Analysis of lithium iron phosphate battery and ternary lithium battery

"After everyone seriously thought and voted, I believe that lithium iron phosphate battery is returning to a certain local strong." This is the prediction of the lithium iron phosphate power battery by the vice president of BYD lithium battery Division.

Not long ago, some insiders analyzed that lithium iron phosphate batteries may “regain the tide”. “Resurgence” means that old things, old habits, old ideas, etc. that have disappeared have reappeared. Although lithium iron phosphate batteries are used less and less in the passenger car field, they still have a lot of room to play in the commercial vehicle field, therefore, the lithium iron phosphate battery has never disappeared, and why talk about "regaining tide".

Active players in the bus field

Compared with the yuan ternary lithium battery, the lithium iron phosphate battery is characterized by the absence of precious elements such as cobalt, low raw material prices, and abundant phosphorus and iron in the earth, and there is no problem of feeding; in high temperature and high heat environment The stability is high, and the disadvantage is that the density is low.

Commercial vehicles, especially passenger cars, carry a large amount of batteries. In order to reduce the risk of thermal runaway, lithium iron phosphate batteries have become the first choice for electric bus manufacturers.

The data is a good illustration of this. (This data is calculated inversely based on vehicle sales, and only calculates the domestic market, and does not consider inventory and transportation in transit products, may be slightly different from actual battery production data.)

In 2017, the new energy passenger vehicle market has 137GWh of power battery installed capacity, of which 76% is ternary lithium battery, the installed capacity is 10.34GWh, and the lithium iron phosphate battery is installed in the new energy passenger car model 2.98GWh, accounting for 22 %; the remaining 2% is a lithium manganate battery, a total of 0.23GWh.

In contrast, the new energy bus market has a power battery capacity of 14.3GWh, of which lithium iron phosphate battery is 12.84GWh, accounting for 90%; ternary lithium battery is only 0.03GWh, accounting for 0.21%.

In the field of special vehicles, the ternary lithium battery is still a big head, and lithium iron phosphate battery accounts for nearly 1/4.

The passenger car ran to the ternary lithium

In the 2018 subsidy New Deal, the three factors of cruising range, energy density and power consumption per 100 kilometer determine the subsidy quota for pure electric vehicles. The characteristics of lithium iron phosphate battery can be said to be contrary to the subsidy requirement: low energy density, the same the battery contains low battery power, which makes the cruising range unsatisfactory. If the battery capacity is increased, the quality of the whole will be greatly improved. The excessive conditioning quality will cause the power consumption of 100 kilometers to be unsatisfactory.

BYD's just-listed Tengshi 500 recently held a media test drive in Lhasa. Its working condition lasted 451km, and the maximum cruising speed of 60km was more than 600km! It can be said that it is the highest passenger car in the domestic market. The longest battery life of the pure electric car is actually using lithium iron phosphate battery, say you dare to believe?

However, Tengshi 500 just finished the publicity, and the new Tengshi appeared on the directory of the Ministry of Industry and Information Technology. The biggest change is that the new Tengshi uses a ternary lithium battery instead of lithium iron phosphate. (Reference reading: Analysis of the third batch of recommended catalog passenger cars in 2018)

Comparison of new and old BYD Teng potential parameters

Although the current Tengshi 500 uses a lithium iron phosphate battery to achieve 451km of battery life, it also pays a price, that is, its conditioning quality exceeds 2 tons!

What is the concept of 2 tons of kerb mass? As a B-class sedan, the quality of Tengshi 500 exceeds the medium-sized SUV of Weipa VV7 (1960-1985kg), which is almost equal to the large-scale SUV Toyota Prado (2065～2285kg). .

The reason is obvious. The energy density of lithium iron phosphate battery is low. BYD has to install a large number of batteries in order to increase the total power of Tengshi 500, so that the quality of the preparation exceeds 2 tons. Car weight is a very troublesome factor in the field of car design, it will bring a variety of negative effects, such as reduced vehicle braking performance, increased steering force, increased inertia. Presumably, Tengshi 500 made a compromise in some performances in order to improve the cruising range.

Therefore, BYD has opened up.

Comparing the parameters of the old and new Tengshi is not difficult to find, although the new Tengshi has reduced the cruising range by nearly 50km, the subsidy has increased.

According to the 2018 subsidy new policy, the energy density of the current Tengshi 500 battery system is 105.72Wh/kg, and the electricity consumption per 100 kilometers is 15.9kWh/100km. The amount of state subsidy that can be obtained is 5*0.6*1.1. =3.3 million; the energy density of the new Tengshi battery system is 141.61Wh/kg, and the electricity consumption per 100 kilometers is 15.1kWh/100km. The amount of state subsidy that can be obtained is 5*1.1*1.1=6. 05,000. The battery life is 50km less, and the subsidy is an extra 2,500.

Even the engineeredwithDAIMLERGROUP has switched the ternary lithium battery. What reason do we still insist on lithium iron phosphate in the passenger car field?

In the end, it’s all about money.

lithium iron phosphate batteries have been widely used in the field of new energy buses, and the energy density limits its development in the passenger vehicle field. This is a reality.

According to Shen Yan, BYD's mass-produced lithium iron phosphate shell battery has an energy density of 165Wh/kg, and the future limit is 200Wh/kg. The energy density of the mass-produced ternary shell battery unit has reached 190Wh/kg, in the future, high-nickel cathode materials with graphite anodes can achieve a maximum energy density of 260Wh/kg. On this basis, silicon-carbon anode materials are the key to breaking 300Wh/kg.

After consulting some power battery practitioners, there are two ways to increase the energy density of lithium iron phosphate batteries in the future: one is to add lithium manganese oxide, using lithium manganese iron phosphate cathode material; the other is the same as ternary lithium. A silicon carbon anode material is used.

According to the GGII data of the Institute of Advanced Research and Development of Lithium Ion, the price of lithium iron phosphate battery pack at the end of 2017 decreased from 1.8 to 1.9 yuan/Wh at the beginning of the year to 1.45 to 1.55 yuan/Wh at the end of the year; The price of the power battery pack dropped from 1.7 to 1.8 yuan/Wh at the beginning of the year to 1.4 to 1.5 yuan/Wh at the end of the year. It seems that lithium iron phosphate batteries do not have a large advantage in the price of the group.

The reason why there will be a "regain" in the lithium iron phosphate battery is because the subsidy policy is adjusted year by year (it can be said that it is a decline). If the subsidy disappears in 2020, the price of raw materials (especially cobalt) in the ternary lithium battery will remain. High, car companies may change their minds, lithium iron phosphate batteries once again become popular. A small engineer who worked in the Ningde era said: "If a lithium iron phosphate battery uses a silicon carbon anode material, even if it achieves an energy density of 200 Wh/kg, it may not be much cheaper than a ternary lithium battery. Shouldn't it be? Is everyone working together to get the price of ternary lithium?"

To put it another way, the 200Wh/kg lithium iron phosphate battery unit in 2020 can reach a cruising range of 300 to 400km after loading, which is not a good thing for consumers.

Cobalt prices are skyrocketing, both in battery companies and in automakers. If you want to switch the ternary lithium battery, at the expense of the cruising range is to get more subsidies. In the era of non-subsidy in 2020, if the price of 200Wh/kg lithium iron phosphate battery is low, the car companies use lithium iron phosphate batteries to control the cost, and maintain the mileage of the product at the level of two years ago. This will not form a healthy market.

We need lithium iron phosphate batteries to continue to shine in the passenger car field, but the passenger car field has to hope for the ternary lithium battery, just ask "cobalt grandma" not so terrible.

The page contains the contents of the machine translation.