Secondary cell and method for manufacturing same
The purpose of the present invention is to provide a secondary cell in which a decrease in energy density is inhibited. In order to achieve this purpose, this secondary cell has a positive electrode in which a positive electrode active material layer is provided on a positive electrode collector, and a negative electrode in which a negative electrode active material layer is provided on a negative electrode collector; the positive electrode active material layer and the negative electrode active material layer are laminated so as to face each other with a separator interposed therebetween; the negative electrode active material layer has a greater area than the positive electrode active material layer; and a thin section is provided in at least a part of the negative electrode active material layer at a location where the negative electrode active material layer does not face the positive electrode active material layer.
1. A secondary cell comprising:
a positive electrode in which a positive electrode active material layer is provided on a positive electrode collector; and
a negative electrode in which a negative electrode active material layer is provided on a negative electrode collector, wherein
the positive electrode active material layer and the negative electrode active material layer are stacked in such a way as to face each other with a separator interposed therebetween, the negative electrode active material layer has a larger area than the positive electrode active material layer, and a thin section is provided in at least a part of the negative electrode active material layer at a location of the negative electrode active material layer that does not face the positive electrode active material layer,
the thin section is located within 2 mm from an end of the positive electrode active material layer from a position immediately under an end of the positive electrode active material layer, and a deepest portion of the thin section has a depth which is 10% or more and 90% or less of thickness of the negative electrode active material layer from a surface of the negative electrode active material layer.
2. The secondary cell according to claim 1 , wherein
the thin section is formed over a whole periphery of the positive electrode.
3. The secondary cell according to claim 1 , wherein
the negative electrode active material layer includes silicon or silicon oxide.
4. The secondary cell according to claim 1 , wherein
the thin section has a U-shaped, wedge-shaped, triangular, or rectangular cross-section.
5. The secondary cell according to claim 1 , wherein
the negative electrode includes negative electrode active material layers formed on both surfaces of a collector, and the thin section is formed on each of the negative electrode active material layers on the both surfaces.
6. The secondary cell according to claim 1 , wherein
the secondary cell is a lithium-ion secondary cell.
7. The secondary cell according to claim 6 , wherein
an active material included in the positive electrode active material layer is a layered oxide-based material being Li transition metal oxide, a spinel-based material, an olivine-based material, an olivine fluoride-based material, a mixture of these materials, a vanadium oxide-based material, or a radical material.
8. The secondary cell according to claim 7 , wherein
an active material included in the negative electrode active material layer is silicon, silicon oxide, a carbon material, metal (including an alloy) which can be alloyed with lithium, metal oxide which can occlude and release lithium ions, or a material in which these materials are mixed.
9. The secondary cell according to claim 1 , wherein
a plurality of layers of electrode stacks in which the positive electrode, the separator, and the negative electrode are stacked in this order are stacked.
10. A method for manufacturing a secondary cell, comprising:
producing at least one electrode stack in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween in such a way that active material layer surfaces face each other, the negative electrode including a thin section in at least a part of a negative electrode active material layer having a larger area than the positive electrode, at a location that does not face the positive electrode;
wrapping the electrode stack with an outer package except for an injection hole; and
injecting electrolyte into the outer package from the injection hole,
wherein the thin section is located within 2 mm from an end of the positive electrode active material layer from a position immediately under an end of the positive electrode active material layer, and a deepest portion of the thin section has a depth which is 10% or more and 90% or less of thickness of the negative electrode active material layer from a surface of the negative electrode active material layer.
11. A negative electrode being used in a secondary cell, wherein
an active material layer of the negative electrode has a larger area than a positive electrode active material layer, and includes a thin section in at least a part of a location that does not face the positive electrode active material layer,
wherein the thin section is located within 2 mm from an end of the positive electrode active material layer from a position immediately under an end of the positive electrode active material layer, and a deepest portion of the thin section has a depth which is 10% or more and 90% or less of thickness of the negative electrode active material layer from a surface of the negative electrode active material layer.