Separators improved thermal resistance and secondary battery comprising same
The present invention relates to a separator including a coating layer and a substrate, wherein phase-change peak temperatures measured by differential scanning calorimetry (DSC) at the time of a first temperature increase and at the time of a second temperature increase satisfy specific ranges, a method of producing the same, and an electrochemical device including the same. More particularly, the present invention relates to a separator that has improved thermal resistance and thus may improve battery safety and implement stable movement of lithium ions and a lithium secondary battery including the same.
1. A separator comprising:
a porous substrate; and
a coating layer formed on both surfaces of the porous substrate and consisting of a binder and inorganic particles,
wherein a thickness of the coating layer is 1.8 μm to 3 μm,
wherein the binder is nanofiber cellulose,
wherein the inorganic particle is boehmite,
wherein the separator has a Gurley permeability of 206 sec/100 cc or less when measured according to ASTM D726,
wherein the separator satisfies the following Equation 1,
12 ≤ΔT=T 1 −T 2 ≤30 [Equation 1]
wherein T 1 is a phase-change peak temperature (melting temperature (T m )) of the separator measured at the time of a first temperature increase, and T 2 is a phase-change peak temperature (melting temperature (T m )) of the separator measured at the time of a second temperature increase performed after cooling the separator subjected to the first temperature increase, the phase-change peak temperature being measured by differential scanning calorimetry (DSC).
2. The separator of claim 1 , wherein an average particle size of the inorganic particles is 40 nm to 1,000 nm.
3. The separator of claim 1 , wherein the inorganic particles and the binder are included in amounts of 50 to 99.9 wt % and 0.1 to 50 wt %, respectively, with respect to a total weight of the coating layer.
4. The separator of claim 1 , wherein the separator has a thermal shrinkage rate of 7% or less when measured in a machine direction (MD) and a transverse direction (TD) after being maintained at 130° C. for 1 hour.
5. The separator of claim 1 , wherein the separator has a thermal shrinkage rate of 4% or less when measured in a machine direction (MD) and a transverse direction (TD) after being left at 130° C. for 1 hour.
6. A lithium secondary battery comprising the separator of claim 1 .