Factors to Consider When Designing and Manufacturing 18650 Lithium Batteries

The choice of materials is the most important factor in the battery design process. Different materials have different performance characteristics, and the performance of the developed batteries is also different. The cycle performance of the positive and negative materials is good, and the cycle life of the battery will be long. In terms of ingredients, pay attention to the amount of positive and negative materials added. Generally speaking, in the design and assembly process, it is generally required that the capacity of the negative electrode is larger than that of the positive electrode. If it is not excessive, the negative electrode will precipitate lithium during the charging process, forming lithium dendrites, which will affect the safety. If the negative electrode is too much relative to the positive electrode, the positive electrode may be excessively delithiated, causing the structure to collapse.

The electrolyte is also a very important factor in the influence of the reversible capacity of the battery. The process of desorption and intercalation of lithium ions in electrode materials is always the process of interaction with the
electrolyte, and this interaction has an important influence on the changes of the interface state and internal structure of electrode materials. In the process of interacting with the positive and negative electrode materials, the electrolyte will be lost. In addition, when the battery is formed to form the SEI film and pre-charged, part of the electrolyte will also be consumed. Therefore, the type and injection volume of the electrolyte also affect the battery life.

The manufacturing process of lithium-ion batteries mainly includes: positive and negative electrode ingredients, coating, filming, winding, shelling, liquid injection, sealing, chemical formation, etc. In the battery production process, the process requirements for each step are very strict. Any process that is not well controlled may affect the battery cycle performance. During the batching process of positive and negative electrodes, attention should be paid to the amount of binder added, stirring speed, slurry concentration, temperature and humidity, and to ensure that the materials can be dispersed evenly.

In the coating process, under the premise of ensuring the high specific energy of the battery, the coating amount of the positive (negative) electrode should be reasonably controlled, and the thickness of the electrode should be appropriately reduced to reduce the decay rate of the battery. The coated pole piece should be further compacted with a roller press. Appropriate positive compaction density can increase the discharge capacity of the battery, reduce the internal resistance, reduce the polarization loss, and prolong the cycle life of the battery.

When winding, the rolled cells should be tight and not loose. The tighter the diaphragm and the positive and negative electrodes are rolled, the smaller the internal resistance. However, when the diaphragm is rolled too tightly, it will cause difficulty in wetting the pole piece and the diaphragm, resulting in a smaller discharge capacity; if the roll is too loose, the pole piece will be over- expanded during the charging and discharging process. , increasing the internal resistance, reducing the capacity and shortening the cycle life.

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