| abstract |
The present invention provides a separator that can be used in a secondary battery such as a non-aqueous electrolyte secondary battery, and a secondary battery including the separator. The spacer of the present invention has a first layer composed of a porous polyolefin, and is a parameter X calculated by the following formula from MDtanδ as tanδ of MD and TDtanδ as tanδ of TD obtained by viscoelasticity measurement at a frequency of 10 Hz and a temperature of 90° C. is 20 or less, the tear strength of the first layer measured by the Ellomondo tear method (in accordance with JIS K 7128-2) is 1.5 mN/μm or more, and the tear strength of the first layer by the right-angle tear method is 1.5 mN/μm or more. In the load-tensile elongation curve of the tear strength measurement of one layer (according to JIS K 7128-3), the value E of the tensile elongation from the moment when the load reaches the maximum load to the decay to 25% of the maximum load is 0.5 mm or more. X=100×|MDtanδ−TDtanδ|÷{(MDtanδ+TDtanδ)÷2}. |