Negative electrode piece and lithium-ion battery containing the same

Abstract

The invention provides a negative electrode piece which comprises a negative electrode current collector and a negative electrode slurry applied on the negative electrode current collector. The negative electrode slurry includes a negative electrode active material, a negative electrode binder and a negative electrode conductive agent, the negative electrode active material is a mixture of Liy-SiOx and graphite, and the Li-SiOx accounts for 1% to 55% of the negative electrode active material. The invention belongs to the technical field of lithium-ion batteries, the negative electrode active material is a mixed material of Liy-SiOx and graphite, the problems of low first effect, fast cycle decay and large cycle expansion of a high-proportion mixed negative electrode can be effectively solved, therefore, the energy density and cycle life of the battery are significantly improved, and the negative electrode piece is suitable for large-scale commercial production.

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 being able to meet this 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-ratio mixed and pouc...

AI Technical Summary

Problems solved by technology

[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 being able to meet this 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-ratio mixed and pouch batteries, more and more manufacturers shift their research focus to Si-based negative electrode materials

[0004] Si and Si-C have the advantages of high specific capacity (~3400mAh / g), long cycle life, and high initial Coulombic efficiency. However, due to the large volume expansion during the cycle, the particles are easy to fall off, resulting in the effective active material detached from the conductive network, and the particles Fragmentation leads to repeated generation and destruction of the SEI film, accelerated electrolyte consumption, and increased internal resistance, making it difficult for Si and Si-C anode materials to be used in the practical application of pouch batteries.

In contrast, silicon oxide (SiO x ) Although the gram capacity is low (~1800mAh / g), due to the advantages of longer material cycle life and small volume expansion, it is more in line with the requirements of soft pack batteries for negative electrode materials and is more and more favored by soft pack battery manufacturers. However, SiO x There are still some problems in the large-scale commercial application of materials: SiO x 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 (x Modification (carbon coating, adjustment of Si:O ratio) can improve the first coulombic efficiency to a certain extent, but it still cannot reach the graphite negative electrode level (x Application, a major obstacle to the process of increasing energy density in the lithium battery industry

[0006] At the same time, due to SiO x During the lithium intercalation process of the negative electrode material, the volume changes greatly, the thickness of the electrode sheet changes greatly during the first charge and discharge process, and the conductive network and bonding strength of the negative electrode active material are significantly reduced.