Market dispute between lithium iron phosphate and ternary materials

In 2017, the subsidy policy for new energy vehicles began to decline, but it still could not stop the expansion of lithium-ion enterprises. As the source of power for new energy vehicles, power batteries are closely related to life, safety, charging and discharging and market.

Among the power batteries, the main applications of new energy vehicles are lithium iron phosphate batteries and ternary lithium batteries. The biggest difference between the two is energy density and safety. The energy density is related to the endurance of the car. The safety is mainly reflected in the decomposition of materials at high temperatures. These two points are the most concerned issues when consumers buy new energy vehicles. They are also the most controversial places in the industry.

Energy density comparison

The energy density of lithium iron phosphate batteries is far less than that of ternary lithium batteries, but its safety is generally considered to be better than ternary lithium. Let's talk about energy density. At present, the subsidy standard for new energy vehicles depends on the energy density of the battery system. The specific policy is that when the energy density of the battery system exceeds 120Wh/kg, you can enjoy a subsidy of 1.1 times, only one-time subsidy can be enjoyed between 90Wh/kg and 120Wh/kg.

It is understood that the current lithium iron phosphate battery on the market has not been difficult to achieve 90Wh / kg, but there are very few companies to achieve 120Wh / kg. BYD has been focusing on lithium iron phosphate battery, which is at the domestic leading level in this technology. It has been rumored that BYD has developed a high-energy density lithium iron phosphate battery with a capacity density of 150Wh/kg, which is equivalent to ternary lithium. The battery is almost equal. Whether the rumor is true or not is not discussed at present, but as the industry leader BYD can only achieve this level, it can be seen that the use of lithium iron phosphate battery to get 1.1 times subsidy is not difficult, but this problem for the ternary lithium batteries are easy to achieve.

In addition, it can be seen from the capacity planning of several power batteries in 2017 that the capacity expansion of the ternary lithium battery is also particularly obvious. Even BYD, a company that loves lithium iron phosphate batteries in the past, maintains iron phosphate in 2017. Lithium production capacity remains unchanged and the expansion of ternary lithium batteries.

The results of ternary PK lithium iron phosphate are known at a glance.

Security comparison

In addition to the expansion of the ternary lithium battery at the supply end, it is also amplified at the demand side. The energy density requirement just mentioned is a driving force for the demand side of the ternary lithium battery and the other is from the ternary lithium battery will be officially released in 2017. Here is the second point of discussion on the advantages and disadvantages of ternary lithium batteries and lithium iron phosphate batteries "safety."

The ternary lithium battery will decompose at about 200 degrees (lithium iron phosphate requires a temperature of up to 700 degrees), and it will produce a more severe chemical reaction after decomposition, so it is easier to catch fire when the car collides. This is also a ternary lithium battery. It is generally considered to be unsafe where it is because of this reason that the ternary lithium battery was previously suspended in the passenger car.

However, the safety is actually more dependent on the entire power battery system, especially the battery management system (BMS). The qualified BMS can cut off the power in case of accidents to avoid fire, and cannot be easily pyrolyzed only because of the ternary lithium material. It is considered that the ternary lithium battery is not safe. With the safety of the ternary lithium battery being re-evaluated, the passenger car will lift the ternary lithium battery, which undoubtedly released a large market.

Temperature effect

China has a vast territory and a complex climate. The temperature changes from the northernmost three northeastern provinces to the southernmost Hainan islands are very rich. Taking Beijing as an example, as the main market for electric vehicles, the highest summer temperature in Beijing is around 40 °C, while in winter it is basically at around 16 °C, or even lower. Such a temperature range is obviously suitable for a ternary lithium battery having a better low temperature performance. The lithium iron phosphate battery, which focuses on high temperature resistance, appears to be somewhat weak in winter in Beijing. What's more, the high temperature resistance of ternary lithium batteries is not much different from that of lithium iron phosphate.

The results of ternary PK lithium iron phosphate are known at a glance.

It can be seen from the above figure that the two types of batteries are discharged at a high temperature of 55 ° C and discharged at a normal temperature of 25 ° C at a normal temperature of 25 ° C, and there is almost no difference in discharge capacity. However, at minus 20 ° C, the ternary lithium battery has a clear advantage compared with the lithium iron phosphate battery.

Charging efficiency comparison

In addition to battery life, charging is also an important part of the actual use of electric vehicles, and ternary lithium batteries have a very large advantage over lithium iron phosphate batteries in terms of charging efficiency.

The results of ternary PK lithium iron phosphate are known at a glance.

We have learned that the most common charging method currently on the market is constant current and constant voltage charging. Generally, constant current charging is used at the beginning of charging, and the current at this time is large, and the charging efficiency is relatively higher. After the voltage reaches a certain value, the current is reduced to constant voltage charging, which can make the battery charge more full.

It can be seen from the table that when the ternary lithium battery and the lithium iron phosphate battery are charged below 10C, there is no significant difference in the constant current ratio. When charging at 10C or higher, the constant current ratio of the lithium iron phosphate battery is rapidly decreased, and the charging efficiency is rapidly lowered.

Conclusion: The market dispute between lithium iron phosphate and ternary, although there is still no clear conclusion, and battery technology is changing with each passing day, it is expected that the revolutionary changes will come in the near future, but the author believes that the technology is mature. The ternary battery will gain a foothold in the new market due to its high energy density and large room for improvement, inferior safety, low temperature resistance and high charging efficiency.

The page contains the contents of the machine translation.