Double heat treatment and rapid formation method for battery cell coated with artificial SEI film negative pole piece

Abstract

The invention relates to a double heat treatment and rapid formation method for a battery cell coated with an artificial SEI film negative pole piece. The method comprises the following steps: preparing a negative pole piece, carrying out hot-pressing treatment according to the technology disclosed by the invention after lamination, and then carrying out hot-pressing special treatment on a batterycell during battery cell formation, so as to make the battery cell with high efficiency and better performance. The method has the advantages that the cycling stability of the battery is improved, the voltage consistency of the battery cell is ensured, and an excellent formation result can be quickly and efficiently realized by regulating and controlling the specific voltage of the battery cell formation.

Description

technical field [0001] The present application relates to the field of lithium battery manufacturing, in particular, the present application relates to a double heat treatment and rapid formation method of a battery core coated with an artificial SEI (solid electrolyte interface, solid electrolyte interface) film negative pole piece. [0002] technical background [0003] In recent years, with the popularization of new energy vehicles, the market demand for power batteries is increasing. Among them, high-end electric vehicles also have relatively large requirements for battery capacity. Therefore, there is still a lot of room for further increasing the effective capacity of power batteries. [0004] In order to increase the effective capacity of the power battery, the current main ideas are to improve the first efficiency, reduce the ohmic internal resistance and the polarization internal resistance. Among them, in terms of improving the first effect, it can be achieved by us...

AI Technical Summary

Problems solved by technology

[0006] In terms of thermal composite treatment, CN 103959539 B forms two battery cells of type A and type C by stacking / folding pole pieces and diaphragms, but the technology is complex and the product cost is high; the heating effect of the battery cells is difficult to unify. It is easy to cause uneven heating on the surface of the separator, and the adhesive coated on the surface of the separator cannot form an affinity with the electrode sheet. The surface of the negative electrode sheet is easy to form an uneven and poor-quality SEI film, which is easy to form in the later period of battery use. Lithium precipitation or black spot phenomenon

[0007] Patent CN 107403945 A introduces a method of forming and rolling soft-packed lithium-ion batteries. The process of this invention is relatively complicated, and the temperature of the battery core after hot pressing is relatively high. Cooling and cold pressing are required, which prolongs the working hours and increases the production cost. ; After the cell is hot-pressed, part of the electrolyte will be vaporized, resulting in more air bubbles remaining on the surface of the pole piece and the gas volume inside the air bag will increase sharply

Even after the subsequent cold pressing, there will still be some gas remaining inside the core pack, and black spots will easily form on the surface of the negative pole piece after the cell cycle, resulting in capacity loss; this technology is prone to uneven distribution of temperature inside the cell, which is likely to cause diaphragm The surface is heated unevenly, the binder coated on the surface of the separator cannot form an affinity with the pole piece, and the electrolyte is easy to decompose at high temperature, which makes the surface of the negative pole piece easy to form an uneven and poor-quality SEI film. In the later stage of battery use, it is easy to form black spots or lithium precipitation, which brings capacity loss or safety risk;

[0008] Patent CN 106099202 A, according to 8% to 15% of reversible capacity as a method of regulating SEI, the consistency of the final cell capacity is low; this technology uses relatively high pressure in the formation and exhaust stage, and under high temperature and high pressure conditions Under high pressure, the air bag will bulge up quickly; under pressure, the diaphragm and the pole piece are in close contact, and the electrolyte in the core pack cannot be well adsorbed on the surface of the pole piece and the diaphragm, which will easily lead to low liquid retention. As a result, a harder battery is formed, which makes the cycle performance of the energy-type battery relatively poor in the later stage

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