CATHODE MATERIAL PRECURSOR AND PREPARATION METHOD AND APPLICATION THEREOF

Abstract

The invention relates to the field of battery materials, and discloses a cathode material precursor and a preparation method and application thereof. The chemical formula of the cathode material precursor is Ni.sub.xCo.sub.yMn.sub.z(OH).sub.2, wherein 0.2≤x≤1, 0≤y≤0.5, 0≤z≤0.6, and 0.8≤x+y+z≤1. The cathode material precursor is in a shape of a stack of lamellae, and has a particle size broadening factor K, where K≤0.85. In the invention, the preparation process of the precursor is effectively controlled and adjusted by the controlled crystallization method combined with Lamer nucleation and growth theoretical model. The prepared precursor has morphology characteristics of concentrated particle size distribution and high proportion of {010} active crystal plane family, and has capacity retention up to 91.33% at a rate of 20C.

Claims

1. A cathode material precursor, wherein the cathode material precursor has a chemical formula of Ni.sub.xCo.sub.yMn.sub.z(OH).sub.2, where 0.2≤x≤1, 0≤y≤0.5, 0≤z≤0.6, and 0.8≤x+y+z≤1; the cathode material precursor is in a shape of a stack of lamella, and has a particle size broadening factor K, where K≤0.85.

2. The cathode material precursor of claim 1, wherein the cathode material precursor has 40% to 80% of {010} crystal plane family, and the {010} crystal plane family in the cathode material precursor includes active crystal planes (010), (010), (100), (110), (110), and (100).

3. A preparation method of a cathode material precursor of claim 1, wherein the preparation method comprises steps of: preparing a metal salt solution of nickel, cobalt and manganese; adding thereto a complexing agent and then a precipitating agent to carry out nucleation reaction; adjusting concentrations of the metal salt solution of nickel, cobalt and manganese and the complexing agent to carry out growth reaction; and carrying out filtering, aging, and drying to obtain the cathode material precursor.

4. A preparation method of a cathode material precursor of claim 2, wherein the preparation method comprises steps of: preparing a metal salt solution of nickel, cobalt and manganese; adding thereto a complexing agent and then a precipitating agent to carry out nucleation reaction; adjusting concentrations of the metal salt solution of nickel, cobalt and manganese and the complexing agent to carry out growth reaction; and carrying out filtering, aging, and drying to obtain the cathode material precursor.

5. The preparation method of claim 3, wherein the complexing agent is a basic nitrogen-containing substance and the basic nitrogen-containing substance is ammonia water; the precipitating agent is at least one selected from a group consisting of sodium hydroxide and sodium carbonate; and the metal salt solution of nickel, cobalt and manganese is at least one selected from a group consisting of solutions of sulfates, nitrates, oxalates and hydrochlorides of nickel, cobalt and manganese.

6. The preparation method of claim 4, wherein the complexing agent is a basic nitrogen-containing substance and the basic nitrogen-containing substance is ammonia water; the precipitating agent is at least one selected from a group consisting of sodium hydroxide and sodium carbonate; and the metal salt solution of nickel, cobalt and manganese is at least one selected from a group consisting of solutions of sulfates, nitrates, oxalates and hydrochlorides of nickel, cobalt and manganese.

7. The preparation method of claim 3, wherein the metal salt solution of nickel, cobalt and manganese in the nucleation reaction has a concentration in a range from 0.5 to 2 mol/L, the metal salt solution of nickel, cobalt and manganese in the growth reaction has a concentration in a range from 1.5 to 3 mol/L; the complexing agent in the nucleation reaction has a concentration in a range from 0.5 to 2.5 g/L, the complexing agent in the growth reaction has a concentration in a range from 2 to 5 g/L; and the nucleation reaction is carried out for 24 to 50 hours, and the growth reaction is carried out for 60 to 100 hours.

8. The preparation method of claim 4, wherein the metal salt solution of nickel, cobalt and manganese in the nucleation reaction has a concentration in a range from 0.5 to 2 mol/L, the metal salt solution of nickel, cobalt and manganese in the growth reaction has a concentration in a range from 1.5 to 3 mol/L; the complexing agent in the nucleation reaction has a concentration in a range from 0.5 to 2.5 g/L, the complexing agent in the growth reaction has a concentration in a range from 2 to 5 g/L; and the nucleation reaction is carried out for 24 to 50 hours, and the growth reaction is carried out for 60 to 100 hours.

9. A cathode material for lithium ion batteries, wherein the cathode material for lithium ion batteries is prepared from raw materials comprising a cathode material precursor of claim 1.

10. A cathode material for lithium ion batteries, wherein the cathode material for lithium ion batteries is prepared from raw materials comprising a cathode material precursor of claim 2.

11. The cathode material for lithium ion batteries of claim 9, wherein the cathode material for lithium ion batteries has a chemical formula of Li.sub.aNi.sub.xCo.sub.yMn.sub.zM.sub.bO.sub.2, where 0.9≤a≤1.4, 0.2≤x≤1, 0≤y≤0.5, 0≤z≤0.6, 0≤b≤0.1, 0.8≤x+y+z≤1, 1≤a/(x+y+z)≤1.5; and M is at least one selected from a group consisting of elements B, Al, Mg, Ti, Fe, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Sn, Sb, La, Ce, W, and Ta.

12. The cathode material for lithium ion batteries of claim 10, wherein the cathode material for lithium ion batteries has a chemical formula of LiaNixCoyMnzMbO2, where 0.9≤a≤1.4, 0.2≤x≤1, 0≤y≤0.5, 0≤z≤0.6, 0≤b≤0.1, 0.8≤x+y+z≤1, 1≤a/(x+y+z)≤1.5; and M is at least one selected from a group consisting of elements B, Al, Mg, Ti, Fe, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Sn, Sb, La, Ce, W, and Ta.

13. A preparation method of a cathode material for lithium ion batteries of claim 9, wherein the preparation method comprises steps of: mixing a cathode material precursor, a lithium source and an additive to obtain a mixture, subjecting the mixture to first sintering and pulverization, and then to second sintering and cooling, to obtain the cathode material for lithium ion batteries.

14. A preparation method of a cathode material for lithium ion batteries of claim 10, wherein the preparation method comprises steps of: mixing a cathode material precursor, a lithium source and an additive to obtain a mixture, subjecting the mixture to first sintering and pulverization, and then to second sintering and cooling, to obtain the cathode material for lithium ion batteries.

15. The preparation method of claim 13, wherein the lithium source is at least one selected from a group consisting of lithium carbonate and lithium hydroxide; and the additive is at least one selected from a group consisting of oxides of B, Al, Mg, Ti, Fe, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Sn, Sb, La, Ce, W, and Ta.

16. The preparation method of claim 14, wherein the lithium source is at least one selected from a group consisting of lithium carbonate and lithium hydroxide; and the additive is at least one selected from a group consisting of oxides of B, Al, Mg, Ti, Fe, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Sn, Sb, La, Ce, W, and Ta.

17. A battery, wherein the battery comprises a cathode material for lithium ion batteries of claim 9.

18. A battery, wherein the battery comprises a cathode material for lithium ion batteries of claim 10.

19. A battery, wherein the battery comprises a cathode material for lithium ion batteries of claim 11.

20. A battery, wherein the battery comprises a cathode material for lithium ion batteries of claim 12.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0035] FIG. 1 is a schematic structure diagram of a precursor with a high proportion of {010} active crystal plane family prepared in Example 1 of the invention; and

[0036] FIGS. 2(a) and 2(b) respectively show SEM images of a precursor and a high power cathode material prepared in Example 1 of the invention.

DETAILED DESCRIPTION

[0037] In order to make the technical solutions of the invention more clearly understood by those skilled in the art, the following examples are listed for description. It should be pointed out that the following examples do not limit the scope of protection claimed by the invention.

[0038] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be purchased commercially, or can be obtained by existing known methods.

Example 1

[0039] A cathode material precursor in this example has a chemical formula of Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(OH).sub.2, is obviously in a shape of a stack of lamellae, and has a particle size broadening factor K, where K=0.75.

[0040] A preparation method of the cathode material precursor in this example comprises the following steps of:

[0041] According to the molar ratio of Ni:Co:Mn of 5:3:2, dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in deionized water to obtain a metal salt solution with a concentration of 0.5 mol/L, adjusting a concentration of ammonia water as a complexing agent to 0.5 g/L, and adding the metal salt solution, ammonia water, and NaOH into a reaction kettle with a peristaltic pump; carrying out a first reaction for 48 hours with a reaction temperature controlled to 70° C. and a stirring speed of 200 r/min; adjusting the concentration of the metal salt solution to 2 mol/L and the concentration of ammonia water to 2 g/L, then carrying out a second reaction for 72 hours; and subjecting the resulting reaction solution to solid-liquid separation, aging, washing, drying, and sieving, to obtain the precursor Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(OH).sub.2, with a particle size broadening factor K=0.75 and micro morphology shown in FIG. 2(a).

[0042] A cathode material for lithium ion batteries in this example is prepared from raw materials comprising the aforementioned cathode material precursor, and has a chemical formula of Li.sub.1.15Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(ZrAl).sub.0.03O.sub.2.

[0043] A preparation method of the cathode material for lithium ion batteries in this example comprises the following steps of:

[0044] Mixing thoroughly the aforementioned cathode material precursor and lithium carbonate at a molar ratio of 1:1.15, with the doping element M being 1500 ppm Zr and 1500 ppm Al (Zr and Al being doped in the form of Zr and Al oxides), to obtain a mixture; and subjecting the mixture to first sintering for 72 hours at 810° C. in an air atmosphere, pulverization and coating, and then to second sintering for 6 hours at 450° C. in an air atmosphere and cooling, to obtain the cathode material for lithium ion batteries, Li.sub.1.15Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(ZrAl).sub.0.03O.sub.2, with micro morphology shown in FIG. 2(b).

[0045] FIG. 1 is a schematic structure diagram of the precursor with a high proportion of {010} active crystal plane family prepared in Example 1 of the invention. The left shows a lower proportion of active crystal planes, and the sum of area of active crystal planes (010), (010), (100), (110), (110), and (100) accounts for less surface area of the cuboid. The right shows a higher proportion of active crystal planes, and the sum of area of the active crystal planes (010), (010), (100), (110), (110), and (100) accounts for more surface area of the cuboid, which indicates that more diffusion channels can be provided for lithium ions.

[0046] FIGS. 2(a) and 2(b) respectively show SEM images of the precursor and the high power cathode material prepared in Example 1 of the invention. It can be seen from FIG. 2(a) that the prepared precursor has morphological characteristics of concentrated particle size distribution and high proportion of {010} active crystal plane family. It can be seen from FIG. 2(b) that the prepared cathode material for lithium ion batteries still greatly maintain the morphological characteristics of the precursor after high-temperature sintering, thereby providing more channels for diffusion and migration of Li.sup.+ and exerting a high power characteristic.

[0047] The higher the discharge capacity retention of a cathode material at high rates, the better the power performance of the cathode material. Therefore, the cathode material Li.sub.1.15Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(ZrAl).sub.0.03O.sub.2 prepared in Example 1 is produced into a half cell and subjected to charge and discharge tests at different rates to characterize its rate performance. The capacity retention (relative to that at 1C) of the prepared high power type cathode material Li.sub.1.15Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(ZrAl).sub.0.03O.sub.2 at different rates is shown in Table 1 below.

TABLE-US-00001 TABLE 1 Rate 2 C/1 C 5 C/1 C 10 C/1 C 20 C/1 C Capacity retention 98.21 95.84 92.37 88.19 (%)

[0048] It can be seen from Table 1 that the capacity retention of the cathode material for lithium ion batteries of Example 1 can be up to 88.19% even at 20C, which indicates that the cathode material for lithium ion batteries possesses a high power characteristic.

Example 2

[0049] A cathode material precursor in this example has a chemical formula of Ni.sub.0.5Co.sub.0.5(OH).sub.2, is obviously in a shape of a stack of lamellae, and has a particle size broadening factor of 0.72, where 0.72=(D.sub.v90−D.sub.v10)/D.sub.v50.

[0050] A preparation method of the cathode material precursor in this example comprises the following steps of:

[0051] According to the molar ratio of Ni:Co of 5:5, dissolving nickel acetate and cobalt acetate in deionized water to obtain a metal salt solution with a concentration of 1 mol/L, adjusting a concentration of ammonia water as a complexing agent to 0.8 g/L, and adding the metal salt solution, ammonia water, and NaOH into a reaction kettle with a peristaltic pump; carrying out a first reaction for 30 hours with a reaction temperature controlled to 60° C. and a stirring speed of 400 r/min; adjusting the concentration of the metal salt solution to 1.5 mol/L and the concentration of ammonia water to 2.5 g/L, then carrying out a second reaction for 60 hours; and subjecting the resulting reaction solution to solid-liquid separation, aging, washing, drying, and sieving, to obtain the precursor Ni.sub.0.5Co.sub.0.5(OH).sub.2 with a particle size broadening factor K=0.72.

[0052] A cathode material for lithium ion batteries in this example is prepared from raw materials comprising the aforementioned cathode material precursor, and has a chemical formula of Li.sub.1.25Ni.sub.0.5Co.sub.05(BSr).sub.0.016O.sub.2.

[0053] A preparation method of the cathode material for lithium ion batteries in this example comprises the following steps of:

[0054] Mixing thoroughly the aforementioned cathode material precursor and lithium carbonate at a molar ratio of 1:1.25, with the doping element M being 600 ppm B and 1000 ppm Sr (B and Sr being doped in the form of B and Sr oxides), to obtain a mixture; and subjecting the mixture to first sintering for 18 hours at 790° C. in an air atmosphere, pulverization and coating, and then to second sintering for 5 hours at 550° C. in an air atmosphere and cooling, to obtain the cathode material for lithium ion batteries, Li.sub.1.25Ni.sub.0.5Co.sub.0.5(BSr).sub.0.016O.sub.2.

[0055] The high power type cathode material Li.sub.1.25Ni.sub.0.5Co.sub.0.5(BSr).sub.0.016O.sub.2 prepared in Example 2 is produced into a half cell and subjected to charge and discharge tests at different rates to characterize its rate performance. The capacity retention (relative to that at 1C) of the prepared high power type cathode material Li.sub.1.25Ni.sub.0.5Co.sub.0.5(BSr).sub.0.016O.sub.2 at different rates is shown in Table 2 below.

TABLE-US-00002 TABLE 2 Rate 2 C/1 C 5 C/1 C 10 C/1 C 20 C/1 C Capacity retention 98.76 97.88 94.93 91.33 (%)

[0056] It can be seen from Table 2 that the capacity retention of the cathode material for lithium ion batteries of Example 2 can be up to 91.33% even at 20C, which indicates that the cathode material for lithium ion batteries possesses a high power characteristic.

Example 3

[0057] A cathode material precursor in this example has a chemical formula of Ni.sub.0.2Mn.sub.0.6(OH).sub.2, is obviously in a shape of a stack of lamellae, and has a particle size broadening factor of 0.73, where 0.73=(D.sub.v90−D.sub.v10)/D.sub.v50.

[0058] A preparation method of the cathode material precursor in this example comprises the following steps of:

[0059] According to the molar ratio of Ni:Mn of 2:6, dissolving nickel acetate and manganese acetate in deionized water to obtain a metal salt solution with a concentration of 0.5 mol/L, adjusting a concentration of ammonia water as a complexing agent to 2.5 g/L, and adding the metal salt solution, ammonia water, and NaOH into a reaction kettle with a peristaltic pump; carrying out a first reaction for 48 hours with a reaction temperature controlled to 40° C. and a stirring speed of 100 r/min; adjusting the concentration of the metal salt solution to 3 mol/L and the concentration of ammonia water to 5 g/L, then carrying out a second reaction for 100 hours; and subjecting the resulting reaction solution to solid-liquid separation, aging, washing, drying, and sieving, to obtain the precursor Ni.sub.0.2Mn.sub.0.6(OH).sub.2 with a particle size broadening factor K=0.73.

[0060] A cathode material for lithium ion batteries in this example is prepared from raw materials comprising the aforementioned cathode material precursor, and has a chemical formula of Li.sub.1.4Ni.sub.0.2Mn.sub.0.6(WTa).sub.0.03O.sub.2.

[0061] A preparation method of the cathode material for lithium ion batteries in this example comprises the following steps of:

[0062] Mixing thoroughly the aforementioned cathode material precursor and lithium carbonate at a molar ratio of 1:1.4, with the doping element M being 2000 ppm W and 1000 ppm Ta (W and Ta being doped in the form of W and Ta oxides), to obtain a mixture; and subjecting the mixture to first sintering for 20 hours at 950° C. in an air atmosphere, pulverization and coating, and then to second sintering for 5 hours at 450° C. in an air atmosphere and cooling, to obtain the cathode material for lithium ion batteries, Li.sub.1.4Ni.sub.0.2Mn.sub.0.6(WTa).sub.0.03O.sub.2.

[0063] The cathode material Li.sub.1.4Ni.sub.0.2Mn.sub.0.6(WTa).sub.0.03O.sub.2 prepared in Example 3 is produced into a half cell and subjected to charge and discharge tests at different rates to characterize its rate performance. The capacity retention (relative to that at 1C) of the prepared high power type cathode material Li.sub.1.4Ni.sub.0.2Mn.sub.0.6(WTa).sub.0.03O.sub.2 at different rates is shown in Table 3 below.

TABLE-US-00003 TABLE 3 Rate 2 C/1 C 5 C/1 C 10 C/1 C 20 C/1 C Capacity retention 95.72 92.57 90.43 87.59 (%)

[0064] It can be seen from Table 3 that the capacity retention of the cathode material for lithium ion batteries of Example 3 can be up to 87.59% even at 20C, which indicates that the cathode material for lithium ion batteries possesses a high power characteristic.

Example 4

[0065] A cathode material precursor in this example has a chemical formula of Ni.sub.0.8Mn.sub.0.2(OH).sub.2, is obviously in a shape of a stack of lamellae, and has a particle size broadening factor of 0.68, where 0.68=(D.sub.v90−D.sub.v10)/D.sub.v50.

[0066] A preparation method of the cathode material precursor in this example comprises the following steps of:

[0067] According to the molar ratio of Ni:Mn of 8:2, dissolving nickel acetate and manganese acetate in deionized water to obtain a metal salt solution with a concentration of 2 mol/L, adjusting a concentration of ammonia water as a complexing agent to 0.5 g/L, and adding the metal salt solution, ammonia water, and NaOH into a reaction kettle with a peristaltic pump; carrying out a first reaction for 40 hours with a reaction temperature controlled to 55° C. and a stirring speed of 300 r/min; adjusting the concentration of the metal salt solution to 2.5 mol/L and the concentration of ammonia water to 4 g/L, then carrying out a second reaction for 80 hours; and subjecting the resulting reaction solution to solid-liquid separation, aging, washing, drying, and sieving, to obtain the precursor Ni.sub.0.8Mn.sub.0.2(OH).sub.2 with a particle size broadening factor K=0.68.

[0068] A cathode material for lithium ion batteries in this example is prepared from raw materials comprising the aforementioned cathode material precursor, and has a chemical formula of Li.sub.1.15Ni.sub.0.8Mn.sub.0.2(Mo).sub.0.03O.sub.2.

[0069] A preparation method of the cathode material for lithium ion batteries in this example comprises the following steps of:

[0070] Mixing thoroughly the aforementioned cathode material precursor and lithium carbonate at a molar ratio of 1:1.15, with the doping element M being 3000 ppm Mo (Mo being doped in the form of Mo oxide), to obtain a mixture; and subjecting the mixture to first sintering for 30 hours at 750° C. in an air atmosphere, pulverization and coating, and then to second sintering for 8 hours at 300° C. in an air atmosphere and cooling, to obtain the cathode material for lithium ion batteries, Li.sub.1.15Ni.sub.0.8Mn.sub.0.2(Mo).sub.0.03O.sub.2.

[0071] The cathode material Li.sub.1.15Ni.sub.0.8Mn.sub.0.2(Mo).sub.0.03O.sub.2 prepared in Example 4 is produced into a half cell and subjected to charge and discharge tests at different rates to characterize its rate performance. The capacity retention (relative to that at 1C) of the prepared high power type cathode material Li.sub.1.15Ni.sub.0.8Mn.sub.0.2(Mo).sub.0.03O.sub.2 at different rates is shown in Table 4 below.

TABLE-US-00004 TABLE 4 Rate 2 C/1 C 5 C/1 C 10 C/1 C 20 C/1 C Capacity retention 97.90 96.83 93.53 90.19 (%)

[0072] It can be seen from Table 4 that the capacity retention of the cathode material for lithium ion batteries of Example 4 can be up to 90.91% even at 20C, which indicates that the cathode material for lithium ion batteries possesses a high power characteristic.

Comparative Example 1

[0073] The precursor in Comparative Example 1 is prepared through a conventional co-precipitation method, and the prepared precursor does not have a high proportion of {010} active crystal plane family.

[0074] A preparation method of a cathode material for lithium ion batteries by using the precursor comprises the following steps of: [0075] (1) According to the molar ratio of Ni:Co:Mn of 5:3:2, dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in deionized water to obtain a metal salt solution with a concentration of 2 mol/L, adjusting a concentration of ammonia water as a complexing agent to 2 g/L, and adding the metal salt solution, ammonia water, and NaOH into a reaction kettle with a peristaltic pump; carrying out the reaction for 120 hours with a reaction temperature controlled to 70° C. and a stirring speed of 200 r/min; and subjecting the resulting reaction solution to solid-liquid separation, aging, washing, drying, and sieving, to obtain the precursor Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(OH).sub.2, with a particle size broadening factor K=0.87; and [0076] (2) Mixing thoroughly the aforementioned precursor and lithium carbonate at a molar ratio of 1:1.15, with the doping element M being 1500 ppm Zr and 1500 ppm Al (Zr and Al being doped in the form of Zr and Al oxides), to obtain a mixture; and subjecting the mixture to first sintering for 27 hours at 810° C. in an air atmosphere, pulverization and coating, and then to second sintering for 6 hours at 450° C. in an air atmosphere and cooling, to obtain the Zr and Al co-doped cathode material for lithium ion batteries, Li.sub.1.15Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(ZrAl).sub.0.03O.sub.2.

[0077] The cathode material Li.sub.1.15Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(ZrAl).sub.0.03O.sub.2 prepared in Comparative Example 1 is produced into a half cell and subjected to charge and discharge tests at different rates to characterize its rate performance. The capacity retention (relative to that at 1C) of the prepared cathode material Li.sub.1.15Ni.sub.0.5Co.sub.0.3Mn.sub.0.2(ZrAl).sub.0.03O.sub.2 at different rates is shown in Table 5 below.

TABLE-US-00005 TABLE 5 Rate 2 C/1 C 5 C/1 C 10 C/1 C 20 C/1 C Capacity retention 86.37 82.44 76.49 67.23 (%)

[0078] It can be seen from Table 5 that the capacity retention of the cathode material for lithium ion batteries of Comparative Example 1 is only 67.23% at 20C, which indicates that the cathode material for lithium ion batteries does not possess a high power characteristic.

Comparative Example 2

[0079] A cathode material precursor in this comparative example has a chemical formula of Ni.sub.0.5Co.sub.0.5(OH).sub.2, is obviously in a shape of a stack of lamellae, and has a particle size broadening factor of 0.90, where 0.90=(D.sub.v90−D.sub.v10)/D.sub.v50.

[0080] A preparation method of the cathode material precursor in this comparative example comprises the following steps of:

[0081] According to the molar ratio of Ni:Co of 5:5, dissolving nickel acetate and cobalt acetate in deionized water to obtain a metal salt solution with a concentration of 1 mol/L, adjusting a concentration of ammonia water as a complexing agent to 0.8 g/L, and adding the metal salt solution, ammonia water, and NaOH into a reaction kettle with a peristaltic pump; carrying out the reaction for 120 hours with a reaction temperature controlled to 60° C. and a stirring speed of 400 r/min; and subjecting the resulting reaction solution to solid-liquid separation, aging, washing, drying, and sieving, to obtain the precursor Ni.sub.0.5Co.sub.0.5(OH).sub.2 with a particle size broadening factor K=0.90.

[0082] A cathode material for lithium ion batteries in this comparative example is prepared from raw materials comprising the aforementioned cathode material precursor, and has a chemical formula of Li.sub.1.25Ni.sub.0.5Co.sub.0.5(BSr).sub.0.016O.sub.2.

[0083] A preparation method of the cathode material for lithium ion batteries in this comparative example comprises the following steps of:

[0084] Mixing thoroughly the aforementioned precursor and lithium carbonate at a molar ratio of 1:1, with the doping element M being 600 ppm B and 1000 ppm Sr (B and Sr being doped in the form of B and Sr oxides), to obtain a mixture; and subjecting the mixture to first sintering for 18 hours at 790° C. in an air atmosphere, pulverization and coating, and then to second sintering for 5 hours at 550° C. in an air atmosphere and cooling, to obtain the cathode material for lithium ion batteries, Li.sub.1.25Ni.sub.0.5Co.sub.0.5(BSr).sub.0.016O.sub.2.

[0085] The high power type cathode material Li.sub.1.25Ni.sub.0.5Co.sub.0.5(BSr).sub.0.016O.sub.2 prepared in Comparative Example 2 is produced into a half cell and subjected to charge and discharge tests at different rates to characterize its rate performance. The capacity retention (relative to that at 1C) of the prepared high power type cathode material Li.sub.1.25Ni.sub.0.5Co.sub.0.5(BSr).sub.0.016O.sub.2 at different rates is shown in Table 6 below.

TABLE-US-00006 TABLE 6 Rate 2 C/1 C 5 C/1 C 10 C/1 C 20 C/1 C Capacity retention 94.29 91.36 88.49 83.20 (%)

[0086] It can be seen from Table 6 that the capacity retention of the cathode material for lithium ion batteries of Comparative Example 2 can be up to 83.20% even at 20C, which indicates that the cathode material for lithium ion batteries possesses a high power characteristic.