Application of flake graphite in lithium battery
Flake graphite is a non-metallic mineral with complete crystals, thin sheet and good toughness, excellent physical and chemical properties, and unique physical and chemical properties such as high temperature resistance, oxidation resistance, corrosion resistance, thermal conductivity and electrical conductivity.
Graphite is divided into two types, one is natural graphite; the other is artificial graphite. Although with the improvement of manufacturing technology, in many cases the function of artificial graphite is no less inferior to natural graphite, in some areas, natural graphite has always maintained a unique advantage.
Among natural graphite resources, flake graphite (crystalline graphite) has low reserves and high value, and has good electrical and thermal conductivity, lubricity and oxidation resistance. It is widely used in metallurgy, machinery, chemical, refractory materials, aerospace and other industries. It is one of the indispensable non-metallic materials for the development of high and new technology today.
The flake graphite structure is in the form of flakes and good surface properties, which makes it have good natural floatability and is one of the best floatable minerals in nature.
According to the size of the scale, the flake graphite can be divided into large scale graphite (particle size of 0.3 mm, 0.18 mm, 0.15 mm) and fine flake graphite (particle size less than 0.15 mm). However, in comparison, large scale graphite has advantages in the market and application, and the price of large scale graphite of the same grade is far superior to that of fine scale graphite.
Next, let's take a look at the application of the next scale graphite in lithium batteries.
The conductivity of flake graphite is 100 times higher than that of general non-metallic minerals, and it is a conductive material with a wide range of applications. Among them, lithium ion batteries work by using the conductivity of flake graphite powder.In lithium ion battery materials, the anode material is the key to determining battery performance.
As a high crystallinity graphite material, the particle size of flake graphite directly affects the ratio of the specific surface area of the electrode and the edge carbon atoms, which has a great influence on the irreversible specific capacity at the time of first charge.Therefore, flake graphite plays a vital role in the battery.
First, flake graphite has many advantages such as high electronic conductivity, large lithium ion diffusion coefficient, high embedding capacity and low embedding potential, so flake graphite is one of the most important materials for lithium batteries.
Graphite powder is soft, black and gray; it has a greasy feel and can contaminate paper. The hardness is 1-2, and the hardness can be increased to 3 to 5 along with the increase of impurities in the vertical direction.
The specific gravity is 1.9 to 2.3. Under the condition of insulating oxygen, its melting point is above 3000 °C, which is one of the most temperature-resistant minerals.
The chemical properties of graphite powder at normal temperature are relatively stable, insoluble in water, dilute acid, dilute alkali and organic solvent; the material has high temperature resistance and can be used as refractory material, conductive material and wear-resistant lubricating material.
Second, the flake graphite can make the lithium battery voltage stable, reduce the internal resistance in the lithium battery, and can make the battery storage time long. Increase battery utilization time.
Third, the scale graphite can reduce the amount of scale graphite powder in the lithium battery, so that the battery cost is greatly reduced.The main component of graphite emulsion is graphite (fine powder graphite). Because it is in a milky state, it is often called graphite emulsion. Strictly speaking, this kind of product should be called graphite colloid.Divided into solvent-based graphite emulsion and water-based graphite emulsion.Expandable graphite has a hexagonal mesh planar layered structure composed of carbon elements. The carbon atoms in the plane of the layer are bonded by strong covalent bonds, and the layers are bonded by van der Waals force, the bonding is very weak, and the interlayer distance is large.Therefore, under appropriate conditions, various chemicals such as acids, alkali metals, and salts can be inserted between the graphite layers and combined with carbon atoms to form a new chemical phase.