Porous silicon particles and porous silicon-composite particles

Abstract

The present invention addresses the problem of obtaining porous silicon particles and porous silicon-composite particles that are suitable for use, for example, in a negative-electrode material for a lithium-ion battery that has high capacity and good cycle characteristics. In order to solve said problem, the present invention uses porous silicon particles (1), each of which comprises a plurality of silicon microparticles (3) joined together with a contiguous void and is characterized in that: the mean (x) of the particle diameters or rod diameters of said silicon microparticles is between 2 nm and 2 µm, inclusive; the standard deviation (sigma) of the particle diameters or rod diameters of the silicon microparticles is between 1 and 500 nm, inclusive; and the quotient (sigma / x) of said standard deviation (sigma) and mean (x) is between 0.01 and 0.5, inclusive. Alternatively, porous silicon-composite particles, each of which comprises a plurality of silicon microparticles and a plurality of silicon-compound particles joined together with a contiguous void and is characterized by having characteristics similar to the above, may also be used.

Description

technical field [0001] The present invention relates to porous silicon particles used in negative electrodes for lithium ion batteries and the like. The porous silicon particles of the present invention can be used in capacitors, lithium ion capacitors, and silicon semiconductors for solar cells. Background technique [0002] Conventionally, lithium ion batteries using various carbon-based materials such as natural graphite, artificial graphite, amorphous carbon, and mesophase carbon, lithium titanate, tin alloy, etc., as negative electrode active materials have been put into practical use. In addition, an operation of kneading a negative electrode active material, a conductive auxiliary agent such as carbon black, and a resin binder to prepare a slurry, coating and drying on a copper foil, and forming a negative electrode was also performed. [0003] On the other hand, for the purpose of increasing the capacity, negative electrodes for lithium ion batteries using metals or...

AI Technical Summary

Problems solved by technology

However, since the volume of silicon that has absorbed lithium ions expands to about four times that of silicon before storage, the negative electrode that uses silicon as the negative electrode active material repeatedly expands and contracts during charge and discharge cycles.

As a result, peeling of the negative electrode active material occurs, and there is a problem that the lifetime is extremely short compared to conventional negative electrodes containing carbon-based active materials.

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