HIGH-VOLTAGE LOW-COBALT TERNARY POSITIVE ELECTRODE MATERIAL, PREPARATION METHOD THEREFOR, AND USE THEREOF

Abstract

A high-voltage low-cobalt ternary positive electrode material has a general formula Li.sub.aNi.sub.bCo.sub.cMn.sub.dO.sub.2, where 0.97a1.1, 0.5b0.76, 0c0.1, 0.24d0.5, b+c+d=1, and c<0.35d. Compared with the prior art, the positive electrode material can be used at a higher voltage compared to other ternary positive electrode materials which have the same nickel content as the positive electrode material, such that the energy density is increased, and because the positive electrode material has a smaller change in size, the cracking and powdering of the positive electrode material are avoided, the service life of the material is prolonged, and the safety performance of the material is improved.

Claims

1. A high-voltage low-cobalt ternary cathode material, wherein the high-voltage low-cobalt ternary cathode material has a general formula Li.sub.aNi.sub.bCo.sub.cMn.sub.dO.sub.2, wherein 0.97a1.1, 0.5b0.76, 0c0.1, 0.24d0.5, b+c+d=1, and c<0.35d.

2. The high-voltage low-cobalt ternary cathode material of claim 1, wherein the high-voltage low-cobalt ternary cathode material has a lithium-nickel disordering ratio (), 27.

3. The high-voltage low-cobalt ternary cathode material of claim 1, wherein in terms of capacity, the high-voltage low-cobalt ternary cathode material has a 0.1 C capacity of no more than 185 mAh/g at an operating voltage ranging from 3V to 4.3 V, and a 0.1 C capacity of no more than 210 mAh/g at an operating voltage ranging from 3 V to 4.5 V.

4. The high-voltage low-cobalt ternary cathode material of claim 1, wherein the high-voltage low-cobalt ternary cathode material is used at an operating voltage greater than or equal to 4.3 V, preferably at an operating voltage greater than or equal to 4.35 V, and more preferably at an operating voltage greater than or equal to 4.40 V.

5. A method for preparing the high-voltage low-cobalt ternary cathode material of claim 1, comprising the following steps: step 1: dissolving NiSO.sub.4.Math.6H.sub.2O, MnSO.sub.4.Math.H.sub.2O and CoSO.sub.4.Math.7H.sub.2O in deionized water to obtain a salt solution; step 2: adding deionized water into a reaction vessel, and adding a concentrated ammonia water into the deionized water to formulate a base solution containing ammonia water; adding the salt solution obtained in step 1, as well as a sodium hydroxide solution and the concentrated ammonia water into the base solution dropwise at the same time, respectively; wherein the reaction vessel is provided with an overflow port, and with the dropwise addition of the salt solution, the sodium hydroxide solution, and the concentrated ammonia water, an overflow is maintained continuously until a particle size D.sub.50 of particles of the reaction mixture in the reaction vessel reaches a target particle size: step 3: removing all the reaction mixture in the reaction vessel obtained in step 2, carrying out solid-liquid separation, washing with deionized water, and drying to obtain a nickel-cobalt-manganese hydroxide precursor; step 4: mixing the nickel-cobalt-manganese hydroxide precursor with LiOH.Math.H.sub.2O or lithium carbonate evenly to obtain a mixture; and step 5: sintering the mixture obtained in step 4 under an oxygen atmosphere to obtain the high-voltage low-cobalt ternary cathode material.

6. The method for preparing the high-voltage low-cobalt ternary cathode material of claim 5, wherein in step 2, a dropwise addition speed of the salt solution is controlled to be in a range from 300 mL/h to 500 mL/h; a dropwise addition speed of the concentrated ammonia water is controlled to be in a range from 6 mL/h to 10 mL/h; and a dropwise addition speed of the sodium hydroxide solution is controlled such that the pH of the overall reaction solution is in a range from 10.00 to 13.00.

7. The method for preparing the high-voltage low-cobalt ternary cathode material of claim 5, wherein the base solution containing ammonia water used in step 2 is a base solution containing 0.1-0.8 M ammonia water, preferably a base solution containing 0.3-0.5 M ammonia water; the concentrated ammonia water used in step 2 is an ammonia water solution with a concentration of 20%-28%, preferably an ammonia water solution with a concentration of 25%; and the sodium hydroxide solution used in step 2 is a sodium hydroxide solution with a concentration of 30%-42%, preferably a sodium hydroxide solution with a concentration of 32%.

8. The method for preparing the high-voltage low-cobalt ternary cathode material of claim 5, wherein the particle size D.sub.50 of particles of the reaction mixture obtained in step 2 has a target particle size ranging from 3 m to 20 m.

9. The method for preparing the high-voltage low-cobalt ternary cathode material of claim 5, wherein the molar ratio of the nickel-cobalt-manganese hydroxide precursor to LiOH.Math.H.sub.2O or lithium carbonate in step 4 is in a range from 1:1.01 to 1:1.10, preferably in a range from 1:1.02 to 1:1.05.

10. The method for preparing the high-voltage low-cobalt ternary cathode material of claim 5, wherein the sintering in step 5 is carried out at a temperature ranging from 700 C. to 1000 C. for a time period ranging from 10 hours to 14 hours.

11. The method for preparing the high-voltage low-cobalt ternary cathode material of claim 5, wherein a doping treatment is carried out in step 4, and the doping treatment comprises adding one or more of compounds containing the elements Ca, Mg. Zr, Sr, Na, Si, Al, La, W, B, Fe, Cu, K, Ge, Nd, Nb, Mo, Y, or Ce in step 4.

12. The method for preparing the high-voltage low-cobalt ternary cathode material of claim 5, wherein a coating treatment is carried out after step 5, and the coating treatment comprises, after step 5, adding one or more of the compounds containing the elements Ca, Mg. Zr, Sr. Na, Si, Al, La, W, B, Fe, Cu, K, Ge, Nd, Nb, Mo, Y, or Ce and sintering the mixture again.

13. A lithium ion battery, wherein the high-voltage low-cobalt ternary cathode material of claim 1 is used to prepare positive electrode for lithium ion battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, the present application is further illustrated by means of examples, but the present application is not limited by the examples.

[0036] The information of main raw materials is as follows: [0037] Nickel sulfate hexahydrate NiSO.sub.4.Math.6H.sub.2O, 262.85 g/mol, battery grade, Jinchuan Group Co., Ltd.; [0038] Cobalt sulfate heptahydrate CoSO.sub.4.Math.7H.sub.2O, 281.15 g/mol, battery grade, Zhejiang Huayou Cobalt Co., Ltd.; [0039] Manganese sulfate monohydrate MnSO.sub.4.Math.H.sub.2O, 169.016 g/mol, battery grade, Guizhou Dalong Huicheng New Material Co., Ltd.; [0040] Nickel-cobalt-manganese hydroxide precursor Ni.sub.bCo.sub.cMn.sub.d(OH).sub.2, self-made; [0041] Lithium hydroxide monohydrate LiOH.Math.H.sub.2O, 41.96 g/mol, Shandong Ruifu Lithium Industry Co., Ltd.; [0042] Lithium carbonate Li2Co.sub.3, 73.89 g/mol, Shandong Ruifu Lithium Industry Co., Ltd.; [0043] Polyvinylidene fluoride (PVDF), analytically pure, Aladdin Holdings Group Co., Ltd.; [0044] Nitromethylpyrrolidone (NMP), analytically pure, Aladdin Holdings Group Co., Ltd.; [0045] Ammonia water (20%-28%), analytically pure, Aladdin Holdings Group Co., Ltd.; [0046] Sodium hydroxide solution (32%), analytically pure, Aladdin Holdings Group Co., Ltd.

[0047] The information of main test equipments is as follows: [0048] XRD: Malvern Panaco Aeris X-ray diffractometer [0049] Electrochemical testing equipment: button cell testing system of Shenzhen Neware Technology Co., Ltd.; [0050] Sintering equipment: Tube furnace of Hefei Kejing material technology Co., Ltd., model OTF-1500X.

[0051] The lithium-nickel disordering test method is as follows.

[0052] The cathode material powder was back-pressed into tablets, and the XRD measurement of the powder was carried out using a Malvern Panalytical Aeris-type XRD test instrument, with a 2 test angle of 10-80, a step size of 2 of 0.0108, and a test time of 100 s for each step.

[0053] The XRD spectra obtained from the tests were subjected to XRD spectrum refinement using HighScore software, and the refinement steps comprised: [0054] 1. performing Default operation with automatic fitting twice for background correction; [0055] 2. performing CIF card loading and selecting the 96-400-2444 card; [0056] 3. converting the card to phase and performing auto-finishing twice; [0057] 4. entering the manual refinement mode and performing refinement operations on the background parameters, peak variables, preferred orientation, asymmetry types and spectrum variables in turn; [0058] 5. performing atomic temperature factor modification, wherein the factor of Li is set to 0.0527, that of Ni/Co/Mn is set to 0.01232, and that of O is set to 0.031663; [0059] 6. performing the valuation of atomic occupancy according to the elemental content of the example, firstly setting the initial lithium-nickel disordering ratio as 5, i.e., the lithium-nickel disordering ratio is defined as the ratio percentage of lithium content in the nickel layer to the total lithium content is 5%, e.g., for LiNi.sub.0.52Co.sub.0.10Mn.sub.0.38O.sub.2 of Example 1, the amount of Lil ions (the amount of Li ions in its own position) is 0.95, the amount of Li.sub.2 ions (the amount of Li ions in Ni's position) is 0.05 (i.e., lithium-nickel disordering ratio ), the amount of Ni1 ions (the amount of Ni ions in its own position) is 0.47, the amount of Ni2 ions (the amount of Ni ions in Li's position) is 0.05, the amount of Co ions is 0.1, the amount of Mn ions is 0.38, and the amount of O ions is 2; and [0060] 7. modifying the atomic occupancy constraint relationships, taking LiNi.sub.0.52Co.sub.0.10Mn.sub.0.38O.sub.2 of Example 1 as an example, the constraint relationships are set as: Li1+Ni2=1, Li2+Li1=1, Ni1+Li2=0.52, and then checking Li1/Li2/Ni1/Ni2 occupancy ratio and performing manual refinement; [0061] continuously carrying out the refining operation until the Weighted R Profile (Rwp) value and Rexpected (Rp) value are both lower than 10 (the smaller values indicate that the measured and simulated spectra are closer to each other), and the Goodness of Fit (GOF) value is less than 1.5, which is considered to be the completion of the refining, and then the lithium-nickel disordering ratio of the material can be read out in the interface of the software.

[0062] The electrochemical performance test method is as follows.

[0063] The cathode material and lithium plate obtained in the example were used as cathode active material and anode active material respectively to assemble a button cell; the cathode slurry in the positive electrode plate was composed of the cathode active material, acetylene black (conductive agent), and PVDF (binder), and the mass ratio of the three was 80:12:8; the button cell testing system of Shenzhen Neware Technology Co., Ltd. was used for the test, and the charging and discharging voltages were set within the voltage ranges, such as 3.0-4.5 V. The electrochemical performance of the button cell assembled with the cathode material was tested at room temperature, and the mass specific capacity of the cathode material was tested at a current density of 0.02 A/g (0.1 C), and then its 100-cycle cycling performance was tested at a current density of 0.2 A/g (1 C), and the capacity retention rate was calculated.

[0064] The DSC test method is as follows.

[0065] The fully charged battery was disassembled, and the cathode material soaked in electrolyte solution was scraped off from the positive electrode plate, placed in a DSC testing device (TOPEM TMDSC), and heated to 800 C. at a heating rate of 10 C./min. The temperature-exothermic curve was obtained, and the exothermic temperature was recorded according to the peak position.

[0066] The test method of particle size D50 was as follows.

[0067] Material powder was taken and tested using a Malvern Mastersizer 3000 laser particle size analyzer with a wet sample injector to obtain particle size distribution data.

Example 1

[0068] 2.73 kg of NiSO.sub.4.Math.6H.sub.2O, 1.284 kg of MnSO.sub.4.Math.H.sub.2O, and 562 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0069] 9 L of deionized water was added into a 10 L of reaction kettle, and about 200 mL of concentrated ammonia water was added into the water to formulate a base solution containing 0.3 M of ammonia water. A peristaltic pump was used to add the salt solution, a 32% of sodium hydroxide solution and a 25% of ammonia water solution into the reaction kettle dropwise simultaneously, in which the dropwise addition speed of the salt solution was controlled to be 400 mL/h, the dropwise addition speed of ammonia water was controlled to be 8 mL/h, and the dropwise addition speed of sodium hydroxide solution was controlled by an on-line pH meter, so that the pH of the overall reaction solution was 11.50. The reaction kettle was provided with an overflow port, and the overflow was maintained continuously as the solution was dropwise added until the particle size D50 of particles of the reaction mixture in the reaction kettle was 10 m. After that, all the reaction mixture in the reaction kettle was taken out, and solid-liquid separation was carried out using a centrifuge. The obtained materials were washed with deionized water. The washed moist solid materials were transferred to an oven and dried at 120 C. for 10 h to obtain 885 g of Ni.sub.0.52Co.sub.0.10Mn.sub.0.38(OH).sub.2.

[0070] 100 g of Ni.sub.0.52Co0.10Mn.sub.0.38(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 920 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.52Co.sub.0.10Mn0.38O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Example 2

[0071] 3.15 kg of NiSO.sub.4.Math.6H.sub.2O, 1,014 g of MnSO.sub.4.Math.H.sub.2O, and 562 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0072] Using the same method as that in Example 1, 860 g of Ni.sub.0.6Co.sub.0.1Mn.sub.0.3(OH).sub.2 with a particle size of 10 m was synthesized.

[0073] 100 g of Ni.sub.0.6Co.sub.0.1Mn.sub.0.3(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 890 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.6Co.sub.0.1Mn.sub.0.3O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Example 3

[0074] 3.15 kg of NiSO.sub.4.Math.6H.sub.2O and 1,352 g of MnSO.sub.4.Math.H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0075] Using the same method as that in Example 1, 855 g of Ni.sub.0.6Mn.sub.0.4(OH).sub.2 with a particle size of 10 m was synthesized.

[0076] 100 g of Ni.sub.0.6Mn.sub.0.4(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 890 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.6Mn.sub.0.4O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Example 4

[0077] 3.668 kg of NiSO.sub.4.Math.6H.sub.2O, 845 g of MnSO.sub.4.Math.H.sub.2O, and 281 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0078] Using the same method as that in Example 1, 872 g of Ni.sub.0.70Co.sub.0.05Mn.sub.0.25(OH).sub.2 with a particle size of 10 m was synthesized.

[0079] 100 g of Ni.sub.0.70Co.sub.0.05Mn.sub.0.25(OH).sub.2 was mixed evenly with 46.80 g of LiOH.Math.H.sub.2O at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 820 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.70Co.sub.0.05Mn.sub.0.25O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Example 5

[0080] 3.15 kg of NiSO.sub.4.Math.6H.sub.2O, 1,014 g of MnSO.sub.4.Math.H.sub.2O, and 562 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0081] Using the same method as that in Example 1, 860 g of Ni.sub.0.6Co.sub.0.1Mn.sub.0.3(OH).sub.2 with a particle size of 10 m was synthesized.

[0082] 100 g of Ni.sub.0.6Co.sub.0.1Mn.sub.0.3(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer, and then 0.1 g of aluminum oxide and 0.3 g of zirconium oxide were added into the high-speed mixer and mixed evenly to obtain a mixture. Afterwards the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 890 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.6Co.sub.0.1Mn.sub.0.3O.sub.2 doped with trace amounts of aluminum and zirconium. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Example 6

[0083] 3.15 kg of NiSO.sub.4.Math.6H.sub.2O, 1,014 g of MnSO.sub.4H.sub.2O, and 562 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0084] Using the same method as that in Example 1, 860 g of Ni.sub.0.6Co.sub.0.1Mn.sub.0.3(OH).sub.2 with a particle size of 10 m was synthesized.

[0085] 100 g of Ni.sub.0.6Co.sub.0.1Mn.sub.0.3(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 890 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.6Co.sub.0.1Mn.sub.0.3O.sub.2.

[0086] 100 g of the cathode electrode material was mixed with 0.3 g of aluminum oxide in a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 400 C. for 12 hours under a pure oxygen atmosphere to obtain 100 g of cathode material LiNi.sub.0.6Co.sub.0.1Mn.sub.0.3O.sub.2 with aluminum coated on its surface. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Comparative Example 1

[0087] 2.625 kg of NiSO.sub.4.Math.6H.sub.2O, 1.014 kg of MnSO.sub.4.Math.H.sub.2O, and 1.124 kg of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0088] Using the same method as that in Example 1, 880 g of Ni.sub.0.5Co.sub.0.2Mn.sub.0.3(OH).sub.2 with a particle size of 10 m was synthesized.

[0089] 100 g of Ni.sub.0.5Co.sub.0.2Mn.sub.0.3(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 920 C. for 12 hours under a oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Comparative Example 2

[0090] 3.15 kg of NiSO.sub.4.Math.6H.sub.2O, 676 g of MnSO.sub.4.Math.H.sub.2O, and 1,124 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0091] Using the same method as that in Example 1, 866 g of Ni.sub.0.6Co.sub.0.2Mn.sub.0.2(OH).sub.2 with a particle size of 10 m was synthesized.

[0092] 100 g of Ni.sub.0.6Co.sub.0.2Mn.sub.0.2(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 890 C. for 12 hours under a pure oxygen atmosphere to obtain 100 g of the cathode material LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Comparative Example 3

[0093] 3.15 kg of NiSO.sub.4.Math.6H.sub.2O and 1,352 g of MnSO.sub.4.Math.H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0094] Using the same method as that in Example 1, 891 g of Ni.sub.0.6Mn.sub.0.4(OH).sub.2 with a particle size of 10 m was synthesized.

[0095] 100 g of Ni.sub.0.6Mn.sub.0.4(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 940 C. for 12 hours under a pure oxygen atmosphere to obtain 101 g of the cathode material LiNi.sub.0.6Mn.sub.0.4O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Comparative Example 4

[0096] 3.93 kg of NiSO.sub.4.Math.6H.sub.2O, 507 g of MnSO.sub.4.Math.H.sub.2O, and 562 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which was then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0097] Using the same method as that in Example 1, 876 g of Ni.sub.0.75Co.sub.0.1Mn.sub.0.15(OH).sub.2 with a particle size of 10 m was synthesized.

[0098] 100 g of Ni.sub.0.75Co.sub.0.1Mn.sub.0.15(OH).sub.2 was mixed evenly with 46.80 g of LiOH.Math.H.sub.2O at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 820 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.75Co.sub.0.1Mn.sub.0.15O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Comparative Example 5

[0099] 4.2 kg of NiSO.sub.4.Math.6H.sub.2O, 338 g of MnSO.sub.4.Math.H.sub.2O, and 562 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use. Using the same method as that in Example 1, 894 g of Ni.sub.0.8Co.sub.0.1Mn.sub.0.1(OH).sub.2 with a particle size of 10 m was synthesized.

[0100] 100 g of Ni.sub.0.8Co.sub.0.1Mn.sub.0.1(OH).sub.2 was mixed evenly with 46.80 g of LiOH.Math.H.sub.2O at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 800 C. for 12 hours under a pure oxygen atmosphere to obtain 101 g of the cathode material LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Comparative Example 6

[0101] 4.2 kg of NiSO.sub.4.Math.6H.sub.2O, 507 g of MnSO.sub.4.Math.H.sub.2O, and 281 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0102] Using the same method as that in Example 1, 857 g of Ni.sub.0.8Co.sub.0.05Mn.sub.0.15(OH).sub.2 with a particle size of 10 m was synthesized.

[0103] 100 g of Ni.sub.0.8Co.sub.0.05Mn.sub.0.15(OH).sub.2 was mixed evenly with 46.80 g of LiOH.Math.H.sub.2O at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 800 C. for 12 hours under a pure oxygen atmosphere to obtain 101 g of the cathode material LiNi.sub.0.8Co.sub.0.05Mn.sub.0.15O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Comparative Example 7

[0104] 2.1 kg of NiSO.sub.4.Math.6H.sub.2O, 1.521 kg of MnSO.sub.4.Math.H.sub.2O, and 843 g of CoSO.sub.4.Math.7H.sub.2O were weighed and dissolved in 6 L of deionized water to obtain a salt solution, which is then diluted to a constant-volume of 10 L. A 32% of sodium hydroxide solution and a 25% of ammonia water solution were prepared for later use.

[0105] Using the same method as that in Example 1, 823 g of Ni.sub.0.4Co.sub.0.15Mn.sub.0.45(OH).sub.2 with a particle size of 10 m was synthesized.

[0106] 100 g of Ni.sub.0.4Co.sub.0.15Mn.sub.0.45(OH).sub.2 was mixed evenly with 40.9 g of lithium carbonate at a molar ratio of 1:1.03 using a high-speed mixer to obtain a mixture, and the mixture was loaded into a sagger, placed into a tube furnace, and sintered at 800 C. for 12 hours under a pure oxygen atmosphere to obtain 102 g of the cathode material LiNi.sub.0.4Co.sub.0.15Mn.sub.0.45O.sub.2. Afterwards, the electrochemical specific capacity and cycling performance of this cathode material were tested, and the data was shown in Table 1.

Test Example: Electrochemical Performance Test

[0107] Tests were conducted in accordance with the electrochemical performance test method, the lithium-nickel disordering test method and the DSC test method as described above, and the test results were shown in Table 1.

TABLE-US-00001 TABLE 1 1C 1C 100-cycle 100-cycle capacity capacity retention retention rate at an rate at an 0.1C 0.1C operating operating DSC Lithium-nickel capacity capacity voltage voltage exothermic disordering (mAh/g) (mAh/g) range of range of temperature ratio (%) 3-4.3 V 3-4.5 V 3-4.3 V (%) 3-4.5 V (%) ( C.) Example 1 3.79 165 188 99.2 93.3 311 Example 2 3.25 170 195 99.1 92.9 305 Example 3 5.70 161 189 98.8 91.7 312 Example 4 3.89 182 208 97.9 89.9 275 Example 5 3.67 169 191 99.5 93.4 308 Example 6 3.38 171 196 99.5 93.8 319 Comparative 1.64 163 186 94.3 88.6 295 Example 1 Comparative 1.87 168 194 94.8 88.2 292 Example 2 Comparative 8.14 156 175 93.9 85.1 307 Example 3 Comparative 1.97 187 210 93.8 84.3 264 Example 4 Comparative 2.92 193 219 90.8 76.2 223 Example 5 Comparative 5.07 192 216 90.9 79.1 226 Example 6 Comparative 10.33 143 164 87.0 69.4 334 Example 7

[0108] It can be seen from Table 1:

[0109] Comparing Example 1 with Comparative Example 1, as the lithium-nickel disordering ratio of Comparative Example 1 is too low, its capacity retention rate is relatively low, and the DSC exothermic onset temperature is relatively low, indicating that a suitable lithium-nickel disordering ratio can help to maintain the stability of the structure.

[0110] Comparing Example 2 with Comparative Example 2, as the lithium-nickel disordering ratio of Comparative Example 2 is too low, its capacity retention rate is relatively low, and the DSC exothermic onset temperature is relatively low, indicating that a suitable lithium-nickel disordering ratio can help to maintain the stability of the structure.

[0111] Comparing Example 3 with Comparative Example 3, the capacity retention rate of Comparative Example 3 is relatively low and the capacity is too low, as the lithium-nickel disordering ratio of Comparative Example 3 is too high.

[0112] Comparing Example 4 with Comparative Example 4, due to the lithium-nickel disordering ratio of Comparative Example 4 being too low, its capacity retention rate is relatively low and the DSC exothermic onset temperature is relatively low, indicating that a suitable lithium-nickel disordering ratio can help to maintain the stability of the structure.

[0113] The capacity retention rates of both Comparative Example 5 and Comparative Example 6 were relatively low due to too high nickel content and too high capacity, even though the lithium-nickel disordering ratio is within the appropriate range.

[0114] Comparative Example 7 has a too low nickel content and a too high lithium-nickel disordering ratio, thus it has a too low capacity and a low capacity retention rate, despite the exothermic onset temperature being improved.

[0115] In summary, the present application provides a high-voltage low-cobalt ternary cathode material having the general formula Li.sub.aNi.sub.bCo.sub.c.sub.cMn.sub.dO.sub.2, wherein, 0.97a1.1, 0.5b0.76, 0c0.1, 0.24d0.5, b+c+d=1 and c<0.35d, and wherein the cathode material has a lithium-nickel disordering ratio (): 27. The high-voltage low-cobalt ternary cathode material provided by the present application can be used at an operating voltage of greater than or equal to 4.3 V, and can even be used at an operating voltage of up to 4.5 V. While improving the energy density, cracking and pulverization of the cathode material is avoided due to the smaller volume change of the cathode material, which prolongs the service life of the material which is manifested by better capacity retention rate during cycling, and improves the safety performance of the material which is manifested by the higher exothermic temperature in the DSC test. In addition, due to the relatively lower nickel and cobalt contents and relatively higher manganese content of the cathode material, the cost of the cathode material is reduced while the cathode material has more excellent cycling performance and high voltage performance.