Double Planetary Agitator | The Slurry Process That Determines The Upper Limit Of Electrode Performance For Lithium Batteries

Lithium-ion battery manufacturing process is complex, many processes, in accordance with the process is generally divided into three sections, one is pole film production, the second is cell production, the third is battery assembly. Among them, the production of pole pieces is the basis of the entire lithium battery production process, which includes slurry (mixing), coating, rolling, slitting, filmmaking, die-cutting and other processes. As the first process of lithium battery electrode production, slurry preparation is the main factor that determines the quality of positive and negative electrode sheet, and is the core of electrode sheet production.

Electrode sizing requirements

Electrode slurry is generally a solid-liquid dispersion system composed of active substances (negative extremely graphite, positive extremely ternary materials, lithium iron phosphate, lithium cobalt oxide, etc.), conductive carbon black, dispersing agents, adhesives, additives and other components in accordance with a certain proportion, the formula of these materials determines the upper limit of the battery performance can be achieved, and the lower limit of its performance is affected by the process.

The requirements for the pole-sheet slurry process should meet:

1. In order for the electrolyte to be able to access all the active material particles and ensure that the battery has a high current density, the active material particles should be evenly dispersed and not agglomerated.

(2) Conductive particles should form a full range of conductive networks to maximize the electronic channel between the active substance and the collector.

3. The active substance, conductive agent, solvent has no adhesion to the metal electrode, and can not be directly coated on the metal foil to make a pole sheet, so it is necessary to use a binder to bond various particles together to form a slurry with stability and adhesion.

To sum up the above points, that is, the lithium ion battery slurry requires each component to have good uniform dispersion and stability, and the dispersion is evaluated by the solid amount, viscosity and particle size distribution of the slurry; The stability is evaluated by the 24 hours change of the solid volume of the paste and the 24 hours change of the viscosity of the paste, both of which put forward high requirements on the slurry slurry process.

Double planetary mixer slurry dispersion

At present, the mainstream homogenizing equipment used by lithium-ion battery manufacturers is mostly double-planet mixers, also known as PD mixers. Named for its working characteristics similar to those of a planet orbiting a star, it consists of a low-speed mixing component and a high-speed dispersing component composed of two folding frame mixing paddles.

Driven by planetary gear, the stirring paddle rotates while rotating, forming a turbulent flow field that does not change with the rotation of the agitator. The establishment of turbulent flow field can quickly realize the uniform mixing of materials without dead corners. The high-speed dispersion components are generally toothing dispersion disks or high-speed dispersion emulsifiers, which orbit together with the planetary frame and rotate at a high speed, forming a strong shear stress field in a local scope, rapidly breaking up the secondary aggregates, reducing their granularity and promoting their rapid dissolution.