Synthesis of metal compounds under carbothermal conditions
View Patent ↗Active materials of the invention contain at least one alkali metal and at least one other metal capable of being oxidized to a higher oxidation state. Preferred other metals are accordingly selected from the group consisting of transition metals (defined as Groups 4-11 of the periodic table), as well as certain other non-transition metals such as tin, bismuth, and lead. The active materials may be synthesized in single step reactions or in multi-step reactions. In at least one of the steps of the synthesis reaction, reducing carbon is used as a starting material. In one aspect, the reducing carbon is provided by elemental carbon, preferably in particulate form such as graphites, amorphous carbon, carbon blacks and the like. In another aspect, reducing carbon may also be provided by an organic precursor material, or by a mixture of elemental carbon and organic precursor material.
1. A method for synthesizing an alkali metal compound of general formula
A a M b (PO 4 ) c Z d ,
wherein
(a) A is selected from the group consisting of Li, Na, K, and mixtures thereof, and 0<a≦8;
(b) M comprises one or more metals, comprising at least one metal which is capable of undergoing to a higher valence state, and 1≦b≦3;
(c) 0<c≦3; and
(d) Z is OH, halogen, or mixtures thereof, and 0<d≦6
comprising:
in a first stage, preparing a metal precursor compound by a process comprising the steps of:
combining starting materials comprising at least one transition metal compound and at least one source of reducing carbon present in an amount at least sufficient to reduce at least one transition metal ion of the at least one transition metal compound in oxidation state without full reduction to elemental state to provide a mixture;
heating the mixture for a time and at a temperature sufficient to form a reaction product comprising a metal precursor compound, wherein at least one metal is reduced in oxidation state during the heating step; and
in a subsequent stage, reacting an alkali metal compound with the metal precursor compound.
2. A method according to claim 1 , wherein the metal precursor compound comprises a transition metal oxide.
3. A method according to claim 1 , wherein the metal precursor compound comprises a transition metal phosphate.
4. A method according to claim 1 , wherein the reducing carbon comprises elemental carbon.
5. A method according to claim 1 , wherein the reducing carbon comprises organic material.
6. A method according to claim 5 , wherein the organic material decomposes during heating to form a decomposition product containing carbon in a form capable of acting as a reductant.
7. A method according to claim 1 , wherein the reducing carbon comprises a carbohydrate.
8. A method according to claim 1 , wherein the reducing carbon comprises sucrose.
9. A method according to claim 1 , wherein in the first stage, heating is carried out in an atmosphere comprising a reducing gas.
10. A method according to claim 9 , wherein the reducing gas comprises hydrogen.
11. A method according to claim 1 , wherein the subsequent stage is carried out with no reduction.
12. A method according to claim 1 , wherein the subsequent stage is carried out in the presence of a source of reducing carbon.
13. A method according to claim 12 , wherein the reducing carbon comprises elemental carbon.
14. A method according to claim 12 , wherein the reducing carbon comprises organic material.
15. A method according to claim 12 , wherein the reducing carbon comprises a carbohydrate.
16. A method according to claim 12 , wherein the reducing carbon comprises sucrose.
17. A method according to claim 12 , wherein the subsequent stage comprises the steps of
combining the metal precursor compound, the alkali metal compound, and the reducing carbon as starting materials; and
heating the mixture for a time and at a temperature sufficient to form a reaction product comprising the alkali metal compound.
18. A method according to claim 1 wherein the alkali metal compound comprises a lithium metal phosphate.