"Non-spontaneous combustion" automobile power battery: Why blade? Why doesn't a flat tire burst?

"New energy vehicles equipped with blade batteries will completely erase the word' spontaneous combustion' from the dictionary of new energy vehicles," said Wang Chuanfu, president of BYD Group, at the blade battery conference on March 29th. Blade batteries will change the industry's dependence on ternary lithium batteries and lead the technical route of power batteries back to the right track.

Through the blade battery, BYD refreshed the energy density of lithium iron phosphate battery and tied the mainstream level of ternary lithium battery; Through the acupuncture experiment, the blade battery showed unusual "calmness" and became the only power battery that could pass this rigorous test.

After years of competition and elimination, the power batteries of electric vehicles have evolved from competing for the top two, ternary lithium batteries have become the mainstream of passenger cars, while lithium iron phosphate batteries have firmly controlled the bus and bus market.

The logic behind it is that ternary lithium batteries have higher energy density, which can support better endurance performance and get policy subsidies, which is stimulating the enthusiasm of car companies to load cars; Lithium iron phosphate battery has better safety and longer service life, and is the best choice for buses and buses with large passenger capacity and high working intensity.

After the emergence of a new generation of "blade batteries" in the lithium iron phosphate camp, what impact will ternary lithium batteries suffer? Will the passenger car market it controls fall to the lithium ferrous phosphate camp?

Why the "blade"?

BYD super lithium ferrous phosphate battery (commonly known as battery cell) is called "blade battery" because of its flat and long shape.

Through the blade battery conference and related patent documents, we can see BYD's idea of improving the energy density of lithium iron phosphate battery.

Blade battery is actually the product of CTP, the so-called CTP(Cell? Where to? Pack) refers to the direct assembly of single batteries (batteries) into a battery pack, while the internal structure of traditional battery packs is complex, so it is necessary to assemble several batteries into modules first, and then assemble several modules into a battery pack.

In the traditional battery pack, it is necessary to set several longitudinal beams and transverse beams to fix the battery module and strengthen the strength of the battery pack. The crisscross battery module housings and reinforcing beams in the battery pack will occupy a lot of space. According to He Long, vice president of BYD Group and chairman of Foday Battery, at the blade battery conference, the space utilization rate of traditional battery pack is only about 40%, while the blade battery saves two links of module and reinforcing beam, and the space utilization rate is increased by 50%. In other words, the space left for batteries in the battery pack can reach 60%.

Why is the blade battery so long? According to the relevant documents of BYD's battery invention patent application, the length of blade battery can be between 600 mm and 2000 mm, far exceeding that of ordinary lithium battery cells. The length of the battery cell can be customized according to the size of the battery pack. Due to the sufficient length, both ends of the battery cell can "reach" the peripheral frame of the battery pack and be directly fixed on the side beam.

Why is the blade battery so flat? It is explained in the related patent literature that flattening the battery cells can increase the effective heat dissipation area and improve the heat dissipation efficiency.

Why can batteries replace longitudinal beams and transverse beams? Patent documents show that this kind of battery is a hard-shell battery, and the shell is made of steel or aluminum, which can support itself. When the batteries are arranged side by side in the battery pack, they can replace the reinforcement structure to ensure the structural strength of the battery pack, thus using less or even no longitudinal beams and beams.

According to He Long's introduction at the press conference, the core of the blade battery is both an "energy body" and a structural part, and the structure of "honeycomb aluminum" is used for reference, and high-strength structural plates are bonded on the upper and lower sides of the battery array, so that the strength of the blade battery pack is "increased" compared with the traditional battery pack.

This design will undoubtedly greatly improve the "volume specific energy density (watt-hour/liter)" of the battery pack, that is to say, more batteries can be put into the battery pack of the same size, thus carrying more electricity.

The power battery pack of electric vehicles is usually arranged between the front and rear axles on the chassis, and its length, width and thickness are limited. Compared with ternary lithium batteries, the bulk lithium iron phosphate batteries have lower energy density, so it is difficult for the traditional bulk lithium iron phosphate batteries to support the battery life of electric vehicles for more than 400 kilometers. According to the data provided by BYD, the volume specific energy density of the battery pack with blade battery structure is increased by 50%. BYD's "Han" model equipped with blade batteries is expected to be launched in June, with a battery life of 605 kilometers, which is basically equal to the advanced level of ternary lithium batteries.

According to the description in related patent documents, the volume utilization rate of blade battery pack can be further improved. "This design can increase the space utilization rate from about 40% to more than 60% or even higher.

In the field of ternary lithium batteries, CTP technology of directly packaging batteries is also being promoted, but the promotion range is obviously different from that of blade batteries. According to the data of contemporary Amperex Technology Co., Ltd., the volume utilization rate of CTP ternary lithium battery pack can be increased by 15%-20%, and the energy density of battery pack can be increased by 10%- 15%.

What does acupuncture stand for?

In addition to the significant increase in energy density, BYD blade batteries also show amazing safety.

It is reported that BYD Blade Battery has recently completed the most difficult "acupuncture experiment" in the field of power battery testing, which is also the first power battery to pass the acupuncture experiment.

The acupuncture experiment of single battery is to pierce the battery with a steel needle with a diameter of 5mm-8mm, and the steel needle stays in the battery for one hour to observe. Penetration of conductive steel needle into the battery will lead to short circuit inside the battery, which may lead to rapid release of heat out of control, and then lead to fire and deflagration? . Because it is too difficult, no ternary lithium battery can pass this test at present, and the new national standard "Safety Requirements for Lithium-ion Power Batteries for Electric Vehicles" (draft for comment) even canceled the acupuncture experiment.

At the blade battery conference on March 29th, BYD released a complete video of the comparative acupuncture experiment of ternary lithium battery, traditional lithium iron phosphate block battery and blade battery. The video shows that the ternary lithium battery "explodes at once" and burns violently within two or three seconds. When the surface temperature exceeds 500 degrees Celsius, the eggs placed on the surface of the battery are blown up; The traditional lithium iron phosphate battery has smoke, but no open flame. The surface temperature is 200-400 degrees Celsius, and the eggs on the battery surface are burnt. However, the blade battery has no smoke and open flame, the surface temperature of the battery is only 30-60 degrees Celsius, and the eggs on the battery surface have not changed.

According to Gao, an academician of Chinese Academy of Sciences and professor of Tsinghua University, the reason why the blade battery can pass the acupuncture experiment is that the strip battery has a large heat dissipation area; On the other hand, the short-circuit time of the battery is long and the calorific value is low, which determines that the temperature rise rate of the blade battery is small.

Due to frequent fire incidents, the safety of electric vehicles is questioned. According to a report released by china automobile dealers association, nearly 30% of consumers are worried about the safety of batteries, so they give up buying electric cars.

According to the research of the National New Energy Vehicle Big Data Alliance, among the identified causes of electric vehicle fires, battery problems account for the highest proportion, reaching 58%; According to CEVE, in the fire accident of 20 19 electric vehicle, ternary lithium battery vehicle accounted for 60%, and lithium iron phosphate battery only accounted for 5%.

Ternary lithium batteries have high energy density. In the "endurance race" of passenger cars in recent two years, ternary lithium batteries have become the mainstream choice of automobile manufacturers. However, the poor thermal stability of ternary lithium batteries, especially the pursuit of better data by manufacturers, has promoted the rapid "high nickel" of ternary lithium batteries (the cathode material of ternary lithium batteries contains nickel, cobalt and manganese, and increasing the proportion of nickel can improve the energy density, but the chemical stability of batteries will decrease), and the safety risk will further increase.

BYD's blade battery passed the acupuncture experiment, which means that through technological innovation, lithium iron phosphate battery has achieved higher product stability and lower failure rate. Will the blade battery that "erases spontaneous combustion from the dictionary of new energy vehicles" have a subversive impact on the passenger car market controlled by ternary lithium batteries?

Wang Chuanfu said at the press conference that the unrealistic pursuit of battery energy density completely "biased" the development route of the power battery industry, which made the safety reputation of new energy passenger cars pay a very heavy price; The release of the blade battery is "correcting the deviation", which not only completely solves the safety pain point of the new energy automobile industry, but also forces the whole industry to make changes.

Regarding the application prospect of blade battery and its impact on the industry, He Long, chairman of Foday Battery, revealed that "almost all the automobile brands you can think of are discussing with us the scheme based on blade battery technology cooperation". ? Text/Great Wall New Media Reporter? Fu Xuefeng

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