Produced by Zhineng Automobile
Geely Automobile recently officially released the latest generation of self-developed and self-produced "blade" lithium iron phosphate batteries - Aegis short knife batteries.
Since BYD proposed the blade battery, Honeycomb Energy, ZEEKR and Volkswagen have actually continued to invest in the design of long batteries. On the whole, short knives (long prismatic batteries within 600mm) have shown their value in terms of safety performance, cycle life, fast charging capacity and low-temperature discharge, and are now expected to become the mainstream choice of power batteries for new energy vehicles in the future.
Part 1
Dimensions and features:
Key features of the Short Knife battery include:
◎ First of all, the size is smaller, and the length is 580 mm, which is about 40% shorter than the traditional long knife battery (960 mm).
◎ Superior structural design, shorter length, smaller internal resistance and low heat generation of the cell, which significantly reduces the safety risk.
◎ The battery adopts a wet double-coated separator, which is more flexible, not easy to break during puncture, and the damage aperture and short-circuit area are small.
◎ The battery coating is made of heat-resistant materials such as alumina, similar to adding an "isolation belt" between the positive and negative electrodes, which greatly improves the thermal shrinkage performance of the separator, so as to effectively prevent thermal runaway under severe conditions.
Let's sort out a few features:
● Fast charging feature
The direct characteristic from the change of size is the change of internal resistance. The Short Knife battery has ultra-fast charging performance, which can be charged to 80% in 17 minutes, with an average charge rate of 2.45C. This is due to its unique physical properties, smaller internal resistance, and the optimization and upgrading of the material system, which significantly improves the fast charging performance.
The battery uses carbon nanotubes with a thinner diameter and longer length, which makes the negative electrodes more tightly connected and provides a "highway" for ion transport. Additives with lower film-forming impedance are added to the electrolyte to reduce the diffusion impedance of lithium ions and make it easier for lithium ions to enter the negative electrode.
In contrast, if the battery is relatively long, the internal resistance is difficult to do, it takes 26 minutes to charge from 10% to 80%, the average charge rate is 1.61C, and due to the large internal resistance, it is easy to occur lithium precipitation, and the heat is also high.
● Security
Here, because lithium iron phosphate is used with thinner cells, it is relatively easy to needprick. Therefore, Geely's battery cell passed the "8 needles and puncture" test of the China Automotive Center, using 8 steel needles with a diameter of 5mm to puncture the battery cell at the same time, and let it stand for 1 hour, the battery cell did not smoke, did not catch fire, and did not explode.
In order to make the battery manifest safely, Geely also conducted six serial tests at the battery system level, including dynamic seawater corrosion immersion, extreme cold on the plateau, high-frequency bottom scraping, 26-ton overweight reciprocating rolling, single-pack side pillar collision and flame scorching.
This battery system is designed through the patented "Tianzi grid" frame, the overall mode is increased by more than 2 times, and the energy-absorbing cavity is added, and the battery cell and box reserve a large space for all-round protection. At the design level, it adopts multiple protection designs of liquid and electricity separation, electrical isolation, heat drainage, and thermal conduction. The bottom protection layer uses three-layer composite material + DP980 steel "sandwich" structure bottom guard plate with a thickness of 2.6mm, and a special battery anti-collision beam to reduce the damage when scraping the bottom in the forward direction.
● Cycle life
In terms of cycle life, 1500 cycles, 2500 cycles and 3500 cycles are good.
◎ Small size, small internal resistance, low calorific value: the internal chemical reaction speed is slowed down, which prolongs the battery life.
◎ Multi-element doping of cathode materials: improve energy density and ionic conductivity, stabilize material structure, and enhance cycling performance. The special coating technology further isolates the electrolyte, inhibits the dissolution of metal ions, reduces side reactions, and enhances electrical conductivity.
◎ Anode material optimization: small particle material is used to shorten the Li+ diffusion distance and increase the electrolyte wetting area. The amorphous carbon coating technology greatly reduces the electrochemical side reactions and ensures the cycling performance of the cell.
Jianhu Yaoning New Energy Technology Co., Ltd. and Guiyang Shanju Plant are the key production bases of Geely Aegis short knife batteries and battery packs.
◎ Jianhu Yaoning New Energy Technology Co., Ltd., located in Jianhu County, Yancheng City, Jiangsu Province, was established in July 2022 with an investment of 10.2 billion yuan, focusing on the manufacture of Aegis short knife battery cells. The industry-leading "multi-layer stator and rotor high-speed dispersion technology" has been introduced, which has significantly improved the pulping efficiency and created a pulping speed of 90 minutes/batch.
Its production process is fully intelligent, using AI intelligence and Internet of Things technology, equipped with more than 300 intelligent logistics equipment, and 100% automated operation. In terms of quality control, each production line is equipped with more than 6,000 quality control points and 1,000 sets of automatic testing equipment, using advanced testing technology to ensure product quality stability and safety.
◎ As the production base of Geely Aegis short knife battery packs, Guiyang Shanju Factory was established in September 2023 and will be fully put into operation in April 2024. Geely's new self-developed intelligent MES system is used in the factory to automate, transparent, and digitize the battery production process. In particular, we have made a breakthrough in the rapid changeover technology, which has shortened the changeover time of the battery pack line from the traditional 4 hours to only 6 minutes.
The factory's production line is designed to be compatible with a variety of battery pack models, and adopts an advanced AGV flexible conveyor system, which ensures a high combination of production efficiency and flexibility. In terms of quality control, the factory implements full-line quality control, and realizes intelligent and data-based management from incoming materials to final products to ensure the quality safety and maximum production efficiency of each link.
Part 2
Trends in short knife batteries
At this stage, it is a test of cost and complexity.
In the past design, square shell batteries often choose different cell sizes in the same model and different power configurations, resulting in the dispersion of cell standardization. The current trend is to unify the design of batteries, and by configuring different cell counts, it is possible to combine battery packs with different capacities. The more reasonable the selection of cells, the more suitable it can be for platformization. In the process of extreme cost reduction, it is very advantageous.
The short-knife battery, due to the relatively small number of adjustment parameters, can be unified and large-scale, and can be realized through very limited changes to achieve platform cells. This is a very promising path for the continuous cost reduction of batteries.
Here we see:
● When car companies enter the battery industry, they must reduce the complexity of the battery. Geely has launched its own battery brands on the Zeekr and Geely brands, but the overall design and production have been as unified as possible, so if you invest in the 46 series, the biggest challenge is that the results are uncontrollable. And around the short knife this series of investment, because there are some companies in the front of the pit, from preparation to the amount of climbing effect is better.
● The balance of performance, cost and life, we focus on the life characteristics, cost control and fast charging performance in this process, the length of the short knife 300-600mm can be designed with different schemes, and the overall balance can also get a satisfactory result.
We expect that this round of Chinese car companies entering battery production, most of them will be done around short knives, on the one hand, to avoid the patent problems of square shell batteries, but also to have some design flexibility.
brief summary
In China, the battery industry has entered a red ocean, and as we see the development of the entire battery industry in the next step, there will be many car companies that are vertically integrated and expand to other areas to spread the cost. We see this trend!