Atomic layer deposition on high-aspect-ratio electrode structures
Battery electrodes using VACNT forests to create 3D electrode nanostructures, and methods of making, are described. The VACNTs are electrically and mechanically attached to the anode or cathode substrates, providing a large area of 3D surfaces for coating with active materials and high-conductivity electron pathways to the cell current collectors. A number of different active materials suitable for anodes and cathodes in lithium-ion batteries may be used to coat the individual carbon nanotubes. The high surface area provided by the VACNT forest and the nano-dimensions of the coated active materials enable both high energy-density and high power-density to be achieved with the same battery. Complete conformal coating of the individual CNTs may be achieved by a number of different methods, and coating with multiple active materials may be used to create nanolaminate coatings having improved electrochemical characteristics over single materials.
1. An anode of a lithium ion battery, comprising:
a substrate, wherein the substrate comprises at least one hole or void, wherein the plurality of vertically aligned carbon nanotubes are not grown in the at least one hole or void, and wherein a perimeter of the at least one hole or void defines an area between 10 and 500 μm 2 ;
a current collector comprising a plurality of vertically aligned carbon nanotubes in a pattern on the substrate, wherein each nanotube of the plurality of vertically aligned carbon nanotubes has an outer surface and a first end, wherein the first end is coupled to the substrate;
an active material layer located on the outer surface of each nanotube of the plurality of vertically aligned carbon nanotubes.
2. The anode of claim 1 , wherein the first end of each nanotube of the plurality of vertically aligned carbon nanotubes is connected to the substrate and a longitudinal axis of each nanotube is perpendicular to a longitudinal axis of the substrate.
3. The anode of claim 1 , wherein the substrate has a first and second side, wherein a first portion of the plurality of vertically aligned carbon nanotubes are connected to the first side of the substrate and a second portion of the plurality of vertically aligned carbon nanotubes are connected to the second side of the substrate.
4. The anode of claim 1 , wherein a distance between adjacent voids is between 25 μm and 100 μm.
5. The anode of claim 1 , wherein the substrate is a patterned substrate.
6. The anode of claim 5 , wherein the patterned substrate is selected from the group consisting of a mesh, a screen, and a foil.
7. The anode of claim 1 , wherein an aspect ratio of the plurality of vertically aligned carbon nanotubes is between 100 and 1500.
8. The anode of claim 1 , wherein the active material layer comprises silicon.
9. The anode of claim 1 , wherein the anode further comprises a second active material layer.
10. The anode of claim 9 , wherein the second active material layer is a protective layer.
11. The anode of claim 9 , wherein the second active material layer comprises SnO x or TiO 2 .
12. The anode of claim 1 , wherein the anode further comprises a layer of Al 2 O 3 .
13. The anode of claim 1 , wherein the active material layer comprises a material selected from the group consisting of SnO 2 , SiO x , RuO 2 , TiO 2 , Cu 2 S, and combinations thereof.
14. The anode of claim 1 , wherein the outer surface of each nanotube of the plurality of vertically aligned carbon nanotubes is functionalized to increase an amount of precursor nucleation sites.
15. The anode of claim 14 , wherein the outer surface is functionalized using a method selected from the group consisting of acid functionalization, oxygen plasma treatment, chemical functionalization, and application of an adhesion layer.
16. The anode of claim 1 , wherein the active material layer is deposited on the outer surface of each nanotube in the plurality of vertically aligned carbon nanotubes by atomic layer deposition.