Negative electrode active material for secondary battery, and secondary battery using same

1 . A negative electrode active material for a secondary battery comprising:

composite particles including a lithium silicate phase and a silicon phase dispersed in the lithium silicate phase, wherein

the silicon phase has lined portions in the lithium silicate phase,

a maximum diameter D 1 and a minimum diameter D 2 of the lined portions satisfy 3≤D 1 /D 2 ,

the composite particles include a metal Me dispersed in the lithium silicate phase, and

the metal Me is at least one selected from the group consisting of Fe, Pb, Zn, Sn, Cu, Ni, Cr, Zr, and Ti.

2 . The negative electrode active material for a secondary battery of claim 1 , wherein the maximum diameter D 1 is 60 nm or less.

3 . The negative electrode active material for a secondary battery of claim 1 , wherein more than half of the lined portions have a diameter of 20 nm or less.

4 . The negative electrode active material for a secondary battery of claim 1 , wherein the lined portions include a lined portion L 1 and a lined portion L 2 ,

the lined portion L 1 has a diameter of (D 2 +10) nm or more and D 1 nm or less,

the lined portion L 2 has a diameter of D 2 nm or more and less than (D 2 +10) nm,

a difference between the maximum diameter D 1 and the minimum diameter D 2 is more than 10 nm, and

a ratio of NL 2 relative to NL 1 :NL 2 /NL 1 is 5 or more and 20 or less, the NL 2 being a number of the lined portion L 2 , and the NL 1 being a number of the lined portion L 1 .

5 . The negative electrode active material for a secondary battery of claim 1 , wherein particles of the metal Me have an average particle size of 1 nm or more and 100 nm or less.

6 . A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein

the negative electrode includes the negative electrode active material for a secondary battery of claim 1 .