"How to make batteries safer" has become a difficult question for major manufacturers to answer.
On August 20th, Lei Feng. Com had the honor to visit SAIC-GM Power Battery Development Center. As an important part of Buick brand's strategic layout of "electrification, networking, intelligence and enjoyment", the battery pack and battery pack production line of Buick Micro Blue 7 and Micro Blue 6 PHEV models have also been unveiled.
In fact, from 2065438 to April 2009, Buick has officially launched the Micro Blue 6 pure electric vehicle, which is Buick's first pure electric product in China. However, at that time, the battery capacity of this car was 35kwh, and the NEDC cruising range was only 30 1km.
In the past July, Buick launched the blue 6 PHEV, equipped with Buick's brand-new eMotin intelligent electric drive system. At the same time, the pure electric SUV micro blue 7 came out. Based on the general second-generation pure electric platform, it is equipped with a 55.6kwh battery pack, and the NEDC cruising range reaches 500km.
Unlike most car companies that simply buy batteries from battery suppliers for assembly, SAIC-GM is more inclined to deeply participate in battery research and development and cooperate with battery suppliers for a long time to develop batteries.
For example, the ternary lithium battery selected by Buick Micro Blue 7 and Micro Blue 6 PHEV mentioned above has further optimized the formula and design on the basis of LG chemical technology, so that the battery has higher energy density and longer service life.
Micro Blue 7 (left) and Micro Blue 6 PHEV (right) are equipped with a new generation of modular high-performance ternary lithium-ion batteries.
To some extent, abnormal temperature is one of the biggest causes of battery safety accidents.
In this regard, Buick Micro Blue 7 and Micro Blue 6 PHEV power battery systems all adopt GM's exclusive battery-level intelligent temperature management system, and are customized according to their respective structure, shape and performance requirements.
A heat conducting plate will be arranged between every two batteries of Micro Blue 7, which is directly connected with the water cooling structure at the bottom of the battery pack, and can realize active cooling or heating according to the working conditions of the batteries. The water cooling structure at the bottom of the battery pack adopts double-channel serpentine design, which is more conducive to the temperature management of the battery module. Moreover, the battery pack of Buick Micro Blue 7 also uses foam to isolate the heat dissipation between batteries, which alleviates the expansion of batteries during later charging, and there are potential safety hazards.
The blue 6 PHEV battery pack adopts laminated liquid cooling technology patented by General Motors. There is a heat conduction sheet with capillary liquid cooling tube between every two batteries, the thickness is only 0.2 mm, and the cooling liquid flowing in the capillary can accelerate heat conduction.
Light blue 6 PHEV battery radiator plate
According to reports, the temperature adaptation range of these two battery packs is -35℃~ 55℃.
In terms of materials, the power batteries of Micro Blue 7 and Micro Blue 6 PHEV are all made of lightweight composite materials, so the shape of the battery pack is small and light, and the sealed design of IP67 can ensure dust prevention and the safe operation of the battery pack when the vehicle wades.
A ribbed steel tray is also designed at the bottom of the micro blue 7 battery pack to reduce the damage to the battery pack caused by collision. As for the overall fuselage, Micro Blue 7 adopts a high-performance BFI integrated fuselage structure, and the application ratio of high-strength steel is as high as 78%, which also ensures the safety of the battery pack to a great extent.
GM China Yan Qian Technology Research Center-Battery Laboratory
During the whole day's visit, Lei Feng. Com visited two sites-GM China Forward-looking Technology Research Center-Battery Lab and SAIC General Power Battery System Development Center-PHEV Micro Blue 7 and Micro Blue 6 battery pack production lines.
First of all, talk about the battery lab. General Motors has independent battery laboratories in the United States and China. In these laboratories, it has established its own battery trial production line for battery prototype development and various types of testing and certification. Before each battery goes on the market, GM will conduct battery verification and testing in the battery laboratory for 3-5 years.
According to the staff, GM began to invest in the battery laboratory 10 years ago. At present, light blue 7 and light blue 6 PHEV batteries can pass various limit tests such as extrusion, collision, immersion, fire, overcharge, overdischarge, short circuit, salt spray and so on 10. In addition, the battery pack will undergo 100 system and vehicle tests, covering mechanical, thermodynamic, electrical, life and performance aspects.
SAIC-GM Power Battery System Development Center was established in Jinqiao, Pudong, Shanghai on 20 15, which is the second battery assembly center of GM in the world and the first outside North America.
SAIC general power battery system development center
The new generation of modular high-performance ternary lithium-ion batteries equipped with Buick Micro Blue 7 and Micro Blue 6 PHEV are assembled and produced here.
In the process of battery cell stacking and battery module assembly, the whole process of battery and module charging, assembly, transportation and battery module testing is intelligently completed by robots or manipulators, and the automation rate reaches100%; Moreover, the accuracy of the robot in each feeding/discharging/handling process is within 0.65438 0 mm.
According to the engineer, there are not many manual inspectors in the whole production line, who are only responsible for correcting the misoperation of the machine. However, these two production lines are not busy at this stage, and even stopped working on the afternoon of Lei Feng's visit.
Through the application of digital technology, the key components of Micro Blue 7 and Micro Blue 6 PHEV not only realize real-time data collection, monitoring and early warning in the assembly process, but also have their own "ID cards" through a complete product information traceability system.
For example, a two-dimensional code will be printed on the outer packaging of batteries that have been operated correctly, and only these batteries with two-dimensional codes can go offline. In addition, by scanning the QR code, the battery unit can accurately trace back to when, where and by whom the product passed.
Another technical highlight is ultrasonic welding. The engineer explained to us that using ultrasonic technology to weld the battery cell tab has no welding defects and will not cause high-temperature pollution and damage to semiconductors such as aluminum and copper, thus reducing the risk of tearing the tab.
Ultrasonic tab welding
Specifically, the technology is precisely positioned by the industrial robot under the guidance of the vision system, and the ultrasonic welding head is automatically manipulated to complete the welding of the positive and negative tabs of the battery cell, so that the battery module forms a path. In addition, different ultrasonic welding techniques can be used for different materials.
In addition to batteries, the safety test and evaluation of modules and battery packs can not be ignored. In order to ensure that Buick Micro Blue 6 PHEV's liquid-cooled heat-conducting fin and Micro Blue 7' s liquid-cooled loop system have no leakage points, the module assembly line will adopt mass flow method for leakage detection, which will improve the detection accuracy and shorten the detection time.
In terms of module welding quality inspection, if there is false welding or missing welding in equipment welding, manual repair welding is used for on-site repair welding. As the engineer said before:
In fact, GM's investment in new energy is far more than that.
As early as 1996, GM introduced the pure electric vehicle EV 1, making GM a real pioneer in the field of electric vehicles. However, due to the bad timing and immature market environment, GM basically "abandoned" electric vehicles in the next decade.
Although GM began to increase investment in research and development of pure electric vehicles in recent years, only from the Buick Micro Blue 6 released last year, the cruising range of NEDC is only 30 1km. Four months later, GM once again launched a brand-new model, Micro Blue 6 pure electric version, and its cruising range has also increased to 465,438+00 km. Today, electric vehicles have become the mainstream, and many new forces have broken through the 600 km cruising range.
However, GM recently announced the launch of Ultium battery system and the third generation global electric vehicle platform. Buick Micro Blue 7 and Micro Blue 6 HEVP are also equipped with a new generation of modular ternary lithium batteries-GM is also a good step.