Negative pole piece and lithium ion battery containing same

Abstract

The invention provides a negative pole piece and a lithium ion battery containing the same. A negative electrode active material of the negative pole piece uses a mixed material of a magnesium-silicon-oxygen composite oxide and graphite, wherein the magnesium-silicon-oxygen composite oxide material has the advantages of higher initial charging efficiency, higher compaction density (up to 1.8 g / cm<3>) and smaller expansion cycle and the like than a SiOy material (y is a number between 0.8 and 1.2), so that volume change in the lithium intercalation process of the negative electrode can be reduced to a certain extent, particle integrity and integrity of the pole piece are ensured, cycle performance of the negative pole piece is improved, and the problems of low first charging efficiency, fast cycle attenuation, large cycle expansion and the like of the SiOy material high-proportion doped negative electrode can be effectively solved; and therefore, the energy density and the cycle life ofthe battery are remarkably improved, and the negative pole piece is suitable for large-scale commercial production. The energy density of the lithium ion battery recorded by the invention is obviously improved, the problem of rapid attenuation at the initial stage of circulation is effectively improved, and the service life is longer.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a negative pole piece and a lithium ion battery containing the pole piece. Background technique [0002] Traditional lithium cobalt oxide (LCO), nickel-cobalt-manganese (NCM), nickel-cobalt-aluminum (NCA), lithium iron phosphate (LFP) cathode materials combined with graphite anode materials are far from meeting the growing demand for energy density, so the new The development of high energy density positive and negative electrode systems is very necessary. [0003] Si-based anode materials have excellent properties such as high specific capacity, low cost, and easy processing; Si composite materials mixed with graphite anodes have been widely used in the fields of high-energy-density cylinders and steel shell power batteries, but due to the large volume expansion during the Si cycle , which limits its application in high-proportion blending and pouch ba...

AI Technical Summary

Problems solved by technology

In contrast, silicon oxide (SiO y , y is between 0.8-1.2), although the specific capacity is low (~1800mAh / g), but due to the advantages of longer cycle life and small volume expansion of the material, it is more in line with the requirements of the negative electrode material of the pouch battery. It is more and more favored by pouch battery manufacturers, but SiO y There are still some problems in the large-scale commercial application of materials: for example: SiO y The material consumes a large amount of active Li during the first charge and discharge process, resulting in high irreversible capacity, resulting in low first-cycle Coulombic efficiency (y Modification (carbon coating, adjustment of Si:O ratio, etc.) can improve the first Coulombic efficiency to a certain extent, but it still cannot reach the level of graphite negative electrode (y Material application, a major obstacle in the process of increasing energy density in the lithium battery industry