During the production process of batteries, there may be fine dust particles and impurities in the air, as well as dust and burrs on the positive and negative electrodes. These factors can easily cause physical contact inside the battery and induce short circuits, greatly affecting its performance. In severe cases, it may even cause the battery cell to fail to charge, resulting in a "dead" battery cell.

Reasons for high short-circuit rate in the lamination process;

1) Dust

Removing the lithium battery with a slight short circuit can reveal black spots on the battery separator. If the black spot is located near the center of the diaphragm, it is highly likely caused by dust breakdown. During the production and manufacturing process of lithium batteries, dust in the air or metal powder on the electrode and diaphragm during production can cause micro short circuits inside the battery cell. The irreversible reaction caused by micro short circuits caused by impurities is the main reason for the excessive self discharge of individual lithium batteries.

2) Burr

Before use, the electrode sheet should be cut into specified sizes using a specific template. During the cutting process, it is inevitable to have chips or burrs on the electrode plates. These foreign objects will be partially entangled in the cell during lamination, mixed between the positive and negative electrodes and the diaphragm, posing a risk of internal micro short circuits. When the lithium battery with a micro short circuit is disassembled, it is found that the black spots appearing on the separator of the lithium battery are mostly at the edge position, which is caused by burrs generated during the electrode slicing process.

3) Direct contact between positive and negative electrode plates

During the lamination process, the diaphragm should completely wrap around the positive and negative electrode plates, and the size of the negative electrode plate is slightly larger than the positive electrode plate. In some cases, there may be problems with the correction process of the diaphragm, causing it to not completely wrap around the positive and negative electrode plates, causing the diaphragm to shift towards one end and causing direct contact between the positive and negative electrode plates, resulting in a short circuit.