In recent years, China's new energy automobile industry has moved forward in the policy and market, and the power battery as its core component has also received increasing attention from the market. As we all know, the core technology of new energy vehicles is 'three powers. ', that is, battery, electric control, motor. As one of the three core components of electric vehicles, the battery is responsible for the cruising range of electric vehicles, and lithium iron phosphate and ternary lithium batteries are the mainstream choice for power batteries in China.
However, with the advancement of R&D technology, the ternary lithium battery has a greater potential. In the 8 batches of 296 new energy passenger cars announced by the Ministry of Industry and Information Technology in 2017, the most used is ternary lithium, a total of 221, using There are only 33 types of lithium iron phosphate.
Since the beginning of last year, BYD has been using the lithium iron phosphate battery to launch the EV300, Qin 80 and Tang 100 and other matching ternary lithium battery models. In October this year, BYD officially announced that it will continue to use lithium iron phosphate in the public transportation field in the future. Outside the battery, all PHEV passenger cars of the company use ternary lithium batteries; next year E5, E6, Qin EV and other pure electric vehicles should also switch ternary lithium batteries.
So, what are the advantages and disadvantages of lithium iron phosphate and ternary lithium batteries? In fact, the concerns of consumers are nothing more than: Which battery has a longer range, longer life and more safety. Here are a few The problem is to analyze one by one.
Energy density (river mileage) comparison
Compared with the energy density of lithium iron phosphate battery, the ternary lithium battery has higher energy density and higher voltage, so the battery of the same weight has a larger capacity and the car can run farther. In addition, the higher energy density can release more. More body space, which is a plus for home users.
At present, a large number of domestic ternary lithium battery production lines are closely related to the subsidy policy. According to the circulated new energy passenger car subsidy adjustment program, the energy density of the battery system must reach 140Wh/kg in 2018 to enjoy 1.1 times subsidy, while low energy The density (105-120Wh/kg) subsidy adjustment factor fell to 0.5, the gap between high-end subsidies and low-grade subsidies further widened, and car companies will undoubtedly pursue the former.
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 200Wh/kg. As the global leader in lithium batteries for vehicles, Ningde era is planned in 2020. In the past, a ternary lithium battery with an energy density of 300-350Wh/kg was developed, and the cruising range will have a qualitative leap. On the contrary, lithium iron phosphate battery has entered the bottleneck in the research and development of energy density, which also directly led to some vehicles. The company gave up the lithium iron phosphate battery.
Charging efficiency comparison
Ternary lithium has obvious advantages in charging efficiency compared with lithium iron phosphate. When ternary lithium battery and lithium iron phosphate battery are charged below 10C, there is no significant difference in constant current ratio. When charging at 10C or higher, the constant current ratio of lithium iron phosphate battery Rapidly lowering, charging efficiency is rapidly decreasing. For new energy vehicles, more efficient charging time can significantly improve the car experience. After all, it is quite helpless to wait for the car to be full.
Lifetime comparison
In terms of service life, lithium iron phosphate has an advantage over ternary lithium in recycling rate, but for the average household, the rated cycle life of both is far beyond the actual use. In addition, lithium iron phosphate battery The low temperature performance attenuation is a major defect. Studies have shown that a 3500mAh battery, if operating in a -10 ° C environment, after less than 100 charge and discharge cycles, the power will be sharply attenuated to 500 mAh. As a pure electric car The main market, Beijing winter temperature is often around minus 16 °C, which will cause great trouble to the owner of the car.
Security comparison
As far as the material system is concerned, both batteries will decompose when they reach a certain temperature. The decomposition temperature of the lithium iron phosphate battery is higher than that of the ternary lithium battery, but this does not determine that the safety of the ternary lithium battery is poor, after all, The safety design of the power battery system can also be upgraded through various aspects such as power connection structure, thermal management design, battery management system, etc., and the safety measures are designed more scientifically and scientifically, so that the battery can work safely. For example. Geely New Energy's ITCS battery temperature management system for electric vehicles can turn on 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 the lithium iron phosphate battery is slightly superior in high temperature resistance and cycle life, the ternary lithium battery has obvious advantages in terms of energy density, cruising range, low temperature performance and charging efficiency, and shows Greater development possibilities.
