Lithium iron phosphate cathode material and method for producing same
AssigneeMitsui Engineering & Shipbuilding Co., Ltd.
InventorsYoshiki Sakaguchi, Yoshitaka Hamanaka
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Abstract
A lithium iron phosphate cathode material has high electron conductivity and high lithium ion conductivity, in other words, has excellent performance as an electrode material, which is provided by a carbon coating formed using a small amount of a carbon material. A method for producing the lithium iron phosphate cathode material is also provided. In particular, a lithium iron phosphate cathode material has primary particles of lithium iron phosphate coated with a conductive carbon cover layer. The conductive carbon cover layer is characterized by having thick layer portions with a thickness of 2 nm or greater and thin layer portions with a thickness of smaller than 2 nm.
Claims9
A lithium iron phosphate cathode material comprising:
- primary particles of lithium iron phosphate coated with a conductive carbon cover layer,
- wherein the conductive carbon cover layer has thick layer portions with a thickness of 2 nm or greater and thin layer portions with a thickness smaller than 2 nm.
A lithium iron phosphate cathode material comprising:
- primary particles of lithium iron phosphate coated with a conductive carbon cover layer, wherein
- the primary particles have carbon protrusions with a length of 5 nm to 100 nm on the conductive carbon cover layer.
The lithium iron phosphate cathode material according to claim further comprising:
- secondary particles, wherein
- each of the secondary particles is formed of at least two primary particles of lithium iron phosphate contacting each other via the carbon protrusions.
A method for producing a lithium iron phosphate cathode material comprising the steps of:
- mixing lithium iron phosphate particles with a carbon precursor which forms a conductive carbon cover layer when pyrolyzed to obtain a mixture;
- and
- calcining the mixture at a temperature and in an atmosphere where the carbon precursor undergoes pyrolysis, wherein
- the carbon precursor contains 20 to 99 wt % of an aromatic compound with a molecular weight of 160 or higher and has a viscosity of 500 to 1000 mPa·sec at 20° C.
A method for producing a lithium iron phosphate cathode material comprising the steps of:
- mixing lithium iron phosphate particles with a carbon precursor which forms a conductive carbon cover layer when pyrolyzed to obtain first and second mixtures;
- and
- calcining the second mixture at a temperature and in an atmosphere where the carbon precursor undergoes pyrolysis, wherein
- the carbon precursor contains 20 to 99 wt % of an aromatic compound with a molecular weight of 160 or higher and is dissolved in a solvent to prepare a solution having a viscosity of lower than 500 Pa·sec at 20° C. and the solution is mixed with the lithium iron phosphate particles to obtain the first mixture,
- the solvent contained in the first mixture is evaporated;
- p1 the first mixture after the evaporation of solvent is mixed with the carbon precursor, which has a viscosity of 500 to 1000 mPa·sec at 20° C., to obtain the second mixture;
Dependencies are inferred from the claim text.