Method for recovering battery negative material

Abstract

This invention relates to a recovering method for negative materials of cells including recovering waste negative pole plates or slurry preparing them, especially crushing the plates into slices by a miller with a rotating knife and putting the mixture containing graphite on the top of a vibration screen to vibrate them to get graphite particles or drying the slurry under low temperature to get graphite blocks then to be crushed to particles via a pre-crushing procedure, then, grinding the particles with a ball mill to get final powder to be confected to slurry added with CMC to adjust the viscosity and meet the requirement, which can utilize resources repeatedly and save manufacture cost.

Description

technical field [0001] The present invention relates to a method for recycling negative electrode materials of secondary batteries, in particular to a method for recycling negative electrode materials of lithium-ion batteries that enables resources to be reused, saves battery manufacturing costs, and at the same time greatly reduces negative impacts on the environment . Background technique [0002] Today, with the rapid development of the information age, the demand for lithium-ion batteries is increasing, and there are more and more manufacturers producing lithium-ion batteries. At present, the vast majority of lithium-ion battery manufacturers use graphite as the negative electrode active material of the battery, but some manufacturers use natural graphite, some use artificial graphite, and some manufacturers use mesocarbon microspheres and so on. And most of these manufacturers adopt water system method to prepare negative electrode slurry. In the production process of...

AI Technical Summary

Problems solved by technology

A very big disadvantage of this recycling method is that the viscosity of the slurry is very unstable, which leads to a high defect rate during coating (the weight per unit area of ​​the pole piece is too widely distributed)

And the viscosity instability of reclaiming slurry mainly has two reasons, one, be because the viscosity of sodium carboxymethylcellulose (hereinafter referred to as CMC) aqueous solution increases with time and the property (as accompanying drawing 1) that reduces, decides, in Settling shelving step, the time of shelving is relatively long, like this, the viscosity of slurry drops more severe, two, because in the process that active material on pole piece is washed down with deionized water, the solid content of the slurry gained after washing ( The content of solid matter) is small and cannot meet the requirements of use. This requires sedimentation and then filtering the supernatant to increase the solid content, but the supernatant contains dissolved CMC, which leads to the loss of CMC and finally reduces the viscosity of the slurry.

On the other hand, another disadvantage of this traditional recycling method is that the defective pole pieces are bonded by the van der Waals force of organic polymers such as CMC and SBR (styrene-butadiene latex) through the coating and drying process. Together, when the negative electrode material is washed directly with water, the bonding between the graphite particles cannot be completely broken, resulting in a lot of large particles in the configured slurry. In this way, during the coating process, the large graphite particles are blocked by the knife Between the material roller and the material roller, longitudinal scratches are formed on the surface of the pole piece, and the thickness of the scratches is too small. Finally, the battery will make the local positive and negative electrodes out of balance, which is likely to cause safety problems.

Some manufacturers also use colloid mills to refine the recovered slurry in an attempt to break the physical bond between particles. This method of refining is indeed conducive to breaking the physical bond between graphite particles and particles, but This strong running-in process can easily increase the temperature of the slurry and break the molecules of CMC, and finally make the viscosity of the recovered slurry drop significantly, which is not conducive to normal mass production

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