US 9,252,419 B2Granted

Positive electrode for lithium secondary battery, manufacturing method thereof, and lithium secondary battery

AssigneeSemiconductor Energy Laboratory Co., Ltd.

InventorsTakuya Miwa, Nobuhiro Inoue, Kuniharu Nomoto, Junpei Momo

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Abstract

Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.

Claims16

Dependent claims

A positive electrode for a lithium secondary battery, comprising:

a positive electrode current collector;
and
a positive electrode active material layer over the positive electrode current collector,
wherein the positive electrode active material layer includes:
a rectangular parallelepiped or substantially rectangular parallelepiped particle of a lithium-containing composite oxide having an olivine structure;
and
a graphene oxide, and
wherein a b-axis of the rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide having the olivine structure is oriented vertically to a surface of the positive electrode current collector,
wherein a number of rectangular parallelepiped or substantially rectangular parallelepiped particle having b-axis thereof oriented vertically to the surface of the positive electrode current collector is larger than a number of rectangular parallelepiped or substantially rectangular parallelepiped particle oriented in other axes directions, and
wherein a peak intensit ratio of a (020) diffraction to a (101) diffraction of the lithium-containing composite oxide having the olivine structure in a X-ray diffraction spectrum is greater than or equal to 4.5 and less than or equal to 5.5.

7 more elements

A lithium secondary battery, comprising:

a negative electrode;
an electrolyte solution;
and
a positive electrode comprising:
a positive electrode current collector;
and
a positive electrode active material layer over the positive electrode current collector,
wherein the positive electrode active material layer includes:
a rectangular parallelepiped or substantially rectangular parallelepiped particle of a lithium-containing composite oxide having an olivine structure;
and
a graphene oxide, and
wherein a b-axis of the rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide having the olivine structure is oriented vertically to a surface of the positive electrode current collector,
wherein a number of rectangular parallelepiped or substantially rectangular parallelepiped particle having b-axis thereof oriented vertically to the surface of the positive electrode current collector is larger than a number of rectangular parallelepiped or substantially rectangular parallelepiped particle oriented in other axes directions, and
wherein a peak intensity ratio of a (020) diffraction to a (101) diffraction of the lithium-containing composite oxide having the olivine structure in a X-ray diffraction spectrum is greater than or equal to 4.5 and less than or equal to 5.5.

11 more elements

Dependencies are inferred from the claim text.