Negative electrode for power storage device, method for forming the same, and power storage device
An object is to suppress electrochemical decomposition of an electrolyte solution and the like at a negative electrode in a lithium ion battery or a lithium ion capacitor; thus, irreversible capacity is reduced, cycle performance is improved, or operating temperature range is extended. A negative electrode for a power storage device including a negative electrode current collector, a negative electrode active material layer which is over the negative electrode current collector and includes a plurality of particles of a negative electrode active material, and a film covering part of the negative electrode active material. The film has an insulating property and lithium ion conductivity.
1. A method for forming a negative electrode, comprising:
forming a dispersion solution by dispersing an active material comprising a graphite particle having concavo-convex shape in a solution including one of metal alkoxide and silicon alkoxide, a stabilizing agent, and a solvent;
attaching a gel, formed by hydrolyzing and condensing the one of metal alkoxide and silicon alkoxide in the dispersion solution, on a surface of the active material;
forming an oxide film on the surface by performing heating treatment on the gel, so that a concave portion of the graphite particle is covered by the oxide film;
applying a slurry including the active material with the oxide film and a binder over a current collector; and
baking the slurry.
2. The method according to claim 1 , wherein the oxide film comprises Nb 2 O 5 .
3. The method according to claim 1 , wherein the oxide film comprises silicon oxide.
4. The method according to claim 1 , wherein the heating treatment is performed at more than or equal to 300° C. and less than or equal to 900° C.
5. A power storage device comprising a battery having the negative electrode formed by the method according to claim 1 .
6. A method for forming an active material, comprising:
forming a dispersion solution by dispersing a graphite particle having concavo-convex shape in a solution including one of metal alkoxide and silicon alkoxide, a stabilizing agent, and a solvent;
attaching a gel, formed by hydrolyzing and condensing the one of metal alkoxide and silicon alkoxide in the dispersion solution, on a surface of the graphite particle; and
forming an oxide film on the surface by performing heating treatment on the gel, so that a concave portion of the graphite particle is covered by the oxide film.
7. The method according to claim 6 , wherein the oxide film comprises Nb 2 O 5 .
8. The method according to claim 6 , wherein the oxide film comprises silicon oxide.
9. The method according to claim 6 , wherein the heating treatment is performed at more than or equal to 300° C. and less than or equal to 900° C.
10. A power storage device comprising a battery having the active material formed by the method according to claim 6 .