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How Much Do You Know About Lithium Battery Cathode Materials?

- Sep 27, 2018 -

Research Background

In recent years, the double harvest of China's new energy vehicle production and sales has driven the rapid development of the entire upstream and downstream industry chain, especially the demand for power batteries continues to rise. Since the power battery accounts for about 30-40% of the new energy vehicle manufacturing cost, in order to make the new energy vehicle more competitive in price and form sufficient market competitiveness, the power battery cost must be reduced. Among the constituent costs of the power battery, the cost of the positive electrode material exceeds 40%, so how to reduce the cost of the positive electrode material becomes the key.

About the comparison of lithium iron phosphate and ternary materials

Among the positive electrode materials, the most commonly used materials are lithium cobaltate, lithium manganate, lithium iron phosphate, and a ternary material (a polymer of nickel cobalt manganese). At present, foreign-funded Japanese and Korean companies mainly use ternary battery materials to be the leading technology in China. However, in the application of the Chinese market, lithium iron phosphate batteries have the upper hand compared to ternary materials. Last year, the amount of lithium iron phosphate was as high as 20 Gwh, accounting for 73%, while the ternary material battery was only 6.3 Gwh, accounting for only 22%.

However, from the technical field, the controversy over the battery route continues. Will the future lead the role of lithium iron phosphate or ternary material batteries?

From the perspective of energy density, the ternary battery is indeed superior to lithium iron phosphate. The foreign companies represented by Tesla, Samsung and LG use ternary materials; while the lithium iron phosphate battery has made great progress in recent years. The specific energy is already close to the ternary material battery, and the domestic automobile giant BYD uses lithium iron phosphate material. According to authoritative data, the specific energy of the ternary material battery is 160-200 wh/kg, and the lithium iron phosphate battery is 120-150 wk/kg. However, some experts said that the specific energy is not absolute, and the specific energy of the lithium iron phosphate battery can be 160wh/kg, but other data should be compromised. Therefore, the data of the power battery is based on market demand. From the perspective of cost, it is not intended to be dominated by lithium iron phosphate. The raw materials of ternary material batteries require precious metals. The price is high and it is difficult to lower in the future. The raw materials of lithium iron phosphate batteries are relatively stable in price and may be large in the future. The amplitude is reduced. Moreover, the ternary materials are mainly supplied by foreign capital, so they are not included in the scope of subsidies of the state, and the cost is definitely higher than that of lithium iron phosphate; from the perspective of safety, lithium iron phosphate is more advantageous. The ternary material is composed of three kinds of nickel, cobalt and manganese. When it reaches a certain temperature, it will decompose. The ternary lithium material will decompose at a lower temperature of about 200 degrees, and the lithium iron phosphate material is around 800 degrees. Moreover, the chemical reaction of the ternary lithium material is more intense, and oxygen molecules are released, and the electrolyte rapidly burns under the action of high temperature, and a chain reaction occurs. To put it simply, the ternary lithium material is more likely to catch fire than the lithium iron phosphate material. However, it should be noted that we are referring to materials, not batteries that have become finished products. At the beginning of this year, the state issued a suspension (suspension) of the use of the ternary material battery regulations, indicating that in the short term, the policy level does not allow the use of three yuan in the passenger car field, indicating the country's orientation.

However, lithium iron phosphate batteries have a fatal disadvantage, that is, poor low temperature performance, even if they are nano-sized and carbon coated, this problem is not solved. Studies have shown that a battery with a capacity of 3500 mAh, if operated in a -10 ° C environment, after less than 100 charge and discharge cycles, the power will be abruptly attenuated to 500 mAh, basically scrapped. This is indeed not a good thing for China, which has a vast territory and a relatively low temperature in winter. In addition, the preparation cost of the material and the manufacturing cost of the battery are high, the battery yield is low, and the consistency is poor, which is also an important reason that the endurance of many pure electric vehicles cannot reach the nominal value. Therefore, we can see that there are quite a few new energy vehicles in China (whether pure electric or hybrid electric), or some relatively cheap new energy vehicles, which will choose lithium iron phosphate batteries for different reasons. It can be said that the use of lithium iron phosphate batteries has an indelible foundation for the mass production and promotion of new energy vehicles.

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