Solid electrolyte separator, secondary battery, battery pack, and vehicle
According to one embodiment, a solid electrolyte separator is provided. The solid electrolyte separator is a sheet containing a solid electrolyte having a lithium ion conductivity. A first lithium ion conductivity in a peripheral edge region along an in-plane direction of the sheet is lower than a second lithium ion conductivity in a central region along the in-plane direction of the sheet.
1. A secondary battery comprising:
a first electrode which is one of a positive electrode and a negative electrode;
a second electrode which is the other of the positive electrode and the negative electrode; and
a solid electrolyte layer which is a sheet comprising a solid electrolyte having a lithium ion conductivity,
wherein a first lithium ion conductivity in a peripheral edge region along an in-plane direction of the sheet is lower than a second lithium ion conductivity in a central region along the in-plane direction of the sheet,
wherein
the solid electrolyte layer has a first surface and a second surface facing the first surface,
at least a portion of the first surface is in contact with the first electrode, at least a portion of the second surface is in contact with the second electrode,
a width of the first electrode along each direction of in-plane direction of the sheet is larger than a width of the second electrode along the each direction,
the peripheral edge region is a region corresponding to a difference between the width of the first electrode and the width of the second electrode and comprises a first portion which comprises a surface in contact with the first electrode and located in the first surface,
the central region is a region corresponding to the width of the second electrode along the each direction and comprises a second portion which comprises a surface in contact with the first electrode and located in the first surface, the second portion further comprises a surface being in contact with the second electrode and located in the second surface, and
a first lithium ion conductivity of the first portion is lower than a second lithium ion conductivity of the second portion.
2. The secondary battery according to claim 1 , wherein
the solid electrolyte layer has a square or rectangular shape,
the first portion has two or more widths along the in-plane directions of the sheet, and
a width of the second electrode along the in-plane direction is larger than a total value of the two or more widths.
3. The secondary battery according to claim 1 , wherein
the solid electrolyte layer has a square or rectangular shape,
the first portion has two or more widths along the in-plane direction of the sheet, and
a ratio of a total value of the two or more widths to a width of the solid electrolyte layer along the in-plane direction is within a range of 1% to 10%.
4. The secondary battery according to claim 1 , wherein
the solid electrolyte layer has a square or rectangular shape,
the first portion has two or more widths along the in-plane direction of the sheet, and
a ratio of a total value of the two or more widths to a width of the second electrode along the in-plane direction is within a range of 0% to 20%.
5. The secondary battery according to claim 1 , wherein the first lithium ion conductivity in the peripheral edge region is not more than 1×10 −10 S/cm, and the second lithium ion conductivity in the central region is not less than 1×10 −4 S/cm.
6. The secondary battery according to claim 1 ,
wherein the negative electrode comprises a negative electrode active material, and
the negative electrode active material comprises at least one selected from the group consisting of lithium titanate having a ramsdellite structure, lithium titanate having a spinel structure, monoclinic titanium dioxide, anatase type titanium dioxide, rutile type titanium dioxide, hollandite type titanium composite oxide, orthorhombic titanium-containing composite oxide, and monoclinic niobium titanium composite oxide.
7. The secondary battery according to claim 1 , further comprising an electrolyte.
8. A battery pack comprising the secondary battery according to claim 1 .
9. The battery pack according to claim 8 , further comprising:
an external power distribution terminal; and
a protective circuit.
10. The battery pack according to claim 8 , comprising plural of the secondary battery, wherein the secondary batteries are electrically connected in series, in parallel, or in combination of series connection and parallel connection.
11. A vehicle comprising the battery pack according to claim 8 .
12. The vehicle according to claim 11 , which comprises a mechanism configured to convert kinetic energy of the vehicle into regenerative energy.