Li-containing silicon oxide powder

Abstract

The present invention relates to a Li-containing SiOx powder (0.5 < x < 1.5) used in a negative electrode of a lithium secondary battery. On a powder particle cross section in a visual field of 1 [mu]m in four directions containing a particle surface and having a definition of 50 pixels * 50 pixels or greater, EELS measurements are performed, and in so doing, the spectral intensities in the Li-K edge domain and the Si-L edge domain are determined. Among the integrated intensities over one row of a particle outermost surface in the visual field, the integrated intensity for the Li-K edge domainis ILi(s), the integrated intensity for the Si-L edge domain is ISi(s), and ILi(s)/(ILi(s) + ISi(s)) is the outermost surface Li intensity ratio R(s). Among the integrated intensities over one row ofa near-surface 500 nm away inward from the particle outermost surface in the visual field, the integrated intensity for the Li-K edge domain is ILi(i), the integrated intensity for the Si-L edge domain is ISi(i), and ILi(i)/(ILi(i) + ISi(i)) is the near-surface Li intensity ratio R(i). Then, the Li-containing silicon oxide powder satisfies R(s)/R(i) < 1.

Description

technical field [0001] The present invention relates to a silicon oxide-based negative electrode material used in forming the negative electrode of a lithium-ion secondary battery, and more specifically, to a lithium-containing silicon oxide powder doped with lithium. In addition, in this document, silicon oxide and SiO x for the same meaning. Background technique [0002] Known SiO x It is an excellent negative electrode material for lithium-ion secondary batteries with large capacitance. The SiO x The anode material is made of SiO x The powder, the conductive additive, and the binder are mixed and slurried, and then coated on a current collector made of copper foil or the like and dried to form a film-shaped negative electrode. Among them, SiO x The powder is obtained by heating a mixture of silicon dioxide and silicon under reduced pressure to generate silicon monoxide gas, cooling and precipitating the silicon monoxide gas, and finely pulverizing it. SiO produced ...

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Problems solved by technology

[0005] However, on the other hand, Li doping has the problem that Li doping improves SiO x Reactivity of the powder to air and water, deteriorating the handling properties of the powder

However, in the case of wet cleaning, since the active Li is removed in the form of lithium silicate or LiSi alloy, pure silicon is exposed from the inside of the powder particle to the surface of the particle, resulting in increased reactivity to the electrolyte, sacrificing SiO x The inherent advantage of the powder, namely low reactivity with the electrolyte, results in a drop in initial efficiency as one of the battery properties

[0009] In addition, in wet cleaning, when Li / O increases, the activity against the cleaning solution becomes too high, and the zero-valent Si responsible for the reversible capacity reacts through cleaning, so the battery performance may not be maintained.

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