Separator for lithium ion secondary battery and lithium ion secondary battery comprising the same

1. A lithium ion secondary battery comprising a negative electrode, a positive electrode and a separator interposed between the negative electrode and the positive electrode,

wherein the separator comprises:

a porous film comprising a polymer resin,

wherein the porous film has a first surface and a second surface;

a lithium-providing layer formed on the first surface of the porous film; and

a heat resistant layer formed on the second surface of the porous film, and

wherein the lithium-providing layer comprises composite particles (A) and the heat resistant layer comprises inorganic particles (B) not comprising lithium as an ingredient,

wherein the inorganic particles (B) are present in an amount of 90 wt % or more based on 100 wt % of the heat resistant layer,

the composite particles (A) comprise a core portion comprising lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0<x<2, 0<y<1, 0<z<3) and a shell portion comprising a carbonaceous material with which the core surface is coated at least partially;

the composite particles (A) cause lithium deintercalation at 0.1 V to 2.5 V (vs. Li/Li);

the battery has a positive electrode potential of 3 V or more (vs. Li+/Li); and

the battery has a driving voltage of 2.5 V to 4.5 V,

wherein the composite particles (A) cause lithium deintercalation during the initial charge/discharge of the battery to supplement irreversible capacity of the negative electrode and do not contribute to the battery capacity from the second charge/discharge,

wherein the negative electrode comprises a negative electrode active material comprising Si and/or Sn, or an oxide thereof, and

wherein the composite particles (A) are present in an amount of 90 wt % or more based on 100 wt % of the lithium-providing layer.

2. The lithium ion secondary battery according to claim 1 , wherein the positive electrode comprises, as a positive electrode active material, any one selected from the group consisting of: a lithium manganese oxide represented by the chemical formula of Li 1+x Mn 2−x O 4 (wherein x is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 or LiMnO 2 ; a Ni-site type lithium nickel oxide represented by the chemical formula of LiNi 1−x M x O 2 (wherein M is Mn and x is 0.01 to 0.3); a lithium manganese composite oxide represented by the chemical formula of LiMn 2−x M x O 2 (wherein M=Co, Ni, Fe, Cr, Zn or Ta, and x is 0.01 to 0.1) or Li 2 Mn 3 MO 8 (wherein M=Fe, Co, Ni, Cu or Zn); LiMn 2 O 4 in which Li is partially substituted with an alkaline earth metal ion; LiNi x Mn 2−x O 4 (0.01≤x≤0.6); LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiCoPO 4 , LiFePO 4 , LiNiMnCoO 2 and LiNi 1−x−y−z Co x M1 y M2 z O 2 (wherein each of M1 and M2 is independently selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, each of x, y and z independently represents an atomic proportion of elements forming the oxide, and 0≤x<0.5, 0≤y<0.5, 0≤z<0.5, x+y+z≤1); or a combination of two or more of them.

3. The lithium ion secondary battery according to claim 1 , wherein the lithium-providing layer is patterned to have a non-coated region.

4. The lithium ion secondary battery according to claim 1 , wherein the carbonaceous material coating is formed by carbonization of a carbonaceous precursor.

5. The lithium ion secondary battery according to claim 4 , wherein the carbonaceous precursor is any one selected from the group consisting of pitch, furfuryl alcohol, glucose, sucrose, phenolic resin, phenolic oligomer, resorcinol resin, resorcinol oligomer, phloroglucinol resin, phloroglucinol oligomer and unsaturated hydrocarbon gases, such as ethylene, propylene or acetylene, or a combination of two or more of them.

6. The lithium ion secondary battery according to claim 1 , wherein the shell portion has a thickness of 5 nm to 50 nm.

7. The lithium ion secondary battery according to claim 1 , wherein the heat resistant layer further comprises a binder resin.