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Ternary lithium battery and lithium iron phosphate battery
- Sep 15, 2018 -

The core technology of new energy vehicles is the battery that provides energy. The battery life and charging speed are the bottlenecks of battery technology development. After more than 30 years of development, most of the energy of electric vehicles are from various lithium battery packs. Provided, but the lithium battery is still not fully mature, and is still in constant exploration.


At present, lithium battery types include lithium manganate, lithium iron phosphate, lithium titanate, lithium cobaltate, and ternary materials. Lithium manganate, lithium titanate and lithium cobalt oxide batteries are gradually becoming more and more expensive due to energy performance and rare metal cost. It became a niche choice, while lithium iron phosphate and ternary lithium batteries were more widely used.


What are the characteristics of these two different lithium batteries, and what is the difference between them? Which technical route has the new energy auto companies adopted? Who can laugh at the end of these two lithium batteries? This article will explain each one for you.


Ternary lithium battery and lithium iron phosphate battery


The ternary lithium battery is called "ternary material battery", generally refers to a lithium battery using nickel-cobalt-manganate (Li(NiCoMn)O2, NCM) or nickel-cobalt lithium aluminate (NCA) ternary cathode material. Salt, cobalt salt and manganese salt are adjusted differently according to the ratio of three different components, so it is called “ternary” and contains many different types of batteries. Different from the shape, it can be divided into soft pack batteries, cylindrical batteries and square hard shell batteries. Its nominal voltage can reach 3.6-3.8V, high energy density, high voltage platform, high tap density, long cruising range, large output power, poor high temperature stability, but excellent low temperature performance and high cost.


Lithium iron phosphate battery uses lithium iron phosphate (LiFePO4) as the positive electrode material, and iron is used as the raw material of the battery. The cost is low, the second does not contain heavy metals, and the environmental pollution is small, and the working voltage is 3.2V. The PO bond in the lithium iron phosphate crystal is stable, so there is no leakage at zero voltage storage. The safety is very high under high temperature conditions or overcharge, and it can be quickly charged, high discharge power, no memory effect, and high cycle life. The disadvantages are poor low temperature performance, low tap density of the positive electrode material, low energy density, and high yield and consistency of the product.


These two types of batteries have their own strengths

Under high temperature conditions, the ternary material of the ternary lithium battery will decompose at 200 ° C, produce a violent chemical reaction, release oxygen atoms, and is prone to combustion or explosion under high temperature, so based on safety considerations In January 2016, the Ministry of Industry and Information Technology of the People's Republic of China temporarily restricted the use of ternary lithium batteries to pure electric buses through special provisions. The decomposition temperature of the lithium phosphate battery is 800 ° C, which is less likely to catch fire and has a relatively high safety.


Under low temperature conditions (temperature below -10 °C), the lithium phosphate battery decays very fast. After less than 100 charge and discharge cycles, the battery capacity will drop to 20% of the initial capacity, which is basically insulated from the use in cold regions; The ternary lithium battery has excellent low-temperature performance, and can maintain normal battery capacity at -30 °C, and is more suitable for use in low temperature areas in the north.


From the point of view of manufacturing cost, the cobalt element necessary for ternary lithium battery is less in China, and most of it is imported overseas. It is greatly affected by market fluctuations, so the cost of ternary lithium battery is bound to remain high, and lithium iron phosphate The raw materials required for the battery do not need to be imported, the supply is sufficient, the price is stable, and the cost is relatively low.


Technical route selection for battery manufacturers and electric vehicle companies


According to the data from January to April 2016, domestic lithium iron phosphate battery shipments can account for 75.3% of the total market, which can be said to be the mainstream technology form, while the proportion of ternary lithium batteries only accounts for 22.6%, but year-on-year. The growth rate has reached 3.47 times and it has developed very rapidly.


Japan's Matsushita, South Korea's LG Chemical, Samsung SDI and other technologies using ternary lithium batteries, such as the new energy giant Tesla has adopted Panasonic nickel-cobalt lithium aluminate ternary lithium battery, is the so-called NCA, in Model S The Model X uses a Panasonic 18650 battery pack, while the latest MODEL 3 uses a larger capacity 21700 cylinder battery pack.


Domestic new energy auto companies originated from cost problems in the early days, mostly using lithium iron phosphate batteries as energy sources. For example, BYD and other companies are the main manufacturers of lithium iron phosphate batteries, and launched many star products such as Qin, Tang and Song. Nowadays, due to the improvement of subsidies such as the cruising range of the country, the market share of ternary lithium batteries is gradually increasing.

Who can laugh at the end of the ternary lithium battery and lithium iron phosphate battery?


Domestic debates about ternary lithium batteries and lithium phosphate batteries are fierce. Who will become the mainstream of the technology in the future? At present, various manufacturers are exploring on two different roads. The risk of leakage, deformation, combustion and explosion of ternary lithium battery can not be ignored, but at present, new energy companies are working hard on battery management systems (such as overcharge protection OVP, over-discharge protection UVP, over-temperature protection OTP, Over-current protection OCP, etc.) also uses high-strength aluminum alloy protection structure, and many battery manufacturers have made good achievements in the technical route of adding titanium-titanium nanotubes, solvent-free PI adhesives, and solid electrolytes to the cathode materials. , greatly reducing risks and costs.


As a leading manufacturer of battery, BYD has been insisting on the technical route of lithium iron phosphate battery, and even started to add manganese element in lithium iron phosphate battery to explore lithium iron manganese phosphate battery, breaking the original energy density limit and cost control. It is also very good, but it poses new challenges for charging time.


Higher security and greater energy density are two sides that enterprises and researchers need to pursue at the same time. From the perspective of the development needs of new energy vehicles, ternary lithium batteries rely on greater energy density after gradually solving safety. In the future contest, we will gain certain advantages.


Conclusion

In the competition with lithium iron phosphate battery, the safety problem of ternary lithium battery needs to be improved. This is always a shadow in the minds of automobile companies. Even the leading technology products such as Tesla Model X have been used at home and abroad. An accident occurred in which the battery pack burned. However, in the long run, the ternary lithium battery has the characteristics of high energy density and low temperature resistance that are incomparable to lithium iron phosphate batteries. In the future of new energy vehicles, the ternary lithium battery will completely replace the safety and cost issues. At present, the market position of lithium iron phosphate will become the trend of the new energy market. This battle will be seen in three years at the earliest. Let us wait and see!