Power storage device
A power storage device which has high charge/discharge capacity and less deterioration in battery characteristics due to charge/discharge and can perform charge/discharge at high speed is provided. A power storage device includes a negative electrode. The negative electrode includes a current collector and an active material layer provided over the current collector. The active material layer includes a plurality of protrusions protruding from the current collector and a graphene provided over the plurality of protrusions. Axes of the plurality of protrusions are oriented in the same direction. A common portion may be provided between the current collector and the plurality of protrusions.
1. A power storage device comprising a negative electrode,
the negative electrode comprising:
an active material layer comprising:
a common portion; and
a plurality of protrusions protruding from the common portion, and
a layer including a graphene over the common portion and the plurality of protrusions.
2. The power storage device according to claim 1 , wherein axes of the plurality of protrusions are oriented in a same direction.
3. The power storage device according to claim 1 , wherein in a lateral cross-sectional shape, an area of a bottom portion of each of the plurality of protrusions which is in contact with the common portion is larger than an area of a top portion of each of the plurality of protrusions.
4. The power storage device according to claim 1 , wherein in a longitudinal cross-sectional shape, a width of a bottom portion of each of the plurality of protrusions which is in contact with the common portion is larger than a width of a top portion of each of the plurality of protrusions.
5. The power storage device according to claim 1 , wherein the common portion or the plurality of protrusions comprise silicon.
6. The power storage device according to claim 1 , wherein the plurality of protrusions each have a columnar shape, a conical or pyramidal shape, a plate-like shape, or a pipe-like shape.
7. The power storage device according to claim 1 , further comprising a protective layer between a top portion of each of the plurality of protrusions and the graphene.
8. The power storage device according to claim 1 , further comprising an insulating layer over the graphene of the negative electrode.
9. A power storage device comprising a negative electrode,
the negative electrode comprising:
a current collector;
a plurality of protrusions over the current collector; and
a layer including a graphene over the current collector and the plurality of protrusions,
wherein each of the plurality of protrusions comprises an active material.
10. The power storage device according to claim 9 , wherein axes of the plurality of protrusions are oriented in a same direction.
11. The power storage device according to claim 9 , wherein in a lateral cross-sectional shape, an area of a bottom portion of each of the plurality of protrusions which is in contact with the current collector is larger than an area of a top portion of each of the plurality of protrusions.
12. The power storage device according to claim 9 , wherein in a longitudinal cross-sectional shape, a width of a bottom portion of each of the plurality of protrusions which is in contact with the current collector is larger than a width of a top portion of each of the plurality of protrusions.
13. The power storage device according to claim 9 , wherein the plurality of protrusions each have a columnar shape, a conical or pyramidal shape, a plate-like shape, or a pipe-like shape.
14. The power storage device according to claim 9 , further comprising a protective layer between a top portion of each of the plurality of protrusions and the graphene.
15. The power storage device according to claim 9 , further comprising an insulating layer over the graphene of the negative electrode.
16. The power storage device according to claim 1 , further comprising a current collector in contact with the active material layer.
17. The power storage device according to claim 1 , the plurality of protrusions are formed by etching.
18. The power storage device according to claim 9 , the plurality of protrusions are formed by etching.
19. The power storage device according to claim 9 , wherein the active material comprises silicon.
20. The power storage device according to claim 19 , wherein the plurality of protrusions comprises phosphorus or boron as an impurity.
21. The power storage device according to claim 9 , wherein the plurality of protrusions has translation symmetry.
22. The power storage device according to claim 1 , wherein in a longitudinal cross-sectional shape, a width of a bottom portion of each of the plurality of protrusions which is in contact with the common portion is 0.1 to 1 μm.
23. The power storage device according to claim 20 , further comprising a second protrusion over and in contact with each of the plurality of protrusions, and
wherein the second protrusion has translation symmetry.
24. The power storage device according to claim 9 ,
wherein the plurality of protrusions each have a prismatic or pyramidal shape, and
wherein a top or an edge of each of the plurality of protrusions is curved.