| CPC H01M 4/48 (2013.01) [H01M 4/366 (2013.01); H01M 4/625 (2013.01); H01M 2004/021 (2013.01); H01M 2004/027 (2013.01)] | 16 Claims |

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1. A negative electrode material for a secondary battery, comprising:
a matrix containing silicon oxide, and a composite oxide of a doping element; wherein the doping element is magnesium (Mg), and
silicon nanoparticles dispersed and embedded in the matrix;
wherein a hardness and a Young's modulus measured by a nanoindentation test are 4.0 GPa or more and 40 GPa or more, respectively, and in an X-ray diffraction pattern using a CuKα ray, a ratio (A1/A2) is 0.8 to 6, wherein A1 is an area of a first peak present in a region where a diffraction angle 2θ is 10° to 27.4°, and A2 is an area of a second peak present in a region where the diffraction angle 2θ is 28±0.5°, and
wherein the negative electrode material satisfies the following Expression 3:
B/A≤0.65 (Expression 3)
wherein A is an average value (A) obtained by averaging contents (wt %) of the doping element measured at 100 random points based on a cross section crossing the center of the negative electrode material, and B is a standard deviation (B) of the contents of the doping element.
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