Composite negative pole piece, preparation method thereof and lithium ion battery

Abstract

The invention relates to a composite negative pole piece, a preparation method thereof and a lithium ion battery. The negative pole piece comprises a current collector metal-metal lithium composite substrate and a carbon fiber-lithium-containing metal composite structure arranged on the current collector metal-metal lithium composite substrate. The carbon fiber-lithium-containing metal composite structure comprises a three-dimensional skeleton and lithium-containing metal, wherein the mass ratio of the three-dimensional skeleton to the lithium-containing metal is (1-18): 6. Gaps of the skeleton are filled with the lithium-containing metal. The three-dimensional skeleton comprises carbon fiber, a polymer, a surfactant and a toughening agent in a mass ratio of (60-80): (10-30): (1-5): (0-5).According to the composite negative pole piece, a three-dimensional skeleton is filled with metal lithium, the composite negative pole piece with light weight and high strength is obtained, stable and uniform deposition of metal lithium is facilitated under high current density, the integrity and uniformity of an SEI film are improved, the conditions of pulverization and lithium death of a lithium piece are improved, the growth of lithium dendrites can be inhibited to a certain extent, and meanwhile, the composite negative pole piece has good interface performance with an electrolyte.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a composite negative pole piece, a preparation method thereof and a lithium ion battery. Background technique [0002] In recent years, with the rapid development of electric vehicles and high-end portable electronic devices, people's requirements for battery energy density continue to increase. At present, the industrialized lithium-ion batteries with graphite as the negative electrode have been difficult to meet the increasing demand for specific energy, so Lithium metal anodes with high specific capacity have entered the field of vision of researchers. Lithium metal has a specific capacity of 3860mAh / g and an electrochemical potential of -3.04V (vs the standard hydrogen electrode), making it an ideal anode material for lithium batteries. To use lithium metal as an anode material for lithium-ion batteries, we still need to overcome the following diffi...

AI Technical Summary

Problems solved by technology

First, during the cycle, due to the local polarization caused by the uneven deposition of lithium ions on the surface of lithium metal, lithium dendrites grow on the surface of lithium metal, and when the lithium dendrites grow to a certain extent, they may penetrate the separator. , leading to a short circuit in the battery, which raises safety concerns

Second, if lithium dendrites break, "dead lithium" will form, resulting in a loss of battery capacity

Third, on the road to industrial application, the mechanical properties of traditional lithium metal negative electrodes are poor, which is not conducive to the welding of tabs and the assembly of large batteries

However, the three-dimensional carrier materials in the prior art often have a large self-weight (such as porous copper foil, copper foam, nickel foam, etc.), which greatly increases the weight of the electrode, thus weakening the advantages of lithium metal as a high specific capacity electrode material.

Secondly, due to the active nature of lithium metal, it is very easy to have side reactions with the electrolyte, which leads to the deterioration of the integrity and compatibility of the system, thereby deteriorating the cycle of the full battery.

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