Soft pack lithium-ion batteries VS large format ones

Soft pack lithium-ion batteries and large format lithium-ion batteries:

Soft pack lithium-ion batteries are not widely used in China, but they have a 70% market share internationally. Here are the advantages and disadvantages of soft pack lithium-ion batteries:

Advantages:

1. Safety: Soft pack lithium-ion batteries use an aluminum-plastic film for packaging. In case of a safety hazard, the battery will generally bulge or crack open at the seal, releasing energy without the risk of explosion that hard pack lithium-ion batteries pose.

2. Lightweight: Soft pack batteries are 40% lighter than steel-cased batteries of the same capacity and 20% lighter than aluminum-cased batteries.

3. Low internal resistance: Domestic soft pack batteries can achieve a minimum internal resistance of less than 35mΩ, significantly reducing self-consumption.

4. Flexible design: Soft pack batteries can be designed to fit specific size and shape requirements, unlike hard pack batteries that only come in circular and square shapes.

Disadvantages:

1. Incomplete supply chain: Some of the raw materials and production equipment for soft pack lithium-ion batteries have a single source of procurement. Any issues with suppliers can impact battery production and supply stability for vehicle manufacturers.

2. High cost: The high-end aluminum-plastic film used in domestic soft pack lithium-ion batteries is still dependent on imports, making them very expensive.

3. Limited models: The number of available soft pack lithium-ion battery models is limited, and the cost of developing new models is too high. At present, soft pack lithium-ion batteries can only meet a small part of the market demand.

As for the safety concern of whether soft pack lithium-ion batteries will explode, they will not. In extreme cases, the battery will crack open at the seal to release energy without the risk of explosion that hard pack lithium-ion batteries pose. In overseas markets, many vehicle models are equipped with soft pack batteries, with over 30 models using them. Among the top 20 best-selling new energy passenger cars in Europe in 2020, 15 models were equipped with soft pack lithium-ion batteries.

Now let's discuss large format lithium-ion batteries and their advantages:

1. Low internal resistance and high safety: Large format lithium-ion batteries that replace many small capacity batteries with a single large capacity cell have excellent consistency. The data collected by the battery management system (BMS) is reliable. When a battery in a parallel system short circuits, it will quickly consume the energy in other batteries and cause a fire. Therefore, only large capacity single-cell batteries can avoid this problem.

   
   

   Also, since there is no self-reflow phenomenon within the parallel batteries, the larger the cell capacity, the lower the internal resistance, and the lower the operating temperature. This increases the load capacity and extends the life of the battery compared to parallel battery modules of the same capacity.

2. Fewer connection points, lower failure rate: The fewer the connection points in a high-capacity single-cell lithium-ion battery, the lower the probability of an accident.

   
   

3. For example, a 480V500Ah power module for a pure electric bus using 10Ah batteries in series and parallel would have as many as 7,500 batteries with up to 15,000 positive and negative connections. In contrast, a single 500Ah battery would require only 150 connections, significantly reducing the probability of accidents.

4. Large capacity single-cell lithium-ion batteries have a large capacitance, which can improve the performance of the power management system.

   
   

In conclusion, both soft pack lithium-ion batteries and large format lithium-ion batteries have unique advantages and disadvantages. Choosing the right type of battery depends on specific requirements and conditions.