ANODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING SAME
An embodiment of the present invention provides an anode active material for a lithium secondary battery which is a porous silicon-carbon-based composite in which a plurality of nano-silicon particles are embedded in a carbon-based material, the composite having a plurality of pores, wherein the carbon-based material comprises graphite particles, soft carbon, hard carbon, or a combination thereof, and the soft carbon, in the carbon-based material, is in the form of a carbon layer.
1 . An anode active material for a lithium secondary battery, comprising
a porous silicon-carbon-based composite in which a plurality of nano-silicon particles are embedded in a carbon-based material,
wherein the carbon-based material comprises graphite particles, soft carbon, hard carbon, or a combination thereof, and
the soft carbon, in the carbon-based material, is in the form of a carbon layer.
2 . The anode active material of claim 1 , wherein the graphite particles, hard carbon, or a combination thereof are included in the carbon layer.
3 . The anode active material of claim 2 , wherein a softening point of the pitch is 250° C. or higher.
4 . The anode active material of claim 3 , wherein a porosity of the anode active material is 30 volume % or less based on the total volume of the anode active material.
5 . The anode active material of claim 4 , wherein a specific surface area (BET) of the anode active material is 5.0 m 2 /g or less.
6 . The anode active material of claim 5 , wherein an expansion rate based on the 50 th cycle of the anode active material is 70% or less.
7 . The anode active material of claim 6 , wherein a content of the nano-silicon is 25 wt % to 50 wt % based on 100 wt % of the porous silicon-carbon-based composite.
8 . A method of preparing an anode active material for a lithium secondary battery, comprising
mixing nano-silicon particles and a carbon-based raw material by dry milling to prepare a porous silicon-carbon-based mixture;
mixing the porous silicon-carbon-based mixture with an aqueous binder to prepare a mixed powder;
mixing the mixed powder with distilled water to prepare a mixed solution;
spray-drying the mixed solution to prepare primary particles;
inserting the primary particles in a mold and press-molding to prepare a molded body;
heat-treating the molded body; and
pulverizing and sieving the heat-treated molded body.
9 . The method of claim 8 , wherein the carbon-based raw material comprises graphite particles, pitch, or a combination thereof.
10 . The method of claim 9 , wherein
before the preparing of the molded body,
the pitch exists in the form of powder particles, and the particle diameter (D50) of the pitch is less than 2 μm.
11 . The method of claim 9 , wherein a softening point of the pitch is 250° C. or higher.
12 . The method of claim 11 , wherein
the preparing of the molded body is performed
in a temperature range of 50 to 100° C. or higher than the softening point of the pitch.
13 . The method of claim 12 , wherein
in the preparing of the molded body,
the pitch has a viscosity.
14 . The method of claim 9 , wherein
after heat-treating of the molded body,
the pitch exists in the shape of a solidified carbon layer.
15 . The method of claim 14 , wherein
by heat-treating of the molded body,
the pitch is carbonized into soft carbon, and the aqueous binder is carbonized into hard carbon.
16 . The method of claim 9 , wherein
the heat-treating the molded body is performed in an inert atmosphere and at less than 1000° C.
17 . A lithium secondary battery, comprising
a cathode;
an anode; and
an electrolyte,
wherein the anode comprises the anode active material for a lithium secondary battery of claim 1 .