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Comparison of ternary lithium battery and lithium iron phosphate battery
Time:Nov 26, 2021
At present, there are two mainstream battery technology routes in new energy vehicles, lithium iron phosphate battery and ternary lithium battery. Although these two batteries compete in many application fields, the competition in the field of new energy vehicles is the main line, because This is the largest lithium battery application scenario in China. Since there is competition, there must be a comparison. The comparison of the cost performance of the battery can be carried out through the price of the car. In terms of performance, it is necessary to compare the ternary lithium battery and the lithium iron phosphate battery. By setting the conditions, the actual parameters of the two batteries are obtained. According to the experiments of relevant laboratories, new energy vehicle manufacturers, and power battery manufacturers, although each test inevitably has subtle differences in specific parameters, the judgments on the performance of the two batteries tend to be consistent. To this end, we take representative parameters for comparison.

1. Choose BYD for passenger cars and Tesla for cars. This is the difference in size between the two. Judging from the current technology, the energy density of ternary lithium batteries is generally 200Wh/kg, and may reach 300Wh/kg in the future; while lithium iron phosphate batteries are currently hovering at 100~110Wh/kg, and some can reach 130~150Wh. /kg, but it is very difficult to break through 200Wh/kg. Therefore, the ternary material power battery can provide twice as much space as lithium iron phosphate, which is very important for cars with limited space. Tesla produces ternary lithium batteries, and BYD produces lithium iron phosphate batteries, so there is a saying that "BYD for passenger cars, Tesla for cars".

2. Also because of the high energy density and much smaller weight, the light weight and small footprint determine that the ternary lithium battery new energy vehicle consumes less power, so the speed is faster and the battery life is stronger. Therefore, ternary lithium batteries can be used for cars to run farther, while lithium iron phosphate new energy vehicles are basically used for city buses. Because the battery life is not far at a time, it is necessary to have charging piles for charging within a short distance.

3. Of course, the core of the use of lithium iron phosphate batteries in passenger buses is based on safety considerations. There have been more than one fire accidents in Tesla cars. The reason is: Tesla's battery pack consists of about 7,000 18650 ternary lithium batteries. If the batteries of these units or the entire battery pack have an internal short circuit, an open flame will be generated. The collision accident, the short circuit caused the fire. The lithium iron phosphate material will not burn in the event of a short circuit, and its high temperature resistance is much better than that of the ternary lithium battery.

4. Although lithium iron phosphate batteries are resistant to high temperatures, ternary lithium batteries have better low temperature resistance and are the main technical route for manufacturing low-temperature lithium batteries. At minus 20°C, ternary lithium batteries can release 70.14% of their capacity, while Lithium iron phosphate batteries can only release 54.94% of their capacity, and due to low temperature conditions, the discharge platform of ternary lithium batteries is much higher than that of lithium iron phosphate batteries, and the voltage platform starts faster.

5. The charging efficiency is higher than that of the ternary lithium battery. Lithium battery charging adopts the current limiting and voltage limiting method, that is, constant current charging is performed in the first stage. At this time, the current is large and the efficiency is high. After 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 the charging efficiency of the two, the ratio of the constant current charging power to the total battery capacity is called the constant current ratio. The experimental data shows that there is little difference between the two when charging below 10C, but the distance above 10C will be widened. When charging at 20C, the constant current ratio of the ternary lithium battery is 52.75%, and the constant current ratio of the lithium iron phosphate battery is 10.08 %, the former is 5 times the latter.

6. In terms of cycle life, lithium iron phosphate batteries are better than ternary lithium batteries. The theoretical life of ternary lithium batteries is 2000 times, but basically at 1000 cycles, the capacity decays to 60%; Sla, after 3000 times, can only maintain 70% of the power, while the lithium iron phosphate battery has 80% of the capacity after the same cycle.

The comparison of the above six aspects can be roughly concluded that the relative advantages of the two are helpful to answer the question of which is better: the lithium iron phosphate battery is safe, long life, and high temperature resistance; the weight of the ternary lithium battery Light weight, high charging efficiency, and low temperature resistance, the difference between the two is the reason for the coexistence of the two.

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