As one of the most promising lithium battery packaging methods, soft-pack packaging has both obvious advantages and disadvantages.
In terms of advantages, the first is the high energy density. According to data, the average cell energy density of mass-produced ternary soft-pack power batteries in the current power battery industry has reached 240-250Wh/kg, while the energy density of ternary square power batteries with the same material system is 210-230Wh/kg. The energy density of a single ternary soft-pack power battery cell is on average 10%-15% higher than that of a ternary square power battery.
Secondly, it has good safety performance. In recent years, the occurrence of spontaneous combustion accidents in new energy vehicles has made governments and consumers pay more and more attention to the safety of new energy vehicles. Under the same material system, ternary soft-pack power batteries, which are encapsulated in aluminum-plastic film soft packs, generally release heat by expanding gas if thermal runaway occurs; while square and cylindrical batteries, due to their hard-shell packaging, cannot release heat, resulting in greater internal pressure and potentially causing an explosion.
In addition, square and cylindrical batteries produced using a winding process are more prone to uneven internal temperatures and stress distribution as the battery is used over time, especially at the winding and bending points, which can lead to safety hazards.
Thirdly, it has excellent electrochemical performance. Ternary soft-pack power batteries have the advantages of large capacity and low internal resistance. Due to the use of aluminum-plastic film packaging, the capacity is 50% higher than that of steel-cased batteries of the same size and material system, and 20-30% higher than that of aluminum-cased batteries. Because of its low internal resistance, ternary soft-pack power batteries can greatly reduce the battery's self-discharge, improve the battery's rate performance and cycle life, and generate less heat.
Fourthly, it offers flexible design. At the cell level, the size and shape of ternary soft-pack power battery cells are flexible, allowing companies to customize them based on their own product designs and customer needs. At the module and battery pack level, the spatial layout of ternary soft-pack power batteries is more flexible, allowing for rectangular or T-shaped layouts to meet the space requirements of more vehicle models.
However, compared to prismatic batteries, pouch batteries are currently less commonly used in the market. This is because their disadvantages are equally obvious.
First, pouch batteries have higher requirements for product consistency. Ternary pouch power batteries are more complex in their manufacturing process. For example, the packaging process is more difficult to control and is prone to problems such as bulging, resulting in poor product consistency. This places higher demands on the technical level and manufacturing processes of enterprises.
Second, the packing efficiency is relatively low. Compared to prismatic and cylindrical power batteries with the same material system, ternary soft-pack power batteries have a relatively low packing efficiency, which means that the energy density of ternary soft-pack power battery systems is currently not much different from that of prismatic and cylindrical power battery systems.
Third, the cost is relatively high. Due to the use of thinner and softer aluminum-plastic film packaging, the self-protection of ternary soft-pack power battery cells is poor, and they are easily punctured in extreme situations. Therefore, metal protective layers need to be added to the battery pack to provide more protection, which will increase costs and place higher demands on the product design of enterprises.
