Will ternary CR2025 battery become the mainstream of new energy vehicles?

In recent years, my country's new energy vehicle industry has been forging ahead under the dual benefits of policies and markets, and power batteries as its core components have also received increasing market attention. As we all know, the core technology of new energy vehicles is "three electricity", namely batteries, electronic controls, and motors. As one of the three core components of electric vehicles, batteries bear the heavy responsibility of electric vehicle range, and lithium iron phosphate and ternary CR2025 battery are the mainstream choices for power batteries in my country.

However, with the advancement of research and development technology, ternary CR2025 battery have exploded with greater potential. Among the 296 new energy passenger cars announced by the Ministry of Industry and Information Technology in 2017, the most used is ternary lithium, with a total of 221 models, and only 33 models use lithium iron phosphate.

Since the beginning of last year, BYD, which has been using lithium iron phosphate batteries, has launched a number of models equipped with ternary CR2025 battery, such as Song EV300, Qin 80 and Tang 100, contrary to its usual practice. In October this year, BYD officially announced that in the future, in addition to continuing to use lithium iron phosphate batteries in the public transportation field, all PHEV passenger cars of the company will use ternary CR2025 battery; next year, pure electric vehicles such as E5, E6, Qin EV will also switch to ternary CR2025 battery.

So, which is better, lithium iron phosphate or ternary lithium battery? In fact, the issue that consumers are concerned about is nothing more than: which battery has a longer range, longer life, and is safer. Let's analyze these issues one by one.

Energy density (range) comparison

Compared with the energy density of lithium iron phosphate batteries, ternary CR2025 battery have a higher energy density and a higher voltage, so the battery capacity of the same weight of the battery pack is larger, and the car can run farther. In addition, higher energy density can free up more body space, which is a plus for home users.

At present, the large number of ternary lithium battery production lines launched in China is also closely related to subsidy policies. According to the circulated subsidy adjustment plan for new energy passenger vehicles, in 2018, the battery system energy density must reach 140Wh/kg to enjoy 1.1 times the subsidy, while the subsidy adjustment coefficient for low energy density (105-120Wh/kg) has dropped to 0.5, and the gap between high-end and low-end subsidies has further widened, and car companies will undoubtedly pursue the former more.

The energy density of lithium iron phosphate battery monomers is usually between 90-120Wh/kg, while the energy density of ternary lithium battery monomers can reach about 200Wh/kg. As a global leader in automotive CR2025 battery, CATL plans to develop ternary CR2025 battery with an energy density of 300-350Wh/kg before 2020, and the cruising range will have a qualitative leap by then. On the contrary, lithium iron phosphate batteries have reached a bottleneck in the research and development of energy density, which has directly led to some car companies giving up on lithium iron phosphate batteries.

Charging efficiency comparison

Ternary lithium has obvious advantages over lithium iron phosphate in terms of charging efficiency. When the ternary lithium battery and the lithium iron phosphate battery are charged below 10C, there is no obvious difference in the constant current ratio. When the charging rate is above 10C, the constant current ratio of the lithium iron phosphate battery decreases rapidly, and the charging efficiency decreases rapidly. For new energy vehicles, a more efficient charging time can significantly improve the car experience. After all, it is quite helpless to wait for the car to be fully charged before going on the road.

Service life comparison

In terms of service life, lithium iron phosphate has an advantage over ternary lithium in terms of recycling rate, but for ordinary families, the rated cycle life of both far exceeds the actual use. In addition, the low-temperature performance attenuation of lithium iron phosphate batteries is a major defect. Studies have shown that if a battery with a capacity of 3500mAh works in an environment of -10℃, after less than 100 charge and discharge cycles, the power will decay sharply to 500mAh. As the main market for pure electric vehicles, the temperature in Beijing is often around minus 16℃ in winter, which will cause great trouble to car owners.

Safety comparison

In terms of material system, both batteries will decompose when reaching a certain temperature. The decomposition temperature of lithium iron phosphate battery is higher than that of ternary lithium battery, but this does not mean that the safety of ternary lithium battery is poor. After all, the safety design of power battery system can be improved through power connection structure, thermal management design, battery management system and other aspects. By making the safety measures more perfect and scientific, the battery can work in a safe state. For example, the ITCS battery temperature management system equipped in Geely New Energy's electric vehicles can start cooling at 38°C to ensure that the battery operates in a safe temperature range.

Through the above analysis, it is not difficult to find that although lithium iron phosphate battery is slightly better in high temperature resistance and cycle life, ternary lithium battery has obvious advantages in energy density, cruising range, low temperature performance and charging efficiency, and shows greater development possibilities.

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