1. Moisture

Excessive moisture can cause side reactions with positive and negative substances, damage their structure, and affect circulation. At the same time, excessive moisture is not conducive to the formation of SEI membranes. However, while trace amounts of moisture are difficult to remove, trace amounts of water can also maintain the performance of the cell.

2. Positive and negative compaction

Excessive positive and negative compaction can increase the energy density of the battery cell, but it also reduces the cycling performance of the material. From a theoretical analysis, the greater the compaction, the greater the structural damage to the material, which is the foundation for the recyclability of lithium-ion batteries; In addition, cells with higher compaction have a higher liquid retention capacity, which is the foundation for cells to complete normal or multiple cycles.

3. Objective conditions for testing

External factors such as charging and discharging rate, cut-off voltage, charging cut-off current, overcharging and discharging during the test, test room temperature, sudden interruption during the test, contact internal resistance between Test point and electric core, etc. will more or less affect the cycle performance test results. In addition, different materials have different sensitivity to the above objective factors, Unifying testing standards and understanding common and important material characteristics should be sufficient for daily work use.

4. Negative excess

The reason for negative excess not only needs to consider the influence of irreversible capacity and coating film density deviation, but also the impact on cycling performance. For the lithium cobalt oxide plus graphite system, negative graphite becomes a "short board" in the cycling process, which is common. If the negative excess is not sufficient, the battery cell may not precipitate lithium before cycling, However, after several hundred cycles, the positive structure changes very little, but the negative structure is severely damaged and cannot fully receive the lithium ions provided by the positive, resulting in the premature decrease of capacity.

5. Coating film density

It is an impossible task to consider the impact of membrane density on cycling in a single variable. Inconsistent membrane density can lead to differences in capacity, or differences in the number of cell winding or stacking layers. For cells of the same model, capacity, and material, reducing membrane density is equivalent to increasing one or more layers of winding or stacking layers. The corresponding increase in membrane density can absorb more electrolyte for cycling, Considering that thin film density can increase the rate performance of the cell, and the drying and water removal of the chip and bare cell will also be easier, of course, it may be difficult to control the error when coating too thin film density, and large particles in the material may also have a negative impact on coating and rolling. More layers mean more foil and membranes, which means high cost and low energy density. Therefore, balanced consideration is also needed during evaluation.