What should be paid attention to in the winding process of 18650 lithium battery
1. Humidity control <1%RH Purpose: to prevent water absorption during the winding process of positive and negative electrode sheets, resulting in zero voltage, self-discharge, and poor cycle performance;
Method: Calculate the dew point value and the temperature value to obtain the temperature and humidity value;
2. Dust control ≤100,000pc/ft3 (detection particle size is 0.5um)
Purpose: to prevent the dust from being involved in the pole group during winding, resulting in short circuit, overheating, fire, self-discharge and other defects of the cell;
Method: use a dust tester;（Lithium - Ion Battery Equipment）
3. Abnormal cutting burr
Process requirements: pole piece < 8um; pole ear burr < 12um; detection method: randomly select 1PCS battery cell for the first inspection of each shift, and test the front and rear ends of the positive and negative plates and the positive , Cut the burr on the negative terminal.
Adverse effects: The burr of the pole piece or the pole ear may cause the burr to pierce the diaphragm, short-circuit the positive and negative poles, overheat the cell, or explode in severe cases, posing a serious safety hazard.
4. Poor coverage of positive and negative electrodes
Process requirements: the alignment of positive and negative electrodes is 0.75?.55mm
The alignment of the negative electrode and the diaphragm is 1?.5mm
Detection method: Sampling inspection continues for 3PCS cells after the roll is changed, and the alignment is detected according to the "X-RAY Operation Instructions". Adverse effects: 1) The alignment of the positive and negative plates exceeds the process specifications, which may cause the negative plates to not cover the positive plates, and the battery cells During the charging process, the lithium ions released from the positive electrode cannot find the corresponding graphite intercalation, resulting in the accumulation of free lithium ions in the battery cell and dendrites on the negative electrode.
2) The alignment of the negative electrode sheet and the diaphragm exceeds the process standard, which may cause the negative electrode sheet to be squeezed and deformed, and the negative electrode material on the electrode sheet may fall off. During the charging process, the cell expands, and the powder material pierces the diaphragm, resulting in an internal short circuit of the positive and negative electrodes and safety. hidden danger;
5. Poor coverage of the pole piece in the winding direction (the length of the outer layer of negative electrode super-positive electrode material and the length of the inner layer of negative electrode and super-positive electrode material) Detection method: every 2H, each winding machine is randomly inspected for 3PCS cell dissection, and the eyepieces and ruler are used to measure the two cells respectively. Coverage difference size.
Adverse effects: It may cause that the negative electrode sheet does not cover the positive electrode sheet. During the charging process of the battery cell, the lithium ions released from the positive electrode cannot find the corresponding graphite embedding, resulting in the accumulation of free lithium ions in the battery cell and dendrites on the negative electrode. The dendrites pierce the separator and cause an internal short circuit, which is a safety hazard.
Method: Calculate the dew point value and the temperature value to obtain the temperature and humidity value;
2. Dust control ≤100,000pc/ft3 (detection particle size is 0.5um)
Purpose: to prevent the dust from being involved in the pole group during winding, resulting in short circuit, overheating, fire, self-discharge and other defects of the cell;
Method: use a dust tester;（Lithium - Ion Battery Equipment）
3. Abnormal cutting burr
Process requirements: pole piece < 8um; pole ear burr < 12um; detection method: randomly select 1PCS battery cell for the first inspection of each shift, and test the front and rear ends of the positive and negative plates and the positive , Cut the burr on the negative terminal.
Adverse effects: The burr of the pole piece or the pole ear may cause the burr to pierce the diaphragm, short-circuit the positive and negative poles, overheat the cell, or explode in severe cases, posing a serious safety hazard.
4. Poor coverage of positive and negative electrodes
Process requirements: the alignment of positive and negative electrodes is 0.75?.55mm
The alignment of the negative electrode and the diaphragm is 1?.5mm
Detection method: Sampling inspection continues for 3PCS cells after the roll is changed, and the alignment is detected according to the "X-RAY Operation Instructions". Adverse effects: 1) The alignment of the positive and negative plates exceeds the process specifications, which may cause the negative plates to not cover the positive plates, and the battery cells During the charging process, the lithium ions released from the positive electrode cannot find the corresponding graphite intercalation, resulting in the accumulation of free lithium ions in the battery cell and dendrites on the negative electrode.
2) The alignment of the negative electrode sheet and the diaphragm exceeds the process standard, which may cause the negative electrode sheet to be squeezed and deformed, and the negative electrode material on the electrode sheet may fall off. During the charging process, the cell expands, and the powder material pierces the diaphragm, resulting in an internal short circuit of the positive and negative electrodes and safety. hidden danger;
5. Poor coverage of the pole piece in the winding direction (the length of the outer layer of negative electrode super-positive electrode material and the length of the inner layer of negative electrode and super-positive electrode material) Detection method: every 2H, each winding machine is randomly inspected for 3PCS cell dissection, and the eyepieces and ruler are used to measure the two cells respectively. Coverage difference size.
Adverse effects: It may cause that the negative electrode sheet does not cover the positive electrode sheet. During the charging process of the battery cell, the lithium ions released from the positive electrode cannot find the corresponding graphite embedding, resulting in the accumulation of free lithium ions in the battery cell and dendrites on the negative electrode. The dendrites pierce the separator and cause an internal short circuit, which is a safety hazard.
