Lithium anode material industry-technical analysis and development direction
Lithium anode material can be basically divided into two categories: carbon based materials and non carbon based materials. Carbon based materials mainly include natural graphite, artificial graphite, composite graphite, mesophase carbon microspheres, and disordered hard carbon and soft carbon.
Non carbon based materials are mainly divided into silicon based materials, lithium titanate anode material and lithium metal anode material. This article will introduce the industry development and direction of lithium battery anode material in 2022.
Lithium battery anode material industry needs technical innovation
At this stage, the anode material on the market are mainly graphite, including natural graphite and artificial graphite, and artificial graphite is the mainstream of the anode material market. In recent years, similar to cathode, electrolyte and other materials, the shipment of anode material has increased significantly.
The proportion of artificial graphite in the market is on the rise, accounting for more than 80% of the anode material market share, while the proportion of natural graphite, silicon based materials and other materials declined from 25% in 2017 to 18% in 2021.
Compared with natural graphite, the anode material market concentration of artificial graphite is relatively high. From the perspective of supply and demand in China and the price of anode material, it is basically in balance.
In terms of supply and demand, based on comprehensive data, China’s output of anode material can basically meet global demand. The product price, market share, industry supply and demand, and the proportion of artificial graphite and other materials shipped all indicate that the industry urgently needs a technological innovation.
First, the market share of artificial graphite has been further improved, indicating that other types of anode material have not replaced artificial graphite; Secondly, in 2021 when the downstream volume is increased, the product price will be stable and the supply and demand will be stable.
Finally, the cross-border of new manufacturers and the impact on the CR3 market share of the industry indicate that the leading lithium iron phosphate materials companies are gradually weakening their technological advantages.
The new lithium battery anode material is mainly silicon
With the continuous improvement of the requirements for the endurance of new energy vehicles, the cathode and anode material of lithium batteries need to be developed towards high specific capacity, which is a definite trend and a problem that new energy vehicles must face when replacing fuel vehicles.
However, the energy density of graphite anode is close to the theoretical specific capacity of 372mAh/g, and has reached the limit, so it is necessary to seek new development directions.
The new anode material is mainly silicon anode, and its theoretical capacity is far more than the limit capacity of graphite anode of 372mAh/g.
However, due to some key technologies and manufacturing processes that need to be broken through, the road to large-scale commercialization of silicon carbon anode material is still unclear, and only a few companies can mass produce on a small scale, so the current market share of silicon based anode is low.
The first discharge capacity of artificial graphite products provided by BTR reaches 335-360mAh/g, and the first discharge efficiency is more than 92%; The first discharge capacity of Shanshan’s anode product reached 355mAh/g, and the first discharge efficiency was more than 92%;
PTL can also provide anode material products with a first discharge capacity of 355mAh/g. Therefore, the specific capacity of large-scale commercial graphite anode material has been very close to its theoretical limit.
More and more manufacturers begin to build their own graphitization production lines
Artificial graphite is generally made from needle coke, petroleum coke, asphalt coke and other raw materials that are easy to be graphitized through pretreatment, crushing, shaping, mixing, secondary granulation, graphitization high temperature heat treatment and other processes.
Early granulation and graphitization are the core links of artificial graphite manufacturing, and the industry barrier is in the graphitization link. In the granulation link, the smaller the particles, the worse the first efficiency and compaction density, the better the magnification performance and cycle life, and vice versa.
Proper particle size distribution can improve the specific capacity of anode. If there is no differentiation in the products provided by leading companies in the industry, the development of the industry will move towards cost reduction and efficiency improvement.
Raw materials procurement and graphitization processing account for a large proportion of the production cost of artificial graphite anode material, among which the raw materials of artificial graphite are mainly petroleum coke, needle coke and other coke raw materials.
Graphitization processing is the key link in the production of artificial graphite anode material, and it is also a link with a large proportion of production costs. If the freight is included, the graphite chemical process accounts for about 50% of the total production cost.
In addition, the production equipment required for graphitization has a huge investment in the early stage. At first, the anode material manufacturers in the industry did not consider putting into production the graphitization processing production line in terms of capacity layout, but mainly carried out graphitization production through entrusted processing.
According to the data, nearly 600 million RMB will be invested to build a graphitization project with an annual output of 50000 tons of anode material. Silicon carbon technology has not been applied on a large scale, and most downstream battery manufacturers still choose graphite as the main anode material, thus leaving time and space for midstream anode material manufacturers to expand upstream.
More and more manufacturers began to build their own graphitization production lines. For example, the new Acheson graphitization furnace designed and built by Zhongke Electric, a anode manufacturer, has the advantages of low power consumption cost, low furnace core consumption cost and high degree of automation compared with the traditional graphitization processing production line.
It has the leading advantage and cost advantage in China’s anode material graphitization processing technology. Of course, this advantage is not absolute. PTL, BTR and other leading peer companies have also mastered the same technology.
At the same time, Zhongke Electric reduced the construction cost of the graphitization production line and improved the utilization rate of the graphitization production line through technology, process optimization and upgrading and other measures.
The only way for new manufacturers to obtain a certain market share is to improve the self-sufficiency rate of graphitization and reduce the cost of graphitization processing through the construction of the anode material integration project.
Substituting silicon for carbon is the new development direction of anode material industry
In addition to cost reduction and efficiency increase, the new development direction of the industry is to replace carbon with silicon. The theoretical specific capacity of silicon is 4200mAh/g, which is far more than 372mAh/g of graphite anode material.
Although silicon material has great development potential than carbon material in theory, there are a series of problems in the practical application of silicon material under the current technical conditions.
First of all, the efficiency of the first cycle is low. During the charging process of lithium ion batteries, the organic electrolyte will decompose on the surface of the anode to form a SEI (solid electrolyte phase interface) film, which will irreversibly consume the lithium ion of the cathode material.
If the lithium ion cannot be recycled, the battery capacity and energy density will inevitably decline. The irreversible cycle loss of silicon materials during the first charge can reach 30% at most, and that of graphite is 5-10%;
Secondly, the volume expansion problem is serious. During silicon charging and discharging, the volume expansion and contraction change reaches 320%, while the graphite is only 12%. The physical volume expansion will directly lead to the failure of the negative electrode and cause serious security problems.
Silicon carbon composite is the most representative improvement technical scheme
In order to solve the key problems of silicon anode material, there are many currently improved technical solutions, the most representative of which is silicon carbon composite, that is, combining silicon and oxygen according to certain chemical characteristics, taking a compromise between the high specific capacity of silicon anode material and the safety of carbon, and making carbon play a buffer role in the silicon charging and discharging process through certain physical structures.
However, at present, the limit of commercialization can only be achieved by doping 10% silicon into the silicon carbon cathode, with a specific capacity of 400-700mAh/g. This method can effectively improve the energy density of the whole battery.
According to the data, taking the flexible battery as an example, when the cathode material is NCM811, the energy density of the whole battery can be increased from 280Wh/kg to 295/310/330Wh/kg by using silicon carbon anode material with a specific capacity of 450/550/800mAh/g, compared with the use of 360mAh/g graphite negative material.
From the perspective of the layout of global manufacturers, BTR’s silicon carbon products passed the certification in 2013 and successfully shipped 1000 tons in 2017. However, so far, the substitution of silicon carbon materials for artificial graphite has not occurred, and the shipment growth rate is slow, which shows that there are some practical application problems of this technology.
If new energy vehicle manufacturers want to improve the penetration rate of their products, it is urgent to improve the energy density of batteries by increasing the specific capacity of anode material.
The core difficulty in the production process of silicon carbon anode material lies in the production of nano silicon powder. Boqian has absolute advantages in this respect, and is the only company in China that can stably provide high-quality nano silicon powder.
Due to the fact that the shipment of silicon carbon cathode is relatively small, this type of product accounts for a very small proportion in the shipment of Boqian, and the company did not disclose it separately.
In a word, the characteristics of technology development basically determine the development pattern of the industry and the development direction of companies in the industry to expand upstream.
As an indispensable component of lithium ion battery, the actual specific capacity of the most commonly used graphite materials has reached 360-365 mAh/g after decades of development, which is almost the same as the specific capacity (372 mAh/g).
However, the maturity of new technologies still needs time. The characteristics of anode material basically determine the development pattern of lithium battery anode materials industry and the development direction of companies in the industry to expand upstream. In this case, the next rapid growth of the anode material industry needs to wait for technological breakthroughs.