four major difficulties of Lithium battery are waiting for breakthrough

China officially regards new energy vehicles as one of the seven strategic emerging industries, including plug-in hybrid electric vehicles and pure electric vehicles. However, due to the high cost of manufacturing, the state is heavily subsidizing electric cars. The main reason for the high cost of electric vehicles is the high cost of lithium batteries, which have cost more than a third of the vehicle. The reason for the high cost of lithium batteries is closely related to the chemical materials involved.

The anode material

The anode materials of lithium battery mainly include lithium cobalt acid, lithium manganese acid, nickel manganese cobalt ternary materials and lithium iron phosphate. Among them, lithium iron phosphate is regarded as an ideal anode material in the industry due to its potential advantages in cycle life, safety and material cost that other materials do not have. The existing problems are as follows: first, most of the major raw materials of electronic lithium carbonate (lithium carbonate content is over 99.5%) are imported; second, the production technology of lithium iron phosphate is also from abroad.

It is known that the electronic lithium carbonate can be extracted from lithium ore or salt lake and then purified from the lithium carbonate. China has the second largest lithium resources in the world. However, due to technical problems, the output of extracting lithium carbonate from ore and purifying it into lithium carbonate for electron electrode is very low. There is no electronic lithium carbonate extracted from salt lake. So we can only import a large number of electronic lithium carbonate from abroad. Due to the large import volume, domestic enterprises basically have no pricing power, and the foreign manufacturers have the final say.

In terms of technology, the development of lithium iron phosphate in China was basically in sync with that of other countries. However, there is no real leading enterprise in China and the industry lacks original innovative technology. Of the leading companies in the lithium iron phosphate battery industry, three are of the United States, A123 and Valence, and Canada's Phostech. lithium iron phosphate technology is regarded as a strategic technology in foreign countries, the United States, Canada, and other governments to this end at the national strength to participate in the establishment of technical barriers.

In the field of lithium iron phosphate materials, there are two core technology patents, one is the carbon coating technology, the other is the carbon thermal reduction technology. The former is owned by Canada foster company and has applied for a patent in our country. The patent right of the latter is owned by American Gaobo company, which has not applied for the patent in China, but the company has established two companies in Suzhou, which are respectively responsible for the production of lithium iron phosphate materials and battery manufacturing. The core patents on lithium iron phosphate batteries are held by several foreign companies, and the transfer of foreign companies' patents to Chinese companies will face high patent licensing fees, posing a huge potential threat to the industry.

In order to get rid of the passive position at the middle and low end of the industrial chain, efforts should be made in three aspects. First, the application for domestic lithium iron phosphate patent should be accelerated through technological research and development. Second, the core patents of foreign enterprises around the layout in the periphery. The third is to strengthen the study of battery structure design and battery combination control.

The electrolyte

Electrolyte plays the role of conducting electrons between the positive and negative electrodes of lithium battery, which is the guarantee for a lithium-ion battery to obtain the advantages of high voltage and high specific energy. The electrolyte is generally made up of high purity organic solvent, lithium electrolyte salt, necessary additives, and other raw materials under certain conditions and in a certain proportion.

Lithium batteries mainly use lithium perchlorate, lithium hexafluorophosphate and other electrolytes. But batteries made of lithium perchlorate have been banned in Japan and the United States because they don't work well at low temperatures and can explode. The batteries made of lithium fluoride have good performance, no explosion risk and strong applicability, especially those made of lithium hexafluorophosphate. In addition to the above advantages, the disposal of waste batteries in the future is relatively simple and eco-friendly, so the market prospect of this kind of electrolyte is very broad.

At present, the matching electrolyte has been basically localized, but the weakness is the electrolyte lithium hexafluorophosphate, which accounts for about half of the cost of the electrolyte. At present, the lithium hexafluorophosphate market is monopolized by several Japanese enterprises, such as the kanto electrochemical industry, SUTERAKEMIFA and morita chemical. The global capacity of lithium hexafluorophosphate is around 4000 tons/year. The three Japanese manufacturers have a capacity of 3,430 tonnes per year or about 85 percent of global capacity. Our country Tianjin Jinniu power source material limited liability company's current capacity is only 250 tons/year, and not for sale. The lithium hexafluorophosphate used by domestic electrolyte manufacturers is mainly imported from Japan and Germany.

The main reason for this situation is that the technical threshold of lithium hexafluorophosphate is quite high. Lithium hexafluorophosphate requires high purity and low moisture. However, because the product itself is easy to absorb moisture and decompose, it is extremely difficult to produce. It has strict requirements on raw materials and equipment and is a typical high-tech, high-risk production environment and high-difficulty production 'three high' technology product. The three main raw materials of lithium hexafluorophosphate are phosphorus pentachloride, anhydrous hydrofluoric acid and lithium fluoride, among which the latter two are the most difficult to produce, which requires domestic enterprises to make breakthroughs in the production process.

The diaphragm

The diaphragm in the lithium battery plays a role in preventing positive and negative short circuit, and in the lithium battery charging and discharging process to provide lithium ion transport channel. In short, a diaphragm is a porous plastic film. But it has a direct impact on the battery capacity, cycle performance and safety performance. Among the components of lithium battery, it is the most technical, accounting for 20% ~ 30% of the cost of lithium battery. But at present, our country 80% lithium battery diaphragm relies on the import.

The high technical content of diaphragm is due to the difficulty of its pore-making process. At present, the mainstream products of the membrane in the world are monolayer polypropylene (PP) nanoporous membrane, monolayer polyethylene (PE) nanoporous membrane, PP/PE/PP three-layer composite nanoporous membrane and other types after horizontal and vertical precision stretching. The production of PE and PP diaphragm by bidirectional precision drawing method is a multi-step, complex and precise processing process, including blow molding, film casting, continuous precision drawing, and other important links. The domestic diaphragm in the thickness of uniformity and the uniformity of the hole and foreign there is a big gap. At present, the international and domestic markets are basically controlled by several powerful foreign manufacturers, such as Celgard (USA), Entek (Entek), Asahi (Japan) and Toru (China).

Many domestic enterprises are trying to break through foreign technical barriers, the development of lithium battery diaphragm, but it is difficult. The difficulty is mainly reflected in the following three aspects: first, the patents related to the traditional diaphragm preparation process are basically monopolized by a few enterprises in the United States and Japan, and China lacks independent intellectual property rights in production technology; Second, domestic enterprises are deficient in the key technology of production diaphragm, especially the industrialization technology. Many enterprises are often able to provide better samples in small tests, but the consistency of products in mass production is poor. Third, China is in the new process, new methods of research and international synchronization, but the new process often equipment and process control requirements are higher, China's precision processing equipment foundation is relatively weak, limiting the industrialization.

Despite the difficulty, but domestic diaphragm has begun to start. Now some domestic enterprises has made some breakthrough in localization of aspects, such as Shenzhen Senior Technology Material Co., Ltd.,Foshan Jinhui hi-tech photoelectric Material Co., Ltd., Henan Xinxiang, Ryan, new energy materials Co., Ltd., etc., these companies have been produced with independent intellectual property rights of lithium battery diaphragm, but now mostly supply medium and low-end market, also need further mature of Membrane Technology.

With the gradual promotion of new energy vehicles, it is expected that new energy vehicles will increase the demand for lithium battery diaphragm by 10 times by 2012. The solution to the localization of the diaphragm will be of revolutionary significance not only to the lithium battery industry but also to the development of the entire electric vehicle industry.

The page contains the contents of the machine translation.