Separator and electrochemical device comprising same
A separator including a porous polymer substrate, and a porous coating layer, and an electrochemical device comprising the same. The porous coating layer includes P(VDF-TrFE-CTFE) and PVDF-CTFE as a binder polymer. The separator has a lower resistance by changing the characteristics of the binder polymer.
1. A separator for an electrochemical device, comprising:
a porous polymer substrate; and
a porous coating layer on at least one surface of the porous polymer substrate,
wherein the porous coating layer comprises a binder polymer,
wherein the binder polymer comprises poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene P (VDF-TrFE-CTFE) and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE),
wherein a β-phase amount of the P (VDF-TrFE-CTFE) is 0.90 or above, and
wherein a weight ratio of the P (VDF-TrFE-CTFE) to the PVDF-CTFE is 35:65 to 87:13.
2. The separator for the electrochemical device according to claim 1 , wherein the weight ratio of the P (VDF-TrFE-CTFE) to the PVDF-CTFE is 50:50 to 80:20.
3. The separator for the electrochemical device according to claim 1 , wherein the P (VDF-TrFE-CTFE) comprises 10 wt % or less of CTFE based on a total weight of the P (VDF-TrFE-CTFE).
4. The separator for the electrochemical device according to claim 1 , wherein the porous coating layer is 1 μm to 10 μm in thickness.
5. The separator for the electrochemical device according to claim 1 , wherein the porous coating layer further comprises inorganic particles.
6. The separator for the electrochemical device according to claim 5 , wherein a weight ratio of the inorganic particles to the binder polymer is 90:10 to 60:40.
7. The separator for the electrochemical device according to claim 5 , wherein the porous coating layer is 1 μm to 15 μm in thickness.
8. The separator for the electrochemical device according to claim 1 , wherein the separator has a resistance of 0.8 ohm or less, and a Lami Strength with an electrode of 50 gf/25 mm or above.
9. An electrochemical device, comprising:
a positive electrode;
a negative electrode; and
a separator interposed between the positive electrode and the negative electrode,
wherein the separator is defined according to claim 1 .
10. The electrochemical device according to claim 9 , wherein the electrochemical device is a lithium secondary battery.