Comparison of Cylindrical Lithium Batteries and Soft Pack Lithium Batteries

Comparison of Cylindrical Lithium Batteries and Soft Pack Lithium Batteries

At present, lithium-ion batteries mainly include square lithium batteries, cylindrical lithium batteries, and soft-pack lithium batteries. Among them, the square and cylindrical shells are mainly made of aluminum alloy, stainless steel and other hard shells, while the soft-pack shells are made of aluminum-plastic film. Manufacturing, which is their essential difference, the important advantages of soft-pack lithium-ion batteries in terms of performance include:

1.Good safety performance: The soft-pack battery has less electrolyte leakage, and in the event of a safety hazard, the soft-pack battery will swell and crack, instead of exploding when the internal pressure is too high like a hard-shell battery;

2. Light weight: The weight of the soft pack battery is 40% lighter than that of the steel shell square battery of the same capacity, and 20% lighter than the aluminum shell square battery;

3. Large battery capacity: the soft pack saves 20% of the volume, which is 50% higher than that of the steel shell battery of the same size and 20-30% higher than that of the aluminum shell battery;

4. Good cycle performance: the cycle life of the soft pack battery is longer, and the attenuation of 100 cycles is 4% to 7% less than that of the aluminum case;

5. Small internal resistance: The internal resistance of the soft pack battery is smaller than that of the lithium-ion battery, and the minimum domestic resistance can be less than 35m, which greatly reduces the self-consumption of the battery;

6. Flexible design: the shape can be customized according to customer needs, and it can be made thinner. The ordinary aluminum shell can only be 4mm, and the soft bag can be 0.5mm.

In terms of performance, soft pack batteries have more comprehensive advantages, and have broad application prospects in the future:

1. Soft pack batteries are more suitable for portable applications that require high space or thickness, such as 3C consumer electronics;

2. Although the single-cell capacity of the square battery is high, it is heavy and large, while the soft-pack battery has obvious advantages in terms of energy density, and the current single-cell battery is also developing in the direction of large capacity and high rate, which will be more in line with new energy. Requirements for mobile power sources in automobiles and other fields;

3. Although the production process of cylindrical batteries is mature and the energy density advantage is obvious, due to the small capacity of the single cell, the battery pack of the same capacity requires more cells. For example, the battery pack capacity of the Tesla Model S is 85kWh, there are about more than 7000 18650 type cylindrical batteries, which has very high requirements for the BMS of the battery management system, and the single capacity of the soft pack battery can reach more than 10 18650 type cylindrical batteries, the requirements for BMS are low, between Most BMSs in China and even in the world have limited supporting capabilities. Large-capacity battery packs do not use too many cylindrical batteries. In addition, cylindrical batteries have poor safety due to too high energy density, and hard shells lead to high internal pressure, so explosions often occur. , while the soft pack battery has obvious advantages.

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