Composite positive electrode material precursor and preparation method therefor

Abstract

The present application provides a composite positive electrode material precursor and a preparation method therefor. The composite positive electrode material precursor comprises nickel-cobalt-manganese hydroxide secondary particles; a Na-containing substance is attached to the surfaces of the nickel-cobalt-manganese hydroxide secondary particles and gaps of wafers; doping and coating of Na ions can be achieved without adding a Na additive during sintering of a positive electrode material. The preparation method for the precursor comprises: dehydrating a precursor slurry, sequentially spraying a washing agent and a coating agent, and drying to obtain the precursor. A water washing step is omitted in a washing process, the original Na ions of the washing agent are reserved, and a certain Na source is added, thereby improving the structural stability, the rate capability and the cycle performance of a ternary positive electrode material.

Description

A composite positive electrode material precursor and preparation method thereof Technical Field

[0001] The present invention relates to the field of lithium-ion battery cathode materials, and in particular to a composite cathode material precursor and a preparation method thereof. Background Art

[0002] Since the successful commercialization of lithium-ion batteries in the late 20th century, they have been widely used in various electronic devices due to their lightweight, high energy density, and long cycle life. In recent years, with the deepening of research and the continuous iteration and upgrading of technology, the energy density of lithium-ion batteries has gradually increased. In particular, with their widespread application in the electric vehicle sector in recent years, the demand for lithium-ion batteries has also exploded. At the same time, higher requirements have been placed on the capacity, cycle life, and safety performance of lithium-ion batteries. Mainstream automotive lithium-ion battery positive electrode materials are mainly divided into two categories: ternary materials and lithium iron phosphate materials. Ternary materials, especially high-nickel ternary materials, have higher volumetric energy density and better rate performance, making them the preferred materials for high-end electric vehicles.

[0003] High nickel materials have a high nickel content and a low sintering temperature, and low-valent Ni 2+ There are more ions, and their ionic radius is similar to that of Li + Close, will cause more serious Li + / Ni 2+ Mixed arrangement affects the cycle performance and rate performance of the material. Generally, fine oxygen-enriched sintering and element doping coating are required to improve these problems. As an alkali metal element, Na is often used as a Li doping because its ionic radius is larger than Li. + When it is doped into the Li layer, it can increase the interlayer spacing and play a supporting role, enhancing the structural strength, which is beneficial to improving the cycle performance and rate performance of the positive electrode material.

[0004] Furthermore, during the production of ternary precursors, sodium hydroxide is typically used as a precipitant and desulfurization detergent. Na ions are treated as impurities and removed with large amounts of pure water during the washing process. The national standard GB / T 26300-2020 stipulates that the mass fraction of Na as an impurity element should not exceed 0.03%. Therefore, many manufacturers go to great lengths to remove elements like Na and S, consuming large amounts of washing water.

[0005] Summary of the Invention

[0006] The present disclosure aims to address at least one of the technical problems existing in the above-mentioned prior art. To this end, the present disclosure provides a composite cathode material precursor and a method for preparing the same. The precursor is coated with a Na-containing substance in the interstices between the particles and on the surface of the particles, which can serve as a Na source for Na doping of the cathode material. This eliminates the need for an additional Na source during the sintering of the cathode material and reduces the amount of washing water used during the precursor washing process, thereby simplifying the process, saving water, and reducing costs.

[0007] According to the first aspect of the present disclosure, a composite cathode material precursor is proposed, wherein the composite cathode material precursor comprises nickel-cobalt-manganese hydroxide secondary particles, wherein a Na-containing substance is attached to the surface of the nickel-cobalt-manganese hydroxide secondary particles and the gaps between the wafers, and the chemical formula of the nickel-cobalt-manganese hydroxide is Ni x Co y Mn (1-x-y) (OH)2, where 0 <x<1,0<y<1,x+y<1。

[0008] In some embodiments, the nickel-cobalt-manganese hydroxide secondary particles are formed by agglomeration of primary particles, the primary particles are flaky crystals, and the thickness of the flaky crystals is 50 to 200 nm.

[0009] In some embodiments, the particle size D50 of the nickel-cobalt-manganese hydroxide secondary particles is 3 to 15 μm.

[0010] In some embodiments, the Na-containing substance is at least one of NaOH, Na2CO3, NaCl or Na2C2O4.

[0011] In some embodiments, the sum of the mass fractions of Ni, Co, and Mn elements in the composite cathode material precursor is 60.0% to 64.0%.

[0012] In some embodiments, the mass fraction of the Na element in the composite cathode material precursor is 0.03% to 3.00%.

[0013] According to the second aspect of the present disclosure, a method for preparing a composite cathode material precursor according to the first aspect of the present disclosure is proposed, comprising the following steps:

[0014] S1: preparing nickel salt, cobalt salt and manganese salt into a metal salt solution;

[0015] S2: mixing the metal salt solution obtained in step S1 with an alkali solution and a complexing agent, adjusting the pH, heating, and stirring to obtain a precursor slurry;

[0016] S3: Dehydrating the precursor slurry obtained in step S2 to obtain a dehydrated material, spraying a detergent and a coating agent on the dehydrated material in sequence, and drying the material to obtain a composite positive electrode material precursor.

[0017] In some embodiments, in step S1, the nickel salt, cobalt salt, and manganese salt are prepared into a metal salt solution according to a molar ratio of Ni:Co:Mn=x:y:(1-xy), wherein 0 <x<1,0<y<1,x+y<1。

[0018] In some embodiments, in step S1, the nickel salt is at least one of nickel sulfate, nickel chloride, or nickel nitrate; the cobalt salt is at least one of cobalt sulfate, cobalt chloride, or cobalt nitrate; and the manganese salt is at least one of manganese sulfate, manganese chloride, or manganese nitrate.

[0019] In some embodiments, in step S1, the concentration of the metal salt solution is 1.0 to 2.5 mol / L.

[0020] In some embodiments, in step S2, the alkali solution is a sodium hydroxide solution, and the mass concentration of the sodium hydroxide solution is 20-40%.

[0021] In some embodiments, in step S2, the complexing agent is an ammonia solution, and the mass concentration of the ammonia solution is 10-20%.

[0022] In some embodiments, in step S2, the pH adjustment is to adjust the pH to 9.0-13.0, the temperature increase is to increase the reaction temperature to 30-80° C., and the stirring speed is 100-500 rpm.

[0023] In some embodiments, in step S2, the pH is adjusted by utilizing the flow rate of the alkali solution to adjust the pH and maintain stability.

[0024] In some embodiments, in step S3, the dehydration of the precursor slurry is performed by centrifugal dehydration, wherein the centrifugal dehydration speed is 500-2000 rpm and the time is 5-15 minutes. The precursor slurry has a high water content, and dehydration is beneficial to improving the subsequent washing and coating effects.

[0025] In some embodiments, in step S3, the detergent is a sodium hydroxide solution, and the mass concentration of the sodium hydroxide solution is 1% to 5%.

[0026] In some embodiments, in step S3, the coating agent is an aqueous solution of at least one of NaOH, Na2CO3, NaCl or Na2C2O4, and the mass concentration of the coating agent is 10% to 50%.

[0027] In some embodiments, in step S3, the spraying parameters of the detergent are: centrifuge speed 500-1500 rpm, detergent volume 50-1000 L, and spraying time 5-20 min.

[0028] In some embodiments, in step S3, the spraying parameters of the coating agent are: centrifuge speed 500-1500 rpm, coating agent volume 5-300 L, and spraying time 1-20 min.

[0029] In some embodiments, in step S3, the drying is to dehydrate the dehydrated material again to obtain a wet precursor material, and then dry the wet precursor material to obtain a composite positive electrode material precursor.

[0030] In some embodiments, in step S3, the dehydration is performed again by centrifugal dehydration, wherein the rotation speed of the centrifugal dehydration is 1000-2000 rpm and the time is 5-30 min.

[0031] In some embodiments, in step S3, the moisture content of the precursor wet material is 5% to 30%. The moisture content of the precursor wet material can be controlled according to the centrifugal dehydration time. Too high a moisture content is not conducive to material transportation, and too low a moisture content will result in excessive energy consumption of the centrifuge.

[0032] In some embodiments, in step S3, the drying temperature is 80-150°C.

[0033] In some embodiments, in step S3, the water content of the composite positive electrode material precursor is less than 1.0%.

[0034] According to a third aspect of the present disclosure, a ternary cathode material is proposed, which is prepared by mixing a composite cathode material precursor obtained by the preparation method described in the second aspect of the present disclosure with a lithium salt and then sintering the mixture.

[0035] In some embodiments, the composite cathode material precursor is mixed with a lithium salt in a molar ratio of 1:(1.01-1.1), and then sintered at a temperature of 650-950° C. for 6-16 hours.

[0036] According to a fourth aspect of the present disclosure, a use of the composite cathode material precursor described in the first aspect of the present disclosure in the preparation of a lithium-ion battery is proposed.

[0037] According to a fifth aspect of the present disclosure, a lithium-ion battery is provided, which comprises the ternary cathode material described in the third aspect of the present disclosure.

[0038] According to one embodiment of the present disclosure, there are at least the following beneficial effects:

[0039] (1) In the composite cathode material precursor disclosed herein, a certain amount of Na-containing substances is attached to the gaps and surfaces of the wafers, and Na ion doping and coating can be achieved without adding Na additives during sintering of the cathode material.

[0040] (2) The present disclosure optimizes the washing process by eliminating the water washing step in the precursor washing process, retaining the original Na ions in the detergent and adding a certain Na source, so that Na-containing substances adhere to the precursor surface and the gap between the wafers, thereby obtaining a composite cathode material precursor. This not only saves water for precursor production and reduces production costs, but also achieves Na ion doping, improving the structural stability and rate and cycle performance of the ternary cathode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present disclosure is further described below with reference to the accompanying drawings and embodiments, wherein:

[0042] FIG1 is a SEM image of the surface morphology of the composite cathode material precursor prepared in Example 1 of the present disclosure;

[0043] FIG2 is a SEM image of the composite cathode material precursor particles prepared in Example 1 of the present disclosure;

[0044] FIG3 is an EPMA scan of the surface of the composite cathode material precursor particles prepared in Example 1 of the present disclosure for the Na element;

[0045] FIG4 is a SEM image of the surface morphology of the precursor prepared in Comparative Example 1 of the present disclosure;

[0046] FIG5 is a SEM image of the precursor particles prepared in Comparative Example 1 of the present disclosure;

[0047] FIG6 is an EPMA scanning diagram of the surface of the precursor particles prepared in Comparative Example 1 of the present disclosure for the Na element;

[0048] FIG7 is a graph showing the cycle capacity retention rate of the positive electrode materials prepared in Example 1 and Comparative Example 1 of the present disclosure. DETAILED DESCRIPTION

[0049] The following will clearly and completely describe the concept and technical effects of the present disclosure in conjunction with embodiments to fully understand the purpose, features and effects of the present disclosure.

[0050] Example 1

[0051] A composite cathode material precursor with the molecular formula Ni 0.92 Co 0.06 Mn 0.02 (OH)2, Na content is 0.2%.

[0052] A method for preparing the composite cathode material precursor as described above comprises the following steps:

[0053] S1: nickel sulfate, cobalt sulfate, and manganese sulfate are prepared in a ratio of 0.92:0.06:0.02 to prepare a metal solution with a concentration of 2.0 mol / L.

[0054] S2: The prepared metal solution is introduced into a 500L reactor. At the same time, alkali solution (32% sodium hydroxide solution) and ammonia solution (20% ammonia solution) are also introduced into the reactor. The flow rates of the metal solution, ammonia solution, and alkali solution are controlled at 30L / h, 1.5L / h, and 15L / h. The reactor is maintained at a constant temperature of 60°C and a speed of 250 rpm. The pH in the reactor is controlled at approximately 10.50 by the flow rate of alkali solution. Under the above conditions, the materials in the reactor are uniformly mixed, a precipitation reaction occurs, and a precursor slurry is obtained.

[0055] S3: The precursor slurry is pumped into a centrifuge for dehydration and centrifugation at a centrifugal speed of 1200 rpm and a centrifugal time of 10 min to obtain a dehydrated material; a 3% mass concentration NaOH solution is used as a detergent, and the dehydrated material is evenly sprayed and washed through a spray device in the centrifuge at a centrifuge speed of 800 rpm, a detergent volume of 100 L, and a spraying time of 5 min to wash away impurities such as S; a 20% mass concentration NaOH solution is used as a coating agent, and a coating spray is performed after the washing spray is completed, the centrifuge speed continues to be maintained at 800 rpm, the coating agent volume is 30 L, and the spraying time is 2 min; after coating spraying, the material is further centrifuged and dehydrated at a centrifugal speed of 1200 rpm and a centrifugal time of 10 min to obtain a precursor wet material with a moisture content of 15%; the centrifuged precursor wet material is placed in an oven and dried at 120°C for 10 h to obtain a finished composite positive electrode material precursor.

[0056] The SEM test results of the finished composite positive electrode material precursor are shown in Figures 1 and 2. It can be seen from the figures that the main body of the precursor is a secondary spherical particle formed by the agglomeration and accumulation of many primary crystals. The particle diameter is about 11 μm, and there are many crystals attached to the surface of the particle. The EPMA scan of the surface Na element in Figure 3 shows that the Na content on the surface is relatively high, proving that the attached crystals are Na-containing coatings.

[0057] A ternary positive electrode material is prepared by the following steps:

[0058] Lithium hydroxide and the composite cathode material precursor prepared by the above preparation method were mixed in a molar ratio of 1.05:1, the mixture was placed in a muffle furnace, and sintered at 850°C for 10 hours in an oxygen atmosphere. The sintered material was crushed and sieved to obtain a ternary cathode material.

[0059] Example 2

[0060] A composite cathode material precursor with the molecular formula Ni 0.90 Co 0.08 Mn 0.02 (OH)2, Na content is 0.6%.

[0061] A method for preparing the composite cathode material precursor as described above comprises the following steps:

[0062] S1: nickel sulfate, cobalt sulfate, and manganese sulfate are prepared in a ratio of 0.90:0.08:0.02 to prepare a metal solution with a concentration of 2.0 mol / L.

[0063] S2: The prepared metal solution is introduced into a 500L reactor. At the same time, alkali solution (32% sodium hydroxide solution) and ammonia solution (20% ammonia solution) are also introduced into the reactor. The flow rates of the metal solution, ammonia solution, and alkali solution are controlled at 25L / h, 1.3L / h, and 12L / h. The reactor is maintained at a constant temperature of 65°C and a speed of 200rpm. The pH in the reactor is controlled at approximately 10.60 by adjusting the alkali solution flow rate. Under the above conditions, the materials in the reactor are uniformly mixed, a precipitation reaction occurs, and a precursor slurry is obtained.

[0064] S3: The precursor slurry is pumped into a centrifuge for dehydration and centrifugation at a centrifugal speed of 1200 rpm and a centrifugal time of 10 min to obtain a dehydrated material; a 3% mass concentration NaOH solution is used as a detergent, and the dehydrated material is evenly sprayed and washed through a spray device in the centrifuge at a centrifuge speed of 800 rpm, a detergent volume of 100 L, and a spraying time of 5 min to wash away impurities such as S; a 20% mass concentration NaOH solution is used as a coating agent, and a coating spray is performed after the washing spray is completed, the centrifuge speed continues to be maintained at 800 rpm, the coating agent volume is 30 L, and the spraying time is 2 min; after coating spraying, the material is further centrifuged and dehydrated at a centrifugal speed of 1200 rpm and a centrifugal time of 8 min to obtain a precursor wet material with a moisture content of 20%; the centrifuged precursor wet material is placed in an oven and dried at 120°C for 10 h to obtain a finished composite positive electrode material precursor.

[0065] A ternary positive electrode material is prepared by the following steps:

[0066] Lithium hydroxide and the composite cathode material precursor prepared by the above preparation method were mixed in a molar ratio of 1.06:1, the mixture was placed in a muffle furnace, and sintered at 880°C in an oxygen atmosphere for 10 hours. The sintered material was crushed and sieved to obtain a ternary cathode material.

[0067] Example 3

[0068] A composite cathode material precursor with the molecular formula Ni 0.82 Co 0.12 Mn 0.06 (OH)2, Na content is 0.8%.

[0069] A method for preparing the composite cathode material precursor as described above comprises the following steps:

[0070] S1: nickel sulfate, cobalt sulfate, and manganese sulfate are prepared in a ratio of 0.82:0.12:0.06 to prepare a metal solution with a concentration of 2.0 mol / L.

[0071] S2: The prepared metal solution is introduced into a 1000L reactor. At the same time, alkali solution (32% sodium hydroxide solution) and ammonia solution (20% ammonia solution) are also introduced into the reactor. The flow rates of the metal solution, ammonia solution, and alkali solution are controlled at 50L / h, 3L / h, and 20L / h. The reactor is maintained at a constant temperature of 70°C and a speed of 150 rpm. The pH in the reactor is controlled at approximately 10.80 by the flow rate of alkali solution. Under the above conditions, the materials in the reactor are uniformly mixed, a precipitation reaction occurs, and a precursor slurry is obtained.

[0072] S3: The precursor slurry is pumped into a centrifuge for dehydration and centrifugation at a centrifugal speed of 1200 rpm and a centrifugal time of 10 min to obtain a dehydrated material; a 3% mass concentration NaOH solution is used as a detergent, and the dehydrated material is evenly sprayed and washed through a spray device in the centrifuge at a centrifuge speed of 1000 rpm, a detergent volume of 100 L, and a spraying time of 5 min to wash away impurities such as S; a 20% mass concentration NaOH solution is used as a coating agent, and a coating spray is performed after the washing spray is completed, the centrifuge speed is adjusted to 800 rpm, the coating agent volume is 30 L, and the spraying time is 3 min; after coating spraying, the material is further centrifuged and dehydrated at a centrifugal speed of 1200 rpm and a centrifugal time of 10 min to obtain a precursor wet material with a moisture content of 15%; the centrifuged precursor wet material is placed in an oven and dried at 120°C for 10 h to obtain a finished composite positive electrode material precursor.

[0073] A ternary positive electrode material is prepared by the following steps:

[0074] Lithium hydroxide and the composite cathode material precursor prepared by the above preparation method were mixed in a molar ratio of 1.04:1, the mixture was placed in a muffle furnace, and sintered at 850°C for 10 hours in an oxygen atmosphere. The sintered material was crushed and sieved to obtain a ternary cathode material.

[0075] Comparative Example 1

[0076] A cathode material precursor with the molecular formula Ni 0.92 Co 0.06 Mn 0.02 (OH)2, no Na complex.

[0077] A method for preparing the positive electrode material precursor as described above comprises the following steps:

[0078] S1: nickel sulfate, cobalt sulfate, and manganese sulfate are prepared in a ratio of 0.92:0.06:0.02 to prepare a metal solution with a concentration of 2.0 mol / L.

[0079] S2: The prepared metal solution is introduced into a 500L reactor. At the same time, alkali solution (32% sodium hydroxide solution) and ammonia solution (20% ammonia solution) are also introduced into the reactor. The flow rates of the metal solution, ammonia solution, and alkali solution are controlled at 30L / h, 1.5L / h, and 15L / h. The reactor is maintained at a constant temperature of 60°C and a speed of 250 rpm. The pH in the reactor is controlled at approximately 10.50 by the flow rate of alkali solution. Under the above conditions, the materials in the reactor are uniformly mixed, a precipitation reaction occurs, and a precursor slurry is obtained.

[0080] S3: The precursor slurry is poured into a centrifuge for dehydration and centrifugation at a centrifuge speed of 1200 rpm and a centrifugation time of 10 min to obtain a dehydrated material; a 3% mass concentration of NaOH solution is used as a detergent, and the dehydrated material is evenly sprayed and washed through the spray device in the centrifuge at a centrifuge speed of 800 rpm, a detergent volume of 100 L, and a spraying time of 5 min to wash away impurities such as S; deionized water is then sprayed for further washing at a centrifuge speed of 800 rpm, a deionized water volume of 300 L, and a spraying time of 10 min to wash away Na residues; after washing, the material is further centrifuged and dehydrated at a centrifuge speed of 1500 rpm and a centrifugation time of 15 min to obtain a precursor wet material; the centrifuged precursor wet material is placed in an oven and dried at 120°C for 10 h to obtain a finished positive electrode material precursor.

[0081] The SEM test results of the finished precursor are shown in Figures 4 and 5. As can be seen from these figures, the precursor consists primarily of secondary, spherical particles formed by the agglomeration of numerous primary grains. The particle diameter is approximately 11 μm, and the particle surface is clean, free of other substances. An EPMA scan of the surface Na element in Figure 6 reveals that the surface Na content is extremely low, almost undetectable.

[0082] A ternary positive electrode material is prepared by the following steps:

[0083] Lithium hydroxide was mixed with the cathode material precursor obtained by the above preparation method in a molar ratio of 1.05:1. The mixture was placed in a muffle furnace and sintered at 850°C for 10 hours in an oxygen atmosphere. The sintered material was crushed and sieved to obtain a ternary cathode material.

[0084] Comparative Example 2

[0085] A cathode material precursor with the molecular formula Ni 0.90 Co 0.08 Mn 0.02 (OH)2, no Na complex.

[0086] A method for preparing the positive electrode material precursor as described above comprises the following steps:

[0087] S1: nickel sulfate, cobalt sulfate, and manganese sulfate are prepared in a ratio of 0.90:0.08:0.02 to prepare a metal solution with a concentration of 2.0 mol / L.

[0088] S2: The prepared metal solution is introduced into a 500L reactor. At the same time, alkali solution (32% sodium hydroxide solution) and ammonia solution (20% ammonia solution) are also introduced into the reactor. The flow rates of the metal solution, ammonia solution, and alkali solution are controlled at 25L / h, 1.3L / h, and 12L / h. The reactor is maintained at a constant temperature of 65°C and a speed of 200rpm. The pH in the reactor is controlled at approximately 10.60 by adjusting the alkali solution flow rate. Under the above conditions, the materials in the reactor are uniformly mixed, a precipitation reaction occurs, and a precursor slurry is obtained.

[0089] S3: The precursor slurry is poured into a centrifuge for dehydration and centrifugation at a centrifuge speed of 1200 rpm and a centrifugation time of 10 min to obtain a dehydrated material; a 3% mass concentration of NaOH solution is used as a detergent, and the dehydrated material is evenly sprayed and washed through the spray device in the centrifuge at a centrifuge speed of 800 rpm, a detergent volume of 100 L, and a spraying time of 5 min to wash away impurities such as S; deionized water is then sprayed for further washing at a centrifuge speed of 800 rpm, a deionized water volume of 300 L, and a spraying time of 10 min to wash away Na residues; after washing, the material is further centrifuged and dehydrated at a centrifuge speed of 1500 rpm and a centrifugation time of 15 min to obtain a precursor wet material; the centrifuged precursor wet material is placed in an oven and dried at 120°C for 10 h to obtain a finished positive electrode material precursor.

[0090] A ternary positive electrode material is prepared by the following steps:

[0091] Lithium hydroxide was mixed with the cathode material precursor obtained by the above preparation method in a molar ratio of 1.06:1. The mixture was placed in a muffle furnace and sintered at 880°C for 10 hours in an oxygen atmosphere. The sintered material was crushed and sieved to obtain a ternary cathode material.

[0092] Comparative Example 3

[0093] A cathode material precursor with the molecular formula Ni 0.82 Co 0.12 Mn0.06 (OH)2, no Na complex.

[0094] A method for preparing the positive electrode material precursor as described above comprises the following steps:

[0095] S1: nickel sulfate, cobalt sulfate, and manganese sulfate are prepared in a ratio of 0.82:0.12:0.06 to prepare a metal solution with a concentration of 2.0 mol / L.

[0096] S2: The prepared metal solution is introduced into a 1000L reactor. At the same time, alkali solution (32% sodium hydroxide solution) and ammonia solution (20% ammonia solution) are also introduced into the reactor. The flow rates of the metal solution, ammonia solution, and alkali solution are controlled at 50L / h, 3L / h, and 20L / h. The reactor is maintained at a constant temperature of 70°C and a speed of 150 rpm. The pH in the reactor is controlled at approximately 10.80 by the flow rate of alkali solution. Under the above conditions, the materials in the reactor are uniformly mixed, a precipitation reaction occurs, and a precursor slurry is obtained.

[0097] S3: The precursor slurry is poured into a centrifuge for dehydration and centrifugation at a centrifuge speed of 1200 rpm and a centrifugation time of 10 min to obtain a dehydrated material; a 3% mass concentration of NaOH solution is used as a detergent, and the dehydrated material is evenly sprayed and washed through the spray device in the centrifuge at a centrifuge speed of 800 rpm, a detergent volume of 100 L, and a spraying time of 5 min to wash away impurities such as S; deionized water is then sprayed for further washing at a centrifuge speed of 800 rpm, a deionized water volume of 300 L, and a spraying time of 10 min to wash away Na residues; after washing, the material is further centrifuged and dehydrated at a centrifuge speed of 1500 rpm and a centrifugation time of 15 min to obtain a precursor wet material; the centrifuged precursor wet material is placed in an oven and dried at 120°C for 10 h to obtain a finished positive electrode material precursor.

[0098] A ternary positive electrode material is prepared by the following steps:

[0099] Lithium hydroxide was mixed with the cathode material precursor obtained by the above preparation method in a molar ratio of 1.04:1. The mixture was placed in a muffle furnace and sintered at 850°C for 10 hours in an oxygen atmosphere. The sintered material was crushed and sieved to obtain a ternary cathode material.

[0100] Test example

[0101] 1. The water consumption in the washing step of Examples 1-3 and Comparative Examples 1-3 was statistically analyzed. The statistical results are shown in the following table:

[0102] Table 1. Washing water consumption of Examples and Comparative Examples

[0103] It can be seen from the above water consumption statistics that when the embodiment and the comparative example wash the same amount of precursor, the average water consumption of the embodiment in the washing stage is 130L, and the average water consumption of the embodiment is 400L. Compared with the comparative example, the embodiment saves 67.5% of water, effectively reducing the precursor production cost.

[0104] 2. The electrochemical performance of the ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 was tested according to the following methods:

[0105] The ternary cathode material was used as the active material, acetylene black as the conductive agent, and PVDF as the binder. The active material, conductive agent, and binder were weighed in a 90:5:5 ratio. A certain amount of the organic solvent NMP was added, stirred, and coated onto aluminum foil to form a positive electrode sheet. A metallic lithium sheet was used as the negative electrode. CR2430 button cells were manufactured in an argon-filled glove box. Electrical performance testing was performed using a CT2001A blue-electric test system. Test conditions: voltage range 3.0-4.3V, current density 1C = 190mAh / g, and test temperature 25±1°C.

[0106] The test results are shown in Table 1:

[0107] Table 2. Electrochemical performance test table

[0108] It can be seen from the above-mentioned charge-discharge performance test that the discharge capacity of the embodiment and the comparative example positive electrode materials at a low rate of 0.1C is comparable, but at a high rate, especially a rate of 2C, the embodiment positive electrode material prepared by the Na-doped and coated composite precursor exhibits a higher capacity, and the rate is better than that of the comparative example positive electrode material.

[0109] Coin-type batteries made from the positive electrode materials obtained in Example 1 and Comparative Example 1 were subjected to cycling performance testing. Charge and discharge tests were performed at a rate of 0.5C within the range of 3.0 to 4.25 V. After 100 cycles, the test results are shown in Figure 7 . The capacity retention rate of Example 1 was 94.8%, while that of Comparative Example 1 was 88.3%. As can be seen from the figure, the capacity retention rate of the positive electrode material of Example 1 was superior to that of Comparative Example 1 over the 100-cycle test.

[0110] The above tests show that the composite positive electrode material precursor containing Na element doping and coating prepared by this scheme has more advantages than conventional precursors in the rate performance and cycle performance of the final battery.

Claims

1. A composite cathode material precursor, characterized in that: The composite positive electrode material precursor comprises secondary particles of nickel-cobalt-manganese hydroxide, the surface of the secondary particles of nickel-cobalt-manganese hydroxide and the gaps of the wafer are attached with a substance containing Na, and the chemical formula of the nickel-cobalt-manganese hydroxide is Ni x Co y Mn (1-x-y) (OH)2, where 0 <x<1,0<y<1,x+y<1。 2. The composite cathode material precursor according to claim 1, characterized in that: The Na-containing substance is at least one of NaOH, Na2CO3, NaCl or Na2C2O4.

3. The composite cathode material precursor according to claim 1, characterized in that: The sum of the mass fractions of Ni, Co and Mn elements in the composite positive electrode material precursor is 60.0% to 64.0%.

4. The composite cathode material precursor according to claim 1, characterized in that: The mass fraction of the Na element in the composite positive electrode material precursor is 0.03% to 3.00%.

5. The method for preparing a composite cathode material precursor according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: preparing a metal salt solution by preparing nickel salt, cobalt salt and manganese salt; S2: mixing the metal salt solution obtained in step S1 with an alkali solution and a complexing agent, adjusting the pH, heating, and stirring to obtain a precursor slurry; S3: dehydrating the precursor slurry obtained in step S2 to obtain a dehydrated material, spraying a detergent and a coating agent on the dehydrated material in sequence, and drying the dehydrated material to obtain a composite positive electrode material precursor.

6. The preparation method according to claim 5, characterized in that: In step S1, the nickel salt, cobalt salt and manganese salt are prepared into a metal salt solution according to the molar ratio of Ni:Co:Mn=x:y:(1-xy), wherein 0 <x<1,0<y<1,x+y<1。 7. The preparation method according to claim 5, characterized in that: In step S1, the nickel salt is at least one of nickel sulfate, nickel chloride or nickel nitrate; the cobalt salt is at least one of cobalt sulfate, cobalt chloride or cobalt nitrate; and the manganese salt is at least one of manganese sulfate, manganese chloride or manganese nitrate.

8. The preparation method according to claim 5, characterized in that: In step S1, the concentration of the metal salt solution is 1.0-2.5 mol / L.

9. The preparation method according to claim 5, characterized in that: In step S2, the pH is adjusted to 9.0-13.0, the temperature is increased to 30-80°C, and the stirring speed is 100-500 rpm.

10. The preparation method according to claim 5, characterized in that: In step S3, the detergent is a sodium hydroxide solution, and the mass concentration of the sodium hydroxide solution is 1% to 5%.

11. The preparation method according to claim 5, characterized in that: In step S3, the coating agent is an aqueous solution of at least one of NaOH, Na2CO3, NaCl or Na2C2O4, and the mass concentration of the coating agent is 10% to 50%.

12. The preparation method according to claim 5, characterized in that: In step S3, the moisture content of the precursor wet material is 5% to 30%.

13. A ternary positive electrode material, characterized in that: The composite positive electrode material precursor according to any one of claims 1 to 4 or the composite positive electrode material precursor prepared by the preparation method according to any one of claims 5 to 12 is mixed with a lithium salt and then sintered.

14. The ternary cathode material according to claim 13, characterized in that: The composite positive electrode material precursor is mixed with a lithium salt in a molar ratio of 1:(1.01-1.10), and then sintered at a temperature of 650-950° C. for 6-16 hours.

15. A lithium ion battery, characterized in that: Contains the ternary positive electrode material as claimed in claim 13 or 14.

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