Analysis of technical characteristics of cylindrical, square and soft pack lithium-ion batteries



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Square lithium ion battery;

Square lithium-ion battery usually refers to aluminum shell or steel shell square battery. The popularity of square battery is very high in China. With the rise of automobile power lithium battery in recent years, the contradiction between automobile mileage and battery capacity has become increasingly prominent. Lithium battery manufacturers mostly use aluminum shell prismatic batteries with higher battery energy density. Because the structure of prismatic batteries is relatively simple, unlike cylindrical batteries, which use high-strength stainless steel as the shell and accessories with explosion-proof safety valves, the overall The attachment weight should be light and the relative energy density should be higher. Square batteries have two different processes: winding and lamination.

Soft pack lithium ion battery

The key materials used in the soft-pack lithium-ion battery cathode materials, anode materials and separators are not much different from traditional steel shell and aluminum shell lithium-ion batteries. The biggest difference lies in the soft packaging material (aluminum-plastic composite film). It is the most critical and technically difficult material in soft-packed lithium-ion batteries. Flexible packaging materials are usually divided into three layers, namely outer barrier layer (usually an outer protective layer composed of nylon BOPA or PET), barrier layer (middle layer aluminum foil) and inner layer (multifunctional high barrier layer). The packaging material and structure of the soft pack battery give it a series of advantages. It is light in weight. The weight of the soft pack battery is 40% lighter than the steel shell lithium ion battery of the same capacity, and 20% lighter than the aluminum shell lithium ion battery; the internal resistance is small and soft The internal resistance of the pack battery is smaller than that of the lithium ion battery, which can greatly reduce the self-consumption of the battery; the design is flexible, the shape can be changed to any shape, and it can be thinner. It can be customized according to customer needs and develop new battery cell models. The disadvantages of soft pack batteries are poor consistency, high cost, and easy leakage.

Comparative analysis of technical characteristics

1. Battery shape: The square lithium ion battery can be of any size, and the cylindrical battery is immobilized.

2. Rate characteristics: the process limitation of cylindrical lithium ion battery welding multi-electrode, so the rate characteristics are slightly worse than the square multi-electrode method

3. Discharge platform: The same positive electrode material, negative electrode material, and electrolyte are used, so theoretically the discharge platform is the same, but the internal resistance of the square battery is slightly superior, so the discharge platform is slightly higher.

4. Product quality: Cylindrical lithium-ion battery technology is very mature, the probability of common secondary slitting defects of the pole piece is low, and the winding process is more mature and automated than the lamination process. The lamination process is still using semi-manual methods. , So there is an adverse effect on the quality of the battery.

5. Tab welding: The tabs of cylindrical lithium-ion batteries are easier to be welded than square lithium-ion batteries, and square batteries are prone to false welding that affects battery quality.

6. PACK into groups: round batteries are relatively easier to use, so the PACK method is simple and the heat dissipation effect is good. The heat dissipation problem should be solved when the square batteries are PACK.

7. Structural features: The chemical activity at the corners of the square battery is poor, and the performance of the battery is significantly reduced after long-term use.


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