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Cylinder cell, prismatic cell, and pouch cell: which is better for the solar energy storage batteries?

cylindrical cells and pouch cells and prismatic cells

The solar energy storage batteries are now the main light source of home battery backup. It is simple to install and does not require a lot of wiring. Converting solar energy into electricity, and electricity into home energy brings power for home applications. SmartPropel rechargeable solar batteries play a key role in this process. Compared with lead-acid batteries or gel batteries in the past, the lithium batteries commonly used today are better in terms of energy, power, etc. They are also easier to achieve rapid charging and deep discharge and have a longer life, so it also gives us a better light experience.

However, there is also a difference between good and bad lithium batteries. Today, we will start with their packaging form to see what features these lithium batteries actually have, and which one is better, there are three types of packaging: cylindrical winding, prismatic welding type, and pouch winding type.

1. Cylindrical Welding Type

cells


This is a cylindrical battery, which is a classical battery configuration, the monomer is mainly composed of positive and negative electrodes, a diaphragm, positive and negative collector, safety valve, over-current protection device, insulation, and shell, the early shells are more steel, now there are many to aluminum shells as raw materials.
According to size, there are now 18650,14650,26650,21700 and other models, in which 18650 is the most common, but also the most mature technology.

Advantages:
Cylindrical batteries have the best history of development, have a high degree of standardization, and are easy to achieve uniform standards in the industry. The level of automation in the production of cylindrical cells is higher than that of other batteries, this ensures the high efficiency of cylindrical battery production, monomer consistency, on the other hand, also reduces production costs.
In addition, the cylinder battery has good mechanical properties, and it can show the highest bending strength under similar size compared to the other two batteries.

Disadvantages:
solar battery, is not a single battery, often need to be composed of batteries to work, cylindrical shape space utilization rate is low, the radial thermal conductivity difference will cause the temperature distribution problem, in such an environment, a large number of cell characteristics will increase the probability of alienation.
In addition, many cylindrical batteries now have a steel shell as the shell, when composed of the battery pack, the weight will be heavier, and the energy density of the room is very small.

2. Prismatic Welding Type

prismatic

The prismatic cell is mainly composed of a top cover, shell, positive plate, negative plate, diaphragm, insulator, a safety assembly, etc. internal design has a needle safety protection device (NSD) and over-charge safety protection device (OSD), Shell early is generally steel-based, now aluminum has become the mainstream.

Advantages:

Prismatic cells are more reliable in packaging and more efficient in space utilization; the system is energy-efficient, has a similar size, weighs less than cylindrical cells and has a higher energy density; and has a simpler structure, capacity expansion is also relatively easy if you want to increase the energy density by increasing the monomer capacity, this prismatic battery is more appropriate. It is good for lithium ion battery factory custom 12V LiFePO4 lithium battery and 48V LiFePO4 lithium battery for home power backup.

The single unit has a large capacity, and the system structure is relatively simple, making it possible to monitor the single unit one by one. Coupled with the design of NSD and OSD, it is safer and more secure to use. In addition, the system structure is relatively simple, making it more stable.

Disadvantages:

The battery can be customized according to specific needs (mainly in terms of size), so in the market square battery models are not uniform, which makes it difficult to unify the technology.

In the production automation level is not high, monomer differences are large, and the composition of the use of the battery, battery life may be far less than the single life of the problem. So the prismatic battery cells should sort before assembling energy storage solar batteries to ensure consistency and cycle life.

3. Pouch Welding Type

pouch cell

The basic structure of this kind of battery is similar to the above two kinds of batteries. It consists of positive and negative electrodes, membranes, insulating materials, positive and negative electrode ears, and shells, however, unlike the winding type, which is formed by winding a single positive and negative plate, the stack type battery is formed by stacking the multi-layer plates.
Among them, the shell is mainly aluminum-plastic film. The material structure of the outermost layer is nylon, the middle is aluminum foil, the inner layer is a heat-sealed layer, each layer is bonded with a binder, this material has good ductility, flexibility, and mechanical strength, in the barrier, heat sealing performance is also very excellent, but also very resistant to electrolyte and strong acid corrosion.

Advantage:

The pouch cells are made by stacking, so they are thinner, have the highest energy density, is thinner, are less than 1 cm thick, and have better heat dissipation performance than the other two models, for the same capacity, the pouch battery is about 40% lighter than cylindrical lithium battery, 20% lighter than the prismatic battery, and there are a lot of electrodes, each of which has a flange welded to the electrode ear, the current density on the plate is well-distributed, the heat is evenly distributed during charging and discharging, and it is designed as a sheet, which is easy to form modules and batteries, and has a high utilization rate of space, also flexible in terms of size, the shape is not limited to the square, can be well adapted to different spaces.

Disadvantage:

The strength of the pouch battery case is not as strong as that of the other two types of batteries with aluminum or steel shells. The reliance on group technology is strong, and the reliability of the aluminum-plastic film package is difficult to guarantee if the battery is used for a long time, the battery body is relatively soft, the contact impedance between the electrodes may be large, need to be solved at the module level or the battery pack level, which adds technical difficulties.
Like prismatic cells, they are flexible in size and fit in different spaces, but they are also difficult to standardize, so the quality is uneven.
Battery consistency is also poor. If the battery is operating in an internal environment where heat is not transferred sufficiently, such as insulation or high temperature, the temperature of the battery will rise significantly, resulting in a “hot spot” inside the battery pack, it’s a security risk.

To put it simply,

  1. Cylindrical battery ( cylindrical winding), usually in steel or aluminum case. Mature process, small size, group flexibility, low cost, mature process, good consistency; group heat is not good design, high weight, and low energy density.
  2. Prismatic battery (prismatic winding type), mostly steel shell in the early days, now mostly aluminum shell. Good heat dissipation, easy design in groups, good reliability, high safety, containing explosion-proof valve, high hardness; high cost, many models, difficult to unify the technology level, is one of the mainstream technical routes.
  3. Pouch battery (Pouch welding type), aluminum-plastic film as outer packaging, flexible size change, high specific energy, lightweight, small internal resistance; poor mechanical strength, complex group structure, bad heat dissipation design, no explosion-proof device, easy leakage, poor consistency, high cost, etc.