mm. The addition of the hydrophilic 1% of PMMA in the paste can improve the product stability to prevent the positive electrode powder from cracking and dropping in the drying process. The expanded steel mesh is adopted as the base material and has the advantages of low cost and simple manufacture process.

Description

technical field [0001] The invention relates to a battery, in particular to a method for making a positive electrode plate of a battery and the positive electrode slurry thereof. Background technique [0002] NiMH and NiCd batteries are widely used in various portable household appliances, digital cameras, mobile communications and other fields. As an important clean energy source in chemical power sources, it is very important to improve the material selection and production methods of nickel-metal hydride and nickel-cadmium batteries. Among them, the positive electrode active material and the positive electrode conductive substrate are the parts that have the greatest impact on the battery. In the traditional method, the positive electrode conductive substrate is mostly made of foamed nickel or nickel-plated punched steel strip, and the positive electrode active material is Ni(OH). 2 . [0003] Ni-MH, Ni-Cd battery cathode matrix material acts as a three-dimensional cond...

AI Technical Summary

Problems solved by technology

[0004] Foamed nickel has the following problems as the positive base material of nickel-metal hydride and nickel-cadmium batteries: the produced pole piece is easy to break during the production process, resulting in scrapping, and cracks will occur after winding, resulting in low capacity of the battery and affecting the consistency of the battery ; And the foamed nickel is pure nickel metal, the material is expensive, which greatly increases the cost of nickel-metal hydride and nickel-cadmium battery materials

But there are still several problems: first, the bonding performance of the active material material and the nickel-plated punching steel strip is poor, because part of the active material is attached to the both sides of the nickel-plated punching steel strip and is not in the pores, it is cut in the positive plate, During the transmission process, there are jitters and easy to fall off. Second, the perforation burrs on both sides of the nickel-plated punching steel strip, that is, the peaks, are easily deformed when they are pressed through the drawing die, which may lead to uneven distribution of active materials. After the pole piece is wound, it is easy to pierce the diaphragm and cause a short circuit, etc.

This technology uses steel mesh as the positive electrode matrix material, which reduces the cost, but there are still problems: first, the use of 3.85% CMC and 4% PTFE can not achieve uniform powder coating even if the ratio is adjusted

Because the prepared slurry has poor fluidity and high water content, the slurry can only be coated on the steel mesh after drying part of the water, and there will be obvious cracks after drying, cutting or other treatments will cause the electrode powder to fall off; and winding also cause shedding

Secondly, after the battery is formed, the capacity performance is obviously worse than that of the foamed nickel substrate, the internal resistance of the battery is also obviously high, and the battery life is short

The above problems are mainly caused by the unreasonable size of the stencil matrix used and the positive electrode formula: hydrophobic PTFE is a non-polar adhesive, the surface is highly hydrophobic, and the PTFE emulsion has good alkali resistance, but the viscosity is too high. Low, cannot be used alone as the positive electrode binder material, it needs to be used in conjunction with a hydrophilic binder

The hydrophilic CMC has good water solubility, thickening, bonding, film forming, protective colloid, moisture retention and dispersion stability, but it is easy to swell and powder, so it is not suitable for independent use

Add 4% PTFE and 3.85% CMC of different viscosity materials as thickeners to adjust the viscosity of the slurry. The prepared plates are brittle after drying and do not have a certain degree of flexibility. When cutting, the edge will drop powder; when winding , larger cracks

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