Positive electrode plates for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary batteries
A positive electrode plate ( 11 ) includes a current collector ( 30 ) and a mixture layer ( 31 ) disposed on the current collector ( 30 ). The mixture layer ( 31 ) has a thin portion ( 32 ) with a thickness of less than 200 μm disposed on an inner coil half of the current collector ( 30 ) and a thick portion ( 33 ) having a larger thickness than the thin portion ( 32 ), the thick portion ( 33 ) having a yield loop height H measured by a stiffness test of 6 mm<H<15 mm.
1. A positive electrode plate for wound nonaqueous electrolyte secondary batteries, comprising:
a current collector, and
a mixture layer disposed on the current collector,
the mixture layer having a thin portion with a thickness of less than 200 μm disposed on an inner coil half of the current collector and a thick portion having a larger thickness than the thin portion, the thick portion having a yield loop height H measured by a stiffness test of 6 mm<H<15 mm.
2. The positive electrode plate for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the thickness of the thick portion is 200 μm or above.
3. The positive electrode plate for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the ratio (a 1 /a 2 ) of a thickness (a 1 ) of the thin portion to a thickness (a 2 ) of the thick portion is 0.4<(a 1 /a 2 )<0.8.
4. The positive electrode plate for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the thin portion is formed only in a region from an inner coil end of the current collector to less than 20% of the length in the winding direction of the current collector.
5. The positive electrode plate for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the mixture layers are disposed on both sides of the current collector,
a thickness (a 1 ) of the thin portion is not less than 100 μm and not more than 180 μm as the total of the thicknesses on both sides of the current collector, and
a thickness (a 2 ) of the thick portion is not less than 220 μm and not more than 320 μm as the total of the thicknesses on both sides of the current collector.
6. A nonaqueous electrolyte secondary battery comprising:
the positive electrode plate for nonaqueous electrolyte secondary batteries described in claim 1 ,
a negative electrode plate, and
a nonaqueous electrolyte.
7. The positive electrode plate for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the thickness of the thick portion is substantially the same along a winding direction.
8. The positive electrode plate for nonaqueous electrolyte secondary batteries according to claim 7 , wherein the mixture layers have a step at the border between the thin portion and the thick portion.
9. The positive electrode plate for nonaqueous electrolyte secondary batteries according to claim 7 , wherein the thin portion is gradually increased in thickness toward the thick portion.