The Factors of Lithium-ion Pouch Cell Gas Generation

Because the steel and aluminum case（cans）lithium ion battery in the explosion of great harm, at present, aluminum laminated film as the main packaging material gradually become the mainstream.

Due to the Aluminum laminated film pouch cell is prone to expansion, the expansion gas generation can be divided into normal gas generation and abnormal gas generation.

1. Normal gas generation

It refers to the formation of SEI film accompanied by gas generation in the battery formation process, which is often called formation gas generation. After analyzing the gas production and gas composition of the battery cathode and anode, it is concluded that the gas generation is mainly concentrated in the anode during the formation process.

Research shows:

(1) When it reaches about 1.5V, the anode electrode and electrolyte continue to have irreversible reaction, and the products cover the anode electrode surface;

(2) Below 2.5V, the gas is mainly H2 and CO2;

(3) Greater than 2.5V, a small amount of EC began to decompose, and the main product was C2H4.

(4) After 3V, DMC and EMC in the electrolyte begin to decompose, and the gas produced contains alkanes such as CH4 and C2H6 in addition to C2H4.

(5) When the voltage exceeds 3.8V, the product C2H4 decomposed by EC basically disappears.

The maximum gas generation occurs when the voltage ranges from 3.0 V to 3.5 V. This indicates that at 3.5V, is the main film-forming region of SEI film. Therefore, after 3.5V, due to the barrier effect of SEI film, gas production is basically completed and gas generation decreases rapidly.

2. Abnormal gas generation

(1) The film formation of the cell itself is unstable. In the subsequent cycle, the SEI film on the anode electrode surface may fall off or become loose, and the SEI film is reconstructed, accompanied by gas generation;

(2) It is caused by excessive water content in the battery cells;

(3) Abnormal gas production is caused by short circuit in the battery;

(4) high temperature stored process gas generation;

(5) It is over-charging and over-discharging lead to gas generation.

Generally speaking, excessive water levels and short circuits in batteries are common problems in the battery manufacturing process.

We provide aluminum laminated film materials and formed pouch cell case for lithium ion pouch cell. We provide custom service according to your requirements to design the new pouch die, but you should pay for the die sinking cost.（There is no minimum order quantity limit for custom service.）