On June 27, Geely Automobile officially released the latest generation of self-developed and self-produced "blade" lithium iron phosphate batteries: Aegis short knife batteries. The battery energy density of this battery reaches 192Wh/kg, and the official said that the Aegis short knife battery has significant advantages in terms of safety performance, cycle life, fast charging capacity and low-temperature discharge. It is worth mentioning that the Geely Galaxy E5 will be the first to carry this Aegis short knife battery. Let's take a look at the technical characteristics of this Aegis short knife battery.
What are the characteristics of the cell structure of the short knife battery?
First of all, in terms of size, the size of the Aegis short knife battery is only 580mm, which is about 40% shorter than the traditional long knife battery, and this compact size design can provide more space layout flexibility for the vehicle.
Secondly, the internal structure of the battery has been optimized to achieve a shorter cell length and lower internal resistance. The lower internal resistance also means less heat is generated during charging and discharging, which not only improves the thermal management efficiency of the battery, but also reduces the safety risk caused by overheating.
Unlike dry separators, the inside of the short knife battery uses wet double-coated separator technology, which is more flexible, stable and not easy to break when subjected to external impact or puncture. This design significantly reduces the area of short circuits due to separator breakage, thereby improving the safety performance of the battery.
Finally, the Aegis Short Knife battery is coated with heat-resistant materials such as alumina between the positive and negative electrodes, which act as a strong "isolation belt" to prevent shrinkage and thermal runaway of the materials inside the battery when the battery is subjected to extreme conditions, such as pinprick tests. This coating not only improves the thermal stability of the separator, but also enhances the safety performance of the battery in the face of extreme conditions.
According to the official introduction, the battery cell of the shield short knife battery is 8 times higher than the national standard, and 8 steel needles with a diameter of 5mm are punctured at the same time and kept for 1h, and the battery cell does not smoke, fire or explode. How do these safety features work?
Aegis short knife batteries use a separator material with high heat resistance, which can remain stable in high-temperature environments and reduce the risk of thermal runaway. The substrate of the separator itself has a high heat resistance, which is further enhanced by a highly heat-resistant coating on the surface. This design not only improves the thermal stability of the diaphragm, but also combines the flexibility of the diaphragm base layer with the rigidity of the ceramic in the coating to form a "soft + hard" dual protection mechanism, which effectively resists mechanical impact or abuse from the outside world. In addition, the adhesive coating on the separator ensures that it is effectively combined with the positive and negative electrode sheets, which helps to maintain the stability of the internal structure of the cell and the uniformity of the interface.
The electrolyte is the medium for ion transport in the battery, and its stability is directly related to the safety performance of the battery. By increasing the content of inorganic components such as LiF and Li2O, the electrolyte of Aegis short knife battery significantly improves the stability of the SEI film of the cell. This improved SEI membrane is not only more stable and dense, but also further enhances the thermally safe performance of the SEI membrane by adding high levels of LiFSI and FEC to the electrolyte. These chemistries work together to form a tighter and more stable SEI film, effectively preventing thermal runaway from occurring.
In addition, the Aegis Short Knife battery uses an innovative self-fusing technology, which is a safety mechanism that automatically de-energizes the battery when it is subjected to extreme conditions such as pinprick attacks. By precisely designing the areal and compacted densities of the electrodes, combined with the high-strength separator, the battery is able to control the current during pinpricking, causing the aluminum foil to blow and cause the separator to collapse, forming an insulating layer that blocks short circuits. This design not only improves the battery's ability to protect itself under extreme conditions, but also significantly improves the safety level of the cell.
The Aegis short knife battery has passed the six "devil" serial tests of the China Automobile Center, including seawater surfing, extreme cold on the plateau, high-frequency bottom scraping, extreme crushing, side pillar collision of the battery pack, and blazing flames.
CTB battery pack configuration upgrade iteration
On the basis of the original Aegis battery safety system, the Aegis battery pack is further upgraded and iterated to adopt the CTB battery pack configuration. It is mainly reflected in the following aspects:
Structural strength improvement: Aegis battery pack adopts a patented "Tianzi grid" frame design, which can significantly improve the overall rigidity and mode of the battery pack by more than 2 times. This structural design, combined with the energy-absorbing cavity, provides a protective space similar to all-round protective armor for the battery cell, effectively resisting external shocks.
Multiple safety protection design: On the basis of the high safety performance of the battery cell itself, the CTB battery pack has added multiple safety protection measures such as liquid-electric separation, electrical isolation, heat dissipation and heat conduction. These designs not only ensure safe isolation between cells, but also optimize thermal management inside the battery pack to prevent overheating.
Enhanced bottom protection: The bottom of the battery pack is made of three-layer composite materials and DP980 high-strength steel, with a total thickness of 2.6mm, which provides strong protection for the bottom and effectively resists the impact of road obstacles. In addition, the front of the battery is also designed with a special anti-collision beam 15mm lower than the battery, which further reduces the potential damage to the battery pack by scraping the bottom.
Thermal runaway risk control: In order to quickly dissipate the heat inside the battery, the Aegis Short Knife battery is equipped with two explosion-proof valves, which ensure that the battery can quickly balance the internal and external pressure when subjected to thermal shock, and discharge the heat in time, greatly reducing the risk of battery explosion.
Intelligent security monitoring: As the world's first super cloud computing platform integrating "cloud, data and intelligence", Geely Star Intelligent Computing Center provides strong intelligent security support for Aegis short knife batteries. With a computing power of 10.2 billion times per second, the center can support the simultaneous online monitoring of up to 5 million vehicles, realizing round-the-clock monitoring of batteries, electric drives, and charging and distribution systems. Through cloud fault warning, online diagnosis and maintenance services, the intelligent safety system can identify and respond to potential vehicle safety risks in advance, thereby further improving the safety of users.
Lifespan: Can safely drive more than 1 million kilometers?
According to official data, the Aegis short knife battery has 1,500 cycles with a battery capacity retention rate of 92.12%, and 2,500 cycles with a battery capacity retention rate of 87.73%, which can safely drive more than 1 million kilometers. What improvements have been made in this area?
The first is the small size of the Aegis Short Knife battery and its low internal resistance, which means that less heat is generated when the battery is working. The low heat generation helps to slow down the chemical reaction inside the cell, thus effectively extending the life of the battery.
Secondly, the cathode material of the battery is optimized by multi-element doping technology, which not only improves the energy density of the cathode material, but also stabilizes the material structure and ion diffusion channel. This improvement increases the conductivity of the ions, enhancing the cycling performance of the battery. In addition, the special coating method provides additional protection for the cathode material, mechanically isolates the electrolyte, inhibits the dissolution of metal ions, and thus enhances conductivity and reduces side reactions.
In addition, the anode material is made of small particle material, which shortens the diffusion distance of lithium ions and increases the wetting area of the electrolyte, thereby improving the charging and discharging efficiency of the battery. The application of amorphous carbon coating technology greatly reduces the electrochemical side reactions of materials and ensures the performance of battery cells in recycling.
Super charged: Average charging magnification 2.45C
According to official data, the Aegis Short Knife battery has the ability to charge ultra-fast, which can replenish the battery power from 10% to 80% in only 17 minutes, and the average charging rate reaches 2.45C, which can effectively improve the user's charging experience. How?
As mentioned earlier, one of the physical characteristics of the Aegis short knife battery is that it has a small internal resistance. Internal resistance is the key factor of internal energy loss in the process of charging and discharging, the smaller the internal resistance, the higher the energy conversion efficiency. By optimizing the material system, the Aegis short knife battery significantly reduces the internal resistance, which not only improves the charging and discharging efficiency of the battery, but also reduces the heat loss during the charging process.
The carbon nanotubes used in the battery have a thinner diameter and longer length, which optimizes the connection of the negative electrode and provides a more unimpeded transport path for lithium ions. Figuratively speaking, this is like creating a "highway" for ion transmission, dramatically increasing the speed at which lithium ions can move inside the battery, thus speeding up the charging process.
In addition, additives with lower film-forming impedance added to the electrolyte help to form a more stable and dense SEI (Solid Electrolyte Interface) film on the surface of the negative electrode of the battery. This film not only protects the electrodes from decomposing the electrolyte, but also reduces the diffusion impedance of lithium ions at the negative electrode, making it easier for lithium ions to enter the negative electrode, further accelerating the charging speed.
Low temperature performance: The battery capacity is still above 90% at -30°C
The low-temperature resistance of Geely Aegis short knife batteries allows them to maintain excellent performance even in extreme cold environments, which is essential for the application of electric vehicles in winter or cold regions. To do this, there are several technical features:
Optimized charge conduction: The positive and negative electrode design of the Aegis short knife battery improves the efficiency of charge conduction, resulting in better discharge performance of the battery at low temperatures. This rapid charge conduction reduces the battery's energy loss in cold environments, thus maintaining a high discharge capacity.
Effect of battery thickness on heat retention: Compared to the long knife battery, the thickness of the Aegis short knife battery is 18.2mm, and this design helps to slow down heat loss during low temperature discharge. The thicker cell structure provides better thermal stability and helps maintain the internal temperature of the battery, thus maintaining battery performance even in extremely cold conditions.
Innovation of electrolyte additives: Aegis short knife batteries add low-impedance film-forming additives to the electrolyte, which can form a protective film with lower impedance on the electrode surface of the battery. This film can not only improve the charging and discharging efficiency of the battery, but also reduce the internal resistance of the battery under low temperature conditions, reduce the resistance of lithium ions when shuttling inside the battery, thereby improving the low temperature charging and discharging performance of the battery.
In addition, the production base of the battery was also shown at the press conference, which will not be expanded here, but in a nutshell, the battery cell production base is in the Yancheng Yaoning factory, using fully automatic equipment and AI intelligent technology to achieve 100% automated operation; The production base of the battery pack is in the Guiyang Shanju factory, which adopts the MES system to achieve automated, transparent and digital production.
Editor's Comments:
It can be seen that the new generation of Aegis short knife battery released by Geely this time has a lot of technical upgrade points, from the internal structure of the cell, the materials used to the structural protection of the battery pack, a series of upgrades have been made, making it have good performance in safety, overcharging, low-temperature performance and cycle life. This battery is newly installed on the Galaxy E5 model, how will it perform in terms of power performance, charging performance, and endurance in the real car? The answer soon came.