Author? fruit juice

Editor? Han Xiao

In June 5438+10, Tesla changed the car model by replacing the iron phosphate battery. The starting price of 3 dropped from 276,5438+0,000 to 249,000, which ushered in a new wave of sales climax.

However, the new car owners who "got a bargain" have not been happy recently.

A few days ago, many iron phosphate models in the north. 3 car owners spit on the internet, saying that their car's power is declining, the charging speed is slow, and even there is a large-scale power outage for no reason.

The above phenomenon will eventually lead to a result-battery life will shrink. The most exaggerated thing is that some car owners even claim that the battery life will shrink by 50%. Similarly, BYD Han and Wuling? Hong Guang Mini? Owners of iron phosphate cars such as electric cars are also complaining about this problem.

Some people even joked that when winter came, electric cars really became "electric dads".

However, it should also be noted that although lithium iron phosphate batteries have been criticized in winter, Tucki G3 still replaced lithium iron phosphate batteries in the latest batch of new car catalogues of the Ministry of Industry and Information Technology. Previously, Roewe and BAIC electric vehicles also introduced lithium ferrous phosphate versions.

Lithium iron phosphate battery has become a love-hate existence for car companies.

So what effect will low temperature have on iron phosphate vehicles? What is the reason behind it? Why do car companies insist on replacing iron phosphate batteries when they know that the low-temperature performance of iron phosphate is poor? Che Dongxi found the answer after communicating with many battery industry experts.

1. iron phosphate model? 3 battery life has shrunk by half? The owner of the car keeps spitting.

Every winter is a time for electric car owners to worry collectively. With the continuous decrease of temperature, the performance of power battery will be greatly affected. This year, this discussion is particularly enthusiastic, and it is Tesla that heats up this discussion.

In June this year 10, Tesla officially released the lithium ferrous phosphate version Model? 3。 This version of the model quickly boosted Tesla's sales after its launch. According to the association data, 1 1 month, Tesla model? More than 265,438+0,604 vehicles have been sold, and only Tesla can sell about 250,000 to more than 20,000 electric vehicles.

The sales situation of new energy vehicles in China announced by Cheyou Federation 1 1.

The cost advantage brought by the lithium ferrous phosphate version is very obvious, but there are also some risks. As we all know, the performance of lithium iron phosphate batteries has been poor in winter, which has also become a place where car owners criticize.

Recently, the temperature in Beijing has fallen below zero, and the temperature in most parts of the north is below 5 degrees. Some of them have purchased the Tesla lithium iron phosphate Model. 3% car owners began to collectively spit out the battery problems of their vehicles online.

At the car home forum, the car saw a picture released by a car owner showing his car model? The cruising range of the watch is 352 kilometers after being fully charged and 379 kilometers after being charged again.

Explain that the battery life has shrunk after charging.

At present, Tesla officially marked the lithium ferrous phosphate version? The NEDC cruising range of the 3 is 468 kilometers, but the mileage displayed on the car is EPA cruising range, and the cruising range of a fully charged vehicle is about 465,438+08 kilometers.

That is to say, the endurance of this owner's vehicle has directly shrunk by 10% ~ 15%. In subsequent posts, the car also found that some users expressed their models. After fully charged, the cruising range is 372 kilometers, which is similar to that of the owner above.

It shows that the battery life has shrunk to 372 kilometers after the charging is completed.

However, in the comments below, Che Dong saw a user comment that "it is full of (electricity) 306 kilometers today". According to this user, his vehicle life has shrunk by 27%.

User comments screenshot

Judging from the expressions of these users, what is the model of lithium ferrous phosphate? There is indeed capacity shrinkage at low temperature, but the extent of shrinkage is not equal, and it has different performances at different temperatures. In addition, the different driving habits of car owners also affect the real endurance of vehicles. Some car owners said on the Internet that the real endurance of vehicles has even shrunk by about 50%.

On the post of a car owner, the car also saw another phenomenon, that is, after the car has stood still for a period of time, its battery life will decline in a cliff-like manner. According to the owner, his vehicle lost 30 kilometers and 40 kilometers of battery life for two consecutive nights.

Netizens spit out the cliff-like decline in vehicle life.

Car colleagues also said his model? In the owner group, there is also a similar situation in which the owner of the lithium ferrous phosphate version vomits. When the owner arrived at the company by car in the morning, the cruising range was still 160 km, and when he went to drive again, it was only 100 km.

From the feedback of the two car owners, what is the lithium ferrous phosphate model? The battery life of 3 does have a "cliff-like decline".

In fact, this situation is essentially the performance of the power drop, but when the user just fully charged, the vehicle has not detected the power drop, so the displayed number has not changed. After driving for a period of time, the vehicle reads the correct electricity information and suddenly loses the number, thus causing the above-mentioned "cliff-like" power failure.

In addition to the decline in capacity, the car also found an obvious problem, that is, the lithium iron phosphate version of the car will charge slowly in winter.

Automobile supplies, models of colleagues? 3 using ternary lithium battery, he said that the vehicle is charged with Tesla super charging pile, and the initial charging power can reach above 80kW. With the increase of charging amount, the charging power will gradually decrease.

Ternary lithium battery version model? 3 The power in the final stage of charging is still 24kW.

However, the car saw a picture uploaded by a car owner on the forum, showing that the charging power was only 64kW at the initial stage of charging. The data on the picture uploaded by another car owner is even more exaggerated. The picture shows that the vehicle charging is still in the primary stage, but the charging power shown is only 25kW, which is quite different from that of the ordinary ternary lithium battery.

Lithium iron phosphate battery model? Just started charging, the battery life is only 25kW.

However, this situation only appears in the northern region. There are lithium ferrous phosphate models in Shanghai. The owner said that the cruising range of each full charge is 425 ~ 4 19 km, and there is basically no deviation in the cruising range without heating the seat.

Does the car material colleague also have a model? 3. It is a ternary lithium battery version. When the battery is charged to 90% in summer, the instrument shows a battery life of 333 kilometers, and when it is charged to 90% in winter, the instrument shows a range of 327-33 1 kilometer. It can be seen that in the weather around 0 degrees, the battery attenuation is very low.

In fact, in cold weather, the battery life of lithium iron phosphate battery will always shrink. Even BYD blade battery, the master of lithium iron phosphate battery, suffered the same fate.

A BYD user said at the forum that his BYD Han's cruising range in Beijing has been reduced by 60%. Some netizens commented that 60% discount is reliable, but now the temperature in Beijing has not reached the coldest time. The implication is that the temperature will drop further and the cruising range will continue to shrink.

Screenshot of Beijing BYD Korean car owner's message

BYD auto executives said in reply to netizens that "normal winter is more than 400 kilometers". This figure has a certain gap compared with the official announcement of 605 kilometers, which is also the official recognition of the problem of shrinking battery life.

Weibo, an executive of BYD Auto, responded to the battery life problem.

Hong Guang MINI, which created a sales miracle this year? EV has been plagued by the same problem. Some car owners reported that the original cruising range should be 170 km, and now the cruising range is less than 100 km. Some car owners even said that the cruising range has not even reached 85 kilometers, and the cruising range has shrunk by more than 50%.

From the above example, it is not difficult to see that the battery life shrinkage of lithium iron phosphate battery still exists in winter, and with the gradual decrease of temperature, the shrinkage situation is becoming more and more serious, which is not good news for the lithium iron phosphate battery that has just been revived this year.

Second, the shortcomings of lithium ferrous phosphate? Low temperature performance attenuation is inevitable.

So, what causes the performance of lithium iron phosphate battery to drop significantly at low temperature?

Che Dongxi found the answer after communicating with many practitioners in the power battery industry.

First of all, let's understand the composition and working principle of lithium iron phosphate battery. The anode material of lithium iron phosphate battery is lithium ferrous phosphate and the cathode is graphite. The charging and discharging process is a repeated process of lithium ion insertion and extraction. When charging, lithium ions escape from the cathode material, enter the electrolyte, and then move to the negative electrode of the battery through the polymer diaphragm and are embedded in the graphite lattice.

During discharge, lithium ions escape from the graphite lattice into the electrolyte, move to the positive electrode of the battery through the polymer diaphragm, and are embedded in the iron phosphate lattice.

After understanding the working principle of lithium iron phosphate battery, we are looking at why lithium iron phosphate battery has poor performance at low temperature.

Ferrous lithium phosphate?

In the above process, the cathode material of the battery is very important, which determines the performance of the power battery, but the cathode material of lithium iron phosphate battery has certain characteristics.

Gao Xiang, a researcher at Beijing High Voltage Science Research Center, told Che Dongxi that compared with ternary lithium battery (the cathode material is ternary lithium), the conductivity of the cathode material of iron phosphate battery is relatively weak, and this weakness will be more prominent at low temperature.

Albert Lin, technical support director of Honeycomb Energy, also said: "The crystal structure of olivine, the cathode material of lithium ferrous phosphate, has fixed defects, and its capacity and working voltage are poor at low temperature."

Gao Xiang also introduced another possible factor to Che Dong, that is, the liquid electrolyte has poor fluidity at low temperature, and the diffusion speed of lithium ions in the electrolyte is relatively slow. However, liquid electrolyte is easy to reduce its fluidity at low temperature in winter, so the power battery under liquid electrolyte system will be affected by low temperature at present.

The reason of cliff power failure is mainly related to the monitoring of batteries by vehicles, which is also a difficult problem in the field of lithium iron phosphate batteries. Albert Lin told riders that the discharge voltage of lithium iron phosphate battery is very flat, and the power is difficult to monitor. In the actual use process, the current is high and low, and the monitoring is inaccurate.

Due to the time-consuming monitoring of vehicle system, the apparent mileage of vehicles will drop sharply.

Zhu Yulong, a well-known expert in the field of new energy and automotive electronics, said in his analysis article that Tesla Model? The initial strategy is aimed at ternary lithium batteries, and there will be some errors after replacing lithium iron phosphate batteries. The problem of cliff-like falling mileage may also be related to strategies such as sentry mode. Due to the dual influence of SOC estimation error and static power consumption, power consumption decreases obviously.

Lin Yumin also answered the question of slow charging of lithium iron phosphate batteries. He said that lithium iron phosphate batteries are relatively low in price and may not have heating function. At low temperature, the charging strategy will reduce the current, and the anode material will easily precipitate lithium at low temperature, so it is necessary to reduce the current to protect the battery, which will lead to the corresponding slow charging of lithium iron phosphate battery.

After understanding this characteristic, we also need to know at what temperature will the performance of lithium iron phosphate batteries begin to deteriorate?

Gao Xiang said that when general car companies and battery companies announce the battery performance, they all use the room temperature of 20 ~ 25 degrees Celsius as the benchmark, that is to say, as long as it is lower than this temperature, the battery performance will decline.

Between 0 and 20 degrees Celsius, the performance decline of lithium iron phosphate battery is linear; When the temperature drops below zero, the performance of lithium iron phosphate battery will drop precipitously, and the cruising range may drop by more than 50%. When the temperature is lower than-10 degrees, the lithium iron phosphate battery may not work at all.

Lin Yumin also said: "Under normal circumstances, when the temperature is lower than 10 degrees Celsius, the performance of lithium iron phosphate battery will be discounted."

At present, the temperature in Beijing has fallen below 0 degrees Celsius, and the temperature in many parts of the country is also below 10 degrees Celsius. If the model equipped with lithium iron phosphate battery is frozen outdoors for one night, the battery performance will inevitably decrease.

The temperature in Beijing has dropped below zero.

Gao Xiang said: "At present, the performance of power batteries with liquid electrolyte system will be discounted at low temperature in winter." Albert Lin also believes that it is difficult to overcome the short board of lithium iron phosphate battery based on the existing production technology.

Lin Yumin also thinks that the effect of using nano-scale iron-lithium materials will be slightly better, but it will also bring new problems. The most intuitive thing is that nano-scale materials will directly increase the cost of batteries, so that the cost advantage of lithium iron phosphate batteries will be lost. What is embarrassing is that even if nano-scale lithium iron materials are used to increase the cost, the performance in winter is still worse than that of ternary lithium batteries.

Generally speaking, lithium iron phosphate battery still has the problem of poor performance in winter, and there is no proper solution at present, and it may continue to exist in the future.

Third, Tucki G3 pushes the version of lithium ferrous phosphate? The fever is still unabated.

Although lithium iron phosphate batteries have a big problem in winter, the upsurge of replacing lithium iron phosphate batteries by car companies has not stopped this year.

Just recently, a lithium ferrous phosphate model-lithium ferrous phosphate version of Tucki G3 appeared in the 339th batch of road motor vehicle manufacturers and product announcements published by the Ministry of Industry and Information Technology. Since the beginning of this year, BYD, Tesla, Roewe, BAIC and other car companies have also launched models equipped with lithium iron phosphate batteries.

Knowing that the capacity of lithium iron phosphate battery will shrink in winter, they still choose this battery. What do these car companies think?

There may be three reasons for the car:

The first is to reduce costs. The lithium iron phosphate battery used in Tucki G3 is provided by Contemporary Amp Technology Co., Ltd., which is similar to Tesla model? Three is the same. Being able to attract Tesla and Tucki at the same time is also inseparable from the cost control of Contemporary Ampere Technology Co., Ltd.. According to some media, the cost per kwh of lithium ferrous phosphate module of Contemporary Amp Technology Co., Ltd. has dropped below that of 500 yuan, and the cost per kwh of battery pack will be below that of 600 yuan.

Domestic Tesla models? three

According to the data of UBS Group AG, an international investment analysis organization, the current price of ternary lithium battery in China is about 1 1,000 yuan per kwh. After adopting lithium iron phosphate battery, the bicycle cost of car enterprises can be reduced by more than 20 thousand yuan, and the price of the whole car can be further reduced, thus bringing greater competitiveness. Tesla model? 3 is the best example, the price has dropped from 279,000 to 249,000, which is just over 20,000.

When BYD released the blade battery, it also said that the cost per kilowatt hour of the battery has also dropped to around 500 yuan, and the price per kilowatt hour of the battery pack is expected to be around 600 yuan.

Because of this, car companies "know that there are tigers in the mountains and prefer to go to the mountains" and take the initiative to choose lithium iron phosphate batteries.

Secondly, although lithium iron phosphate batteries will be greatly affected at low temperature, the impact in the southern region is not too great.

The model from the southern version of lithium ferrous phosphate? It can also be seen from users' comments that the temperature in the south is not as high as that in the north, so the endurance of its vehicles has basically not been greatly affected.

Shanghai LiFePO4 Tesla owner message screenshot

Albert Lin also told Che Dongxi that in South China or Southeast Asia, the inherent low-temperature shortcomings of lithium iron phosphate batteries will not appear directly.

Therefore, for southern users, there is no difference in specific performance between lithium iron phosphate battery and ternary lithium battery, but lithium iron phosphate battery is cheaper, which is also a good choice for many southern users.

The existence of this market has also given car companies the confidence to replace lithium iron phosphate batteries.

In addition, although there is no way to improve the low-temperature performance of lithium iron phosphate battery in terms of battery materials, some car companies are improving the winter performance of lithium iron phosphate battery through other methods, the main method is to keep the battery warm.

Some car companies directly wrap insulating materials in the battery pack, which further improves the thermal management system of the battery and can further reduce the power consumption of battery heating.

There are also some car companies that use hybrid heating of oil and electricity to heat vehicles, and use the heat generated by fuel to maintain the battery temperature and increase the battery life.

Generally speaking, although there are some problems in lithium iron phosphate batteries, after years of market education, many car owners have certain psychological endurance. In addition, lithium iron phosphate batteries can indeed bring lower prices, and car companies have begun to pay more attention to lithium iron phosphate batteries.

Conclusion: There is still a long way to go in the field of power batteries.

Low temperature weather is unfriendly to all kinds of cars, and electric vehicles are more affected by low temperature. Whether it is ternary lithium battery or lithium iron phosphate battery, the performance in winter will be discounted.

At present, the temperature in the north is generally around zero, and some electric car owners of lithium ferrous phosphate complain on the Internet that their car life has shrunk seriously, even by more than half. The performance of ternary lithium battery is not so serious.

This has also caused lithium iron phosphate batteries to fall into the whirlpool of public opinion again. However, some car companies insist on choosing lithium iron phosphate batteries. Compared with ternary lithium battery, lithium iron phosphate battery has better safety and lower cost. In order to reduce the cost, many car companies have chosen this battery, but its poor performance and low energy density in winter are also one of its natural shortcomings.

The use of ternary lithium batteries will also have problems of high cost and low safety.

For car companies, no matter whether they choose ternary lithium battery or lithium iron phosphate battery, they will face certain risks, which also shows that the current power battery technology is far from mature and there is still a long way to go.

This article comes from car home, the author of the car manufacturer, and does not represent car home's position.