SILICON-SILICON OXIDE-LITHIUM COMPOSITE, MAKING METHOD, AND NON-AQUEOUS ELECTROLYTE SECONDARY CELL NEGATIVE ELECTRODE MATERIAL

Abstract

A silicon-silicon oxide-lithium composite comprises a silicon-silicon oxide composite having such a structure that silicon grains having a size of 0.5-50 nm are dispersed in silicon oxide, the silicon-silicon oxide composite being doped with lithium. Using the silicon-silicon oxide-lithium composite as a negative electrode material, a lithium ion secondary cell having a high initial efficiency and improved cycle performance can be constructed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a X-ray diffraction diagram of the low-temperature reaction product of silicon oxide and metallic lithium in Reference Example.

FIG. 2 is a X-ray diffraction diagram of the ignited state reaction product of silicon oxide and metallic lithium in Reference Example.

Claims

1. A silicon-silicon oxide-lithium composite in the form of a silicon-silicon oxide composite doped with lithium, having such a structure that silicon grains having a size of 0.5 to 50 nm in an atomic order and/or crystallite state are dispersed in silicon oxide.

2. The silicon-silicon oxide-lithium composite of claim 1, wherein the silicon grains have a size of 0.5 to 50 nm, and the silicon oxide is silicon dioxide which is doped with lithium.

3. The silicon-silicon oxide-lithium composite of claim 1, wherein the composite is in particle form, and surfaces of particles are coated with carbon in a coating weight of 5 to 50% by weight based on the weight of the surface-coated composite particles.

4. A method for preparing a silicon-silicon oxide-lithium composite, comprising doping silicon oxide with lithium at a temperature equal to or lower than 1,300° C., using metallic lithium and/or an organolithium compound as a lithiating agent.

5. A method for preparing a conductive silicon-silicon oxide-lithium composite, comprising providing a silicon-silicon oxide-lithium composite ground to a predetermined particle size, andperforming thermal CVD on the silicon-silicon oxide-lithium composite particles at 900° C. to 1,400° C. with an organic hydrocarbon gas and/or vapor, for coating the composite particles with carbon in a coating weight of 5 to 50% by weight based on the weight of the surface-coated composite particles.

6. A negative electrode material for use in a non-aqueous electrolyte secondary cell, comprising the silicon-silicon oxide-lithium composite of claim 1.

7. A negative electrode material for use in a non-aqueous electrolyte secondary cell, comprising a mixture of the silicon-silicon oxide-lithium composite of claim 1 and a conductive agent, the mixture containing 1 to 60% by weight of the conductive agent and having a total carbon content of 5 to 90% by weight.