Author: Kaijun Qiu
Editor: Kaijun Qiu
When Honeycomb Energy made its debut, it declared that it would take the world by storm with its stacking technology in the age of stacking. Ever since, VDA batteries and MEB batteries have also been stacking.
At the 2021 Honeycomb Energy Battery Day, the company announced that it would “short sword” its entire range of batteries. The so-called “short sword” refers to a thin, elongated rectangular shell battery with a maximum length of about 600mm.
It is difficult to align such long battery cells when stacked. Is it still possible to stack them?
Yes, it is still possible.
Moreover, the speed needs to be increased to compete with most rectangular shell battery factories’ winding process.
Can this really be achieved?
On February 25, I had the opportunity to visit the “short sword” production line at Honeycomb Energy’s Changzhou Phase II factory and witness the production process of “short sword” batteries. After that, I also had discussions with Honeycomb Energy’s Chairman Yang Hongxin and other executives about battery research and production.
“The ‘short sword’ production line is much more advanced than all other battery production lines around the world… we are very confident about the production line and can produce high-quality batteries,” said Yang Hongxin.
After successfully developing and producing the first generation of “short swords,” Honeycomb Energy will continue to make improvements to “short swords”: higher energy density, higher rate capability, and more abundant materials, to respond to the sustained challenges of domestic and foreign competitors.
Many people think that power battery companies like Honeycomb Energy are just manufacturers without any technological content. However, under the national strategic emerging industry, Honeycomb Energy has been competing at the global forefront of technology with the development of cobalt-free batteries and other new products, research and application of stacking technology, machine vision, artificial intelligence, and other new technologies, catering to the thriving demand of the battery market.
Both research and production are tools of hard technology, which is also the core driving force behind Honeycomb Energy’s rapid growth.
“Short sword” yield rate approaches 90%
Honeycomb Energy was founded in February 2018. Its first factory was established in Changzhou, and the first-phase construction was completed at the end of 2019. In the third quarter of 2021, the second-phase construction was also completed and put into operation. The speed was very fast.
Among the 8GWh capacity of the second phase, Honeycomb Energy attaches great importance to the “short sword” production line, which aims to meet the demands of the passenger car, commercial vehicle, energy storage, and other markets.
“Short sword” is undoubtedly a strategic product for Honeycomb Energy.
Compared with BYD’s blade battery, Honeycomb Energy’s “short sword” is also a thin, elongated aluminum shell battery, but its length is shorter, less than 600mm, while the blade of BYD can reach 960mm.BHEV believes that the “Short Sword” has almost all the advantages of blade batteries: high volumetric energy density, can be used as a structural component to reduce costs, easy to dissipate heat, and good safety performance.
In addition, because its length is not too long, it can adapt to more than 80% of passenger cars, including the MEB module promoted by the Volkswagen series, and is also suitable for energy storage. Moreover, the production process is easier to achieve, achieving a higher yield of qualified products.
All of this is theoretical deduction. Can BHEV, established only in 2018, really make a 600mm long cell?
The task falls on Phase II of BHEV’s Changzhou factory.
In the third quarter of 2021, BHEV’s Changzhou Phase II factory was put into production, capable of producing three types of batteries: VDA, MEB, and “Short Sword”.
Regardless of which battery, the production process is generally similar, divided into slurry coating, coating, rolling, slicing, stacking (or winding), assembly, injection, formation, etc.
General production process of battery cells
Regarding the “Short Sword” category of BHEV, the difficulties lie in coating, rolling, die cutting, and stacking processes. Because the length reaches nearly 600mm, the surface density and alignment of the coating have great difficulty. The die cutting process is similar and must be cut very accurately. In the stacking process, it must be stacked quickly and evenly.
In the coating section, we visited the positive electrode coating process. The coating machine in this process can coat two columns of 1.4 meters each. Liu Xiaoan, Director of BHEV and Senior Technology Director, said that this is one of the widest coating machines in the industry.
The evaluation of the coating process mainly depends on three indicators: speed, surface density, and the accuracy of the coating position. The level that the coating process of the “Short Sword” can achieve is: coating speed up to the level of 80 m/min, coating surface density control within ±1.5%, and the alignment deviation of the coating front and back ≤0.5 mm.
Liu Xiaoan said that all these indicators are the best level in the industry.
After the coating, the electrode sheet needs to be rolled to ensure that the positive and negative electrodes and the substrate are tightly bonded and achieve high energy density. The “Short Sword” sheet’s electrode sheet is very long, and the rolling difficulty is also great because the entire electrode sheet’s height and density must be highly consistent.
There is also a difficulty in this process. During the rolling process, the aluminum foil in the material area and the aluminum foil in the non-material area have different stresses and are prone to breakage.
This requires good ductility of aluminum foil. Aluminum foil has better ductility when heated. The industry’s general solution is to use a hot rolling machine, which is heated. The special feature of the honeycomb rolling process is that the aluminum foil is preheated by electromagnetic heating to increase its ductility, because heating during rolling has limited effect.
In the rolling process, the CPK of the “Short Knife” of Honeycomb Energy can achieve more than 1.33 (equivalent to a theoretical pass rate of the product segment of 99.993%).
In the die-cutting process, unlike the first phase of Honeycomb Energy, the second phase uses laser cutting. Laser cutting has higher precision, produces less burrs, does not require molds, and is faster. Compared with the first phase, the cutting speed has been increased from 30 meters per minute to 40-50 meters per minute.
After cutting, it is the most core and competitive stacking process of Honeycomb Energy. In China, companies that adopt the square aluminum shell technology route generally use winding process because of its speed and simpler equipment. The stacking process used to be used for soft pack batteries.
However, stacked batteries are safer and have higher energy density. Therefore, Honeycomb Energy has just appeared and has determined to take stacking as the technical route and become the leader of high-speed stacking process.
In phase one, Honeycomb Energy has achieved the industry’s fastest stacking speed of 0.6 seconds per sheet. In phase two, Honeycomb’s Z-shaped stacking machine has achieved 0.4 seconds per sheet. In addition, in a process that is surrounded by a fence on the second phase production line, Honeycomb has achieved a stacking speed of 0.125 seconds per sheet.
Liu Xiaoan said that a stacking speed of 0.125 seconds per sheet can already rival the winding process. The general winding speed is 0.2 seconds per sheet.
While stacking fast, it also needs to be stacked accurately. Liu Xiaoan introduced that the alignment accuracy of the “Short Knife” stacking process is ±0.3mm, which has reached the best level in the industry.
After the stacking process, the stacked polar groups need to be sent for assembly. In the logistics section that connects the two processes, Honeycomb Energy uses the industry’s first magnetic levitation logistics line. Compared with traditional belt logistics lines, the magnetic levitation logistics line has a faster speed of up to 3 meters per second, which is ten times of the industry standard of 0.3 meters per second, and the foreign object suppression rate has increased by 80%.
One advantage of the maglev logistics line is that it does not generate friction and thus will not cause dust pollution. On the other hand, the honeycomb also uses AI technology to set the acceleration and deceleration of the maglev tray to prevent collisions.
After the laminated pole piece is subjected to processes such as hot pressing, assembly, injection, activation, aging, and testing, the “short knife” is completed.
Thus, the “Short Knife” was born.
Currently, making square batteries larger has become a trend because it can improve energy density and can be combined with the chassis, partially used as a structural component. Many companies also use long and thin-shaped battery cells, but they either cannot make them that long or the product yield is not high enough.
The “Short Knife” production line at the FENIXO Changzhou Plant, not only can produce “Short Knives” that are as long as 600mm but also has a good yield rate.
Yang Hongxin introduced that the “Short Knife” production line is still in the ramp-up stage, but the yield rate has already reached 85-90%. “Our goal is to achieve the same level as traditional products–more than 95%.”
Hard technology achieves intelligent manufacturing
The “Short Knife” production line of FENIXO Energy is not only the most advanced battery production line in the world, it is also a model of intelligent manufacturing.
Firstly, this production line uses a lot of high-end equipment required for battery production.
The most typical is the ultra-high-speed lamination machine. When FENIXO Energy first launched its “Lamination Era” slogan, it looked for advanced lamination technology and equipment from South Korea. However, the ultra-high-speed blade-type battery cell laminating machine that will be put into use in the second phase is developed and designed by FENIXO Energy itself and commissioned by the equipment factory for processing.
As mentioned earlier, the laminating efficiency of this machine can reach 0.125s/piece, surpassing the efficiency of ordinary winding processes, leading the progress of global laminating processes.
In addition, in the slurry mixing process, FENIXO uses a 2300L large-capacity double-row planetary mixing device. Liu Xiaoan introduced that the single capacity of this device is the largest in the industry, and each slurry can produce about 10 pure electric vehicles.
Secondly, this production line extensively uses machine vision to help achieve industrial automation and intelligence.
The “Short Knife” production line mainly uses three types of machine vision devices: beta ray detection system, laser detection, and CCD (image) detection.
Beta ray detection and laser detection emit beta rays or lasers on the detection object and analyze and measure the thickness, size, position, and other data of the detection object by detecting the attenuation of beta rays or the reflection data of lasers.
Using CCD detection is like taking a picture of the object being inspected, then converting the image signal into a digital signal, and determining the characteristics of the object being inspected by conducting calculations through the system.
Honeycomb Energy uses these devices extensively to monitor the quality of cell production.
For example, in the coating process, Honeycomb uses three sets of β-ray online surface density detection systems and two real-time CCD coating width detection systems to ensure consistent surface density and accurate coating position.
In the rolling process, Honeycomb uses real-time online laser thickness measurement technology to help control the thickness to within ±3 microns.
In the stamping process, Honeycomb uses two sets of CCD detection equipment to detect white spots, black spots, scratches, and whether the size of the polarizer matches the requirements.
For problems that the human eye cannot detect, visual inspection by machines can reveal even the smallest details and help control product quality.
Thirdly, Honeycomb Energy’s “Short Knife” production line uses AI technology extensively.
When Honeycomb Energy began planning its factory construction, building power batteries to meet vehicle specifications was the norm, and to achieve vehicle specifications, a significant amount of AI technology was necessary.
For AI technology to work, it must have sensory abilities similar to those of humans to obtain information. Therefore, production lines must be digitized to a high degree to allow artificial intelligence to fully grasp production line information.
In this regard, Honeycomb Energy’s production process control is seven-dimensional, including people, machines, materials, methods, environment, testing, and time, monitoring over 2,500 process factors and being able to trace process data for each individual cell. With such data in hand, AI can get a complete overview of the production line.
The second step for AI to function is to learn. Through the analysis of big data, AI gradually establishes the parameters of 2,500 factors and their relationships with product quality and quantity. In this process, Honeycomb relies not on its supplier Siemens but on its own algorithm team to construct various models to train AI.
The third step for AI to function is intelligent feedback and continuous calibration. Once the relationship between each factor and the quality and quantity of the product to make a parameter combination that will improve quality or efficiency has been found, AI can adjust the production parameters in real-time to meet production requirements.
For example, in the coating process, β-ray detection systems and CCD coating width detection systems interact in real-time with the coating machine. When the detection equipment detects anomalies in surface density and position, it will automatically adjust the coating parameters, allowing the coating machine to execute the required production requirements.Currently, battery production has become a business that different companies and even countries are scrambling for. The advanced level of equipment and intelligent level are two major indicators for assessing battery factories. Currently, the “Short Sword” factory of Funeng has a leading intelligent manufacturing level.
Especially artificial intelligence. Advanced equipment can be purchased or imitated, but the layout and evolution of artificial intelligence require time and accumulation.
The “Short Sword” that Continuously Evolves
The current “Short Sword” production line of Funeng Energy produces lithium iron phosphate batteries, with an energy density of 175 Wh/kg. The second generation “Short Sword” can achieve an energy density of 190 Wh/kg.
Energy density competition is just one aspect of battery competition. Along with the demand from application scenarios such as electric vehicles, batteries also need to compete in many aspects such as fast charging rate, stable and economical material supply, and high safety.
How will the “Short Sword” of Funeng Energy respond?
Funeng Energy’s strategy is to continuously research and apply new material technologies to meet different needs while adhering to the “Short Sword” standard system.
In terms of energy density improvement, Funeng has both similar plans to its peers and its own persistent plans.
“Whether it’s mixing lithium iron phosphate with lithium manganese oxide, or mixing manganese iron phosphate with ternary, we are doing both,” said Yang Hongxin.
He introduced that, using similar technology, Funeng will launch the third generation “Short Sword” in 2023, and the energy density will be further increased.
Yang Hongxin introduced that the technology of lithium iron manganese phosphate has achieved a higher energy density, which has also challenged ternary batteries and cobalt-free batteries.
Funeng’s response plan is to still adhere to the nickel route for ternary batteries, but to increase the specific capacity and voltage of nickel. “We will start mass production of 4.4V high-voltage nickel products in the first half of 2022. Cobalt-free 4.4V products will also be mass produced at the end of this year or the beginning of 2023,” he said.
By increasing the voltage and overall specific capacity of the material, the energy density of the ternary “Short Sword” is expected to reach 250 Wh/kg, which can create a certain gap between iron manganese phosphate and iron phosphate, Yang Hongxin said.
In terms of fast charging performance, Funeng Energy’s improvement roadmap is: “1.6C is standard configuration for all our ‘Short Swords’ next, we are developing iron phosphate 2C-2.2C, and we are also pre-researching the 4C of lithium iron phosphate.”
In addition, Yang Hongxin revealed that Funeng Energy is researching silicon anode, and is also developing solid-state battery technology, sodium ion battery positive and negative electrodes, electrolytes, and so on.
Regarding the innovation and evolution of battery materials, Yang Hongxin believes that “this is where the fun of making batteries lies, but small businesses cannot keep up because they need to develop fifth-generation, sixth-generation products, and more than a dozen systems need to be integrated together. The huge investment, resource requirements, and talent needs will only be effective in the next few years. Only companies that value research and development and have certain resources can persist, and many small businesses cannot fully blossom to do this.”
Indeed, the current battery industry is no longer a resource-intensive industry, but a technology-intensive industry. Both research and development and production require huge investment in research and development, production equipment, process innovation, and application investment. This makes the survival threshold of battery companies higher and higher.
In 2022, Honeycomb Energy’s “Short Sword” batteries are expected to exceed 2GWh in shipments, opening up the situation for its entire series of “Short Sword” products.
How long the “Short Sword” can be wielded depends on Honeycomb Energy’s ongoing research and development and production innovation.
In terms of research and development, Honeycomb Energy has already begun developing the second and third generations of “Short Sword” products. In terms of production, after the first “Short Sword” production line was built and put into operation, Honeycomb Energy has gained experience. The next “Short Sword” production line will have higher yields and efficiency.
This article is a translation by ChatGPT of a Chinese report from 42HOW. If you have any questions about it, please email bd@42how.com.