Graphite Anode Materials Processing Technology

Carbon material is currently the main negative electrode material used in lithium-ion batteries, include graphite, needle coke, petroleum coke, graphene, etc.Its performance affects the quality, cost and safety of lithium-ion batteries.The factors that determine the performance of anode materials are not only the raw materials and the process formula, but also the stable and energy-efficient carbon graphite grinding, spheroidizing, shaping and grading technologies.

To follow the trend of negative electrode, we developed CUM Impact Mill and designed a process to realize the surface fixing with mechanical force. This system is designed to improve the shaping efficiency and performance, and meet the requirement of surface coating. CUM Impact Mills are mainly used for shaping of artificial graphite and natural graphite, grinded by CSM Air Classifier Mill. The surface of the particle is fixed under the long time, low speed mechanical force. The surface area is decreased considerably but the particle size changes slightly. This brings higher product output, narrow particle size distribution and better coating performance.

Mechanical Grinding and Shaping of Graphite Anode Materials

Ultrafine grinding equipment with built-in grinder and classifier, the material is fed into the grinding disc to be collided repeatedly and milled by grinding hammers around the disc, then enters the classification area, through the centrifugal classification of the classifying wheel, fine powder is collected, coarse particles fall back to the grinding area to continue grinding and shaping.

The complete set of equipment is mainly composed of shaping machine, external classifier, cyclone collector, bag filter and draft fan, etc. After shaping, most of the finished product will be collected from the bottom outlet of classifier, and a small amount of micro powder will be collected by the bag filter. Draft fan provides necessary negative pressure for the whole system, and the system runs under negative pressure without dust flying.

The system has a three-way pipeline at the inlet of the classifier, which can be designed as the entrance into the shaping machine or directly into the classifier, depending on the process needs.

Raw Coke Grinding Process with Impact Mill

The body cavity is cylindrical, the upper part is ultra-micro classifier, the lower part is ultra-micro mill. The grinding chamber is composed of grinding disc and grinding block which are used to grind the material into ultrafine powder; The classification chamber is composed of a classification wheel, which can divide the fine powder into two specifications of particle size as qualified powder and unqualified powder. The qualified powder is discharged through the discharge pipe and collected by the cyclone collector. The unqualified powder falls back to the grinding chamber along the inner wall of the shunt ring and continue grinding until reaching the standard.

The grinding disc and the classifying wheel are driven by their respective driving devices. The rotating speed of the classifying wheel is adjustable to adjust the particle size of the product. Screw feeding device in the inner wall of the mill host, which is used to feed the material evenly into the grinding chamber, can control the feeding quantity by adjusting rotating speed.

The complete set of equipment is mainly composed of feeding screw, mill host, cyclone collector, bag filter and draft fan. The crushed raw materials less than 5mm are fed into ultrafine Classifier Mill to be milled. Most of the milled finished products are collected by cyclone collector, a small amount of micro powder is collected by bag filter, and clean air is discharged through draft fan. Draft fan provides necessary negative pressure for the whole system, and the system runs under negative pressure without dust flying.

Cooked Coke Grinding Process by Ring Roller Mill

The raw material is fed into the grinding system for ultrafine grinding by quantitative feeding. Roller is divided into upper and lower layers, in the process of revolution and rotation of each layer of roller, a strong centrifugal force is produced, a strong rolling grinding effect between the roller and ring will form. Driven by centrifugal force and roller rotation field, the material to be milled enters the grinding zone between roller and ring, and then is milled under the action of strong squeezing pressure and grinding force. The milled material falls into the discharge tray and then is driven by the updraft along the shunt ring up to the classifying area for classification, qualified fine powder will go through the classifying wheel into the collection system, coarse powder falls along the inner wall of shunt ring back to grinding chamber for re-grinding.

Bitumen grinding process by Jet Mill

Jet Mill, bag filter, draft fan constitute a set of grinding system. Dry compressed air is filtered and ejected through the high-speed Laval nozzle into the grinding chamber. The material is collided, sheared and robbed repeatedly at the joint of several high-pressure jet air flow and finally pulverized, After that, the milled material moves up to the classifying zone with the updraft under the action of a draft fan, then will be classified into different size under the centrifugal force produced by classifying turbine at high rotative speed. The qualified fine particles enter classifying wheel and then collected by cyclone collector and bag filter, and the coarse particles fall back to the grinding zone for further grinding.

Preparation of anode raw materials from natural flake graphite

The raw material is grinded to d50: 21-23μm by the MJW700 Air Classifier Mill. The second step is to get spherical particle with size d50:19-20μm, by using MJW500 Air Classifier Mill and HTS Air Classifier. Spherical particle is transferred to MJW400 Air Classifier Mill and HTS Air Classifier by pneumatic conveying system, to optimize the particle appearance. By this step, the particle is in potato shape and particle size is D50: 16-17μm. Then it comes to purification. The carbon content rises to 99.95%-99.99% during this process. By following the requirement from customers, the particle is shaped, classified, coated, carbonized and packed.

Grinding and Shaping process of artificial graphite (coke) for lithium anode

The raw material is milled into powder with particle size of 6-18um (D50) by ultra-fine grinder, and then enters shaping classification system, where the particles are gradually rounded into spherical shape, and particle size meets specific index requirements (D10, D50, D90 and tap density, etc.). Similarly, the system is equipped with classifier, which can separate ultrafine particles generated during shaping in time.

Graphite Grinding and Shaping System

MJW-L Air Classifier Mill (Vertical type)

Classic internal classifying mill is widely used, relatively cost-effective. The lower part is ultrafine mill and the upper part is ultrafine classifier.

Material is fed into grinding disc’s outer edge part by spiral feeder, then driven by hammers on the grinding disc to get acceleration, meanwhile material collide with each other to be ground in the grinding area between grinding hammers and gear ring. Then the ground material is driven by rising air flow into classification area. Qualified fine powder is separated by classifying wheel, and coarse powders fall into grinding area along inside of split ring for regrinding.

MJW-L Air Classifier Mill (Vertical and heightened type)

Material is fed into center of grinding disc by spiral feeder, then driven by hammers uniformly distributed on grinding disc to get a certain outward acceleration. Meanwhile material collide with each other in the grinding area between grinding disc and ring gear to be ground, then the ground powder is driven by rising air flow into classification area. Qualified fine powder is separated by classifying wheel, coarser particles fall back to grinding area for regrinding.

Features:

The kinetic energy of material is relatively larger, more finer powder can be obtained;
The rising area is longer, water evaporation effect is better;
Dmax is easy to control.

Pin Mill Deagglomeration System

The complete system consists of pin mill, two stage classifiers, bag filter and fan. The material to be deagglomerated is evenly fed into pin mill by feeding system. After being fully deagglomerated by the multi-layer pins of the mill, material enters classification area. The first-stage classifier is responsible for removing the large particles to meet the requirements of D90 index, and the large particles can be returned to pin mill to continue deagglomeration. The second-stage classifier is responsible for removing fine powder and meeting the requirements of D10 index. Pin Mill grinding meets the requirements of D50 index.

The system has three outlets, coarse particles are discharged from the outlet of first-stage classifier, final products are discharged from the outlet of second-stage classifier, fine powder is discharged from the outlet of bag filter.

Pin Mill working principle

The closed-loop inert gas protection system, a closed-loop ultra-fine grinding and classifying system using inert gas circulation protection, is developed by our company for the grinding and classifying requirements of special materials such as inflammable, explosive, and easily oxidized materials. Due to the high cost of inert gas, a closed system is adopted, and a strictly airtight separation device is adopted at the inlet and outlet.

Working principle: Material is fed into grinding chamber by feeding device, the material also spin at a accelerated rate under the action of grinding disc’s high speed rotation, and moves to the outer direction under centrifugal force. In this process, material is ground by strong collision among the pins of rotary disc and static dis. Because there are 3 layers of pins’ ring of both rotary disc and static disc, so that the grinding effect of material is more sufficient, the fineness of product is good and uniform.

Features: small particle surface damage, suitable for deagglomeration.

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Factory Address：

NO. 369, Road S209, Huanxiu , Qingdao City, China