Electrode-active anion-deficient lithium transition-metal phosphate, method for preparing the same, and electrochemical device using the same

Abstract

The invention provides an anion-deficient lithium transition-metal phosphate as an electrode-active material, which is represented by the chemical formula Li 1−x M(PO 4 ) 1−y (0≦x≦0.15, 0≦y≦0.05). The invention provides a method for preparing said Li 1−x M(PO 4 ) 1−y , which comprises preparing a precursor of lithium transition-metal phosphate; mixing said precursor with water under reaction conditions of 200˜700 and 180˜550 bar to produce an anion-deficient lithium transition-metal phosphate; and calcining, or granulating and calcining the resultant compound. The invention also provides electrochemical devices employing said Li 1−x M(PO 4 ) 1−y as an electrode-active material.

1 . An electrode-active anion-deficient lithium transition-metal phosphate of the following chemical formula 1
   Li 1−x M(PO 4 ) 1−y   (1)
   wherein 0≦x≦0.15, 0≦y≦0.05, and M is represented by the following chemical formula 2,
   M A   a M B   b M T   t Fe 1−(a+b+t)   (2)
 
   wherein M A  is at least one element selected from the group consisting of the Group 2 elements of the periodic table, M B  is at least one element selected from the group consisting of Group 13 elements of the periodic table, M T  is at least one element selected from the group consisting of Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, and Mo, and wherein 0≦a<1, 0≦b<0.575, 0≦t≦1, 0≦(a+b)<1, and 0<(a+b+t)≦1.   
     
     
         2 . An anion-deficient lithium transition-metal phosphate of  claim 1 , wherein 0.01≦y≦0.05. 
     
     
         3 . An anion-deficient lithium transition-metal phosphate of  claim 1 , wherein 0.02≦y≦0.05. 
     
     
         4 . An anion-deficient lithium transition-metal phosphate of  claim 1 , wherein 0.03≦y≦0.05. 
     
     
         5 . An anion-deficient lithium transition-metal phosphate of  claim 1 , wherein M A  is at least one element selected from the group consisting of Mg and Ca, M B  is at least one element selected from the group consisting of B, Al, and Ga, and M T  is at least one element selected from the group consisting of Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Zr, Nb, and Mo. 
     
     
         6 . An anion-deficient lithium transition-metal phosphate of  claim 1 , wherein M A  is Mg, M B  is Al, and M T  is selected from the group consisting of Mn, Co, and Ni. 
     
     
         7 . An anion-deficient lithium transition-metal phosphate of  claim 1 , wherein 0≦a≦0.30, and 0≦b≦0.20. 
     
     
         8 . An anion-deficient lithium transition-metal phosphate of  claim 1 , wherein 0≦a≦0.15, and 0≦b≦0.10. 
     
     
         9 . An anion-deficient lithium transition-metal phosphate of  claim 1 , characterized by having an olivine crystal structure. 
     
     
         10 . A cathode of a secondary battery, comprising an anion-deficient lithium transition-metal phosphate of any one of  claims 1  to  9 . 
     
     
         11 . A secondary battery comprising:
 (a) a cathode comprising an anion-deficient lithium transition-metal phosphate of any one of  claims 1  to  9 ;   (b) an anode;   (c) a separator; and   (d) an electrolyte   
     
     
         12 . A method for preparing an electrode-active anion-deficient lithium transition-metal phosphate of the following chemical formula 1:
   Li 1−x M(PO 4 ) 1−y   (1)
   wherein 0≦x≦0.15, 0<y≦0.05, and M is represented by the following chemical formula 2
   M A   a M B   b M T   t Fe 1−(a+b+t)   (2)
 
   wherein M A  is at least one element selected from the group consisting of the Group 2 elements of the periodic table, M B  is at least one element selected from the group consisting of Group 13 elements of the periodic table, M T  is at least one element selected from the group consisting of Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, and Mo, and wherein 0≦a<1, 0≦b<0.575, 0≦t≦1, 0≦(a+b)<1, and 0<(a+b+t)≦1,   said method comprising the following steps:
 (a) mixing a precursor of the metal M, a phosphate compound, an alkalinizing agent, and a lithium precursor to prepare a precursor of a lithium transition-metal phosphate; 
 (b) mixing the precursor of lithium transition-metal phosphate of step (a) with water under reaction conditions of a temperature of 200˜700, and a pressure of 180˜550 bar to produce an anion-deficient lithium transition-metal 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. 
   
     
     
         13 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein 0.01≦y≦0.05. 
     
     
         14 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein 0.02≦y≦0.05. 
     
     
         15 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein 0.03≦y≦0.05. 
     
     
         16 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein M A  is at least one element selected from the group consisting of Mg and Ca, M B  is at least one element selected from the group consisting of B, Al, and Ga, and M T  is at least one element selected from the group consisting of Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Zr, Nb, and Mo. 
     
     
         17 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein M A  is Mg, M B  is Al, and M T  is at least one element selected from the group consisting of Mn, Co, and Ni. 
     
     
         18 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein 0≦a≦0.30, and 0≦b≦0.20. 
     
     
         19 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein 0≦a≦0.15, and 0≦b≦0.10. 
     
     
         20 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate which is characterized by having an olivine crystal structure. 
     
     
         21 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein the pH of the reaction conditions in step (b) is greater than 4.0 and equal to or less than 12.0. 
     
     
         22 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, wherein the average size of the primary particles of anion-deficient lithium transition-metal phosphate prepared in step (b) is 0.01 μm to 5 μm. 
     
     
         23 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, characterized in adding at least one reducing agent selected from the group consisting of hydrazine, sodium phosphate, sodium sulfite, sodium nitrite, potassium iodide, sucrose, fructose, oxalic acid, ascorbic acid, hydrogen, carbon, and hydrocarbon, before, after, or during at least one of steps (a), (b), and (c). 
     
     
         24 . A method of  claim 12  for preparing an electrode-active anion-deficient lithium transition-metal phosphate, characterized in adding at least one carbon precursor selected from the group consisting of graphite, sucrose, fructose, oxalic acid, ascorbic acid, starch, cellulose, polyvinyl alcohol (PVA), and polyethylene glycol (PEG), before, after, or during at least one of steps (a), (b), and (c).