Separator for lithium secondary battery, manufacturing method therefor, and lithium secondary battery comprising same
A separator for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the separator, where the separator includes a porous polymer substrate having a plurality of pores, and a porous coating layer on at least one surface of the porous polymer substrate. The porous coating layer includes a plurality of inorganic particles and a binder polymer. The binder polymer includes a thermosetting phenolic resin having at least one hydroxyl group and at least one aromatic group. When the separator is exposed to high temperature, due to ignition or the like, the thermosetting phenolic resin in the porous coating layer is thermally cured to form a network structure by virtue of the structural characteristics of the separator. As a result, the separator has improved heat resistance as compared to the conventional separators and shows high adhesion to an electrode.
1. A separator for a lithium secondary battery, comprising:
a porous polymer substrate having a plurality of pores; and
a porous coating layer on at least one surface of the porous polymer substrate,
wherein the porous coating layer comprises a plurality of inorganic particles and a binder polymer,
wherein the binder polymer comprises a thermosetting phenolic resin having at least one hydroxyl group and at least one aromatic group, and
wherein the thermosetting phenolic resin is configured to be thermally cured at 120° C. to 200° C. in the separator to form a network structure.
2. The separator for a lithium secondary battery according to claim 1 , wherein the thermosetting phenolic resin comprises at least one of a novolac-containing phenol resin represented by Chemical Formula 1 and a resol-containing phenol resin represented by Chemical Formula 2:
wherein n is an integer of 1 or more, and R represents any one of H, C 1 -C 100 alkyl, alkoxy and alkenyl groups,
wherein the C 1 -C 100 alkyl, alkoxy and alkenyl groups are optionally substituted,
wherein each of n and m is an integer of 1 or more, and R represents any one of H, C 1 -C 100 alkyl, alkoxy and alkenyl groups,
wherein the C 1 -C 100 alkyl, alkoxy and alkenyl groups are optionally substituted.
3. The separator for a lithium secondary battery according to claim 2 , wherein an amount of the thermosetting phenolic resin is 0.1 wt % to 20 wt % based on 100 wt % of an amount of the inorganic particles.
4. The separator for a lithium secondary battery according to claim 1 , wherein the thermosetting phenolic resin is a phenol-formaldehyde resin.
5. The separator for a lithium secondary battery according to claim 1 , wherein an amount of the thermosetting phenolic resin is 0.1 wt % to 20 wt % based on 100 wt % of an amount of the inorganic particles.
6. The separator for a lithium secondary battery according to claim 1 , wherein the binder polymer further comprises a non-phenolic resin in an amount of 0.1 wt % to 50 wt % based on 100 wt % of an amount of the inorganic particles.
7. The separator for a lithium secondary battery according to claim 1 , wherein the porous polymer substrate has a thickness of 1 μm to 20 μm, and the thickness of the porous coating layer is 0.5 μm to 20 μm based on single surface coating.
8. A lithium secondary battery comprising:
a cathode,
an anode, and
a separator interposed between the cathode and the anode,
wherein the separator is the same as defined in claim 1 .
9. A method for manufacturing a separator for a lithium secondary battery, comprising the steps of:
(S1) preparing an inorganic particle dispersion by dispersing inorganic particles in a first solvent, and dissolving a thermosetting phenolic resin having at least one hydroxyl group and at least one aromatic ring in the inorganic particle dispersion to form a slurry; and
(S2) coating the slurry comprising the inorganic particle dispersion on at least one surface of a porous polymer substrate, and drying the slurry after coating to form a porous coating layer,
wherein the thermosetting phenolic resin is configured to be thermally cured at 120° C. to 200° C. in the separator to form a network structure.
10. The method for manufacturing the separator for the lithium secondary battery according to claim 9 , which further comprises a step of mixing the inorganic particle dispersion of step (S1) with a polymer solution comprising a non-phenolic resin dissolved in a second solvent before step (S2).
11. The method for manufacturing the separator for the lithium secondary battery according to claim 10 , wherein each of the first solvent and the second solvent independently comprises at least one selected from the group consisting of water, C 2 -C 5 alcohols, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethyl formamide, N-methyl-2-pyrrolidone, methyl ethyl ketone and cyclohexane.
12. The method for manufacturing the separator for the lithium secondary battery according to claim 9 , wherein the inorganic particle dispersion further comprises a dispersing agent.
13. The method for manufacturing the separator for the lithium secondary battery according to claim 9 , wherein the thermosetting phenolic resin comprises at least one of a novolac-containing phenol resin represented by Chemical Formula 1 and a resol-containing phenol resin represented by Chemical Formula 2:
wherein n is an integer of 1 or more, and R represents any one of H, C 1 -C 100 alkyl, alkoxy and alkenyl groups,
wherein the C 1 -C 100 alkyl, alkoxy and alkenyl groups are optionally substituted,
wherein each of n and m is an integer of 1 or more, and R represents any one of H, C 1 -C 100 alkyl, alkoxy and alkenyl groups,
wherein the C 1 -C 100 alkyl, alkoxy and alkenyl groups are optionally substituted.
14. The method for manufacturing the separator for the lithium secondary battery according to claim 13 , wherein an amount of the thermosetting phenolic resin is 0.1 wt % to 20 wt % based on 100 wt % of an amount of the inorganic particles.
15. The method for manufacturing the separator for the lithium secondary battery according to claim 9 , wherein an amount of the thermosetting phenolic resin is 0.1 wt % to 20 wt % based on 100 wt % of an amount of the inorganic particles.