Electrode-active anion-deficient non-stoichiometric lithium iron-phosphate, method for preparing the same, and electrochemical device using the same
The invention provides an anion-deficient non-stoichiometric lithium iron phosphate as an electrode-active material, which is represented by the formula Li 1−x Fe(PO 4 ) 1−y , wherein 0<x≦0.15 and 0<y≦0.05. The invention provides a method for preparing said Li 1−x Fe(PO 4 ) 1−y , which comprises preparing a precursor of lithium iron phosphate; mixing said precursor with water under reaction conditions of 200˜700° C. and 180˜550 bar to produce lithium iron phosphate; and calcining, or granulating and calcining the resultant compound. The invention also provides electrochemical devices employing said Li 1−x Fe(PO 4 ) 1−y as an electrode-active material.
1. An electrode-active anion-deficient non-stoichiometric lithium iron phosphate of the formula Li 1−x Fe(PO 4 ) 1−y wherein 0.06≦x≦0.15 and 0.02≦y≦0.05.
2. The lithium iron phosphate of claim 1 , wherein 0.03≦y≦0.05.
3. A cathode of a secondary battery, comprising an electrode-active anion-deficient non-stoichiometric lithium iron phosphate of the formula Li 1−x Fe(PO 4 ) 1−y wherein 0.06≦x≦0.15 and 0.02≦y≦0.05.
4. The cathode of claim 3 , wherein 0.03≦y≦0.05.
5. A secondary battery comprising:
(a) a cathode comprising an electrode-active anion-deficient non-stoichiometric lithium iron phosphate of the formula Li 1−x Fe(PO 4 ) 1−y wherein 0.06≦x≦0.15 and 0.02≦y≦0.05;
(b) an anode;
(c) a separator; and
(d) an electrolyte.
6. The secondary battery of claim 5 , wherein 0.03≦y≦0.05.
7. A method for preparing an electrode-active anion-deficient non-stoichiometric lithium iron phosphate of the formula Li 1−x Fe(PO 4 ) 1−y , wherein 0<x≦0.15 and 0<y≦0.05, said method comprising the steps:
(a) mixing an iron precursor, a phosphate compound, an alkalinizing agent, and a lithium precursor to prepare a precursor of a lithium iron phosphate;
(b) mixing the precursor of lithium iron phosphate of step (a) with water under reaction conditions of a temperature of 200˜700° C., and a pressure of 180˜550 bar to produce an anion-deficient non-stoichiometric lithium iron phosphate, and drying the thus-obtained compound; and
(c) subjecting the resultant compound of step (b) either to calcination or to granulation and subsequent calcination.
8. The method of claim 7 , wherein 0.01≦y≦0.05.
9. The method of claim 7 , wherein 0.03≦y≦0.05.
10. The method of claim 7 , wherein the pH of the reaction conditions in step (b) is greater than 4 and equal to or less than 9.