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Graphite and Applications

[Graphite - University of Waterloo]

- Overview

Graphite is a mineral made of stacked carbon atoms and has a hexagonal crystal structure. It is the most stable form of pure carbon under standard conditions. Graphite is very soft, has a low specific gravity, is relatively unreactive, and has high electrical and thermal conductivity. 

Graphite occurs naturally in igneous and metamorphic rocks, and high temperatures and pressures compress carbon into graphite. Graphite can also be synthesized by heating materials with a high carbon content, such as petroleum coke or coal tar pitch. The carbon-rich material is heated to 2,500 to 3,000 degrees Celsius, which is hot enough to "clean" the material of contaminants and cause the carbon to form into hexagonal flakes. 

Graphite is very soft and breaks down into thin, flexible flakes that slide easily over each other, creating a greasy feel. Therefore, graphite is a good "dry" lubricant and can be used in applications where wet lubricants such as lubricants cannot be used. 

Due to its unique composition, graphite has a wide range of uses in metallurgy and manufacturing, making it one of the most popular materials in the modern world. Its purpose is very simple, it is to replace the "lead" in pencils and is used in lubricants, lithium-ion batteries and solar panels. 

Graphite is a critical metal for the economy and national security of the United States. As the world moves towards decarbonization, electric vehicles and clean energy technologies, both artificial and natural graphite will continue to be important minerals or raw materials. While there is currently a huge demand for synthetic graphite in the green economy, demand for natural graphite has increased significantly as more and more industries seek to transition to clean energy.


- Allotropes of Carbon

Because of its valency, carbon is capable of forming many allotropes (structurally different forms of the same element). Well-known forms of carbon include diamond, graphene, and graphite. 

In recent decades, more allotropes have been discovered and studied, including spheres such as buckminsterfullerene and sheets such as graphene. Larger scale carbon structures include nanotubes, nanobuds and nanoribbons. Other unusual forms of carbon exist at very high temperatures or under extreme pressure. 

According to the Samara Carbon Allotrope Database (SACADA), approximately 500 hypothetical three-period allotropes of carbon are currently known.


Allotropes of Carbon_Wikipedia_102423A
[Eight Allotropes of Carbon: Eight allotropes of carbon: (a) diamond, (b) graphite, (c) lonsdaleite, (d) C60 buckminsterfullerene, (e) C540 fullerite (f) C70 fullerene, (g) amorphous carbon, (h) zig-zag single-walled carbon nanotube. Missing: cyclocarbon, carbon nanobuds, schwarzites, glassy carbon, and linear acetylenic carbon (carbyne) - Wikipedia]

- Natural Graphite

Graphite is a naturally occurring form of crystalline carbon, also known as plumbago. Composed of carbon, a natural element found in igneous and metamorphic rocks, it is an extreme mineral that is soft and pliable, but very stable under ordinary atmospheric conditions. 

In its natural form, graphite has a layered structure in which rings of six carbon atoms are arranged in widely spaced horizontal sheets. 

Natural graphite, as the name suggests, occurs naturally and comes in three forms: amorphous graphite, flake graphite, and crystal vein graphite.

All three forms have unique properties that make them suitable for certain applications, which is why natural graphite can be found in electronics, aerospace, hot metal processing, friction, lubricants and many other modern manufacturing industries.


- Graphite Anodes

Graphite anodes remain the mainstream choice for global downstream battery manufacturers. But with prospects bleak, competition between natural and synthetic graphite is intensifying. 

Graphite anode is a corrosion-resistant material used as a secondary anode to low-solubility anode materials. Graphite anodes are used in soil, flowing seawater and marine mud. In fact, they are not harmed by chlorine. 

Graphite anodes are usually impregnated with a sealant to prevent mechanical damage due to gas in the pores, and graphite is also brittle.

In the short term, synthetic graphite anode materials will continue to occupy the largest market share in the lithium-ion battery industry, but due to their respective advantages in battery manufacturing, the expected growth in consumption of natural anode materials has been attracting attention.


- Synthetic Graphite

Synthetic graphite is man-made through a production process. Synthetic graphite is produced from petroleum coke or coal tar.

Synthetic graphite is made from non-graphitic carbon or amorphous carbon materials through graphitization or high temperature treatment. It is used in many manufacturing industries such as conductive fillers, rubber and plastic compounds, drilling applications, coatings, fuel cell bipolar sites, corrosion products and electrolysis processes, among others. 

In the United States, the primary raw materials used to make artificial graphite are calcined petroleum coke and coal tar pitch, both of which are composed of highly graphitized carbon.


- Potential Applications

Graphite is the crystalline form of the element carbon. It consists of stacked graphene layers. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed in large quantities for pencils, lubricants and electrodes. Under high pressure and heat, it transforms into diamond. It is a good (but not excellent) conductor of heat and electricity.

Graphite’s key properties make it an important element of clean technology: 

  • High thermal conductivity
  • High conductivity
  • high energy density
  • High temperature resistance 
  • Long life cycle 
  • Relatively low cost - natural graphite

Graphite is used in many applications that require high temperatures and require a material that will not melt or decompose.

Graphite is a non-renewable carbon that is used in renewable energy technologies. It's resistant to extreme heat, so it's used in:

  • Solar panels: Used in crucibles and molds to cast silicon
  • Batteries: Used to store energy generated by solar and wind farms
  • Lithium-ion batteries: About half of a lithium-ion battery is made of graphite.

Graphite is also used to:

  • Reduce the cost of renewable hydrogen fuel
  • Make hydrogen fuel stations more common

The World Bank forecasts that low-carbon energy technologies will require 4.5Mt of graphite per year by 2050.


- Environmental Impacts

Graphite processing is a long and complex process that usually takes several weeks. The process includes: Mining, Concentration, Spheronisation, Purification, Carbon coating, Chemical concentration. 

Graphite processing can have several environmental impacts, including:

  • Mining: Can lead to deforestation, habitat degradation, and water contamination.
  • Purification: Can be dangerous to surrounding ecosystems if runoff and wastewater are not properly controlled.
  • Production: Synthetic graphite emits more greenhouse gases than mining natural graphite. The production of synthetic graphite anodes can be four times more carbon-intensive than natural graphite anode production.
  • Energy consumption: Energy consumption and waste acid generation are the main environmental drivers.


- Natural Vs Synthetic Graphite

How to identify natural and synthetic graphite?

  • Color Difference – Natural graphite has a more opaque quality in its dark gray to black color, while synthetic graphite, while similar in hue, is flatter in color. 
  • Graphite Density – Natural graphite flakes are rougher than synthetic graphite because it contains more impurities. The density of synthetic graphite is higher than that of natural graphite, and its thermal conductivity is about 700-1500w, while natural graphite is about 300-700w. 
  • Price Difference – Synthetic graphite is much more expensive than natural graphite due to the rather energy-intensive manufacturing process. The cost difference can be double or even triple the standard price of natural graphite.


- Is Synthetic Graphite Better Than Natural Graphite?

The main difference between the two types of graphite is the manufacturing process. Synthetic graphite is currently in demand in the battery industry because of its fast charge turnaround and long service life. 

Today, synthetic graphite accounts for more than 50% of the anode market. The industry is shifting towards natural graphite due to its cost advantages and lower environmental impact. 

The only emissions from natural graphite are those produced during the mining process, while synthetic graphite produces more than 3 times the amount of carbon dioxide and other harmful emissions due to the energy-intensive and costly production process. Synthetic graphite, on the other hand, is less affected by problems in mining or mine sites that can disrupt production.

Natural graphite and synthetic graphite are used in a mixture whenever possible, and both forms of graphite have a place in the industrial market. Batteries can use both types of graphite materials, so the demand for graphite is expected to increase significantly, with demand for each type varying as the industry develops.


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