Effect of Coating on the Performance of Lithium Batteries
Electrode coating generally refers to a process in which a uniformly stirred slurry is uniformly coated on a current collector by film drying coating machine, and the organic solvent in the slurry is dried. The effect of coating has an important impact on battery capacity, internal resistance, cycle life and safety, ensuring uniform coating of pole pieces. The choiceof coating method and control parameters have an important impact on the performance of lithium-ion batteries, mainly in:
1.Coating and drying temperature control: If the drying temperature is too low during coating, the complete drying of the pole piece cannot be guaranteed. If the temperature is too high, the coating on the surface of the pole piece may fall off because the organic solvent inside the pole piece evaporates too quickly and other phenomena;
2.Coating surface density: If the coating surface density is too small, the battery capacity may not reach the nominal capacity. If the coating surface density is too high, it is easy to cause waste of ingredients. The precipitation of lithium dendrites pierces the battery separator and causes a short circuit, causing safety hazards;
3.Coating size: If the coating size is too small or too large, the positive electrode inside the battery may not be completely covered by the negative electrode. During the charging process, lithium ions are intercalated from the positive electrode and move to the electrolyte that is not completely covered by the negative electrode. Among them, the actual capacity of the positive electrode cannot be used efficiently. In severe cases, lithium dendrites will be formed inside the battery, which can easily pierce the separator and cause the internal circuit of the battery;
4.Coating thickness: If the coating thickness is too thin or too thick, it will affect the subsequent pole piece rolling process, and the performance consistency of the battery pole piece cannot be guaranteed.
In addition, electrode coating is of great significance to the safety of batteries. Do a good job of 5S work before coating to ensure that no particles, sundries, dust, etc. are mixed into the pole piece during the coating process. If sundries are mixed in, it will cause a micro-short circuit inside the battery, and in severe cases, the battery will catch fire and explode.
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