In today's power battery market, lithium iron phosphate batteries and ternary lithium batteries are the main ones. The main characteristics of the two are the difference between energy density and safety. Energy density is related to the endurance of power batteries, and safety is also one of the most important indicators of power lithium batteries.
Then we will introduce the differences and connections between these two lithium batteries from the four aspects of energy density and safety, temperature adaptability, and charge and discharge efficiency:
The energy density of lithium iron phosphate batteries is much lower than that of ternary lithium batteries. The current subsidy standard for new energy vehicles uses the energy density of the battery pack system as an important indicator. The policy stipulates that when the energy density of the battery system exceeds 120Wh/kg, you can enjoy 1.1 times The subsidy between 90Wh/kg and 120Wh/kg can only enjoy 1 times the subsidy. It needs to be explained here that the energy density of the automotive power battery pack produced by Lilang Battery has reached 125Wh/kg.
The energy density of a single lithium iron phosphate battery is usually between 90-120Wh/kg, while the energy density of a single ternary lithium battery can reach about 200Wh/kg. It can be seen that the energy density advantage of a ternary lithium battery is relatively clear. The reason why a large number of ternary lithium battery production lines have been launched in China, coupled with the persistence of Japan and South Korea in the direction of ternary lithium battery technology, has injected strong confidence into the market.
We know that as far as the material system is concerned, the decomposition temperature of the positive electrode material of the ternary lithium battery is about 200 ℃, and the decomposition temperature of the positive electrode material of the lithium iron phosphate battery is about 700 ℃. In the laboratory test environment, short-circuiting the single lithium iron phosphate battery basically does not cause fire, but the ternary lithium battery is not the case. When using the ternary lithium battery, it is especially necessary to put forward higher requirements for thermal management. For the vehicle battery pack, the safety measures are more perfect and scientific. The lithium battery is effectively managed through the BMS, and the battery can work in a safe state.
my country has a vast territory and a complex climate. From the three northeastern provinces at the northernmost point to the Hainan Islands at the southernmost point, the temperature changes are very rich. Taking Beijing as an example, as the main market for electric vehicles, the highest temperature in Beijing in summer is around 40°C, while in winter it basically stays around minus 16°C, or even lower. Such a temperature range is obviously suitable for ternary lithium batteries with better low temperature performance. However, lithium iron phosphate batteries, which focus on high temperature resistance, will appear a little weak in winter in Beijing. What's more, compared with lithium iron phosphate, the high temperature resistance of ternary lithium battery is not far behind.
Figure 1 Adaptive temperature of ternary lithium battery and lithium iron phosphate battery
It can be seen from the figure above that, with 25°C as the benchmark normal temperature, there is almost no difference in the discharge capacity of the two types of batteries when they are discharged at a high temperature of 55°C and at a normal temperature of 25°C. However, at minus 20°C, ternary lithium batteries have obvious advantages over lithium iron phosphate batteries.
Charge and discharge efficiency
In addition to battery life, charging is also an important link in the actual use of electric vehicles, and ternary lithium batteries have a great advantage over lithium iron phosphate batteries in terms of charging efficiency.
Figure 2 Comparison of charging efficiency between ternary lithium battery and lithium iron phosphate battery
It can be seen from the table that when the ternary lithium battery and the lithium iron phosphate battery are charged below 10C, there is no significant difference in the constant current ratio. When the rate is charged above 10C, the constant current ratio of the lithium iron phosphate battery decreases rapidly, and the charging efficiency decreases rapidly.
The market competition between lithium iron phosphate and ternary is still evenly divided, and each has its own strengths. In the case of continuous innovation in battery technology, it is expected that revolutionary changes will occur in the near future. Ternary lithium batteries and lithium iron phosphate batteries with mature technologies have a place in the market by virtue of their respective advantages.