Method for preparing metal oxide nanosheets
The present invention generally relates to a method for preparing metal oxide nanosheets. In a preferred embodiment, graphene oxide (GO) or graphite oxide is employed as a template or structure directing agent for the formation of the metal oxide nanosheets, wherein the template is mixed with metal oxide precursor to form a metal oxide precursor-bonded template. Subsequently, the metal oxide precursor-bonded template is calcined to form the metal oxide nanosheets. The present invention also relates to a lithium-ion battery anode comprising the metal oxide nanosheets. In a further preferred embodiment, the battery anode may comprising reduced template, which is reduced graphene oxide (rGO) or reduced graphite oxide.
1. A method of preparing metal oxide nanosheets comprising:
a) mixing a template with at least one metal oxide precursor at a temperature between 20° C. to 50° C. to form a metal oxide precursor-bonded template, wherein the at least one metal oxide precursor is selected from the group consisting of metal halide, metal alkoxide, metal nitrate, metal diketone (metal dione), metal salt of a saturated fatty acid and combinations thereof; and wherein the at least one metal oxide precursor comprises a metal selected from groups 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 of the Periodic Table of Elements; and
b) calcining the metal oxide precursor-bonded template obtained in operation a) to form the metal oxide nanosheets, wherein the metal oxide nanosheets have a thickness of 0.5 nm to 10 nm.
2. The method according to claim 1 , wherein the template is a two-dimensional carbonaceous material with surface functional groups selected from graphite oxide and graphene oxide (GO).
3. The method according to claim 1 , wherein the at least one metal oxide precursor is selected from the group consisting of NbCl 5 , Nb(V) ethoxide, Ti(IV) ethoxide, Ti(V) butoxide, Fe(II) chloride, Fe(III) chloride, Fe(II) methoxide, Fe(III) ethoxide, Fe(II) acetylacetonate, Fe(III) acetylacetonate, tin(II) chloride, dibutyltin dilaureate, Ni(II) chloride, Ni(II) ethoxide, Ni(II) acetylacetonate, Co(II) chloride, Co(II) methoxide, Co(II) acetylacetonate, Mn(II) chloride, Mn(II) methoxide, Mn(II) acetylacetonate, Zr(IV) chloride, Zr(IV) propoxide and combinations thereof.
4. The method according to claim 1 , wherein the calcining operation is undertaken at a temperature in the range from 250° C. to 900° C. or wherein the calcining step is undertaken in the presence of a gas selected from the group consisting of air, oxygen, nitrogen, argon, helium, hydrogen, nitrogen and combinations thereof.
5. The method according to claim 1 , further comprising the operation of a1) pre-calcining the metal oxide precursor-bonded template.
6. The method according to claim 5 , wherein the pre-calcining operation a1) is undertaken at a temperature in the range from 250° C. to 900° C.
7. The method according to claim 5 , wherein the pre-calcining operation a1) is undertaken in the presence of gas that is selected from the group consisting of air, oxygen, nitrogen, argon, helium, hydrogen, nitrogen and combinations thereof.
8. The method according to claim 1 , further comprising the operation of adding a doping agent in said mixing step a) to form the metal oxide precursor-bonded template or wherein the metal oxide nanosheets obtained in operation b) are doped binary oxide nanosheets.
9. The method according to claim 8 , wherein the doping agent is a transition metal precursor and wherein the transition metal element of said transition metal precursor is selected from groups 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 of the Periodic Table of Elements or wherein the doping agent is present in a doping ratio in the range of 0.01 to 0.5.
10. The method according to claim 1 , comprising mixing a template with two metal oxide precursors in said mixing operation a) in a precursor atomic ratio to form the metal oxide precursor-bonded template or wherein the metal oxide nanosheets obtained in operation b) are ternary oxide nanosheets.
11. The method according to claim 10 , wherein the precursor atomic ratio of transition metals in the ternary oxide nanosheets is in the range of 1:20 to 20:1.