Graphite powder can be divided into natural graphite powder and artificial graphite powder. Both have similar structures and similar physical and chemical properties, but their uses are quite different. In many studies, some researchers did not notice the difference between the two and call it graphite in general. The result of this conflation of the two has caused a lot of misleading and even decision-making errors, resulting in a great waste of resources and economic losses. From the perspective of the structure, composition and performance of natural graphite and artificial graphite, this article will talk about the difference and correlation between the two.
Natural graphite powder is formed by the transformation of carbon-rich organic matter under the long-term action of high temperature and high pressure geological environment. It is the crystallization of nature. The process characteristics of natural graphite mainly depend on its crystal form. Minerals with different crystalline forms have different industrial values and uses. There are many types of natural graphite powder. According to different crystalline forms, the industry divides natural graphite into dense crystalline graphite, flake graphite and cryptocrystalline graphite. There are two main categories of flake graphite and cryptocrystalline graphite in my country.
Artificial graphite is similar to polycrystals in crystallography. There are many kinds of artificial graphite, and the production process is very different. Broadly speaking, all graphite materials obtained through organic carbonization and graphitization high temperature treatment can be collectively called artificial graphite, such as carbon (graphite) fiber, pyrolytic carbon (graphite), foam graphite, etc. In the narrow sense, artificial graphite usually refers to the use of carbonaceous raw materials (petroleum coke, pitch coke, etc.) with low impurity content as aggregates, coal pitch, etc. as binders, after batching, kneading, molding, and carbonization (industrially called It is a block solid material obtained by baking) and graphitization, such as graphite electrode, hot isostatic pressing graphite, etc. Today we will learn about the use and production process of artificial graphite.
Lithium battery anode material is one of the main materials of lithium-ion batteries, which plays a key role in energy density and cycle stability. In recent years, with the continuous development of science and technology, new negative electrode materials have emerged in endlessly, including graphene, carbon nanotubes, silicon-based materials, tin-based materials, tungsten-based materials, etc., but they have limited large quantities due to various problems. Production, at present, graphite-based carbon materials have always been in the mainstream position of market-oriented anode materials.
Compared with natural graphite, artificial graphite has larger interlayer spacing, lower graphitization degree (≤93%), lower crystallinity, and some disordered layer structure. In addition, the surface of artificial graphite is not smooth, porous, and has a large specific surface. It is easy to decompose and react with the electrolyte, so its initial efficiency and specific capacity (≤350mAh/g) are low.
In order to solve the problems of artificial graphite used in lithium batteries, researchers have improved the production process. Such a product is modified artificial graphite, which has the characteristics of high compaction, long cycle time, and low expansion rate. Using it as the negative electrode of a lithium battery can improve its conversion with electrolyte, reduce the swelling of the pole shoe, and have a positive impact on the overall life of the replacement battery. The production process is to replace artificial graphite with pitch, etc. and carbonize. An amorphous carbon-doped layer is formed on the surface of the artificial graphite. The overlapping layer can prevent the co-embedding of organic solvents and prevent the expansion and contraction of graphite. The surface layer is displaced, so that the lithium battery is interrupted to maintain high capacity, low potential and compatibility with solvents.
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