LiFePO4 precursor for manufacturing electrode material of Li-ion battery and method for manufacturing the same

Abstract

An LiFePO.sub.4 precursor for manufacturing an electrode material of an Li-ion battery and a method for manufacturing the same are disclosed. The LiFePO.sub.4 precursor of the present disclosure can be represented by the following formula (I):
LiFe.sub.(1-a)M.sub.aPO.sub.4  (I)
wherein M and a are defined in the specification, the LiFePO.sub.4 precursor does not have an olivine structure, and the LiFePO.sub.4 precursor is powders constituted by plural flakes.

Claims

1. An LiFePO.sub.4 precursor for manufacturing an electrode material of an Li-ion battery, represented by the following formula (I):
LiFe.sub.(1-a)M.sub.aPO.sub.4  (I) wherein M comprises at least one metal selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B, and Nb, 0≤a<0.5, the LiFePO.sub.4 precursor does not have an olivine structure, and the LiFePO.sub.4 precursor is powders constituted by plural flakes; wherein the LiFePO4 precursor comprises an amorphous zone and a crystallized zone.

2. The LiFePO.sub.4 precursor of claim 1, wherein a content of the amorphous zone is greater than a content of the crystallized zone.

3. The LiFePO.sub.4 precursor of claim 1, wherein the crystallized zone comprises at least two selected from the group consisting of C.sub.2H.sub.4Li.sub.4O.sub.7P.sub.2.Math.H.sub.2O, Fe.sub.3H.sub.9(PO.sub.4).sub.6.Math.6H.sub.2O, Fe.sub.2Fe(P.sub.2O.sub.7).sub.2, FeLiO.sub.2, Li.sub.2Fe.sub.2O.sub.4, FePO.sub.4, C.sub.6H.sub.6FeO.sub.8.Math.2H.sub.2O, FePO.sub.4(H.sub.2O).sub.2, Li.sub.2O.sub.2, Li, and Fe.sub.2O(PO.sub.4).

4. The LiFePO.sub.4 precursor of claim 3, wherein the crystallized zone further comprises at least one selected from the group consisting of Fe.sub.3O.sub.4, Fe.sub.3PO.sub.7, Fe.sub.3Fe.sub.4(PO.sub.4).sub.6 and C.sub.2HLiO.sub.4.Math.H.sub.2O.

5. The LiFePO.sub.4 precursor of claim 1, which shows an X-ray diffraction pattern having characteristic peaks at near 2θ angles of 19.37°, 21.47°, 24.11°, 25.95°, 32.35°, 35°, 36.46°, and 43.83°.

6. The LiFePO.sub.4 precursor of claim 5, which shows the X-ray diffraction pattern having further characteristic peaks at near 2θ angles of 18.3°, 28.91° and 30.05°.

7. The LiFePO.sub.4 precursor of claim 1, wherein the powders has a diameter ranged from 800 nm to 5 μm, a length of each of the plural flakes is respectively ranged from 400 nm to 5000 nm, and a thickness of each of the plural flakes is respectively ranged from 1 nm to 50 nm.

8. The LiFePO.sub.4 precursor of claim 7, wherein the plural flakes are gathered to from a flower-like shape or laminated to form a shale-like shape.

9. The LiFePO.sub.4 precursor of 1, wherein the powders are further coated with a carbon layer.

10. A method for manufacturing an LiFePO.sub.4 precursor for manufacturing an electrode material of an Li-ion battery, comprising the following steps: providing a mixed organic solution, which comprises Li, Fe, and P, wherein the Li contained in the mixed organic solution is derived from a Li-containing precursor or a P and Li-containing precursor, the Fe contained in the mixed organic solution is derived from an Fe-containing precursor or a P and Fe-containing precursor, and the P contained in the mixed organic solution is derived from a P-containing precursor, a P and Li-containing precursor, or a P and Fe-containing precursor; and heating the mixed organic solution under reflux to a predetermined temperature and maintaining the predetermined temperature for a predetermined period to obtain an LiFePO.sub.4 precursor, wherein the LiFePO.sub.4 precursor is represented by the following formula (I):
LiFe.sub.(1-a)M.sub.aPO.sub.4  (I) wherein M comprises at least one metal selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B, and Nb, 0≤a<0.5, the LiFePO.sub.4 precursor does not have an olivine structure, and the LiFePO.sub.4 precursor is powders constituted by plural flakes, wherein the LiFePO.sub.4 precursor comprises an amorphous zone and a crystallized zone.

11. The method of claim 10, further comprising a step of coating the LiFePO.sub.4 precursor with a carbon source through a milling process to form a carbon layer on the powders.

12. The method of claim 11, wherein the mixed organic solution is heated under an atmosphere or with an introduced gas flow.

13. The method of claim 12, wherein the atmosphere or the introduced gas flow comprises one selected from the group consisting of N.sub.2, He, Ne, Ar, Kr, Xe, CO, methane, N.sub.2—H.sub.2 mixed gas, and a mixture thereof.

14. The method of claim 10, 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, and LiI; the Fe-containing precursor is at least one selected from the group consisting of FeCl.sub.2, FeBr.sub.2, FeI.sub.2, FeSO.sub.4, (NH.sub.4).sub.2Fe(SO.sub.4).sub.2, Fe(NO.sub.3).sub.2, FeC.sub.2O.sub.4, (CH.sub.3COO).sub.2Fe, and FeCO.sub.3; 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; the P and Li-containing precursor is at least one selected from the group consisting of LiH.sub.2PO.sub.4, Li.sub.2HPO.sub.4, and Li.sub.3PO.sub.4; and the P and Fe-containing precursor is at least one selected from the group consisting of Fe.sub.3(PO.sub.4).sub.2, and FePO.sub.4.

15. The method of claim 10, wherein the mixed organic solution is heated under atmospheric pressure.

16. The method of claim 10, wherein an organic solvent in the mixed organic solution is at least one selected from the group consisting of ethylene glycol (EG), diethylene glycol (DEG), glycerol, triethylene glycol (TEG), tetraethylene glycol (TTEG), polyethylene glycol (PEG), Dimethyl sulfoxide (DMSO), and N,N-dimethylmethanamide (DMF).

17. The method of claim 10, wherein the predetermined temperature is ranged from 105° C. to 350° C., and the predetermined period is ranged from 2 hrs to 20 hrs.

18. The method of claim 10, wherein the LiFePO.sub.4 precursor shows an X-ray diffraction pattern having characteristic peaks at near 2θ angles of 19.370, 21.47°, 24.110, 25.95°, 32.350, 350, 36.46°, and 43.83°.

19. The method of claim 18, wherein the LiFePO.sub.4 precursor shows the X-ray diffraction pattern having further characteristic peaks at near 2θ angles of 18.3°, 28.91° and 30.05°.

20. The method of claim 10, wherein the mixed organic solution further comprises a dispersant.

21. The method of claim 20, wherein the dispersant is at least one selected from the group consisting of potassium dodecyl sulfate, ammonium dodecyl sulfate, calcium dodecyl sulfate, sodium dodecyl sulfate, copper dodecyl sulfate, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl Sulfate, sodium dodecyl benzene sulfonate, magnesium dodecyl benzene sulfonate, sodium dodecyl sulfonate, magnesium dodecyl sulfonate, sodium decyl sulfonate, and sodium decyl sulfate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an XRD pattern of an LiFePO.sub.4 precursor according to Example 1 of the present disclosure.

(2) FIG. 2A to FIG. 2C shows TEM photos of one region of an LiFePO.sub.4 precursor according to Example 1 of the present disclosure.

(3) FIG. 3 is a TEM photo of another region of an LiFePO.sub.4 precursor according to Example 1 of the present disclosure.

(4) FIG. 4 is a TEM photo of further another region of an LiFePO.sub.4 precursor according to Example 1 of the present disclosure.

(5) FIG. 5A to FIG. 5F are SEM photos of an LiFePO.sub.4 precursor according to Example 1 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENT

(6) The following embodiments when read with the accompanying drawings are made to clearly exhibit the above-mentioned and other technical contents, features and/or effects of the present disclosure.

(7) Through the exposition by means of the specific embodiments, people would further understand the technical means and effects the present disclosure adopts to achieve the above-indicated objectives. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present disclosure should be encompassed by the appended claims.

(8) Furthermore, when a value is in a range from a first value to a second value, the value can be the first value, the second value, or another value between the first value and the second value.

(9) Example 1 to Example 29

(10) The LiFePO.sub.4 precursors of Example (Ex as the abbreviation in the following Table 1) 1 to Example 29 are synthesized according to the following Table 1. In the following Table 1, the addition amounts and molar ratios of H.sub.3PO.sub.4, FeC.sub.2O.sub.4.Math.2H.sub.2O, and LiOH.Math.H.sub.2O, ambient temperature (Temp 1), relative humidity (RH), time for increasing to 220° C. (T1), reaction time (T2), final temperature after the reaction is stopped (Temp 2), and N.sub.2 gas flow (N.sub.2).

(11) In Example 1 to Example 25, H.sub.3PO.sub.4 (2 g), FeC.sub.2O.sub.4.Math.2H.sub.2O (3.6 g), and LiOH.Math.H.sub.2O (0.84 g) were mixed in a ratio of 1:1:1, and dissolved in DEG (100 ml) to obtain a mixed organic solution (0.2 M). In Example 20 and Example 26, SDBS (0.02 mole) and SDS (0.01 mole) was also added respectively into the mixed organic solution. In Example 27, FeC.sub.2O.sub.4.Math.2H.sub.2O used in Example 1 was replaced by FeC.sub.2O.sub.4.Math.H.sub.2O:MnC.sub.2O.sub.4.Math.2H.sub.2O (9:1). In Example 28, FeC.sub.2O.sub.4.Math.2H.sub.2O used in Example 1 was replaced by FeC.sub.2O.sub.4.Math.H.sub.2O:NiC.sub.2O.sub.4.Math.2H.sub.2O (9:1). In Example 29, FeC.sub.2O.sub.4.Math.2H.sub.2O used in Example 1 was replaced by FeC.sub.2O.sub.4.Math.H.sub.2O:MnC.sub.2O.sub.4.Math.2H.sub.2O:NiC.sub.2O.sub.4.Math.2H.sub.2O (9:0.5:0.5). Next, the mixed organic solution was heated to 220° C. Then, N.sub.2 gas was introduced, the mixed organic solution was reacted under reflux, at 220° C. for a period of time (T2). The reaction was performed under atmospheric pressure. After the mixed organic solution was filtrated, the LiFePO.sub.4 precursor was obtained.

(12) The obtained LiFePO.sub.4 precursor was examined by an X-ray diffractometer (Shimadzu 6000) to obtain the crystal structure thereof. The X-ray diffraction pattern (XRD pattern) was obtained by applying Cu Ku radiation, the 2θ-scanning angle is ranged from 15° to 45°, and the scanning rate is 1°/min. The XRD pattern of the LiFePO.sub.4 precursor of Example 1 is shown in FIG. 1.

(13) The XRD pattern shown in FIG. 1 has characteristic peaks at near 2θ angles of 19.37° (peak 2), 21.47° (peak 4), 24.110 (peak 6), 25.95° (peak 7), 32.35° (peak 10), 35° (peak 11), 36.46° (peak 12), and 43.83° (peak 13). In addition, the XRD pattern shown in FIG. 1 further has characteristic peaks at near 2θ angles of 18.3° (peak 1), 28.91° (peak 8) and 30.05° (peak 9).

(14) The XRD pattern is different from the XRD pattern of LiFePO.sub.4 crystal with an olivine structure (JCPDS No. 81-1173). Thus, the LiFePO.sub.4 precursor of the present disclosure does not have an olivine structure.

(15) The LiFePO.sub.4 precursors prepared in Examples 2 to Example 29 are also examined by an X-ray diffractometer, and the obtained XRD patterns are similar to that shown in FIG. 1, except that some peaks (especially, the peak 1 and the peak 8) are very week or not found in the XRD patterns of the LiFePO.sub.4 precursors of some examples. The presences of the peak 1 and peak 8 are also listed in the following Table 1.

(16) TABLE-US-00001 TABLE 1 Temp 1 RH Temp 2 N.sub.2 Ex (° C.) (%) T1 T2 (° C.) (c.c./min) Peak 1 Peak 8 1 29 60 5 hr 29 min 3 hr 1 min 238 100+ V V 2 — — 8 hr 47 min 3 hr 24 min 237 100 V V 3 27 68 5 hr 44 min 3 hr 239 100+ V V 4 25 70 7 hr 12 min 3 hr 13 min 238 100+ V Δ 5 25 60 2 hr 57 min 3 hr 1 min 242 100+ V V 6 24 50 4 hr 43 min 3 hr 13 min 239 100+ V V 7 29 55 5 hr 30 min 3 hr 12 min 239 100+ V Δ 8 — — 4 hr 22 min 3 hr 236 100+ V V 9 — — 5 hr 15 min 3 hr 238 100+ Δ Δ 10 — — 6 hr 29 min 3 hr 2 min 236 100+ V Δ 11 — — 5 hr 44 min 3 hr 11 min 240 100+ V V 12 23 60 — — — 100+ V Δ 13 23 60 8 hr 9 min 3 hr 22 min 240 100 V V 14 23 60 8 hr 11 min 3 hr 6 min 235 100 V Δ 15 — — — — 241 100+ Δ Δ 16 25 70 4 hr 16 min 3 hr 4 min 234 100 X V 17 27 55 7 hr 37 min 3 hr 235 100 X Δ 18 25 65 8 hr 43 min 3 hr 234 100 X X 19 26 55 7 hr 2 min 3 hr 234 100 X X 20 23 60 15 hr 30 min 4 hr 19 min 240 100 X Δ 21 25 60 9 hr 46 min 5 hr 59 min 237 100 X X 22 27 70 10 hr 13 min 3 hr 235 100+ X X 23 — — 5 hr 25 min 5 hr 34 min 242 100+ X X 24 — — 4 hr 15 min 16 hr 23 min 243 100+ X X 25 29 65 8 hr 1 min 16 hr 241 100 X Δ 26 — — — 3 hr — 100 V Δ 27 — — — 3 hr — 100 X X 28 — — — 3 hr — 100 V V 29 — — — 3 hr — 100 V+ X V: Peak can be found. V+: Peak is very strong. Δ: Peak is very weak or almost disappears. X: Peak cannot be found. —: Not measured.

(17) According to the data shown in Table 1, the presences of the peak 1 and peak 8 may not be related to the ambient temperature, relative humidity, time for increasing to 220° C., reaction time, final temperature, and N.sub.2 gas flow. The intensity of the peaks (especially, the peak 1 and the peak 8) may be related to the compounds or the contents of the compounds existing in the LiFePO.sub.4 precursors.

(18) According to the XRD data (JCPDS card), it is found that the XRD pattern of the compound containing Li, Fe, P, O or H may have one peak with the strongest intensity. Herein, each peaks contributed by which crystallized compound are investigated by comparing the XRD pattern of FIG. 1 with JCPDS cards. The comparison results are listed in the following Table 2.

(19) TABLE-US-00002 TABLE 2 Com- Com- pound 1 pound 2 Peak JCPDS Compound 1 JCPDS Compound 2 2θ No. Formula No. Formula Peak 1 74-1910 Fe.sub.3O.sub.4 — — 18.3° Magnetite Peak 2 46-1551 C.sub.2H.sub.4Li.sub.4O.sub.7P.sub.2•H.sub.2O 44-812  Fe.sub.3H.sub.9(PO.sub.4).sub.6•6H.sub.2O 19.37° Lithium hydroxyl Iron hydrogen ethyldiene phosphate hydrate phosphonate Peak 4 80-2315 Fe.sub.2Fe(P.sub.2O.sub.7).sub.2 — — 21.47° Iron phosphate Peak 6 65-2754 FeLiO.sub.2 75-1603 Li.sub.2Fe.sub.2O.sub.4 24.11° Tetragonal Lithium iron(III) Lithium iron(III) oxide oxide Peak 7 72-2124 FePO.sub.4 33-1721 C.sub.6H.sub.6FeO.sub.8•2H.sub.2O 25.95° Iron(III) phosphate Iron hydrogen malonate dihydrate Peak 8 76-1761 Fe.sub.3PO.sub.7 28.91° Triiron(III) trioxide phosphate(V) Peak 9 72-2446 Fe.sub.3Fe.sub.4(PO.sub.4).sub.6 49-1209 C.sub.2HLiO.sub.4•H.sub.2O 30.05° Iron phosphate Lithium hydrogen oxalate hydrate Peak 10 72-464  FePO.sub.4(H.sub.2O).sub.2 32.35° Phosphosiderite Peak 11 74-115  Li.sub.2O.sub.2 35° Lithium peroxide Peak 12 89-4083 Li 36.46° Lithium Peak 13 48-582  Fe.sub.2O(PO.sub.4) 43.83° Alpha-iron oxide phosphate

(20) In addition, the LiFePO.sub.4 precursors obtained in Examples 1 to 29 were also examined by Inductively Coupled Plasma (ICP). The results show that the atomic ratio of Li, Fe and P was very close to 1:1:1 (i.e. Li:Fe:P=1:1:1) in the FePO.sub.4 precursors obtained in Examples 1 to 29, which indicated that the LiFePO.sub.4 precursors obtained in Examples 1 to 29 can be directly used to prepare the LiFePO.sub.4 electrode material.

Example 30 to Example 35

(21) In Example 30 to Example 35, the LiFePO.sub.4 precursors prepared in Examples 4, 6, 3, 13, 9, and 14 were respectively coated with a carbon source through a milling process to form a carbon layer on the powders of the LiFePO.sub.4 precursors. Briefly, a carbon source was dissolved in a milling solution, followed by mixing with the LiFePO.sub.4 precursor. Then, zirconia balls were used and the milling process was held for 2 hrs to obtain the LiFePO.sub.4 precursor with a carbon layer formed thereon. In Example 34, the milling solution with the carbon source (steric acid) was heated to well dissolve the steric acid.

(22) The diameter of the used zirconia balls, the milling solution used in the milling process, the carbon source, and the weight ratio of the carbon source to the LiFePO.sub.4 precursor are listed in the following Table 3. In addition, the obtained LiFePO.sub.4 precursor coated with the carbon source was also examined by an X-ray diffractometer (Shimadzu 6000) to obtain the crystal structure thereof. The XRD patterns of the LiFePO.sub.4 precursor with or without the carbon layer formed thereon were compared, and the comparison results are listed in the following Table 3.

(23) TABLE-US-00003 TABLE 3 Carbon source & LiFePO.sub.4 Milling weight Changes in the XRD Ex precursor Diameter solution ratio patterns 30 Example 4 0.8 mm   25 ml H.sub.2O Sucrose Peak 1 disappeared 0.15 Peak 8 disappeared Peak 9 weakened 31 Example 6 0.8 mm   5 ml H.sub.2O + Sucrose Peak 1 weakened 20 ml EtOH 0.15 Peak 8 disappeared Peak 9 weakened 32 Example 3 2 mm 25 ml H.sub.2O Sucrose Peak 1 weakened 0.15 Peak 8 disappeared Peak 9 weakened 33 Example 2 mm 5 ml H.sub.2O + Sucrose Peak 1 weakened 13 20 ml EtOH 0.15 Peak 8 disappeared Peak 9 weakened 34 Example 9 2 mm 30 ml EtOH Steric Peak 1 weakened acid Peak 8 disappeared 0.083 Peak 9 weakened 35 Example 2 mm 25 ml Poly- Peak 1 weakened 14 Toluene styrene Peak 8 disappeared 0.068 Peak 9 weakened

(24) The results of Example 30 to Example 35 indicate that the crystalline of the LiFePO.sub.4 precursor is decreased or the lattice of the crystals in the LiFePO.sub.4 precursor is destroyed due to the milling process. In addition, in Example 32 to Example 35, after the milling process, the decreasing level of the intensity of the peak 9 in Example 32 is greater than that in Example 33, the decreasing level of the intensity of the peak 9 in Example 33 is greater than that in Example 34, and the decreasing level of the intensity of the peak 9 in Example 35 is very small. These results indicate that the decreasing level of the intensity of the peak 9 is related to the water content in the milling solution.

(25) The shapes of the LiFePO.sub.4 precursor prepared in Example 1 were also observed with a high resolution transmission electron microscope (TEM) (JEOL 2010). FIG. 2A to FIG. 2C show TEM photos of one region of an LiFePO.sub.4 precursor according to Example 1 of the present disclosure.

(26) It is found that 80% of the LiFePO.sub.4 precursor is amorphous zones and 20% of the LiFePO.sub.4 precursor is crystallized zones, and the crystallized zones are spread among the amorphous zones.

(27) The left photo shown in FIG. 2A was observed at the magnification of 40,000×. The right photo shown in FIG. 2A is the circle region of the left photo, which is one flake of the LiFePO.sub.4 precursor and was observed at the magnification of 200,000×. The photo shown in FIG. 2B was observed at the magnification of 600,000×, which shows that one flake of the LiFePO.sub.4 precursor is formed by an amorphous zone and a crystallized zone. After measured by Gatan Microscopy Suite Software, the result shown in FIG. 2C shows that the d-spacing of the crystallized zone is 2.56 Å, which is consistent with the interplanar spacing of (1, 0, 1) planes of Li.sub.2O.sub.2(JCPDS No. 75-115). As shown in FIG. 1 and Table 2, the strongest peak of the LiFePO.sub.4 precursor is the peak 11, which is contributed by crystallized Li.sub.2O.sub.2. The crystallized zone shown in FIG. 2B and FIG. 2C has good crystalline and this crystallized zone is identified as the crystallized Li.sub.2O.sub.2; thus, the strongest peak 11 should be contributed by the crystallized Li.sub.2O.sub.2

(28) FIG. 3 is a TEM photo of another region an LiFePO.sub.4 precursor according to Example 1 of the present disclosure, which was observed at the magnification of 500,000×. It is found that different fringes can be found in one flake of the LiFePO.sub.4 precursor. As shown in FIG. 3, three zones indicated by A, B and C with different fringe directions can be found, and some zones without good crystalline may exist between the zones indicated by A, B and C. After measured by Gatan Microscopy Suite Software, in the zone A, the d-spacing of the crystallized zone is 2.465 Å, which is consistent with the interplanar spacing of (1, 1, 0) planes of Li (JCPDS No. 89-4083). In the zone B, the d-spacing of the crystallized zone is 2.72 Å, which is similar to the interplanar spacing of (1, 2, 2) planes of FePO.sub.4(H.sub.2O).sub.2 (JCPDS No. 72-464). In the zone C, the d-spacing of the crystallized zone is 2.06 Å, which is consistent with the interplanar spacing of (0, 3, 1) planes of Fe.sub.2O(PO.sub.4) (JCPDS No. 48-582). The crystallized zones A, B and C shown in FIG. 3 have good crystalline and these crystallized zones A, B and C are respectively identified as Li, the crystallized FePO.sub.4(H.sub.2O).sub.2 and the crystallized Fe.sub.2O(PO.sub.4); thus, the peaks 12, 10 and 13 should be respectively contributed by Li, the crystallized FePO.sub.4(H.sub.2O).sub.2 and the crystallized Fe.sub.2O(PO.sub.4).

(29) FIG. 4 is a TEM photo of further another region of an LiFePO.sub.4 precursor according to Example 1 of the present disclosure, which was observed at the magnification of 600,000×. It is found that different fringes can be found in one flake of the LiFePO.sub.4 precursor. As shown in FIG. 4, three zones indicated by D, E and F with different fringe directions can be found, and some zones without good crystalline may exist between the zones indicated by D, E and F. After measured by Gatan Microscopy Suite Software, in the zone D, the d-spacing of the crystallized zone is 2.54 Å, which is consistent with the interplanar spacing of (1, 3, 2) planes of C.sub.6H.sub.6FeO.sub.8.Math.2H.sub.2O (JCPDS No. 33-1721). In the zone E, the d-spacing of the crystallized zone is 3.07 Å, which is similar to the interplanar spacing of (0, 1, 2) planes of Fe.sub.3PO.sub.7 (JCPDS No. 76-1761). In the zone F, the d-spacing of the crystallized zone is 2.67 Å, which is consistent with the interplanar spacing of (2, 1, 1) planes of Fe.sub.3Fe.sub.4(PO.sub.4).sub.6(JCPDS No. 72-2446). The crystallized zones D, E and F shown in FIG. 4 have good crystalline and these crystallized zones D, E and F are respectively identified as the crystallized C.sub.6H.sub.6FeO.sub.8.Math.2H.sub.2O, the crystallized Fe.sub.3PO.sub.7 and the crystallized Fe.sub.3Fe.sub.4(PO.sub.4).sub.6; thus, the peaks 7, 8 and 9 should be respectively contributed by the crystallized C.sub.6H.sub.6FeOs.sub.8.2H.sub.2O, the crystallized Fe.sub.3PO.sub.7 and the crystallized Fe.sub.3Fe.sub.4(PO.sub.4).sub.6.

(30) According to the results shown in FIG. 2A to FIG. 4, the LiFePO.sub.4 precursor are powders comprising amorphous zones and crystallized zones contributed from different crystallized compounds. Thus, the powders of the LiFePO.sub.4 precursor are constituted by different crystallized compounds. In particular, one flake of the powder of the LiFePO.sub.4 precursor may be constituted by more than one crystallized compounds.

(31) The shapes of the LiFePO.sub.4 precursor prepared in Example 1 were also observed with a scanning electron microscope (SEM) (Hitachi S-4000). The results are shown in FIG. 5A to FIG. 5F.

(32) FIG. 5A was observed at the magnification of 10,000×. It can be found that the LiFePO.sub.4 precursor is a powder having flakes, and a diameter of the powder is about 5 μm. It can also be found that the powder have plural flakes, which are gathered to form a flower-like shape. FIG. 5B was observed at the magnification of 40,000×. It can be found that each flake has a length of about 700 nm to 1000 nm. FIG. 5C was observed at the magnification of 150,000×. It can be found that each flake has a width of about 5 nm to 14 nm.

(33) In addition to the shapes shown in FIG. 5A to FIG. 5C, the powder of the LiFePO.sub.4 precursor may have other shape, in which the flakes are laminated to form a shale-like shape. FIG. 5D was observed at the magnification of 10,000×, which shows that some flakes are gathered to form a flower-like shape and some flakes are laminated to form a shale-like shape. FIG. 5E was observed at the magnification of 80,000×. It can be found that the gaps are present between flakes to form the shale-like shape.

(34) FIG. 5F was observed at the magnification of 150,000×. It can be found that each flake has a thickness of about 5 nm to 10 nm. Thus, the flakes of the powders of the LiFePO.sub.4 precursor have similar thicknesses despite the shapes of the powders.

(35) According to the results shown in FIG. 5A to FIG. 5G, the LiFePO.sub.4 precursor is a powder constituted with flakes. When the LiFePO.sub.4 precursor of the present disclosure is heat-treated to form LiFePO.sub.4, the obtained LiFePO.sub.4 powder can also be a powder constituted with flakes. Thus, Li ions can extract from the powders in a uniform and high-density manner, so the current density of the Li-ion batteries can be further increased.

Example 36 to Example 43

(36) H.sub.3PO.sub.4, FeC.sub.2O.sub.4, and LiOH were mixed in a ratio of 1:1:1, and dissolved in DEG to obtain a mixed organic solution. Next, the mixed organic solution was heated to 220° C. Then, N.sub.2 gas was introduced, the mixed organic solution was reacted under reflux, at 220° C. for 3 hrs. After the mixed organic solution was filtrated, synthetic powders were obtained.

(37) The synthetic powders were washed with DI water for three times, followed by dried at 55° C. to obtain the LiFePO.sub.4 precursors.

(38) The obtained LiFePO.sub.4 precursors were respectively mixed with sucrose (15 wt %), and the mixtures were mixed by using a 3D mixer for 2 hrs to obtain mixing powders.

(39) The mixing powders were placed in a vacuum heat treatment furnace introduced with N.sub.2 gas or a heat treatment furnace introduced with N.sub.2 constant airflow, and the heat treatment was held at 750° C. for 2 hrs. Then, LiFePO.sub.4 powders for an electrode material were obtained.

(40) The LiFePO.sub.4 precursors prepared in Examples 36 to Example 43 were also examined by an X-ray diffractometer, and the obtained XRD patterns are similar to that shown in FIG. 1. Herein, only the peak 1 and the peak 8 are listed in the following Table 4.

(41) In addition, the shapes of the LiFePO.sub.4 precursors and LiFePO.sub.4 powders prepared in Example 36 to Example 43 were also observed with a scanning electron microscope (SEM) (Hitachi S-4000). The results are summarized in the following Table 4.

(42) TABLE-US-00004 TABLE 4 Concentration XRD features of Shapes of the Shapes of the DEG of the mixed the LiFePO.sub.4 LiFePO.sub.4 LiFePO.sub.4 Ex (ml) organic solution precursors precursors powders 36 100 0.22M Peak 1: small Petals and plates Petals and plates Peak 8: small Thickness: Thickness: 18~24 nm 5~25 nm Length of the Length of the petals: petals: 700~1,800 nm 550~1,400 nm Length of the Length of the plates: plates: 1,500~2,000 nm 700~1,400 nm 37 150 0.22M Peak 1: medium Petals and plates Petals and plates Peak 8: small Thickness: Thickness: 15~20 nm 16~20 nm Length of the Length of the petals: petals: 800~1,800 nm 450~1,300 nm Length of the Length of the plates: plates: 800~2,400 nm 800~2,100 nm 38 100 0.33M Peak 1: medium Petals and plates Petals and plates Peak 8: small Thickness: Thickness: 20~25 nm 12~20 nm Length of the Length of the petals: petals: 800~2,000 nm 650~1,400 nm Length of the Length of the plates: plates: 800~1,900 nm 800~2,000 nm 39 150 0.33M Peak 1: medium Petals and plates Petals and plates Peak 8: small Thickness: Thickness: 12~24 nm 10~20 nm Length of the Length of the petals: petals: 600~1,700 nm 500~1,300 nm Length of the Length of the plates: plates: 800~1,900 nm 900~2,000 nm 40 100 0.44M Peak 1: medium Petals and plates Petals and plates Peak 8: small Thickness: Thickness: 15~20 nm 12~24 nm Length of the Length of the petals: petals: 450~1,500 nm 350~1,300 nm Length of the Length of the plates: plates: 450~2,000 nm 500~1,800 nm 41 150 0.44M Peak 1: medium Petals and plates Petals and plates Peak 8: small Thickness: Thickness: 16~20 nm 12~21 nm Length of the Length of the petals: petals: 550~1,550 nm 600~1,500 nm Length of the Length of the plates: plates: 500~2,600 nm 600~1,900 nm 42 960 0.48M Peak 1: very Petals (with a 3D Petals and plates small structure) and Thickness: Peak 8: plates 20 nm disappeared Thickness: Length of the 14~23 nm petals: Length of the 400~1,750 nm petals: Length of the 600~2,000 nm plates: Length of the 400~2,400 nm plates: 800~2,400 nm Gap between plates: >20 nm 43 67 0.66M Peak 1: large Petals and plates Petals and plates Peak 8: small Thickness: Thickness: 12~20 nm 15~22 nm Length of the Length of the petals: petals: 500~1,500 nm 550~1,500 nm Length of the Length of the plates: plates: 800~1,600 nm 700~1,500 nm

(43) Although the present invention has been explained by 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 present disclosure as hereinafter claimed.