Electrode material with enhanced ionic transport properties
View Patent ↗Materials useful as electrodes for lithium batteries have very good electronic and ionic conductivities. They are fabricated from a starting mixture which includes a metal, a phosphate ion, and an additive which enhances the transport of lithium ions in the resultant material. The mixture is heated in a reducing environment to produce the material. The additive may comprise a pentavalent metal or a carbon. In certain embodiments the material is a two-phase material. Also disclosed are electrodes which incorporate the materials and lithium batteries which incorporate those electrodes.
1. An electroactive material comprising:
a first phase comprising a lithiated olivine metal phosphate comprising a first metal M;
a second phase having an ionic conductivity greater than the ionic conductivity of the first phase; and
an additive in at least one of the first and second phases, the additive comprising a metal different from the first metal;
characterized in that when incorporated into a cathode of a lithium battery, the electroactive material has a lithium ion conductivity in the range of 10 −6 S/cm to 5×10 −4 S/cm.
2. The material of claim 1 , wherein the additive is in the second phase.
3. The material of claim 2 , wherein the additive comprises a metal having a +5 oxidation state, but not a +6 oxidation state.
4. The material of claim 2 , wherein the additive comprises one or more of V, Mo, and Nb.
5. The material of claim 4 , wherein the additive is V.
6. The material of claim 1 , wherein the additive is in the first phase.
7. The material of claim 6 , wherein the additive comprises a metal having a +5 oxidation state, but not a +6 oxidation state.
8. The material of claim 6 , wherein the additive comprises one or more metals selected from the group consisting of V, Mo, and Nb.
9. The material of claim 8 , wherein the additive is V.
10. The material of claim 8 , wherein the additive comprises V and Nb or the additive comprises Mo and Nb.
11. The material of claim 6 , wherein the additive substitutes for at least a portion of the phosphorous in the material.
12. The material of claim 6 , wherein the additive substitutes for a portion of the metal M in the material.
13. The material of claim 1 , characterized in that when incorporated into a cathode of a lithium ion battery, the electronic conductivity of the material is in the range of 10 −7 S/cm to 10 −4 S/cm.
14. The material of claim 1 , wherein the metal M is iron.
15. The material of claim 1 , wherein the second phase includes one or more phosphates, partially reduced phosphate and phosphides.
16. The material of claim 1 , wherein the second phase includes one or more of Fe 2 P 2 O 7 ; FeP; Fe 2 P; Fe 3 P.
17. The material of claim 1 , wherein the first phase comprises 80-95 mole percent of the material and the second phase comprises 5-20 mole percent of the material.
18. An electrode which includes the material of claim 1 .
19. An electroactive material comprising:
a lithiated olivine metal phosphate comprising a metal M; and
V and Nb, wherein the material comprises a first phase comprising the lithiated olivine metal phosphate and a second phase having an ionic conductivity greater than the ionic conductivity of the first phase; and when incorporated into a cathode of a lithium battery, the electroactive material has a lithium ion conductivity in the range of 10 −6 S/cm to 5×10 −4 S/cm.
20. The material of claim 19 wherein the metal M comprises Fe.
21. The material of claim 19 , wherein the second phase includes one or more phosphates, partially reduced phosphates and phosphides.
22. The material of claim 19 , wherein the second phase comprises one Or more of Fe 2 P 2 O 7 ; FeP; Fe 2 P; Fe 3 P.
23. The material of claim 19 , wherein the first phase comprises 80-95 mole percent of the material and the second phase comprises 5-20 mole percent of the material.
24. The material of claim 19 , wherein V is a dopant.
25. The material of claim 19 , wherein Nb is a dopant.
26. The material of claim 19 , wherein V substitutes for at least a portion of the phosphorous in the material.
27. The material of claim 19 , wherein V substitutes for a portion of the metal M in the material.
28. The material of claim 19 , wherein Nb substitutes for at least a portion of the metal M in the material.
29. The material of claim 19 , wherein Nb substitutes for at least a portion of the phosphorous in the material.
30. An electrode which includes the material of claim 19 .