Comparison of advantages and disadvantages of lithium soft pack battery

Lithium soft pack battery packaging often includes cylindrical winding, square winding, and square stacking.

1. Cylindrical winding

That is a cylindrical battery, which is a classical soft pack battery configuration. The monomer comprises positive and negative electrodes, separators, positive and negative electrode collectors, safety valves, overcurrent protection devices, insulators, and shells. There were many steel shells in the early days, and now there are many aluminum shells as raw materials.

According to the size, there are mainly 18650, 14650, 21700, and other models of this kind of battery. Among them, 18650 is the most common and the most mature technology.

Advantages: Cylindrical batteries have the best development history, a high degree of standardization, and it is easy to achieve unified standards in the industry. The automation level of cylindrical battery production is higher than that of other batteries, which ensures the high efficiency of cylindrical battery production. Body consistency, on the other hand, also reduces production costs. In addition, the mechanical properties of the cylindrical battery cell itself are better. It can show the highest bending strength under similar dimensions compared to the other two batteries.

Disadvantages: As a battery for solar street lights, it is not a single battery. It often needs to form a battery pack to work. The cylindrical shape has a low space utilization rate, and poor radial thermal conductivity will cause temperature distribution problems. The probability of dissimilating many cell characteristics in such an environment will increase. In addition, many cylindrical batteries of steel shells make. The weight will be heavier when forming a battery pack, and there is little room for energy density to increase.

2. Square winding

This kind of battery cell composes mainly of a top cover, a shell, a lamination or winding composed of a positive plate, a negative plate, a diaphragm, an insulating member, a safety component, etc. Steel shells generally dominated the shell in the early days by using a needle-punched safety design device (NSD) and an Overcharge safety protection device (OSD). Now aluminum shells have become the mainstream.

This kind of battery cell is mainly composed of a top cover, a shell, a lamination or winding composed of a positive plate, a negative plate, a diaphragm, an insulating member, a safety component, etc., and is designed with a needle-punched safety device (NSD) and Overcharge safety protection device (OSD), the shell was generally dominated by steel shells in the early days, and now aluminum shells have become the mainstream.

Square winding soft pack battery

Advantages: The square battery has high packaging reliability and higher utilization of space; the system has high energy efficiency, the weight is also higher than that of the cylindrical battery of the same size, and the energy density is higher; the structure is relatively simple, and the capacity expansion is relatively easy. It is more convenient. If you want to increase the energy density by increasing the single capacity, this kind of battery is more suitable. The capacity of the single unit is large, and the system structure is relatively simple, which makes it possible to monitor the units one by one. The design of NSD and OSD, it is safer and more reliable to use. In addition, the relatively simple system structure makes it stable. Sexual performance is also better.

Disadvantages: This kind of battery can be customized according to specific needs (mainly in terms of size), so the models of square batteries in the market are not uniform, and this non-uniformity also makes it difficult to unify the process. The quality of the batteries that come out varies. The level of production automation is not high, and the individual cells are quite different. The use of battery packs may lead to the problem that the life of the battery pack is much lower than that of the single cells.

3. Square stacked

That is to say, the soft pack battery we often talk about. The basic structure of this battery is similar to the above two kinds of batteries. It consists of positive and negative electrodes, separators, insulating materials, positive and negative electrodes, and shells. A single sheet’s positive and negative electrode sheets are wounded differently and form a battery by stacking multiple layers of electrode sheets.

Among them, the shell is mainly aluminum plastic film. The outermost layer of this material structure is a nylon layer, the middle is an aluminum foil, and the inner layer is a heat-sealing layer. Each layer bonds with an adhesive. This material has good ductility, flexibility, and mechanical strength. It also has an excellent performance in heat sealing performance and is also very resistant to electrolyte and strong acid corrosion.

 Square Soft pack battery

Advantages: The soft pack battery adopts a superimposed manufacturing method, so the volume is thinner, the energy density is the highest, and the thickness is relatively thin, generally not exceeding 1cm, and it is better than the other two in terms of heat dissipation performance, and the same capacity. , The soft pack battery is about 40% lighter than the steel shell lithium battery and 20% lighter than the aluminum shell battery, and there are many pole pieces. Each pole piece has flanges and tabs welded together.

Good distribution uniformity and uniform heat distribution during the charging and discharging process. It is a thin sheet design, it is easy to form modules and battery packs.
The utilization rate of space is also very high, it is also flexible in size changes, and the shape is not only Limited to a square shape, but it can also adapt to different spaces.

Disadvantages: The shell strength of the soft pack battery is not as strong as that of the other two batteries with an aluminum shell or steel shell as a shell. It is difficult to guarantee stability, the battery body is relatively soft, and the contact resistance solved between the pole pieces may be large at the module level or the battery pack level, which increases the technical difficulty. Like the square battery, although it is more flexible in size and can adapt to different spaces, it is difficult to unify the standardization of the process, so the quality of the battery is also uneven.

The consistency of the battery is also poor. If the battery operates in an internal environment with insufficient heat transfer, such as adiabatic or high temperature, the battery’s temperature will rise significantly, resulting in the formation of “hot spots” inside the battery pack, posing a safety hazard.

Analyzed Conclusion

1. Cylindrical batteries (cylindrical winding type) generally use steel shells, but also aluminum shells. The technology is relatively mature, small in size, flexible in groups, low cost, mature in technology, and good in consistency; after grouping,

Gupta said, “Although nickel-cobalt-manganese ternary lithium-ion batteries (NMC) are in short supply in the energy storage market,
Lithium iron phosphate (LFP) batteries are in sufficient supply.
Extend delivery time and prices have remained the same, lithium iron phosphate (LFP) battery suppliers have begun to enter the market with limited nickel-cobalt-manganese ternary lithium-ion battery (NMC) applications at competitive prices, making lithium iron phosphate Batteries (LFPs) becomes an attractive option for power and energy applications.”

the heat dissipation, the weight is heavy, and the specific energy is low.

2. Square batteries (square wound type), mostly steel shells in the early days, and most aluminum shells now. Good heat dissipation, easy to design in groups, good reliability, high safety, including explosion-proof valve, high hardness; high cost, many models, difficult to unify the process level, is one of the mainstream technical routes.

3. Soft pack battery (square laminated type), aluminum-plastic film as the outer packaging, flexible size change, high specific energy, lightweight, relatively small internal resistance; poor mechanical strength, difficult sealing process, complex group structure, heat dissipation Bad design, no explosion-proof device, easy to leak, poor consistency and high cost.