Lithium-doped silicon-based oxide negative electrode active material, method of preparing the same, and negative electrode and secondary battery including the same

1 . A negative electrode active material comprising:

negative electrode active material particles including a silicon oxide (SiO x , 0<x≤2) and at least one lithium silicate selected from Li 2 SiO 3 , Li 2 Si 2 O 5 , and Li 4 SiO 4 in at least a part of the silicon oxide,

wherein when a signal generated in a region of 200 to 600 cm −1 according to a Raman spectrum is subjected to deconvolution into three peaks, which are set to peak A, peak B, and peak C from lowest to highest of an absolute value of a wavenumber, the negative electrode active material particles satisfy the following Relations 1, 2, and 3:

0.36≤ D (= C′/B ′- C″/B ″)≤0.92  [Relation 1]

wherein

D is a difference value of a peak area ratio (C″/B″) from a peak intensity ratio (C′/B′),

the peak intensity ratio (C′/B′) is a ratio of an intensity of the peak C to an intensity of the peak B, and

the peak area ratio (C″/B″) is a ratio of an area of the peak C to an area of the peak B,

1.13≤peak intensity ratio ( C′/B ′)≤2.82  [Relation 2]

wherein the peak intensity ratio (C′/B′) is a ratio of the intensity of the peak C to the intensity of the peak B, and

0.37≤peak area ratio ( C″/B ″)≤2.46  [Relation 3]

wherein the peak area ratio (C″/B″) is a ratio of the area of the peak C to the area of the peak B, and

wherein the peak C is positioned at a region of 471.9 cm −1 or less, and is derived from amorphous Si and amorphous Si of the lithium silicate, and

wherein a content of amorphous Si is larger than a content of crystalline Si in the negative electrode active material particles.

2 . The negative electrode active material of claim 1 , wherein the negative electrode active material particles include 10 to 100 wt % of the lithium silicate with respect to a total weight.

3 . The negative electrode active material of claim 1 , wherein the negative electrode active material particles have a peak area ratio H/I according to an X-ray diffraction analysis method of less than 5.54, wherein H is an area of a Li 2 Si 2 O 5 peak positioned at 24.9±0.3°, and I is an area of a Li 2 SiO 3 peak positioned at 26.9+0.3° in X-ray diffraction analysis.

4 . The negative electrode active material of claim 1 , wherein the negative electrode active material particles have a peak area ratio G/H according to the X-ray diffraction analysis method of less than 45.99, wherein G is an area of a Si peak positioned at 28.4+0.3°, and H is an area of a Li 2 Si 2 O 5 peak positioned at 24.9±0.3° in the X-ray diffraction analysis.

5 . The negative electrode active material of claim 1 , wherein the negative electrode active material particles have a peak area ratio G/I according to the X-ray diffraction analysis method of less than 8.75, wherein G is an area of a Si peak positioned at 28.4±0.3°, and I is an area of a Li 2 SiO 3 peak positioned at 26.9±0.3° in the X-ray diffraction analysis.

6 . The negative electrode active material of claim 5 , wherein the peak area ratio G/I according to the X-ray diffraction analysis method is less than 1.1.

7 . The negative electrode active material of claim 1 , wherein the negative electrode active material particles include 25 wt % or less of Li 4 SiO 4 with respect to the total weight.

8 . The negative electrode active material of claim 1 , wherein the negative electrode active material includes 50 wt % or more of the negative electrode active material particles with respect to the total weight.

9 . A negative electrode comprising a negative electrode active material layer comprising: the negative electrode active material of claim 1 and a water-based binder.

10 . A lithium secondary battery comprising: the negative electrode of claim 9 ; a positive electrode; a separator positioned between the negative electrode and the positive electrode; and an electrolyte.