Formation method for improving K value of soft-package battery cell

Abstract

The invention discloses a formation method for improving the K value of a soft-package battery cell, which solves the problems of poor film formation of an SEI film formed by normal pressure formationof the soft-package battery cell, deformation and insufficient hardness of a battery cell main body, black spots on an interface, lithium precipitation and the like, and also solves the problem of high K value reject ratio caused by the formation of a high-temperature and high-pressure clamp of the soft-package battery cell. According to the invention, in the formation step operation process, theinterlayer spacing between the positive electrode and the diaphragm and the interlayer spacing between the negative electrode and the diaphragm can be reduced by applying a small surface pressure tothe surface of the battery cell, and the migration path of lithium ions in the formation process is further reduced, so that the film forming quality is improved, the internal activity of the batterycell can be improved by controlling the temperature of a clamping plate, and the migration difficulty of the lithium ions is reduced. The method has the advantages that the SEI film forming quality ishigh, the main body of the battery cell is not easy to deform, and the K value of the battery cell is stable.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a formation method for improving the K value of soft-pack batteries. Background technique [0002] With the increasing demand for high energy density in the market, the thickness of the diaphragm of lithium-ion batteries is also required to be thinner and thinner, but the thin diaphragm has the following problems: On the one hand, due to the elastic deformation of the thinner diaphragm when it is subjected to mechanical stress The larger the value is, the greater the internal stress generated by the diaphragm during the winding process of the cell. During the formation process, due to the expansion of the pole piece itself, the internal stress of the cell is further increased, and the stress cannot be released, which leads to the failure of the cell. Deformation increases the layer spacing between the positive and negative electrodes of the cell and the ...

AI Technical Summary

Problems solved by technology

[0002] With the increasing demand for high energy density in the market, the thickness of the diaphragm of lithium-ion batteries is also required to be thinner and thinner, but the thin diaphragm has the following problems: On the one hand, due to the elastic deformation of the thinner diaphragm when it is subjected to mechanical stress The larger the value is, the greater the internal stress generated by the diaphragm during the winding process of the cell. During the formation process, due to the expansion of the pole piece itself, the internal stress of the cell is further increased, and the stress cannot be released, which leads to the failure of the cell. Deformation increases the layer spacing between the positive and negative electrodes of the cell and the diaphragm, which leads to problems such as black spots on the interface, lithium precipitation, and deformation of the cell body; on the other hand, the thin diaphragm is easy to be pierced by burrs and dust due to its poor mechanical strength , leading to poor K values

[0003] At present, there are two main formation methods for lithium-ion soft-packed batteries: common formation under normal temperature and pressure and high-temperature and high-pressure fixture formation; ordinary formation under normal temperature and pressure is prone to poor SEI film formation, deformation of the main body of the battery cell, and insufficient hardness of the main body of the battery cell. , black spots on the interface, lithium analysis and other problems; and the formation of high-temperature and high-pressure fixtures can easily cause the problem of poor K value of the battery cell

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