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Which is better, wound lithium battery or laminated lithium battery?

Because of the different processing methods, lithium ion batteries are divided into wound lithium ion batteries and laminated lithium ion batteries. They have different principles and have the same performance. Then what is the difference between the lithium ion batteries produced by these two methods? Which is better?

wound lithium battery Vs laminated lithium battery

A) Detailed explanation of the two produce processes

Wound lithium battery

A battery composed of cells formed by a combination of winding methods is called a wound battery. Wound batteries are also called cells, and those in the battery industry are called winding cell.

Laminated lithium battery

Power batteries are generally divided into three forms: square shell, soft pack, and cylindrical. They mostly adopt two processes of winding and lamination, which have their own advantages and disadvantages. Lamination batteries are lithium batteries for vehicles that use lamination technology.

The working principle of the laminated battery is the same as that of the lithium ion battery used in traditional electric vehicles. The interior is composed of a positive electrode, a negative electrode, a diaphragm, and an electrolyte. The movement of lithium ions is used to generate electricity.

B) Which is better, wound lithium battery or laminated lithium battery?

1. Comparison of battery discharge platforms

The discharge platform of the winding lithium battery is slightly lower. Due to the high polarization of the internal resistance, part of the voltage is consumed in the internal polarization of the battery, so the discharge platform is slightly lower.

The discharge platform of the laminated lithium battery is high. The internal resistance is lower and the polarization is smaller, so the discharge platform will be higher than the winding battery and closer to the self-discharge platform of the material.

For many electrical equipment with a higher discharge cut-off voltage, a laminated battery with a higher discharge platform is undoubtedly the preferred choice.

2. Comparison of battery capacity density

The capacity density of the wound lithium battery is slightly lower. Due to the thickness of the lugs, the rounded sides of the battery, and the two-layer diaphragm at the end occupying the thickness in vain, the internal space is not fully utilized, and the volumetric specific capacity is slightly lower.

The laminated lithium battery has a higher capacity density. The internal space of the battery is fully utilized, so compared with the winding process, the volume specific capacity is higher.

The difference in battery capacity is reflected in these two types of batteries, which are thicker (insufficient utilization of the winding side space will be enlarged) and thinner (the thickness of the winding tabs occupying the thickness space in vain will be enlarged). Generally speaking, there are differences in batteries of conventional sizes, but they are not particularly obvious.

3. Comparison of battery energy density

The energy density of the wound lithium battery is slightly lower. Due to the lower volumetric capacity and lower discharge platform, the energy density is not as good as that of the laminated technology battery.

The laminated lithium battery has high energy density. Both the discharge platform and the volume specific capacity are higher than the winding process battery, so the energy density is correspondingly higher.

For details, please refer to the two points of amplification platform and capacity density. In general, lamination is dominant.

4. Comparison of applicable thickness of batteries

The scope of application of wound lithium batteries is narrow. For ultra-thin batteries, the thickness of the tabs occupies a large proportion of the space and affects the battery capacity. For ultra-thick batteries, not only is the wound pole piece too long and difficult to control, and the space on both sides of the battery cannot be fully utilized, it will also reduce the battery capacity.

The laminated lithium battery has a wide application range. Whether it is made into an ultra-thin battery or an ultra-thick battery, the lamination process can be competent.

The wound battery has no advantage in ultra-thin and ultra-thick batteries, but at the same time, it should be noted that there are not many applications for ultra-thin batteries for the time being. Ultra-thick batteries can be realized by stacking two thinner batteries in parallel. Capacity at the expense).

5. Comparison of battery thickness control

The thickness of the wound lithium battery is difficult to control. Due to the uneven internal structure of the cell, the tabs, the end of the diaphragm, and the two sides of the cell are all locations where it is easy to be over-thick.

The thickness of the laminated lithium battery is easy to control. The internal structure of the battery is the same, and the thickness of each part of the battery is correspondingly consistent, so it is easy to control its thickness.

Because the thickness of the wound lithium battery is difficult to control, it is necessary to leave some margin in the thickness when designing, thereby reducing the design capacity of the battery.

6. Comparison of battery thickness deformation

Wound lithium batteries are easily deformed. Due to the uneven internal structure, the internal reaction degree and rate of the cell during charging and discharging are uneven. Therefore, for thicker wound batteries, there is a possibility of deformation after high-rate charging and discharging or after multiple cycles.

The laminated lithium battery is not easily deformed. The internal structure is uniform and the reaction rate is the same. To be consistent, even thick batteries are not easy to deform.

This is also one of the reasons why the wound battery is not suitable to achieve a large thickness.

7. Comparison of battery shape

The winding lithium battery has a single shape; it can only be used as a rectangular parallelepiped battery. The size of the laminated lithium battery is flexible. The size of each pole piece can be designed according to the size of the battery, so that the battery can be made into any shape.

Flexible size is an obvious advantage of the lamination process, but as far as the current market is concerned, it seems that the demand for special-shaped batteries is not very large.

8. Comparison of battery suitable fields

The wound lithium battery is only a conventional battery. Laminated lithium batteries are used as high-rate batteries, special-shaped batteries, and power batteries.

Since the lamination process has better rate performance and more diverse choices of appearance and shape, the scope of application is also wider than that of wound batteries.

9. Comparison of battery coating

Coating requirements for wound lithium batteries are high. For each pole piece, the coating film density of each part cannot be significantly different, and the film density must be strictly controlled.

Laminated lithium battery coating requirements are low. Since the positive and negative electrodes are divided into many small pieces, the influence of poor coating film density can be eliminated by dividing the small pieces before lamination.

Due to the improvement of the current process, it is not difficult to control the density of the very long pole piece film of the wound battery within a range with little error, and it is very cumbersome to weigh and classify each small piece of the laminated battery, so the The impact of the point on the two is actually not great.

10. Slitting

The winding lithium battery is convenient to slit and the qualified rate is high. Each cell only needs to cut the positive and negative poles once, which is less difficult and has a low probability of producing defective products.

The splitting of laminated lithium batteries is cumbersome and the qualification rate is low. Each battery has dozens of small pieces, and each small piece has four sections. The slicing process is easy to produce bad punching. Therefore, for a single battery, the probability of generating pole sections and burrs is greatly increased.

Although the small pole pieces of the laminated battery can be strictly checked through the screening after slitting, who has the time to inspect each of the hundreds of thousands of small pole pieces?

11. Elasticity of battery pole piece

A certain degree of flexibility is required for winding lithium battery pole pieces. To prevent breakage and material loss at the bend. |The pole piece of the laminated lithium battery can have no elasticity.

As long as there is no obvious problem with the coating of pole piece ingredients, generally pole pieces can be purchased under this condition.

12. Battery spot welding

Easy spot welding of winding lithium battery. Each battery only needs two spot welding, which is easy to control.

Laminated lithium batteries are easy to solder. All pole pieces must be spot welded to a solder joint, which is difficult to operate and easy to solder.

It is not difficult to control the virtual welding in small batch production, but it is difficult to monitor and effectively solve the virtual welding in mass production.

13. Battery production control

The production control of wound lithium batteries is relatively simple. One battery has two pole pieces for easy control. The production control of laminated lithium batteries is cumbersome. Each battery has dozens of pole pieces, which are difficult to detect, transport, and count.

For a slightly larger factory, a daily output of tens of thousands means millions of laminated pole pieces per day! If the output is hundreds of thousands, it may even be close to 10 million small pole pieces! The difficulty of turnover and monitoring in the production process can be imagined.

14. Operator requirements

Winding lithium battery requires low operator requirements. It is difficult to complete the winding proficiently, but it is not difficult to complete the winding qualified. You can get started after knowing the process and controlling the alignment of the pole piece.

Laminated lithium batteries have high requirements for operators. The stacking operation is difficult, and the over-length and over-wide design of the negative electrode sheet to the positive electrode sheet is generally not too large, so the operator needs to have a certain operating basis.

15. Battery entry threshold

The entry barrier for winding lithium batteries is low. Manual winding is easy to operate, and manual operation can be considered when funds are insufficient, which saves funds for purchasing large-scale automatic equipment and lowers the entry barrier.

The barriers to entry for laminated lithium batteries are high. The automation equipment is not yet mature, and the cumbersome manual operation of the lamination process has caused labor costs to rise, thus raising the barriers to entry for the lamination process battery.

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