What are the technical indicators of graphite anode materials for lithium batteries? 

Lithium battery, as a booming emerging industry, has great development potential and prospects. In order to promote the healthy and orderly development of the industry, relevant industry standards have been continuously formulated and issued. Among them, the relevant technical standards for lithium battery anode materials have also been clearly specified. What are the specific indicators?

1. Anode materials crystal structure

Different crystal structure and chemical composition will cause the physical and chemical properties of the powder to be different, which will affect the application of the powder. The commonly used anode material graphite has two crystal structures, one is hexagonal phase, the other is rhombic phase. Degree of the order of the crystal structure is related to degree of the graphitization. The greater the degree of graphitization, the easier the carbon materials are to be graphitized, and the higher the degree of order of the crystal structure. The higher the graphitization degree is, the less the corresponding lattice defects are, and the less the electron migration resistance is, and the dynamic performance of the battery will be improved.

2. Anode materials particle size distribution 

The particle size distribution of anode materials will directly affect the battery pulping process and volume energy density. At the same volume fraction, the larger the particle size and the wider the particle size distribution of the material, the smaller the viscosity of the slurry, which is conducive to improving the solid content and reducing the coating difficulty. In addition, when the particle size distribution of the material is wide, the small particles in the system can be filled in the gaps of the large particles, which helps to increase the compaction density of the electrode piece and improve the volume energy density of the battery.

3. Anode materials density

Density refers to the mass per unit volume of materials in an absolute dense state. Powder materials are generally porous. According to whether these pore volumes are included, they can be divided into true density, effective density and apparent density, and the apparent density can be divided into compaction density and vibrating density. In practical applications, manufacturers are more concerned about the apparent density of materials. For the anode materials , the density will directly affect the volume energy density of the battery. For the same material, the higher the compaction density is, the higher the volumetric energy density is. Therefore, the lower limit values of various densities are required in the standard.

4. Anode materialspecific surface area 

The specific surface area of anode material has great influence on the dynamic performance of battery and solid electrolyte film formation. If the specific surface area of graphite is too large, the capacity loss is too large for the first time, and more adhesives are added, resulting in increased internal resistance. The specific surface area of graphite is related to the shape and surface structure of graphite particles. For example, artificial graphite has a special microporoustructure, large specific surface area, active sites and reaction area, which improves the utilization rate of active materials and shows high capacity and high amplification performance. It can be said that too large or too small specific surface area of graphite particles is not conducive to the reversible deinking of lithium ions, and only appropriate specific surface area can limit the reversible deinking of lithium ions.

5. Requirements of anode materials on pH and moisture

The pH value and water content of the anode material have important influence on the stability and pulping process of the material. The Karl Fischer Coulomb titrimeter can be used to determine the trace amount of water contained in powder materials. The pH. The sample can be mixed with distilled water and measured with a pH meter.

6. Element content of anode materials

Graphite is mainly composed of fixed carbon, ash and volatile matter. Fixed carbon is a component with real electrochemical activity. The standard hastrict requirements on fixed carbon content, which shall be at least greater than 99.5%. In addition to the fixed carbon and lithium main elements, some impurity elements will be introduced into the anode materials during coating, doping and other modification processes, which will also seriously affect the electrochemical performance of battery and need to be strictly controlled. Moreover, some anode materials contain limited elements, such as cadmium, lead, mercury, hexavalent chromium and their compounds, which are harmful to animals, plants and the environment. Therefore, there are strict restrictions on such substances in the standard.

7. First reversible specific capacity and first efficiency of anode materials

Anode material first reversible specific capacity refers to the first week's lithium removal capacity, while the first efficiency refers to the ratio of the lithium removal capacity in the first week to the lithium insertion capacity, which can reflect the electrochemical performance of the electrode material to a large extent. Moreover, the reversible specific capacity of battery can reflect material stable capacity in the subsequent cycle to a certain extent, which also has important practical significance. The anode materials indexes and performance in graphite market, welcome your further contact.