Nonaqueous electrolyte secondary battery
A nonaqueous electrolyte secondary battery having an electrode group in which a positive electrode plate containing a positive electrode active material and a negative electrode plate containing a negative electrode active material are wound with a separator there between. The positive electrode active material uses a lithium transition metal oxide represented by the formula Li a Ni x M 1−x O 2 (0.9≤a≤1.2, 0.8≤x<1, and M is at least one element of Co, Mn, and Al). The positive electrode plate is provided with a current-collecting tab placed in a position that is 200 mm or more apart from the winding start of the positive electrode plate. The separator has an MD direction tensile strength (S MD )-to-TD direction tensile strength (S TD ) ratio (S MD /S TD ) of from 0.72 to 1.37 and an MD direction tensile elongation (E MD )-to-TD direction tensile elongation (E TD ) ratio (E MD /E TD ) of from 0.34 to 1.29.
1. A nonaqueous electrolyte secondary battery comprising an electrode group in which a positive electrode plate containing a positive electrode active material and a negative electrode plate containing a negative electrode active material are wound with a separator therebetween,
wherein the positive electrode active material uses a lithium transition metal oxide represented by the formula Li a Ni x M 1−x O 2 (0.9≤a≤1.2, 0.8≤x<1, and M is at least one element selected from the group consisting of Co, Mn, and Al),
the positive electrode plate is provided with a current-collecting tab placed in a position that is 200 mm to 450 mm apart from the winding start of the positive electrode plate, and
the separator has an MD direction tensile strength (S MD )-to-TD direction tensile strength (S TD ) ratio (S MD /S TD ) of from 0.72 to 1.37 and an MD direction tensile elongation (E MD )-to-TD direction tensile elongation (E TD ) ratio (E MD /E TD ) of from 0.34 to 1.29.
2. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the MD direction tensile elongation (E MD ) of the separator is 100% or more.
3. The nonaqueous electrolyte secondary battery according claim 1 , wherein the separator includes a heat-resistant layer.
4. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the negative electrode active material contains SiO x (0.5≤x≤1.5).