Material selection is a key factor affecting the performance of lithium-ion batteries. If you choose a poor cycling performance of the material, even if the process is more reasonable, made more perfect, the cycle performance of the battery cell is bound to be unable to guarantee;Battery recycling and if you choose a better material, even if the follow-up made a slight problem, the cycle performance may not be too bad too far (for example, a lithium cobalt acid grams play only 135.5mAh / g or so and lithium precipitation of the battery cell, 1C, although more than a hundred times diving but 0.5C , 500 times more than 90%; another time the core is disassembled after the negative pole has black graphite particles of the core, cycle performance is normal). From the material point of view, the cycle performance of a full battery is determined by the cycling performance of the positive electrode after matching with the electrolyte, the negative electrode after matching with the electrolyte cycle performance of the worse of the two. The poor cycling performance of the material, on the one hand, may be in the cycling process of the crystal structure changes too quickly and thus can not continue to complete the embedded lithium delithiation, on the other hand, may be due to the active material and the corresponding electrolyte can not generate dense and uniform SEI film caused by the active material and the electrolyte premature side reaction and the electrolyte is consumed too quickly and thus affect the cycle. In the design of the battery cell, if one pole is confirmed to choose a material with poor cycling performance, then the other pole does not need to choose a material with good cycling performance, which is wasteful.

Too high compaction of positive and negative poles, although it can improve the energy density of the core,cylindrical cell assembly machine but it will also reduce the cycling performance of the material to a certain extent. From the theoretical analysis, the greater the compaction, the greater the damage to the structure of the material, and the structure of the material is to ensure that the lithium-ion battery can be the basis of recycling; in addition, the positive and negative electrode compaction is higher than the core is difficult to ensure a high amount of liquid retention, which is the basis for the completion of the normal cycle of the core or more cycles.

Excessive water will have side reactions with the positive and negative active substances, destroying their structure and thus affecting the cycle, and at the same time, too much water is not favorable to the formation of SEI film.battery making machine However, while trace water is difficult to remove, trace water can also ensure the performance of the cell to a certain extent. Unfortunately Wenwu has almost zero personal experience in this area and can't say much about it. If you are interested, you can search the forum for information on this topic, there is still a lot of it.

The effect of coating film density on cycling is an almost impossible task. Inconsistencies in film density will either result in differences in capacity, or differences in the number of layers in the winding or stacking of the cell. For the same type of cell, same capacity, same material, a lower film density equates to one or more additional winding or stacking layers, which corresponds to more diaphragm that can absorb more electrolyte to ensure cycling. Considering that thinner film density can increase the multiplication performance of the cell, and the baking and de-watering of the pole piece and the bare cell will be easier, of course, the error in coating may be more difficult to control when the film density is too thin, and the large particles in the active substance may also have a negative impact on coating and rolling, more layers means more foils and diaphragms, which in turn means a higher cost and lower energy density. Therefore, a balanced consideration is also needed when evaluating.

In addition to the impact of the first irreversible capacity and coated film density deviation, the impact on cycling performance is also a consideration for anode excess. For lithium cobaltate plus graphite system, it is more common for the anode graphite to be the "short board" in the cycling process. If the negative electrode excess is not sufficient, the core may not precipitate lithium before cycling, but after several hundred cycles, the positive electrode structure changes very little, but the negative electrode structure is seriously damaged, and cannot fully receive the lithium ions provided by the positive electrode, thus precipitating lithium, resulting in a premature decline in capacity.

Insufficient electrolyte has an impact on the cycle mainly due to three reasons, one is insufficient liquid injection, the second is insufficient aging time or insufficient immersion of the positive and negative electrodes due to too much compaction and so on although the liquid injection is sufficient, and the third is that the electrolyte inside the core is consumed as the cycle is completed. Insufficient liquid injection and insufficient liquid retention. For the third point, the microscopic manifestation of the match between positive and negative electrodes, especially the negative electrode and electrolyte, is the formation of dense and stable SEI, while the visible manifestation to the right eye is both the rate of electrolyte consumption during the cycling process. Incomplete SEI film on the one hand can not effectively prevent the negative electrode and electrolyte side reaction and thus consume electrolyte, on the one hand, in the SEI film defective parts will be with the cycle to regenerate SEI film and thus consume reversible lithium source and electrolyte. Whether it is for a cell that has been cycled hundreds or even thousands of times or for a cell that has dived dozens of times, if the electrolyte is sufficient before cycling and has been consumed after cycling, increasing the amount of electrolyte retained is likely to improve its cycling performance to a certain extent.

External factors such as charging/discharging multiplier, cut-off voltage, charging cut-off current, over-charging and over-discharging during testing, temperature of the testing room, sudden interruption of the testing process, and internal resistance of the contact between the testing point and the battery cell during the testing process will all affect the results of the cycling performance test to a greater or lesser extent. In addition, different materials have different sensitivities to the above objective factors, so standardizing the test criteria and understanding the common and important material characteristics should be sufficient for daily work.

Like the barrel principle, among the many factors affecting the cycling performance of a battery cell, the final determining factor is the shortest of the many factors. At the same time, all of these factors interact with each other. With the same materials and manufacturing capabilities, higher cycling tends to mean lower energy density.