Lithium metal phosphate, its preparation and use
A lithium transition metal phosphate material comprising lithium iron phosphate doped with very precise amounts of aluminium dopant, the material having formula Li y Fe 1-x Al x PO 4 , in which 0.8≤y≤1.2 and 0.0120≤x≤0.0180. When x is within this range, the capacity of the material can be improved, and good or excellent distribution of aluminium in the lithium metal phosphate is observed.
1. A particulate carbon-coated lithium metal phosphate having the formula
Li y Fe 1-x Al x PO 4
in which 0.8≤y≤1.2 and 0.0120≤x≤0.0180.
2. The particulate carbon-coated lithium metal phosphate according to claim 1 , in which 0.0130≤x≤0.0170.
3. The particulate carbon-coated lithium metal phosphate according to claim 1 , in which 0.9≤y≤1.1.
4. The particulate carbon-coated lithium metal phosphate according to claim 1 , having the formula LiFe 1-x Al x PO 4 .
5. The particulate carbon-coated lithium metal phosphate according to claim 1 , wherein the lithium metal phosphate has a crystallite size determined by Rietveld analysis of 60 nm or more.
6. The particulate carbon-coated lithium metal phosphate according to claim 1 which is prepared by a solid state process.
7. A solid-state process for preparing the particulate carbon-coated lithium metal phosphate of claim 1 , the process comprising
(i) a milling step in which lithium-containing precursor, iron-containing precursor, aluminium-containing precursor and carbon-containing precursor are combined and subjected to milling; and
(ii) a calcination step in which the product of the milling step is calcined to provide the particulate carbon-coated lithium metal phosphate.
8. The process according to claim 7 wherein at least 100 kWh of energy is delivered during the milling treatment per kilogram of solids being milled.
9. The process according to claim 7 in which the aluminium-containing precursor is AbO 3 or Al(OH) 3 .
10. The process according to claim 7 , further comprising forming an electrode comprising the carbon-coated lithium metal phosphate.
11. The process according to claim 10 , further comprising constructing a battery including the electrode.
12. A particulate carbon-coated lithium metal phosphate obtained or obtainable by a process according to claim 7 .
13. A method for preparing an electrode for a secondary lithium ion battery, comprising:
(i) forming a slurry of the particulate carbon-coated lithium metal phosphate according to claim 1 ; and
(ii) applying the slurry to the surface of a current collector.
14. An electrode for a secondary lithium ion battery comprising particulate carbon-coated lithium metal phosphate according to claim 1 .
15. A secondary lithium ion battery comprising the electrode according to claim 14 .
16. The process according to claim 7 , wherein the aluminium-containing precursor is Al(OH) 3 .