Ternary lithium batteries may become the mainstream of new energy vehicles

In recent years, my country's new energy vehicle industry has been advancing 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 the "three electrics", namely batteries, electronic controls, and motors. As one of the three core components of electric vehicles, batteries are responsible for the mileage of electric vehicles, and lithium iron phosphate and ternary lithium batteries are the mainstream choices for power batteries in my country.

However, with the advancement of research and development technology, ternary lithium batteries have shown greater potential. Among the 296 new energy passenger cars in eight batches announced by the Ministry of Industry and Information Technology in 2017, ternary lithium batteries are the most widely used, with a total of 221 models, while 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 lithium batteries, such as Song EV300, Qin 80 and Tang 100, which are contrary to its usual practice. In October this year, BYD officially announced that in the future, except for the public transportation field, all the company's PHEV passenger cars will use ternary lithium batteries; next year, pure electric vehicles such as E5, E6, Qin EV will also switch to ternary lithium batteries.

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

Energy density (range) comparison

Compared with the energy density of lithium iron phosphate batteries, ternary lithium batteries have higher energy density and voltage, so the battery capacity of the same weight 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.

The large number of ternary lithium battery production lines currently launched in China is also closely related to the subsidy policy. 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) is reduced to 0.5, and the gap between high-end subsidies and low-end subsidies is further widened, and car companies will undoubtedly pursue the former more.

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

Charging efficiency comparison

Ternary lithium has a clear advantage over lithium iron phosphate in terms of charging efficiency. When charging at a rate below 10C, there is no significant difference in the constant current ratio between ternary lithium batteries and lithium iron phosphate batteries. When charging at a rate above 10C, the constant current ratio of lithium iron phosphate batteries 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 your car to be fully charged before you can go 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 degradation of lithium iron phosphate batteries is a major drawback. Studies have shown that if a battery with a capacity of 3500mAh works in an environment of -10℃, the power will decay sharply to 500mAh after less than 100 charge and discharge cycles. As the main market for pure electric vehicles, Beijing's winter temperature is often around minus 16℃, which will cause great trouble to car owners.

Security comparison

In terms of the material system, both types of batteries will decompose when they reach a certain temperature. The decomposition temperature of lithium iron phosphate batteries is higher than that of ternary lithium batteries, but this does not mean that the safety of ternary lithium batteries is poor. After all, the safety design of the power battery system can be improved through multiple aspects such as power connection structure, thermal management design, and battery management system. 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 degrees 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 batteries are slightly better in high temperature resistance and cycle life, ternary lithium batteries have obvious advantages in energy density, cruising range, low temperature performance and charging efficiency, and show greater development possibilities.