Artificial graphite for lithium ion batteries

Recently, the demand for artificial graphite is increasing, because the demand for artificial graphite for negative electrode materials such as lithium batteries is also increasing.

At present, most of the negative electrode materials are mixed and used with natural graphite and artificial graphite, which can not only increase the battery capacity but also increase the number of cycles. Said an employee who has worked in the field of cathode materials for lithium-ion batteries for many years. The reporter learned that MCMB (mesophase carbon microsphere) was the first commercial cathode material, and then artificial graphite began to be widely used. At that time, natural graphite also existed, but many manufacturers did not apply it well. With the continuous progress of battery technology and electrolyte technology, natural graphite is more and more used in all kinds of lithium-ion batteries with its low price.

In commercial applications, the technology of graphite carbon materials is relatively mature and the market price is relatively stable. Due to the increasing requirements for capacity density, power density, and safety performance of lithium-ion power lithium-ion batteries, negative materials with high capacity, high safety, good stability, and low price have become the focus of research and discussion.

Qiao Yongmin, R & D director of Shanghai Shanshan Technology Co., Ltd., pointed out that the cathode material of power lithium-ion battery has not formed its own system, and manufacturers also have different choices.

Artificial graphite and natural graphite mix and match

The first application in China is artificial graphite. In recent years, natural graphite has been used in turn. At present, the shipment of domestic natural graphite is still very high. Wang Zheng, director of Shenzhen beiteri advanced materials business department, said.

He believes that the cycle performance of artificial graphite will be relatively better, but if natural graphite is done well, the cycle performance will not be poor. Beiteri mainly exports. Samsung uses beiteri’s natural graphite, which has a very high-cost performance. The key is to match with the electrolyte.

Generally speaking, natural graphite has high capacity, high compaction, good processing performance, low cost, poor safety, poor cycle performance, and picky selection of electrolytes. However, due to the improvement of positive capacity, the relative cost will decrease. Therefore, it is widely used as a small battery and mobile phone battery. Artificial graphite has low capacity, low compaction, difficult processing performance, high cost, good circulation, and rate performance, and is not picky about the choice of electrolyte. It is generally used as a high-capacity battery and rate battery.

The reporter learned that most manufacturers are increasingly pursuing high energy density and have higher and higher requirements for the compaction density of negative electrode materials. However, due to its large cyclic expansion, high electrolyte consumption, poor liquid absorption performance under high pressure and poor rate performance, few pure natural graphite can be really applied to high-capacity systems.

With regard to the stability and cycle life of natural graphite products, the test is the production and processing process, process, and technology control of each factory. A negative electrode material technology R & D personnel told reporters that the reason why Japan can do a good job in battery capacity and performance with natural graphite is that they buy back the graphite powder supplied by domestic manufacturers and will further process it by themselves, After that, it can be used or sold back to the domestic market at a high price, and the current domestic technical level still does not use natural graphite well.

At the same time, he pointed out that because the technology of domestic battery companies is still lacking, the domestic market is mainly mixed with natural and artificial graphite, which not only reduces the cost but also reduces the difficulty of battery manufacturing.

At present, many mobile phone battery manufacturers, in order to make up for the shortcomings of natural graphite, adulterate artificial graphite in a certain proportion. For example, aluminum shell batteries use high-end natural graphite mixed with a small amount of low-end artificial graphite, which has a good effect on improving circulation and reducing cost. Miss Xu, the business manager of a negative electrode material factory in Qingdao, pointed out that with the improvement of customers’ performance requirements, high-end artificial graphite will be widely used in mobile phone batteries.

Huang Yuehua, deputy general manager of Changsha Xingcheng, also said that at present, the domestic market is dominated by artificial graphite, the raw materials of natural graphite are limited, and the production process is simple. The maximum gram capacity can only reach 370mah / g, and the artificial graphite can reach more than 400mah / g.

He believes that the use of artificial graphite in the past two years will increasingly exceed that of natural graphite.

Selection of high rate negative electrode materials

With the development of power lithium-ion batteries in recent years and people’s pursuit of fast charging and high rate charging performance, high rate electrode materials have attracted more and more attention.

Beiteri’s natural graphite is mainly used in consumer batteries, while Changsha Xingcheng’s artificial graphite is mainly aimed at the powerful lithium-ion battery market. In 2011, the company’s power cathode materials accounted for 40%. Huang Yuehua said that natural graphite is limited by raw materials, and the raw materials of artificial graphite come from a wider range.

In this regard, Wang Zheng believes that the important raw material of artificial graphite is petroleum coke, and the source is unstable, so the stability of the batch is very poor. The raw materials of natural graphite are very consistent because they come from graphite ore.

Natural graphite is also important in Japan. Beiteri accounts for about 30% of the domestic negative electrode material market, most of which are natural graphite.

Although artificial graphite was used earlier in China, the more core technology is still monopolized by Japanese manufacturers. In the long run, I think natural graphite is a trend. A negative material technician told reporters.

He said that Japan has used natural graphite as a powerful lithium-ion battery, that is, a layer of conductive carbon black is coated on the surface of natural graphite to solve its liquid absorption problem and crystal plane orientation problem, but the capacity and efficiency will be slightly affected. Some people in China have coated hard carbon on the surface of natural graphite, but it is not very uniform, and the batch stability is not good, which restricts the promotion.

In addition, lithium titanate with good safety, cycling, and high rate charge and discharge performance has also become one of the best choices for negative electrode materials of power lithium-ion batteries. Qiao Yongmin believes that lithium titanate has a certain demand space in the field of hybrid vehicles and energy storage. However, due to the high voltage platform, flatulence and other problems are difficult to solve, and the technology of domestic manufacturers is insufficient and the price is expensive, so it can not be used in batch at present. In terms of cost, soft carbon and natural graphite may be the trend of future application. The reality is that it is difficult to solve the high-temperature performance, so it is still difficult to make soft carbon and hard carbon practical at present.

Some insiders said that the use of soft carbon alone has no advantages. The use of soft carbon doped with graphite should make up for its shortcomings and can be used in the field of power lithium-ion batteries or energy storage. For example, Japan’s soft carbon is basically doped with artificial graphite, which is currently being promoted.

Influenced by the concept of new energy, the investment in the lithium battery industry is getting hotter and hotter, and the competition is further intensified by the construction of factories in China by Japanese negative electrode material giants. Dangsheng Technology (300073. SZ), which holds 40% of the shares of Changsha Xingcheng, disclosed that the performance of Changsha Xingcheng in the first quarter of this year was not ideal.

Huang Yuehua said that the economic environment was bad in 2011, and the company’s revenue was 20 million. It has improved slightly in the past two months. In recent years, there are more and more small companies of negative electrode materials.

With regard to the impact of the construction of Japanese negative electrode material giants in China on the domestic negative electrode material industry, Wang Zheng believes that this is not a bad thing for battery. After all, battery has the advantage of the industrial chain. In his opinion, the competition of negative electrode materials still depends on everyone’s technology. As long as you have technical advantages, you naturally have the confidence to face the competition.