Electrode material with enhanced ionic transport properties
AssigneeA123 Systems, Inc.
InventorsMichael R. Wixom, Chuanjing Xu
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Abstract
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.
Claims31
A method for synthesizing a material, said method comprising the steps of:
- providing a starting mixture which includes lithium, a metal M, substantially all of which is in a first oxidation state, a phosphate ion, and an additive comprising a metal which is different from said metal M, which additive enhances the transport of lithium ions in a material prepared by this method, as compared to a material prepared in the absence of said additive;
- heating said mixture in a reducing environment so as to produce a material which comprises a first phase comprising a lithiated olivine metal phosphate, and a second phase having an ionic conductivity which is greater than the ionic conductivity of said first phase, wherein substantially all of the metal M is in a second oxidation which is lower than said first oxidation state, and the ratio of lithium to metal is less than or equal to 1.05.
A material comprising:
- a first phase comprising a lithiated olivine metal phosphate;
- and
- a second phase having an ionic conductivity which is greater than the ionic conductivity of said first phase, wherein substantially all of the metal M is in a second oxidation which is lower than said first oxidation state, and the ratio of lithium to metal is less than or equal to 1.05, characterized in that when it is incorporated into a cathode of a lithium battery, the lithium ion conductivity of said material is in the range of 10−6 S/cm to 5×10−4S/cm.
Dependencies are inferred from the claim text.