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Influence of lithium battery design and manufacturing process
2021-07-22

In the process of battery design, the choice of materials is the most important factor. Different materials have different performance characteristics, and the developed batteries have different performance. The cycle life of the battery will be long if the positive and negative materials match well. In batching, we should pay attention to the addition of positive and negative materials. Generally speaking, in the design and assembly process, it is generally required that the capacity of the negative electrode should be excessive relative to that of the positive electrode. If it is not excessive, lithium will precipitate in the negative electrode during charging, forming lithium dendrites, which will affect the safety. The negative electrode is too much relative to the positive electrode, and the positive electrode may be delithiated excessively, resulting in structural collapse.
 
Electrolyte is also a very important factor in the reversible capacity of batteries. The process of lithium ion removal and intercalation of electrode materials is always the process of interaction with electrolyte, which has an important influence on the interface condition and internal structure of electrode materials. Electrolyte will be consumed in the process of interaction with positive and negative materials. In addition, part of electrolyte will be consumed when the battery is formed into SEI film and precharged. Therefore, the type of electrolyte and the amount of liquid injected also affect the battery life.
 
The manufacturing process of lithium ion battery mainly includes: anode and cathode batching, coating, tabletting, winding, casing, liquid injection, sealing, formation, etc. In the battery production process, every step of the process is very strict. If any process is not well controlled, it may affect the battery cycle performance.
 
In the process of batching positive and negative electrodes, attention should be paid to the amount of binder, stirring speed, slurry concentration, temperature and humidity, and ensure that the materials can be evenly dispersed.
 
In the coating process, on the premise of ensuring high specific energy of the battery, reasonable control of the coating amount of positive (negative) electrodes and appropriate reduction of electrode thickness are beneficial to reduce the decay rate of the battery. The coated pole piece should be further compacted by a roller press. Appropriate compaction density of positive electrode can increase the discharge capacity of the battery, reduce internal resistance, reduce 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 positive and negative electrodes are rolled, the smaller the internal resistance is, but when the diaphragm is rolled too tightly, it will make it difficult for the pole piece and diaphragm to wet, resulting in a smaller discharge capacity; Too loose winding will cause excessive expansion of the pole piece during charging and discharging, which will increase the internal resistance, reduce the capacity and shorten the cycle life.