Composite anode material including surface-stabilized active material particles and methods of making same
Composite anode materials and methods of making same, the anode materials including capsules including graphene, reduced graphene oxide, graphene oxide, or a combination thereof, and particles of an active material disposed inside of the capsules. The particles may each include a core and a buffer layer surrounding the core. The core may include crystalline silicon, and the buffer layer may include a silicon oxide, a lithium silicate, carbon, or a combination thereof.
1. A composite electrode material comprising:
capsules, each capsule comprising one of graphene, reduced graphene oxide, graphene oxide, or a combination thereof; and
at least one active material particle disposed inside of each capsule, the active material particle comprising:
an electrochemically active core; and
a buffer layer that surrounds the core and comprises a silicon oxide, a lithium silicate, or combination thereof;
wherein the buffer layer comprises Li 2 Si 2 O 5 , Li 2 SiO 3 , Li 4 SiO 4 , or combinations thereof.
2. The electrode material of claim 1 , wherein the core comprises crystalline silicon.
3. The electrode material of claim 1 , further comprising a carbon-based material.
4. The electrode material of claim 1 , wherein the buffer layer comprises a matrix.
5. The electrode material of claim 1 , wherein:
the capsules have an average particle size that ranges from about 0.5 μm to about 10 μm; and
the particles have an average particle size that ranges from about 30 nm to about 500 nm.
6. The electrode material of claim 1 , wherein the buffer layer has an average thickness that ranges from about 1 nm to about 50 nm.
7. The electrode material of claim 1 , wherein the buffer layer has an average thickness that ranges from about 5 nm to about 10 nm.
8. An electrode, comprising:
capsules comprising graphene, reduced graphene oxide, graphene oxide, or a combination thereof;
active material particles disposed inside of the capsules, the active material particles comprising silicon particles surrounded by a buffer layer comprising an oxide, a silicate, or a combination thereof; and
a binder;
wherein:
the binder comprises polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(acrylic) acid, polyethylenetetrafluoroethylene (ETFE), polyamides, and polyimides, polyethylene (UHMW), styrene-butadiene rubber, cellulose, polyacrylate rubber, or a mixture thereof; and
the electrode has an internal porosity that ranges from about 40 percent to about 60 percent, as measured by the equation:
Internal
Porosity
(
%
)
=
1
-
(
measured
density
theoretical
density
)
where the measured density is calculated by dividing the mass of a dried electrode by its volume, and the theoretical density is the density of the electrochemically active material that is 100 percent dense.
9. The electrode of claim 8 , wherein:
the buffer layer comprises a silicon oxide, a lithium silicate, or a combination thereof.
10. An electrode, comprising:
capsules comprising graphene, reduced graphene oxide, graphene oxide, or a combination thereof;
active material particles disposed inside of the capsules, the active material particles comprising silicon particles surrounded by a buffer layer comprising an oxide, a silicate, or a combination thereof; and
a binder;
wherein:
the silicon comprises a crystalline silicon; and
the buffer layer comprises Li 2 Si 2 O 5 , Li 2 SiO 3 , Li 4 SiO 4 , or combinations thereof.
11. The electrode of claim 10 , further comprising a carbon-based material.
12. The electrode of claim 10 , wherein the buffer layer comprises the Li 2 Si 2 O 5 .
13. The electrode of claim 10 , wherein the buffer layer comprises the Li 2 SiO 3 .
14. The electrode of claim 10 , wherein the buffer layer comprises the Li 4 SiO 4 .
15. The electrode material of claim 1 , wherein the buffer layer comprises the Li 2 Si 2 O 5 .
16. The electrode material of claim 1 , wherein the buffer layer comprises the Li 2 SiO 3 .
17. The electrode material of claim 1 , wherein the buffer layer comprises the Li 4 SiO 4 .