Cylinder, square, soft pack electric vehicle lithium battery which is better, buy skills

The core component of electric vehicle lithium battery is battery, lithium battery battery is divided into three categories, are: cylindrical, square, soft package.

In the current use of lithium battery process, cylinder, square, soft pack three batteries are equipped with models, and there is no absolute good or bad points, can only be said that each has its own advantages.

In terms of cell energy density, soft-pack cells are theoretically the highest, followed by square cells and the smallest by cylindrical cells.

Square cell

A typical square lithium-ion battery, the main components include positive electrode, negative electrode, positive electrode shell, insulation layer, sealing cover, upper cover, pressure relief valve, overcharging safety device, etc.

Square cells usually have two safety structures: acupuncture safety device and overcharge protection.

Advantages of square battery: high energy efficiency, low relative weight, high energy density, simple structure, convenient expansion is an important option to improve the energy density, the system is relatively simple to monitor one by one; another benefit of simple system is relatively good stability.

Disadvantages: because square lithium battery can be customized according to the product size of the production, so there are thousands of models on the market, and because there are too many models, it is difficult to unify the process; production automation level is not high, the monomer difference is large, in large-scale application, the system life is far lower than the single life.

Soft pack cell

Soft pack lithium battery is a polymer shell on the outside of liquid lithium ion battery.In the structure of aluminum-plastic film packaging, in the case of safety risks, the soft pack battery will only crack at most.

So-called soft pack cell, is relative to the cylinder and square the two hard shell battery, its internal composition: positive, negative, diaphragm, electrolyte, and square and cylindrical lithium battery difference, the biggest difference is that soft pack cell using aluminum plastic composite film as a shell, square and cylindrical battery using metal material as a shell.

The reason why the soft packaging cell is thermal packaging is that it uses aluminum plastic packaging film material, usually divided into three layers, outer resistance layer (generally outer protective layer composed of nylon BOPA or PET), resistance layer (middle layer aluminum foil) and inner layer (multi-functional high barrier layer).

Advantages of soft-pack cells:

1. Good security.

2. Higher specific energy.

3. Good cycle performance.

4. Small internal resistance.

5. Flexible design.

Disadvantages of soft-pack batteries:

1. Standardization and cost issues.Due to the many models of soft-pack batteries, the degree of automation in the middle and back segments is not as good as that in the cylindrical battery production line, which makes the mass production of soft-pack battery impossible.

2. Shell reinforcement is required.The soft-pack battery structure itself is not strong enough to lead to the need for additional shell in the formation process and increased cost.

The cylindrical cell is mainly composed of positive electrode, negative electrode, diaphragm, collector, safety valve, overcurrent protection device, insulation parts and shell.

Advantages of cylindrical cells:

1. Good monomer consistency.

2. Good mechanical properties of the monomer itself.

3. The technology is mature and low cost, and the space for cost optimization has been almost consumed.

4. The monomer energy is small, and the situation is easy to control when accidents occur.

Disadvantages of cylindrical cells:

1. There is little room for energy density.

2. Under the condition of uneven temperature environment, the probability of alienation of a large number of core characteristics increases.

3. The number of cylindrical cells in the battery system is very large, which increases the complexity of the battery system and leads to the high cost of the battery system.