Electrode for secondary battery, secondary battery, and manufacturing method of the electrode and the secondary battery
Electrode 6 for a secondary battery to be laminated with another type of electrode 1 , with separator 20 interposed therebetween, to constitute a battery electrode assembly, is comprised of collector 8 and active material layer 7 formed on collector 8 , and electrode 6 includes a coated part in which active material layer 7 is formed on collector 8 and an uncoated part in which active material layer 7 is not formed on collector 8 . Active material layer 7 includes, in at least a part of the outer peripheral portion of the coated part, high density part 7 a having a smaller thickness and a higher density than those of a portion other than the outer peripheral portion.
1. An electrode for a secondary battery to be laminated with another type of electrode, with a separator interposed therebetween, to constitute a battery electrode assembly, which is comprised of a collector and an active material layer formed on the collector; comprising
a coated part in which the active material layer is formed on the collector; and
an uncoated part in which the active material layer is not formed on the collector,
wherein the active material layer comprises:
in at least a part of an outer peripheral portion of the coated part, a high density part having a smaller thickness and a higher density than those of a portion other than the outer peripheral portion, and
a non-high density part positioned at an outer edge part of the coated part, smaller in thickness than a portion other than the outer peripheral portion, and lower in density than the high density part,
wherein the high density part is positioned closer to the center than the non-high density part in the outer peripheral portion of the coated part.
2. The electrode for the secondary battery according to claim 1 , the electrode being a negative electrode alternately laminated with a positive electrode that is the other type of electrode, with the separator interposed therebetween.
3. The electrode for the secondary battery according to claim 1 , wherein the high density part is positioned at an outer edge part of the coated part.
4. The electrode for the secondary battery according to claim 1 , wherein an average density of the high density part is not less than 110% and not more than 125% of an average density of the portion other than the outer peripheral portion.
5. The electrode for the secondary battery according to claim 1 , wherein:
the part of the electrode other than the outer peripheral portion of the active material layer has a thickness which is not less than 50 μm and not more than 70 μm and an average density which is not less than 1400 kg/m 3 and not more than 1500 kg/m 3 ; and
the high density part is smaller in thickness than the part other than the outer peripheral portion, and has a thickness which is not less than 41.5 μm and not more than 67.5 μm and an average density which is not less than 1550 kg/m 3 and not more than 1750 kg/m 3 .
6. The electrode for the secondary battery according to claim 5 , wherein the active material layer is made of a material including carbon.
7. A secondary battery comprising:
a battery electrode assembly including the electrode for the secondary battery according to claim 1 , which is used as a negative electrode, the separator, and a positive electrode alternately laminated with the negative electrode with the separator interposed therebetween;
an exterior container for housing the battery electrode assembly; and
an electrolyte housed together with the battery electrode assembly in the exterior container.
8. The secondary battery according to claim 7 , wherein:
the positive electrode is comprised of a collector and an active material layer applied on the collector, and the positive electrode includes a coated part in which the active material layer is formed on the collector, and an uncoated part in which the active material layer is not formed on the collector;
an insulating member is disposed to cover a boundary portion between the coated part and the uncoated part; and
the high density part of the negative electrode is provided at a position planarly overlapping a part of the insulating member.
9. The secondary battery according to claim 7 , wherein:
the positive electrode is comprised of a collector and an active material layer applied on the collector, and the positive electrode includes a coated part in which the active material layer is formed on the collector, and an uncoated part in which the active material layer is not formed on the collector;
an insulating member is disposed to cover a boundary portion between the coated part and the uncoated part of the negative electrode; and
the high density part is provided at a position planarly overlapping a part of the insulating member.
10. The secondary battery according to claim 7 , the secondary battery being a lithium ion secondary battery.