Lithium secondary battery and cathode of the lithium secondary battery
To provide a lithium secondary battery which has high capacity while maintaining excellent cycle characteristic. The lithium secondary battery cathode of the present invention includes a cathode collector formed of a conductive substance, and a cathode active material layer formed of a sintered lithium composite oxide sheet. The cathode active material layer is bonded to the cathode collector by the mediation of a conductive bonding layer. A characteristic feature of the present invention resides in that the cathode active material layer has a thickness of 30 μm or more, a voidage of 3 to 30%, and an open pore ratio of 70% or higher.
1. A lithium secondary battery cathode comprising:
a cathode collector formed of a conductive substance, and
a cathode active material layer which is formed of a sintered lithium composite oxide sheet having a thickness of 30 μm or more, a voidage of 3 to 30%, and an open pore ratio of 70% or higher, and which is bonded to the cathode collector by the mediation of a conductive bonding layer,
wherein the sintered lithium composite oxide sheet has a layered rock salt structure,
wherein the sintered lithium composite oxide sheet exhibits a ratio of intensity of X-ray diffraction by the (003) plane to intensity of X-ray diffraction by the (104) plane, [003]/[104], of 2 or less,
wherein the intensity of X-ray diffraction is attained by measuring an X-ray diffraction profile of the surface of the sintered lithium composite oxide sheet, and
wherein the (104) plane is oriented in a direction parallel to the surface of the sintered lithium composite oxide sheet.
2. The lithium secondary battery cathode according to claim 1 , wherein the sintered lithium composite oxide sheet has a ratio w/t of 3 or more, wherein t represents the thickness of the sheet, and w represents the minimum size of the sheet as measured in a direction orthogonal to the thickness direction which defines the thickness t.
3. The lithium secondary battery cathode according to claim 1 , wherein the sintered lithium composite oxide sheet has a structure in which numerous primary particles have been bound to one another, and the primary particles have a primary particle size of 5 μm or less.
4. A lithium secondary battery comprising at least the following:
a cathode having a cathode active material layer which is formed of a sintered lithium composite oxide sheet having a thickness of 30 μm or more, a voidage of 3 to 30%, and an open pore ratio of 70% or higher, and a cathode collector bonded to the cathode active material layer by the mediation of a conductive bonding layer;
wherein the sintered lithium composite oxide sheet has a layered rock salt structure,
an anode containing as an anode active material a carbonaceous material or a lithium-occluding substance; and
an electrolyte disposed so as to intervene between the cathode and the anode,
wherein the sintered lithium composite oxide sheet exhibits a ratio of intensity of X-ray diffraction by the (003) plane to intensity of X-ray diffraction by the (104) plane, [003]/[104], of 2 or less,
wherein the intensity of X-ray diffraction is attained by measuring an X-ray diffraction profile of the Mate surface of the sintered lithium composite oxide sheet, and
wherein the (104) plane is oriented in a direction parallel to the surface of the sintered lithium composite oxide sheet.
5. The lithium secondary battery according to claim 4 , wherein the sintered lithium composite oxide sheet has a ratio w/t of 3 or more, wherein t represents the thickness of the sheet, and w represents the minimum size of the sheet as measured in a direction orthogonal to the thickness direction which defines the thickness t.
6. The lithium secondary battery according to claim 4 , wherein the sintered lithium composite oxide sheet has a structure in which numerous primary particles have been bound to one another, and the primary particles have a primary particle size of 5 μm or less.
7. The lithium secondary battery cathode according to claim 1 , wherein the [003]/[104] intensity ratio is 1.4 or less.
8. The lithium secondary battery cathode according to claim 4 , wherein the [003]/[104] intensity ratio is 1.4 or less.