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What does the rejuvenation of lithium iron phosphate battery mean?




There is an important market signal in the power battery market - lithium iron phosphate battery is coming back.

The first signal was from BYD. Not long ago, BYD announced that it would launch a new generation of lithium iron phosphate batteries around April and may next year. At that time, the volume specific energy density of the new generation of lithium iron phosphate battery will be reduced by 50% (that is, the energy density will be greatly increased), but the cost will be reduced by 30%;

The second signal comes from Chery. Now Chery EQ, which runs all over the street, will replace the lithium-ion battery with the lithium-ion battery of iron phosphate. Before it, JAC iev6e, Baojun E100 and E200 have been listed in the catalogue of new energy vehicle promotion and application recommended models (the 7th batch in 2019) published by the Ministry of industry and information technology as lithium battery and lithium iron phosphate battery.

The third signal is the catalogue of the 8th batch of new energy vehicle promotion and application recommended models in 2019 released earlier this month. There are 246 electric vehicles in the catalogue, of which 169 are equipped with lithium iron phosphate battery, accounting for 69%, while in the first batch and the second batch, the proportion is 45% and 58%.

As we all know, compared with ternary lithium battery, lithium iron phosphate battery has higher security.

Recently, the battery safety laboratory of Tsinghua University released the Research Report on power battery safety in 2019. According to incomplete statistics, from January to the end of July 2019, there were more than 40 battery related electric vehicle safety accidents reported by domestic and foreign media.

In these cases, the proportion of accident vehicles equipped with ternary lithium battery reached 60%, while the proportion of lithium iron phosphate battery was only 5%, that is, only two cases - 4.24 in Hubei and 5.04 in Hangzhou, respectively. The cause of the accident has nothing to do with the battery, the former is the trunk is on fire and the battery is in good condition; the cause of the fire of the latter is unknown, but according to the report, it has nothing to do with the battery.

Although the lithium iron phosphate battery has obvious safety advantages, a fatal disadvantage makes it gradually disappear in the stage of passenger cars - the energy density is too low.

At the end of last year, the system energy density of most of the lithium iron phosphate batteries on the market was less than 90Wh / kg, even fewer enterprises could achieve 120wh / kg, but the ternary lithium battery could easily achieve the energy density of the battery system above 120wh / kg. This means that for the same battery capacity, the lithium iron phosphate battery weighs 25% or more than the lithium ternary battery.

Now, the lithium iron phosphate battery is getting the market's favor again, for no more than one reason - its energy density has been greatly increased, enough to meet the design needs of most automobile enterprises.

Taking Chery EQ as an example, although the new EQ uses lithium iron phosphate battery, and the endurance mileage under NEDC condition remains the same as the old one, reaching 301km, but its overall mass is reduced or not increased, only 966kg, 29kg less than the current one. All of this is attributed to the lithium iron phosphate battery. According to the data of the Ministry of industry and information technology, the energy density of its battery system has reached 140wh / kg, which has basically equalled the level of ncm523 and ncm622.

Perhaps many people will attribute the rejuvenation of lithium iron phosphate batteries to cost. Exactly! Compared with the ternary lithium battery, the cost of iron lithium battery is a little lower.

According to the data of national energy information platform, the current price of lithium iron power battery module is 0.76-0.8 yuan / wh, and the price of ternary power battery module is 0.9-0.95 yuan / wh, that is to say, each kilowatt hour, the former is about 100 yuan cheaper than the latter. If the battery capacity of Chery EQ is about 30 kwh, the cost of the whole vehicle can be reduced by 3000 yuan. It's a lot of money for a car that doesn't match up to 70000.

But if Chery EQ uses the ternary lithium battery with higher energy density - about 160wh / kg (this is also the average level on the market, and most of the independent brands at this level can achieve the endurance mileage of more than 400km), squeeze it together and increase the endurance mileage to 401km, which obviously helps it get higher policy subsidies - it can probably get more than the 301km version A subsidy of 7000 yuan. The final cost, I think the difference between the two is not very big, and even higher mileage EQ will be more cost-effective.

Therefore, I think that the reason why lithium iron phosphate battery returns to life is that the choice of technical route of pure electric vehicle by car enterprises has changed from performance orientation to safety orientation.

For a long time, in pure electric vehicles, every big car enterprise has a misunderstanding, that is, blindly pursuing the endurance mileage of pure electric vehicles, thinking that relying on high endurance mileage can solve the mileage anxiety problem of pure electric vehicle users. But in fact, the cause of this "disease" is not the mileage, but the convenience of charging. Just like my own gm8, even if the range of a tank of oil is only about 400km, I don't have any anxiety, because it's very convenient to refuel and can be solved in a few minutes. But not pure electric vehicles.

Behind the blind pursuit of endurance mileage, it must be at the cost of safety.

According to experts from the State Key Laboratory of automotive safety and energy conservation, the increase in mileage means an increase in the specific energy of the battery. The specific energy and safety are contradictory things. Generally, the battery with high specific energy is certainly more unsafe, because the electrochemical characteristics determine that it is more active, and the temperature point of the accident will become lower.

In fact, major car companies have gradually realized that consumers in the pure electric market are worried more about safety than about endurance mileage. Although there is no investigation agency to use data to explain all this, it seems that this can be verified by the "spontaneous combustion" that consumers must talk about when they open their mouth.

Some people say that the pure electric vehicle market is going backward. The lithium iron phosphate battery, the "old thing" that is about to leave the passenger vehicle market, can "revive" and reappear in the vision of consumers.

But I think it's a good thing, because now is the time to put things in order - pure electric vehicles should not have blind pursuit, such as charging speed, endurance mileage and too fast acceleration time, and should focus on safety, even if this point, consumers can't see.

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