Comparison of ternary lithium battery and lithium iron phosphate battery
At present, there are two mainstream battery technology routes in new energy vehicles, lithium iron phosphate battery and lithium ternary battery. Although these two kinds of batteries compete in many application fields, the main line is the competition in the field of new energy vehicles, because this is the largest lithium battery application scenario in China. Since there is competition, there must be comparison. The comparison of battery cost performance is based on the price of the vehicle Can be carried out, and from the performance of lithium ternary battery and lithium iron phosphate battery which is better, it is necessary to set the conditions, get the actual parameters of the two batteries to explain. According to the experiments of relevant laboratories, new energy vehicle manufacturers and power battery manufacturers, although there are some subtle differences in specific parameters in each test, the judgment of the performance of the two batteries tends to be the same. Therefore, we take representative parameters for comparison.
1. BYD for passenger cars and Tesla for cars. This is the difference in volume between the two. From the perspective of current technology, the energy density of ternary lithium battery is generally 200wh / kg, which may reach 300wh / kg in the future; while the lithium iron phosphate battery is basically hovering at 100-110wh / kg, some of which can reach 130-150wh / kg, but it is very difficult to break through 200wh / kg. Therefore, the ternary material power battery can provide twice more space than lithium iron phosphate, which is very important for cars with limited space. Tesla produces ternary lithium battery, BYD produces lithium iron phosphate battery, so it is said that "BYD is the choice of passenger cars, Tesla is the choice of passenger cars".
2. Because of the high energy density and the low weight, the new energy vehicle with ternary lithium battery consumes less power, so it has faster speed and stronger endurance. Therefore, the car can run farther with ternary lithium battery, while the lithium iron phosphate new energy vehicle is basically used in the city bus at present, because the one-time endurance is not far, it needs a charging pile in a short distance to be able to charge.
3. Of course, the core of lithium iron phosphate battery for passenger buses is based on safety considerations. There are more than one Tesla car fire accident. The reason is that Tesla's battery pack consists of about 7000 18650 ternary lithium batteries. If there is an internal short circuit in these batteries or the whole battery pack, there will be an open fire. In case of an extreme collision accident, the short circuit will cause a fire. The material of lithium iron phosphate will not burn in case of short circuit, and its high temperature resistance is much better than that of ternary lithium battery.
4. Although the lithium iron phosphate battery is resistant to high temperature, its low-temperature performance is better. It is the main technical route of manufacturing low-temperature lithium battery. At - 20 ° C, the lithium iron phosphate battery can release 70.14% of its capacity, while the lithium iron phosphate battery can only release 54.94% of its capacity. Moreover, the discharge platform of the lithium iron phosphate battery is much higher than the voltage platform of the lithium iron phosphate battery It moves faster.
5. Charging efficiency, the ternary lithium battery is higher. The current limiting and voltage limiting method is adopted for lithium battery charging, that is, constant current charging is carried out in the first stage, when the current is large and the efficiency is high. When the constant current charging reaches a certain voltage, it enters the second stage of constant voltage charging. At this time, the current is small and the efficiency is low. Therefore, to measure their charging efficiency, the ratio of constant current charging capacity to total battery capacity is called constant current ratio. The experimental data show that the difference between them is not big when charging under 10C, but the distance will be opened when charging above 10C. When charging at 20c, the constant current ratio of ternary lithium battery is 52.75%, and that of lithium iron phosphate battery is 10.08%, the former is 5 times of the latter.
6. In terms of cycle life, the lithium iron phosphate battery is better than the lithium ternary battery. The theoretical life of the lithium ternary battery is 2000 times, but the capacity declines to 60% when it reaches 1000 cycles. Even the best brand Tesla in the industry can only maintain 70% of the power after 3000 cycles, while the lithium iron phosphate battery has 80% of the capacity after the same cycle.
From the comparison of the above six aspects, it can be concluded that the relative advantages of the two can help to answer the question which is the best: the safety, long life and high temperature resistance of the lithium iron phosphate battery; the light weight, high charging efficiency and low temperature resistance of the lithium iron phosphate battery; the adaptability of the two due to the difference in time and place is the reason for the coexistence of the two males.