Gap between manufacturing technology of graphite products in China and abroad
（1） Special carbon materials the development of China's special carbon industry is relatively late. From the beginning of copying foreign products, to now there are products and technologies that meet our national conditions. After decades of continuous learning and exploration, our country's special carbon industry has gradually started to move onto the right track. Special carbon products are generally divided into cold molding graphite, vibration molding graphite, hot extrusion graphite, isostatic pressing graphite and so on according to their different molding processes. In terms of molding and vibration molding, our technology can compete with the most advanced technology abroad. The most representative enterprises in molding are. Some products have a high reputation in the world, and these enterprises are also growing. They are equipped with 2000 tons of molding machines, and the quality of finished products can reach 200 kg. Representative enterprises in vibration molding include Shandong Zibo continental carbon, Datong new town and Inner Mongolia Qingshan special carbon, among which GSK products are highly known internationally. These enterprises have mature production technology and stable product performance. Some products have received great attention as substitutes for isostatic pressing products, such as graphite for EDM, nonferrous metal crystallizers and some mechanical seals.
However, in hot extrusion and isostatic pressing, there are still some gaps between us and foreign advanced technologies. In terms of extrusion molding, Fangda carbon and Sinosteel Jilin Carbon have made remarkable achievements, and their products can represent the advanced level of China. However, compared with the extrusion products of Sigri in Germany and UCAR in the United States, the size of domestic products is relatively small, and the maximum size is 500 mm × 450 mm × 3000mm, the maximum size of sigli's products can reach 670mm × 450 mm × 3000mm。 In addition, the isotropy and mechanical strength of domestic products need to be improved.
Isostatic pressing graphite is a fine product among graphite materials, which has a series of excellent properties. Therefore, it will be closely related to high-tech and national defense cutting-edge technologies, and become one of the most valuable new materials in the 21st century. Although China has its own isostatic pressing graphite production enterprises, most of the isostatic pressing graphite products have low performance, single variety, and large-scale high-performance isostatic pressing graphite can not be produced. The development of isostatic pressing graphite materials abroad has a long history. Among them, the isostatic pressing graphite produced by Japan, the United States, Germany and France has nearly 100 models and self-made series, providing a large number of new types of graphite products for the development of other high-tech, precision and advanced fields. Relatively speaking, the gap between domestic and foreign isostatic pressing graphite materials is mainly reflected in the following points:
1. Raw materials and formulas raw materials and formulas are different, and the internal arrangement structure and element composition of the product are different, so the external physical and chemical properties are also very different. The raw materials for producing isostatic pressure graphite in China are basically the same as those used for other graphite products, namely petroleum coke and asphalt coke. The specific production raw materials and formulas of foreign countries have always been confidential to China. After acquiring Shanxi Quanhai carbon company in 2007, sigli established sigli Quanhai carbon (Shanxi) Co., Ltd. As far as the current situation is concerned, sigli's production base in China only uses the two processes of roasting and graphitization for production. Roland France has invested in the construction of a 2500 t / a isostatic pressing graphite material production base in Chongqing. The production base is not a complete production line, and its key processes such as abrasives, formulations, kneading, granulation and other key processes are not produced in Chongqing. And part of the graphitization and purification process is carried out in the factory in Kunshan, Jiangsu Province. These foreign-invested multinational companies still put the core material formulation and process of isostatic pressing graphite material production abroad. This is a constraint and test for the development of isostatic pressing technology in China, and we need to invest more manpower and material resources to explore it.
2. Differences in technology differences in technology can be seen from the following table. China needs to improve both hardware equipment and process flow. Process and equipment: conventional process flow in China and foreign countries: batching → molding → first baking → first soaking → second baking → third baking → third baking → fourth baking → graphitization batching → molding → first baking → first soaking → second baking → low graphitization automation, high production cost, low yield, high advanced level
3. Product performance differences the following table shows the differences in the performance of isostatic pressing graphite products at home and abroad. It is precisely because of the differences in raw materials and processes that our product performance lags behind. Particle size (? M) average China and foreign 25-45 5-25 min 8 1-3 purity (PPM) high 200 50 ultra high < 20 < 2 low high low high low high short mechanical strength finish machining performance service life
4. Size at present, large and super large isostatic pressure isotropic graphite is a gap in China's graphite products. At present, the largest isotropic graphite with a diameter of 2500mm can be produced in Japan, and the diameter of Sigri products can also reach 1250mm. Chongqing Roland special graphite Co., Ltd. can produce isostatic pressing graphite with a maximum diameter of 1500mm and a maximum length of 2m. However, there are few large-scale isotropic graphite in China, and there is excess capacity below 500mm in diameter. However, there are few isotropic graphite above 600mm in diameter, and the equipment is difficult to match, and the product quality is difficult to be stable.
From the above four aspects, it can be seen that the isostatic pressing technology in China is still in the initial stage, and there is still a long way to go. However, China imports about 3 / 4 of the isostatic pressing graphite blanks from abroad every year, and China consumes about 1 / 4 of the global isostatic pressing graphite products. It can be seen that China is undoubtedly a potential isostatic pressing graphite Market in the world. However, at present, isostatic pressing graphite products have only a history of nearly 10 years in China, which is still in its infancy. The isostatic pressure graphite produced by domestic manufacturers has low output, and its quality, performance, product size and specifications can not fully meet the market demand. Most of them are low-end small-size products, which have a large gap with the products of major foreign manufacturers. The specific performance is that the size is small, the strength and density are not enough, and the most important difference is the non-uniformity of the material structure and performance. These gaps are mainly due to the fact that the selection of raw materials and production technology have not reached the advanced level. Almost all high-end special graphite is imported, mainly from the four isostatic pressing graphite production bases of the United States, Japan, Germany and France.
Therefore, we still have a lot to do in isostatic pressing. In addition, the application fields of special carbon products are very wide. From the perspective of application, compared with foreign special carbon products, our products also have shortcomings such as less specifications and less complete types.

（2） Negative electrode material carbon material was first found to be used as a negative electrode for lithium-ion batteries (LIB) in 1926. By the 1980s, it was further found that the potential of lithium intercalation reaction in carbon materials was close to that of lithium, which was not easy to react with organic solvents and had good recycling performance. Therefore, it was considered to be the best and most widely used negative electrode material for lithium-ion batteries. At present, the anode materials for lithium-ion batteries developed and used mainly include graphite, soft carbon and hard Caobon. There are natural graphite, artificial graphite and graphite carbon fiber in graphite. Petroleum coke, needle coke, carbon fiber, mesophase carbon microbends (MCMB) and so on are common in soft carbon. Hard carbon refers to pyrolytic carbon of polymer. The common ones are resin carbon, organic polymer pyrolysis carbon, carbon black, etc. Among the anode materials for lithium-ion batteries, graphite carbon anode materials are widely available and cheap,
Has always been the main type of negative electrode materials. In addition to graphitized mesophase carbon microspheres (MCMB) and low-end artificial graphite, modified natural graphite is gaining more and more market shares. China is rich in natural graphite mineral resources. In terms of the industrialization of lithium-ion negative electrode materials using natural graphite as raw materials, Shenzhen beiteri battery materials Co., Ltd. promotes the development of traditional industries with high and new technology. It processes ordinary flake graphite into spherical graphite by using unique plastic grading, mechanical modification and thermochemical purification technologies, and improves the purity to more than 99.95%, up to 99.9995%. Through mechanical fusion, chemical modification and other advanced surface modification technologies, we have developed and produced high-end negative electrode materials with international leading level. Its first discharge capacity is more than 360mah / g, the first efficiency is more than 95%, the compaction ratio is 1.7g/cm3, the cycle life is 500 times, and the capacity is maintained at more than 88%.
The products are exported to Japan, South Korea, the United States, Canada, Denmark, India and other countries, and are applied in more than 40 domestic lithium battery manufacturers. The company has an annual output of 1800 tons of natural composite graphite (MSG, AMG, 616, 717, 818, etc.), 1200 tons of artificial graphite negative electrode materials (SAG series, NAG series, 316 series, 317 Series), 3000 tons of spherical graphite (SG), 5000 tons of natural micro powder graphite and 600 tons of lithium manganate positive electrode materials, and is constantly expanding its production scale. At the same time Develop products for customers according to equipment and existing problems. The products produced are stable and uniform in quality, with good electrochemical performance and excellent processing performance. The specific surface area, tap density, compaction density, impurity content and particle size distribution of the products can be adjusted. The main production equipment and testing instruments are imported from abroad, thus forming part of the company's unique core competitiveness. In the negative electrode material industry of lithium-ion batteries, beiteri has led the development direction of the industry. Table 1 performance comparison of natural graphite negative electrode materials from different manufacturers Table 2 performance comparison of artificial graphite negative electrode materials from different manufacturers Table 3 performance comparison of mesophase carbon microspheres (MCMB) negative electrode materials from different manufacturers Table 4 competitiveness of negative electrode materials compared with natural graphite negative electrodes mainly developed in China, Japan pays more attention to the research of hard carbon materials, such as resin carbon (such as phenolic resin, epoxy resin, POLYFURFURYL alcohol pfa-c, etc.) Organic polymer pyrolytic carbon (PVA, PVC, PVDF, pan, etc.), carbon black (acetylene black). Among them, Sony of Japan has used POLYFURFURYL alcohol resin carbon pfa-c as the negative electrode material of lithium-ion batteries. The capacity of pfa-c can reach 400mah / g, and the crystal plane spacing (D002) of pfa-c is equivalent, which is conducive to the insertion of lithium without causing significant expansion of the structure, and has good charge and discharge cycle performance. Another kind of hard carbon material is poly (phenylene) (PAS), an amorphous semiconductor material obtained by pyrolysis of phenolic resin below 800 ℃. Its capacity is as high as 800 MAH / g, and the spacing between crystal planes is 0.37-0.40nm, which is conducive to the intercalation and deintercalation of lithium in it and has good cycle performance. Graphite anode materials have been successfully commercialized, but there are still some insuperable weaknesses. This is because the carbon negative electrode will form a passivation layer (SEI layer) in the organic electrolyte, which can transfer electrons and lithium ions, but will cause irreversible loss of initial capacity; Moreover, the potential of the carbon electrode is very close to the potential of metal lithium. When the battery is overcharged, metal lithium is easy to precipitate on the surface of the carbon electrode, which may form lithium dendrites and cause short circuits; Secondly, at high temperature, the protective layer on the carbon negative electrode may decompose and cause the battery to catch fire; In addition, the performance of carbon electrode is greatly affected by the preparation process. In view of the above, it is still an important topic to find non carbon anode materials with better performance for lithium-ion batteries. In recent years, many researchers have reported their achievements in the research of non carbon anode materials, especially in the field of intermetallic compounds. Their research results show that although the specific capacity of metal based compounds is slightly reduced compared with pure metal negative electrode materials, the cycle performance is significantly improved.
（3） Flexible graphite flexible graphite is a deep-processing product of flake graphite. It takes advantage of the characteristic that flake graphite can form interlayer compounds. After the flake graphite is subjected to specific chemical treatment, it forms some interlayer compounds. After high-temperature heat treatment, the interlayer compounds are decomposed. At the same time, the graphite expands rapidly along the c-axis direction to form a material with excellent flexibility, that is, expanded graphite (or flexible graphite), The materials of various shapes formed by pressing expanded graphite with or without binder are flexible graphite materials. Flexible graphite has excellent properties. While retaining the high temperature resistance, corrosion resistance, self lubrication and other properties of flake graphite, it also has the characteristics of softness, resilience, plasticity, impermeability, self adhesion, low density and anisotropy. Therefore, it can work under harsh conditions. For example, in terms of sealing, compared with rubber and asbestos, it has incomparable advantages and can be called the "king of sealing" in contemporary times. Some people also call it a "revolutionary material". It is precisely because of this that flexible graphite has attracted universal attention and developed rapidly all over the world.
Since the United carbide company of the United States first developed expanded graphite sealing materials in the 1960s, flexible graphite has entered many fields and even some high-tech fields in just 30 years. Especially in developed industrial countries such as the United States, Japan, Britain and Germany, the research on flexible graphite is very extensive, which has involved many deep-seated problems such as the preparation method of interlayer compounds, and it is still likely to continue to develop. The research and application of flexible graphite in China started relatively late. In the past, the advanced flexible graphite materials used for key equipment were generally imported from abroad. After 1978, with the deepening of reform and opening up, the research and development of flexible graphite developed rapidly, and thus entered a new stage. In the early 1980s, China's flexible graphite was only used as a sealing material, and it was only used as a static seal in a few industries such as petroleum and chemical industry, with a very narrow application range.
After the mid-1980s, with the deepening of scientific research and the improvement of product quality, there was a breakthrough in the application of flexible graphite. First of all, it has improved the sealing, and can work normally under the condition of large pressure and temperature alternation, that is, it can be used as a dynamic seal. At this time, it not only prevents leakage, but also protects the shaft and valve stem from wear with its own lubricity, which has the effect of extending the service life of the equipment. Flexible graphite is especially popular in automobile, shipbuilding and other industries because it is impermeable to various liquids and vapors and can achieve complete sealing. Secondly, flexible graphite is also made into various protective fluxes, which are widely used in ingot casting technology. Third, some manufacturers have also achieved initial success in using flexible graphite as a protective material in smelting rare metals. In addition, flexible graphite is also used as anti radiation lining material for atomic nuclear devices, impurity diffusion barrier material and heat shielding material in high-temperature furnaces, electrical contacts or heating elements of high-temperature graphite components, crucible lining, improved rectifier brush and variable resistor brush.
In the past ten years, the production of flexible graphite products in China has developed from the beginning to more than 100 manufacturers, with an annual output of about 600 tons. The successful development of domestic flexible graphite materials and the expansion of production capacity have not only ended the situation in which China relied on imports in this respect in the past, but also promoted the progress of related industries. Although the research and development of flexible graphite in China has made rapid progress, there is still a big gap compared with Japan, Germany and the United States. The main reason is that the production level is low and the product quality lags far behind that of developed countries. For example, the tensile strength of flexible graphite products is nearly 20% lower than that of similar foreign products, and the friction coefficient is 20% higher than that of foreign products. In addition, in terms of varieties and specifications, we also seem to be single. Some developed countries in the West and Japan have developed more than 1600 kinds of flexible graphite products, such as oxidation-resistant and corrosion-resistant products, according to different use conditions, which have almost reached the level of everything; In terms of flexible graphite product composites, Japan has successfully developed six kinds, but we only have three kinds, and one of them is still in the trial stage.
（3） At present, there are more than 400 carbon enterprises in China, with an annual production capacity of about 700000 tons. China is one of the world's largest producers of graphite electrodes. However, there are only more than 50 enterprises with matching processes and mass scale production, which still lags behind the technical level of foreign countries. At present, the largest specification of graphite electrode in China is Φ 700 mm, and in the early 21st century, it has been used in the world Φ 800 mm graphite electrode. In recent years, with the optimization and upgrading of China's metallurgical industrial structure, small electric furnaces with backward production equipment have been gradually eliminated, and high-power and ultra-high-power electric furnaces have developed rapidly. As a result, the market supply and demand of ordinary power and small and medium-sized graphite electrodes have greatly shrunk, and the products are seriously surplus. The supply and demand of high-power graphite electrodes are basically balanced. The demand for ultra-high power and large-sized graphite electrodes is increasing year by year, and the product supply exceeds the demand.
Therefore, in recent years, the supply and demand of graphite electrodes in the carbon industry are basically in a situation where the supply of ultra-high power electrodes exceeds the demand, the supply and demand of high-power electrodes are basically balanced, and the supply of ordinary power electrodes exceeds the demand. In terms of variety structure, there is a big gap with developed countries. At present, u-car in the United States, Tokai in Japan, Showa electric, etc. all produce ultra-high power electrodes, and about 80% of them are ultra-high power electrodes with large specifications of more than 500 mm. However, the output of ultra-high power electrodes in China only accounts for about 27% of the total output of graphite electrodes. Ultra-high power and high-power electric furnace steelmaking can save 10% ~ 20% of electricity, shorten the smelting time by 20%, and save more than 10% of the unit cost. Therefore, the development of ultra-high power electric furnace steelmaking is the general trend& nbsp;