In the development of new energy vehicles, safety, especially the safety of power batteries, has always been a huge challenge. There were dozens of spontaneous combustion incidents of electric vehicles in the middle of last year, most of which were caused by power batteries. Therefore, overthrowing the blind pursuit of high energy density and returning to safety is the foundation for the healthy and sustainable development of power batteries.
In the domestic market, there are few vehicle companies that have mastered the power battery technology and have the ability of sustainable development. BYD, which started with batteries, can definitely be counted as a member.
On March 29th, BYD officially released the blade lithium iron phosphate battery, also known as the "blade battery". Compared with other power batteries, it is safer, longer in life and longer in battery life. Wang Chuanfu, chairman of BYD Group, also put down his rhetoric at the press conference: "Blade battery will completely erase the word' spontaneous combustion' from the dictionary of new energy vehicles."
To understand blade batteries, let's first understand CTP.
The full name of CTP technology is Cell? Where to? Pack, also known as modeless technology. In fact, at present, the battery packs carried by general electric vehicles are all assembled into modules by batteries, and then the modules are installed in the battery packs, forming a three-level assembly mode of "batteries-modules-battery packs". CTP integrates the battery cells directly into the battery pack, thus eliminating the intermediate module link.
The blade battery adopts CTP design, which improves the space utilization rate inside the battery pack shell from 40-50% in the traditional design method to 60-80%.
Specifically, the existing battery pack structure is usually composed of a single battery pack, and then the module is combined with BMS, power distribution module and other components to form a "battery pack".
CTP technology is to cancel the module and integrate the single battery directly into the battery pack. Thereby improving the space utilization rate in the packaging of the battery pack and increasing the battery capacity.
Blade electricity?
After understanding CTP, let's talk about "blade battery" in detail.
In essence, BYD's blade battery still belongs to the category of lithium iron phosphate battery. According to the official statement, CTP battery pack of contemporary Amperex Technology Co., Ltd. saves the assembly process of battery modules, and improves the volume utilization rate by 15%-20% and the energy density by 10%- 15%. BYD's lithium ferrous phosphate "blade battery" with GCTP packaging technology has also increased the "volume specific energy density" of the battery pack by more than 50%.
At the same time, according to BYD's patent, the brand-new "blade battery" adopts a long battery core with a square shell, and the battery core adopts a flat design, with a maximum length of 2.5 meters, which is more than 10 times that of the traditional lithium iron phosphate battery.
"blade battery" battery pack
Moreover, the blade battery also has a good performance in cost control.
The ternary lithium battery is named "ternary" because the cathode material contains nickel, cobalt and aluminum (NCA) or nickel, cobalt and manganese (NCM), in which "cobalt" is one of the essential metal elements. However, as a precious metal, cobalt is not abundant in China, and its cost remains high.
With the reduction of subsidies, the disadvantages of high cost of ternary lithium batteries will gradually emerge. For power batteries, which account for nearly 40% of the BOM cost of electric vehicles, improving the dependence of cathode materials on rare metals is the key development direction in the future.
In addition, the specific figures about the energy density of blade batteries were not mentioned at the press conference. The main reason is that Wang Chuanfu, chairman of BYD Group, said at the beginning of the conference that blade batteries are not for the pursuit of high energy density, but for safety as the primary orientation.
Personally, I guess that the mass and energy density of blade battery should be the same as that of ternary lithium battery (140 Wh/kg ~ 160? Wh/kg) is similar, which is lower than that of high nickel ratio ternary battery (160? wh/kg~ 180？ wh/kg).
Safety is the primary purpose.
When I introduced CTP above, I briefly explained the concept of canceling the module, so why must there be a "module" before?
There are modules, on the one hand, because the battery cell is protected and supported by the shell and the side beam, and it is relatively stable in the event of accidental collision; On the other hand, each module independently manages some batteries, which is helpful for temperature control, preventing thermal runaway (spontaneous combustion) and facilitating maintenance.
Traditional power battery pack
Without the blade battery of the module, if the side beam of the battery pack is removed, the battery unit will directly bear the impact of collision. How to ensure and improve security?
Blade battery fixes the battery cells on the frame of the battery pack, and each battery stack has about 100 battery cells, which not only solves the fixing problem, but also solves the strength problem. At the same time, it also draws lessons from the case of honeycomb aluminum plate, and sticks two high-strength plates on the upper and lower layers of the battery stack to further ensure the strength.
In addition, BYD played a video comparing three kinds of battery acupuncture tests on the day of the conference. "Puncture penetration test" is recognized in the industry as the most stringent test method for battery safety. This test requires a steel needle to pierce the battery core of the power battery, resulting in a large area of short circuit inside the battery core.
Under the same experimental conditions, the temperature of ternary lithium battery changed dramatically at the moment of acupuncture, and the surface temperature quickly exceeded 500℃, which led to extreme thermal runaway-violent combustion, and the eggs on the battery surface were blown up.
After the traditional lithium iron phosphate battery was punctured, there was no open flame and smoke, the surface temperature reached 200℃-400℃, and the eggs on the battery surface were burnt at high temperature.
There is no open flame and smoke after the "blade battery" penetrates. The surface temperature of the battery is only about 30-60℃, and the eggs on the battery surface are still in a flowable liquid state.
This result proves that the "blade battery" has completely got rid of the nightmare of "thermal runaway" that may occur in traditional power batteries, and its safety has great advantages.
Acupuncture experiment of three kinds of power batteries
Finally, it was revealed at the press conference that the blade battery was the first to be mounted on BYD pure electric vehicles, and it is expected to be mass-produced and released in Shenzhen in June this year. The cruising range of this model under comprehensive working conditions reaches 605 kilometers, and the acceleration of 100 kilometers is 3.9 seconds.
Byd Han EV
At the same time, as a power battery manufacturer, according to He Long, vice president of BYD Group and chairman of Foday Battery, "Almost all the automobile brands you can think of are discussing cooperation schemes based on blade battery technology with us. I believe that you will soon see and hear more exciting news about blade batteries, so it is very likely that there will be more different brands of vehicles equipped with blade batteries in the future.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.