Anode material for lithium-ion secondary batteries, anode for lithium-ion secondary batteries and lithium-ion secondary batteries using the same, and a method for manufacturing anode material for lithium-ion secondary batteries.

Abstract

To provide a silicon-based negative electrode for a lithium ion secondary battery, high in charge capacity and good in cycle characteristics.SOLUTION: A negative electrode material for a lithium ion secondary battery comprises silicon fine particles each including a plurality of surface pores, the silicon fine particles containing a group 13 element or a group 15 element as a dopant. A method for preparing the negative electrode material for the lithium ion secondary battery includes: a first etching step of immersing silicon fine particles in a solution containing hydrofluoric acid and transition metal ions; a second etching step of adding an oxidizing agent to a mixed solution that has undergone the first etching step and causing a reaction while mixing the oxidizing agent and the mixed solution; an acid treatment step of removing transition metal particles from silicon fine particles by subjecting the silicon fine particles to acid treatment, the silicon fine particles having undergone the second etching step; and a doping step of subjecting silicon fine particles having undergone the acid treatment step to heat treatment while the silicon fine particles are brought into contact with a simple substance comprising an element serving as a dopant or a compound including the element.SELECTED DRAWING: Figure 1

Claims

1. A first etching step involves immersing silicon nanoparticles in a solution containing hydrofluoric acid and transition metal ions to precipitate transition metal particles on the surface of the silicon nanoparticles, and etching the surface of the silicon nanoparticles, where the contact area with the transition metal particles has been oxidized as a result of the precipitation, with hydrofluoric acid. A second etching step involves adding an oxidizing agent to the mixture obtained through the first etching step and reacting them while mixing them, An acid treatment step is performed to remove the transition metal particles from the silicon nanoparticles that have undergone the second etching step by acid treatment, The process includes a doping step in which silicon nanoparticles that have undergone the acid treatment step are heat-treated while in contact with an element that will serve as a dopant, or a compound containing that element, A method for producing a negative electrode material for a lithium-ion secondary electrode, characterized in that the silicon fine particles used in the first etching step are derived from silicon sludge containing carbon-based organic matter, and the silicon sludge is heat-treated to convert the carbon-based organic matter contained in the silicon sludge into graphite before being subjected to the first etching step.

2. The manufacturing method according to claim 1, characterized in that the element that forms the dopant is a Group 15 element.

3. The manufacturing method according to claim 2, characterized in that the element is phosphorus.

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