The different packaging forms of the battery are designed to serve the needs of the user. In the field of consumer electronics, pouch cell is commonly used in mobile phones, notebooks and other products.
In the car field, prismatic battery is currently widely accepted, and pouch cell is not popular in China due to immature supply chain, technical difficulty, low group efficiency, and few battery factories involved. But at present, pouch cell technology has been very mature, how to play to its own advantages in the future. Today's article focuses on this.
1. The background of the battery development
In recent years, technological breakthroughs have been made in the field of lithium batteries. In addition to improvements to chemical systems, many technological advances are structural innovations.
Blade batteries, Tesla 4680 battery vs CATL CTP battery, and Kirin battery CTP3.0 technology paired with prismatic batteries. In contrast, how is the pouch cell developing. Historically, pouch cells have also gone through non-standard large sizes and so on.
The previous design was more from the perspective of the battery itself, and as the pouch cell is also combined with the car for structural design, what is the new design idea of the pouch cell?
2. Features of the pouch cell
① Advantages of the pouch cell
- The size is flexible, and the production line can be adjusted according to the needs of automotive customers.
- The aluminum plastic film of the pouch cell has a large deformation space, and the cell level is easier to relieve pressure when thermal runaway.
- Aluminum plastic film, light weight, small proportion of inactive parts, pouch cell energy density.
- The mechanical stress on the internal structure during cycling is small.
- The tab position is abundant, and the heat distribution is uniform during the loading and unloading process.
In the actual manufacturing process, pouch cell uses the lamination process, which has the following advantages over prismatic using the winding process:
● Higher energy density
The winding process inside the battery cell has a curve at the corner of the winding, and the space utilization is lower. This is because the lamination process makes the most of the battery space. With the same volume of cell design, there come the battery high energy density.
● Stable structure
Although the lamination process also expands during the periodic use of the battery, in general, the expansion force of each layer is similar, so the interface can be kept flat.
● More security
Security is also brought about by the advantages of the structure itself. Expansion and contraction of the electrode sheet, stretching of the diaphragm, etc. will cause deformation of the cell.
Therefore, ensuring that the deformation of the battery cell is minimized is also a guarantee of battery safety. Laminated batteries have higher safety cells due to uniform force and small deformation.
● Longer cycle life
Laminated cells have a large number of tabs. The shorter the electron transmission distance, the smaller the resistance, so the internal resistance of the laminated battery can be reduced. And the heat production of the battery is small. The winding is prone to deformation, expansion and other problems, which affect the battery attenuation performance.
② Disadvantages of pouch cell
The housing strength is low, there are many additional materials in the group technology, and the CTP design was not used before. The capacity is not large, and the aluminum plastic film limits the thickness of the battery and limits the capacity.
Lamination productivity is relatively low. In other words, from the point of view of product features, the difficulties that pouch cell needs to face directly are:
- The breakthrough in technical difficulty is designed in combination with the development of automobiles.
- Solve the problem of low group rate and make the battery capacity larger.
- Improve the maturity of the industrial chain and increase production capacity.
- Effective cost design.
Of course, the most important thing is the improvement of the manufacturing end, and with the improvement of the efficiency of the lamination process, it has also driven the pouch cell to expand its advantages.
3. The market pattern of pouch cell
The market landscape for pouch cell has changed. The battery market pattern is in the years 2018 to 2021, which is conducive to the development of pouch cell. The market share of cylindrical batteries is shrinking.
Tesla has always been the largest user of cylinders, and after starting to choose prismatic batteries, the impact of cylinders on the overall market has become smaller.
- Pouch cell: since the market share continues to increase, the shares in the first half of this year fell slightly, at about 25%.
- Prismatic battery: it has always occupied 50% of the market share, and its proportion has increased in the past two years.
From the perspective of the automotive market of product terminals, the proportion of battery products is limited by the sales volume of finished vehicles. Therefore, the higher share of prismatic batteries is closely related to the automotive end market, while crowding out the share of other products.
4. Market reason analysis of pouch cell
The application side of vehicle companies is changing, and from the perspective of automobile companies, there is indeed a game with battery companies. Another reason that is easy to overlook is also related to the speed of capacity expansion of CATL and BYD, the main companies of prismatic – the rapid expansion of production capacity, which objectively increases market share.
There are some bottlenecks in the development of pouch cells. The main reasons are:
On the one hand, there is the problem of material supply, including materials such as aluminum plastic film. At a time when the market is demanding large-scale supplies, for the 10 lithium battery companies in the world, pouch cell needs to overcome technical problems.
In terms of technology, due to the main characteristics of pouch cells, the advantages around energy density are not outstanding (high cells, large pack discount rate). When you compete, you lose some money in terms of cost and productivity. This is also a problem that pouch cell needs to address urgently.
5. The development of pouch cell
The future of pouch cell in the current pouch cell design, the SPS (Super Pouch Solution) released by Farasis is very characteristic, which can be said to explore a correct direction for the revival of pouch cells. A closer study shows that SPS is mainly made around large pouch cells, large pouch cell systems, and large pouch cells. Material costs are reduced and volume utilization is improved.
● Resolve thermal runaway
Whether pouch cells can do CTP design is a big challenge. The SPS is designed to stack pouch cells on top of each other and integrate directly into the PACK or even the car chassis. The composite use of high-efficiency liquid cold plate and thermal conductive sheet improves the heat dissipation efficiency of the battery system.
● Fast charging speed
Fast battery charging is the next hot spot for battery characteristics improvement. The improved heat dissipation efficiency of the battery system, coupled with precise temperature control, also increases the battery cycle life.
6. ConclusionIn general, the three technical paths of power batteries, cylindrical, prismatic and pouch cell, are all developed separately. Pouch cell technical path has always been flexible. If you want to gain more share in the ongoing competition, you must make the capacity larger and the structure simpler. In this direction, there are constantly companies in the innovation of cell level and grouping, which has a great impact on the entire industry.