A kind of silicon carbon negative pole piece and its preparation method and lithium ion battery

Abstract

The present invention is applicable to the technical field of lithium-ion batteries, and provides a silicon-carbon negative pole piece and a preparation method thereof and a lithium-ion battery. The silicon-carbon negative pole piece comprises: a current collector; a first carbon negative electrode layer arranged on the collector On the fluid; the main material layer is arranged on the current collector; the main material layer includes a silicon carbon negative electrode region with a pit structure and a carbon negative electrode region filled in the pit structure; and a second carbon negative electrode layer , set on the main material layer. In the present invention, the elastic conductive agent is uniformly dispersed and wrapped on the surface of silicon-carbon material particles, so as to play a buffering role when the silicon-carbon material expands. In addition, the present invention adopts the gravure printing coating technology, and the silicon-carbon material and the carbon material containing lithium salt are distributed in the gap. The lithium salt can supplement lithium for the silicon-carbon material and form an SEI film, and the carbon material provides a volume expansion buffer for the silicon-carbon material, which can At the same time, it solves the problems of low first effect and expansion and cracking of silicon carbon materials.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a silicon-carbon negative pole piece, a preparation method thereof, and a lithium-ion battery. Background technique [0002] At present, in the field of secondary batteries, lithium-ion batteries are widely used in new energy vehicles, energy storage systems, consumer electronics and other fields due to their excellent characteristics such as environmental protection, high energy power density, and high operating voltage. As one of the four major components of lithium-ion batteries, the negative electrode has been dominated by graphite-like carbon materials for many years. However, its theoretical gram capacity of 372mAh / g can no longer meet the demand for high energy density, so new high specific capacity materials have been extensively studied. The theoretical specific capacity of the silicon negative electrode is as high as 4200mAh / g, the lithium int...

AI Technical Summary

Problems solved by technology

[0004] And existing technical scheme, all there is certain drawback

For example, encapsulation, doping and encapsulation are common methods used to improve material properties. To enclose a protective layer of carbon material on the surface of silicon materials, it is necessary to first make silicon materials into nanometer scale and then encapsulate them. Technology The difficulty is high and the process is complicated. Although the volume expansion of silicon is suppressed to a certain extent, the problem of silicon fragmentation after long-term cycling still exists.

The pole piece buffer layer method, coating a layer of graphite buffer layer on the surface of the silicon carbon negative electrode, only weakens the expansion of the pole piece level, but the expansion of the silicon material level still exists, and the improvement is very limited, such as pulverization, SEI cracking and other problems still exists

The pre-lithiation method, whether it is adding lithium foil to the silicon carbon negative electrode, or adding lithium powder or other lithium supplements to the silicon carbon slurry, greatly increases the difficulty and cost of the manufacturing process, and cannot solve the problem of silicon material expansion

Images