Needle coke is a high-performance carbon material with a metallic luster and silver-gray color. Its surface texture is fibrous or needle-like, with a slippery feel. It contains small, oval-shaped pores inside. Needle coke consists of large molecular polycyclic aromatic hydrocarbons with flat aromatic layers. It has a graphite-like microcrystalline structure with high unit orientation. The microscopic structure follows the Franklin model and is a typical graphitizable carbon. It is an ideal material for preparing porous carbon. When heated above 2000°C, it forms graphite-like layered structures.
Due to its excellent electrical conductivity, thermal conductivity, low thermal expansion, and thermal shock resistance, needle coke is widely used in steelmaking graphite electrodes, aerospace, and other fields. It has become a hot research topic in the material science field worldwide in recent years.
Needle cokes can be classified into coal-based and petroleum-based types, depending on the raw material source. Coal-based needle coke is produced by high-temperature carbonization of coal tar, coal tar pitch, or flash distillation oil.
Petroleum-based needle coke is produced by high-temperature carbonization of ethylene tar, vacuum and thermal cracking residual oil, or catalytic cracking oil slurry. Due to its low sulfur, low ash, low metal content, and easy graphitization, it is currently the main raw material for artificial graphite. However, its production cost is high, and it has strict raw material requirements.
Preparation of Needle Coke
Needle coke is produced through liquid-phase carbonization, gradually pyrolyzing and polymerizing raw materials to form mesophase spheres, which then grow, merge, orient, and finally carbonize into a fibrous needle-like structure. The production process includes raw material pretreatment, delayed coking, and calcination.
Delayed coking, the main stage of coking, involves distillation and carbonization, producing refined pitch and coke. Calcination removes volatile substances and moisture to improve true density.
Coal-based needle cokes requires stricter pretreatment than petroleum-based needle coke, but both types are similar in structure and applications. Petroleum-based needle coke, however, has lower production costs and higher market capacity.
Graphitization of needle coke involves processes like schiacciamento, grinding, modifica della superficie, heat treatment, and surface modification, similar to coal graphitization. Needle coke, as a soft carbon with high electrical conductivity and low impurities, is commonly used in lithium-ion batteries. However, it has a low theoretical capacity, and its use in batteries requires high-temperature graphitization to become artificial graphite.
Research on needle coke-based anode materials for lithium-ion batteries focuses on modification and composite techniques to improve capacity and reduce costs, addressing growing demand for high energy density, fast-charging, and safe batteries.
Application of Needle Coke in Different Fields
Needle coke has three main uses: high-power electrodes, special carbon materials, and lithium-ion battery anodes. High-power graphite electrodes made from needle coke are used in electric arc furnaces for steelmaking. Electric arc furnace steelmaking has advantages like low pollution and low energy consumption. High-power graphite electrodes made from needle coke have low thermal expansion, high electrical conductivity, and high mechanical strength.
These electrodes efficiently heat and melt metals in electric arc furnaces. As an anode material, needle coke, as soft carbon, is easy to graphitize and low-cost. After high-temperature heat treatment, it forms artificial graphite with good cycling stability and high specific capacity.
Application of Acicular Coke in Graphite Electrodes
Graphite electrodes are mainly used in electric arc furnaces, submerged arc furnaces, and resistance furnaces. Electric arc furnace steelmaking is more environmentally friendly than blast furnace steelmaking, leading to favorable policies in many countries. The growing scale of electric arc furnace steelmaking has driven up the demand for graphite electrodes. Currently, electric arc furnace steelmaking is moving towards larger and ultra-high-power furnaces. As a result, the requirements for graphite electrodes are becoming more stringent. Since the maximum allowable current for electric arc furnace graphite electrodes is positively correlated with their diameter, developing large-diameter graphite electrodes is essential. Producing large-diameter graphite electrodes requires high-quality needle coke.
Application of Acicular Coke in Negative Electrode of Alkali Metal Ion Battery
Currently, alkali metal-ion batteries mainly include lithium-ion, sodium-ion, and potassium-ion batteries. Lithium-ion batteries are widely used in daily life. Sodium-ion and potassium-ion batteries have attracted special attention as alternative energy storage systems.
Alkali metal-ion batteries mainly consist of cathode, anode, electrolyte, separator, and battery casing. The anode material, as a key component, greatly affects the overall performance of the battery. For lithium-ion batteries, commercial anode materials include artificial graphite and natural graphite, with artificial graphite accounting for 80%. Artificial graphite can be divided into oil-based coke and coal-based coke. Oil-based coke can be further divided into petroleum coke and needle coke. Anode materials made from needle coke have good chimico stability, high capacity, and excellent conductivity. They are used to produce high-press density, high-energy-density electrode materials.
Application of Needle Coke in Supercapacitors
In recent years, supercapacitors, as energy storage devices combining the characteristics of both capacitors and batteries, have gained attention. They offer higher energy density than traditional capacitors and higher power density than secondary batteries, with a cycle life more than an order of magnitude longer than that of secondary batteries. Supercapacitors can be used for energy recovery and release during the startup, acceleration, and braking of various vehicles. In most cases, supercapacitors are combined with secondary batteries or fuel cells with high energy density to form hybrid power systems. This combination meets the requirements of new energy vehicles for high charging rates, high specific capacity, and high energy recovery efficiency.
Needle Coke for Graphene Preparation
Graphene has excellent optical, electrical, and mechanical properties, with broad applications in materials science, energy, and biomedicine. The main preparation methods for graphene include mechanical exfoliation, epitaxial growth on silicon carbide, solvent exfoliation, chemical exfoliation (oxidation/reduction), and chemical vapor deposition (CVD). However, most of these methods, such as mechanical exfoliation and solvent exfoliation, are typically used in laboratories. The CVD method, while effective, has a relatively complex process and higher costs.
Needle Coke for Photovoltaic Industry
Dye-sensitized solar cells (DSSCs) are emerging as a new photovoltaic device and are becoming a research hotspot. Compared to traditional solar cells, DSSCs have advantages such as longer lifespan (15–20 years), easy large-scale industrial production, short energy recovery cycle, lower production cost (only 1/10 to 1/5 of silicon solar cells), and non-toxic, pollution-free production processes. In recent years, researchers have found that needle coke has high conductivity, heat resistance, corrosion resistance, and electrocatalytic activity for triiodide. Additionally, its low cost makes it a promising electrode material for dye-sensitized solar cells.
Conclusione
Needle coke, a highly ordered carbon material, is vital for high-performance lithium-ion batteries due to its excellent conductivity and low impurity. Combining grinding modification optimizes its particle structure, enhancing capacity and reducing energy-intensive processing, aligning with sustainable, high-energy battery demands.
Polvere epica, oltre 20 anni di esperienza lavorativa nel settore delle polveri ultrafini. Promuovere attivamente lo sviluppo futuro delle polveri ultrafini, concentrandosi sul processo di frantumazione, macinazione, classificazione e modifica delle polveri ultrafini. Contattaci per una consulenza gratuita e soluzioni personalizzate! Il nostro team di esperti è impegnato a fornire prodotti e servizi di alta qualità per massimizzare il valore della tua lavorazione delle polveri. Epic Powder: il tuo esperto di fiducia nella lavorazione delle polveri!