Metal (II) phosphate powders, lithium metal phosphate powders for Li-ion battery, and methods for manufacturing the same

Abstract

Metal (II) phosphate powders, lithium metal phosphate powders for a Li-ion battery and methods for manufacturing the same are provided. The lithium metal phosphate powders are represented by the following formula (II):
LiFe.sub.1-aM.sub.aPO.sub.4(II)
wherein M comprises at least one metal selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<a1, the lithium metal phosphate powders are composed of plural flake powders, and a length of each of the flake powders is ranged from 50 nm to 10 m.

Claims

1. Lithium metal phosphate powders for a Li-ion battery, represented by the following formula (II):
LiFe.sub.1-aM.sub.aPO.sub.4(II) wherein M comprises at least one metal selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<a1, the lithium metal phosphate powders are composed of plural flake powders, and a length of each of the flake powders is ranged from 50 nm to 10 m.

2. The lithium metal phosphate powders of claim 1, wherein the flake powders are powders composed of independent flakes, flake powders that one end of each of the flake powders connects to each other, flake powders connecting to each other at the center of the flakes, or flake powders that one end of each of the flake powders connects to each other to form a connecting center.

3. The lithium metal phosphate powders of claim 1, wherein M comprises at least one metal selected from the group consisting of Mn, Co, Cu, Ni, Zn, and Mg.

4. The lithium metal phosphate powders of claim 1, wherein a thickness of each of the flake powders is ranged from 5 nm to 1 m.

5. The lithium metal phosphate powders of claim 1, wherein M is Mn, Co, Ni or Cu, and 0.6a1.

6. The lithium metal phosphate powders of claim 1, represented by the following formula (II-1):
LiFe.sub.1-a1-a2Mn.sub.a1M.sub.a2PO.sub.4(II-1) wherein M comprises at least one metal selected from the group consisting of Co, Cu, Ni, Zn, and Mg, 0.2a10.8, 0.05a20.4, and 0.5<a1+a21.

7. A method for manufacturing lithium metal phosphate powders, comprising the following steps: (a) providing metal (II) phosphate powders represented by the following formula (I):
(Fe.sub.1-xM.sub.x).sub.3(PO.sub.4).sub.2.yH.sub.2O(I) wherein M comprises at least one metal selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<x1, y is an integer of 0 to 8, the metal phosphate (II) powders are composed of plural flake powders, and a length of each of the flake powders is ranged from 50 nm to 10 m; (b) mixing the metal (II) phosphate powders with a Li-containing precursor to obtain mixed powders; and (c) heat-treating the mixed powders to obtain lithium metal phosphate powders represented by the following formula (II):
LiFe.sub.1-aM.sub.aPO.sub.4(II) wherein M comprises at least one metal selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<a1, the lithium metal phosphate powders are composed of plural flake powders, and a length of each of the flake powders is ranged from 50 nm to 10 m.

8. The method of claim 7, wherein the step (a) comprises the following steps: (a1) providing a P-containing precursor solution, wherein the P-containing precursor solution comprises: a P-containing precursor, and a weakly alkaline compound; and (a2) adding at least one metal (II) compound into the P-containing precursor solution to obtain the metal (II) phosphate powders represented by the formula (I).

9. The method of claim 8, wherein the P-containing precursor is at least one selected from the group consisting of H.sub.3PO.sub.4, NaH.sub.2PO.sub.4, Na.sub.2HPO.sub.4, Mg.sub.3(PO.sub.4).sub.2, and NH.sub.4H.sub.2PO.sub.4.

10. The method of claim 8, wherein the weakly alkaline compound is at least one selected from the group consisting of Na.sub.2CO.sub.3, and NaHCO.sub.3.

11. The method of claim 8, wherein the metal (II) compound is a sulfate, a carbonate, a nitrate, an oxalate, an acetate, a chlorite, a bromide, or an iodide of Fe, Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B or Nb.

12. The method of claim 7, wherein the Li-containing precursor is at least one selected from the group consisting of LiOH, Li.sub.2CO.sub.3, LiNO.sub.3, CH.sub.3COOLi, Li.sub.2C.sub.2O.sub.4, Li.sub.2SO.sub.4, LiCl, LiBr, LiI, LiH.sub.2PO.sub.4, Li.sub.2HPO.sub.4, and Li.sub.3PO.sub.4.

13. The method of claim 7, wherein the metal (II) phosphate powders are mixed with the Li-containing precursor and at least one carbon-containing material to obtain the mixed powders in the step (b).

14. The method of claim 13, wherein the carbon-containing material is sugar, stearic acid, citric acid, lauric acid, polystyrene, polystyrene ball (PS ball), graphene oxide, glucose, or vitamin C.

15. The method of claim 7, wherein the mixed powders is heat-treated under an atmosphere or vacuum or with an introduced gas flow to obtain the lithium metal phosphate powders, in the step (c).

16. The method of claim 15, wherein the atmosphere or the introduced gas flow comprises at least one selected from the group consisting of N.sub.2, H.sub.2, He, Ne, Ar, Kr, Xe, CO, methane, ArH.sub.2 mixed gas, and N.sub.2H.sub.2 mixed gas.

17. The method of claim 7, wherein the lithium metal phosphate powders are represented by the following formula (II-1):
LiFe.sub.1-a1-a2Mn.sub.a1M.sub.a2PO.sub.4(II-1) wherein M comprises at least one metal selected from the group consisting of Co, Cu, Ni, Zn, and Mg, 0.2a10.8, 0.05a20.4, and 0.5<a1+a21.

18. The method of claim 7, wherein the flake powders are powders composed of independent flakes, flake powders that one end of each of the flake powders connects to each other, flake powders connecting to each other at the center of the flakes, or flake powders that one end of each of the flake powders connects to each other to form a connecting center.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a SEM photo of Mn.sub.3(PO.sub.4).sub.2 prepared in Example 14 of the present invention.

(2) FIG. 2 is a SEM photo of Co.sub.3(PO.sub.4).sub.2 prepared in Example 16 of the present invention.

(3) FIG. 3 is a SEM photo of Cu.sub.3(PO.sub.4).sub.2 prepared in Example 17 of the present invention.

(4) FIG. 4 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Mg.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 3 of the present invention.

(5) FIG. 5 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Co.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 1 of the present invention.

(6) FIG. 6 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Zn.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 2 of the present invention.

(7) FIG. 7 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Ni.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 4 of the present invention.

(8) FIG. 8 is a SEM photo of (Mn.sub.0.6Fe.sub.0.2Ni.sub.0.2).sub.3(PO.sub.4).sub.2 prepared in Example 5 of the present invention.

(9) FIG. 9 is a SEM photo of (Mn.sub.0.55Fe.sub.0.3Ni.sub.0.15).sub.3(PO.sub.4).sub.2 prepared in Example 6 of the present invention.

(10) FIG. 10 is a SEM photo of (Fe.sub.0.4Mn.sub.0.2Ni.sub.0.2Mg.sub.0.2).sub.3(PO.sub.4).sub.2 prepared in Example 11 of the present invention.

(11) FIG. 11 is a SEM photo of LiMnPO.sub.4 prepared in Example 26 of the present invention.

(12) FIG. 12 is a SEM photo of LiMnPO.sub.4 prepared in Example 27 of the present invention.

(13) FIG. 13 is a SEM photo of LiCoPO.sub.4 prepared in Example 28 of the present invention.

(14) FIG. 14 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 18 of the present invention.

(15) FIG. 15 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 19 of the present invention.

(16) FIG. 16 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 20 of the present invention.

(17) FIG. 17 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 21 of the present invention.

(18) FIG. 18 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 22 of the present invention.

(19) FIG. 19 is a SEM photo of LiFe.sub.0.4Mn.sub.0.55Ni.sub.0.05PO.sub.4 prepared in Example 23 of the present invention.

(20) FIG. 20 is a TEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 20 of the present invention.

(21) FIG. 21 is a perspective view showing a Li-ion battery according to the present invention.

(22) FIG. 22 shows the relation between the voltage and the specific capacities of a Li-ion battery prepared with lithium metal phosphate powders according to Example 19 of the present invention.

(23) FIG. 23 shows the relation between the voltage and the specific capacities of a Li-ion battery prepared with lithium metal phosphate powders according to Example 19 of the present invention.

(24) FIG. 24 shows the relation between the voltage and the specific capacities of a Li-ion battery prepared with lithium metal phosphate powders according to Example 20 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(25) The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

(26) Analysis

(27) The shapes of the metal (II) phosphate powders and the lithium metal phosphate powders obtained in the following examples (Ex) were observed with a scanning electron microscope (SEM) (Hitachi S-4000).

(28) In addition, the metal (II) phosphate powders and the lithium metal phosphate powders obtained in the following examples were also examined with an X-ray diffractometer (Shimadzu 6000) to understand the crystal structure thereof. The X-ray diffraction pattern was collected by Cu K radiation, the 2-scanning angle is 15-45, and the scanning rate is 1/min. The standards for X-ray examination are listed in the following Table 1.

(29) TABLE-US-00001 TABLE 1 Compound Standard Mn.sub.3(PO.sub.4).sub.23H.sub.2O JCPDS No. 3-426 Mn.sub.3(PO.sub.4).sub.27H.sub.2O JCPDS No. 84-1160 Ni.sub.3(PO.sub.4).sub.28H.sub.2O JCPDS No. 46-1388 or JCPDS No. 1-126 Co.sub.3(PO.sub.4).sub.28H.sub.2O JCPDS No. 33-432 Cu.sub.3(PO.sub.4).sub.23H.sub.2O JCPDS No. 22-548 Fe.sub.3(PO.sub.4).sub.28H.sub.2O JCPDS No. 79-1928 LiMnPO.sub.4 JCPDS No. 33-804 LiCoPO.sub.4 JCPDS No. 85-2 LiFePO.sub.4 JCPDS No. 81-1173
Preparation of Metal (II) Phosphate Powders
Step I

(30) H.sub.3PO.sub.4 and NaHCO.sub.3 were added into 500 ml of de-ionized water in a molar ratio of 1:3 to obtain a P-containing precursor solution, and the P-containing precursor solution was stirred for 30 min.

(31) Step II

(32) To prepare Mn.sub.3(PO.sub.4).sub.2, MnSO.sub.4.5H.sub.2O was added into the obtained P-containing precursor solution, wherein a molar ratio of MnSO.sub.4.5H.sub.2O to H.sub.3PO.sub.4 was 3:2.

(33) To prepare (Fe.sub.1-xMn.sub.x).sub.3(PO.sub.4).sub.2, MnSO.sub.4.5H.sub.2O and FeSO.sub.4.7H.sub.2O were added into the obtained P-containing precursor solution, wherein a molar ratio of a total amount of MnSO.sub.4.5H.sub.2O and FeSO.sub.4.7H.sub.2O to H.sub.3PO.sub.4 was 3:2, and a molar ratio of MnSO.sub.4.5H.sub.2O to FeSO.sub.4.7H.sub.2O was adjusted on the basis of the desired (Fe.sub.1-xMn.sub.x).sub.3(PO.sub.4).sub.2 shown in the following Table 2.

(34) To prepare Fe.sub.3(PO.sub.4).sub.2, FeSO.sub.4.7H.sub.2O was added into the obtained P-containing precursor solution, wherein a molar ratio of FeSO.sub.4.7H.sub.2O to H.sub.3PO.sub.4 was 3:2.

(35) To prepare metal (II) phosphate powders containing two or more metals selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, two or more suitable metal (II) sulfates were used, wherein a molar ratio of a total amount of the used metal (II) sulfates to H.sub.3PO.sub.4 was 3:2, and a molar ratio between the used metal (II) sulfates are adjusted on the basis of the desired metal (II) phosphate powders shown in the following Table 2.

(36) Step III

(37) The obtained products in Step II were washed with de-ionized water and then collected with centrifugation for three times.

(38) Step IV

(39) The collected products in Step III were dried at 55 C. for 12 to 108 hr, and metal (II) phosphate powders shown in the following Table 2 were obtained.

(40) The shapes of the metal (II) phosphate powders were observed by SEM, and the obtained were also examined with an X-ray diffractometer. The results are listed in the following Table 2.

(41) TABLE-US-00002 TABLE 2 Ex Compound Color Shape XRD summary 1 (Mn.sub.0.8Fe.sub.0.1Co.sub.0.1).sub.3(PO.sub.4).sub.2 Light Thickness: 10~15 nm Peaks similar to brown Length: 50~900 nm Mn.sub.3(PO.sub.4).sub.23H.sub.2O, Irregular independent but right-shifting flakes 2 (Mn.sub.0.8Fe.sub.0.1Zn.sub.0.1).sub.3(PO.sub.4).sub.2 Milky Thickness: 20~80 nm Peaks similar to yellow Plates with flakes Mn.sub.3(PO.sub.4).sub.23H.sub.2O, attached on their but right-shifting surface Length (plates): 1~3 m Length (flakes): 60~150 nm Irregular plates and gathered flakes 3 (Mn.sub.0.8Fe.sub.0.1Mg.sub.0.1).sub.3(PO.sub.4).sub.2 Milky Thickness: 10~15 nm Peaks similar to yellow Length: 300~900 nm Mn.sub.3(PO.sub.4).sub.23H.sub.2O, Irregular independent but right-shifting flakes 4 (Mn.sub.0.8Fe.sub.0.1Ni.sub.0.1).sub.3(PO.sub.4).sub.2 Milky Thickness: 10~15 nm Peaks similar to yellow Length: 200~800 nm Mn.sub.3(PO.sub.4).sub.23H.sub.2O, Irregular independent but right-shifting flakes 5 (Mn.sub.0.6Fe.sub.0.2Ni.sub.0.2).sub.3(PO.sub.4).sub.2 Chartreuse Thickness: 60~100 nm Peaks similar to Length: 1~3 m Fe.sub.3(PO.sub.4).sub.28H.sub.2O Plates 6 (Mn.sub.0.55Fe.sub.0.3Ni.sub.0.15).sub.3(PO.sub.4).sub.2 Cyan Thickenss: 20~100 nm Peaks similar to Length: 1~3 m Fe.sub.3(PO.sub.4).sub.28H.sub.2O Plates 7 (Mn.sub.0.6Fe.sub.0.3Ni.sub.0.10).sub.3(PO.sub.4).sub.2 Cyan Thickenss: 80~130 nm Peaks similar to Length: 1~3 m Fe.sub.3(PO.sub.4).sub.28H.sub.2O Plates 8 (Mn.sub.0.55Fe.sub.0.4Ni.sub.0.05).sub.3(PO.sub.4).sub.2 Camel Thickness: 50~140 nm Peaks similar to green Length: 1~3 m Fe.sub.3(PO.sub.4).sub.28H.sub.2O Plates 9 (Mn.sub.0.575Fe.sub.0.4Ni.sub.0.025).sub.3(PO.sub.4).sub.2 Yellow tan Thickness: 10~15 nm Peaks similar to Length: 300 nm~1 m Fe.sub.3(PO.sub.4).sub.28H.sub.2O, Irregular independent but poor flakes crystallinity 10 (Fe.sub.0.4Mn.sub.0.2Ni.sub.0.2Mg.sub.0.2).sub.3(PO.sub.4).sub.2 Blue Thickness: 10 nm Peaks similar to Length: 50~300 nm Fe.sub.3(PO.sub.4).sub.28H.sub.2O, Cloudy flakes but right-shifting 11 (Fe.sub.0.4Mn.sub.0.2Ni.sub.0.2Mg.sub.0.2).sub.3(PO.sub.4).sub.2 Blue Thickness: 50~100 nm Peaks similar to Plates with flakes Fe.sub.3(PO.sub.4).sub.28H.sub.2O, attached on their but right-shifting surface Length (plates): 1~2 m Length (flakes): 50~200 nm Irregular plates and flakes 12 (Mn.sub.0.6Fe.sub.0.4).sub.3(PO.sub.4).sub.2 Khaki Thickness: 10~15 nm Most peaks are Length: 300~900 nm consistent to Irregular flakes peaks of Mn.sub.3(PO.sub.4).sub.77H.sub.2O and Fe.sub.3(PO.sub.4).sub.28H.sub.2O, and 3 peaks cannot be identified. 13 (Mn.sub.0.9Fe.sub.0.1).sub.3(PO.sub.4).sub.2 Light Thickness: 10 nm Major peaks are yellow Length: 100~600 nm consistent to the Irregular independent peaks of flakes Mn.sub.3(PO.sub.4).sub.23H.sub.2O, but some peaks are consistent to the peaks of Mn.sub.3(PO.sub.4).sub.27H.sub.2O. 14 Mn.sub.3(PO.sub.4).sub.2 Light pink Thicknesss: 10~15 nm Major peaks are Length: 300~900 nm consistent to the Irregular independent peaks of flakes Mn.sub.3(PO.sub.4).sub.23H.sub.2O, but some peaks are consistent to the peaks of Mn.sub.3(PO.sub.4).sub.27H.sub.2O after drying for 108 hr. 15 Ni.sub.3(PO.sub.4).sub.2 Apple Thickness: 10 nm Peaks similar to green Length: 100~300 nm Ni.sub.3(PO.sub.4).sub.28H.sub.2O Circular flakes 16 Co.sub.3(PO.sub.4).sub.2 Pink The thickness is Peaks similar to purple varied according to Co.sub.3(PO.sub.4).sub.28H.sub.2O, the reaction time. but right-shifting Thickness: 15 min: 90~700 nm 60 s: 20~300 nm 45 s: 10~40 nm Length: 15 min: 3~10 m 60 s: 400 nm~1 m 45 s: 400 nm~1 m One end of each of the flake powders connects to each other to form a connecting center. 17 Cu.sub.3(PO.sub.4).sub.2 Baby blue Thickness: 10~15 nm Peaks similar to Length: 200~500 nm Cu.sub.3(PO.sub.4).sub.23H.sub.2O Flakes formed into a 3D net shape

(42) FIG. 1 is a SEM photo of Mn.sub.3(PO.sub.4).sub.2 prepared in Example 14 of the present invention. FIG. 2 is a SEM photo of Co.sub.3(PO.sub.4).sub.2 prepared in Example 16 of the present invention. FIG. 3 is a SEM photo of Cu.sub.3(PO.sub.4).sub.2 prepared in Example 17 of the present invention. FIG. 4 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Mg.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 3 of the present invention. FIG. 5 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Co.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 1 of the present invention. FIG. 6 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Zn.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 2 of the present invention. FIG. 7 is a SEM photo of (Mn.sub.0.8Fe.sub.0.1Ni.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 4 of the present invention. FIG. 8 is a SEM photo of (Mn.sub.0.6Fe.sub.uNi.sub.0.2).sub.3(PO.sub.4).sub.2 prepared in Example 5 of the present invention. FIG. 9 is a SEM photo of (Mn.sub.0.55Fe.sub.0.3Ni.sub.0.1).sub.3(PO.sub.4).sub.2 prepared in Example 6 of the present invention. FIG. 10 is a SEM photo of (Fe.sub.0.4Mn.sub.0.2Ni.sub.0.2Mg.sub.0.2).sub.3(PO.sub.4).sub.2 prepared in Example 11 of the present invention. From FIG. 1 to FIG. 10, it can be found that most of the observed metal (II) phosphates have flake shapes with thin thicknesses and long lengths.

(43) In addition, the rate for adding MnSO.sub.4.5H.sub.2O into the P-containing precursor solution relates to the formation of Mn.sub.3(PO.sub.4).sub.2.3H.sub.2O and Mn.sub.3(PO.sub.4).sub.2.7H.sub.2O. When MnSO.sub.4.5H.sub.2O is added rapidly, more Mn.sub.3(PO.sub.4).sub.2.3H.sub.2O is obtained. When MnSO.sub.4.5H.sub.2O is added slowly, more Mn.sub.3(PO.sub.4).sub.2.7H.sub.2O is obtained. Furthermore, even though the collected products in Step III were dried at 55 C. for 12 to 108 hr, the water molecules in Mn.sub.3(PO.sub.4).sub.2.7H.sub.2O cannot be removed completely. Thus, for preparing lithium metal phosphate powders, the thermal gravimetric analysis (TGA) is held to calculate the content of the water molecular in the manganese (II) phosphate.

(44) Similarly, for other metal (II) phosphate with different crystals containing different amount of water molecules, TGA is also held to calculate the content of the water molecular in the metal (II) phosphate.

(45) Furthermore, the rate for adding metal (II) sulfates into the P-containing precursor solution is also related to the thickness of the obtained metal (II) phosphate.

(46) Preparation of Lithium Metal Phosphate Powders

(47) Step A: Ball Milling Process

(48) A-1: Preparation by One Metal (II) Phosphate Powder and Li.sub.3PO.sub.4

(49) One metal (II) phosphate powder was used as a precursor, and mixed with Li.sub.3PO.sub.4 in a molar ratio of 1:1. In addition, 15 wt % of sugar or 6.5 wt % of polystyrene was also added in the mixture. The mixture was mixed with a 3D shaker containing 0.8 mm zirconia balls for 2 hr to obtain mixed powders.

(50) A-2: Preparation by Two or More Metal (II) Phosphate Powder and Li.sub.3PO.sub.4

(51) Two or more metal (II) phosphate powders was used as precursors, and mixed with Li.sub.3PO.sub.4, wherein a molar ratio of a total amount of the metal (II) phosphate powders to Li.sub.3PO.sub.4 was 1:1. In addition, 15 wt % of sugar or 6.5 wt % of polystyrene (PS) was also added in the mixture. The mixture was mixed with a 3D shaker containing 0.8 mm zirconia balls for 2 hr to obtain mixed powders.

(52) In one example, 1 wt % of graphene oxide was also added as a carbon source into the mixture.

(53) Step B: Heat Treating Process

(54) The product obtained in Step A was thermal-annealed at 750 C., under a N.sub.2 gas flow (1 atm) for 3 hr. Finally, lithium metal phosphate powders coated with carbon and formed in flake shapes were obtained.

(55) Alternatively, a vacuum is created in the heat-treating tube, followed by introducing N.sub.2 gas into the heat-treating tube, and then the heat-treating tube is sealed. The product obtained in Step A was thermal-annealed at 750 C. in the sealed heat-treating tube under N.sub.2 atmosphere for 3 hr. The pressure was kept under 1 atm during the heat-treating process. Finally, lithium metal phosphate powders coated with carbon and formed in flake shapes were obtained.

(56) The shapes of the obtained lithium metal phosphate powders were observed by SEM, and the obtained were also examined with an X-ray diffractometer. The results are listed in the following Table 3.

(57) TABLE-US-00003 TABLE 3 Step Carbon XRD Ex Compound Precursor A source Shape Summary 18 LiFe.sub.0.4Mn.sub.0.6PO.sub.4 Mn.sub.3(PO.sub.4).sub.2 A-2 Sugar Thickness: Peaks Fe.sub.3(PO.sub.4).sub.2 10~15 nm consistent to Length: LiFePO.sub.4 when 300~900 nm 2 < 35 Irregular Peaks locating independent between flakes LiFePO.sub.4 and LiMnPO.sub.4 when 2 > 35 19 LiFe.sub.0.4Mn.sub.0.6PO.sub.4 Mn.sub.3(PO.sub.4).sub.2 A-2 PS Thickness: Peaks Fe.sub.3(PO.sub.4).sub.2 10~15 nm consistent to Length: LiFePO.sub.4 when 300~900 nm 2 < 35 Irregular Peaks locating independent between flakes (95%) LiFePO.sub.4 and and bulk LiMnPO.sub.4 powders (5%) when 2 > 35 20 LiFe.sub.0.4Mn.sub.0.6PO.sub.4 Mn.sub.3(PO.sub.4).sub.2 A-2 Sugar Thickness: Peaks Fe.sub.3(PO.sub.4).sub.2 Graphene 10~15 nm consistent to oxide Length: LiFePO.sub.4 when 300~900 nm 2 < 35 Irregular Peaks locating independent between flakes (more LiFePO.sub.4 and gathered) LiMnPO.sub.4 when 2 > 35 21 LiFe.sub.0.4Mn.sub.0.6PO.sub.4 (Mn.sub.0.6Fe.sub.0.4).sub.3 A-1 Sugar Thickness: Most peaks (PO.sub.4).sub.2 10 nm consistent with Length: LiFePO.sub.4, and 300~900 nm some peaks (70%) shifted 70~150 nm (30%) Flakes with rounding edges 22 LiFe.sub.0.4Mn.sub.0.6PO.sub.4 (Mn.sub.0.6Fe.sub.0.4).sub.3 A-1 PS Thickness: Most peaks (PO.sub.4).sub.2 10 nm consistent with Circular flakes, LiFePO.sub.4, and Length: some peaks 300~700 nm shifted (50%) Irregular flakes, Length: 300~700 nm (25%) Irregular broken flakes, Length: <100 nm (10%) Big circular flakes, Length: around 2.5 m (15%) 23 LiFe.sub.0.4Mn.sub.0.55 (Mn.sub.0.55Fe.sub.0.4 A-1 Sugar Thickness: Peaks Ni.sub.0.05PO.sub.4 Ni.sub.0.05).sub.3(PO.sub.4).sub.2 20 nm consistent to Circular flakes, LiFePO.sub.4 Length: 250~900 nm Irregular flakes with rounding edges, Length: 60~500 nm 24 LiFe.sub.0.2Mn.sub.0.8PO.sub.4 Mn.sub.3(PO.sub.4).sub.2 A-2 Sugar Thickness: Peaks Fe.sub.3(PO.sub.4).sub.2 10~15 nm consistent to Length: LiFePO.sub.4 when 300~900 nm 2 < 21 Independent Peaks locating flakes between LiFePO.sub.4 and LiMnPO.sub.4 when 2 > 21 25 LiFe.sub.0.4Mn.sub.0.55 Mn.sub.3(PO.sub.4).sub.2 A-2 Sugar Thickness: Peaks Co.sub.0.05PO.sub.4 Fe.sub.3(PO.sub.4).sub.2 10~15 nm consistent to Co.sub.3(PO.sub.4).sub.2 Length: LiFePO.sub.4 when 300~900 nm 2 < 35 Independent Peaks locating flakes between LiFePO.sub.4 and LiMnPO.sub.4 when 2 > 35 26 LiMnPO.sub.4 Mn.sub.3(PO.sub.4).sub.2 A-1 Sugar Thickness: Peaks 10 nm consistent to Length: LiMnPO.sub.4 300~900 nm Independent flakes 27 LiMnPO.sub.4 Mn.sub.3(PO.sub.4).sub.2 A-1 PS Thickness: Peaks 10 nm consistent to Length: LiMnPO.sub.4 500 nm~2 m Independent flakes 28 LiCoPO.sub.4 Co.sub.3(PO.sub.4).sub.2 A-1 Sugar Thickness: Peaks 10~20 nm consistent to Length: LiCoPO.sub.4 300 nm~1.5 m Independent flakes 29 LiMn.sub.0.6Co.sub.0.4PO.sub.4 Mn.sub.3(PO.sub.4).sub.2 A-2 Sugar Thickness: Peaks Co.sub.3(PO.sub.4).sub.2 10~20 nm consistent to Length: LiCoPO.sub.4 when 300~900 nm 2 < 27 Flakes with Peaks locating rounding edges between LiCoPO.sub.4 and LiMnPO.sub.4 when 2 > 27

(58) FIG. 11 is a SEM photo of LiMnPO.sub.4 prepared in Example 26 of the present invention. FIG. 12 is a SEM photo of LiMnPO.sub.4 prepared in Example 27 of the present invention. FIG. 13 is a SEM photo of LiCoPO.sub.4 prepared in Example 28 of the present invention. FIG. 14 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 18 of the present invention. FIG. 15 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 19 of the present invention. FIG. 16 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 20 of the present invention. FIG. 17 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 21 of the present invention. FIG. 18 is a SEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 22 of the present invention. FIG. 19 is a SEM photo of LiFe.sub.0.4Mn.sub.0.55Ni.sub.0.05PO.sub.4 prepared in Example 23 of the present invention. From FIG. 11 to FIG. 19, it can be found that the observed lithium metal phosphates have flake shapes with thin thicknesses and long lengths.

(59) FIG. 20 is a TEM photo of LiFe.sub.0.4Mn.sub.0.6PO.sub.4 prepared in Example 20 of the present invention. From the result shown in FIG. 20, it can be found reduced graphene oxide is present between flakes, and the flakes are coated with a uniform carbon film.

(60) According to the results of Examples 1 to 17, the meal (II) phosphate powders have small and uniform grain size. When these metal (II) phosphate powders are used as a precursor for preparing lithium ion phosphate powders, the time for the heat-treating process can be shortened. Hence, the cost for manufacturing the Li-ion batteries can be further reduced. In addition, the thermal-annealed lithium metal phosphate powders have similar shape to that of metal (II) phosphate powders, so the thermal-annealed lithium metal phosphate powders also have small and uniform grain size. Hence, the grinding process and the sieving process can be omitted during the process for preparing the cathode materials, so the cost of Li-ion batteries can be reduced. Furthermore, according to the results of Examples 18 to 29, the lithium metal phosphate powders of the present invention have nano, micro, or sub-micro grain size. When the lithium metal phosphate powders of the present invention are used as cathode materials of Li-ion batteries, the Li-ion batteries can exhibit uniform charging and discharging current, and excellent charge/discharge efficiency. Hence, not only the cost of the Li-ion batteries can be reduced, but also the charge/discharge time can be shortened and the capacity of the batteries can be further improved.

(61) Preparation and Testing of Li-Ion Batteries

(62) The Li-ion battery of the present invention was prepared through the conventional manufacturing method thereof. Briefly, PVDF, lithium metal phosphate powders of Examples 19 and 20, ZrO, KS-6 [TIMCAL] and Super-P [TIMCAL] were dried in a vacuum oven for 24 hr, and a weight ratio of lithium metal phosphate powders:PVDF:KS-6: Super-P was 85:10:3:2. Next, the aforementioned materials were mixed with a 3D miller containing NMP to obtain slurry. An Al foil was provided and coated with the slurry through a blade coating process, and then placed in a vacuum oven at 90 C. for 12 hr. The dried foil coated with the slurry was pressed by a roller, and cut into 13 mm circular plates.

(63) Next, as shown in FIG. 21, an upper cap 17, a lower cap 11, a wide mouth plate 16, a pad 15, the aforementioned circular plate 12 with the slurry coated on a surface 121 thereof, and a 18 mm separator 13 are placed in a vacuum oven at 90 C. for 24 hr, and then placed into a glove box with less than 1 ppm of water and O.sub.2 under Ar environment. After immersing the circular plate 12, and the separator 13 with electrolyte, the circular plate 12, the separator 13, a Li-plate 14, the pad 15, the wide mouth plate 16 and the upper cap 17 were sequentially laminated on the lower cap 11, as shown in FIG. 20. After pressing and sealing, a CR2032 coin type Li-ion battery was obtained, and tested after 12-30 hr. The electrolyte used was 1M LiPF.sub.6 in EC/EMC/DMC (1:1:1 wt %)+1% VC, a commonly used electrolyte for LiFePO.sub.4 battery.

(64) The obtained Li-ion batteries prepared by lithium metal phosphate powders of Examples 19 and 20 were tested with automatic cell charge-discharge test system (AcuTech Systems BAT-750B). FIG. 22 show the relations between the voltage and the specific capacities of a Li-ion battery prepared with lithium metal phosphate powders according to Example 19 of the present invention, wherein the lithium metal phosphate powders is prepared by a heat treatment process under sealed N.sub.2 atmosphere. FIG. 23 show the relations between the voltage and the specific capacities of a Li-ion battery prepared with lithium metal phosphate powders according to Example 19 of the present invention, wherein the lithium metal phosphate powders is prepared by a heat treatment process under a N.sub.2 gas flow. FIG. 24 show the relations between the voltage and the specific capacities of a Li-ion battery prepared with lithium metal phosphate powders according to Example 20 of the present invention, wherein the lithium metal phosphate powders is prepared by a heat treatment process under a N.sub.2 gas flow.

(65) FIG. 22 to FIG. 24 show the relations between the voltage and the specific capacities of a Li-ion battery prepared with lithium metal phosphate powders according to Examples 19 and 20 of the present invention, which was tested by the same charge and discharge current (0.1 C, 0.2 C, 0.5 C, 0.75 C and 1 C) at 30-40 cycles. From the results shown in FIG. 22 and FIG. 23, it can be found that the specific capacities of the batteries thereof under 0.1 C discharge current was about 152 mAh/g, and was less than that of the batteries prepared with lithium metal phosphate powders of example 20 which is above 160 mAh/g as shown in FIG. 24. An average discharging voltage of about 3.6 V was obtained for batteries prepared with lithium metal phosphate powders of example 19 which was higher than the values 3.2-3.4 V of the batteries prepared with LiFePO.sub.4. These results indicate the energy density of the Li-ion battery prepared with lithium metal phosphate powders according to Example 19 would be higher than that of the LiFePO.sub.4 battery, although a commonly used low voltage electrolyte for LiFePO.sub.4 battery was applied.

(66) In conclusion, the metal (II) phosphate powders of the present invention have thin thickness, and high length to thickness ratio. Hence, the time for preparing lithium metal phosphate powders can be greatly reduced. In addition, when the obtained lithium metal phosphate powders are further applied to prepare Li-ion batteries, the performance of the batteries can be greatly improved.

(67) Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.