Carbon-containing material and lithium secondary cell containg the same material

Abstract

The invention discloses a carbon-containing material, comprising: graphite particles, which have a 002 plane interval d002 of less than 0.337 nm measured by X-ray wide-angle diffraction method; composite particles, which are arranged and distributed near the surface of the graphite particles, and the composite particles contain Si and C, the particle size of which is smaller than the particle size of graphite; and an amorphous carbon layer, whose in-plane spacing d002 is greater than 0.37 nm, the amorphous carbon layer is a polymer layer and is coated on the graphite particles and composite particles, wherein the said The composite particles include: Si particles, conductive carbon materials arranged and distributed near the surface of the Si particles, and a hard carbon material layer coated on the Si particles and the conductive carbon materials, and the Si particles are composed of crystalline Si phases. Carbonaceous materials have high charge-discharge capacity and improved cycle life characteristics.

Description

[0001] Cross-Referenced Related Patent Applications [0002] This application is based on Japanese Patent Applications 2001-058397, 2001-058398, and 2001-058399 filed with the Japan Patent Office on March 2, 2001, and Korean Patent Application 2001- 068302, the disclosures of which are incorporated herein by reference. technical field [0003] The present invention relates to a carbonaceous material and a lithium secondary battery comprising the same, and more particularly to a carbonaceous material having high charge-discharge capacity and improved cycle life characteristics and a lithium secondary battery comprising the same. Background technique [0004] As electronic products become smaller in size, lighter in weight, and higher in quality and performance, the demand for developing lithium secondary batteries with higher capacity is growing rapidly. [0005] Although graphite has a theoretical capacity of 372 mAh / g as a ma...

AI Technical Summary

Problems solved by technology

[0008] However, in the aforementioned simple mixed material (1), since the silicon compound is not firmly adhered to the graphite, there is concern that the silicon compound will be separated from the graphite due to the expansion and contraction of the graphite during the charge-discharge cycle.

In addition, due to the low electrical conductivity of silicon compounds, which weaken the cycle characteristics of lithium secondary batteries, it is not suitable for negative electrode active materials.

[0009] Moreover, in the graphite material (2) with silicon compound particles fixed, although the adhesion of the silicon compound on the graphite can be maintained in the early charge-discharge cycle, allowing silicon to play the role of the negative electrode active material, when repeated During the charge-discharge cycle, the silicon compound expands due to alloying with lithium, causing the bond to break and the silicon compound to separate from the graphite

In addition, silicon compounds are not good enough negative electrode active materials because they impair the cycle characteristics of lithium secondary batteries.

Moreover, unless the silane coupling agent is uniformly processed in the preparation of the negative electrode material, it cannot be made into a negative electrode material of consistent quality.

[0010] Finally, material (3) coated or bonded with amorphous carbon material on graphite-based carbon material and metal material such as Si suffers from the same disadvantages as material (2)

That is, when the charge-discharge cycle is repeated, the bonding strength between the silicon compound and the amorphous carbon material becomes weak, causing the metallic material to detach from the graphite-based carbon material.

Therefore, this metal material is not suitable as an anode active material due to impairing the cycle life characteristics of lithium secondary batteries.

[0011] Japanese Unexamined Patent Application Publication P5-74463 discloses a single crystal silicon used as an anode active material, but silicon has low capacity at low temperature

Moreover, its charge-discharge efficiency per cycle is low, and when using such as LiBF 4 In the case of Lewis (Lewis) acid-base electrolyte, the cycle characteristics deteriorate

Images