Introduce anode materials for lithium batteries: graphite and graphene

Lithium battery cathode materials: Graphite and Graphene Graphite According to media estimates, with the rapid development of electric vehicles this year, the demand for lithium batteries has surged, which will drive the graphite industry down. Although graphite prices and sales have not recovered yet, speculators are still optimistic about the prospect of tightening graphite demand. Graphite is an allotrope of carbon, and the two are closely related. Allotropes are the basic elements of different structures composed of the same element. Graphite is the most stable carbon. Diamond is a metastable allotrope of carbon. Although it is much harder than graphite (the hardest substance in nature), it is not as stable as graphite. The term graphite comes from the Greek graphein, which is resistant to high temperature, corrosion, good electrical conductivity, good thermal conductivity, stable chemical function, and is lighter than aluminum. In addition to cathode data for lithium batteries, high-quality graphite can also be used in fuel power batteries, solar cells, semiconductors, light-emitting diodes, and nuclear reactors. Carbon fiber is a microcrystalline material held together by carbon atoms. Its diameter is only 5-10 meters, about one-tenth the diameter of a human hair, but its strength is very high. Carbon-carbon bonds form bonds along the polymer matrix, just like weaving cloth. Carbon fiber is stronger than steel, but lighter than steel. Carbon fiber is used in golf clubs, bicycle frames, and is expected to replace aluminum in the structural frames of cars and airplanes, such as Boeing 787 and Airbus 350X. Today, graphite only accounts for 5% of global battery demand. There are two sources of graphite: one is natural ore, and the other is a component of coal tar. The graphite material used in lithium batteries is usually a mixture of 55% graphite and 45% low-purity natural graphite. Manufacturers used to prefer the composition of graphite because it is more uniform and purer than natural graphite. However, today, modern chemical methods are used to purify natural graphite so that it can be heat treated to a purity of 99.9%, which is more popular than compositional graphite with 99% purity. Compared with constituent graphite, purified natural flake graphite has higher crystallinity, better electrical conductivity and thermal conductivity. In addition, natural graphite is expected to reduce the processing cost of lithium batteries and enable battery performance to reach or better. Graphite used in lithium batteries is now priced at US$10,000 per ton, while spherical graphite made from natural graphite flakes sells for only US$7,000 per ton (price in 2015). Natural graphite raw materials are even cheaper. It can be predicted that graphite will eventually be replaced by natural graphite. In the future, natural graphite will be cheaper and more environmentally friendly. Graphene is made of natural graphite, which is another blueprint drawn by scientists for us. Graphene Graphene is another allotrope of carbon. It is a hexagonal lattice structure of a thin film. It has only one carbon atom layer thickness, flexibility, transparency, water resistance and strength. It is simpler than diamond and simpler than gold. Conductive, there are three electrons in each carbon atom, and the electrons form a chemical bond with the nearest neighbor atom. Experts believe that graphene is a magical material that can be used in many products, including batteries. When used as the cathode data of lithium batteries, graphene has better electrochemical energy storage than graphite, and the charging speed is 10 times that of graphite, which is expected to realize fast charging. In addition, the load capacity of lithium batteries will also be improved. Regarding conventional graphite cathodes, lithium ions are deposited on the surface to form dendrites. Graphene perfectly solves this problem, allowing lithium ions to pass through the small holes at 10-20nm on the surface and store them well between graphene sheets, thereby achieving fast charging and optimal energy storage. Once put into use, this battery is estimated to be able to store 10 times the energy of ordinary graphite cathodes. Graphene can also be incorporated into vanadium oxide to improve the electrochemical performance of the positive electrode data. Experimental studies have shown that the improved positive data battery can be fully charged within 20 seconds, and after 1000 cycles, the capacity continuity rate can reach 90%. Graphene is also used in the research of supercapacitors and solar cells to increase energy density. Figure 3 shows a common graphene lattice under scanning probe microscopy (SPM). The advantages of graphene have been debated in academia for decades, but have not yet been commercialized. Surprisingly, graphene has been used casually in pencils and other products for centuries. We may want to better understand the mechanism and structure. Statement: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Basic principles of batteries and an overview of industry development